基本情報

所属

• 理学研究院　化学部門　有機・生命化学分野

職名

• 教授

ホームページURL

http://barato.sci.hokudai.ac.jp/~org1/

科研費研究者番号

• 70202132

ORCID ID

•  https://orcid.org/0000-0002-1230-2044

J-Global ID

• 200901041847970754

研究キーワード

• 超分子   応答性分子   酸化還元系   エレクトロクロミズム   分子素子   酸化還元   安定ラジカル   色素   有機電導体   水素結合   分子不斉   両性多段階酸化還元   光誘起電子移動   動的酸化還元   単一成分有機電導体   レドックス系   開殻型分子   円二色性   C-H--O水素結合   渡環相互作用   シクロファン   応答性   電気化学   ホトクロミズム   単一分子メモリ   固相反応   共有結合   ホストゲスト   物性有機化学   有機電子材料   構造有機化学   Organic Materials Chemistry   Organic Reaction Chemistry   Structural Organic Chemistry   

研究分野

• ナノテク・材料 / 構造有機化学、物理有機化学
• ナノテク・材料 / 機能物性化学
• ナノテク・材料 / 有機合成化学
• ものづくり技術（機械・電気電子・化学工学） / 電子デバイス、電子機器

担当教育組織

•  学士課程　理学部
•  修士課程　総合化学院
•  博士課程　総合化学院

職歴

• 2006年04月 - 現在 北海道大学大学院 理学研究院 化学部門 教授 (改組）
• 2002年04月 - 2006年03月 北海道大学大学院理学研究科化学専攻 教授
• 1995年01月 - 2002年03月 北海道大学理学部化学第二学科 助教授
• 1989年04月 - 1994年12月 東北大学 理学部 化学科 助手
• 1988年04月 - 1989年03月 JSPS PD (東北大学理学部化学科）

学歴

• 1986年04月 - 1988年04月   東北大学大学院理学研究科化学専攻博士後期課程(短縮修了）
• 1984年04月 - 1986年03月   東北大学   理学研究科   化学専攻博士課程前期
• 1980年04月 - 1984年03月   東北大学   理学部   化学第二学科

所属学協会

• 基礎有機化学会   日本化学会   有機合成化学協会   

研究活動情報

論文

• Smart Lipid Nanoparticle that Remodels Tumor Microenvironment for Activatable H2S Gas and Photodynamic Immunotherapy

  Luyan Wu, Yili Liu, Wenhui Zeng, Yusuke Ishigaki, Sensen Zhou, Xingxing Wang, Yidan Sun, Yan Zhang, Xiqun Jiang, Takanori Suzuki, Deju Ye

  Journal of the American Chemical Society 2023年12月07日
• On-Surface Synthesis of Multiple Cu Atom-Bridged Organometallic Oligomers

  Kewei Sun, Kazuma Sugawara, Andrey Lyalin, Yusuke Ishigaki, Kohei Uosaki, Oscar Custance, Tetsuya Taketsugu, Takanori Suzuki, Shigeki Kawai

  ACS Nano 2023年12月04日
• Domino‐Redox Reaction Induced by An Electrochemically Triggered Conformational Change

  Takashi Harimoto, Tomoki Tadokoro, Soichiro Sugiyama, Takanori Suzuki, Yusuke Ishigaki

  Angewandte Chemie International Edition 2023年11月28日 

  Abstract The concept of a domino‐type reaction has been applied in a wide range of fields such as synthetic organic chemistry, material engineering, and life science. To extend the domino concept to redox chemistry, we designed and synthesized a dimeric quinodimethane (QD) with a nonplanar dithiin spacer. The domino‐redox properties can be activated by raising the temperature, based on a thermally equilibrated twisted conformation of QD, which has a higher HOMO level that is more readily oxidized. After one QD unit is oxidized (trigger), steric repulsion and electronic interaction between electrophores make the neighboring QD unit adopt a twisted conformation (domino process), which facilitates the following oxidation. Thus, a domino‐redox reaction was achieved for the first time by a change in the HOMO level due to a drastic change in the molecular conformation.
• Carbon-based Biradicals: Structural and Magnetic Switching

  Yusuke Ishigaki, Takashi Harimoto, Takuya Shimajiri, Takanori Suzuki

  Chemical Reviews 2023年11月10日
• Double Dynamic Structural Change Enabling Tricolor Chromism by the Realization of Apparent Two-Electron Transfer to Skip the Open-Shell State

  Takashi Harimoto, Yuka Sugai, Kazuma Sugawara, Takanori Suzuki, Yusuke Ishigaki

  CHEMISTRY-A EUROPEAN JOURNAL 2023年07月 

  Most redox systems generally cannot avoid the involvement of open-shell species upon generating multiply charged species, which often reduces reversibility in multi-color electrochromic systems. In this study, we newly synthesized octakis(aminophenyl)-substituted pentacenebisquinodimethane (BQD) derivatives and their hybrids with alkoxyphenyl analogues. Thanks to apparent two-electron transfer accompanied by double dramatic changes in the structure of the arylated quinodimethane skeleton, the dicationic and tetracationic states were generated and isolated quantitatively because of the negligible steady-state concentration of intermediary open-shell species such as monocation or trication radicals. When two electrophores with different donating abilities are attached to the BQD skeleton, a dicationic state with a different color can be isolated in addition to the neutral and tetracationic states. For these tetracations, an interchromophore interaction induces a red-shift of the NIR absorptions, thus realizing tricolor UV/Vis/NIR electrochromic behavior involving only closed-shell states.
• Chalcogen-Peierls Transition: Single-Crystal-to-Single-Crystal Transition from a Two-Dimensional to a One-Dimensional Network of Chalcogen Bonds at Low Temperature

  Soki Kawaguchi, Takuya Shimajiri, Tomoyuki Akutagawa, Takanori Fukushima, Yusuke Ishigaki, Takanori Suzuki

  BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 96 7 631 - 635 2023年07月 

  Due to inherent structural instability, low-dimensional mate-rials often undergo the Peierls transition upon cooling, which suppressed by an increase in dimensionality of their solid-state electronic structures using secondary bonding interactions such as chalcogen bonds (ChB). We revealed here that ChB them-selves have an inherent structural instability when a chalcogen atom participates in simultaneous formation of two ChB, dem-onstrating for the first time a Peierls-like transition (chalcogen-Peierls transition) of ChB-based organic solids upon cooling. Thus, a lattice dimerization occurs at 220-230 K that changes the two-dimensional ChB network into an accumulated one-dimensional ribbon network in the tetracyanoquinodimethane fused with two [1,2,5]thiadiazoles (1). Negative cooperativity of two ChB formation is weakened on the Se atom due to greater polarizability. Thus, the selenadiazole analogues (2 and 3) undergo a similar chalcogen-Peierls transition at lower tem- peratures, such as at 160-170 K and at 110-120 K, respectively, depending on the number of Se atom incorporated (one or two, respectively).
• One-Pot Synthesis of Helical Azaheptalene and Chiroptical Switching of an Isolable Radical Cation

  Yuta Nishimura, Takashi Harimoto, Takanori Suzuki, Yusuke Ishigaki

  CHEMISTRY-A EUROPEAN JOURNAL 2023年07月 

  A nitrogen-centered heptalene, azaheptalene, was designed as a representative of a new class of redox-responsive molecules with a large steric strain that originates from the adjacent seven-membered rings. The pentabenzo derivative of azaheptalene was efficiently synthesized by a palladium-catalyzed one-pot reaction of commercially available reagents. Bromination led to mono- and dibrominated derivatives, the latter of which is interconvertible with isolable radical cation species exhibiting near-infrared absorption. Since the azaheptalene skeleton shows configurationally stable helicity with a large torsion angle, enantiomers could be successfully separated. Thus, optically pure azaheptalenes with P- or M-helicity showed strong chiroptical properties (|g(abs)|& GE;0.01), which could be changed by an electric potential.
• Crystal Engineering, Electron Conduction, and Molecular Recognition and Reactivity by Chalcogen Bonds in Tetracyanoquinodimethanes Fused with [1,2,5]Chalcogenadiazoles

  Takuya Shimajiri, Henri-Pierre Jacquot de Rouville, Valérie Heitz, Tomoyuki Akutagawa, Takanori Fukushima, Yusuke Ishigaki, Takanori Suzuki

  Synlett 2023年04月12日 

  Studies on a series of tetracyanoquinodimethanes (TCNQs) fused with [1,2,5]chalcogenadiazole rings reveals that chalcogen bonds (ChBs), through E center dot center dot center dot=C (E = S or Se) contacts, are a decisive factor in determining their crystal structures, with the formation of one- or twodimensional networks in a lateral direction. For anion-radical salts generated by one-electron reduction, electron conduction occurs in the direction of the network due to intermolecular electronic interactions involving ChBs. Based on the reliable synthon E center dot center dot center dot N=C for crystal engineering, molecular recognition occurs so that solid-state molecular complexes are selectively formed with certain donors, such as xylenes, among their isomers by charge-transfer-type clathrate formation. The inclusion cavity of the clathrate might provide a reaction environment for photoinduced electron transfer in the solid state. The accommodation of multiple conformers of overcrowded ethylene exhibiting thermo/mechanochromism is another example of a novel function that can be realized by ChBs through E center dot center dot center dot N=C contacts. Therefore, these chalcogenadiazolo-TCNQs endowed with the ability to form ChBs are promising materials for the development of novel solid-state functions. 1 Introduction 2 Bis[1,2,5]thiadiazolo-TCNQ (BTDA) 2.1 Chalcogen Bonds in Crystal Structures of BTDA and its Se Analogues 2.2 Electronic Effects of Chalcogen Bonds in Organic Conductors Consisting of BTDA 2.3 Molecular Recognition by Chalcogen Bonds in Molecular Complexes of BTDA 2.4 Single-Crystalline-State Photoreactions of Molecular Complexes of BTDA 2.5 Overcrowded Ethylene Composed of a BTDA Substructure 3 TCNQ Analogues Fused with a [1,2,5]Chalcogenadiazole 3.1 Crystal Structures of Chalcogenadiazolo-TCNQs 3.2 Crystal Structures of Chalcogenadiazolo-TCNNQs: An E center dot center dot center dot N=C Chalcogen Bond versus a Weak C-H center dot center dot center dot N=C Hydrogen Bond 3.3 Molecular Recognition by Chalcogen Bonds in TCNNQ Derivatives 4 Outlook
• Tripodal Triazatruxene Derivative as a Face-On Oriented Hole-Collecting Monolayer for Efficient and Stable Inverted Perovskite Solar Cells

  Minh Anh Truong, Tsukasa Funasaki, Lucas Ueberricke, Wataru Nojo, Richard Murdey, Takumi Yamada, Shuaifeng Hu, Aruto Akatsuka, Naomu Sekiguchi, Shota Hira, Lingling Xie, Tomoya Nakamura, Nobutaka Shioya, Daisuke Kan, Yuta Tsuji, Satoshi Iikubo, Hiroyuki Yoshida, Yuichi Shimakawa, Takeshi Hasegawa, Yoshihiko Kanemitsu, Takanori Suzuki, Atsushi Wakamiya

  Journal of the American Chemical Society 145 13 7528 - 7539 2023年03月22日 

  Hole-collecting monolayers have drawn attention in perovskite solar cell research due to their ease of processing, high performance, and good durability. Since molecules in the hole-collecting monolayer are typically composed of functionalized pi-conjugated structures, hole extraction is expected to be more efficient when the pi-cores are oriented face-on with respect to the adjacent surfaces. However, strategies for reliably controlling the molecular orientation in monolayers remain elusive. In this work, multiple phosphonic acid anchoring groups were used to control the molecular orientation of a series of triazatruxene derivatives chemisorbed on a transparent conducting oxide electrode surface. Using infrared reflection absorption spectroscopy and metastable atom electron spectroscopy, we found that multipodal derivatives align face-on to the electrode surface, while the monopodal counterpart adopts a more tilted configuration. The face-on orientation was found to facilitate hole extraction, leading to inverted perovskite solar cells with enhanced stability and high-power conversion efficiencies up to 23.0%.
• Enhancement of NIR‐Absorbing Ability of Bis(diarylmethylium)‐Type Dicationic Dyes Based on an Ortho ‐Substitution Strategy.

  Takashi Harimoto, Takanori Suzuki, Yusuke Ishigaki

  Chemistry – A European Journal 29 23 2023年03月16日 

  Electrochromic systems capable of switching near-infrared (NIR) absorption are fascinating from the viewpoint of applications in the materials and life sciences. Although 11,11,12,12-tetraaryl-9,10-anthraquinodimethanes (AQDs) with a folded form undergo one-stage two-electron oxidation to produce twisted dicationic dyes exhibiting NIR absorption, there is a need to establish a design strategy that can enhance the NIR-absorbing abilities of the corresponding dicationic dyes. In this study, we designed and synthesized a series of AQD derivatives with various substituents introduced at the ortho-position(s) of the 4-methoxyphenyl group. X-ray and spectroscopic analyses revealed that NIR-absorbing properties can be changed by introduction of the ortho-substituents. Thus, control of the steric and electronic effects of the ortho-substituents on the 4-methoxyphenyl groups was demonstrated to be an effective strategy for fine-tuning of the HOMO and LUMO levels for neutral AQDs and twisted dications, respectively, resulting in the modification of electrochemical and spectroscopic properties under an "ortho-substitution strategy".
• Bis(triarylmethylium)‐type Macrocyclic Dications: Mechanochromic Emission Extending to the Red Region

  Yusuke Ishigaki, Takuya Tachibana, Kazuma Sugawara, Moto Kikuchi, Takanori Suzuki

  ChemPlusChem 88 3 2023年03月 

  Macrocyclic dications 2(2+) composed of two triarylmethylium units were designed and synthesized. In contrast to the reference monocations 1(+), macrocyclic dications 2(2+) exhibited mechanochromic emission extending to the red region (-900 nm), since the luminescence color in a solid state can reversibly change due to their constrained structures granted by alkylene linkers and the choice of a proper counterion. X-ray diffraction and spectroscopic analyses revealed that such mechanochromic behavior was induced by the crystal-to-amorphous transition. A change in the intermolecular interaction of macrocyclic dications 2(2+) would be the key to realizing a change in the emission pattern, since the color of the molecules did not change by applying mechanical stimuli. These findings may suggest a design strategy for creating a variety of stimuli-responsive materials, especially for carbocation-based fluorescent materials.
• Dibenzotropylium-Capped Orthogonal Geometry Enabling Isolation and Examination of a Series of Hydrocarbons with Multiple 14π-Aromatic Units

  Yuki Hayashi, Shuichi Suzuki, Takanori Suzuki, Yusuke Ishigaki

  Journal of the American Chemical Society 145 4 2596 - 2608 2023年02月01日 

  A series of six dications composed of pure hydrocarbons with one to six non-substituted 9,10-anthrylene units end-capped with two dibenzotropyliums were designed and synthesized to elucidate the electronic properties of huge oligo(9,10-anthrylene) backbones. Their structures were successfully determined by X-ray analyses even in the case of eight planar 14π-electron units, revealing that all dications adopt almost orthogonally twisted structures between neighboring units. Spectroscopic and voltammetric analyses show that neither the significant overlap of orbitals nor the delocalization of electrons between 14π-electron units occurs due to the orthogonally twisted geometry even in solution. As a result, sequential oxidation processes were observed with the reversible formation of multivalent cations with the release of the same number of electrons as the number of anthrylene units. Upon two-electron reduction, a closed-shell butterfly-shaped form was obtained from the dication containing one anthrylene unit, whereas open-shell twisted biradicals were isolated as stable entities in the cases of derivatives containing three to six anthrylene units. Notably, from the derivative with two anthrylene units, a metastable open-shell isomer was obtained quantitatively and underwent slow thermal conversion to the most stable closed-shell isomer (Ea = 23.1 kcal mol-1). There is a drastic change in oxidation potentials between two neutral species (ΔE = 1.32 V in CH2Cl2). Since the present dications were regenerated upon oxidation of the isolated reduction products, these systems may contribute to the development of advanced response systems capable of switching color, magnetic properties, and oxidative properties by using a “cation-capped orthogonal geometry”.
• Single-Molecule Observation of Redox Reactions Enabled by Rigid and Isolated Tripodal Molecules

  Yuzu Kobayashi, Yasuyuki Yokota, Raymond A. Wong, Misun Hong, Jun Takeya, Saho Osawa, Fumitaka Ishiwari, Yoshiaki Shoji, Takashi Harimoto, Keisuke Sugimoto, Yusuke Ishigaki, Takanori Suzuki, Takanori Fukushima, Yousoo Kim

  Journal of Physical Chemistry C 127 1 746 - 758 2023年01月12日 

  Tracking various chemical reactions, including electrochemical and photochemical reactions at the single-molecule level, is expected to yield a great deal of knowledge from both fundamental and applied aspects. In this study, we report on a methodology to track the electronic-state changes of redox reactions at the single-molecule level by using electrochemical scanning tunneling microscopy (EC-STM). EC-STM is powerful for single-molecule analysis of redox reactions, but previous studies have shown difficulties separating the structural and electronic contributions due to orientational changes during the redox reaction. Here, we visualize the electronic-state changes of a single ferrocene associated with redox reactions using EC-STM by synthesizing and fabricating a monolayer of structurally rigid tripodal molecules based on triptycene, which act as ideal anchors to preserve a constant distance between the electrode and the ferrocene moieties. This methodology paves the way for versatile single-molecule measurements of important phenomena at the solid-liquid interface, such as photochemistry and heterogeneous catalysis.
• Exceptionally flexible quinodimethanes with multiple conformations: polymorph-dependent colour tone and emission of crystals

  Kazuma Sugawara, Toshikazu Ono, Yoshio Yano, Takanori Suzuki, Yusuke Ishigaki

  Materials Chemistry Frontiers 7 8 1591 - 1598 2023年 

  Tetraazaanthraquinodimethanes can exhibit various colours and emissions depending on their multiple conformations, such as not only folded and twisted forms but also intermediate structures, e.g., planar and twisted-folded forms, in pseudopolymorphs.
• Strain‐sensitive On‐Surface Ladderization via Non‐Dehydrogenative Heterocyclization

  Yujing Ma, Kazuma Sugawara, Yusuke Ishigaki, Kewei Sun, Takanori Suzuki, Shigeki Kawai

  Chemistry – A European Journal 2022年12月20日 

  On-surface cyclodehydrogenation recently became an important reaction to planarize pi-conjugated molecules and oligomers. However, the high-activation barrier to cleave the C-H bond often requires high-temperature annealing, consequently restricting structures of precursor molecules and/or leading to random fusion at their edges. Here, we present a synthesis of pyrrolopyrrole-bridged ladder oligomers from 11,11,12,12-tetrabromo-1,4,5,8-tetraaza-9,10-anthraquinodimethane molecules on Ag(111) with bond-resolved scanning tunnelling microscopy. This non-dehydrogenative cyclization between pyrazine and ethynylene/cumulene groups has a low-activation barrier for forming intermediary dimeric oligomer containing dipyrazinopyrrolopyrrolopyrazine units, thus giving new insight into the strain-sensitive in ladder-oligomer formation.
• Ultralong C(sp3)–C(sp3) Single Bonds Shortened and Stabilized by London Dispersion

  Takuya Shimajiri, Yusuke Ishigaki, Yuta Kawakami, Soki Kawaguchi, Yuki Hayashi, Kazuto Hada, Takanori Suzuki

  Synlett 34 10 1147 - 1152 2022年10月11日 

  A carbon-carbon (C-C) single bond longer than 1.7 Å shows unique bond flexibility, even though a C-C single bond is typically rigid and robust. We report here that the bond length of a flexible C-C single bond surrounded by bulky alkyl groups on novel hexaphenylethane-type hydrocarbons could be affected by even weak non-covalent interactions such as London dispersion. Thanks to London dispersion, an ultralong and flexible C-C single bond exhibits an obvious bond contraction. X-ray analyses and Raman spectroscopy provide direct information regarding the bond length and strength, and density functional theory calculations explain the bond contraction driven by London dispersion. An extremely elongated C-C bond with flexibility would be a good probe for quantifying even weak interaction, which is usually difficult to detect, as a change in bond length.
• Geometrical and Electronic Structure of Cation Radical Species of Tetraarylanthraquinodimethane: An Intermediate for Unique Electrochromic Behavior

  Yusuke Ishigaki, Reina Fukagawa, Kazuma Sugawara, Takashi Harimoto, Takanori Suzuki

  Chemistry – An Asian Journal 17 22 e202200914  2022年09月30日 

  Two tetraarylanthraquinodimethane (Ar4 AQD) derivatives having two different aryl groups (aminophenyl and methoxyphenyl) were prepared by sequential dibromomethylation and Suzuki-coupling reactions. X-ray analyses showed that they adopt a folded structure in the neutral state whereas the corresponding dications have a planar anthracene ring, to which diarylmethylium units are perpendicularly attached. Different from Ar4 AQD having the same substituents that undergoes facile two-electron transfer during interconversion with the dicationic state, the intermediary cation radical becomes long-lived in the newly prepared unsymmetric derivatives. The geometric and electronic structures of the open-shell intermediates were elucidated through electrochemical and theoretical investigation, with revealing that the cation radicals adopt the twisted geometry like dications. Upon electrolyses of the dications, the twisted cation radicals were involved in the electrochromism whereas their steady-state concentration is negligible in the oxidation process, thus realizing unique tricolor electrochromic behavior with a hysteretic pattern of color change (colorless -> purple -> blue -> colorless).
• Near-Infrared Electrochromic Behavior of Dibenzothiepin Derivatives Attached by Two Michler's Hydrol Blue Units.

  Yusuke Ishigaki, Masaki Takata, Takuya Shimajiri, Luyan Wu, Wenhui Zeng, Deju Ye, Takanori Suzuki

  Chemistry (Weinheim an der Bergstrasse, Germany) 28 70 2022年09月15日 

  10,11-Bis[bis(4-dimethylaminophenyl)methylene]dibenzo[ bf ]thiepin ( 1 ) and -oxepin ( 2 ) were prepared as stable yellow crystalline compounds, which are the cyclic analogues of electron-donating hexaarylbutadienes. Upon two-electron oxidation, they are reversibly transformed into the title dications ( 1 2+ and 2 2+ ) exhibiting near-infrared (NIR) absorptions, which were also isolated as stable salts. These redox pairs can serve as new entries into less well-explored organic NIR-electrochromic systems, and the separation of redox peaks (electrochemical bistability) was attained for 1 / 1 2+ and 2 / 2 2+ , thanks to drastic geometrical changes between neutral and dicationic states, as revealed by a series of X-ray analyses. Thiepin- S,S -dioxide analogue ( 3 / 3 2+ ) exhibits quite similar redox behavior due to nonaromatic nature of the dibenzothiepin or -oxepin unit in 1 2+ and 2 2+ , whereas thiepin- S -oxide derivative ( 4 / 4 2+ ) does not exhibit bistability due to the less change in geometry upon electron transfer, showing that a subtle change of a bridging atom in the central seven-membered ring can modify the redox properties.
• A Ratiometric Photoacoustic Probe with a Reversible Response to Hydrogen Sulfide and Hydroxyl Radicals for Dynamic Imaging of Liver Inflammation

  Luyan Wu, Wenhui Zeng, Yusuke Ishigaki, Junya Zhang, He Bai, Takashi Harimoto, Takanori Suzuki, Deju Ye

  Angewandte Chemie International Edition 61 37 e202209248  2022年08月08日 

  Reversible imaging probes that allow for the dynamic visualization of the redox cycle between hydroxyl radical ((OH)-O-center dot) and hydrogen sulfide (H2S) are vital to probe the redox imbalance-involved pathological process in vivo. Herein, we report a reversible ratiometric photoacoustic (PA) imaging nanoprobe (1-PAIN) for the real-time imaging of (OH)-O-center dot/H2S redox cycle in vivo. 1-PAIN displays a low PA ratio between 690 and 825 nm (PA(690)/PA(825)), which significantly increases by approximate to 5-fold upon oxidation by (OH)-O-center dot, and is switched back to the initially low PA(690)/PA(825) value upon reduction by H2S. 1-PAIN could dynamically report on the hepatic (OH)-O-center dot production in mice during the lipopolysaccharide (LPS)-induced liver inflammation process, and visualize hepatic H2S generation during the N-acetyl cysteine (NAC)-induced anti-inflammation process. 1-PAIN can act as a useful tool to probe the redox state in living biology, beneficial for the study of redox imbalance-related diseases.
• Solid‐State Assembly by Chelating Chalcogen Bonding in Quinodimethane Tetraesters Fused with a Chalcogenadiazole

  Yusuke Ishigaki, Kota Asai, Henri‐Pierre Jacquot de Rouville, Takuya Shimajiri, Johnny Hu, Valérie Heitz, Takanori Suzuki

  ChemPlusChem 87 4 e202200075  2022年04月 

  In contrast to p-quinodimethane tetraesters, which undergo facile polymerization due to their diradical character, newly synthesized 1 and 2 consisting of a chalcogenadiazole fused to a p-naphthoquinodimethane tetraester are thermodynamically stable due to butterfly-shaped deformation. Such a folded molecular structure is also favorable for chalcogen bond (ChB) formation through intermolecular close contacts between a chalcogen atom (E: Se or S) and the oxygen atoms of ester groups in a crystal. The less-explored chelating-ChB through a C=O⋅⋅⋅E⋅⋅⋅O=C contact [Se⋅⋅⋅O: 2.94–3.37 Å] is the key supramolecular synthon for the formation of a one-dimensional rod-like assembly in a crystal, which is commonly observed in selenadiazole-tetraesters (1) with OMe, OEt, and OiPr groups. The formation of inclusion cavities between the rods shows that 1 could serve as solid-state host molecules for clathrate formation, as found in a hexane-solvated crystal. In contrast, thiadiazole-tetraesters (2) are less suitable for the formation of a rod-like assembly since the ChB involving S is less effective, and thus is overwhelmed by weak hydrogen bonds through C−H⋅⋅⋅O contacts.
• An Activatable Afterglow/MRI Bimodal Nanoprobe with Fast Response to H2S for In Vivo Imaging of Acute Hepatitis

  Wenhui Zeng, Luyan Wu, Yusuke Ishigaki, Takashi Harimoto, Yuxuan Hu, Yidan Sun, Yuqi Wang, Takanori Suzuki, Hong Yuan Chen, Deju Ye

  Angewandte Chemie - International Edition 61 4 e202111759  2022年01月21日 

  Accurate detection of hepatic hydrogen sulfide (H2S) to monitor H2S-related enzymes’ activity is critical for acute hepatitis diagnosis, but remains a challenge due to the dynamic and transient nature of H2S. Here, we report a H2S-activatable near-infrared afterglow/MRI bimodal probe F1-GdNP, which shows an “always-on” MRI signal and “off-on” afterglow signal toward H2S. F1-GdNP shows fast response, high sensitivity and specificity toward H2S, permitting afterglow imaging of H2S and evaluation of cystathionine γ-lyase (CSE)’s activity in living mice. We further employ the high spatial-resolution MRI signal of F1-GdNP to track its delivery and accumulation in liver. Importantly, F1-GdNP offers a high signal-to-background ratio (SBR=86.2±12.0) to sensitively report on the increased hepatic H2S level in the acute hepatitis mice via afterglow imaging, which correlated well with the upregulated CSE activity in the liver, showcasing the good potential of F1-GdNP for monitoring of acute hepatitis process in vivo.
• Multiple Molecular Interactions between Alkyl Groups and Dissociated Bromine Atoms on Ag(111)

  Shigeki Kawai, Kazuma Sugawara, Yujing Ma, Kewei Sun, Oscar Custance, Yusuke Ishigaki, Takanori Suzuki

  Physical Chemistry Chemical Physics 24 36 22191 - 22197 2022年 

  Multiple intermolecular interactions offer a high-degree of controllability of on-surface molecular assemblies. Here, two kinds of molecular networks were formed by depositing 11,11,12,12-tetrabromo-1,4,5,8-tetraaza-9,10-anthraquinodimethane derivatives with two different alkyl groups in...
• Anthraquinodimethane Ring-Flip in Sterically Congested Alkenes: Isolation of Isomer and Elucidation of Intermediate through Experimental and Theoretical Approach

  Yusuke Ishigaki, Tomoki Tadokoro, Yu Harabuchi, Yuki Hayashi, Satoshi Maeda, Takanori Suzuki

  Bulletin of the Chemical Society of Japan 95 1 38 - 46 2022年 

  From the viewpoint of the development of molecular response systems, stimulus-induced switching of multiconformational/multi-configurational overcrowded ethylenes are interesting, whose properties could be manipulated by understanding the detailed isomerization paths. Anthraquinodimethane (AQD) ring-flip is usually a very fast process, and thus less studied experimentally. Herein, we studied AQDs with dibenzo- and tribenzocycloheptatrienylidene units, which have large enough steric hindrance to retard the AQD ring-flip to allow determination of the ¦Gºvalue experimentally. Their thermal isomerization was also scrutinized using the artificial force induced reaction method to elucidate the intermediates. Based on the structural unsymmetry in a newly prepared AQD, one of the isomers that undergoes a reversible conformational change via AQD ring-flip was isolated and analyzed by X-ray for the first time.
• Chalcogen Bond versus Halogen Bond: Changing Contributions in Determining the Crystal Packing of Dihalobenzochalcogenadiazoles

  Yusuke Ishigaki, Kai Shimomura, Kota Asai, Takuya Shimajiri, Tomoyuki Akutagawa, Takanori Fukushima, Takanori Suzuki

  Bulletin of the Chemical Society of Japan 95 3 522 - 531 2022年 

  In the crystals of 4,7-dihalobenzo[c][1,2,5]chalcogenadiazoles, the molecules are connected by two competing secondary bonding interactions: chalcogen bond (ChB) and halogen bond (HaB). Because the strengths of ChB and HaB change according to the kind of chalcogen (E: S, Se, Te) and halogen (X: Cl, Br, I), their relative contributions in determining the crystal packing can also change. Six newly determined crystal structures as well as 3 previously reported structures can be categorized into two groups: ChB-dominant and HaB-dominant structures. HaB in which X = I is strong enough to dictate the crystal packing of compounds with E = S and Se, but not where E = Te, whereas HaB in which X = Cl or Br has little effect on ChB-dominant molecular networks in crystals. The observed changing contributions of ChB and HaB may be useful for designing new supramolecular synthons for crystal engineering.
• Generation of hydroxyl radical-activatable ratiometric near-infrared bimodal probes for early monitoring of tumor response to therapy

  Luyan Wu, Yusuke Ishigaki, Wenhui Zeng, Takashi Harimoto, Baoli Yin, Yinghan Chen, Shiyi Liao, Yongchun Liu, Yidan Sun, Xiaobo Zhang, Ying Liu, Yong Liang, Pengfei Sun, Takanori Suzuki, Guosheng Song, Quli Fan, Deju Ye

  Nature Communications 12 1 2021年12月 [査読有り]
   

  Tumor response to radiotherapy or ferroptosis is closely related to hydroxyl radical (•OH) production. Noninvasive imaging of •OH fluctuation in tumors can allow early monitoring of response to therapy, but is challenging. Here, we report the optimization of a diene electrochromic material (1-Br-Et) as a •OH-responsive chromophore, and use it to develop a near-infrared ratiometric fluorescent and photoacoustic (FL/PA) bimodal probe for in vivo imaging of •OH. The probe displays a large FL ratio between 780 and 1113 nm (FL₇₈₀/FL₁₁₁₃), but a small PA ratio between 755 and 905 nm (PA₇₅₅/PA₉₀₅). Oxidation of 1-Br-Et by •OH decreases the FL₇₈₀/FL₁₁₁₃ while concurrently increasing the PA₇₅₅/PA₉₀₅, allowing the reliable monitoring of •OH production in tumors undergoing erastin-induced ferroptosis or radiotherapy.
• Obituary for Professor Toshio Mukai

  Hiroshi Ikeda, Takashi Hirano, Kan Wakamatsu, Takanori Suzuki, Eietsu Hasegawa

  JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY C-PHOTOCHEMISTRY REVIEWS 48 2021年09月
• Heterocyclic Ring‐Opening of Nanographene on Au(111)

  Kewei Sun, Kazuma Sugawara, Andrey Lyalin, Yusuke Ishigaki, Kohei Uosaki, Tetsuya Taketsugu, Takanori Suzuki, Shigeki Kawai

  Angewandte Chemie 133 17 9513 - 9518 2021年04月19日
• Heterocyclic Ring-Opening of Nanographene on Au(111)

  Sun, K., Sugawara, K., Lyalin, A., Ishigaki, Y., Uosaki, K., Taketsugu, T., Suzuki, T., Kawai, S.

  Angewandte Chemie - International Edition 60 17 9427 - 9432 2021年04月19日 

  Cyclo-dehydrogenation is of importance to induce the planarization of molecules on noble surfaces upon annealing. In contrast to a number of successful syntheses of polycyclic aromatic hydrocarbons by forming carbon–carbon bonds, it is still rare to conduct conjugation and cleavage of carbon–nitrogen bonds in molecules. Here, we present a systematic transformation of the C−N bonds in11,11,12,12-tetraphenyl-1,4,5,8-tetraazaanthraquinodimethane as well as three other derivatives on Au(111). With bond-resolved scanning tunneling microscopy, we discovered novel the “heterocyclic segregation” reaction of one pyrazine ring with two nitrogen atoms to form two quinoline rings with one nitrogen each. Density functional theory calculations showed that the intramolecular ring-forming and -opening of N-heterocycles are strongly affected by the initial hydrogen–substrate interaction.
• Chalcogen Bond versus Weak Hydrogen Bond: Changing Contributions in Determining the Crystal Packing of [1,2,5]-Chalcogenadiazole-Fused Tetracyanonaphthoquinodimethanes

  Yusuke Ishigaki, Kota Asai, Takuya Shimajiri, Tomoyuki Akutagawa, Takanori Fukushima, Takanori Suzuki

  Organic Materials 03 02 090 - 096 2021年04月 

  The crystal structures of a series of tetracyanonaphthoquinodimethanes fused with a selenadiazole or thiadiazole ring revealed that their molecular packing is determined mainly by two intermolecular interactions: chalcogen bond (ChB) and weak hydrogen bond (WHB). ChB between Se and a cyano group dictates the packing of selenadiazole derivatives, whereas the S-based ChB is much weaker and competes with WHB in thiadiazole analogues. This difference can be explained by different electrostatic potentials as revealed by density functional theory calculations. A proper molecular design that weakens WHB can change the contribution of ChB in determining the crystal packing of thiadiazole derivatives.
• Hysteretic Three-State Redox Interconversion among Zigzag Bisquinodimethanes with Non-fused Benzene Rings and Twisted Tetra-/Dications with [5]/[3]Acenes Exhibiting Near-Infrared Absorptions

  Yusuke Ishigaki, Takashi Harimoto, Kazuma Sugawara, Takanori Suzuki

  Journal of the American Chemical Society 143 9 3306 - 3311 2021年03月10日 

  Octaaryl-substituted bisquinodimethanes (BQDs) with a zigzag structure were designed as redox-switchable molecules that undergo four-electron oxidation to produce tetracationic pentacenes with a doubly twisted structure. In contrast to one-stage four-electron oxidation of BQDs, stepwise two-electron reduction of tetracationic pentacenes occurs to give dicationic anthracenes and then the original BQDs, step-by-step. Since both tetracations and dications exhibit near-infrared (NIR) absorptions (-1400 nm) based on an intramolecular charge-transfer interaction, changes in not only their structures but also their UV-vis-NIR spectra can be controlled by redox stimuli. In this Communication, we present an unprecedented one-step π-extension to pentacene from non-fused benzene rings by oxidation, and subsequent two-stage deannulation to benzene rings via anthracene upon reduction. All structures were determined by single-crystal X-ray analyses, and their properties were characterized by spectroscopic and theoretical studies.
• Molecular Recognition by Chalcogen Bond: Selective Charge-Transfer Crystal Formation of Dimethylnaphthalene with Selenadiazolotetracyanonaphthoquinodimethane

  Ishigaki, Y., Asai, K., de Rouville, H.-P.J., Shimajiri, T., Heitz, V., Fujii-Shinomiya, H., Suzuki, T.

  European Journal of Organic Chemistry 2021 6 990 - 997 2021年02月12日 

  The title nonplanar electron acceptor (1) fused with a selenadiazole ring selectively forms a crystalline charge-transfer complex (CT crystal) with 2,6-dimethylnaphthalene (2,6-DMN). On the other hand, the sulfur analogue (2) has less recognition ability and forms CT crystals with both 2,6- and 2,7-DMN. X-ray analyses of 1, 2, and their CT crystals revealed that the Se⋅⋅⋅N chalcogen bond (ChB) in 1 is strong enough to determine the crystal packing with the formation of a cavity suitable for 2,6-DMN. On the contrary, ChB through S⋅⋅⋅N contact in 2 competes with other weak interactions such as a C−H⋅⋅⋅N hydrogen bond. The stronger ChB involving Se is the key for 1 to separate 2,6-DMN (>97 wt %) from a complex isomer mixture containing ca. 10 wt % each of 2,6- and 2,7-DMN by a simple, efficient and straightforward mixing-filtration-heating process.
• 9,9'-bi(xanthene)-type hexaphenylethane derivatives as advanced organic electrochromic systems

  Suzuki, T., Ishigaki, Y., Takata, M., Nishida, J.-I., Fukushima, T.

  Heterocycles 102 3 419 - 450 2021年 

  9-Phenylxanthenyl radical can undergo facile C-C bond formation at C9-position when the two units of the radical are connected at C2'-positions to give stable intramolecular dimer (1), which is a clamped hexaphenylethane derivative with an elongated C-C bond. The newly formed bond in 1 can be cleaved easily upon two-electron oxidation to give bis(9-xanthenylium)-type dication (22+), from which the diradical is generated upon two-electron reduction. This review account describes the dynamic redox ("dyrex") pair of colorless 1 and yellow-orange 22+, which provides a versatile scaffold to develop multi-functional electrochromic systems. Both of 1 and 22+ are sterically challenged molecules and thus adopt characteristic skewed geometries. Electrochiroptical response was realized by suppressing the chiral inversion of helicity in 1 and axial chirality in 22+ whereas redox-induced fluorescence switching was attained by attaching the fluorophore whose emission is quenched by xanthenylium in 22+ but not by spiro(xanthene) unit in 1. By the molecular design that allows intramolecular chiral transmission, the spectral changes were also induced by the external stimuli (e.g. heat, pH) other than redox input, which made it possible to construct less well-explored multi-input-multi-output response systems. More advanced functions could be endowed, such as chiral redox memory or reversible O2-storage, by further modification of the prototype.
• Expandability of the covalent bond: A new facet discovered in extremely long Csp3-Csp3 single bonds

  Ishigaki, Y., Uchimura, Y., Shimajiri, T., Suzuki, T.

  Bulletin of the Chemical Society of Japan 94 4 1385 - 1393 2021年 

  Molecules with an extreme structural parameter, such as an elongated C-C bond, have attracted much attention due to their special properties, which ordinary molecules do not have. Stabilized hexaphenylethanes are suitable compounds for seeking for the longest C-C bond. In addition to steric repulsion among the aryl groups (“front strain”) found in 1,1,2,2-tetra-arylacenaphthenes (1), “scissor effects” cause expansion of the C1-C2 bond in 1,1,2,2-tetraarylpyracenes (2). A series of crystallographic analyses of 2 revealed that the substituent on the aryl group also affects the C1-C2 bond length. The “front strain” over the weakened bond is enhanced by the ring-fused structure in di(spiroacridan)pyracene (2A). The bond length of 1.771(3) ¡ determined by X-ray analysis at 93 K is one of the largest values for a Csp3-Csp3 bond, and increases to 1.791(3) ¡ when the single crystal is heated to 413 K. Further expansion over 1.80 ¡ was achieved by maximizing the front strain by fixing the spirodibenzocycloheptatriene units in an eclipsed manner in the core-shell-type dihydropyracylene (3B) [1.795(2) ¡ at 100 K, 1.806(2) ¡ at 400 K]. Several studies show that “bond expandability” is a newly discovered feature of an elongated covalent bond, which could be used for the future design of novel materials with a mechanical/thermal response.
• Redox-active tetraaryldibenzoquinodimethanes

  Ishigaki, Y., Sugawara, K., Tadokoro, T., Hayashi, Y., Harimoto, T., Suzuki, T.

  Chemical Communications 57 59 7201 - 7214 2021年 

  In this Feature Article, we focus on our research history for constructing functional response systems based on redox-active quinodimethanes with electron-donating aryl groups, which undergo reversible interconversion with twisted cations.

• 1,2,5]Chalcogenadiazole-fused Dicyanonaphthoquinodiimines: Larger Contribution from Chalcogen Bond than Weak Hydrogen Bond in Determining Crystal Structures#

  Ishigaki, Y., Asai, K., Shimajiri, T., Suzuki, T.

  Chemistry Letters 50 6 1184 - 1187 2021年 

  The title electron acceptors are planar molecules undergoing reversible two-stage one-electron reduction processes. In the crystal of selenadiazole derivative (1), tetrameric structure is formed by two kinds of chalcogen bond (ChB), which is further connected by ChB and weak hydrogen bond (WHB). Although sulfur analogue (2) has only weaker ChB, it crystallizes isomorphously to 1 forming ChB-Tetramer, thus contribution from ChB is more dominant than WHB in determining the crystal packing, which is different from the corresponding tetracyanoquinodimethane analogues.
• 5-arylidenetetronate as a versatile electrophore for pi-extended electron acceptors

  Hayashi, Y., Ishigaki, Y., Merad, J., Suzuki, T., Médebielle, M.

  Heterocycles 103 1 165 - 171 2021年 

  Bis[4-methoxy-5-methylenefuran-2(5H)-one]-type electron acceptors with anthracene-9,10-diyl and thiophene-2,5-diyl spacer were prepared by one-pot condensation of methyl tetronate with the corresponding dialdehydes. They undergo reversible electrochemical reduction, thus showing the potential utility of 5-arylidenetetronate as an electrophore for developing novel electron acceptors.
• Flexible C−C Bonds: Reversible Expansion, Contraction, Formation, and Scission of Extremely Elongated Single Bonds

  Shimajiri, T., Suzuki, T., Ishigaki, Y.

  Angewandte Chemie - International Edition 59 49 22252 - 22257 2020年12月30日 

  Since carbon-carbon (C-C) covalent bonds are rigid and robust, the bond length is, in general, nearly constant and depends only on the bond order and hybrid orbitals. We report herein direct visualization of the reversible expansion and contraction of a C(sp(3))-C(sp(3)) single bond by light and heat. This flexibility of a C-C bond was demonstrated by X-ray analysis and Raman spectroscopy of hexaphenylethane (HPE)-type hydrocarbons with two spiro-dibenzocycloheptatriene units, the intramolecular [2+2] photocyclization of which and thermal cleavage of the resulting cyclobutane ring both occur in a single-crystalline phase. The force constant of the contracted C-C bond is 1.6 times greater than that of the expanded bond. Since formation of the cyclobutane ring and contraction of the C-C bond lower the HOMO level by approximately 1 eV, the oxidative properties of these HPEs with a flexible C-C bond can be deactivated/activated by light/heat.
• Flexible C−C Bonds: Reversible Expansion, Contraction, Formation, and Scission of Extremely Elongated Single Bonds

  Takuya Shimajiri, Takanori Suzuki, Yusuke Ishigaki

  Angewandte Chemie 132 49 22436 - 22441 2020年12月30日
• H2S-activatable near-infrared afterglow luminescent probes for sensitive molecular imaging in vivo

  Luyan Wu, Yusuke Ishigaki, Yuxuan Hu, Keisuke Sugimoto, Wenhui Zeng, Takashi Harimoto, Yidan Sun, Jian He, Takanori Suzuki, Xiqun Jiang, Hong-Yuan Chen, Deju Ye

  Nature Communications 11 1 2020年12月 [査読有り]
   

  Afterglow luminescent probes with high signal-to-background ratio show promise for in vivo imaging; however, such probes that can be selectively delivered into target sites and switch on afterglow luminescence remain limited. We optimize an organic electrochromic material and integrate it into near-infrared (NIR) photosensitizer (silicon 2,3-naphthalocyanine bis(trihexylsilyloxide) and (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]) containing nanoparticles, developing an H₂S-activatable NIR afterglow probe (F1²⁺-ANP). F1²⁺-ANP displays a fast reaction rate (1563 ± 141 M⁻¹ s⁻¹) and large afterglow turn-on ratio (~122-fold) toward H₂S, enabling high-sensitivity and -specificity measurement of H₂S concentration in bloods from healthy persons, hepatic or colorectal cancer patients. We further construct a hepatic-tumor-targeting and H₂S-activatable afterglow probe (F1²⁺-ANP-Gal) for noninvasive, real-time imaging of tiny subcutaneous HepG2 tumors (<3 mm in diameter) and orthotopic liver tumors in mice. Strikingly, F1²⁺-ANP-Gal accurately delineates tumor margins in excised hepatic cancer specimens, which may facilitate intraoperative guidance of hepatic cancer surgery.
• Switching of Redox Properties Triggered by a Thermal Equilibrium between Closed‐Shell Folded and Open‐Shell Twisted Species

  Yusuke Ishigaki, Takumi Hashimoto, Kazuma Sugawara, Shuichi Suzuki, Takanori Suzuki

  Angewandte Chemie 132 16 6643 - 6646 2020年04月16日
• Switching of Redox Properties Triggered by a Thermal Equilibrium between Closed-Shell Folded and Open-Shell Twisted Species

  Ishigaki, Y., Hashimoto, T., Sugawara, K., Suzuki, S., Suzuki, T.

  Angewandte Chemie - International Edition 59 16 6581 - 6584 2020年04月16日 [査読有り][通常論文]
   

  Thermally switchable redox properties have been reported to be due to a change in the spin state of newly designed overcrowded ethylenes, which can adopt closed-shell folded and open-shell twisted forms. In this study, tetrathienylanthraquinodimethane derivatives were designed to be in thermal equilibrium between a more stable folded form and less stable but more donating twisted diradical in solution, so that the oxidation potential can be controlled by heating/cooling. This is the first example of a switching of redox properties based on a thermally equilibrated twisted diradical, which can be more readily oxidized to the twisted dication.
• Hexaarylbutadiene: A Versatile Scaffold with Tunable Redox Properties towards Organic Near‐Infrared Electrochromic Material

  Yusuke Ishigaki, Takashi Harimoto, Keisuke Sugimoto, Luyan Wu, Wenhui Zeng, Deju Ye, Takanori Suzuki

  Chemistry – An Asian Journal 15 7 1147 - 1155 2020年04月 

  When the 1,1,4,4-tetraanilinobutadiene skeleton is attached with two halogenated aryl units at the 2,3-positions, they undergo facile two-electron oxidation to give stable dicationic dyes which exhibit a near-infrared (NIR) absorption whereas the neutral dienes show only pale color. Therefore, a distinct electrochromic response with an absorption change in the NIR region is achieved, which is attracting considerable recent attention from the viewpoint of bioimaging. Herein, we demonstrate that the redox potentials of the 1,1,4,4-tetraanilinobutadiene can be precisely controlled by the donating properties of the amino group on the aniline unit as well as the number of halogen atoms on the aryl units at 2,3-positions on the butadiene. In contrast, the NIR absorption bands mainly depend on the number of halogen atoms irrespective to the donating properties of aniline unit. Thus, the hexaarylbutadiene skeleton is proven to be a versatile scaffold to develop less-explored organic NIR electrochromic materials, whose redox and spectroscopic properties can be finely tuned by modifying/attaching the proper substituents.
• Identification of synthetic inhibitors for the DNA binding of intrinsically disordered circadian clock transcription factors

  Yusuke Hosoya, Wataru Nojo, Isao Kii, Takanori Suzuki, Miki Imanishi, Junko Ohkanda

  Chemical Communications 56 76 11203 - 11206 2020年 

  Essential components of the human circadian clock, BMAL1 and CLOCK, which are intrinsically disordered transcription factors, were expressed and subjected to a fluorescent in vitro binding assay using an E-box DNA fragment. Screening of a chemical library identified 5,8-quinoxalinedione (1), which was found to inhibit binding of the heterodimer BMAL1/CLOCK to E-box at low micromolar concentrations.
• Electric-Field-Controllable Conductance Switching of an Overcrowded Ethylene Self-Assembled Monolayer

  Shintaro Fujii, Masato Koike, Tomoaki Nishino, Yoshiaki Shoji, Takanori Suzuki, Takanori Fukushima, Manabu Kiguchi

  Journal of the American Chemical Society 141 46 18544 - 18550 2019年11月20日 

  Molecular isomerism has been discussed from the viewpoint of the tiniest switch and memory elements in electronics. Here, we report an overcrowded ethylene-based molecular conductance switch, which fulfills all the essential requirements for implementation into electronic devices, namely, electric-field-controllable reversible conductance change with a molecular-level spatial resolution, robust conformational bistability under ambient conditions, and ordered monolayer formation on electrode surfaces. The conformational state of this overcrowded ethylene, represented by a folded or twisted conformer, is susceptible to external environments. Nanoscopic measurements using scanning tunneling microscopy techniques, together with theoretical simulations, revealed the electronic properties of each conformer adsorbed on Au(111). While the twisted conformer prevails in the molecularly dispersed state, upon self-assembly into a monolayer, a two-dimensional network structure of the folded conformer is preferentially formed due to particular intermolecular interaction. In the monolayer state, folded-to-twisted and its reverse isomerization can be controlled by the modulation of electric fields.
• Photo- and Thermal Interconversion of Multiconfigurational Strained Hydrocarbons Exhibiting Completely Switchable Oxidation to Stable Dicationic Dyes

  Yusuke Ishigaki, Yuki Hayashi, Takanori Suzuki

  Journal of the American Chemical Society 141 45 18293 - 18300 2019年11月13日 [査読有り][通常論文]
   

  Highly strained hydrocarbons with two di/tribenzocycloheptatriene units were designed as electrochromic overcrowded ethylenes that undergo reversible interconversion with stable dicationic dyes. Due to severe steric repulsion, two configurational isomers (anti,anti-folded and syn,anti-folded forms) were isolated as stable entities. Photo- and thermal interconversion of these isomers proceeded cleanly: one-way photo-isomerization occurred from anti,anti- to syn,anti-form and one-way thermal isomerization was observed from syn,anti- to anti,anti-form. Even though both isomers undergo two-electron oxidation into the same twisted dications, quite different oxidation potentials enable completely selective oxidation of syn,anti-isomers. Thus, the present multiconfigurational strained hydrocarbons are capable of switching of activation/deactivation of their electrochromic properties by light/heat.
• Molecular Wires with Controllable π-Delocalization Incorporating Redox-Triggered π-Conjugated Switching Units

  Wataru Nojo, Hitomi Tamaoki, Yusuke Ishigaki, Ryo Katoono, Kenshu Fujiwara, Takanori Fukushima, Takanori Suzuki

  ChemPlusChem 84 6 634 - 642 Wiley 2019年06月24日 [査読有り][通常論文]
   

  © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim A perfluorobiphenyl-2,2′-diyl dication and its corresponding dihydrophenanthrene-type electron donor are interconvertible upon two-electron transfer. Redox-triggered C−C bond-formation/cleavage caused a drastic change in the torsion angle of the biphenyl unit. Thus, π-delocalization ON/OFF switching was observed as a change in the UV absorption upon electrolysis of the linearly extended analogue with two phenylethynyl groups. A further extended π-system with a molecular length of ca. 3.5 nm, which has two switching units, was synthesized. Spectroelectrograms as well as voltammetric analyses showed that the two units act nearly simultaneously because of the very small inter-unit electrostatic repulsion in the tetracationic state. Thus, the present pair is a promising candidate as a switching unit for “molecular wires” with controllable π-delocalization, in which a higher ON/OFF ratio of delocalization could be realized by incorporating multiple switching units.
• Selective Formation of a Mixed‐Valence State from Linearly Bridged Oligo(aromatic diamines): Drastic Structural Change into a Folded Columnar Stack for Half‐filled Polycations

  Wataru Nojo, Yusuke Ishigaki, Takashi Takeda, Tomoyuki Akutagawa, Takanori Suzuki

  Chemistry – A European Journal 25 32 7759 - 7765 Wiley 2019年06月07日 [査読有り][通常論文]
   

  A method to obtain an organic mixed-valence state with long-range delocalization is proposed, which enables the selective generation of half-filled (n/2-charged) polycations from linearly bridged oligomers with n electron-donating units. When pi-extended phenylenediamine units are connected by meta-xylylene-type spacers, the resulting oligomers adopt non-folded structures in the neutral state owing to the non-conjugating and flexible nature of the spacer, whereas the structure shows a drastic change into a one-dimensional columnar stack upon oxidation to the corresponding half-filled polycations. Although they are nano-sized discrete molecules, they can mimic the electronic structure of crystalline organic conductors in a mixed-valence state. The key for the oligomer design is adoption of the best-matched spacer that facilitates formation of the singly charged pimer in the dichromophoric system whereas the corresponding doubly charged pi-dimer is disfavored.
• Total synthesis of kehokorins A and B

  Kenshu Fujiwara, Ryosuke Motousu, Daisuke Sato, Yoshihiko Kondo, Uichi Akiba, Takanori Suzuki, Tetsuo Tokiwano

  Tetrahedron Letters 60 18 1299 - 1301 2019年05月02日 

  © 2019 Elsevier Ltd The total synthesis of a dibenzofuran rhamnoside, kehokorin A, and its aglycone, kehokorin B, was achieved via a route including Suzuki-Miyaura cross-coupling followed by Ullmann ether synthesis to form a dibenzofuran, stepwise bromination at C7 of the dibenzofuran, a second Suzuki-Miyaura cross-coupling to install a 4-methoxyphenyl group at C7, and rhamnosylation.
• Synthesis of the cyclohexene segment of portimine

  Takafumi Saito, Kenshu Fujiwara, Yoshihiko Kondo, Uichi Akiba, Takanori Suzuki

  Tetrahedron Letters 60 4 386 - 389 2019年01月24日 

  © 2018 Elsevier Ltd The synthesis of the cyclohexene segment of portimine, a marine cytotoxin from the dinoflagellate Vulcanodinium rugosum, was achieved. The route includes an acylation/aldol reaction from 3-ethoxycyclohex-2-enone to create the C3 center, the 1,4-addition of a vinyl group at C16, the diastereoselective dihydroxylation of the vinyl group to generate the C15 center, a vinylation/dehydration sequence to set up the diene moiety, and stepwise installation of the amino-group-substituted C1 unit.
• A novel condensed heterocyclic quinone with a dibenzofuranobisthiadiazole skeleton

  Kazuma Sugawara, Wataru Nojo, Yusuke Ishigaki, Junko Ohkanda, Takanori Suzuki

  Heterocycles published online. 1 99 - 103 2019年 [査読無し][通常論文]
   

  Upon oxidation of hydroquinone fused with 1,2,5-thiadiazole by using FeCl3, a novel dibenzofurano[1,2-c:6,7-c]bis[1,2,5]thiadiazole-type quinone was obtained whereas the similar dimerization-condensation process did not occur for the pyrazine-fused hydroquinone under the similar conditions.
• Two-way chromic systems based on tetraarylanthraquinodimethanes: Electrochromism in solution and mechanofluorochromism in a solid state

  Ishigaki Y, Sugawara K, Yoshida M, Kato M, Suzuki T

  Bulletin of the Chemical Society of Japan 92 7 1211 - 1217 2019年 [査読有り][通常論文]
   

  Tetraarylanthraquinodimethane derivatives 1 with butterfly-shaped folded structures and the corresponding dications 1(2+) with twisted conformations can undergo interconversion upon two-electron transfer, which is accompanied by a drastic color change. While reversible electrochromic behavior occurs in solution, electron donors 1 exhibit fluorescence only in the solid state. The emission color changed upon grinding assynthesized samples of 1, and the original emission color was recovered by a dissolving-drying process. Such mechanofluoro-chromic behavior can be accounted for by the results of powder X-ray diffraction (PXRD), for which as-synthesized crystalline sample was transformed into an amorphous state after grinding. Thus, the title electron donors 1 provided two-way chromic systems exhibiting electrochromism in solution as well as mechanofluorochromism in a solid state.
• Dual dynamic chirality generated in the assembly of three achiral rods through the three-fold twisting of a macrocycle

  Ryo Katoono, Kazuki Sakamoto, Takanori Suzuki

  Chemical Communications 55 38 5503 - 5506 2019年 [査読有り][通常論文]
   

  We demonstrated dynamic chirality based on assemblies of three achiral rods with a twisted macrocycle. The three-fold twisting of a macrocycle can lead to two different chiral forms with C-2- or D-3-symmetry. Through a transmission of chirality to each dynamic chiral form, a helical-sense preference was successfully induced.
• Chiral diversification through the assembly of achiral phenylacetylene macrocycles with a two-fold bridge

  Ryo Katoono, Keiichi Kusaka, Yuki Saito, Kazuki Sakamoto, Takanori Suzuki

  Chemical Science 10 18 4782 - 4791 2019年 [査読有り][通常論文]
   

  Multiple chiral molecules were generated through the assembly and double-bridging of achiral phenylacetylene macrocycles.

• Engineering of Electrochromic Materials as Activatable Probes for Molecular Imaging and Photodynamic Therapy

  Luyan Wu, Yidan Sun, Keisuke Sugimoto, Zhiliang Luo, Yusuke Ishigaki, Kanyi Pu, Takanori Suzuki, Hong-Yuan Chen, Deju Ye

  Journal of the American Chemical Society 140 47 16340 - 16352 2018年11月28日 [査読有り][通常論文]
   

  Electrochromic materials (EMs) are widely used color-switchable materials, but their applications as stimuli-responsive biomaterials to monitor and control biological processes remain unexplored. This study reports the engineering of an organic pi-electron structure-based EM (dicationic 1,1,4,4-tetraarylbutadiene, 1(2+)) as a unique hydrogen sulfide (H2S)-responsive chromophore amenable to build H2S-activatable fluorescent probes (1(2+)-semiconducting polymer nanoparticles, 1(2+)-SNPs) for in vivo H2S detection. We demonstrate that EM 1(2+), with a strong absorption (500-850 nm), efficiently quenches the fluorescence (580, 700, or 830 nm) of different fluorophores within 1(2+)-SNPs, while the selective conversion into colorless diene 2 via H2S-mediated two-electron reduction significantly recovers fluorescence, allowing for non-invasive imaging of hepatic and tumor H2S in mice in real time. Strikingly, EM 1(2+) is further applied to design a near-infrared photosensitizer with tumor-targeting and H2S-activatable ability for effective photodynamic therapy (PDT) of H2S-related tumors in mice. This study demonstrates promise for applying EMs to build activatable probes for molecular imaging of H2S and selective PDT of tumors, which may lead to the development of new EMs capable of detecting and regulating essential biological processes in vivo.
• Transmission of Point Chirality to Axial Chirality for Strong Circular Dichroism in Triarylmethylium-o,o-dimers

  Takanori Suzuki, Yusuke Ishigaki, Tomohiro Iwai, Yuki Hayashi, Aiichiro Nagaki, Ryo Katoono, Kenshu Fujiwara, Jun-ichi Yoshida

  Synlett 29 16 2147 - 2154 2018年10月25日 [査読有り][通常論文]
   

  Triarylmethylium-o,o-dimers adopt a twisted geometry so that two diarylmethyliums are stacked in a slipped manner. Thus, chiral auxiliaries on the aryl groups induce a preference in the axial chirality of the central biphenyl unit. Strong circular dichroism is attained through exciton coupling, which can be used for additional spectral output in their electrochromic behavior. Diastereoselectivity based on - stacking exhibits unique solvent effects, thus endowing multifunctional response properties.
• Double bond formation based on nitroaldol reaction and radical elimination: A prototype segment connection method for the total synthesis of nigricanoside A dimethyl ester

  Takayuki Tsunoda, Kenshu Fujiwara, Satoshi Okamoto, Yoshihiko Kondo, Uichi Akiba, Yusuke Ishigaki, Ryo Katoono, Takanori Suzuki

  Tetrahedron Letters 59 19 1846 - 1850 2018年05月 [査読有り][通常論文]
   

  © 2018 Elsevier Ltd During the course of our studies toward the total synthesis of nigricanoside A dimethyl ester, a prototype method for the connection of the left- and right-half segments at the C9′–C10′ double bond was developed using a model system. The method was based on a simple three-step process including: (i) a nitroaldol reaction, (ii) chlorination or thionocarbonylation, and (iii) radical elimination.
• Longest C–C Single Bond among Neutral Hydrocarbons with a Bond Length beyond 1.8 Å

  Yusuke Ishigaki, Takuya Shimajiri, Takashi Takeda, Ryo Katoono, Takanori Suzuki

  Chem 4 4 795 - 806 2018年04月12日 [査読有り][通常論文]
   

  On the basis of the intramolecular “core-shell strategy,” we designed dihydropyracylene with two spiro(dibenzocycloheptatriene) units, for which theoretical calculations predicted a very weak C–C bond with a bond length around 1.8 Å. This bond is expanded by the forced adoption of an eclipsed conformation and by angle strain through a “scissor effect.” The highly strained hydrocarbon was isolated as a thermally stable compound with no signs of diradical contribution because the weak C–C bond (core) is protected by the shape-persistent fused-ring structure (shell). A Raman shift corresponding to the C–C stretching vibration (587 cm−1) was very different from that for ethane (993 cm−1). The bond length determined by X-ray (1.806(2) Å) was greater than the shortest non-bonded intramolecular C…C contact (1.80(2) Å). The assumed limit for a C–C bond (1.803 Å) by supposing linear correlation between bond length and bond-dissociation energy for covalent bonding was proven to be invalid. The nature of chemical bonds is of fundamental importance in chemistry. Clarifying the new facets of covalent bonds is also helpful to promote green chemistry by allowing chemists to design novel chemical products and new processes to advance sustainability. We have successfully synthesized highly strained “core-shell”-type hydrocarbons and demonstrated that the C–C covalent bond can be expanded beyond 1.80 Å, which is 1.17 times greater than the standard length (1.54 Å). By the discovery of such a “hyper covalent bond,” the covalently bonded state and non-bonded state are seamlessly connected in terms of the interatomic distance. Compounds with the hyper covalent bond are potential candidates for making a novel class of materials whose crystals, films, or polymers can respond to external mechanical stimuli with anisotropic contraction or expansion of the matter, accompanied by reversible compression, extension, or fission of the “bond” in the molecule. Compounds with an ultralong C–C single bond have been successfully constructed in three steps from commercially available dihalo aromatics. The intramolecular “core-shell strategy” is a key tactic for stabilizing compounds with an ultralong C–C bond. Using this concept could lead to an even longer C–C bond (“hyper covalent bonds” with a bond length of 1.8–2.0 Å) because the covalently bonded state and non-bonded state are seamlessly connected in terms of the interatomic distance.
• An improved synthesis of the C42–C52 segment of ciguatoxin 3C

  Takafumi Saito, Kenshu Fujiwara, Yusuke Sano, Takuto Sato, Yoshihiko Kondo, Uichi Akiba, Yusuke Ishigaki, Ryo Katoono, Takanori Suzuki

  Tetrahedron Letters 59 14 1372 - 1376 2018年04月 [査読有り][通常論文]
   

  © 2018 Elsevier Ltd In our previously reported method for the construction of the IJKLM-ring of ciguatoxin 3C (CTX3C), the lengthy synthetic process for the intermediate C42–C52 (L-ring) segment was problematic. Therefore, a new and improved procedure for the C42–C52 segment, having modified protecting groups, was developed. The new route includes a chirality transferring Ireland-Claisen rearrangement for the construction of the vicinal dimethyl branching at C47–48, a one-pot cyclization process for the establishment of the stereocenters at C45 and C46 as well as the γ-hydroxy δ-lactone framework corresponding to the L-ring, and Brown's asymmetric crotylboration for the installation of the stereocenters at C43 and C44. The new C42–C52 segment was successfully coupled with the previously reported C32–C41 (I-ring) segment to produce the IJKLM-ring.
• Narrower HOMO-LUMO gap attained by conformational switching through peripheral polyarylation in 1,4,5,8-tetraaza-9,10-anthraquinodimethanes

  Suzuki, T, Ishigaki, Y, Sugawara, K, Umezawa, Y, Katoono, R, Shimoyama, A, Manabe, Y, Fukase, K, Fukushima, T

  Tetrahedron 74 18 2239 - 2244 2018年04月 [査読有り][通常論文]
   

  2,3,6,7,11,11,12,12-Octaphenyl-1,4,5,8-tetraaza-9,10-anthraquinodimethane was prepared as a sterically hindered molecule from 2,3,6,7-tetraphenyl-1,4,5,8-tetraaza-9,10-anthraquinone via bis(dibromomethylene) derivative through the quadruple Suzuki-Miyaura coupling reaction. An X-ray analysis revealed that steric repulsion is relieved mainly by twisting the exomethylene bonds, which is less common deformation for hindered quinodimethanes. According to the OFT calculations, the folded geometry with bent exomethylene bonds is the metastable conformer, and thus the nitrogen atoms at peri-positons and polyaryl substituents induce novel switching for the preferred geometry of 9,10-anthraquinodimethane skeleton from the common bent form to the twisted form, which causes a decrease in the HOMO-LUMO-gap energy by ca. 1 eV. (C) 2018 Elsevier Ltd. All rights reserved.
• Expandability of a long C–O bond by a scissor effect in acenaphthofuran

  Yasuto Uchimura, Takuya Shimajiri, Yusuke Ishigaki, Ryo Katoono, Takanori Suzuki

  Chemical Communications 54 73 10300 - 10303 Royal Society of Chemistry ({RSC}) 2018年 [査読有り][通常論文]
   

  The angle strain induced by ring annulation on a spiro-type naphthofuran weakens its C(sp(3))-O bond at the opposite peri-position and endows expandability, so that quite different bond lengths [1.493(3)-1.526(6) angstrom] are determined for the elongated C(sp(3))-O bond of the corresponding spiro-acenaphthofuran derivative upon X-ray analyses of its pseudopolymorphs.
• Dynamic or undynamic chirality generated by helical arrangement of a shape-persistent ring and rod doubly bridged in a molecule

  Ryo Katoono, Yudai Obara, Keiichi Kusaka, Takanori Suzuki

  Chemical Communications 54 7 735 - 738 2018年 [査読有り][通常論文]
   

  We synthesized molecular assemblies of a ring and rod that were covalently bound in a molecule. The bridged components were helically arranged in a threaded or unthreaded form to show unique chiroptical properties based on shape-persistent m-phenylacetylene rings with six, five and four units and phenylene-ethynylene rods.
• Supramolecular chiroptical switching of helical-sense preferences through the two-way intramolecular transmission of a single chiral source

  Ryo Katoono, Keiichi Kusaka, Yuki Tanaka, Kenshu Fujiwara, Takanori Suzuki

  Organic and Biomolecular Chemistry 16 7 1167 - 1171 2018年 [査読有り][通常論文]
   

  We demonstrate a chiroptical switching system with a simple molecule. The molecule contains a pair of chromophores of diphenylacetylene that are linked with a diyne bond and arranged to exert exciton coupling in helically folded forms with (M)- or (P)-helicity. A tertiary amide group is attached to each end of the looped molecule. The amide carbonyls were used to capture a ditopic hydrogen-bonding guest. A chiral auxiliary group on the amide nitrogen acted as a chiral handle to control the helical-sense preference of dynamic helical forms of the loop. The helical-sense preference is brought about by an intramolecular transmission of point chirality associated with the loop. The preferred sense was switched upon complexation with an achiral additive through the formation of hydrogen bonds. In both states, before and after complexation, the helical-sense preferences were controlled through two-way transmission of the single chiral source.
• Enhanced circular dichroism at elevated temperatures through complexation-induced transformation of a three-layer cyclophane with dualistic dynamic helicity

  Ryo Katoono, Yudai Obara, Kenshu Fujiwara, Takanori Suzuki

  Chemical Science 9 8 2222 - 2229 2018年 [査読有り][通常論文]
   

  When two planes stacked one above the other are twisted, they provide a dynamic pair of helical conformations with (M)- or (P)-helicity. We designed a three-layer cyclophane that consists of two such dynamic pairs: the top and middle planes, and the middle and bottom planes. Hence, several global conformations could be created for the overall molecule, e.g., double-helical forms with a pair with the same helicity [(M,M) or (P,P)], and a meso-like form with a pair with a different helicity (M,P). These conformations dynamically interconvert to each other in solution. Chiroptical properties were given by the helical-sense preference of the double-helical forms, which was brought about through complexation with a chiral hydrogen-bonding guest. In terms of the conformational energy in a complexed state, when a desirable relationship between double-helical and meso-like forms was attained, complexation-induced circular dichroism was enhanced at elevated temperatures and decreased at lowered temperatures.
• Direct synthesis of aryl-annulated [c]carbazoles by gold(i)-catalysed cascade reaction of azide-diynes and arenes

  Yuiki Kawada, Shunsuke Ohmura, Misaki Kobayashi, Wataru Nojo, Masaki Kondo, Yuka Matsuda, Junpei Matsuoka, Shinsuke Inuki, Shinya Oishi, Chao Wang, Tatsuo Saito, Masanobu Uchiyama, Takanori Suzuki, Hiroaki Ohno

  Chemical Science 9 44 8416 - 8425 2018年 [査読有り][通常論文]
   

  The gold-catalysed annulation of conjugated alkynes bearing an azido group with arenes gave annulated [c]carbazoles.

• 9,10-Dihydrophenanthrene with Two Spiro(dibenzocycloheptatriene) Units: A Highly Strained Caged Hydrocarbon Exhibiting Reversible Electrochromic Behavior

  Yusuke Ishigaki, Yuki Hayashi, Kazuma Sugawara, Takuya Shimajiri, Wataru Nojo, Ryo Katoono, Takanori Suzuki

  MOLECULES 22 11 2017年11月 [査読有り][通常論文]
   

  The title dispiro hydrocarbon 1 was designed as a new electrochromic material. This multiply clamped hexaphenylethane-type electron donor was prepared from 2,2'-diiodobiphenyl via biphenyl-2,2'-diylbis(dibenzotropylium) 2(2+) salt. X-ray analysis of 1 revealed a highly strained structure as reflected by an elongated ethane bond [bond length: 1.6665(17) angstrom] and nearly eclipsed conformation. The weakened bond was cleaved upon two-electron oxidation to regenerate the deeply colored dication 2(2+). The reversible interconversion between 1 and 2(2+) is accompanied not only by a drastic color change but also by C-C bond formation/cleavage. Thus, the voltammogram showed a pair of well-separated redox waves, which is characteristic of "dynamic redox (dyrex)" behavior. The tetrahydro derivative of 1 with two units of spiro(dibenzocycloheptadiene), which suffers from more severe steric congestion, was also prepared. The crystallographically determined bond length for the central C-C bond [1.705(4) angstrom] is greatest among the values reported for 9,9,10,10-tetraaryl-9,10-dihydrophenanthrene derivatives.
• Back Cover: Organic Molecular Layer with High Electrochemical Bistability: Synthesis, Structure, and Properties of a Dynamic Redox System with Lipoate Units for Binding to Au(111) (ChemPlusChem 7/2017)

  Eisuke Ohta, Hiromitsu Uehara, Ying Han, Kazuhisa Wada, Hidenori Noguchi, Ryo Katoono, Yusuke Ishigaki, Hiroshi Ikeda, Kohei Uosaki, Takanori Suzuki

  ChemPlusChem 82 7 1043 - 1047 2017年07月14日 [査読有り][通常論文]
   

  Biphenyl-2,2'-diylbis(10-methyl-9-methyleneacridan)-type electron donor 1, which has two tethered cyclic disulfide units at the 6,6'-positions, was designed and synthesized as the first member of a dynamic redox (dyrex) system that can form molecular layers on a Au(111) electrode. Upon the two-electron (2 e) oxidation of 1, the persistent dicationic dye 22+ was generated with the formation of a new C = C bond, which is reversibly cleaved upon 2e reduction to regenerate 1 (dyrex behavior). Similar dyrex interconversion occurs in the molecular layer of 1 on gold. The chemical identities of 1/Au and electrochemically generated 2(2+)/Au were unambiguously determined by in situ IR spectroscopy in the attenuated total reflection mode. In situ scanning tunneling microscopy (STM) was conducted under electrochemical conditions to examine the surface structure of 1 adsorbed on a Au(111) electrode. Although no longrange- ordered morphology was found in the STM image of 1, an in situ STM study of the potential-induced dyrex reaction of 1 to 2(2+) showed that the grained spots in the image became slightly brighter.
• Organic Molecular Layer with High Electrochemical Bistability: Synthesis, Structure, and Properties of a Dynamic Redox System with Lipoate Units for Binding to Au(111)

  Eisuke Ohta, Hiromitsu Uehara, Ying Han, Kazuhisa Wada, Hidenori Noguchi, Ryo Katoono, Yusuke Ishigaki, Hiroshi Ikeda, Kohei Uosaki, Takanori Suzuki

  CHEMPLUSCHEM 82 7 1043 - 1047 2017年07月 [査読有り][通常論文]
   

  Biphenyl-2,2'-diylbis(10-methyl-9-methyleneacridan)-type electron donor 1, which has two tethered cyclic disulfide units at the 6,6'-positions, was designed and synthesized as the first member of a dynamic redox (dyrex) system that can form molecular layers on a Au(111) electrode. Upon the two-electron (2 e) oxidation of 1, the persistent dicationic dye 22+ was generated with the formation of a new C = C bond, which is reversibly cleaved upon 2e reduction to regenerate 1 (dyrex behavior). Similar dyrex interconversion occurs in the molecular layer of 1 on gold. The chemical identities of 1/Au and electrochemically generated 2(2+)/Au were unambiguously determined by in situ IR spectroscopy in the attenuated total reflection mode. In situ scanning tunneling microscopy (STM) was conducted under electrochemical conditions to examine the surface structure of 1 adsorbed on a Au(111) electrode. Although no longrange- ordered morphology was found in the STM image of 1, an in situ STM study of the potential-induced dyrex reaction of 1 to 2(2+) showed that the grained spots in the image became slightly brighter.
• Bis(diarylethenyl)-thiophenes, -bithiophenes, and -terthiophenes: a new series of electrochromic systems that exhibit a fluorescence response

  Yusuke Ishigaki, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Hiroki Higuchi, Hirotsugu Kikuchi, Takanori Suzuki

  CANADIAN JOURNAL OF CHEMISTRY 95 3 243 - 252 2017年03月 [査読有り][通常論文]
   

  2,5-Bis(diarylethenyl)thiophenes (1) and their bithiophene (2) and terthiophene (3) homologues were designed as a new series of violene/cyanine-hybrid-type electrochromic materials. Alkoxyphenyl and dialkylaminophenyl groups are used as the aryl group in the cyanine parts of 1/2/3O and 1/2/3N, respectively, which emit fluorescence in the neutral state but not in the oxidized state. Voltammetric analyses of 18 newly prepared electron donors show that they all undergo two reversible one-electron oxidations. Redox potentials, UV-vis spectral features, and fluorescence quantum yields are important parameters for characterizing the present electrochromic behavior with a fluorescence response, and can be finely tuned by changing aryl groups in the cyanine part, the number of thiophene rings in the violene part, and the alkyl-chain length of the alkoxyphenyl or diaklylaminophenyl groups (R = CH3, C8H17, C16H33), which makes this a versatile platform for the design of novel electrochromic materials.
• Synthesis of the ABCDEF-ring of ciguatoxin 3C

  Takuto Sato, Kenshu Fujiwara, Keisuke Nogoshi, Akiyoshi Goto, Daisuke Domon, Natsumi Kawamura, Yoshitaka Nomura, Daisuke Sato, Hideki Tanaka, Akio Murai, Yoshihiko Kondo, Uichi Akiba, Ryo Katoono, Hidetoshi Kawai, Takanori Suzuki

  TETRAHEDRON 73 6 703 - 726 2017年02月 [査読有り][通常論文]
   

  The synthesis of the ABCDEF-ring of ciguatoxin 3C was achieved via a route that included anion coupling of a dimethyldithioacetal mono-S-oxide derivative corresponding to the AB-ring and an aldehyde corresponding to the EF-ring, followed by cyclization using reductive etherification. The AB-ring was synthesized from a known D-glucose derivative based, on ring-closing olefin metathesis, and the EF-ring was prepared by a process employing chirality-transferring Ireland-Claisen rearrangement and ring-closing olefin metathesis. (C) 2016 Elsevier Ltd. All rights reserved.
• OXIDATIVE DESULFURIZATION OF ELECTRON-DONATING 5,5,7,7-TETRAARYL-5,7-DIHYDRODIBENZO[c,e]THIEPINS AND THE RELATED HETEROCYCLES: GENERATION OF DICATIONIC DYES UPON TWO-ELECTRON OXIDATION

  Suzuki, Takanori, Kuroda, Takuma, Tamaoki, Hitomi, Higasa, Sho, Nehira, Tatsuo, Katoono, Ryo, Ishigaki, Yusuke, Fujiwara, Kenshu, Fukushima, Takanori, Yamada, Hidetoshi

  Heterocycles 95 2 816 - 829 2017年 [査読有り][通常論文]
   

  Upon oxidation of the title heterocycle (1A) with dimethylamino groups, elemental sulfur is extruded to form dicationic dye (1B(2+)), from which the starting dibenzothiepin derivative was generated by the reaction with Na2S. The bay-region substituents enhance configurational stability, so that, the optically pure heterocycles [(M)-2A, (M)-3A)] can be obtained in terms of helicity of one-handedness by starting with the corresponding optically pure dicationic dyes [(R)-2B(2+), (R)-3B(2+))]. Similar oxidative desulfurization occurs in dibenzo-1,5-oxathiocin 4A, a structurally related 8-membered heterocycle.
• STEREOSELECTIVE ENCAPSULATION FOR A TRIARYLMETHYLIUM o,o-DIMER BY NATURAL gamma-CYCLODEXTRIN: ORIGIN OF CHIRAL RECOGNITION FOR THE AXIALLY CHIRAL DICATIONIC GUEST

  Suzuki, Takanori, Suzuki, Takanori, Ceron-Carrasco, Jose P., Ceron-Carrasco, Jose P., Tamaoki, Hitomi, Tamaoki, Hitomi, Ishigaki, Yusuke, Ishigaki, Yusuke, Katoono, Ryo, Katoono, Ryo, Fukushima, Takanori, Fukushima, Takanori, Perez-Sanchez, Horacio, Perez-Sanchez, Horacio

  Heterocycles 94 6 1123 - 1132 2017年 [査読有り][通常論文]
   

  Upon 1:1 complexation with gamma-cyclodextrin (CyD) in water, easily interconverting rotational isomers of biphenyl-2,2'-diylbis[bis(4-dimethylaminophenyl)methylium] (R)/(S)-1a(2+) were biased to prefer an R configuration (75:25 at 25 degrees C). Docking and quantum chemical calculations revealed two modes (on-top and botton-side) of encapsulation of gamma-CyD, which shed a light on the origin of the first chiral recognition of axially chiral dicationic dyes by using natural CyDs.
• Redox-induced Conformational Changes in 1,3-Propylene- and m-Xylylenebis[5-(10-butyl-5,10-dihydrobenzo[a]indolo[2,3-c]carbazole)]: Twin-BIC Donors that Form Sandwich-like Dimeric Cations Exhibiting NIR Absorption

  Takanori Suzuki, Wataru Nojo, Yuto Sakano, Ryo Katoono, Yusuke Ishigaki, Hiroaki Ohno, Kenshu Fujiwara

  CHEMISTRY LETTERS 45 7 720 - 722 2016年07月 [査読有り][通常論文]
   

  The title electron-donors with two units of a disk-shaped heterocyclic diamine undergo two-stage stepwise one-electron oxidation to the corresponding cation radicals and dication diradicals. They adopt a stacked geometry as in pimers and pi-dimers, respectively. In contrast, the third and fourth oxidation processes occur nearly at the same potential, indicating that tricationic/tetracationic species prefer the extended geometry. The similar redox-induced conformational changes were not observed in 1,5-pentylene or o-xylylene derivatives, which prefer the extended geometry irrespective of the oxidation states.
• Assembly of an Axially Chiral Dynamic Redox System with a Perfluorobiphenyl Skeleton into Dumbbell‐ or Tripod‐type Electron Donors

  Hitomi Tamaoki, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki

  Angewandte Chemie 128 7 2628  2016年02月12日 [査読有り][通常論文]
  
• Assembly of an Axially Chiral Dynamic Redox System with a Perfluorobiphenyl Skeleton into Dumbbell- or Tripod-type Electron Donors

  Hitomi Tamaoki, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki

  ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 55 7 2582 - 2586 2016年02月 [査読有り][通常論文]
   

  The incorporation of F atoms endows a diethenylbiphenyl-based electron donor with configurational stability and SNAr reactivity. The former enables the dynamic redox pair of (R-ax)-1/(R-ax,R,R)-1(2+) to exhibit drastic UV/Vis and CD spectral changes upon electrolysis, whereas the latter makes it possible for (R-ax)-1 to serve as a useful chiral synthon for the production of larger assemblies [(R-ax,R-ax)-2d,p,m and (R-ax,R-ax,R-ax)-3] containing two or three dyrex units. These dyads and triad also exhibit a clean electrochiroptical response with isosbestic points owing to one-wave multi-electron transfer.
• Dynamic helical cyclophanes with two quadruply-bridged planes arranged in an "obverse and/or reverse" relation

  Ryo Katoono, Shunsuke Kawai, Takanori Suzuki

  CHEMICAL SCIENCE 7 5 3240 - 3247 2016年 [査読有り][通常論文]
   

  We describe the design of two types of cyclophanes that generate dynamic helicity through the twisting of two planes in a clockwise or counterclockwise direction to give (M)- or (P)-helicity. We used a rectangular and anisotropic plane of 1,2,4,5-tetrakis(phenylethynyl) benzene (TPEB), since it can be stacked in pairs in two ways, in parallel or orthogonally, to be identified as distinct cyclophane molecules. We adopted a synthetic strategy for obtaining these two cyclophanes as a mixture using a macrocyclic intermediate that possessed two rotatable phenyl rings. We introduced necessary parts into the rotators to give a mixture of rotational isomers leading to a parallel or orthogonal arrangement of TPEBs, and then doubly bridged two planes of TPEB to form quadruply-bridged cyclophanes. We consider that such two planes in each cyclophane are in an "obverse and/or reverse" relation. In each cyclophane, we found unique dynamic helical forms with (M)- or (P)-helicity as well as an inherently non-chiral form. Normally, the screw-sense preference of dynamic helicity would be controlled through the intramolecular or supramolecular transmission of central chirality, when a chiral auxiliary is attached to the cyclophanes or a chiral guest is allowed to form a complex with the cyclophanes. In a case where two different substitution groups were used on bridging units to generate planar chirality in each cyclophane, the screw-sense preference was controlled through the arrangement of these substitution groups, and did not depend on the transmission of central chirality. Two different substitution groups desymmetrize the enantiomeric forms with (M)- or (P)-helicity generated in each dynamic helical cyclophane so that two dynamic helical forms with (M)- or (P)-helicity can be in a diastereomeric relation. Thus, a particular screw sense of dynamic helicity can be preferred, regardless of whether or not the two substitution groups possess some chiral element.
• REDOX-MEDIATED REVERSIBLE sigma-BOND FORMATION/CLEAVAGE

  Suzuki, Takanori, Tamaoki, Hitomi, Nishida, Jun-ichi, Higuchi, Hiroki, Iwai, Tomohiro, Ishigaki, Yusuke, Hanada, Keisuke, Katoono, Ryo, Kawai, Hidetoshi, Fujiwara, Kenshu, Fukushima, Takanori, Nishinaga, T

  Organic Redox Systems: Synthesis, Properties, and Applications 2016年 [査読有り][通常論文]
  
• Planar chiral desymmetrization of a two-layered cyclophane and control of dynamic helicity through the arrangement of two nonstereogenic centers

  Ryo Katoono, Takanori Suzuki

  CHEMICAL COMMUNICATIONS 52 5 1029 - 1031 2016年 [査読有り][通常論文]
   

  We designed a planar chiral two-layered cyclophane, which is inherently achiral but desymmetrized by the arrangement of two nonstereogenic centers. We demonstrate the control of dynamic helicity that is generated by the helical twisting of two-layered planes in the cyclophane, where methyl and cyclohexylmethyl groups act as directing groups.
• Synthesis of Ganbajunins D and E and the Proposed Structure of

  Fujiwara K, Kushibe K, Sato T, Norikura T, Matsue H, Iwai K, Katoono R, Suzuki T

  Eur. J. Org. Chem. 26 26 5798 - 5809 2015年09月 [査読有り][通常論文]
   

  The syntheses of ganbajunins D and E and of the structure proposed for thelephantin D, as well as its regioisomer, were achieved in a divergent manner via a common monoester intermediate. The proposed structure of thelephantin D had NMR chemical shifts different from those of natural thelephantin D. This supported Takahashi's suggestion that the true structure of natural thelephantin D should be the same as that of terrestrin C, as was deduced from the similarities in their NMR spectra. The presence of isomerization equilibria between 2′,5′- and 2′,6′-diacyloxy-p-terphenyl derivatives in solution, which are the cause of the inseparability of these derivatives, was also demonstrated by monitoring the dynamic transition from a 2′,6′-diacyloxy-p-terphenyl-rich mixture of the derivatives to an equilibrium mixture. The results of biological and chemical property tests - such as cytotoxicity against cancer cells, affinity towards Fe²⁺ ion, and antioxidative activity - with the synthesized compounds are also described.
• ChemInform Abstract: Electrochromic and Unique Chiroptical Properties of Helically Deformed Tetraarylquinodimethanes Generated from Less-Hindered Dicationic Precursors Upon Reduction

  Takanori Suzuki, Yuto Sakano, Tomohiro Iwai, Shinichi Iwashita, Youhei Miura, Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara, Yasushi Tsuji, Takanori Fukushima

  ChemInform 46 38 no - no 2015年09月 [査読有り][通常論文]
  
• Dynamic Figure Eight Chirality: Multifarious Inversions of a Helical Preference Induced by Complexation

  Ryo Katoono, Yuki Tanaka, Keiichi Kusaka, Kenshu Fujiwara, Takanori Suzuki

  JOURNAL OF ORGANIC CHEMISTRY 80 15 7613 - 7625 2015年08月 [査読有り][通常論文]
   

  We demonstrate two types of inversion of a helical preference upon the 1:1 complexation of a dynamic figure eight molecule with a guest molecule through the controlled transmission of point chirality. We designed a series of macrocycles that prefer a nonplanar conformation with figure eight chirality. These macrocycles are composed of a chirality-transferring unit (terephthalamide) and a structure-modifying unit (two o-phenylene rings spaced with a varying number of triple bonds). The former unit provides a binding site for capturing a guest molecule through the formation of hydrogen bonds. The attachment of chiral auxiliaries to the former unit induces a helical preference for a particular sense through the intramolecular transmission of point chirality. For relatively small-sized macrocycles, the preferred sense was reversed upon complexation with an achiral guest. Contrary preferences before and after complexation were both seen for chiral auxiliaries associated with a figure eight host through two-way intramolecular transmission of the single chiral source. Alternatively, the helical preference induced in relatively large-sized macrocycles was reversed only when a figure eight host formed a 1:1 complex with a particular enantiomeric guest through the supramolecular transmission of point chirality in the guest. This stereospecific inversion of a helical preference is rare.
• Reversible Interconversion between 11,11,12,12-Tetraaryl-1,4-diaza/-1,4,5,8-tetraazaanthraquinodimethanes and Their Cationic Species: Electrochromic and Halochromic Responses

  Takanori Suzuki, Yu Umezawa, Yuto Sakano, Hitomi Tamaoki, Ryo Katoono, Kenshu Fujiwara

  CHEMISTRY LETTERS 44 7 905 - 907 2015年07月 [査読有り][通常論文]
   

  11,11,12,12-Tetrakis (4-methoxyphenyl)-1,4-diaza-2,3-diphenyl- and -1,4,5,8-tetraaza-2,3,6,7-tetraphenylanthraquinodimethanes (1 and 2) adopt a bent geometry. They undergo reversible redox interconversion with twisted dications 1(2+) and 2(2+), exhibiting a vivid change in color (electrochromism). Treatment with acid also induced drastic color change due to the formation of protonated species H-1(+) and H-2(+) (halochromism), thus demonstrating their two-way-input chromic behavior.
• ChemInform Abstract: Bis(10-methylacridinium)s as a Versatile Platform for Redox-Active Functionalized Dyes and Novel Structures

  Takanori Suzuki, Takashi Takeda, Eisuke Ohta, Kazuhisa Wada, Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara

  ChemInform 46 18 no - no 2015年04月 [査読有り][通常論文]
  
• New Insights into the Hexaphenylethane Riddle: Formation of an α,o-Dimer

  Yasuto Uchimura, Takashi Takeda, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki

  Angewandte Chemie - International Edition 54 13 4010 - 4013 2015年03月 [査読無し][通常論文]
   

  © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Upon reduction of a 1H-cyclobuta[de]naphthalene-4,5-diylbis(diarylmethylium) species, a new C-C bond is formed between the Cα and Cortho atoms of the two chromophores, which presents an unprecedented coupling pattern for the dimerization of two trityl units. By attaching an annulated cyclobutane ring at the opposite peri position of the naphthalene core, the distance between the Cα carbon atoms was elongated beyond the limit of σ-bond formation through "scissor effects". The suppression of Cα-Cα bond formation, which would lead to hexaphenylethane-type compounds, is key to the first successful isolation of the α,o-adducts. The 5-diarylmethylene-6-triarylmethyl-1,3-cyclohexadiene unit in the α,o-adducts is stable, and isomerization of the cyclohexadiene unit into an aromatic system was not observed. The newly formed Cα-Cortho bond was cleaved upon two-electron oxidation to regenerate the dicationic dye. Beyond the ultralong C-C bond: Whereas an acenaphthene-5,6-diyl (n=2) undergoes smooth conversion into the corresponding tetraarylpyracene (the α,α-adduct) with an ultralong C-C bond, enhanced "scissor effects" in the cyclobutanaphthalene-4,5-diyl diradical (n=1) place the two Cα atoms so far apart that Cα-Cα bond formation is prevented. Instead, the α,o-adduct is formed
• New insights into the hexaphenylethane riddle: Formation of an α,o-dimer

  Yasuto Uchimura, Takashi Takeda, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki

  Angewandte Chemie - International Edition 54 13 4010 - 4013 Wiley-Blackwell 2015年03月 [査読有り][通常論文]
   

  © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Upon reduction of a 1H-cyclobuta[de]naphthalene-4,5-diylbis(diarylmethylium) species, a new C-C bond is formed between the Cα and Cortho atoms of the two chromophores, which presents an unprecedented coupling pattern for the dimerization of two trityl units. By attaching an annulated cyclobutane ring at the opposite peri position of the naphthalene core, the distance between the Cα carbon atoms was elongated beyond the limit of σ-bond formation through "scissor effects". The suppression of Cα-Cα bond formation, which would lead to hexaphenylethane-type compounds, is key to the first successful isolation of the α,o-adducts. The 5-diarylmethylene-6-triarylmethyl-1,3-cyclohexadiene unit in the α,o-adducts is stable, and isomerization of the cyclohexadiene unit into an aromatic system was not observed. The newly formed Cα-Cortho bond was cleaved upon two-electron oxidation to regenerate the dicationic dye.
• Bis(10-methylacridinium)s as a Versatile Platform for Redox-Active Functionalized Dyes and Novel Structures

  Takanori Suzuki, Takashi Takeda, Eisuke Ohta, Kazuhisa Wada, Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara

  CHEMICAL RECORD 15 1 280 - 294 2015年02月 [査読有り][通常論文]
   

  10-Methylacridinium is a stable aromatic cation exhibiting yellow-orange color and strong green fluorescence (FL), and can be used as a versatile building block in constructing a wide variety of novel -electron systems. The dications with the two chromophores connected by a proper spacer undergo reversible dyrex (dynamic redox) behavior, and C-C bond formation/cleavage is accompanied by their redox reactions. The prototype is biphenyl-2,2-diylbis(10-methylacridinium), which exhibits electrochromic response with ON/OFF switching of FL during the reversible interconversion with the di(spiroacridan)-type electron donor. Slight structural alteration under the concept of MFMS (maximum function on the minimum skeleton) endowed the dyrex system with metal-binding or chiroptical properties, which could be modified by the redox reactions. Some of the di(spiroacridan) derivatives generated from bis(10-methylacridinium)s have extreme structural parameters, such as the greatest C-C bond length ever reported.
• New Insights into the Hexaphenylethane Riddle: Formation of an α, o -Dimer

  Yasuto Uchimura, Takashi Takeda, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki

  Angewandte Chemie 127 13 4082 - 4085 Wiley-Blackwell 2015年02月 [査読有り][通常論文]
  
• Inside Back Cover: New Insights into the Hexaphenylethane Riddle: Formation of an α, o -Dimer (Angew. Chem. Int. Ed. 13/2015)

  Yasuto Uchimura, Takashi Takeda, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki

  Angewandte Chemie International Edition 54 13 4125 - 4125 Wiley-Blackwell 2015年02月 [査読有り][通常論文]
  
• Two-way chromic interconversion of the 2,2′-biphenol-6,6′-diyl dication with 5H,10H-dioxapyrene or 9H,10H-4,5-dihydroxyphenanthrene

  Yuto Sakano, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki

  Chemical Communications 51 76 14303 - 14305 2015年 [査読無し][通常論文]
   

  © 2015 The Royal Society of Chemistry. Two-proton or two-electron transfer of the title biphenolic dication proceeds nearly simultaneously to induce 2,6′/2′,6- or 6,6′-bond formation to give dioxapyrene or dihydrophenanthrene derivatives, respectively, with vivid changes in color (halochromism and electrochromism).
• STEREOSELECTIVE SYNTHESIS OF THE A-RING OF ARMATOL A FROM A BROMO-SUBSTITUTED CHIRAL BUILDING BLOCK BASED ON IRELAND-CLAISEN REARRANGEMENT AND RING-CLOSING OLEFIN METATHESIS

  Yuta Hirose, Kenshu Fujiwara, Takafumi Saito, Ryo Katoono, Takanori Suzuki

  HETEROCYCLES 91 1 76 - 103 2015年01月 [査読有り][通常論文]
   

  The stereoselective synthesis of the A-ring of armatol A, a natural polycyclic ether triterpene from the red alga Chondria armata, was achieved in a non-biomimetic way. The synthesis employed Ireland-Claisen rearrangement of an ester, prepared from a bromo-substituted chiral building block, for the construction of C6 and C7 stereocenters and a relay ring-closing olefin metathesis for the seven-membered ring formation.
• THREE-WAY OUTPUT MOLECULAR RESPONSE SYSTEM BASED ON TETRAKIS(3,4-DIALKOXYPHENYL)-3,4-DIHYDRO[5]HELICENES: PERTURBATION OF PROPERTIES BY LONG ALKYL CHAINS

  Yusuke Ishigaki, Satoshige Yoshida, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Fukushima, Takanori Suzuki

  HETEROCYCLES 90 1 126 - 135 2015年01月 [査読有り][通常論文]
   

  Starting from (S)-dimethyl 1,1'-binaphthyl-2,2'-dicarboxylate, optically pure (P)-3,3,4,4-tetrakis(3,4-dialkoxyphenyl)-3,4-dihydro[5]helicenes (P)-1 were prepared via bis(diarylhyclroxymethyl)binaphthyl and/or tetraaryldinaphthodihydroxepin as key intermediates. Upon electrochemical oxidation to the corresponding (S)-1,1'-binaphthyl-2,2'-diylbis(diarylcarbenium)s (S)-2(2+), three kinds of spectral changes (UV-Vis, circular dichroism, fluorescence) were successfully observed. Compared to the methoxy compound, the octyloxy and hexadecyloxy derivatives exhibit a redshifted emission maxima in the dihydro[5]helicenes. The long alkyl chains induce step-by-step two-electron reduction of the binaphthyldiyl(dicarbenium)s whereas the dication with methoxy groups exhibits one-wave two-electron process.
• Controllability of dynamic double helices: quantitative analysis of the inversion of a screw-sense preference upon complexation

  Ryo Katoono, Shunsuke Kawai, Kenshu Fujiwara, Takanori Suzuki

  CHEMICAL SCIENCE 6 11 6592 - 6600 2015年 [査読有り][通常論文]
   

  We describe a quantitative analysis of the complexation-induced inversion of a screw-sense preference based on a conformationally dynamic double-helix structure in a macrocycle. The macrocycle is composed of two twisting units (terephthalamide), which are spaced by two strands (1,3-bis(phenylethynyl)benzene), and is designed to generate a double-helix structure through twisting about a C-2 axis in a conrotatory manner. The attachment of chiral auxiliaries to the twisting units induces a helical preference for a particular sense of (M)- or (P)-helicity through the intramolecular transmission of chirality to dynamic double helices. The twisting unit can also act as a binding site for capturing a guest molecule, and, in a complexed state, the preferred screw sense of the dynamic double-helix structure is reversed to exhibit the contrary preference. We quantitatively monitored the complexation-induced inversion of the screw-sense preference using H-1 NMR spectroscopy, which enabled us to observe independently two species with (M)- or (P)-helicity in both the absence and presence of a guest molecule. Inversion of the screw-sense preference was induced upon complexation with an achiral guest as well as a chiral guest.
• BIS(DIARYLETHENYL)THIOPHENE, -BITHIOPHENE, AND -TERTHIOPHENE: A NEW SERIES OF VIOLENE-CYANINE HYBRID-TYPE ELECTRON DONORS

  Yusuke Ishigaki, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki

  HETEROCYCLES 90 1 136 - 143 2015年01月 [査読有り][通常論文]
   

  The title fluorescent (oligo)thiophenes 1-3 were designed as new violene/cyanine-hybrid-type electron donors, which have two 4-methoxyphenyl groups each on the two cyanine parts. Voltammetric analyses showed that they all undergo reversible two-stage one-electron oxidation. The intramolecular short S(thiophene) -- C-ipso(Ar) contacts were commonly present in their X-ray structures, and the coplanarily extended geometries are suitable for pi-delocalization. Electrochemical oxidation of 1-3 caused continuous changes in their UV-Vis-NIR and fluorescence spectra although the oxidized species are too labile to be isolated.
• THREE-WAY OUTPUT MOLECULAR RESPONSE SYSTEM BASED ON TETRAKIS(3,4-DIALKOXYPHENYL)-3,4-DIHYDRO[5]HELICENES: PERTURBATION OF PROPERTIES BY LONG ALKYL CHAINS

  Yusuke Ishigaki, Satoshige Yoshida, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Fukushima, Takanori Suzuki

  HETEROCYCLES 90 1 126 - 135 2015年01月 [査読有り][通常論文]
   

  Starting from (S)-dimethyl 1,1'-binaphthyl-2,2'-dicarboxylate, optically pure (P)-3,3,4,4-tetrakis(3,4-dialkoxyphenyl)-3,4-dihydro[5]helicenes (P)-1 were prepared via bis(diarylhyclroxymethyl)binaphthyl and/or tetraaryldinaphthodihydroxepin as key intermediates. Upon electrochemical oxidation to the corresponding (S)-1,1'-binaphthyl-2,2'-diylbis(diarylcarbenium)s (S)-2(2+), three kinds of spectral changes (UV-Vis, circular dichroism, fluorescence) were successfully observed. Compared to the methoxy compound, the octyloxy and hexadecyloxy derivatives exhibit a redshifted emission maxima in the dihydro[5]helicenes. The long alkyl chains induce step-by-step two-electron reduction of the binaphthyldiyl(dicarbenium)s whereas the dication with methoxy groups exhibits one-wave two-electron process.
• STEREOSELECTIVE SYNTHESIS OF THE A-RING OF ARMATOL A FROM A BROMO-SUBSTITUTED CHIRAL BUILDING BLOCK BASED ON IRELAND-CLAISEN REARRANGEMENT AND RING-CLOSING OLEFIN METATHESIS

  Yuta Hirose, Kenshu Fujiwara, Takafumi Saito, Ryo Katoono, Takanori Suzuki

  HETEROCYCLES 91 1 76 - 103 2015年01月 [査読有り][通常論文]
   

  The stereoselective synthesis of the A-ring of armatol A, a natural polycyclic ether triterpene from the red alga Chondria armata, was achieved in a non-biomimetic way. The synthesis employed Ireland-Claisen rearrangement of an ester, prepared from a bromo-substituted chiral building block, for the construction of C6 and C7 stereocenters and a relay ring-closing olefin metathesis for the seven-membered ring formation.
• Controllability of dynamic double helices: quantitative analysis of the inversion of a screw-sense preference upon complexation

  Ryo Katoono, Shunsuke Kawai, Kenshu Fujiwara, Takanori Suzuki

  CHEMICAL SCIENCE 6 11 6592 - 6600 2015年 [査読有り][通常論文]
   

  We describe a quantitative analysis of the complexation-induced inversion of a screw-sense preference based on a conformationally dynamic double-helix structure in a macrocycle. The macrocycle is composed of two twisting units (terephthalamide), which are spaced by two strands (1,3-bis(phenylethynyl)benzene), and is designed to generate a double-helix structure through twisting about a C-2 axis in a conrotatory manner. The attachment of chiral auxiliaries to the twisting units induces a helical preference for a particular sense of (M)- or (P)-helicity through the intramolecular transmission of chirality to dynamic double helices. The twisting unit can also act as a binding site for capturing a guest molecule, and, in a complexed state, the preferred screw sense of the dynamic double-helix structure is reversed to exhibit the contrary preference. We quantitatively monitored the complexation-induced inversion of the screw-sense preference using H-1 NMR spectroscopy, which enabled us to observe independently two species with (M)- or (P)-helicity in both the absence and presence of a guest molecule. Inversion of the screw-sense preference was induced upon complexation with an achiral guest as well as a chiral guest.
• BIS(DIARYLETHENYL)THIOPHENE, -BITHIOPHENE, AND -TERTHIOPHENE: A NEW SERIES OF VIOLENE-CYANINE HYBRID-TYPE ELECTRON DONORS

  Yusuke Ishigaki, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki

  HETEROCYCLES 90 1 136 - 143 2015年01月 [査読有り][通常論文]
   

  The title fluorescent (oligo)thiophenes 1-3 were designed as new violene/cyanine-hybrid-type electron donors, which have two 4-methoxyphenyl groups each on the two cyanine parts. Voltammetric analyses showed that they all undergo reversible two-stage one-electron oxidation. The intramolecular short S(thiophene) -- C-ipso(Ar) contacts were commonly present in their X-ray structures, and the coplanarily extended geometries are suitable for pi-delocalization. Electrochemical oxidation of 1-3 caused continuous changes in their UV-Vis-NIR and fluorescence spectra although the oxidized species are too labile to be isolated.
• Controlled Dynamic Helicity of a Folded Macrocycle Based on a Bisterephthalamide with a Twofold Z-Shaped Structure

  Ryo Katoono, Keiichi Kusaka, Kenshu Fujiwara, Takanori Suzuki

  CHEMISTRY-AN ASIAN JOURNAL 9 11 3182 - 3187 2014年11月 [査読無し][通常論文]
   

  Dynamic helicity in a folded macrocycle and control of the helical preference are described. We designed macrocycle 1 with a dual mode of folding through the integration of two flexible units that are arranged twice to form a cyclic structure. As a folding unit, we used a terephthalamide skeleton and a Z-shaped hydrocarbon: the former acted as a control unit to induce a preference of a particular sense of dynamic helicity and the latter was just a spacer. A terephthalamide unit provided a binding site for capturing a ditopic hydrogen-bonding guest when it adopted helically folded syn forms (M/P). Thus, only the terephthalamide unit controlled the helical sense of dynamic helicity in a folded macrocycle through the supramolecular transmission of chirality upon complexation with a chiral ditopic guest. In addition, chirality on a host could also contribute to the control of the helical preference in a folded macrocycle, which led to exceptionally enhanced chiroptical signals.
• A Foldable Cyclic Oligomer: Chiroptical Modulation through Molecular Folding upon Complexation and a Change in Temperature

  Ryo Katoono, Yuki Tanaka, Kenshu Fujiwara, Takanori Suzuki

  JOURNAL OF ORGANIC CHEMISTRY 79 21 10218 - 10225 2014年11月 [査読有り][通常論文]
   

  A foldable cyclic oligomer 1 consisting of three terephthalamide units spaced with a 3-fold o-phenylene unit presented a dynamic pair of enantiomeric forms through molecular folding, to which the external chirality on a ditopic guest [(S,S)-2 or (R,R)-2] was supramolecularly transferred to prefer a particular sense of dynamic helicity [(M,M)-/(P,P)-1 and (M,M,P)-/(P,P,M)-1]. In the macrocycle, the terephthalamide units acted as exotopic binding sites to fold into helical forms upon complexation. The internal chirality associated with a host [(R,R,R,R,R,R)-1b] had no preference in a helical sense in the absence of a guest. Instead, the internal chirality was responsible for the signal modulation that it was cooperatively or competitively transferred in response to the external chirality on a guest (S,S)-2 or (R,R)-2. During the diastereomeric complexation, a particular sense of dynamic helicity was favored due to cooperative transmission of chirality when the helical preference was matched between the host and guest. Alternatively, the host complexed with an antipodal guest underwent a drastic change in conformation upon a change in temperature.
• ChemInform Abstract: Hexaphenylethanes with an Ultralong C-C Bond: Expandability of the C-C Bond in Highly Strained Tetraarylpyracenes

  Takashi Takeda, Yasuto Uchimura, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki

  ChemInform 45 30 no - no 2014年07月10日 [査読有り][通常論文]
  
• Wurster's Blue-type Cation Radicals Framed in a 5,10-Dihydrobenzo[a]indolo[2,3-c]carbazole (BIC) Skeleton: Dual Electrochromism with Drastic Changes in UV/Vis/NIR and Fluorescence

  Takanori Suzuki, Yuto Sakano, Yusuke Tokimizu, Youhei Miura, Ryo Katoono, Kenshu Fujiwara, Naoki Yoshioka, Nobutaka Fujii, Hiroaki Ohno

  CHEMISTRY-AN ASIAN JOURNAL 9 7 1841 - 1846 2014年07月 [査読有り][通常論文]
   

  Electron-donating dihydrobenzindolocarbazoles (BICs) 1a-c, which adopt planar disk-shaped geometries, were prepared by gold(I)-catalyzed cyclization as a key step. Due to the presence of a 1,4-phenylenediamine (PD) moiety in the framework, they undergo reversible one-electron oxidation to the corresponding Wurster's Blue (WB)-type species that exhibits NIR absorptions up to lambda=1200 nm. In the case of the N,N'-dimethyl derivative, cation radical 1c(+center dot) is stable enough to be isolated as a salt and Xray analysis indicated paraquinoid-type bond alternation in the WB core unit, whereas the bond lengths in the peripheral benzene rings are identical to those in the neutral donor. Upon electrochemical interconversion, the redox pairs of 1a-c and 1a-c(+center dot) exhibited an electrochromic response in the UV/Vis/NIR region, which was accompanied by a drastic change in the fluorescence spectrum because only neutral donors 1a-c are highly emissive (Phi(F): 0.7-0.8).
• Preparation, Redox Properties, and X-ray Structures of Electrochromic 11,11,12,12-Tetraarylanthraquinodimethane and Its Bianthraquinodimethane Analogue: Drastic Geometrical Changes upon Interconversion with Dicationic Dyes

  Yuto Sakano, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki

  CHEMISTRY LETTERS 43 7 1143 - 1145 2014年07月 [査読有り][通常論文]
   

  Tetrakis(4-methoxyphenyl)anthraquinodimethane 1(b) with a bent geometry undergoes reversible redox interconversion with twisted dication 1(t)(2+) exhibiting a vivid change in color (electrochromism) accompanied by a drastic structural change. Electrochemical oxidation of bianthraquinodimethane 2(b) with a doubly bent structure to bianthrylidene-type twisted dication 2(t)(2+) proceeded smoothly, whereas the reverse conversion was less effective because 2(t)(2 center dot) generated upon reduction of 2(t)(2+) is a long-lived species to undergo side reactions.
• Electrochiroptical Response in Aqueous Media: 9,10-Dihydrophenanthrene-9,10-diyl Dications with Michlar's Hydrol Blue Chromophores Attached with Oligoethylene Glycol Units

  Takanori Suzuki, Keisuke Hanada, Ryo Katoono, Yusuke Ishigaki, Sho Higasa, Hiroki Higuchi, Hirotsugu Kikuchi, Kenshu Fujiwara, Hidetoshi Yamada, Takanori Fukushima

  CHEMISTRY LETTERS 43 7 982 - 984 2014年07月 [査読有り][通常論文]
   

  Upon electrochemical oxidation of configurationally stable biphenyl-based electron donors (R-ax)-1a and -1b to butane-1,4-diyl dications (M)-2a(2+) and -2b(2+), drastic changes were induced not only in UV-vis but also in CD spectra. Because of the hydrophilic oligoethylene glycol units on the amino nitrogens, (R-ax)-1b and (M)-2b(2+) are soluble in water, thus realizing the electrochiroptical behavior not only in organic solvents but also in aqueous media.
• Oxidative Protonolysis of the Expanded Central C-C Bond in a Di(spiroacridan)-type Hexaphenylethane Derivative Accompanied by UV- vis, FL, and CD Spectral Changes

  Takanori Suzuki, Yusuke Kuroda, Kazuhisa Wada, Yuto Sakano, Ryo Katoono, Kenshu Fujiwara, Fumitoshi Kakiuchi, Takanori Fukushima

  CHEMISTRY LETTERS 43 6 887 - 889 2014年06月 [査読有り][通常論文]
   

  Upon electrochemical oxidation of configurationally stable (M)-4,5-dimethyl-9,10-dihydrophenanthrene attached with two spiroacridan units at the C9 and C10 positions [(M)-1c], a three-way-output response by UV vis, FL, and CD spectra was realized via clean conversion to the corresponding bond-dissociated dication (R-ax)-2c(2+). Similar gradual changes were induced upon standing of an aerated MeCN solution of (M)-1c after the addition of CF3CO2H because the elongated C9 C10 bond was also cleaved by oxidative protonolysis to give (R-ax)-2c(2+).
• Inside Back Cover: Wurster’s Blue-type Cation Radicals Framed in a 5,10-Dihydrobenzo[ a ]indolo[2,3- c ]carbazole (BIC) Skeleton: Dual Electrochromism with Drastic Changes in UV/Vis/NIR and Fluorescence (Chem. Asian J. 7/2014)

  Takanori Suzuki, Yuto Sakano, Yusuke Tokimizu, Youhei Miura, Ryo Katoono, Kenshu Fujiwara, Naoki Yoshioka, Nobutaka Fujii, Hiroaki Ohno

  Chem. Asian J. 9 7 1967 - 1967 Wiley-Blackwell 2014年06月 [査読有り][通常論文]
  
• Cyanoazulene-based Multistage Redox Systems Prepared from Vinylcyclopropanecarbonitrile and Cyclopentenone via Divinylcyclopropane-rearrangement Approach

  Keiji Tanino, Takumasa Yamada, Fumihiko Yoshimura, Takanori Suzuki

  CHEMISTRY LETTERS 43 5 607 - 609 2014年05月 [査読有り][通常論文]
   

  A series of 4-cyanoazulene derivatives 1-5 were synthesized from 4-cyanohexahydroazulen-l-one, which was efficiently obtained by the annulation of the seven-membered ring on the cyclopentenone skeleton via the divinylcyclopropane rearrangement. This synthetic protocol is also effective in preparing 1,1'-bi(4-cyanoazulene) (6) and its p-phenylene-extended derivative 7, which undergo multistage redox reactions exhibiting electrochemical amphotericity.
• Electrochromic and unique chiroptical properties of helically deformed tetra-arylquinodimethanes generated from lesshindered dicationic precursors upon reduction

  Takanori Suzuki, Yuto Sakano, Tomohiro Iwai, Shinichi Iwashita, Youhei Miura, Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara, Yasushi Tsuji, Takanori Fukushima

  PURE AND APPLIED CHEMISTRY 86 4 507 - 516 2014年04月 [査読有り][通常論文]
   

  Electron-donating 1,1,4,4-tetraarylbutadiene is a representative electrochromic dye, and the same chromophore can be found in 9,10-bis(diarylmethylene)-9,10-dihydrophenanthrene (dibenzo-oQD) albeit in a fixed s-cis geometry. Unlike thermodynamically unstable 7,7,8,8-tetraaryl-o-quinodimethane, spontaneous electrocyclization is prohibited by dibenzo-annulation. Several derivatives of dibenzo-oQD were successfully generated despite highly strained geometry caused by steric hindrance between the bulky diarylmethylene units. Their precursors are phenanthrene-9,10-diyl bis(diarylmethylium) dyes (PDM2+) stabilized by four electron-donating alkoxy groups. The redox pairs of dibenzo-oQD/PDM2+ exhibit vivid change in color upon redox interconversion (electrochromism). Both dibenzo-oQD and PDM2+ adopt a helical conformation, whose configuration is unstable. When a chiral alkoxy substituent is attached on each of the aryl groups, the point chirality is successfully transmitted to helicity of PDM2+. Resulting diastereomeric biasing is the key for dibenzo-oQD/PDM2+ to exhibit the two-way-output response (e.g., UV-vis and CD). In addition, much more strained quinodimethane derivatives, 1,2-bis(diarylmethylene) acenaphthene and 1,16-diaryldibenzo[b, n] perylene, were also generated from the dicationic precursors, demonstrating that the reductive transformation can serve as a useful protocol to generate severely deformed pi-conjugated systems.
• Total Synthesis of Pectenotoxin-2

  Kenshu Fujiwara, Yuki Suzuki, Nao Koseki, Yu-ichi Aki, Yuta Kikuchi, Shun-ichi Murata, Fuyuki Yamamoto, Mariko Kawamura, Toshio Norikura, Hajime Matsue, Akio Murai, Ryo Katoono, Hidetoshi Kawai, Takanori Suzuki

  ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 53 3 780 - 784 2014年01月 [査読有り][通常論文]
   

  Pectenotoxin-2 (PTX2) is a shellfish toxin and has a non-anomeric spiroacetal, which is not stabilized by an anomeric effect. The selective construction of the non-anomeric spiroacetal has been a major problem in the synthesis of PTX2. Described herein is the stereoselective total synthesis of PTX2 via the isomerization of anomeric spiroacetal pectenotoxin-2b (PTX2b). The synthesis of PTX2b was achieved by a simple process including sulfone-mediated assembly of spirocyclic and bicyclic acetals and subsequent macrocyclization by ring-closing olefin metathesis. Finally, the selective construction of PTX2 was accomplished by the early termination of a dynamic transition process to equilibrium in the acid-catalyzed isomerization of anomeric PTX2b. [6,6]-Spiroacetal pectenotoxin-2c (PTX2c) was also synthesized from PTX2b. The cytotoxicity assay of the synthetic compounds against HepG2 and Caco2 cancer cells showed a potency of the order: PTX2 >> PTX2b > PTX2c.
• Complexation-induced inversion of helicity by an organic guest in a dynamic molecular propeller based on a tristerephthalamide host with a two-layer structure

  Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki

  CHEMICAL COMMUNICATIONS 50 41 5438 - 5440 2014年 [査読有り][通常論文]
   

  A tristerephthalamide host exhibited two helical geometries with (M)- and (P)- helicity, respectively, in terms of the twisting direction of a two-layer structure, and the helical preference switched upon complexation with a ditopic guest. In both uncomplexed and complexed states, the intramolecular transmission of chirality was responsible for the control of helicity.
• Expandability of Ultralong C-C Bonds: Largely Different C-1-C-2 Bond Lengths Determined by Low-temperature X-ray Structural Analyses on Pseudopolymorphs of 1,1-Bis(4-fluorophenyl)-2,2-bis(4-methoxyphenyl)pyracene

  Takanori Suzuki, Yasuto Uchimura, Fumika Nagasawa, Takashi Takeda, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Kei Murakoshi, Takanori Fukushima, Aiichiro Nagaki, Jun-ichi Yoshida

  CHEMISTRY LETTERS 43 1 86 - 88 2014年01月 [査読有り][通常論文]
   

  Low-temperature X-ray analyses on several pseudopolymorphs (solvate crystals) revealed that the C-1-C-2 bond length of the highly congested title molecule can adopt quite different values [1.700(6)-1.739(6)angstrom]. Such an unusual observation indicates that the ultralong covalent bond is endowed with "expandability," thus the prestrained bond can be elongated or shortened very easily accompanied by only a minute change in energy, which can be compensated by intermolecular perturbation in the crystal.
• Chiroptical molecular propellers based on hexakis(phenylethynyl)benzene through the complexation-induced intramolecular transmission of local point chirality

  Ryo Katoono, Keiichi Kusaka, Shunsuke Kawai, Yuki Tanaka, Keisuke Hanada, Tatsuo Nehira, Kenshu Fujiwara, Takanori Suzuki

  ORGANIC & BIOMOLECULAR CHEMISTRY 12 47 9532 - 9538 2014年 [査読無し][通常論文]
   

  We designed hexakis(phenylethynyl) benzene derivatives with a tertiary amide group on each blade to achieve a helically biased propeller arrangement through the complexation-induced intramolecular transmission of point chirality. A hydrogen-bonding ditopic guest was captured at two amide groups, and thus could pair two neighboring blades to form a supramolecular cyclic structure, in which an auxiliary chiral group associated with a blade acted as a chiral handle to control the helical bias, while the chiral auxiliary did not exert any helical influence on the dynamic helicity in the absence of a guest due to the high flexibility of each blade.
• Preparation and structure of acenaphthylene-1,2-diyldi(9-acridine) derivatives with a long C=C bond

  Takashi Takeda, Yasuto Uchimura, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki

  CHEMICAL COMMUNICATIONS 50 30 3924 - 3927 2014年 [査読有り][通常論文]
   

  Due to purely steric effects of acridine units, acenaphthylene-1,2-diyldi(9-acridine) has a long C=C bond [1.3789(19) angstrom] while maintaining its sp(2) hybridized nature and bond order.
• CHIRAL MEMORY UNITS BASED ON DYNAMIC REDOX SYSTEMS WITH A DIBENZOXEPINONE SKELETON: DRASTIC CHANGE IN RACEMIZATION BARRIER AND ELECTROCHEMICAL BISTABILITY

  Kazuhisa Wada, Yuna Chiba, Takashi Takeda, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki

  HETEROCYCLES 88 2 945 - 952 2014年01月 [査読有り][通常論文]
   

  The configuration of helical dicationic dyes 2(2+) with a dihydrodibenzoxepinone unit is stable, whereas the corresponding neutral electron donors 1 with a tetrahydrophenanthroxepinone skeleton easily undergo ring-flip. Thanks to their electrochemical bistability, electron exchange between 1 and 2(2+) is prohibited. Thus, the above electrochromic pairs 1/2(2+) can serve as new members of less well-explored redox-based chiral-memory units.
• A C3-symmetric chiroptical molecular propeller based on hexakis(phenylethynyl)benzene with a threefold terephthalamide: Stereospecific propeller generation through the cooperative transmission of point chiralities on the host and guest upon complexation

  Ryo Katoono, Hidetoshi Kawai, Masakazu Ohkita, Kenshu Fujiwara, Takanori Suzuki

  Chemical Communications 49 88 10352 - 10354 2013年11月14日 [査読有り][通常論文]
   

  Propeller-shaped dynamic helicity was generated in a hexakis(phenylethynyl) benzene framework that preferred a particular sense to afford a strong CD signal, which was realized by the cooperative transmission of point chiralities upon complexation with a chiral guest through a threefold binding site presented by a syn-formed terephthalamide. © 2013 The Royal Society of Chemistry.
• Total Synthesis of Pectenotoxin-2

  Kenshu Fujiwara, Yuki Suzuki, Nao Koseki, Yu-ichi Aki, Yuta Kikuchi, Shun-ichi Murata, Fuyuki Yamamoto, Mariko Kawamura, Toshio Norikura, Hajime Matsue, Akio Murai, Ryo Katoono, Hidetoshi Kawai, Takanori Suzuki

  Angew. Chem. 126 3 799 - 803 2013年11月 [査読有り][通常論文]
  
• Time-integrated One-pot Synthesis, X-ray Structure, and Redox Properties of Electrochromic 1,3-Diarylisobenzofurans

  Toshiyuki Hamura, Ryosuke Nakayama, Keisuke Hanada, Yuto Sakano, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki

  CHEMISTRY LETTERS 42 10 1244 - 1246 2013年10月 [査読有り][通常論文]
   

  1,3-Bis[4-(dimethylamino)phenyl]isobenzofuran (1a) and a derivative were efficiently prepared through a sequence of reactions in a single batch reactor (time integration). The o-quinodimethane-type pi-conjugation in 1a was confirmed by bond alternation determined by a low-temperature X-ray analysis. Brightly colored heterocycle 1a undergoes reversible two-stage one-electron oxidation, and electrolysis of 1a induces a vivid change in UV-vis-NIR. absorptions exhibiting several isosbestic points (electrochromism).
• Geometrical Remote Steric Effects in 4,5-Disubstituted-9,10-dihydrophenanthrenes: Expansion of Prestrained C-9-C-10 Bond in Di(spiroacridan) Derivatives

  Kazuhisa Wada, Takashi Takeda, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki

  CHEMISTRY LETTERS 42 10 1194 - 1196 2013年10月 [査読有り][通常論文]
   

  By attaching bulky substituents at the bay region of di(spiroacridan)-substituted dihydrophenanthrene la, the prestrained C-9-C-10 bond in the dihydrophenanthrene (DHP) skeleton of le le is expanded from 1.634(2) to 1.649(3)-1.652(6)angstrom, which demonstrates the bond expansion through remote steric effects. Twisting deformation of the DHP skeleton is the key to transfer the steric bulkiness from the C-4/C-5 positions to cause the additional strain in the C-9-C-10 bond.
• Preparation, Properties, and X-ray Structures of Bis(10-methyl-9-methyleneacridan)-type Electron Donors with a Thiophene, Bithiophene, or Terthiophene Skeleton: Redox Switching of Thiophene-Thienoquinoid Structure Accompanied by UV-vis-NIR Electrochromic Response

  Takanori Suzuki, Yuulci Hoshiyama, Kazuhisa Wada, Yusuke Ishigaki, Youhei Miura, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Fukushima

  CHEMISTRY LETTERS 42 9 1004 - 1006 2013年09月 [査読有り][通常論文]
   

  The newly designed title dyes 1-3 have a thiophene-type pi-skeleton, to which two methyleneacridan subunits are attached as electron-donating end groups. They undergo reversible one-wave 2e-oxidation to the corresponding dications containing a thienoquinoid moiety. The redox and spectral properties can be modified by changing the pi-skeleton, and bithiophene 2 and terthiophene 3 can serve as new entries of UV-vis-NIR. electrochromic materials.
• 5,10-Dihydrobenzo[a]indolo[2,3-c]carbazole: A Highly Fluorescent Disk-shaped Electron Donor Exhibiting Dual UV-vis-NIR and Fluorescence Spectral Changes upon Electrolysis

  Takanori Suzuki, Yusuke Toldmizu, Yuto Sakano, Ryo Katoono, Kenshu Fujiwara, Saori Naoe, Nobutaka Fujii, Hiroaki Ohno

  CHEMISTRY LETTERS 42 9 1001 - 1003 2013年09月 [査読有り][通常論文]
   

  Through gold(I)-catalyzed cascade cyclization as a key step, the title electron donor was prepared, which adopts a planar geometry, as confirmed by an X-ray analysis. Due to 1,4-phenylenediamine moiety incorporated in the framework, it undergoes reversible one-electron oxidation. Upon electrolysis, it exhibited an electrochromic response in the UV-vis-NIR region, which was accompanied by a drastic change in the fluorescence spectrum since only the neutral donor is highly fluorescent.
• Hexaphenylethanes with an Ultra long C-C Bond: Expandability of the C-C Bond in Highly Strained Tetraarylpyracenes

  Takashi Takeda, Yasuto Uchimura, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki

  CHEMISTRY LETTERS 42 9 954 - 962 2013年09月 [査読有り][通常論文]
   

  Over the past few decades, many studies have been conducted on ultralong C-C bonds (bond length greater than 1.7 angstrom). This highlight review discusses the molecular design of ultralong C-C bonds and their bonding properties, especially their "expandability." In particular, the ultralong C-C bonds in tetraarylpyracene derivatives can change in length by adopting a slightly different conformation in the crystalline state. This expandability of ultralong C-C bonds could be due to the smaller decrease in bond energy at a longer interatomic distance (>1.7 angstrom). This interesting property can be applied to stimulus-responsive materials, as illustrated in the thermochromism of a bis(methylacridan)-substituted pyracene crystal, since the thermally induced change in bond-length modifies the HOMO-LUMO gap.
• A stereoselective method for the construction of the C8′-O-C6″ ether of nigricanoside-A: Synthesis of simple models for the C20 lipid chain/galactosyl glycerol segment

  Naoto Kinashi, Kenshu Fujiwara, Takayuki Tsunoda, Ryo Katoono, Hidetoshi Kawai, Takanori Suzuki

  Tetrahedron Letters 54 34 4564 - 4567 Elsevier {BV} 2013年08月 [査読有り][通常論文]
   

  A method for the stereoselective construction of the C8′-O-C6″ ether of nigricanoside-A, an antimitotic natural product from the green alga Avrainvillea nigricans, has been developed based on chirality-transferring Ireland-Claisen rearrangement. The method was successfully applied to the synthesis of simple models for the C20 lipid chain/galactosyl glycerol segment of the natural product. © 2013 Elsevier Ltd. All rights reserved.
• Redox switching of conjugation length using 9,9,10,10-tetraaryl-9,10- dihydrophenanthrene as an ON/OFF unit: Preparation, x-ray structure, and redox properties of perfluorobiphenyl derivative and its SnAr reactions to φextended analogues

  Takanori Suzuki, Hitomi Tamaoki, Ryo Katoono, Kenshu Fujiwara, Junji Ichikawa, Takanori Fukushima

  Chemistry Letters 42 7 703 - 705 Chemical Society of Japan 2013年07月 [査読有り][通常論文]
   

  Octafluorobiphenyl-2,2-diylbis(diarylmethylium) dye 2a2+ prepared from 1,2-dibromotetrafluorobenzene is interconvertible with colorless dihydrophenanthrene donor 1a. By the SNAr reactions of 1a with acetylides,φ-extended analogues 1b and 1c were obtained. Their electrochromic behavior is accompanied by a drastic absorption change not only in the visible but also UV region, because the torsion angle of the biaryl unit is modified upon redox reactions. © 2013 The Chemical Society of Japan.
• Oxidative Conversion of Tetraaryldihydrodibenzothiepins into Elemental Sulfur and Stable Cationic Dyes Accompanied by Dual UV-vis and CD Spectral Changes

  Takanori Suzuki, Takuma Kuroda, Hitomi Tamaoki, Sho Higasa, Ryo Katoono, Kenshu Fujiwara, Takanori Fukushima, Hidetoshi Yamada

  CHEMISTRY LETTERS 42 7 706 - 708 2013年07月 [査読有り][通常論文]
   

  Upon oxidation of the title heterocycles with dimethylamino groups, elemental sulfur is extruded to form dicationic dyes, which regenerate the heterocycles by the reaction with Na2S. The electrolysis of the heterocycles induces a drastic change in UV-vis spectrum exhibiting several isosbestic points. The bay-region substituents enhance configurational stability, so the optically pure heterocycle can be obtained in terms of helicity of one-handedness, and its chromism is accompanied by a large chiroptical response as detected by CD spectroscopy.
• Hydrindacene-based acetylenic macrocycles with horizontally and vertically ordered functionality arrays

  Hidetoshi Kawai, Tatsuya Utamura, Erina Motoi, Tomoko Takahashi, Hiroyoshi Sugino, Manabu Tamura, Masakazu Ohkita, Kenshu Fujiwara, Takao Saito, Takashi Tsuji, Takanori Suzuki

  Chemistry - A European Journal 19 14 4513 - 4524 2013年04月02日 [査読無し][通常論文]
   

  The macrocyclization of 2,6-diethynyl hydrindacenes (1) with functional groups at mutually perpendicular positions results in the formation of novel macrocycles which, as a result of the hindered rotation of the hydrindacene units, possess directionally persistent peripheral functionalities. The two hydrindacene units in the dimer macrocycle (2) have been shown to interact electronically through their respective butadiyne moieties, whereas the trimer macrocycle (3) demonstrates a moderate degree of geometrical flexibility as a result of the five-membered hydrindacene rings. In addition, these trimer macrocycles contain a central cavity suitably sized for the inclusion of various solvent molecules. These new macrocycles can be further modified by introducing π-conjugated side groups, such as styryl and thienyl groups, as well as by attaching a variety of peripheral ester groups. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
• An Ireland–Claisen rearrangement/RCM based approach for the construction of the EF-ring of ciguatoxin 3C

  Keisuke Nogoshi, Daisuke Domon, Kenshu Fujiwara, Natsumi Kawamura, Ryo Katoono, Hidetoshi Kawai, Takanori Suzuki

  Tetrahedron Letters 54 7 676 - 680 Elsevier {BV} 2013年02月 [査読有り][通常論文]
   

  The EF-ring of ciguatoxin 3C, a marine toxin from the dinoflagellate Gambierdiscus toxicus, was stereoselectively synthesized by iterative use of a cyclic ether formation process based on chirality-transferring Ireland-Claisen rearrangement and ring-closing olefin metathesis. (c) 2012 Elsevier Ltd. All rights reserved.
• 7,7,8,8-tetraaryl-o-quinodimethane stabilized by dibenzo annulation: A helical π-electron system that exhibits electrochromic and unique chiroptical Properties

  Takanori Suzuki, Yuto Sakano, Tomohiro Iwai, Shinichi Iwashita, Youhei Miura, Ryo Katoono, Hidetoshi Kawai, Hidetoshi Kawai, Kenshu Fujiwara, Yasushi Tsuji, Takanori Fukushima

  Chemistry - A European Journal 19 1 117 - 123 Wiley-Blackwell 2013年01月 [査読有り][通常論文]
   

  When two benzene rings are fused to a tetraaryl-o-quinodimethane skeleton, sterically hindered helical molecules 1 acquire a high thermodynamic stability. Because the tetraarylbutadiene subunit contains electron-donating alkoxy groups, 1 undergo reversible two-electron oxidation to 22+, which can be isolated as deeply colored stable salts. Intramolecular transfer of the point chirality (e.g., sec-butyl) on the aryl groups to helicity induces a diastereomeric preference in dications 2 b2+ and 2 c2+, which represents an efficient method for enhancing circular-dichroism signals. Thus, those redox pairs can serve as new electrochiroptical response systems. X-ray analysis of dication 22+ revealed π-π stacking interaction of the diarylmethylium moieties, which is also present in solution. The stacking geometry is the key contributor to the chirosolvatochromic response. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
• A new variant of fused cyclic ether synthesis based on ireland-claisen rearrangement and RCM

  Daisuke Domon, Kenshu Fujiwara, Natsumi Kawamura, Ryo Katoono, Hidetoshi Kawai, Takanori Suzuki

  Natural Product Communications 8 7 929 - 934 2013年 [査読無し][通常論文]
   

  A new variant of fused cyclic ether synthesis based on Ireland-Claisen rearrangement and ring-closing olefin metathesis (RCM) was developed. The Ireland- Claisen rearrangement of a (Z)-3-alkoxyprop-2-en-1-yl glycolate ester having a cyclic ether on the oxygen at C3 of the (Z)-prop-2-en-1-yl group stereoselectively produced an anti-α,β-dialkoxyester, which was successfully transformed to a fused bicyclic ether via a reaction sequence including RCM.
• Stable neutral radicals based on the polyazaacene skeleton that exhibit high electrochemical amphotericity

  Youhei Miura, Hiroshi Chiba, Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara, Shuichi Suzuki, Keiji Okada, Takanori Suzuki

  TETRAHEDRON LETTERS 53 48 6561 - 6564 2012年11月 [査読有り][通常論文]
   

  Upon the one-electron reduction of N-methylquinoxalino[2,3-b]quinoxaliniums 2, neutral radicals 1 without any bulky protecting groups were generated and isolated as stable solids, which exhibit electric conductivity (sigma = 10(-7) 10(-9) S cm(-1)) as a single-component organic material due to high electrochemical amphotericity (Delta E = ca. 0.9 V). (C) 2012 Elsevier Ltd. All rights reserved.
• Effects of Axle-Core, Macrocycle, and Side-Station Structures on the Threading and Hydrolysis Processes of Imine-Bridged Rotaxanes

  Hiroyoshi Sugino, Hidetoshi Kawai, Takeshi Umehara, Kenshu Fujiwara, Takanori Suzuki

  CHEMISTRY-A EUROPEAN JOURNAL 18 43 13722 - 13732 2012年10月 [査読有り][通常論文]
   

  Imine-bridged rotaxanes are a new type of rotaxane in which the axle and macrocyclic ring are connected by imine bonds. We have previously reported that in imine-bridged rotaxane 5, the shuttling motion of the macrocycle could be controlled by changing the temperature. In this study, we investigated how the axle and macrocycle structures affect the construction of the imine-bridged rotaxane as well as the dynamic equilibrium between imine-bridged rotaxane 5 and [2]rotaxane 7 by using various combinations of axles (1?A,B), macrocycles (2?ae), and side-stations (XYL and TEG). In the threading process, the flexibility of the macrocycle and the substituent groups at the para position of the aniline moieties affect the preparation of the threaded imines. The size of the imine-bridging station and the macrocyclic tether affects the hydrolysis of the imine bonds under acidic conditions.
• P-27 ニグリカノシドAジメチルエステルの合成研究(ポスター発表の部)

  木梨 尚人, 藤原 憲秀, 上遠野 亮, 河合 英敏, 鈴木 孝紀

  天然有機化合物討論会講演要旨集 54 345 - 350 天然有機化合物討論会 2012年09月01日 

  Nigricanocide A dimethyl ester (1), which originated from the green alga Avrainvillea nigricans, is an antimitotic galactoglycerolipid. It is structurally characterized by two ether linkages between a galactosyl glycerol and a C20 oxylipin and between C16 and C20 oxylipins. While the planar structure of the lipid chains and the partial relative configuration of the galactosyl glycerol moiety have been determined, the full absolute stereochemistry is unclear. Therefore, we started a program for determining the full absolute stereostructure of nigricanoside A dimethyl ester by total synthesis. As a part of the program, stereoselective methods for constructing the ether linkages between the galactosyl glycerol and the C20 lipid chain and between the C20 and C16 lipid chains have been developed. Model compounds ((8'R)-4 and (8'S)-4) corresponding to the bottom half of 1, including the C20 lipid chain and the galactosyl glycerol, has also been synthesized. The ether linkage between the galactose and the C20 lipid chain was constructed stereoselectively by the chirality-transferring Ireland-Claisen rearrangement of a 1-substituted-2-bromoallyl alkoxyacetate, which consisted of an optically active 2-bromo-1-alken-3-ol and a 6-(carboxymethoxy)galactose derivative. The rearrangement products were converted to model conpounds (8'R)-4 and (8'S)-4 via a process including Julia olefination with sulfone 5, Mori's alkyne formation, and Lindlar hydrogenation. The ether linkage between lipid chains was stereoselectively synthesized by an Evans type aldol reaction under lithium enolate conditions. Details will be presented in the poster session.
• Total Synthesis of Thelephantin O, Vialinin A/Terrestrin A, and Terrestrins B–D

  Kenshu Fujiwara, Takuto Sato, Yusuke Sano, Toshio Norikura, Ryo Katoono, Takanori Suzuki, Hajime Matsue

  The Journal of Organic Chemistry 77 11 5161 - 5166 American Chemical Society ({ACS}) 2012年06月 [査読有り][通常論文]
   

  The first total synthesis of natural, unsymmetrical 2',3'-diacyloxy-p-terphenyls, thelephantin O (1) and terrestrins C and D (2 and 3, respectively), was achieved via a practical route which was also applicable to the synthesis of the symmetrical diesters vialinin A/terrestrin A. (4) and terrestrin B (5). Compounds 1-5 exhibited cytotoxicity against cancer cells (HepG2 and Caco2) with IC50 values of 13.6-26.7 mu mol/L.
• Nonadditive Substituent Effects on Expanding Prestrained C-C Bond in Crystal: X-ray Analyses on Unsymmetrically Substituted Tetraarylpyracenes Prepared by a Flow Microreactor Method

  Takanori Suzuki, Yasuto Uchimura, Yusuke Ishigaki, Takashi Takeda, Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara, Aiichiro Nagaki, Jun-ichi Yoshida

  CHEMISTRY LETTERS 41 5 541 - 543 2012年05月 [査読有り][通常論文]
   

  Based on space integration using a flow microreactor system, the title unsymmetrically substituted pyracenes with an extremely long C C bond [1.714(2)-1.739(4)angstrom] are readily accessible, whose structures demonstrate nonadditive substituent effects on expanding the polyarylated C-1-C-2 bond in crystal. The bond lengths rather exhibit correlation with the eclipsing degree of the C-sp3-C-sp3 bond, which is more affected by the intermolecular factors such as crystal packing.
• Molecular Gyroscope with a trans-Cyclohexane-1,4-diimine Rotor Unit: Isolation and Characterization of a Geometric Isomer as a Formal Intermediate of Hindered Rotation

  Hiroyoshi Sugino, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Suzuki

  CHEMISTRY LETTERS 41 1 79 - 81 2012年01月 [査読有り][通常論文]
   

  Condensation reactions of macrocyclic diamines 1 and cyclohexane-1,4-dicarbaldehydes 2 with the substituents at 1,4-positions gave a series of macrocage molecules that can be considered molecular gyroscopes. The gyro-rotational behavior of the cyclohexane rotor is largely affected by the degree of steric requirement of the substituents, and isolation of syn-isomer suggests stepwise motion in the macrocages attached with bulky substituents on the rotor.
• Induced preference for axial chirality in a triarylmethylium o,o-dimer upon complexation with natural γ-cyclodextrin: Strong ECD signaling and fixation of supramolecular chirality to molecular chirality

  Takanori Suzuki, Hitomi Tamaoki, Kazuhisa Wada, Ryo Katoono, Tatsuo Nehira, Hidetoshi Kawai, Hidetoshi Kawai, Kenshu Fujiwara

  Chemical Communications 48 22 2812 - 2814 Royal Society of Chemistry ({RSC}) 2012年 [査読有り][通常論文]
   

  The ratio of the easily interconverting rotational isomers of biphenyl-2,2′-diylbis[bis(4-dimethylaminophenyl)methylium] (R)/(S)-1a ²⁺ can be biased to prefer an R configuration upon 1:1 complexation with γ-cyclodextrin in water. Through the reaction with Na<inf>2</inf>S, the preference of 1a²⁺ at γ-CyD for an axial chirality of R can be fixed as the M-helicity of dihydrothiepin 2. © The Royal Society of Chemistry 2012.
• Chirality sensing based on changes in conformation of dynamic terephthalamide hosts: Propeller-, double-arm-, and figure-of-eight-shaped hosts

  Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Suzuki

  Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry 70 6 640 - 650 2012年 [査読無し][通常論文]
   

  This article describes the chirality sensing systems based on changes in conformation of dynamic terephthalamide hosts from a nonhelical form to a helical form with biasing to prefer one handedness upon complexation with a chiral guest through supramolecular transmission of chirality. The syn form is endowed with the ability to capture a ditopic guest through hydrogen bonds at the amide carbonyls thus in a complexed state, a strong CD signal is produced thanks to a helical conformation induced by the conformational change and a biased handedness. Attachment of chirality to the terephthalamide host itself leads to an intrinsic preference in the sense of dynamic helicity in a helical syn form. Cooperative transmission of chiralities within the host and from the guest enables to further design an advanced sensing system with stereospecific chiroptical modulation, based on a stereospecific change in conformation of the chiral dynamic host upon complexation with a pair of enantiomeric guests.
• Hysteretic Tricolor Electrochromic Systems Based on the Dynamic Redox Properties of Unsymmetrically Substituted Dihydrophenanthrenes and Biphenyl-2,2 '-Diyl Dications: Efficient Precursor Synthesis by a Flow Microreactor Method

  Yusuke Ishigaki, Takanori Suzuki, Jun-ichi Nishida, Aiichiro Nagaki, Naofumi Takabayashi, Hidetoshi Kawai, Kenshu Fujiwara, Jun-ichi Yoshida

  MATERIALS 4 11 1906 - 1926 2011年11月 [査読有り][通常論文]
   

  A series of biphenyl-2,2'-diylbis(diarylmethanol) s 3, which have two kinds of aryl groups at the bay region, were efficiently obtained by integrated flow microreactor synthesis. The diols 3NO/NX are the precursors of unsymmetric biphenylic dications 2NO/NX2+, which are transformed into the corresponding dihydrophenanthrenes 1NO/NX via 2NO/NX+center dot upon reduction, when they exhibit two-stage color changes. On the other hand, the steady-state concentration of the intermediate 2NO/NX+center dot is negligible during the oxidation of 1NO/NX to 2NO/NX2+, which reflects unique tricolor electrochromicity with a hysteretic pattern of color change [color 1 -> color 2 -> color 3 -> color 1].
• Improved synthesis of C8–C20 segment of pectenotoxin-2

  Kenshu Fujiwara, Yuki Suzuki, Nao Koseki, Shun-ichi Murata, Akio Murai, Hidetoshi Kawai, Takanori Suzuki

  Tetrahedron Letters 52 43 5589 - 5592 Elsevier {BV} 2011年10月 [査読有り][通常論文]
   

  The C8-C20 segment of pectenotoxin-2 was efficiently synthesized in 16% overall yield in 22 steps from L-malic acid via an improved route. (C) 2011 Elsevier Ltd. All rights reserved.
• 1,4-Diaryl-7,10-dimethoxyquinoxalino[2,3-b]quinoxalines and Their Dihydro Derivatives: Redox Switching of NIR Absorption and Fluorescence

  Youhei Miura, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Suzuki

  CHEMISTRY LETTERS 40 9 975 - 977 2011年09月 [査読有り][通常論文]
   

  Due to the high-lying HOMO of the substituents and the low-lying LUMO inherited by the heterocyclic skeleton, the title quinoxalinoquinoxalines 1 exhibit absorption bands which extend to the NIR region, whereas the dihydro derivatives 2 are less colored but emit strong green fluorescence. Thus, the present pairs can serve as novel redox dyes for drastic spectral changes.
• Photophysical characteristics of 4,4′-bis(N-carbazolyl)tolan derivatives and their application in organic light emitting diodes

  Masakazu Ohkita, Ayataka Endo, Kimihiro Sumiya, Hajime Nakanotani, Takanori Suzuki, Chihaya Adachi

  Journal of Luminescence 131 7 1520 - 1524 Elsevier {BV} 2011年07月 [査読有り][通常論文]
   

  4,4'-bis(N-carbazolyl)tolan (BCT) and 4,4'-bis[N-(3,6-di-t-butyl)carbazolyl]tolan (BCT-t-Bu) were synthesized as pi-expanded analogs of 4,4'-bis(N-carbazolyl)biphenyl. Their photophysical characteristics both in solution and films were thoroughly investigated. Interestingly, the phosphorescence spectrum of BCT was significantly medium-dependent, and the emission maximum was red-shifted by 131 nm from 489 nm in solution at 77 K to 620 nm in a deposited film at 5 K. suggesting the presence of strong intermolecular interactions in the film. BCT and BCT-t-Bu were found to be useful as host materials for fluorescence-based organic light emitting diodes (OLEDs). However, their low triplet energy levels in films negated their potential to act as hosts in phosphorescence-based OLEDs. (C) 2011 Elsevier B.V. All rights reserved.
• Synthesis of the C22–C37 segment of prorocentin

  Atsushi Takemura, Yasushi Katagiri, Kenshu Fujiwara, Hidetoshi Kawai, Takanori Suzuki

  Tetrahedron Letters 52 11 1222 - 1224 Elsevier {BV} 2011年03月 [査読有り][通常論文]
   

  The synthesis of the C22-C37 segment of prorocentin, isolated from the dinoflagellate Prorocentrum lima, was achieved. Because the relative stereochemical relationship between C26 and other stereocenters (C28/C31/C32 established as R*/R*/R*) in the C22-C37 region of natural prorocentin has not yet been determined, both epimers at C26 of the C22-C37 segment were selectively constructed. The synthesis was based on a 5-exo epoxide ring opening reaction to form an oxolane (E-ring). Brown asymmetric methallylation to install the C26-stereocenter, acryloylation of the resulting alcohol, and ring-closing olefin metathesis to establish the Z-olefin at C23/C24. (C) 2011 Elsevier Ltd. All rights reserved.
• Construction of main-chain type oligorotaxanes and their switching properties: controlled dynamic behavior by imine-bonding formation and cleavage.

  Sugino, H, Kawai, H, Fujiwara, K, Suzuki, T

  Kobunshi Ronbunshu 68 12 795 - 803 The Society of Polymer Science, Japan 2011年 [査読有り][通常論文]
   

  イミン架橋型擬ロタキサンは，軸分子となるヒドリンダセンジホルミル体とジアミノマクロサイクル間のイミン結合形成によって構築される．このイミン架橋型擬ロタキサンは，中性および塩基性条件下においては脱スレッドしないため，さまざまな誘導化が可能である．本研究では，このイミン架橋型擬ロタキサンを軸部分で複数個連結したイミン架橋型オリゴ擬ロタキサンの構築を鍵反応として，イミン架橋型/水素結合型ロタキサン間スイッチング特性をもつオリゴロタキサンを創出した．イミン架橋型オリゴロタキサンは，イミン架橋型擬ロタキサンの軸末端を水素結合部位となるトリエチレングリコールエーテル鎖により連結してオリゴマー化した後，末端を封鎖することにより得られた．トリフルオロ酢酸を酸触媒とするイミン結合の加水分解により，いずれのオリゴロタキサンにおいても水素結合型ロタキサンへ独占的に変換されることが確認された．また，この加水分解溶液を加熱することによりイミン架橋型ロタキサンが再生し，温度変化によって環の位置が制御されるイミン架橋型/水素結合型間スイッチングが達成された．
  
• ChemInform Abstract: Intramolecular Triarylmethane-Triarylmethylium Complex: Generation, Properties, and X-Ray Structure of a C-H-Bridged Carbocation

  Takanori Suzuki, Takashi Takeda, Yasuyo Yoshimoto, Takayuki Nagasu, Hidetoshi Kawai, Kenshu Fujiwara

  ChemInform 41 39 no - no 2010年09月02日 [査読有り][通常論文]
  
• 32 プロロセンチンの全合成と絶対配置の決定(口頭発表の部)

  片桐 康, 藤原 憲秀, 竹村 淳志, 河合 英敏, 鈴木 孝紀

  天然有機化合物討論会講演要旨集 52 187 - 192 天然有機化合物討論会 2010年09月01日 

  Prorocentin, isolated from dinoflagellate Prorocentrum lima by Lu et al., exhibits inhibitory activity against some human cancer cell lines [IC_<50>: 16.7μg/mL (DLD-1); 83.67μg/mL (RPM17951)] and possesses an unique polyether structure, characterized by a [6,6]-spirocyclic acetal fused with an oxane ring (BCD-ring), an epoxide (A-ring), a five membered ether (E-ring) and a side chain including a conjugated triene group. Although the absolute configuration of prorocentin has not yet been determined, its biological and structural features make it an attractive synthetic target. Thus,a project toward the total synthesis of prorocentin aiming at determination of the absolute stereochemistry has been commenced. The partial relative structure of prorocentin was proposed by Lu et al. from their intensive NMR experiments, and a possible stereostructure was also shown as 1 in their report. Therefore, we first performed the total symthesis of 1. First, the C8-C20 segment (6) was synthesized from alkyne 7 and 8 via a process including Pd-catalyzed 6-endo cyclization. Aldehyde 6 was then connected with the C21-C35 segment(5), and the resulting alcohol was transformed to 27. The intramolecular double conjugate addition reaction of 27 produced the CD-ring spiroacetal (28), which was transformed to E-iodoalkene 4. The Suzuki-Miyaura coupling of 4 with dienylborane 3 followed by the removal of TBS groups and the concomitant epoxide fromation completed the total synthesis of 1. However, the ^1H and ^<13>C NMR spectra of 1 disagreed with those of natural prorocentin. Since the large deviations of chemical shifts between them were observed in the B-ring, we conferred with Lu on the deviations and deduced structure 2, having a hydroxy group at C17 of the B-ring, as a plausible structure of prorocentin. Thus, we next achieved the total synthesis of 2. The synthetic process was almost similar to that of 1, except the preparation of the B-ring (36), which was carried out by a process involving the aldol reaction of ketone 37 and 38. Finally, compound 2 showed the same spectral properties as natural prorocentin, except the opposite sign of optical rotation, thereby concluding that natural prorocentin is the enantiomer of 2.
• Enhancement of transcriptional activity of mutant p53 tumor suppressor protein through stabilization of tetramer formation by calix[6]arene derivatives

  Rui Kamada, Wataru Yoshino, Takao Nomura, Yoshiro Chuman, Toshiaki Imagawa, Takanori Suzuki, Kazuyasu Sakaguchi

  BIOORGANIC & MEDICINAL CHEMISTRY LETTERS 20 15 4412 - 4415 2010年08月 

  Li-Fraumeni syndrome, a hereditary disorder characterized by familial clusters of early-onset multiple tumors, is caused by mutation of the TP53 gene, which encodes the p53 tumor suppressor protein. Mutation of Arg337 to histidine in the tetramerization domain of p53 is most frequently observed in Li-Fraumeni syndrome. This mutation is reported to destabilize the tetrameric structure of p53. We designed and synthesized calix[6] arene derivatives, which have six imidazole or pyrazole groups at the upper rim. In this study, we report, for the first time, the enhancement of the in vivo transcriptional activity of the most common Li-Fraumeni p53 mutant by imidazole-calix[6] arene through stabilization of the oligomer formation. (C) 2010 Elsevier Ltd. All rights reserved.
• Studies toward the total synthesis of armatol F: stereoselective construction of the C6 and C7 stereocenters and formation of the A-ring skeleton

  Kenshu Fujiwara, Yuta Hirose, Daisuke Sato, Hidetoshi Kawai, Takanori Suzuki

  TETRAHEDRON LETTERS 51 32 4263 - 4266 2010年08月 [査読有り][通常論文]
   

  Armatol F, isolated from the red alga Chondria armata as a polyether triterpene, has a solitary oxepane (A-ring) and a fused tricyclic ether moiety (BCD-ring). The A-ring features a rare cis-relationship between the hydroxy group at the quaternary carbon C6 and the carbon chain at C7. As part of our program toward the total synthesis of armatol F, a new stereoselective method for the construction of the C6 and C7 stereocenters has been developed based on chirality-transferring Ireland-Claisen rearrangement. The A-ring skeleton has also been synthesized from the rearrangement product by a process including ring-closing olefin metathesis. (C) 2010 Elsevier Ltd. All rights reserved.
• Model studies for the stereoselective construction of the BC-ring of armatol F based on Ireland-Claisen rearrangement and relay ring-closing olefin metathesis

  Kenshu Fujiwara, Keita Tanaka, Yasushi Katagiri, Hidetoshi Kawai, Takanori Suzuki

  TETRAHEDRON LETTERS 51 34 4543 - 4546 2010年08月 [査読有り][通常論文]
   

  Armatol F, isolated from the red alga Chondria armata as a polyether triterpene, has a fused tricyclic ether moiety (BCD-ring) with an unusual cis ring junction at C18-C19 between the C- and D-rings. En route to the total synthesis of armatol F, the stereoselective construction of the C18 and C19 stereocenters by Ireland-Claisen rearrangement and the formation of the C-ring by relay ring-closing olefin metathesis were established through the synthesis of monocyclic (C-ring) and bicyclic (BC-ring) model compounds. (C) 2010 Elsevier Ltd. All rights reserved.
• Intramolecular Chirality Transfer in trans-5,6-Diaryl-5,6-dihydro-1,10-phenanthroline-5,6-diols: Solvato- and Halochromic Responses by Circular Dichroism

  Takanori Suzuki, Youhei Miura, Tatsuo Nehira, Hidetoshi Kawai, Kenshu Fujiwara

  CHEMISTRY LETTERS 39 7 695 - 697 2010年07月 [査読有り][通常論文]
   

  Not only the configuration at the C5 and C6 stereocenters but also the intra/intermoleculer hydrogen-bonding mode are determinant for the sense of mobile helicity of the dihydrophenanthroline unit in the title diols in solution. Thus, drastic changes in chiroptical signals are induced through conformational switching of 1 upon addition of protic solvent and/or acid.
• Intramolecular triarylmethane-triarylmethylium complex: Generation, properties, and X-ray structure of a C–H bridged carbocation

  Takanori Suzuki, Takashi Takeda, Yasuyo Yoshimoto, Takayuki Nagasu, Hidetoshi Kawai, Kenshu Fujiwara

  Pure and Applied Chemistry 82 4 1033 - 1044 Walter de Gruyter {GmbH} 2010年04月 [査読有り][通常論文]
   

  A series of title carbocations was generated and isolated as stable salts. X-ray analyses revealed a preference for an unsymmetric structure in which the bridging hydrogen is localized on one of the two triarylmethane units. NMR spectroscopy showed a similar preference in solution. The bridging hydrogen fluctuates between the two chromophores in solution, and the energy barrier for the H shift is linearly correlated with the C center dot center dot center dot C(+) separation determined by X-ray. According to an extrapolation, the energy barrier should decrease when the C center dot center dot center dot C(+) separation is less than 2.7 angstrom, which suggests a new model for isolable pure organic species with a three-center two-electron bond.
• Intramolecular triarylmethane-triarylmethylium complex: Generation, properties, and X-ray structure of a C–H bridged carbocation

  Takanori Suzuki, Takashi Takeda, Yasuyo Yoshimoto, Takayuki Nagasu, Hidetoshi Kawai, Kenshu Fujiwara

  Pure and Applied Chemistry 82 4 1033 - 1044 Walter de Gruyter {GmbH} 2010年04月 [査読有り][通常論文]
   

  A series of title carbocations was generated and isolated as stable salts. X-ray analyses revealed a preference for an unsymmetric structure in which the bridging hydrogen is localized on one of the two triarylmethane units. NMR spectroscopy showed a similar preference in solution. The bridging hydrogen fluctuates between the two chromophores in solution, and the energy barrier for the H shift is linearly correlated with the C center dot center dot center dot C(+) separation determined by X-ray. According to an extrapolation, the energy barrier should decrease when the C center dot center dot center dot C(+) separation is less than 2.7 angstrom, which suggests a new model for isolable pure organic species with a three-center two-electron bond.
• Halochromic Chiroptical Response of Novel Bis(9-acridinyl)-type Fluorophores with a Helical pi Framework

  Tatsuo Nehira, Yasuyo Yoshimoto, Kazuhisa Wada, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Suzuki

  CHEMISTRY LETTERS 39 3 165 - 167 2010年03月 [査読無し][通常論文]
   

  Acridine-based novel fluorophores 1/2 with a helical dihydrodibenzoxepin/azepine skeleton exhibit halochromic response upon addition of Bronsted acid in CH2Cl2, thus giving UV-vis and fluorescence spectral changes. By using the optically resolved species [(M)-1/2], circular dichroism (CD) and fluorescence detected-CD (FDCD) signals were also changed drastically, thus demonstrating four-way-output response thanks to configurational stability of helicity and efficient exciton coupling.
• PHENANTHRENE-4,5-DIYLBIS(10-METHYLACRIDINIUM) WITH A SHORT C+ -- C+ CONTACT: PREPARATION, MOLECULAR STRUCTURE, REDOX PROPERTIES, AND ELECTROCHROMIC INTERCONVERSION WITH DIHYDROPYRENE DERIVATIVE

  Takanori Suzuki, Yasuyo Yoshimoto, Kazuhisa Wada, Takashi Takeda, Hidetoshi Kawai, Kenshu Fujiware

  HETEROCYCLES 80 1 149 - 155 2010年01月 [査読無し][通常論文]
   

  The title dication (1(2+)) was generated by oxidative bond cleavage of a 4,5-dihydoropyrene derivative (2) with two spiro(10-methylacridan) units. Despite the skewed deformation of the arylene spacer, two cationic chromophores in 1(2+) are forced to face in a proximity with a very short interatomic separation of 2.98(1) angstrom between carbenium centers (X-ray), which makes the LUMO level of 1 much lower than that of biphenyl-2,2'-diyl-type dication (3(2+)).
• Drastic change in racemization barrier upon redox reactions: novel chiral-memory units based on dynamic redox systems

  Takanori Suzuki, Kazuhisa Wada, Yusuke Ishigaki, Yasuyo Yoshimoto, Eisuke Ohta, Hidetoshi Kawai, Kenshu Fujiwara

  CHEMICAL COMMUNICATIONS 46 23 4100 - 4102 2010年 [査読有り][通常論文]
   

  The helical configuration of dication dyes 2(2+) with a dihydro-dibenzoxepin unit remained unchanged even at high temperature, whereas the corresponding neutral electron donors 1 with a tetrahydrophenanthroxepin skeleton easily underwent racemization. Due to their electrochemical bistability, electron exchange between 1 and 2(2+) is prohibited. Thus, the above electrochromic pairs can serve as novel chiral-memory units where redox reactions trigger switching between an "erasable/writable''-state (1) and a "memorizing''-state (2(2+)).
• PHENANTHRENE-4,5-DIYLBIS(10-METHYLACRIDINIUM) WITH A SHORT C+ -- C+ CONTACT: PREPARATION, MOLECULAR STRUCTURE, REDOX PROPERTIES, AND ELECTROCHROMIC INTERCONVERSION WITH DIHYDROPYRENE DERIVATIVE

  Takanori Suzuki, Yasuyo Yoshimoto, Kazuhisa Wada, Takashi Takeda, Hidetoshi Kawai, Kenshu Fujiware

  HETEROCYCLES 80 1 149 - 155 2010年01月 [査読有り][通常論文]
   

  The title dication (1(2+)) was generated by oxidative bond cleavage of a 4,5-dihydoropyrene derivative (2) with two spiro(10-methylacridan) units. Despite the skewed deformation of the arylene spacer, two cationic chromophores in 1(2+) are forced to face in a proximity with a very short interatomic separation of 2.98(1) angstrom between carbenium centers (X-ray), which makes the LUMO level of 1 much lower than that of biphenyl-2,2'-diyl-type dication (3(2+)).
• ChemInform Abstract: 4,5-Bis(diarylmethylene)-1,3-dithiole: A Novel Helical Electron Donor Exhibiting Electrochromic Behavior.

  Takanori Suzuki, Shintaro Mikuni, Yusuke Ishigaki, Hiroki Higuchi, Hidetoshi Kawai, Kenshu Fujiwara

  ChemInform 40 44 2009年11月03日 [査読有り][通常論文]
  
• Dynamic Molecular Propeller: Supramolecular Chirality Sensing by Enhanced Chiroptical Response through the Transmission of Point Chirality to Mobile Helicity

  Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Suzuki

  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 131 46 16896 - 16904 2009年11月 [査読有り][通常論文]
   

  The secondary terephthalamide host la-H attached to four aryl blades was prepared from tetrabromide 2a by Suzuki-Miyaura coupling and undergoes a conformational change from a nonpropeller anti-form to a propeller-shaped syn-form upon complexation with ditopic guests such as p-xylylenediammonium derivatives (RR)/(SS)-3 (chirality generation). Through transmission of the point chiralities attached on the nitrogens in the chiral guests to the mobile helicity in 1a-H, the propeller-shaped host in the complex is biased to prefer a particular handedness (chirality biasing). While chiral guests with simple point chiralities such as (R,R)/(S,S)-3 exhibit only very weak CD activity, complexation with the dynamic propeller host 1 a-H results in much stronger chiroptical signals (chiroptical enhancement). The chirality generation-chirality biasing protocol was successfully applied to a neurotransmitter, (-)-phenylephrine 4, acting as a chiral ditopic guest. When the chiral auxiliaries are attached to the host as in (R,R)-1b-H, complexation with (S,S)-3 causes CD enhancement but not with (R,R)-3, due to chiral recognition.
• P-37 紅藻由来トリテルペン縮環ポリエーテル、アルマトールFの合成研究(ポスター発表の部)

  藤原 憲秀, 広瀬 悠太, 田中 啓太, 片桐 康, 佐藤 大輔, 河合 英敏, 鈴木 孝紀

  天然有機化合物討論会講演要旨集 51 347 - 352 天然有機化合物討論会 2009年09月01日 

  Armatol F (1), isolated from the red alga Chondria armata by Ciavatta et al., is an unusual triterpene compound characterized by the presence of an oxepane (A-ring), a 6/7/7 fusea-tricyclic ether (BCD-ring), six quaternary carbons, and two bromine atoms in its structure. It is also notable that 1 has a cis ring-fusion between C- and D-rings, which is a rare mode of ring-fusion in polycyclic ether natural procudts. The absolte configuraton of the A-ring and relative stereostructure of the BCD-ring have been elucidated by NMR and degradation studies, but the full absolute stereochemistry of 1 remains unclear. Although the bioactivity of 1 has not been reported, it is strongly expected that 1 would have some biological properties because of its striking structural similarity to bioactive thyrsiferol and the congeners. Since we have been interested in the structural complexity and the potential bioactivity of 1, we have been engaged in studies toward the total synthesis of 1 and the determination of its full absolute configuration. As a part of the studies, the model syntheses of the A and BCD-ring skeletons were performed. In the synthesis of A-ring model 16, a chirality transferring Ireland-Claisen rearrangement and a ring-closing olefin metathesis (RCM) were employed as key reactions for the construction of the oxepane skeleton, and the final bromination at C3 is now under investigation. BCD-ring model 18 was designed to be constructed from B-ring model 36 via a chirality transferring Ireland-Claisen rearrangement, an RCM, and Morimoto's intramolecular bromoetherification. At present, BC-ring 50, possessing a carbon chain corresponding to the D-ring, has been synthesized. The details of the model syntheses will be presented in the poster session.
• Negligible diradical character for the ultralong C-C bond in 1,1,2,2-tetraarylpyracene derivatives at room temperature

  Takashi Takeda, Hidetoshi Kawai, Rainer Herges, Eva Mucke, Yoshitaka Sawai, Kei Murakoshi, Kenshu Fujiwara, Takanori Suzuki

  TETRAHEDRON LETTERS 50 26 3693 - 3697 2009年07月 [査読有り][通常論文]
   

  There is evidence that the crystalline-state thermochromic behavior of dispiropyracene acr-1 with an ultralong C-C bond [1.791(3) angstrom at 413 K, 1.771(3) angstrom at 93K] might be due to thermal generation of a bond-dissociated triplet diradical. The C(1)-C(2) bond lengths (d) in the newly prepared 1,1,2,2-tetraarylpyracenes 1a-e [1.717(4)-1.761(4) angstrom at 113/123/153 K] are also much larger than the standard value for C(sp(3))-C(sp(3)) (1.54 angstrom). The fact that there is no correlation between d and the radical-stabilizing parameter (sigma(center dot)) provides evidence that there is no contribution from a crystallographic artifact caused by contamination of the diradical in the crystal of 1 at room temperature or below. Further indication for the covalent nature of the ultralong C-C bond in tetraphenylpyracene 1c was attained by Raman spectroscopy, showing the far Fed-shifted C(1)-C(2) Stretching vibration (638 cm(-1)) and by the theoretical prediction of very large vertical singlet-triplet energy gap (58.3 kcal mol(-1) at the UB3LYP/6-31G* level). However, at elevated temperatures bond dissociation might occur forming a triplet diradical. (C) 2009 Elsevier Ltd. All rights reserved.
• Preparation and X-ray Structures of trans-5,6-Diaryl-5,6-dihydro-1,10-phenanthroline-5,6-diols: Formation of Supramolecular Rod by Hydrogen Bonds

  Takanori Suzuki, Youhei Miura, Ryuuichi Tamaki, Hidetoshi Kawai, Kenshu Fujiwara

  CHEMISTRY LETTERS 38 7 670 - 671 2009年07月 [査読有り][通常論文]
   

  A series of X-ray analyses on the newly prepared title molecules have revealed that the one-dimensional rod-like structures are commonly present in the crystals of trans-dihydrophenan-throlinediols. The architecture is of interest from the viewpoint of supramolecular chirality because homochiral diol molecules with the same sense of helicity are connected in a head-to-tail fashion by a pair of N center dot center dot center dot H-O hydrogen bonds.
• 4,5-Bis(diarylmethylene)-1,3-dithiole: A Novel Helical Electron Donor Exhibiting Electrochromic Behavior

  Takanori Suzuki, Shintaro Mikuni, Yusuke Ishigaki, Hiroki Higuchi, Hidetoshi Kawai, Kenshu Fujiwara

  CHEMISTRY LETTERS 38 7 748 - 749 2009年07月 [査読有り][通常論文]
   

  Vivid color change from intense yellow to deep purple was observed upon electrochemcal oxidation of the title donor 1 to bis(Michler's hydrol blue)-type dication 1(2+). Since the interconversion was also accompanied by drastic geometric changes, configurational stability of the helical pi-arrangement is modified upon redox reactions.
• Distorted Saturated Hydrocarbons

  Kata Mlinarić-Majerski, Helena Dodziuk, Tatyana N. Gribanova, Vladimir I. Minkin, Ruslan M. Minyaev, Takanori Suzuki, Takashi Takeda, Hidetoshi Kawai, Kenshu Fujiwara, Vladimir Y. Lee, Akira Sekiguchi

  Strained Hydrocarbons: Beyond the van-t Hoff and Le Bel Hypothesis 33 - 102 2009年05月08日 [査読有り][通常論文]
  
• Stereoselective construction of an anti-β-alkoxy ether by Ireland–Claisen rearrangement for medium-ring ether synthesis

  Kenshu Fujiwara, Natsumi Kawamura, Hidetoshi Kawai, Takanori Suzuki

  Tetrahedron Letters 50 11 1236 - 1239 Elsevier {BV} 2009年03月 [査読有り][通常論文]
   

  The asymmetric synthesis of an acyclic anti-beta-alkoxy ether was achieved by the Ireland-Claisen rearrangement of Z-3-aikoxy-2-propenyl glycolate ester, prepared from Garner's aldehyde, a glycolic acid derivative, and ethynyl N,N-diisopropylcarbamate. The resulting acyclic ether was facilely converted to seven- and eight-membered cyclic ethers via processes involving ring-closing olefin metatheses. (C) 2009 Elsevier Ltd. All rights reserved.
• Strained Hydrocarbon (Chap 2.5 Ultralong C-C Bond)

  Wiley-VCH 2009年 [査読無し][通常論文]
  
• Intramolecular Methylacridan-Methylacridinium Complexes with a Phenanthrene-4,5-diyl or Related Skeleton: Geometry-Property Relationships in Isolable C-H Bridged Carbocations

  Takanori Suzuki, Yasuyo Yoshimoto, Takashi Takeda, Hidetoshi Kawai, Kenshu Fujiwara

  CHEMISTRY-A EUROPEAN JOURNAL 15 9 2210 - 2216 2009年 [査読有り][通常論文]
   

  The isolation and low-temperature X-ray analyses of a series of intramolecular methylacridan-methylacridinium complexes have been achieved. The two chromophores are in close proximity due to an arylene spacer, such as a phenanthrene-4,5-diyl or biphenyl-2.2'-diyl unit. These bridged carbocations prefer the C-H localized structure both in solution and in the solid state. The bridging hydrogen atom undergoes a facile intramolecular hydride shift from one carbon atom to another in solution, and the energy barrier is linearly correlated with the intramolecular C center dot center dot center dot C(+) distance in the solid state geometry, as determined by single-crystal X-ray analyses. By extrapolation from the data, the delocalized three-center bond of [C-H-C](+) would be formed when the C center dot center dot center dot C(+) distance is less than 2.7 angstrom.
• Multi-Input/Multi-Output Molecular Response System Based on the Dynamic Redox Behavior of 3,3,4,4-Tetraaryldihydro[5]helicene Derivatives: Reversible Formation/Destruction of Chiral Fluorophore and Modulation of Chiroptical Properties by Solvent Polarity

  Takanori Suzuki, Yusuke Ishigaki, Tomohiro Iwai, Hidetoshi Kawai, Kenshu Fujiwara, Hiroshi Ikeda, Yusuke Kano, Kazuhiko Mizuno

  CHEMISTRY-A EUROPEAN JOURNAL 15 37 9434 - 9441 2009年 [査読有り][通常論文]
   

  3,3,4,4-Tetaaryldihydro[5]helicenes (1) and 1,1'-binaphthyl-2,2'-diyl-bis(diarylcarbenium)s (2(2+)) can be reversibly interconverted upon electron transfer, which is accompanied by a vivid color change (electrochromism) as well as by the formation/cleavage of a C-C bond ("dynamic redox behavior"). Because only the neutral donor 1 exhibits strong fluorescence, electrochemical input can further modify the fluorescent properties of the pair. Due to the configurational stability of the helicity in 1 and axial chirality in 2(2+), the redox reaction of optically pure material proceeds stereospecifically, which induces a chiroptical change such as circular dichroism (CD) as an additional output. The CD spectra of dications 2(2+) exhibit solvent dependency (chiro-solvatochromism), which is accompanied by solvatochromic behavior based on the pi-pi interaction of the two cationic chromophores as well as coordinative interaction of the Lewis basic solvent to the Lewis acidic triarylcarbenium moieties. Thus, the present system is endowed with multi-input functionality for modifying multiple output signals.
• Entropy- and hydrolytic-driven positional switching of macrocycle between imine- and hydrogen-bonding stations in rotaxane-based molecular shuttles

  Takeshi Umehara, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Suzuki

  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 130 42 13981 - 13988 2008年10月 [査読有り][通常論文]
   

  The construction and switching properties of a novel class of molecular shuttles 1 with imine-bonding stations for macrocyclic diamine parts are reported. Studies on dithioacetalized [2]rotaxane 4 with two hydrogen-bonding stations and a masked imine-bonding station showed that protonation of a macrocycle increases the shuttling barrier due to hydrogen-bond formation between NH(3)(+) groups and the TEG-stations. Hydrolysis of the imine-bonds of the imine-bridged molecular shuttles 1b,c with TEG-stations could exclusively give the [2]rotaxane 2b,c center dot 2H(2+), With the macrocycle hydrogen-bonded with the TEG-station. In contrast, la without TEG-stations gave an equilibrated mixture of la, monoimine 3a center dot H(+), and 2a center dot 2H(2+) under similar acidic hydrolytic conditions. The equilibrium between 1b,c and 2b,c center dot 2H(2+) to control the position of the macrocycle could be successfully switched to either side by applying acidic hydrolytic or dehydrating conditions. Furthermore, the equilibrium was largely biased to [2]rotaxane 2b,c center dot 2H(2+) under acidic hydrolytic conditions and could be reversed in favor of bis-imine 1b,c just by heating. This is a successful example of a molecular shuttle exhibiting entropy-driven translational isomerism with remarkable positional discrimination. An examination of thermodynamic parameters showed that imine-bond hydrolyses and the formation of hydrogen bonds between the macrocycle and the station are thermodynamically matched processes, because both processes are enthalpically favored and accompanied by a loss of entropy. The combination of imine-bonding and hydrogen-bonding station in a rotaxane system is the key to realizing the clear entropy-driven positional switching of the macrocycle observed.
• P-82 プロロセンチンの全合成研究(ポスター発表の部)

  藤原 憲秀, 片桐 康, 竹村 淳志, 河合 英敏, 鈴木 孝紀

  天然有機化合物討論会講演要旨集 50 783 - 787 天然有機化合物討論会 2008年09月01日 

  Prorocentin, isolated from dinoflagellate Prorocentrum lima by Lu et al., exhibits inhibitory activity against some human cancer cell lines [IC_<50>: 16.7μg/mL (DLD-1); 83.6μg/mL (RPMI7951)] and possesses an unique polyether structure, featured by a [6,6]-spirocyclic acetal fused with an oxane ring (BCD-ring), an epoxide (A-ring), a five membered ether (E-ring), and a side chain including a conjugated triene group. Although the absolute configuration of prorocentin has not yet been determined, its biological and structural features make it an attractive synthetic target. Thus, a project toward the total synthesis of prorocentin aiming at determination of the absolute stereochemistry has been commenced. The partial relative stereochemistry of prorocentin was proposed by Lu et al. from their intensive NMR experiments, and a possible stereostructure was also shown as 1 in their report. Therefore, we first elucidated a synthetic plan for prorocentin based on the stereochemistry of 1. At the final stage in the synthesis, assembly of 1 from dienyl boran 2 and iodoalkene 3 via a Suzuki-Miyaura coupling followed by removal of TBS group and the simultaneous epoxide formation is intended. Iodoalkene 3 would be derived from C8-C35 segment 4 in a few steps including Takai olefination and protective group manipulation. So far, we have synthesized segments 2 and 4, and examined the above transformation processes (4→3 and 3+2→1) in a model system. Details of the synthesis of 4, based on 6-endo Utimoto cyclization to create the B-ring and intramolecular double conjugate addition to produce the CD-ring, and the model experiments will be described in the poster session.
• Synthesis of the ABC-ring models of goniodomin A: preference for the unnatural configuration at C11 of the BC-ring in a non-macrocyclic model system

  Takahiro Katagiri, Kenshu Fujiwara, Hidetoshi Kawai, Takanori Suzuki

  TETRAHEDRON LETTERS 49 20 3242 - 3247 2008年05月 [査読有り][通常論文]
   

  To confirm the natural relative stereochemistry of the ABC-ring of goniodomin A (1), the corresponding three stereoisomeric compounds, (2R,5S,6S,7S,9S,11R,15S)-, (2R,5S,6S,7R,9R,11S,15R)-, and (2R,5S,6S,7R,9R,11R,15S)-isomers (2, 3, and 5, respectively), were stereoselectively synthesized using a Nozaki-Hiyama-Kishi reaction as a key step. It was also found that a (2R,5S,6S,7R,9R,11S,15S)-isomer (4), corresponding to the absolute configuration of I recently proposed by Sasaki, was not detected during the formation of 5 from a common ketodiol substrate under acid-catalyzed spiroacetalization conditions. This would be attributable to the absence of a macrocyclic framework. (c) 2008 Elsevier Ltd. All rights reserved.
• Ultralong C-C bonds in hexaphenylethane derivatives

  Takanori Suzuki, Takashi Takeda, Hidetoshi Kawai, Kenshu Fujiwara

  PURE AND APPLIED CHEMISTRY 80 3 547 - 553 2008年03月 [査読有り][通常論文]
   

  The longer C-C bond than the standard (1.54 angstrom) is so weakened that it is cleaved easily, as found in the parent hexaphenylethane (HPE). However, the compounds with an ultralong C-C bond (1.75 angstrom) can be isolated as stable solids when the bond-dissociated species does not undergo any reactions other than bond reformation. This is the central point in designing the highly strained HPEs, which were obtained by two-electron reduction of the corresponding dications. Steric repulsion of "front strain" is the major factor to expand the central C-C bond of HPEs. During the detailed examination of the ultralong C-C bond, the authors discovered the intriguing phenomenon of "expandability": the C-C bond length can be altered over a wide range by applying only a small amount of energy (1 kcal mol(-1)) supplied by crystal packing force. This observation indicates that the much longer C-C bond than the shortest nonbonded contact (1.80 angstrom) will be realized under the rational molecular design concept.
• Concise stereoselective synthesis of cis-3-alkoxy-2-carbomethoxy medium-ring oxacycles from (R)-3-(3-butenyl)-4-propynoyloxazolidin-2-one

  Daisuke Sato, Kenshu Fujiwara, Hidetoshi Kawai, Takanorl Suzuki

  TETRAHEDRON LETTERS 49 9 1514 - 1517 2008年02月 [査読無し][通常論文]
   

  A concise process for the stereoselective synthesis of chiral cis-3-alkoxy-2-carbomethoxy medium-ring oxacycles from (R)-3-(3-butenyl)-4-propynoyloxazolidin-2-one (1) was developed. The process includes five major steps: (i) hetero-Michael reaction between an alcohol and 1, (ii) stereoselective reduction of the resulting ketone, featuring stereochemical assistance of the neighboring oxazolidin-2-one group, (iii) esterification with an alkoxy acetic acid, (iv) chirality-transferring Ireland-Claisen rearrangement of the resulting 3-alkoxyallyl glycolate ester to provide a syn-2,3-dialkoxy carboxylate ester, and (v) relay ring-closing olefin metathesis to form a medium-ring ether along with the simultaneous removal of the oxazolidin-2-one moiety. (c) 2007 Elsevier Ltd. All rights reserved.
• Synthesis of the DE-ring of goniodomin A and prediction of its natural relative stereochemistry

  Takahiro Katagiri, Kenshu Fujiwara, Hidetoshi Kawai, Takanori Suzuki

  TETRAHEDRON LETTERS 49 2 233 - 237 2008年01月 [査読無し][通常論文]
   

  Goniodomin A (1) was first isolated from Alexandrium hiranoi as a stereochemically unidentified antifungal agent in 1987 by Murakami. In this study, two stereoisomeric series of non-macrocyclic and macrocyclic DE-ring model compounds of I were synthesized, and the natural relative stereochemistry of the DE-ring was predicted by NMR comparison of I with these model compounds. (c) 2007 Elsevier Ltd. All rights reserved.
• Ultralong carbon-carbon bonds in dispirobis(10-methylacridan) derivatives with an acenaphthene, pyracene, or dihydropyracylene skeleton

  Hidetoshi Kawai, Takashi Takeda, Kenshu Fujiwara, Makoto Wakeshima, Yukio Hinatsu, Takanori Suzuki

  CHEMISTRY-A EUROPEAN JOURNAL 14 19 5780 - 5793 2008年 [査読有り][通常論文]
   

  Acenapthalene, pyracene, and dihydropyracylene attached to two units of spiroacridan are a novel class of hexaphenylethane (HPE) derivatives that have an ultralong C-sp3-C-sp3 bond (1.77-1.70 angstrom). These sterically challenged molecules were cleanly prepared by C-C bond formation through two-electron reduction from the less-hindered dications. These ultralong bonds were realized based on several molecular-design concepts including enhanced "front strain" through "multiclamping" by means of fusing or bridging aryl groups in the HPE molecule. The lengths of these ultralong bonds and their relation to the conformation (torsional angle) were also validated by means of theoretical calculations. Bond-fission experiments revealed that the bonds are more easily cleaved than standard covalent bonds to produce the corresponding dication upon oxidation with an increase in the length of the C-C bond.
• Designed molecular propellers based on tetraarylterephthalamide and their chiroptical properties induced by biased helicity through transmission of point chirality

  Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Suzuki

  CHEMICAL COMMUNICATIONS 40 4906 - 4908 2008年 [査読有り][通常論文]
   

  The syn-atropisomers of the title bis(tertiary amide)s were designed as six-bladed molecular propellers based on the ''directing effects'' of amide dipoles; the helicity of the propeller is biased to prefer one handedness upon the attachment of point chirality to the amide nitrogens to attain stronger circular-dichroism activity than for the non-propeller-shaped anti-isomers.
• Unprecedented four-way-output molecular response system based on biphenyl-2,2 '-diyldiacridiniums: induction of axial chirality through intramolecular hydrogen bonds between chiral amide groups

  Takanorl Suzuki, Kenji Ohta, Tatsuo Nehira, Hiroki Higuchi, Eisuke Ohta, Hidetoshi Kawai, Kenshu Fujiwara

  TETRAHEDRON LETTERS 49 5 772 - 776 2008年01月 [査読有り][通常論文]
   

  Upon the attachment of N-(R)-2-phenylethylamide moieties to the acridinium units of the title dication, intramolecular hydrogen bonds induce a diastereomeric preference in terms of axial chirality (70% de at -40 degrees C in CH(2)Cl(2)). Thus, external stimuli induce not only UV-vis and fluorescence spectra changes but also changes in the CD and fluorescence-detected CD (FDCD) spectra, realizing unprecedented four-way-output molecular response systems. (C) 2007 Elsevier Ltd. All rights reserved.
• Four-way-output molecular response system based on the dihydrodibenzo[c,g]phenanthrene skeleton: modulation of CD and FDCD activity by acid and electron-transfer

  Eisuke Ohta, Tatsuo Nehira, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Suzuki

  TETRAHEDRON LETTERS 49 5 777 - 781 2008年01月 [査読有り][通常論文]
   

  Presence or absence of electron-accepting dye chromophores is the key function for ON/OFF switching of fluorescence from the dihydrodibenzo[c,g]phenanthrene skeleton in 2(2+)/3. The helical fluorophore in 2(2+) could be generated stereoselectively upon electrolysis of binaphthylic donor 1 through intramolecular chirality transmission. Huge chiroptical signals are easily detected by circular dichroism, (CD) and fluorescence-detected CD (FDCD) techniques to realize novel four-way-output response. (C) 2007 Elsevier Ltd. All rights reserved.
• Synthesis of the EF-ring of ciguatoxin 3C based on the [2,3]-Wittig rearrangement and ring-closing olefin metathesis

  Akiyoshi Goto, Kenshu Fujiwara, Ayako Kawai, Hidetoshi Kawai, Takanori Suzuki

  ORGANIC LETTERS 9 26 5373 - 5376 2007年12月 [査読有り][通常論文]
   

  The EF-ring segment of ciguatoxin 3C, a causative toxin of ciguatera fish poisoning, was synthesized in three major steps: 1,4-addition for the C20O-C27 bond connection, chirality transferring anti selective [2,3]-Wittig rearrangement for the construction of the anti-2-hydroxyalkyl ether part, and ring-closing olefin metathesis for the F-ring formation.
• P-76 ヘテロ共役付加と不斉転写型シグマトロピー転位を利用した鎖状二級アルキルエーテル合成とその応用(ポスター発表の部)

  後藤 研由, 藤原 憲秀, 河合 綾子, 河合 英敏, 鈴木 孝紀

  天然有機化合物討論会講演要旨集 49 703 - 708 天然有機化合物討論会 2007年08月24日 

  Stereoselective construction of medium-sized cyclic ethers is one of the major problems in the synthesis of fused-polycyclic ether natural compounds, represented by ciguatoxin CTX3C. We have explored efficient solutions for the problem, and examined an application of a ring-closing olefin metathesis reaction (RCM), one of the most reliable methods for the formation of medium-ring structure, to cyclic ether synthesis. Although preparation of the precursors for RCM involved a serious difficulty in the stereoselective construction of their acyclic di-sec-alkyl ether part, we found its effective answers, namely, the [2,3]-Wittig rearrangement of a 3-alkoxyallyloxyacetic acid ester and the Ireland-Claisen rearrangement of a 3-alkoxyallyl glycolate. These rearrangement reactions stereoselectively produced 1,2-dialkoxy structures, which were easily transformed to medium cyclic ethers through a process including RCM. Details of the rearrangement reactions and the preparation method for the substrates using a hetero-conjugate addition reaction will be discussed at the presentation. The applications of these rearrangement reactions to the synthesis of the EF-ring of CTX3C will also be described.
• Synthesis and relative stereochemistry of the A- and F-rings of goniodomin A

  Kenshu Fujiwara, Jota Naka, Takahiro Katagiri, Daisuke Sato, Hidetoshi Kawai, Takanori Suzuki

  BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 80 6 1173 - 1186 2007年06月 [査読無し][通常論文]
   

  The synthesis of the A- and F-rings of goniodomin A (1), which is a stereochemically unidentified antifungal agent isolated from dinoflagellate Alexandrium hiranoi, was performed to determine of the relative stereochemistry of these parts. The relative stereochemistry of the A- and F-rings was first deduced from Murakami's NMR data, and model compounds corresponding to these parts were then synthesized. The synthetic A-ring model, of which the structure was established by X-ray crystallographic analysis, showed good agreement with the natural A-ring on the basis of J and NOE behavior in the H-1 NMR spectroscopy. The chemical shifts in H-1 and C-13 NMR specta and J(32-OH-H33) of the synthetic F-ring model having a 33S,34R configuration also agreed with those of the F-ring of 1. Thus, the relative stereochemistry of the A- and F-rings of 1 was elucidated.
• Synthesis of the C8-C20 and C21-C30 segments of pectenotoxin 2

  Kenshu Fujiwara, Yu-ichi Aki, Fuyuki Yamamoto, Mariko Kawamura, Masanori Kobayashi, Azusa Okano, Daisuke Awakura, Shunsuke Shiga, Akio Murai, Hidetoshi Kawai, Takanori Suzuki

  TETRAHEDRON LETTERS 48 26 4523 - 4527 2007年06月 [査読有り][通常論文]
   

  In this study, we synthesized the C8-C20 and C21-C30 segments of the diarrhetic shellfish toxin pectenotoxin 2. The C8C20 segment was assembled from a phosphonate corresponding to the C8-C15 segment (prepared from L-malic acid in 19 steps) and an aldehyde corresponding to the C16-C20 segment (synthesized from 3-methyl-3-butenol in nine steps) by a twelve-step process including the Homer-Wadsworth-Emmons reaction, regio- and stereoselective reduction of the resulting enone, diastereoselective epoxidation, and 5-exo epoxide cleavage forming the C-ring. The C21-C30 segment was constructed in 13 steps from (S)-glycidol via a route involving E-ring formation by 5-exo epoxide cleavage and stereoselective methylation at C27 by the Evans method. (c) 2007 Elsevier Ltd. All rights reserved.
• Electrochiroptical systems based on biphenyl-2,2 '-diyl-type dicationic dyes: strong chiroptical signals through the transmission of point chirality to axial chirality

  Takanori Suzuki, Tomohiro Iwai, Eisuke Ohta, Hidetoshi Kawai, Kenshu Fujiwara

  TETRAHEDRON LETTERS 48 20 3599 - 3603 2007年05月 [査読有り][通常論文]
   

  Huge CD amplitude (A = +538) was attained by diastereomeric preference (50% de) for the title dication with two bis[4(R)-sec-butoxyphenyl]methylium units in benzene at 23 degrees C. Intramolecular pi-pi stacking is the origin for effective transmission of point chirality to axial chirality to attain the chiroptical enhancement of 400-times. Thanks to the strong CD signaling, chiroptical changes upon electrolysis could be readily detected, thus realizing a new class of clectrochiroptical response systems. Chiroptical properties could also be modified by solvent polarity. (C) 2007 Elsevier Ltd. All rights reserved.
• Chromic and fluorescence response system based on the dihydrophenanthroline-bipyridine skeleton: dynamic redox behavior and metal binding properties

  Takanori Suzuki, Ryuuichi Tamaki, Eisuke Ohta, Takashi Takeda, Hidetoshi Kawai, Kenshu Fujiwara, Masako Kato

  TETRAHEDRON LETTERS 48 22 3823 - 3827 2007年05月 [査読有り][通常論文]
   

  The spiro-acridan/acridinium-based dynamic redox pair (1/2(2+)) transduces the electrochemical input into UV-vis and fluorescence spectra, whereas the 2,2 '-bipyridine units in I works as a bidentate ligand for metal ions. X-ray structural analyses of this redox pair and the corresponding Zn-complexes [1-ZnI2/2(2+)-Zn2+(OTf-)(4)] demonstrate drastic structural changes upon electron-transfer, thus metal binding properties are modified by redox reactions. (C) 2007 Elsevier Ltd. All rights reserved.
• Dynamic redox systems as electrochromic materials: Bistability and advanced response

  Takanori Suzuki, Eisuke Ohta, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Fukushima

  SYNLETT 2007 6 851 - 869 2007年04月 [査読有り][通常論文]
   

  'Dynamic redox systems' is the name given to a certain class of compounds that can be reversibly converted into the corresponding charged species accompanied by C-C bond formation/cleavage upon electron transfer. This account details the two major motifs (hexaphenylethane derivatives and butane-1,4-diyl dications) that have been developed in the principal author's group.
• Tetraaryl-o-quinodimethanes: Reductive Generation and Severely Distorted Geometry

  Shinichi Iwashita, Takanori Suzuki

  ChemInform 38 8 2007年02月 [査読有り][通常論文]
  
• Intramolecular triarylmethane-triarylmethylium complexes with a naphthalene-1,8-diyl skeleton: Isolation, structure, and reactivities of the C-H-bridged carbocations

  Takashi Takeda, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Suzuki

  CHEMISTRY-A EUROPEAN JOURNAL 13 28 7915 - 7925 2007年 [査読有り][通常論文]
   

  Isolation and low-temperature X-ray analyses of intramolecular triarylmethane-triarylmethylium complexes with a naphthalene-1,8-diyl-type skeleton have been achieved. These bridged cations prefer a C-H localized structure both in solution and in the solid state. The bridging hydrogen undergoes a facile intramolecular 1,5-hydride shift from one carbon to another in solution. The C-H delocalized geometry is suggested to be the transition-state structure of the degenerate rearrangement. Charge-transfer interaction from the triarylmethane to the triarylmethylium units is evident in the electronic spectra. This interaction stabilizes the present cations. Low reactivity toward Bronsted acids indicates that these species are not the reaction intermediates in the acid-assisted long-bond cleavage of 1, 1,2,2-tetraarylace-naphthene derivatives.
• Multi-input-multi-output molecular response system based on dynamic redox behavior of hexaphenylethane-type electron donors with the tetrahydrophenanthrazepine skeleton: Strong chiroptical signals through the transmission of point chirality to helicity

  Takanori Suzuki, Shoko Tanaka, Hidetoshi Kawai, Kenshu Fujiwara

  CHEMISTRY-AN ASIAN JOURNAL 2 1 171 - 177 2007年 [査読有り][通常論文]
   

  The title heterocyclic donors undergo reversible C-C bond formation/cleavage upon electron transfer (dynamic redox behavior). The helical sense in both neutral and cationic states is interconvertible by facile ring flipping. The pi-type asymmetric center on the azepine nitrogen atom induces a significant degree of diasteromeric preference, thus endowing strong CD activity based on exciton coupling. Chi-roptical properties could be modified not only by redox reactions but also by heat and protonation. The present redox pairs can serve as unprecedented three-way-input (e, H+, Delta) and two-way-Output (UV/Vis, CD) response systems.
• P-61 ゴニオドミンAの合成研究(ポスター発表の部)

  藤原 憲秀, 片桐 隆廣, 仲 定太, 佐藤 大輔, 河合 英敏, 鈴木 孝紀

  天然有機化合物討論会講演要旨集 48 421 - 426 天然有機化合物討論会 2006年09月15日 

  Goniodomin A (GDA) was isolated from dinoflagellate Alexandrium hiranoi as an antifungal agent by Murakami in 1988. Later, its particular bioactivities, such as modulation of actomyosin ATPase activities, increasing the filamentous actin content of human astronoma cells, and antiangiogenic activity via inhibition of actin reorganization in endothelial cells, were found. Although its detailed NMR data and unique planer structure featured by a 32-membered macrolactone including 5- and 6-membered cyclic ethers (the A-, D- and E-ring parts), a spirocyclic acetal (the BC-ring part), and a 6-membered cyclic hemiacetal (the F-ring part) were reported, the stereochemistry of GDA was unclear. Since the complex structure and the remarkable bioactivities of GDA prompted our synthetic interest, we started the program of its total synthesis aiming at determination of absolute stereochemistry. In this presentation, synthesis and stereochemical-elucidation of the A-, DE-, and F-ring parts of GDA will be disclosed.
• P-409 Synthetic Studies on Goniodomin A

  Katagiri Takahiro, Fujiwara Kenshu, Naka Jota, Kawai Hidetoshi, Suzuki Takanori

  International Symposium on the Chemistry of Natural Products 2006 "P - 409" 天然有機化合物討論会 2006年07月23日
• P-408 Stereoselective Synthesis of the Nonanomeric Spirocyclic Acetal Part of Pectenotoxin 2

  Fujiwara Kenshu, Okano Azusa, Aki Yu-ichi, Kawamura Mariko, Murai Akio, Kawai Hidetoshi, Suzuki Takanori

  International Symposium on the Chemistry of Natural Products 2006 "P - 408" 天然有機化合物討論会 2006年07月23日
• Convergent synthesis of the common FGHI-ring part of ciguatoxins

  Ayumi Takizawa, Kenshu Fujiwara, Eriko Doi, Akio Murai, Hidetoshi Kawai, Takanori Suzuki

  TETRAHEDRON 62 31 7408 - 7435 2006年07月 [査読有り][通常論文]
   

  Convergent synthesis of the common FGHI-ring part (54) of ciguatoxins was achieved via the following key steps: (i) the Nozaki-Hiyama-Kishi reaction connecting the F-ring part (6) with the I-ring part (7); (ii) regio- and stereoselective epoxidation; (iii) the 6-exo-epoxide opening reaction forming simultaneously the H-ring and the quaternary asymmetric center at C30; (iv) inversion of the C29 stereocenter by a two-step oxidation/reduction process, where the successful inversion depended on proper management of the steric environment of the substrate; and (v) final reductive cyclization constructing the G-ring. (c) 2006 Elsevier Ltd. All rights reserved.
• Dynamic Covalently Bonded Rotaxanes Cross-Linked by Imine Bonds between the Axle and Ring: Inverse Temperature Dependence of Subunit Mobility

  Hidetoshi Kawai, Takeshi Umehara, Kenshu Fujiwara, Takashi Tsuji, Takanori Suzuki

  Angew. Chem. 118 26 4387 - 4392 2006年06月 [査読有り][通常論文]
  
• Change in conformation upon complexation of double-armed terephthalamide hosts: dynamic molecular recognition of ditopic guests with strong CD signaling

  R Katoono, H Kawai, K Fujiwara, T Suzuki

  TETRAHEDRON LETTERS 47 10 1513 - 1518 2006年03月 [査読有り][通常論文]
   

  Conformation of novel terephthalamide hosts 1 changes from anti to syn upon complexation with a bidentate guest (2 or 3). Chiral sense in the helical syn-form of the double-armed host molecules 1 is biased by the asymmetric centers on the chiral guest [(R,R)1(S,S)-2a], which can be detected by the drastic change in circular dichroism (CD) spectrum thanks to the exciton coupling of two chromophores ('arms') linked to the amide nitrogens. Asymmetric centers on the host molecule also exhibit preference for the twisting direction upon change in geometry from the anti- to syn-form. Thus, the achiral guests (2b or 3) can also be detected by modulation of CD spectrum upon complexation with the chiral host [(,R,R)-1a]. (c) 2006 Elsevier Ltd. All rights reserved.
• Dynamic covalently bonded rotaxanes cross-linked by imine bonds between the axle and ring: Inverse temperature dependence of subunit mobility

  Hidetoshi Kawai, Takeshi Umehara, Kenshu Fujiwara, Takashi Tsuji, Takanori Suzuki

  ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 45 26 4281 - 4286 2006年 [査読有り][通常論文]
  
• Synthesis of the common FGHI-ring part of ciguatoxins

  A Takizawa, K Fujiwara, E Doi, A Murai, H Kawai, T Suzuki

  TETRAHEDRON LETTERS 47 5 747 - 751 2006年01月 [査読有り][通常論文]
   

  The common FGHI-ring part (2) of ciguatoxins has been synthesized from the F- and I-ring parts (6 and 5, respectively). The Nozaki-Hiyama-Kishi coupling of 6 with 5 followed by regio- and stereoselective epoxidation at C29 and C30 afforded an epoxide (4), which was transformed into a tricyclic compound (3) corresponding to the F-HI-ring part by 6-exo-epoxide opening and the subsequent inversion of the C29 stereocenter. Reductive cyclization of 3 forming the C31-O26 bond of the G-ring successfully produced 2. (c) 2005 Elsevier Ltd. All rights reserved.
• The first stable tetraarylacenaphthenequinodimethanes exhibiting electrochromism with 'write-protect' option: preparation, highly deformed structure, and reversible interconversion with acenaphthylene-5,6-diyl dicationic dyes

  T Suzuki, S Iwashita, T Yoshino, H Kawai, K Fujiwara, M Ohkita, T Tsuji, K Ono, M Takenaka

  TETRAHEDRON LETTERS 47 4 467 - 471 2006年01月 [査読有り][通常論文]
   

  Severely deformed title quinodimethanes [1,2-bis(diarylmethylene)acenaphthenes] 1 have been designed and prepared as novel electrochromic materials, which can be reversibly interconverted with the deeply colored dicationic dyes 1(2+) with acenaphthylene-1,2-diyl skeleton. The X-ray analysis of 1 revealed that the inner two aryl groups are forced to overlap in proximity, which can account for the facile electrocyclization process to the isomer. By combination of reversible electrochemical transformation with irreversible isomerization process, the present system provides a prototype for novel molecular response systems equipped with the 'write-protect' option. (c) 2005 Elsevier Ltd. All rights reserved.
• テトラアリール‐ｏ‐キノジメタン：二電子還元による発生・単離と高度に歪んだ分子構造

  Shinichi Iwashita, Takanori Suzuki

  J. Syn. Org. Chem., Jpn. 64 9 958 - 968 The Society of Synthetic Organic Chemistry, Japan 2006年 [査読有り][通常論文]
   

  Introduction of four aryl groups on the highly reactive o-quinodimethane (o-QDM) skeleton suppresses the intermolecular reactivities. Thus, the unimolecular isomerization through electro-cyclization is the major decomposition path for title molecules. Rational design can prevent thermal isomerization of Ar4-o-QDMs. A new general procedure to generate Ar4-o-QDM has been established here that includes two-electron reduction of the corresponding dications, whose reaction conditions no longer promote electrocyclization of Ar4-o-QDM. Several derivatives of Ar4-o-QDM with the dihydrophenanthrene, dibenzoperylene, or acenaphthene skeleton were isolated for the first time, and the details on their highly strained molecular structures were investigated by low-temperature X-ray analyses. Based on the reversible interconversion between Ar4-o-QDMs and the precursor dications, they represent a new class of electrochromic redox pairs.
• Synthesis of the C42—C52 Part of Ciguatoxin CTX3C.

  Daisuke Domon, Kenshu Fujiwara, Yuko Ohtaniuchi, Akihiro Takezawa, Sayaka Takeda, Hidekazu Kawasaki, Akio Murai, Hidethoshi Kawai, Takanori Suzuki

  ChemInform 37 5 Wiley-Blackwell 2006年01月 [査読有り][通常論文]
  
• Synthesis of (+)-Laurencin via Ring Expansion of a C-Glycoside Derivative.

  Kenshu Fujiwara, Saori Yoshimoto, Ayumi Takizawa, Shin-ichiro Souma, Hirofumi Mishima, Akio Murai, Hidetoshi Kawai, Takanori Suzuki

  ChemInform 37 3 2006年01月 [査読有り][通常論文]
  
• Convergent Synthesis of the IJKLM-Ring Part of Ciguatoxin CTX3C.

  Daisuke Domon, Kenshu Fujiwara, Akio Murai, Hidethoshi Kawai, Takanori Suzuki

  ChemInform 37 5 2006年01月 [査読有り][通常論文]
  
• Exceptionally large difference in bond length among conformational isomorphs of a hexaphenylethane derivative with a dispiropyracene skeleton

  H Kawai, T Takeda, K Fujiwara, T Inabe, T Suzuki

  CRYSTAL GROWTH & DESIGN 5 6 2256 - 2260 2005年11月 [査読無し][通常論文]
   

  A large difference of 0.064(3) angstrom for a chemically equivalent C-sp(3) - C-sp(3) bond was observed among crystallographically independent molecules with different conformations (conformational isomorphs) of a hexaphenylethane derivative, dispiro[(10-methylacridan)-9,1'-pyracene-2',9"-(10-methylacridan)I (1): triclinic, P (1) over bar, a = 17.6990 angstrom, b = 18.1110 angstrom, c = 18.844(3) angstrom, alpha = 111.183(2)degrees, beta = 93.828(1)degrees, gamma = 102.130(2)degrees, V = 5438.5(14) angstrom(3), T = - 180 degrees C, Z = 8 (four independent molecules: A, N, B, and B'). While B and B' adopt the skewed conformation to reduce steric repulsion in 1, in other positions of the crystal, molecules A and X adopt the eclipsed conformation, which induces a much longer bond length [1.771(3) and 1.758(3) angstrom versus 1.712(2) and 1.707(2) angstrom].
• Synthesis of the C42–C52 part of ciguatoxin CTX3C

  Daisuke Domon, Kenshu Fujiwara, Yuko Ohtaniuchi, Akihiro Takezawa, Sayaka Takeda, Hidekazu Kawasaki, Akio Murai, Hidethoshi Kawai, Takanori Suzuki

  Tetrahedron Letters 46 48 8279 - 8283 Elsevier {BV} 2005年11月 [査読有り][通常論文]
   

  The C42-C52 part of ciguatoxin CTX3C (1) was synthesized from tri-O-acetyl D-glucal. The synthetic segment had a tetrahydropyran ring corresponding to the 'C49-reduced' L-ring of 1, designed to avoid side reactions due to acid-labile C49 acetal carbon during acidic reductive conditions planned in further synthesis toward 1. The vicinal dimethyl part at C47-C48 was constructed by a stepwise conjugate addition/methylation procedure. The C50-C52 unit was installed by Grignard addition of the C-3 unit followed by of the spirocyclic acetal. Stereoselective assembly of the C42-C44 part was achieved by Brown's asymmetric crotylboration. (c) 2005 Elsevier Ltd. All rights reserved.
• Convergent synthesis of the IJKLM-ring part of ciguatoxin CTX3C

  D Domon, K Fujiwara, A Murai, H Kawai, T Suzuki

  TETRAHEDRON LETTERS 46 48 8285 - 8288 2005年11月 [査読有り][通常論文]
   

  Convergent synthesis of the IJKLM-ring part (2) of ciguatoxin CTX3C has been achieved from the I-ring and the L-ring parts (4 and 5) in total eight steps in 27% overall yield. The carbanion derived from 4, stabilized by a dimethyldithioacetal S-oxide group, was readily reacted with aldehyde 5 to give an adduct, which was facilely transformed into the corresponding alpha,epsilon-dihydroxy ketone 3. The JK-ring formation from 3 under reductive conditions followed by oxidative M-ring cyclization efficiently led to the pentacyclic ether 2. Improved synthesis of 6, a synthetic intermediate for 4, was also established. (c) 2005 Elsevier Ltd. All rights reserved.
• Synthesis of (+)-laurencin via ring expansion of a C-glycoside derivative

  K Fujiwara, S Yoshimoto, A Takizawa, S Souma, H Mishima, A Murai, H Kawai, T Suzuki

  TETRAHEDRON LETTERS 46 40 6819 - 6822 2005年10月 [査読有り][通常論文]
   

  Laurencin was efficiently synthesized from a C-glycoside derivative based on ring expansion of the oxane part of the starting compound into an eight-membered cyclic ether via a ring-cleavage/ring-closing olefin metathesis process, stereoselective introduction of a brotno group at C4, and convergent construction of the side-chain part using a lithiated enyne unit. (c) 2005 Elsevier Ltd. All rights reserved.
• P-18 4-アルコキシ-2-トリメチルシロキシ-3-ブテンニトリル誘導体の反応と縮環状エーテル合成への応用(ポスター発表の部)

  竹村 淳志, 藤原 憲秀, 村井 章夫, 河合 英敏, 鈴木 孝紀

  天然有機化合物討論会講演要旨集 47 493 - 498 天然有機化合物討論会 2005年09月15日 

  Since trans-fused polycyclic ethers are often seen in potently bioactive natural products, such as ciguatoxin (1), they attract significant synthetic attention. So far, many approaches have been studied for their efficient construction. Among these approaches, a ring-closing olefin metathesis reaction (RCM) has now become one of the most reliable methods for the construction of medium-sized cyclic ethers. However, preparation of the precursors for RCM involves a serious difficulty of the stereoselective construction of their acyclic branched ether part. Therefore, we explored an efficient branched ether formation reaction. Here, BF_3・OEt_2 promoted site-selective reduction of 4-alkoxy-2-trimethylsilyloxy-3-butenenitrile (5), prepared through a process including intermolecular hetero-Michael reaction of a 2-butynoate ester derivative (3) with an alcohol (2), with R_3SiH or Bu_3SnH is disclosed, along with the efficient application to the synthesis of fused medium-ring ethers involving the EF-ring segment of CTX1B (1).
• Isolation and low-temperature X-ray analysis of intramolecular triarylmethane-triarylmethylium complex: Preference for a C-H-bridged unsymmetric structure exhibiting a facile 1,5-hydride shift and charge-transfer interaction

  H Kawai, T Takeda, K Fujiwara, T Suzuki

  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 127 35 12172 - 12173 2005年09月 [査読有り][通常論文]
   

  The intramolecular triarylmethane-methylium complex with an averaged C2v-symmetry was successfully generated by N-methylation of the acridine-acridan hybrid. Theoretical calculation and VT-NMR analyses in solution indicate the unsymmetric geometry for the three-center bond, which was finally confirmed crystallographically. Significant degree of CT interaction is induced through the very short C-H⋯C+ contact. Copyright © 2005 American Chemical Society.
• Synthesis of the EF-ring segment of ciguatoxin CTXIB based on novel regioselective reduction of unsaturated cyanohydrins and ring-closing olefin metathesis

  A Takemura, K Fujiwara, K Shimawaki, A Murai, H Kawai, T Suzuki

  TETRAHEDRON 61 31 7392 - 7419 2005年08月 [査読有り][通常論文]
   

  Aiming at a convergent total synthesis of ciguatoxin CTX1B, its EF-ring segment has been synthesized. During the synthesis, a novel method for the construction of branched ethers, based on regioselective reduction of gamma-alkoxy beta,gamma-unsaturated alpha-silyloxy nitriles with borontrifluoride etherate and trialkyl silane or tributyltin hydride, has been developed. Combination use of the method and ring-closing olefin metathesis successfully provided medium-sized cyclic ethers. Efficient site-selective reduction of vinyl epoxides into homoallyl alcohols has also been developed. (c) 2005 Elsevier Ltd. All rights reserved.
• Tetracyanoanthraquinodimethanes with a chiral amide group: Preparation, properties, and charge-transfer photochirogenetic reaction with 1,2-dianisylacenaphthene-1,2-diol

  T Suzuki, K Ichioka, H Higuchi, H Kawai, K Fujiwara, M Ohkita, T Tsuji, Y Takahashi

  JOURNAL OF ORGANIC CHEMISTRY 70 14 5592 - 5598 2005年07月 [査読有り][通常論文]
   

  A series of butterfly-shaped tetracyanoanthraquinodimethanes (TCNAQs) with a chiral amide auxiliary 1a-f were prepared from the corresponding anthraquinones. They are stronger acceptors than the unsubstituted derivative and undergo one-wave two-electron reduction. They form weak electron-donor-acceptor (EDA) complexes with the title pinacol 2. Upon charge-transfer excitation of these complexes, dihydro-TCNAQs 3 and 1,8-dianisoylnaphthalene 4 were efficiently formed, the latter of which is the product of a retropinacol reaction via 2(+.). Partial enantiodifferentiation of rac-2 was realized during the photoreactions with 2-[(R)-1-phenylethylcarbamoyl]-TCNAQ la in CD3CN. Thus, optically active (S,S)-(+)-pinacol 2 (12.3% ee at 54% conversion; 21.5% ee at 70% conversion) was recovered from the photolyzates. This reaction represents a new and rare example of the pseudokinetic resolution of tert-alcohol accompanied by C-C bond fission. Significant differences in the association constants for the diastereomeric EDA complexes are responsible for the observed enantiodifferentiation.
• Stereoselective synthesis of cis- and trans-2,3-disubstituted eight-membered medium-ring ethers based on Ireland–Claisen rearrangement of 3-alkoxy-2-propenyl glycolate esters and ring-closing olefin metathesis

  Kenshu Fujiwara, Akiyoshi Goto, Daisuke Sato, Hidetoshi Kawai, Takanori Suzuki

  Tetrahedron Letters 46 20 3465 - 3468 Elsevier {BV} 2005年05月 [査読有り][通常論文]
   

  A simple stereoselective synthesis of cis- and trans-2,3-disubstituted medium-sized cyclic ethers has been developed based on geometry-selective synthesis of 3-alkoxy-2-propenyl glycolate esters, Ireland-Claisen rearrangement of the glycolate esters, and ring-closing olefin metathesis. (c) 2005 Elsevier Ltd. All rights reserved.
• Stereospecific change in conformation upon complexation of an exoditopic tetraamide host with a bis(ammonium) guest: chiral recognition and strong CD signaling

  R Katoono, H Kawai, K Fujiwara, T Suzuki

  CHEMICAL COMMUNICATIONS 41 5154 - 5156 2005年 [査読有り][通常論文]
   

  Upon complexation of a rectangular-shaped achiral macro-cyclic host with chiral guests, twisting deformation occurs to induce exciton-type bisignated CD, whereas a chiral rectangular host undergoes a similar structural change only with the matching enantiomer of a chiral guest.
• Butane-1,4-diyl dications stabilized by steric factors: Electrochiroptical response systems based on reversible interconversion between dihydro[5]helicene-type electron acceptors and electron-donating 1,1′-binaphthyls

  Eisuke Ohta, Hiroki Higuchi, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Suzuki

  Organic and Biomolecular Chemistry 3 16 3024 - 3031 2005年 [査読無し][通常論文]
   

  Incorporation in the dihydro[5]helicene framework prevents deprotonation of the title dications by steric factors, thus allowing their isolation as deeply colored stable salts. Based on the reversible interconversion with the electron-donating binaphthylic diolefins, they constitute a new class of electrochromic systems, in which C-C bond making/breaking is accompanied by two-electron transfer. Optically pure (R)-binaphthylic donors are interconvertible with the 1,4-dications with the R,R-configuration. The very large molar ellipticity makes it possible for them to be used as electrochiroptical response systems, by which the electrochemical input is transduced into two spectral outputs, i.e. UV-Vis and circular dichroism. Structurally related push-pull-type bis(quinonemethide)s also exhibit a similar multi-output electrochemical response. © The Royal Society of Chemistry 2005.
• Synthesis of the common left-half part of pectenotoxins

  Fujiwara, K., Kobayashi, M., Yamamoto, F., Aki, Y.-I., Kawamura, M., Awakura, D., Amano, S., Okano, A., Murai, A., Kawai, H., Suzuki, T.

  Tetrahedron Letters 46 30 5067 - 5069 2005年 [査読有り][通常論文]
  
• Multipoint recognition of catecholamines by hydrindacene-based receptors accompanied by the complexation-induced conformational switching

  H Kawai, R Katoono, K Fujiwara, T Tsuji, T Suzuki

  CHEMISTRY-A EUROPEAN JOURNAL 11 3 815 - 824 2005年01月 [査読有り][通常論文]
   

  The molecular recognition of catecholamines by hydrindacene-based receptors 1 and 2, as well as the durene-based receptor 3, and the guest-induced conformational changes are reported. These receptors selectively bind adrenaline and dopamine salts through the guests' ammonium group and 3-hydroxyl group on the aromatic ring. In the case of adrenaline, an additional hydrogen bond with a benzylic hydroxyl group is formed. In 2% CD3CN/CDCl3, the association constants are of the order of 10(4)m(-1), which is much larger than with guests without the 3-hydroxyl groups (10(3)m(-1)). The two amide groups of receptor 1 can rotate freely around the C-aromatic-C-amide bond, whereas the tert-amide in 2 changes between two stable conformations at a slow enough rate to allow detection by H-1 NMR spectroscopy. In the absence of a guest molecule, the syn-conformer is less stable than the anti-conformer. On complex formation with adrenaline, the syn-conformer becomes dominant due to an intramolecular dipole-reversal effect in addition to multipoint hydrogen bonding.
• Short nonbond and long C-C bond in naphthalene-1,8-diylbis(10-methylacridinium) and the corresponding hexaphenylethane derivative: a new electrochromic pair exhibiting dynamic redox properties

  H Kawai, T Takeda, K Fujiwara, T Suzuki

  TETRAHEDRON LETTERS 45 45 8289 - 8293 2004年11月 [査読有り][通常論文]
   

  The extremely long C-C bond [1.696(3) Angstrom] in the colorless dispiroacenaphthene-type hexaphenylethane is cleaved readily upon electrochemical transformation into the orange colored naphthalene-1,8-diylbis(acridinium), in which the two cationic units are forced to overlap in a face-to-face manner exhibiting the shortest C+...C+ interatomic contact of 2.927(7) Angstrom among the values ever reported. (C) 2004 Elsevier Ltd. All rights reserved.
• Dynamic redox systems based on bis(spiroxanthene)-type donors with a polycyclic aromatic hydrocarbon: preparation, X-ray structures, and electrochromic response with fluorescence change

  T Suzuki, S Tanaka, H Higuchi, H Kawai, K Fujiwara

  TETRAHEDRON LETTERS 45 46 8563 - 8567 2004年11月 [査読有り][通常論文]
   

  The long C-C bonds (1.614(2)-1.630(2) Angstrom) in newly prepared title donors 2-6 are cleaved upon two-electron oxidation to afford the bond-dissociated dicationic dyes 2(2+)-6(2+), whose electron affinities are stronger than the corresponding biphenyl-2,2'-diyl dications 1(2+) due to the spatial proximity of two xanthenylium units. Not only UV-vis but also fluorescence spectra changed drastically upon electrolysis since only colorless neutral donors are fluorescent. (C) 2004 Elsevier Ltd. All rights reserved.
• [10]Paracyclophanediamides and their octadehydro derivatives: novel exotopic receptors with hydrogen-bonding sites on the bridge

  R Katoono, H Kawai, K Fujiwara, T Suzuki

  TETRAHEDRON LETTERS 45 46 8455 - 8459 2004年11月 [査読有り][通常論文]
   

  2,9-Diaza-1,10-dioxo[10]paracyclophanes were prepared in short steps from the terephthaloyl chlorides via the corresponding 4,6-diyne derivatives, and the amide groups on the bridge endow the skeleton with the guest-binding properties as demonstrated by complexation with adrenaline by hydrogen bonds. The chiral auxiliaries on the bridge induce diastereomeric preference in terms of the planar chirality for the octadehydro derivative with a rigid diyne unit in crystal. (C) 2004 Elsevier Ltd. All rights reserved.
• 102(P-38) シガトキシンCTX3CのABCDE環部の収束合成(ポスター発表の部)

  藤原 憲秀, 後藤 研由, 佐藤 大輔, 大谷内 裕子, 田中 秀輝, 村井 章夫, 河合 英敏, 鈴木 孝紀

  天然有機化合物討論会講演要旨集 46 587 - 591 天然有機化合物討論会 2004年10月01日 

  CTX3C (1) was isolated as congener of ciguatoxin (CTX) from cultured dinoflagellate Gambierdiscus toxicus by the Yasumoto group. Its unique ladder-shaped trans-fused polycyclic structure possessing 13 ether rings is a synthetic challenge and has attracted the attention of synthetic chemists. During the course of our studies directed toward CTXs, we achieved the syntheses of their individual medium ring parts and developed a convergent method for the construction of their X/6/7/X ring systems. Here, we disclose alternative successful convergent construction of the ABCDE ring system 2 of 1 from the AB- and E-ring segments (5 and 6, respectively). Previously, effective convergent method applying coupling reaction of an acyl anion equivalent with an aldehyde followed by reductive cyclization reactions was developed for the synthesis of trans-fused tetracyclic ethers in this laboratory. Therefore, dimethyldithioacetal mono-S-oxide 5 and aldehyde 6 were selected as AB-and E-ring segments, respectively, in our synthetic plan for 1. The segment 5 was prepared in 16 steps from 7 in 12% total yield. The aldehyde 6 was synthesized in 20 steps from 16 in 38% total yield. Coupling reaction of deprotonated 5 with 6 followed by simultaneous removal of TBS and dithioacetal groups afforded ketodiol 4, which was subjected to reductive cyclization and the subsequent oxidation and deprotection to give 3. Hydroxy ketone 3 was efficiently cyclized into pentacyclic ether 35 under the similar reductive conditions as the cyclization of 4. Treatment of 35 with an excess amount of LDBB induced not only benzyl group detachment but also conversion of the PBBO group to a BnO group to produce 2 successfully. Thus, the ABCDE-ring part 2 was efficiently constructed in 10 steps from 6 in 11% total yield.
• Novel branched ether formation via conjugate reduction of an unsaturated cyanohydrin derivative and its synthetic application to the EF-ring segment of ciguatoxin

  A Takemura, K Fujiwara, A Murai, H Kawai, T Suzuki

  TETRAHEDRON LETTERS 45 41 7567 - 7571 2004年10月 [査読有り][通常論文]
   

  A synthetic method for a branched ether system was developed. The method was based on Lewis-acid-promoted gamma-position selective reduction of a gamma-alkoxy beta,gamma-unsaturated alpha-silyloxy nitrile, prepared through a process including intermolecular hetero-Michael reaction of a 2-butynoate ester derivative with an alcohol. The method was efficiently applied to the synthesis of fused medium-ring ethers involving the EF-ring segment (2) of ciguatoxin (1). (C) 2004 Elsevier Ltd. All rights reserved.
• Formal Total Synthesis of Hemibrevetoxin B by a Convergent Strategy.

  Kenshu Fujiwara, Daisuke Sato, Manabu Watanabe, Hiroshi Morishita, Akio Murai, Hidetoshi Kawai, Takanori Suzuki

  ChemInform 35 43 2004年10月 [査読有り][通常論文]
  
• Convergent synthesis of the ABCDE-ring part of ciguatoxin CTX3C

  K Fujiwara, A Goto, D Sato, Y Ohtaniuchi, H Tanaka, A Murai, H Kawai, T Suzuki

  TETRAHEDRON LETTERS 45 38 7011 - 7014 2004年09月 [査読有り][通常論文]
   

  Convergent synthesis of the ABCDE-ring part (2) of ciguatoxin CTX3C (1) has been achieved. A carbanion stabilized by a dimethyldithioacetal S-oxide group in the AB-ring part (4) readily reacted with an aldehyde group in the E-ring part (5). The resulting adduct was facilely converted to the corresponding beta,gamma-unsaturated alpha,epsilon-dihydroxy ketone (3). The subsequent reductive hydroxy-ketone-cyclization reactions constructed the CD-ring part efficiently. Thus, the ABCDE-ring part (2) was concisely synthesized in 10 steps in 11% overall yield from the AB-ring and the E-ring parts (4 and 5). (C) 2004 Elsevier Ltd. All rights reserved.
• Synthesis and characterization of hexakis(4-pyridylethynyl)benzene and hexakis(5-pyrimidylethynyl)benzene

  M Ohkita, C Adachi, M Kawano, T Suzuki

  HETEROCYCLES 63 7 1537 - 1540 2004年07月 [査読有り][通常論文]
   

  Two new members of snowflake-shaped carbon-rich molecules possessing nitrogen-heterocycles as functional end groups, hexakis(4-pyridylethynyl)benzene (1) and hexakis(5-pyrimidylethynyl)benzene (2), have been prepared by six-fold Sonogashira cross-coupling reaction of hexabromobenzene with 4-ethynylpyridine and 5-ethynylpyrimidine, respectively.
• Formal total synthesis of hemibrevetoxin B by a convergent strategy

  K Fujiwara, D Sato, M Watanabe, H Morishita, A Murai, H Kawai, T Suzuki

  TETRAHEDRON LETTERS 45 27 5243 - 5246 2004年06月 [査読有り][通常論文]
   

  Concise construction of the trans-fused 7/7/6/6 tetracyclic ether part of hemibrevetoxin B (1) was achieved by a convergent strategy based on coupling reaction of an acyl anion equivalent, reductive cyclization of an alpha,epsilon-dihydroxyketone, and introduction of a methyl group at the central ring junction by the Nicolaou method. The resultant tetracyclic ether was transformed into the known intermediate, which was already converted to 1 by the Yamamoto group, thereby completing the formal total synthesis of 1. (C) 2004 Elsevier Ltd. All rights reserved.
• peri-Interaction between diarylmethyl and diarylmethylium units in 1,8-disubstituted naphthalenes: preference of localized structure for the C-H bridged carbocation

  H Kawai, T Nagasu, T Takeda, K Fujiwara, T Tsuji, M Ohkita, JI Nishida, T Suzuki

  TETRAHEDRON LETTERS 45 23 4553 - 4558 2004年05月 [査読有り][通常論文]
   

  (8-Diarylmethyl-1-naphthyl)bis(4-dimethylaminophenyl)methyliums (aryl=C6H5, 4-IC6H4, and 4-MeOC6H4) were generated by hydride shift from (4-dimethylaminophenyl)methyl group to the diarylmethylium unit at peri-positions of naphthalene. Successful isolation and low-temperature X-ray analysis indicated that they are novel C-H bridged carbocations, which prefer the localized structure with a short contact of C-H... C+ rather than the delocalized one with a three-centered-two-electron bond of (C... H...C)+. (C) 2004 Elsevier Ltd. All rights reserved.
• Three-way-output response system by electric potential: UV-vis, CD, and fluorescence spectral changes upon electrolysis of the chiral ester of tetracyanoanthraquinodimethane

  H Higuchi, K Ichioka, H Kawai, K Fujiwara, M Ohkita, T Tsuji, T Suzuki

  TETRAHEDRON LETTERS 45 15 3027 - 3030 2004年04月 [査読有り][通常論文]
   

  The newly prepared tetracyanoanthraquinodimethane (TCNAQ) derivatives 1a,b with a chiral auxiliary are good electron acceptors and exhibit weak circular dichroism (CD) based on the absorption of TCNAQ. The twin-type electron acceptor 1c with two TCNAQ units shows larger ellipticity by exciton coupling. UV-vis, CD, and fluorescence spectra were changed drastically upon electrochemical reduction of 1c, which demonstrates the unprecedented three-way-output response system. (C) 2004 Elsevier Ltd. All rights reserved.
• Positive Homotropic Allosteric Binding of Benzenediols in a Hydrindacene-Based Exoditopic Receptor:  Cooperativity in Amide Hydrogen Bonding

  Hidetoshi Kawai, Ryo Katoono, Kouki Nishimura, Shunsuke Matsuda, Kenshu Fujiwara, Takashi Tsuji, Takanori Suzuki

  J. Am. Chem. Soc. 126 16 5034 - 5035 American Chemical Society ({ACS}) 2004年04月 [査読有り][通常論文]
  
• Pyrazino-tetracyanonaphthoquinodimethanes: sterically deformed electron acceptors affording zwitterionic radicals

  T Suzuki, S Miyanari, H Kawai, K Fujiwara, T Fukushima, T Miyashi, Y Yamashita

  TETRAHEDRON 60 9 1997 - 2003 2004年02月 [査読有り][通常論文]
   

  The X-ray analyses of the title electron acceptors (1) revealed their butterfly-shaped deformed geometry, which is not affected by the pyridyl group attached at 2-position of the pyrazino-TCNNQ skeleton. Small differences between the first and second reduction potentials (ca. 0.1 V) in pyrazino-TCNNQs show that their anion radicals (1(-.)) are prone to disproportionate into the neutral (1) and dianionic (1(2-)) species. The thermodynamically unstable anion radical species based on the pyrazino-TCNNQ skeleton could be isolated as inner salts upon electrochemical reduction of the derivatives having an N-methylpyridinium moiety at 2-position (2(+)). The zwitterionic open-shell species (2) constitute a novel class of radicals that exhibit semiconducting behavior as a single component thanks to the high electrochemical amphotericity. (C) 2004 Elsevier Ltd. All rights reserved.
• Preparation, properties, and X-ray structures of 5,5′-bi(8- aminoquinoxalyl)s: Novel Wurster-type electron donors with a heterobiaryl skeleton

  Takanori Suzuki, Mayu Saito, Hidetoshi Kawai, Kenshu Fujiwara, Takashi Tsuji

  Tetrahedron Letters 45 2 329 - 333 Elsevier {BV} 2004年01月 [査読有り][通常論文]
   

  The title electron donors were prepared by the double condensation reactions of 2,2′,3,3′-tetraamino-4,4′-bis(1-pyrrolidinyl) biphenyl with 1,2-diketones. They adopt twisted conformations in crystal, yet the reversible two-stage one-electron oxidation process suggests the planar geometries for the oxidized species. Depending on the nature of substituents on the pyrazine ring, this π-system can be endowed additional features such as chiroptical properties or metal coordination ability. © 2003 Elsevier Ltd. All rights reserved.
• First stable 7,7,8,8-tetraaryl-o-quinodimethane: isolation, X-ray structure, electrochromic response of 9,10-bis(dianisylmethylene)-9,10-dihydrophenanthrene

  S Iwashita, E Ohta, H Higuchi, H Kawai, K Fujiwara, K Ono, M Takanaka, T Suzuki

  CHEMICAL COMMUNICATIONS 10 18 2076 - 2077 2004年 [査読有り][通常論文]
   

  Oxidative cyclization of 2,2'-bis(dianisylethenyl) biphenyl yielded the dicationic salt of phenanthrene-9,10-diylbis( dianisylmethylium), which in turn afforded the severely congested title molecule as the first stable tetraaryl-o-quinodimethane derivative upon reduction.
• Kinetic stabilization of the o-quinoidal 3,4-benzotropone system

  M Ohkita, K Sano, K Ono, K Saito, T Suzuki, T Tsuji

  ORGANIC & BIOMOLECULAR CHEMISTRY 2 17 2421 - 2425 2004年 [査読有り][通常論文]
   

  Kinetic stabilization of the o-quinoidal 3,4-benzotropone system was investigated. The parent 3,4-benzotropone 1 undergoes rapid [pi8+pi10] dimerization in fluid solution even at -78degreesC while triptycene-fused derivative 5 having a tert-butyl group at the C(6) position of the tropone moiety was found to be stable indefinitely under similar conditions. The relative importance of the triptycene moiety and the tert-butyl group in 5 for the kinetic stabilization was evaluated.
• pi-extended o-quinoidal tropone derivatives: experimental and theoretical studies of naphtho[2,3-c]tropone and anthro[2,3-c]tropone

  M Ohkita, K Sano, T Suzuki, T Tsuji, T Sato, H Niino

  ORGANIC & BIOMOLECULAR CHEMISTRY 2 7 1044 - 1050 2004年 [査読有り][通常論文]
   

  pi-Extended o-quinoidal tropone derivatives, naphtho[2,3-c] tropone (3) and anthro[2,3-c] tropone (4), have been investigated theoretically as well as experimentally. The geometrical optimization of 3, 4, and related compounds at the B3LYP level employing 6-31G* basis set as well as the GIAO calculations at the RHF level employing the 6-31+G* basis set have been performed to evaluate the contributions of the polarized resonance forms to these molecules. The GIAO calculated NICS(1) values indicate that the aromaticities of the tropone rings of o-quinoidal 3 and 4 are significantly increased as compared with that of parent tropone (1) at the expense of the fused benzenoid rings, consistent with the significant electronic polarization of these molecules in the ground state. On the other hand, the fusion of a benzene or naphthalene ring to the 2,3- or 4,5-position of tropone leads to diminution of aromaticity in the resulting tropone moiety. Experimentally, irradiation of 6,7-(2', 3'-naphtho) bicyclo[3.2.0] hepta-3,6-dien-2-one (10) in a rigid glass at - 196 degreesC leads to the formation of 3, which exhibits a characteristic UV-Vis absorption extending to 700 nm and undergoes rapid [pi12 + pi14] dimerization upon thawing the glass. In contrast, 6,7-(2', 3'-anthro) bicyclo[3.2.0] hepta-3,6-dien-2-one (11) showed no sign of isomerization to 4 under the same reaction conditions.
• First stable 7,7,8,8-tetraaryl-o-quinodimethane: isolation, X-ray structure, electrochromic response of 9,10-bis(dianisylmethylene)-9,10-dihydrophenanthrene

  S Iwashita, E Ohta, H Higuchi, H Kawai, K Fujiwara, K Ono, M Takanaka, T Suzuki

  CHEMICAL COMMUNICATIONS 36 18 2076 - 2077 2004年 [査読有り][通常論文]
   

  Oxidative cyclization of 2,2'-bis(dianisylethenyl) biphenyl yielded the dicationic salt of phenanthrene-9,10-diylbis( dianisylmethylium), which in turn afforded the severely congested title molecule as the first stable tetraaryl-o-quinodimethane derivative upon reduction.
• Synthesis of the tricyclic dihydrofuran moiety of azadirachtin: efficient transformation of the Claisen rearrangement intermediate into a functionalized tricyclic dihydrofuran core

  J Ishihara, Y Ikuma, S Hatakeyama, T Suzuki, A Murai

  TETRAHEDRON 59 51 10287 - 10294 2003年12月 [査読有り][通常論文]
   

  Azadirachtin is a C-seco, limonoid, derived from the neem tree. Previously, we reported the synthesis of the right and left segments of azadirachtin, in addition to the coupling reaction of the modeled ester utilizing Claisen rearrangement. Herein we report the transformation of the modeled rearrangement product into a tricyclic dihydrofuran, which would be expected to have bioactivity against insects. (C) 2003 Elsevier Ltd. All rights reserved.
• 4,7-bis(dimethylamino)benzimidazoles and twin-type derivatives: reversible two-stage redox system modulated by proton-transfer

  T Suzuki, Y Tsubata, Y Obana, T Fukushima, T Miyashi, M Saito, H Kawai, K Fujiwara, K Akiyama

  TETRAHEDRON LETTERS 44 43 7881 - 7884 2003年10月 [査読無し][通常論文]
   

  The title electron donors 1 as well as their conjugate bases 2(-) undergo reversible two-stage one-electron oxidation. ESR analysis indicated the important contribution of zwitterionic structure for radicals 2(.). Bis(zwitterionic) but not quinoid structure was suggested for p-4, generated from the twin-type dianionic donor P-4(2-) with a p-phenylene spacer. (C) 2003 Elsevier Ltd. All rights reserved.
• 95(P-26) ヘミブレベトキシンBの収束的全合成研究(ポスター発表の部)

  藤原 憲秀, 渡邊 学, 佐藤 大輔, 森下 大司, 村井 章夫, 鈴木 孝紀

  天然有機化合物討論会講演要旨集 45 561 - 566 天然有機化合物討論会 2003年09月01日 

  Hemibrevetoxin B (1), isolated from the red tide dinoflagellate Gymnodinium breve by Shimizu group, is a trans-fused tetracyclic ether. To date, many research groups reported total synthesis of 1. Notably, most of them adopted a linear strategy, though a convergent strategy would have comparable efficiency with linear one even in the synthesis of such small polyether. In this context, we planned to synthesize 1 through a convergent strategy that would allow the large-scale preparation. During our studies, Holton group reported first convergent total synthesis of 1 very recently, where the ABCD ring part was constructed in 15 steps after connection of the cyclic A-ring part with the acyclic C12-C21 (BCD-ring) segment. Here, we disclose alternate successful convergent construction of the ABCD ring system 2 of 1 from the A- and D-ring segments (5 and 6, respectively). Previously, we developed an effective convergent method for the synthesis of trans-fused tetracyclic ethers adopting coupling reaction of an acyl anion equivalent with an aldehyde followed by reductive cyclization reactions. Therefore, dimethyldithioacetal mono-S-oxide 5 and aldehyde 6 were selected as A- and D-ring segments, respectively, in our synthetic plan for 1. The segment 5 was prepared in 14 steps from 2,4,6-tri-O-acetyl-D-glucal 7 in 14% total yield. The aldehyde 6 was synthesized in 19 steps from γ-butyrolactone 14 in 11% total yield. Coupling reaction of deprotonated 5 with 6 followed by simultaneous removal of TBS and dithioacetal groups afforded ketodiol 4, which was subjected to reductive cyclization, oxidation, and deprotection to give 3. Formation of cyclic S,O-acetal 34 from 3 followed by oxidation with mCPBA and in situ treatment with AlMe_3 produced tetracyclic 2. Thus, the ABCD-ring part 2 was successfully constructed in 7 steps from 6 in 12% total yield.
• A novel redox switch for fluorescence: drastic UV–vis and fluorescence spectral changes upon electrolysis of a hexaphenylethane derivative of 10,10′-dimethylbiacridan

  Takanori Suzuki, Akira Migita, Hiroki Higuchi, Hidetoshi Kawai, Kenshu Fujiwara, Takashi Tsuji

  Tetrahedron Letters 44 36 6837 - 6840 Elsevier {BV} 2003年09月 [査読有り][通常論文]
   

  The newly prepared title donor 1 has a very long C-C bond [1.635(2) Angstrom], which was readily cleaved upon oxidation to. give dication 2(2+) containing two 10-methylacridinium chromophores. Colorless donor 1 (E-ox +0.18 V) is non-fluorescent whereas orange dication 2(2+) (E-red -0.27 V) emits strong green fluorescence, so that, this pair can be considered as a novel redox switch for fluorescence with high electrochemical bistability. (C) 2003 Elsevier Ltd. All rights reserved.
• A novel redox switch for fluorescence: drastic UV–vis and fluorescence spectral changes upon electrolysis of a hexaphenylethane derivative of 10,10′-dimethylbiacridan

  Takanori Suzuki, Akira Migita, Hiroki Higuchi, Hidetoshi Kawai, Kenshu Fujiwara, Takashi Tsuji

  Tetrahedron Letters 44 36 6837 - 6840 Elsevier {BV} 2003年09月 [査読有り][通常論文]
   

  The newly prepared title donor 1 has a very long C-C bond [1.635(2) Å], which was readily cleaved upon oxidation to give dication 2 2+ containing two 10-methylacridinium chromophores. Colorless donor 1 (Eox +0.18 V) is non-fluorescent whereas orange dication 2 2+ (Ered -0.27 V) emits strong green fluorescence, so that, this pair can be considered as a novel redox switch for fluorescence with high electrochemical bistability. © 2003 Elsevier Ltd. All rights reserved.
• Electrochiroptical response of 2,2′-(2,2-diarylethenyl)binaphthyl-type electron donors that undergo reversible C-C bond formation/breaking upon two-electron transfer

  Hiroki Higuchi, Eisuke Ohta, Hidetoshi Kawai, Kenshu Fujiwara, Takashi Tsuji, Takanori Suzuki

  Journal of Organic Chemistry 68 17 6605 - 6610 American Chemical Society ({ACS}) 2003年08月 [査読有り][通常論文]
   

  2,2′-[2,2-Bis(4-dimethylaminophenyl)ethenyl]biphenyl (1) is a strong electron donor that undergoes oxidative C-C bond formation to give a stable dication rac-22+, the 9,10-dihydrophenanthrene derivative substituted with two bis(4-dimethylaminophenyl)methylium chromophores. This dication salt regenerates the starting diolefin 1 by reductive C-C bond breaking, thus realizing a new electrochromic system with high electrochemical bistability and a vivid change in color from yellow to deep blue. Similarly, the binaphthylic diolefin rac-3 and the helicene-type dication rac-4 2+ are interconvertible upon two-electron transfer. Both the UV-vis and CD spectra changed drastically upon electrochemical transformation between optically pure 3 and 42+, which represents a new electrochiroptical system.
• Formation of keto-carbeniums from 1,2,2-triarylacenaphthen-1-ols by breaking a long CC bond: unusual alcohol protonolysis accompanied by formal hydride abstraction

  Takanori Suzuki, Takayuki Nagasu, Hidetoshi Kawai, Kenshu Fujiwara, Takashi Tsuji

  Tetrahedron Letters 44 32 6095 - 6098 Elsevier {BV} 2003年08月 [査読有り][通常論文]
   

  Oxidation of 1,2,2-tris(4-dimethylaminophenyl)- and 2,2-bis(4-dimethylaminophenyl)-1-phenylacenaphthen-1-ols 1a,b with I-2 induced the C-1-C-2 bond fission to give 8-aroylnaphthalen-1-yl-bis(4-dimethylaminophenyl)carbenium derivatives 2a,b(+), the intramolecular Lewis acid-base pairs. Treatment of 1 with HBF4 did not induce the expected C-OH bond heterolysis but caused fission of CO-H and C-1-C-2 bonds to give exactly the same carbenium 2(+). (C) 2003 Elsevier Ltd. All rights reserved.
• Formation of keto-carbeniums from 1,2,2-triarylacenaphthen-1-ols by breaking a long CC bond: unusual alcohol protonolysis accompanied by formal hydride abstraction

  Takanori Suzuki, Takayuki Nagasu, Hidetoshi Kawai, Kenshu Fujiwara, Takashi Tsuji

  Tetrahedron Letters 44 32 6095 - 6098 Elsevier {BV} 2003年08月 [査読有り][通常論文]
   

  Oxidation of 1,2,2-tris(4-dimethylaminophenyl)- and 2,2-bis(4-dimethylaminophenyl)-1-phenylacenaphthen-1-ols 1a,b with I2 induced the C1-C2 bond fission to give 8-aroylnaphthalen-1-yl-bis(4-dimethylaminophenyl)carbenium derivatives 2a,b+, the intramolecular Lewis acid-base pairs. Treatment of 1 with HBF4 did not induce the expected C-OH bond heterolysis but caused fission of CO-H and C1-C2 bonds to give exactly the same carbenium 2+. © 2003 Elsevier Ltd. All rights reserved.
• Dynamic Redox Systems: Toward the Realization of Unimolecular Memory

  Takanori Suzuki, Hiroki Higuchi, Takashi Tsuji, Jun-ichi Nishida, Yoshiro Yamashita, Tsutomu Miyashi

  ChemInform 34 23 2003年06月10日 [査読有り][通常論文]
  
• Chiral electron donors and acceptors: novel "electrochiroptical" response

  T Suzuki, J Nishida, E Hirota, M Ohkita, T Tsuji

  SYNTHETIC METALS 133 357 - 358 2003年03月 [査読無し][通常論文]
   

  The electrochiroptical systems are a new type of transducers that transform the electrochemical input into the UV-Vis as well as chiroptical outputs. Several previous examples are briefly reviewed. The new concept to realize the drastic chiroptical response is proposed. (C) 2002 Elsevier Science B.V. All rights reserved.
• Dynamic redox systems: Toward the realization of unimolecular memory

  Suzuki, T., Higuchi, H., Tsuji, T., Nishida, J.-I., Yamashita, Y., Miyashi, T.

  Springer Series in Chemical Physics 70 3 - 24 2003年01月22日 [査読有り][通常論文]
   

  "Dynamic redox systems" is the name given to a certain class of compounds that can be reversibly converted into the corresponding charged species upon electron transfer (ET) but accompanied by drastic structural changes and/or covalent bond making/breaking. Although transformation between the neutral and charged species proceeds quantitatively in most cases, their electrochemical processes are irreversible owing to the chemical reactions followed by ET. This situation endows the "dynamic redox pairs" with very high bistability, which is a prerequisite in order to construct the molecular response systems. This chapter first describes the principle of the "dynamic redox properties", and then classifies the compounds into several categories from the viewpoint of the type of structrual changes. After the properties of representative molecules in each category have been described in detail, their expected use as unimolecular devices is commented on in the final part of the chapter.
• Suzuki, T.; Higuchi, H.; Tsuji, T.; Nishida, J.; Yamashita, Y.; Miyashi, T.: Dynamic Redox Systems: Toward the Realization of Unimolecular Memory, 3-24 (Nakamura, T.; Matsumoto, T.; Tada, H.; Sugiura, K. "Chemistry of Nanomolecular Systems", Springer, ・・・

  2003年 [査読無し][通常論文]
   

  Suzuki, T.; Higuchi, H.; Tsuji, T.; Nishida, J.; Yamashita, Y.; Miyashi, T.: Dynamic Redox Systems: Toward the Realization of Unimolecular Memory, 3-24 (Nakamura, T.; Matsumoto, T.; Tada, H.; Sugiura, K. "Chemistry of Nanomolecular Systems", Springer, Berlin) (2003)
• Functionalization and kinetic stabilization of the [4]paracyclophane system and aromaticity of its extremely bent benzene ring

  T Tsuji, M Okuyama, M Ohkita, H Kawai, T Suzuki

  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 125 4 951 - 961 2003年01月 [査読有り][通常論文]
   

  Kinetic stabilization of the [4]paracyclophane skeleton by the introduction of substituents, which serve to sterically hinder reactions at the reactive bridgehead sites, and properties of the resultant [4]paracyclophanes are investigated in this study. Modification of the property of [4]paracyclophane by functionalization is also intended. [4]Paracyclophanes are designed to be derived from the corresponding Dewar benzene isomers via their photochemical aromatization, and the requisite 1,4-bridged Dewar benzenes bearing sterically demanding functional groups are prepared. Irradiation of these precursors under matrix isolation at 77 K leads to the formation of [4)paracyclophanes, which exhibit characteristic electronic absorption spectra. The half-lives of the generated species vary widely from less than 1 min at -90 degreesC to 0.5 h at -20 degreesC, depending on the type of substituents and the pattern of substitution. One of the derivatives, 24, is stable enough and its content in the irradiated mixture is high enough to permit the measurement of the H-1 NMR spectrum. The recorded spectrum, which is reproduced very well by theoretical calculations using the GIAO method at the hybrid HF-DFT (B3LYP/6-31+G*) level, suggests the sustenance of rather strong diatropicity in its severely bent benzene moiety. Calculations on the bent benzene whose geometry is constrained to that calculated for 24 support that aromaticity is retained to a significant extent as compared to that of planar benzene, as judged by the magnetic criteria of aromaticity, that is, diamagnetic susceptibility exaltation and nucleus-in dependent chemical shift. The reason for the retention of aromaticity despite the severe bending of the benzene ring is discussed. Cyclophane 24 is so strained that it exceeds the corresponding Dewar benzene precursor in energy and thermally reverts to the latter with a half-life of 15 +/- 5 min at -20 degreesC (DeltaG(double dagger) = 18.3 +/- 0.3 kcal mol(-1)).
• Electrochiroptical response of a hexaarylethane derivative with a helical ??-skeleton: drastic UV???Vis and CD spectral changes upon electrolysis of 4???,5???-dibromodispiro[xanthene-9,9???(9???H,10???H)-phenanthrene-10???,9???-xanthene]

  Takanori Suzuki, Rie Yamamoto, Hiroki Higuchi, Erika Hirota, Masakazu Ohkita, Takashi Tsuji

  J. Chem. Soc., Perkin Trans. 2 11 1937 - 1942 2002年10月03日 [査読有り][通常論文]
   

  Upon two-electron oxidation of the title electron donor 1a, the elongated central C9-C10 bond [1.656(5) Å (X-ray)] is cleaved to give the biphenyl-2,2′-diyl bis(xanthenylium) dye 2a+2, which regenerates the colorless dispiro compound 1a by two-electron reduction. The presence of isosbestic points in the UV-Vis spectra during the electrochemical oxidation of 1a to 2a+2 indicates the negligible steady-state concentration of the intermediate cation radical. Interconversion between optically resolved 1a and 2a+2 is accompanied by drastic changes in the CD spectra again with several isosbestic points, and racemization of (P)- and (M)-1a and (S)- and (R)-2a+2 does not occur at ambient conditions. This redox pair represents a new motif for the multi-output response system, where the electrochemical input is transduced into two independent spectral outputs.
• ChemInform Abstract: A Novel Class of Molecular Response Systems Based on Hexaphenylethane-Type Electron Donors

  Jun-ichi Nishida, Takanori Suzuki, Takashi Tsuji

  ChemInform 33 26 no - no 2002年07月02日 [査読有り][通常論文]
  
• Electrochiroptical response of a hexaarylethane derivative with a helical pi-skeleton: drastic UV-Vis and CD spectral changes upon electrolysis of 4 ',5 '-dibromodispiro[xanthene-9,9 '(9 ' H, 10 ' H)-phenanthrene-10 ',9 ''-xanthene]

  T Suzuki, R Yamamoto, H Higuchi, E Hirota, M Ohkita, T Tsuji

  JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2 11 1937 - 1942 2002年 [査読有り][通常論文]
   

  Upon two- electron oxidation of the title electron donor 1a, the elongated central C-9-C-10 bond [1.656(5) Angstrom(X-ray)] is cleaved to give the biphenyl-2,2'-diyl bis( xanthenylium) dye 2a(2+), which regenerates the colorless dispiro compound 1a by two- electron reduction. The presence of isosbestic points in the UV- Vis spectra during the electrochemical oxidation of 1a to 2a(2+) indicates the negligible steady- state concentration of the intermediate cation radical. Interconversion between optically resolved 1a and 2a(2+) is accompanied by drastic changes in the CD spectra again with several isosbestic points, and racemization of (P)- and (M)- 1a and (S)- and (R)- 2a(2+) does not occur at ambient conditions. This redox pair represents a new motif for the multi- output response system, where the electrochemical input is transduced into two independent spectral outputs.
• A novel class of molecular response systems based on hexaphenylethane-type electron donors

  J Nishida, T Suzuki, T Tsuji

  JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN 60 1 40 - 51 2002年01月 [査読有り][通常論文]
   

  Redox reactions of a series of dicationic dyes (2(2+), 4(2+), 6(2+)) having two triarylmethylenium chromophores were studied, which are interconvertible with colorless hexaarylethane derivatives (1, 3) or 9-membered cyclic peroxides (5), respectively, upon two-electron transfer. They constitute a new class of electrochromic systems endowed with high electrochemical bistability since the reversible bond making/breaking causes the drastic changes in the geometrical and electronic structures of the redox pairs. Bond dissociated cation radical 2(+.) is the stable intermediate for the interconversion between I and 2(2+), and the unprecedented tricolor chromic systems showing a hysteretic color change were constructed based on 1, 2(+.), and 2(2+). Drastic change in CD spectrum was observed during the interconversion between chiral helicenes 3 and binaplithylic dications 4(2+), which is the successful demonstration of electrochiroptical response. Peroxides 5 were readily obtained by two-electron reduction of dications 6(2+) under air. Since 6(2+) were regenerated by the "oxidative deoxygenation" reaction of 5, these pairs can serve as a electrochemically controlled oxygen-storage system.
• ヘキサフェニルエタン型化合物を基軸とした酸化還元型応答系の構築

  Jun-ichi Nishida, Takanori Suzuki, Takashi Tsuji

  J. Syn. Org. Chem., Jpn. 60 1 40 - 51 The Society of Synthetic Organic Chemistry, Japan 2002年 [査読有り][通常論文]
   

  Redox reactions of a series of dicationic dyes (22+, 42+, 62+) having two triarylmethylenium chromophores were studied, which are interconvertible with colorless hexaarylethane derivatives (1, 3) or 9-membered cyclic peroxides (5), respectively, upon two-electron transfer. They constitute a new class of electrochromic systems endowed with high electrochemical bistability since the reversible bond making/breaking causes the drastic changes in the geometrical and electronic structures of the redox pairs. Bond dissociated cation radical 2+. is the stable intermediate for the interconversion between 1 and 22+, and the unprecedented tricolor chromic systems showing a hysteretic color change were constructed based on 1, 2+., and 22+. Drastic change in CD spectrum was observed during the interconversion between chiral helicenes 3 and binaphthylic dications 42+, which is the successful demonstration of electrochiroptical response. Peroxides 5 were readily obtained by two-electron reduction of dications 62+ under air. Since 62+ were regenerated by the "oxidative deoxygenation" reaction of 5, these pairs can serve as a electrochemically controlled oxygen-storage system.
• Supramolecular graphyne: a C(sp)-H center dot center dot center dot N hydrogen-bonded unique network structure of 2,4,6-triethynyl-1,3,5-triazine

  M Ohkita, M Kawano, T Suzuki, T Tsuji

  CHEMICAL COMMUNICATIONS 24 3054 - 3055 2002年 [査読有り][通常論文]
   

  The crystallization of 2,4,6-triethynyl-1,3,5-triazine (2) leads to a pi-stacked layered structure of a C(sp)-H...N hydrogen-bonded unique hexagonal network structure, which may be regarded as a supramolecular analogue of a hitherto unknown graphyne network: in-plane intermolecular interactions are short and linear H...N contacts (2.31 and 2.34 Angstrom) and the interlayer separation is 3.23 Angstrom.
• Preparation, structure, and amphoteric redox properties of p-phenylenediamine-type dyes fused with a chalcogenadiazole unit

  T Suzuki, T Tsuji, T Okubo, A Okada, Y Obana, T Fukushima, T Miyashi, Y Yamashita

  JOURNAL OF ORGANIC CHEMISTRY 66 26 8954 - 8960 2001年12月 [査読有り][通常論文]
   

  4,7-Bis(dialkylamino)benzo[c] [1,2,5]chalcogenadiazoles are a novel class of organic dyes that undergo reversible two-stage one-electron oxidation as well as one-electron reduction. They exhibit absorption maxima in the long-wavelength region, which are assigned as intramolecular charge transfer bands from the phenylenediamine moiety to the electron-accepting heterocycle. Their redox properties as well as molecular and crystal structures are affected by the alkyl substituents on the amino nitrogen and/or by the chalcogen atom (O, S, Se) in the heterocycle.
• Experimental and computational studies of naphtho[2,3-c]tropone: a highly polarized novel troponid system

  M Ohkita, K Sano, T Suzuki, T Tsuji

  TETRAHEDRON LETTERS 42 41 7295 - 7297 2001年10月 [査読有り][通常論文]
   

  Irradiation of 6.7-(2',3'-aphtho)bicyclo[3.2.0]hepta-3,6-dien-2-one (10) in a rigid glass at -196 degreesC leads to the formation of hitherto unknown naphtho[2,3-c]tropone (3). which exhibits a characteristic UV-vis absorption extending to 700 nm and undergoes rapid [pi 12+pi 14] dimerization upon thawing the glass. NICS(1) values calculated for a series of benzo- and naphtho-fused tropones suggest that aromatic character of the tropone ring in 3 is significantly increased relative to the parent system. (C) 2001 Elsevier Science Ltd. All rights reserved.
• Polar assembly of 2,6-diethynylpyridine through C(sp(2))-H center dot center dot center dot N, C(sp)-H center dot center dot center dot pi and pi-pi stacking interactions: Crystal structure and nonlinear optical properties

  M Ohkita, T Suzuki, K Nakatani, T Tsuji

  CHEMISTRY LETTERS 10 988 - 989 2001年10月 [査読有り][通常論文]
   

  The crystallization of 2,6-diethynylpyridine 1 leads to C(sp(2))-H . . .N hydrogen bonded head-to-tail tapes which are held together by C(sp)-H . . . pi hydrogen bridges to form 2D polar sheets; further assembly through pi-pi stacking interaction results in 3D polar crystals which show intense powder SHG response, 5-fold stronger than crystalline urea.
• A Redox Switch Based on Dihydro[5]helicene: Drastic Chiroptical Response Induced by Reversible C−C Bond Making/Breaking upon Electron Transfer

  Jun-ichi Nishida, Takanori Suzuki, Masakazu Ohkita, Takashi Tsuji

  Angewandte Chemie 113 17 3351 - 3354 Wiley-Blackwell 2001年09月03日 [査読有り][通常論文]
  
• Low-temperature X-ray structural analysis of propanedinitrile derivatives substituted with a bis(4-dimethylaminophenyl)methyl group: the origin of elongation of the donor–acceptor substituted C–C bond†

  Takanori Suzuki, Kazunori Ono, Hidetoshi Kawai, Takashi Tsuji

  J. Chem. Soc., Perkin Trans. 2 9 1798 - 1801 Royal Society of Chemistry ({RSC}) 2001年09月 [査読有り][通常論文]
   

  Push-pull type substitution at C-sp 3-C-sp 3 in the title. compounds does not have special electronic effects on the bond length, and the observed expansion can be best accounted for by steric interaction between substituents.
• Dual-mode electrochromism switched by proton transfer: dynamic redox properties of bis(diarylmethylenium)-type dyes

  T Suzuki, H Higuchi, M Ohkita, T Tsuji

  CHEMICAL COMMUNICATIONS 17 1574 - 1575 2001年09月 [査読有り][通常論文]
   

  Upon oxidative dimerization of pale yellow Ar2C-CHPh 1 (Ar = 4-Me2NC6H4), deep blue 1,4-dication 2(2+) was obtained as a stable salt, which was transformed into I by reductive C-C bond fission; deprotonation of 22+ gave intense yellow diene 3, which was interconvertible with violet dication 4(2+) by two-electron transfer, thus exhibiting two distinct modes of electrochromism before and after proton transfer.
• Crystal engineering using very short and linear C(sp)–H⋯N hydrogen bonds: formation of head-to-tail straight tapes and their assembly into nonlinear optical polar crystals

  Masakazu Ohkita, Takanori Suzuki, Takashi Tsuji, Keitaro Nakatani

  Chemical Communications 16 1454 - 1455 Royal Society of Chemistry ({RSC}) 2001年08月 [査読有り][通常論文]
   

  The crystallization of 4-ethynylpyridine (1) and 4-(4-ethynylphenyl)ethynylpyridine (2) leads to C(sp)-H···N hydrogen bonded straight tapes that further assemble into polar crystals, in the case of 2, and show intense powder SHG response, 8 times more efficient than crystalline urea.
• ChemInform Abstract: Preparation, X-Ray Structures and Unique Redox Reactions of Novel 2,2′-(2,2-Dimethylpropane-1,3-diylidene)bis(1,3-benzodithiole)-type Electron Donors Fused with a Naphthalene Ring.

  Takanori Suzuki, Tsuyoshi Yoshino, Masakazu Ohkita, Takashi Tsuji

  ChemInform 32 7 no - no Wiley-Blackwell 2001年02月 [査読有り][通常論文]
  
• Generation and amphoteric redox properties of novel neutral radicals with the TTF-TCNQ hybrid structure

  T Suzuki, M Yamada, M Ohkita, T Tsuji

  HETEROCYCLES 54 1 387 - 394 2001年01月 [査読無し][通常論文]
   

  One electron oxidation of 4-(2-tetrathiafulvalenyl)phenyl substituted dicyanomethylides (1-) gave black solids of the title radicals (1(.)). They exhibit quite high electrochemical amphotericity, which may be responsible for their good electrical conductivities (sigma = ca. 10(-7) S cm(-1)) as a single component. Isomeric radicals (2(.)) with a m-phenylene spacer could not be obtained under the similar conditions probably due to insufficient delocalization of the unpaired electron.
• Single-component organic semiconductors based on novel radicals that exhibit electrochemical amphotericity: Preparation, crystal structures, and solid-state properties of N,N′-dicyanopyrazinonaphthoquinodiiminides substituted with an N-alkylpyridinium uni

  T. Suzuki, S. Miyanari, Y. Tsubata, T. Fukushima, T. Miyashi, Y. Yamashita, K. Imaeda, T. Ishida, T. Nogami

  Journal of Organic Chemistry 66 1 216 - 224 American Chemical Society ({ACS}) 2001年01月 [査読有り][通常論文]
   

  N,N′-Dicyanonaphthoquinodiimines fused with a pyrazine ring 1 were prepared from the corresponding quinones 4. The new acceptors 1 have a planar π-system and undergo reversible two-stage 1e-reduction. Quaternization of the pyridyl substituent in 1d-f gave pyridinium derivatives 2d+, 2e+, and R-3+, respectively, which are stronger acceptors that undergo three-stage 1e-reduction. Upon electrochemical reduction of these cations, novel radicals 2d·, 2e·, and R-3· were generated and isolated as stable solids. The molecular geometries determined by X-ray analysis indicated that these radicals adopt a zwitterionic structure, in which the unpaired electron is located on the quinodiimine unit but not on the pyridyl group. These novel radicals undergo facile and reversible 1e-oxidation as well as two-stage 1e-reduction. The observed amphotericity endows the radicals with electrical conductivities (10-5 to 10-9 S cm-1), and these thus represent a new motif for singlecomponent organic semiconductors.
• A redox switch based on dihydro[5]helicene: Drastic chiroptical response induced by reversible C-C bond making/breaking upon electron transfer

  J Nishida, T Suzuki, M Ohkita, T Tsuji

  ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 40 17 3251 - + 2001年 [査読有り][通常論文]
  
• Generation and amphoteric redox properties of novel neutral radicals with the TTF-TCNQ hybrid structure

  T Suzuki, M Yamada, M Ohkita, T Tsuji

  HETEROCYCLES 54 1 387 - 394 2001年01月 [査読有り][通常論文]
   

  One electron oxidation of 4-(2-tetrathiafulvalenyl)phenyl substituted dicyanomethylides (1-) gave black solids of the title radicals (1(.)). They exhibit quite high electrochemical amphotericity, which may be responsible for their good electrical conductivities (sigma = ca. 10(-7) S cm(-1)) as a single component. Isomeric radicals (2(.)) with a m-phenylene spacer could not be obtained under the similar conditions probably due to insufficient delocalization of the unpaired electron.
• Kinetic stabilization of the [1.1]paracyclophane system: Isolation and X-ray structural analysis of a [1.1]paracyclophane derivative and its interconversion with the transannular adduct

  H Kawai, T Suzuki, M Ohkita, T Tsuji

  CHEMISTRY-A EUROPEAN JOURNAL 6 22 4177 - 4187 2000年11月 [査読有り][通常論文]
   

  Intentionally designed kinetic stabilization of the [1.1]paracyclophane skeleton has been achieved by multiple substitution of the aromatic rings with trimethylsilylmethyl and N,N-dimethylcarbamoyl groups, which serve to shield the proximate bridgehead carbon atoms sterically from access by other reagents. The bis(Dewar benzene) precursor (1a) has been prepared in essentially the same manner as previous derivatives-starting from the photocycloaddition of 1,4-bis(trimethylsilyl)-2-butyne to octahydroindacene-1,5-dione-except for a few critical modifications described in the text. Substituted [1.1]paracyclophane (2a), photochemically generated from the precursor, is indefinitely stable at 50 degreesC and suffers decomposition only by 8% after 2 h at 100 degreesC in degassed n-decane, demonstrating its greatly improved kinetic stability compared to previous [1.1]paracyclophanes. Since 2a undergoes efficient photochemical transformation into the transannular addition product 3a, irradiation of 1a tends to produce a mixture of products consisting mainly of 3a. Compound 3a, however, reverts thermally to 2a in a process of half life 40 min at 55 degreesC; the activation parameters for this process are DeltaH(+) = 21.1 +/- 0.8 kcal mol(-1) and DeltaS(+) = - 10.5 +/- 2.6 cal K-1 mol(-1). Thus, on heating 3a in benzene and cooling the resultant solution, 2a is obtained as orange-red crystals. X-ray crystallographic analysis of 2a reveals benzene rings bent to the highest degree ever reported for a paracyclophane, with their face-to-face arrangement in unusually close proximity. The shortest nonbonding interatomic distance is 2.376 Angstrom less than the sum of the van der Waals radii by more than 1.0 Angstrom. The generation of related substituted [1.1]paracyclophanes and their kinetic stabilities are also reported.
• Kinetic stabilization of the [1.1]paracyclophane system: Isolation and X-ray structural analysis of a [1.1]paracyclophane derivative and its interconversion with the transannular adduct

  H Kawai, T Suzuki, M Ohkita, T Tsuji

  CHEMISTRY-A EUROPEAN JOURNAL 6 22 4177 - 4187 2000年11月 [査読有り][通常論文]
   

  Intentionally designed kinetic stabilization of the [1.1]paracyclophane skeleton has been achieved by multiple substitution of the aromatic rings with trimethylsilylmethyl and N,N-dimethylcarbamoyl groups, which serve to shield the proximate bridgehead carbon atoms sterically from access by other reagents. The bis(Dewar benzene) precursor (1a) has been prepared in essentially the same manner as previous derivatives-starting from the photocycloaddition of 1,4-bis(trimethylsilyl)-2-butyne to octahydroindacene-1,5-dione-except for a few critical modifications described in the text. Substituted [1.1]paracyclophane (2a), photochemically generated from the precursor, is indefinitely stable at 50 degreesC and suffers decomposition only by 8% after 2 h at 100 degreesC in degassed n-decane, demonstrating its greatly improved kinetic stability compared to previous [1.1]paracyclophanes. Since 2a undergoes efficient photochemical transformation into the transannular addition product 3a, irradiation of 1a tends to produce a mixture of products consisting mainly of 3a. Compound 3a, however, reverts thermally to 2a in a process of half life 40 min at 55 degreesC; the activation parameters for this process are DeltaH(+) = 21.1 +/- 0.8 kcal mol(-1) and DeltaS(+) = - 10.5 +/- 2.6 cal K-1 mol(-1). Thus, on heating 3a in benzene and cooling the resultant solution, 2a is obtained as orange-red crystals. X-ray crystallographic analysis of 2a reveals benzene rings bent to the highest degree ever reported for a paracyclophane, with their face-to-face arrangement in unusually close proximity. The shortest nonbonding interatomic distance is 2.376 Angstrom less than the sum of the van der Waals radii by more than 1.0 Angstrom. The generation of related substituted [1.1]paracyclophanes and their kinetic stabilities are also reported.
• Kinetic stabilization of the [1.1]paracyclophane system: Isolation and X-ray structural analysis of a [1.1]paracyclophane derivative and its interconversion with the transannular adduct

  H Kawai, T Suzuki, M Ohkita, T Tsuji

  CHEMISTRY-A EUROPEAN JOURNAL 6 22 4177 - 4187 2000年11月 [査読有り][通常論文]
   

  Intentionally designed kinetic stabilization of the [1.1]paracyclophane skeleton has been achieved by multiple substitution of the aromatic rings with trimethylsilylmethyl and N,N-dimethylcarbamoyl groups, which serve to shield the proximate bridgehead carbon atoms sterically from access by other reagents. The bis(Dewar benzene) precursor (1a) has been prepared in essentially the same manner as previous derivatives-starting from the photocycloaddition of 1,4-bis(trimethylsilyl)-2-butyne to octahydroindacene-1,5-dione-except for a few critical modifications described in the text. Substituted [1.1]paracyclophane (2a), photochemically generated from the precursor, is indefinitely stable at 50 degreesC and suffers decomposition only by 8% after 2 h at 100 degreesC in degassed n-decane, demonstrating its greatly improved kinetic stability compared to previous [1.1]paracyclophanes. Since 2a undergoes efficient photochemical transformation into the transannular addition product 3a, irradiation of 1a tends to produce a mixture of products consisting mainly of 3a. Compound 3a, however, reverts thermally to 2a in a process of half life 40 min at 55 degreesC; the activation parameters for this process are DeltaH(+) = 21.1 +/- 0.8 kcal mol(-1) and DeltaS(+) = - 10.5 +/- 2.6 cal K-1 mol(-1). Thus, on heating 3a in benzene and cooling the resultant solution, 2a is obtained as orange-red crystals. X-ray crystallographic analysis of 2a reveals benzene rings bent to the highest degree ever reported for a paracyclophane, with their face-to-face arrangement in unusually close proximity. The shortest nonbonding interatomic distance is 2.376 Angstrom less than the sum of the van der Waals radii by more than 1.0 Angstrom. The generation of related substituted [1.1]paracyclophanes and their kinetic stabilities are also reported.
• ChemInform Abstract: A 2,3,5,6-Tetramethylenebicyclo[2.2.0]hexane Derivative: A Novel Bisdiene Molecule That Produces a Dewar Benzene Skeleton Upon Two Successive Diels-Alder Reactions with Dienophiles.

  Masakazu Ohkita, Kieko Sano, Sotoyuki Dohba, Yuko Fujita, Takanori Suzuki, Takashi Tsuji

  ChemInform 31 41 no - no 2000年10月10日 [査読有り][通常論文]
  
• Preparation, structure, and unique redox properties of mono-, bis-, and tris(diarylmethylene)-1,3,5-trithianes and related compounds

  T Suzuki, T Yoshino, J Nishida, M Ohkita, T Tsuji

  JOURNAL OF ORGANIC CHEMISTRY 65 18 5514 - 5521 2000年09月 [査読有り][通常論文]
   

  A series of 1,3,5-trithianes 1-3 having diarylmethylene units were designed as novel electron donors giving highly colored cationic species upon oxidation. They were prepared along with the dithiane and dithiazine derivatives 4-6 by the reactions of lithiated heterocycles with diaryl ketones followed by dehydration. Voltammetric analyses indicate that a large structural change and/or transannular bonding are induced during their electrochemical oxidation. Mono(diarylmethylene) derivative 1a exhibits electrochromism with vivid change in color from faintly yellow to deep blue with concomitant rotation around the exocyclic bond. Both of the strongly colored salts obtained upon oxidation of 2,4-bis- and 2,4,6-tris(diarylmethylene)-1,3,5-trithianes (2aa and 3) consist of the dications with a 1,2,4-trithiane ring, suggesting the easy skeletal rearrangement of the transannular dications with a trithiabicylo[3. 1.0]hexane ring. Upon reduction of these salts were obtained bright yellow 12 and 13, respectively, with high electron-donating properties due to the tetraarylbutadiene-type conjugation, thus giving another class of electrochromic compounds.
• Preparation and molecular structures of 9,10-dihydrophenanthrenes: Substituent effects on the long bond length

  T Suzuki, K Ono, J Nishida, H Takahashi, T Tsuji

  JOURNAL OF ORGANIC CHEMISTRY 65 16 4944 - 4948 2000年08月 [査読有り][通常論文]
   

  9,10-Dihydrophenanthrene derivatives 1-3 with electron-donating and/or -accepting groups at their 9,10-positions were prepared, and their precise molecular structures were determined by X-ray analyses at 203 K. The long C-9-C-10 bond [1.646(4) Angstrom] in the hexaarylethane-type compound 1 with four electron-donating groups is mainly caused by steric interaction. Push-pull type substitution does not induce the elongation of the central bond in the present system; the corresponding distance in 9,9-bis(4-dimethylaminophenyl)-10,10-dicyano derivative 2 [1.599(4) Angstrom] is intermediate between those of 1 and the tetracyano compound 3 [1.587(2) Angstrom].
• Syntheses of acetylenic oligophenylene macrocycles based on a novel Dewar benzene building block approach

  M Ohkita, K Ando, T Suzuki, T Tsuji

  JOURNAL OF ORGANIC CHEMISTRY 65 14 4385 - 4390 2000年07月 [査読有り][通常論文]
   

  A general synthetic approach to strained p-phenylene-based acetylenic macrocycles is described. A key feature in this approach is exploitation of Dewar benzene as an angular p-phenylene synthon. Thus, 1,4-acetal-bridged 2,5-dichloro(Dewar benzene) 5, prepared in four steps from dimethyl acetylenedicarboxylate and 1,2-dichloroethylene, is applied as such a building block in the syntheses of strained macrocycles 13 and anti-20. For the synthesis of 13, m-phenylene units are used as spacers and modified Eglington-Glaser coupling is applied for the macrocyclization step. For the synthesis of anti-20, on the other hand, o-phenylene units are used as spacers and Sonogashira coupling is applied for the macrocyclization step. Macrocycles 13 and anti-20 are characterized crystallographically? and their strained nature is reflected mainly in the deviation of the acetylene units from linearity; the C=C-C angles range from 168.7(3)degrees to 179.9(3)degrees in 13 and from 168.0(5)degrees to 171.4(4)degrees in anti-20, Macrocycle 13 shows unique conformational property, namely, the p-phenylene units arranged in parallel in the rectangular framework rotate freely about the long axes, as evidenced by the H-1 NMR studies. Macrocycle anti-20 exhibits a Stokes shift of 179 nm, which is exceptionally large for phenylacetylene macrocycles, presumably owing to the characteristic stacking structure.
• ChemInform Abstract: Synthesis and Reaction of 1,4-Acetal-Bridged 2,3,5,6-Tetramethylidenebicyclo[2.2.0]hexane: The First Diels-Alder Route to Dewar Benzenes.

  Masakazu Ohkita, Takanori Suzuki, Takashi Tsuji

  ChemInform 31 2 no - no 2000年01月11日 [査読有り][通常論文]
  
• ChemInform Abstract: Supramolecular Aggregation of m-Nitrobenzoic Acid by C-H×××O and O-H×××O Hydrogen Bondings in the Crystalline Charge-Transfer Complexes with Aromatic Hydrocarbons.

  Takanori Suzuki, Takashi Tsuji, Takanori Fukushima, Setsuko Miyanari, Tsutomu Miyashi, Yasuyuki Sakata, Tsutomu Kouda, Hiroki Kamiyama

  ChemInform 31 2 no - no Wiley-Blackwell 2000年01月11日 [査読有り][通常論文]
  
• Preparation, structure, and redox reactions of nine-membered cyclic peroxides: A novel electrochromic system undergoing reversible extrusion and trapping of O-2

  T Suzuki, J Nishida, M Ohkita, T Tsuji

  ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 39 10 1804 - + 2000年 [査読有り][通常論文]
  
• Preparation, X-ray structures and unique redox reactions of novel 2,2′-(2,2-dimethylpropane-1,3-diylidene)bis(1,3-benzodithiole)-type electron donors fused with a naphthalene ring

  Takanori Suzuki, Tsuyoshi Yoshino, Masakazu Ohkita, Takashi Tsuji

  Journal of the Chemical Society, Perkin Transactions 1 20 3417 - 3420 Royal Society of Chemistry ({RSC}) 2000年 [査読有り][通常論文]
   

  The title pi-extended TTF derivatives 1 and 2 were prepared from the corresponding diketones by Wittig-Horner reactions. Donor 1 with a naphthalene-1,8-diyl skeleton adopts a butterfly-shaped geometry; its oxidation caused transannular C-C bonding to give the dicationic cyclopropane derivative 4(2+), from which 1 was regenerated upon 2e-reduction. The 2,3-diyl isomer 2 possesses, on the other hand, an almost planar pi-system and underwent 2-stage 1e-oxidation, thus allowing the isolation of both 2(.+) and 2(2+) as stable salts.
• First Dewar benzene approach to acetylenic oligophenylene macrocycles: synthesis and structure of a molecular rectangle bearing two spindles

  M Ohkita, K Ando, K Yamamoto, T Suzuki, T Tsuji

  CHEMICAL COMMUNICATIONS 1 83 - 84 2000年 [査読有り][通常論文]
   

  A novel Dewar benzene approach to the construction of oligophenylene macrocycles has been developed by introducing Dewar benzene 1 as a building block and applied to the synthesis of a molecular rectangle 8, whose structure was characterized crystallographically.
• ChemInform Abstract: Preparation, Structure, and Unique Redox Properties of Mono-, Bis-, and Tris(diarylmethylene)-1,3,5-trithianes and Related Compounds.

  Takanori Suzuki, Tsuyoshi Yoshino, Jun-ichi Nishida, Masakazu Ohkita, Takashi Tsuji

  ChemInform 31 51 no - no 2000年 [査読有り][通常論文]
  
• A 2,3,5,6-tetramethylenebicyclo[2.2.0]hexane derivative: a novel bisdiene molecule that produces a Dewar benzene skeleton upon two successive Diels–Alder reactions with dienophiles

  Masakazu Ohkita, Kieko Sano, Sotoyuki Dohba, Yuko Fujita, Takanori Suzuki, Takashi Tsuji

  Journal of the Chemical Society, Perkin Transactions 1 12 1971 - 1975 Royal Society of Chemistry ({RSC}) 2000年 [査読有り][通常論文]
   

  A new bisdiene molecule 1, the 1,4-acetal-bridged derivative of the hitherto unknown 2,3,5,6-tetramethylenebicyclo[2.2.0]hexane, is synthesized in four steps from dimethyl acetylenedicarboxylate and (E)-1,4-dichlorobut-2-ene. Reaction of 1 with dimethyl acetylenedicarboxylate or benzyne leads to the formation of the Dewar benzene derivatives 6 and 7, respectively, through two successive Diels-Alder additions of the dienophiles to 1. Dehydrogenation of the adducts 6 and 7 affords the corresponding 9,10-Dewar anthracene derivative 10 and 6,13-Dewar pentacene derivative 11, respectively. Compound 11 is characterized crystallographically. Reactions of 1,4-benzoquinone and N-phenylmaleimide with 1 are also reported.
• Preparation, structure, and redox reactions of nine-membered cyclic peroxides: A novel electrochromic system undergoing reversible extrusion and trapping of O-2

  T Suzuki, J Nishida, M Ohkita, T Tsuji

  ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 39 10 1804 - + 2000年 [査読有り][通常論文]
   

  The hitherto unknown 1,2,6-tricyclononane derivatives 1 (X = O, S) were readily obtained upon the electrochemical 2 electron reduction of 22+ in air (see scheme). Oxidative deoxygenation of the colorless peroxides 1 regenerates the orange 22+ ions.
• Synthesis and reaction of 1,4-acetal-bridged 2,3,5,6-tetramethylidene-bicyclo[2.2.0]hexane: the first Diels–Alder route to Dewar benzenes

  Masakazu Ohkita, Takanori Suzuki, Takashi Tsuji

  Chemical Communications 19 1999 - 2000 Royal Society of Chemistry ({RSC}) 1999年10月 [査読有り][通常論文]
   

  The 1,4-acetal-bridged derivative of hitherto unknown 2,3,5,6-tetramethylidenebicyclo[2.2.0]hexane, which produces the Dewar benzene skeleton through two successive Diels-Alder reactions with dienophiles, has been synthesized in four steps from dimethyl acetylenedicarboxylate and 1,4-dichlorobut-2-ene.
• Supramolecular Aggregation of m -Nitrobenzoic Acid by C−H···O and O−H···O Hydrogen Bondings in the Crystalline Charge-Transfer Complexes with Aromatic Hydrocarbons

  Takanori Suzuki, Takashi Tsuji, Takanori Fukushima, Setsuko Miyanari, Tsutomu Miyashi, Yasuyuki Sakata, Tsutomu Kouda, Hiroki Kamiyama

  The Journal of Organic Chemistry 64 19 7107 - 7113 American Chemical Society ({ACS}) 1999年09月 [査読有り][通常論文]
   

  Charge-transfer complexation of m-nitrobenzoic acid (1) with aromatic hydrocarbons was found to exhibit size and shape selectivity: naphthalene or its 2,7-dimethyl and 2,3,6,7-tetramethyl derivatives failed to afford crystalline complexes with 1 whereas yellow crystals containing a stoichiometric amount of 2,3- or 2,6-dimethylnaphthalene, biphenylene, or anthracene were obtained by the direct method in CH2Cl2. X-ray analyses on these complexes have revealed dimer formation of 1 by O-H ... O hydrogen bonding, yet the important structural motif observed as a common feature is the two-dimensional sheetlike network, in which the dimers of 1 are further connected by C-H ... O hydrogen bonding to form a series of inclusion lattices that incorporate hydrocarbon guests. Such a supramolecular aggregation by C-H ... O bonding was proven to take a significant part in the recognition properties of 1 to differentiate the dimethylnaphthalene isomers in its complexation process.
• Photoinduced electron-transfer cope rearrangements of 3,6-diaryl-2,6- octadienes and 2,5-diaryl-3,4-dimethyl-1,5-hexadienes: Stereospecificity and an unexpected formation of the bicyclo[2.2.0]hexane Derivatives

  Ikeda, H., Takasaki, T., Takahashi, Y., Konno, A., Matsumoto, M., Hoshi, Y., Aoki, T., Suzuki, T., Goodman, J.L., Miyashi, T.

  Journal of Organic Chemistry 64 5 1640 - 1649 1999年03月05日 [査読無し][通常論文]
   

  Under the 9,10-dicyanoanthracene-sensitized photoinduced electron- transfer conditions, (Z,Z)-, (E,E)-, (E,Z)-3,6-diaryl-2,6-octadiene and (d,l),(meso)-2,5-diaryl-3,4-dimethyl-1,5-hexadiene stereospecifically undergo the Cope rearrangement to give a Cope photostationary mixture. Remarkably, the photoinduced electron-transfer Cope rearrangements of the 4-methylphenyl derivatives are concurrent with the formation of trans- or endo,cis-1,4- bis(4-methylphenyl)-2,3-dimethylbicyclo[2.2.0]hexane in a Cope photostationary mixture. Observed stereospecificity of the Cope rearrangement and the formation of the bicyclo[2.2.0]hexane derivatives demonstrate the intermediacies of both the chair and boat 1,4-diaryl-1,2-dimethylcyclohexane- 1,4-diyl and cation radical intermediates in a Cope rearrangement cycle. Photoreactions of trans- and exo,cis-1,4-diaryl-5,6-dimethyl-2,3- diazabicyclo[2.2.2]oct-2-enes further support the interventions of the diyl intermediates in the Cope rearrangement cycle. By photoacoustic analysis, a cation radical cyclization-diradical cleavage mechanism is proposed for the photoinduced electron-transfer Cope rearrangement of the title dienes.
• First stable tetracyanodiphenoquinodimethane with a completely planar geometry: Preparation, X-ray structure, and highly conductive complexes of bis[1,2,5]thiadiazolo-TCNDQ

  Takanori Fukushima, Nobuharu Okazeri, Tsutomu Miyashi, Kazuharu Suzuki, Yoshiro Yamashita, Takanori Suzuki

  Tetrahedron Letters 40 6 1175 - 1178 1999年02月
• Electrical and Nonlinear Optical Properties of Langmuir-Blodgett Films of Charge Transfer Complexes

  Nakamura, T., Yumoto, T., Suzuki, T., Akutagawa, T., Hasegawa, T., Tachibana, H., Matsumoto, M., Horiuchi, S., Ikegami, H., Yamochi, H., Saito, G.

  Molecular Crystals and Liquid Crystals Science and Technology Section A: Molecular Crystals and Liquid Crystals 327 1999年
• First stable tetracyanodiphenoquinodimethane with a completely planar geometry: Preparation, X-ray structure, and highly conductive complexes of bis[1,2,5]thiadiazolo-TCNDQ

  Fukushima, T., Okazeri, N., Miyashi, T., Suzuki, K., Yamashita, Y., Suzuki, T.

  Tetrahedron Letters 40 6 1999年
• A new type of tricolor electrochromic system based on the dynamic redox properties of hexaarylethane derivatives

  T Suzuki, J Nishida, T Tsuji

  CHEMICAL COMMUNICATIONS 20 2193 - 2194 1998年10月 [査読有り][通常論文]
   

  Electrochemical interconversion between 9,9,10,10-tetraaryldihydrophenanthrene 1 and 2,2'-bis(triarylmethylium) 2(2+) has been proven to proceed via open form cation radical 2(+.) as a stable intermediate; using these three species, a novel tricolor electrochromic system that exhibits hysteretic color change (color 1 --> color 2 --> color 3 --> color 1) is formed.
• Biphenyl-type electron acceptors exhibiting dynamic redox properties: a novel electrochromic system with ‘write protect’ option

  Takanori Suzuki, Jun-ichi Nishida, Takashi Tsuji

  Chemical Communications 13 1331 - 1332 Royal Society of Chemistry ({RSC}) 1998年07月 [査読有り][通常論文]
   

  A novel redox pair undergoing reversible C-C bond making/ breaking has been constructed based on a bis(dicyanovinyl)biphenyl derivative and a dianion with the dihydrophenanthrene skeleton; further cyclization of the latter to an enaminonitrile endows the 'write protect' option to its electrochromic response.
• A kinetically stabilized [1.1]paracyclophane: Isolation and X-ray structural analysis

  H Kawai, T Suzuki, M Ohkita, T Tsuji

  ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 37 6 817 - 819 1998年04月 [査読有り][通常論文]
  
• A kinetically stabilized [1.1]paracyclophane: Isolation and X-ray structural analysis

  H Kawai, T Suzuki, M Ohkita, T Tsuji

  ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 37 6 817 - 819 1998年04月 [査読有り][通常論文]
  
• Ein kinetisch stabilisiertes [1.1]Paracyclophan – Isolierung und Röntgenstrukturanalyse

  Hidetoshi Kawai, Takanori Suzuki, Masakazu Ohkita, Takashi Tsuji

  Angewandte Chemie 110 6 827 - 829 Wiley-Blackwell 1998年03月 [査読有り][通常論文]
  
• Isolation and X-ray Structural Determination of Both Folded and Twisted Conformers of Bis{4H,8H-4-(dicyanomethylene)-benzo[1,2-c:4,5-c′]bis[1,2,5]thiadiazol-8-ylidene}, an Overcrowded Ethylene with High Electron Affinity

  Takanori Suzuki, Takanori Fukushima, Tsutomu Miyashi, Takashi Tsuji

  Angewandte Chemie International Edition in English 36 22 2495 - 2497 Wiley-Blackwell 1997年12月 [査読有り][通常論文]
  
• Dibenzotetrathiafulvalenes inserted with cycloalkanes and their tricyclic valence isomers: reversible C–C bond making/breaking upon electron transfer

  Takanori Suzuki, Masahide Kondo, Tatsuo Nakamura, Takanori Fukushima, Tsutomu Miyashi

  Chemical Communications 23 2325 - 2326 Royal Society of Chemistry ({RSC}) 1997年12月 [査読有り][通常論文]
   

  The title TTF derivatives and their tricyclic valence isomers afford the same bicyclic dications upon two-electron oxidation, and the resulting dications regenerate either one or the other of the two isomers selectively upon reduction.
• Tricyclo[4.2.2.2(2,5)]dodeca-1,3,5,7,9,11-hexaene: generation and chemical trapping of the 3,4-dicyano derivative

  T Tsuji, M Okuyama, M Ohkita, T Imai, T Suzuki

  CHEMICAL COMMUNICATIONS 22 2151 - 2152 1997年11月 [査読有り][通常論文]
   

  The 3,4-dicyano derivative of hitherto unknown tricycle[4.2.2.2(2,5)]dodeca-1,3,5,7,9,11-hexaene, in which six double bonds are uniquely arranged, is generated and chemically trapped with 1,2-dimethylenecyclopentane and tert-butyl-lithium.
• Hexaphenylethane derivatives exhibiting novel electrochromic behavior

  T Suzuki, J Nishida, T Tsuji

  ANGEWANDTE CHEMIE-INTERNATIONAL EDITION IN ENGLISH 36 12 1329 - 1331 1997年07月 [査読有り][通常論文]
  
• Hexaphenylethan-Derivate mit neuartigem elektrochromem Verhalten

  Takanori Suzuki, Jun-Ich Nishida, Takashi Tsuji

  Angew. Chem. 109 12 1387 - 1389 1997年06月 [査読有り][通常論文]
  
• Tetracyanoquinodimethanes Fused With A [1,2,5]Chalcogenadiazole Ring

  Takanori Suzuki, Yoshiro Yamashita, Takanori Fukushima, Tustomu Miyashi

  Molecular Crystals and Liquid Crystals 296 1997年 [査読有り][通常論文]
  
• Electronic structures and oxidation potentials of some azulene derivatives

  T Kurihara, T Suzuki, H Wakabayashi, S Ishikawa, K Shindo, Y Shimada, H Chiba, T Miyashi, M Yasunami, T Nozoe

  BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 69 7 2003 - 2008 1996年07月 [査読有り][通常論文]
   

  The electronic structures of azulene (1) and its alkylated derivatives were investigated on the basis of MO calculations by MNDO and PM3 method. There results were experimentally evaluated by measuring the oxidation potentials (E(ox)) of 1 and its alkylated derivatives, from which the additive property on E(ox) was suggested as shown by E(ox)(Az.subst)=E(ox)(AZ)-0.10n(1,3)+0.06n(2)-0.02n(4,8)-0.11n(5,7)-0.01n(6). Thus, the alkyl groups at the 1,3- and 5,7-positions lower the E(ox) values by ca. 0.1 V, and stronger donating properties were observed for 3-methylguaiazulene (E(ox)=+0.53 V) and 3,3'biguaiazulene (E(ox)=+0.40 V). The redox properties of guaiazulenyl sulfides which were prepared from guaiazulene via a phenylsulfonylthio derivative were also studied. Unlike the alkylated azulenes they underwent reversible one-electron oxidations and exhibited stronger donating properties (E(ox)=+0.40-+0.44).
• Photoinduced skeletal rearrangement of 1,1-diarylspiropentanes

  Y Takahashi, H Ohaku, S Morishima, T Suzuki, H Ikeda, T Miyashi

  JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 1 4 319 - 325 1996年02月 [査読有り][通常論文]
   

  The photochemical reactivities of 1,1-diarylspiropentanes la-c have been investigated under various photolysis conditions. Upon direct photolysis or acetone-sensitized photolysis, 1 underwent skeletal rearrangement to afford methylidenecyclobutanes 2, 3 and 4. A mechanism involving diradical intermediates has been proposed. Also studied were the photochemical and thermal reactions of the electron donor-acceptor (EDA) complexes of 1 with tetracyanoethylene (TCNE). Photoirradiation of the charge-transfer (CT) absorption bands of the EDA complexes resulted in the skeletal rearrangement of 1 to 2 and 3, with concomitant formation of TCNE adducts 11b,c and 12a-c. The X-ray structure of Ile is reported. A mechanism involving ion radical pairs [1'(+), TCNE'(-)] is proposed for the photoreaction. In contrast, no skeletal rearrangement was observed in the thermal reaction of the EDA complexes although 11b and 11c were produced.
• Photoreactions of crystalline charge-transfer complexes

  Suzuki, T.

  Pure and Applied Chemistry 68 2 1996年
• ESR of the anion radical of 2,6-dithioxobenzo[1,2-d:4,5-d']bis[1,3] dithiol-4,8-dione. Observation of the satellites of O-17, C-13, and S-33 and the second-generation satellites due to both C-13 and S-33 in natural abundance

  M Hirayama, T Terasaka, Y Yamashita, T Susuki, T Miyashi, Y Usui

  BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 68 12 3337 - 3339 1995年12月 [査読有り][通常論文]
   

  ESR study of the anion radical produced by the reduction of the title compound (DTB-BDTD) with potassium metal in 1,2-dimethoxyethane is reported. In addition to the satellites of O-17, C-13, and S-33, the second-generation satellite lines of extremely low intensity, arising from both C-13 and S-33 isotopes in natural abundance, have been detected. It was found that these satellites vary markedly in line width among each component of its multiplet. This line width effect was used to determine the sign of hfs constants of these magnetic nuclei, and the resulting signs agreed well with those estimated from the spin densities obtained by the McLachlan procedure and the INDO method.
• ESR OF THE TRIANION AND ANION-RADICALS OF BENZO[G][1,2,5]THIADIAZOLO[3,4-B]QUINOXALINE-5,10-DIONE AND ITS SELENIUM ANALOG

  M HIRAYAMA, T TERASAKA, M ITASAKA, T SUZUKI, Y YAMASHITA, T MIYASHI

  CHEMISTRY LETTERS 9 837 - 838 1995年09月 [査読有り][通常論文]
   

  The anion and trianion radicals of title compounds were generated by electrolysis in acetonitrile at room temperature and their ESR spectra were measured, which carl be identified on the basis of pi-MO calculations of hfsc's.
• PHOTOINDUCED SKELETAL REARRANGEMENT OF 1,1-DIPHENYLSPIROPENTANES

  Y TAKAHASHI, H OHAKU, S MORISHIMA, T SUZUKI, T MIYASHI

  TETRAHEDRON LETTERS 36 29 5207 - 5210 1995年07月 [査読有り][通常論文]
   

  Photoreactions of 1,1-diphenylspiropentanes have been investigated under various photochemical conditions. The exploratory studies have provided unprecedented examples of photochemically induced skeletal rearrangement of spiropentanes to methylenecyclobutanes.
• THE PI-TRIANION RADICAL OF 2,3,6,7-TETRACYANOBENZO[1,2-B/4,5-B']BISDITHIOLE-4,8-DIONE - OBSERVATION OF ESR WITH C-13-SATELLITES IN NATURAL-ABUNDANCE

  M HIRAYAMA, M ITASAKA, T SUZUKI, Y YAMASHITA, T MIYASHI

  CHEMISTRY LETTERS 7 511 - 512 1995年07月 [査読有り][通常論文]
   

  The pi-trianion radical of the title compound was formed by electrolysis in acetonitrile and its ESR spectrum with C-13 satellites in natural abundance was observed, which was clearly identified by MO calculation.
• PHOTOINDUCED SKELETAL REARRANGEMENT OF 1,1-DIPHENYLSPIROPENTANES

  Y TAKAHASHI, H OHAKU, S MORISHIMA, T SUZUKI, T MIYASHI

  TETRAHEDRON LETTERS 36 29 5207 - 5210 1995年07月 [査読有り][通常論文]
   

  Photoreactions of 1,1-diphenylspiropentanes have been investigated under various photochemical conditions. The exploratory studies have provided unprecedented examples of photochemically induced skeletal rearrangement of spiropentanes to methylenecyclobutanes.
• 結晶状態に働く弱い分子間相互作用 分子認識から単結晶相反応まで

  Takanori SUZUKI

  J. Syn. Org. Chem., Jpn. 53 5 403 - 412 The Society of Synthetic Organic Chemistry, Japan 1995年 [査読有り][通常論文]
   

  The role of weak intermolecular interactions in 'crystal engineering' is briefly reviewed. The selective complexation of TNF (1) and mNBA (2) with 2,6-DMN was studied in detail to test the validity of C-H · · O hydrogen bonding in determining the molecular arrangement in multi-component organic solids. In order to find the new interacting sites in crystal 1,2,5-chalcogenadiazoles substituted with a dicyanomethylene group were designed. Systematic structural analyses of 4-12 indicated the presence of novel chalcogen-cyano interaction. This interaction is one of the sources of the directionality in crystal packing and caused the formation of 'ribbon'-like networks in the anion-radical salts as well as the CT crystals of 7. By the network were formed the inclusion cavities in the latter, which can be used for the isomer recognition or as unique reaction centers for topochemical transformation. The single crystal-to-single crystal reaction occurred in a certain case, and the S · · N ≡ C interaction was suggested to take part in maintaining the crystal matrix during the solid-state reaction.
• 2-(THIOPYRAN-4'-YLIDEN)-1,3-DITHIOLES FUSED WITH THIOPHENE UNITS - INTRAMOLECULAR S-S INTERACTION AFFECTING THE REDOX PROPERTIES AND MOLECULAR GEOMETRIES

  T SUZUKI, T SAKIMURA, S TANAKA, Y YAMASHITA, H SHIOHARA, T MIYASHI

  JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS 12 1431 - 1432 1994年06月 [査読有り][通常論文]
   

  The title molecules (1) are strong electron donors like tetrathiafulvalene (TTF) but possess non-planar geometries with short intramolecular contacts between S atoms (av. 3.06 Angstrom in 1b, X-ray); by contrast, their cation radicals are endowed with molecular planarity, and the shorter S...S contacts (av. 2.87 Angstrom in 1b(.+), X-ray) result in the enhanced attractive interaction as well as much smaller Coulombic repulsion in 1(2+) than in TTF2+.
• AN ABSOLUTE ASYMMETRIC-SYNTHESIS OF THE [2+2] CYCLOADDUCT VIA SINGLE CRYSTAL-TO-SINGLE CRYSTAL TRANSFORMATION BY CHARGE-TRANSFER EXCITATION OF SOLID-STATE MOLECULAR-COMPLEXES COMPOSED OF ARYLOLEFINS AND BIS[1,2,5]THIADIAZOLOTETRACYANOQUINODIMETHANE

  T SUZUKI, T FUKUSHIMA, Y YAMASHITA, T MIYASHI

  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 116 7 2793 - 2803 1994年04月 [査読有り][通常論文]
   

  The title electron acceptor, bis[1,2,5]thiadiazolotetracyanoquinodimethane(BTDA,1), formed weak electron-donor-acceptor (EDA) complexes with arylolefins such as styrene (ST) and divinylbenzenes (DVs). Upon charge-transfer (CT) excitation of these complexes in MeCN, the [2 + 2]-type cycloadducts(2) were formed via a single electron transfer. Similar cycloaddition reactions were efficiently induced when the solid-state molecular complexes of 1 and arylolefins were irradiated. In contrast to the close similarities in solution photochemistry, the solid state reactivities of three isomeric divinylbenzenes (oDV, mDV, pDV) were quite dissimilar because of the different molecular overlaps of 1 and DVs in the crystal. The apparent reactivity of the oDV.1 crystal was much higher than that in solution as in the case of the ST.1 crystal, and adduct 2o was formed via the single crystal-to-single crystal transformation. Because of the asymmetric crystal structure in oDV 1, the optically pure product with 95% ee was obtained from the achiral components without any external chiral source. On the other hand, the incomplete conversion of the mDV.1 crystal to 2m is due to the crystal-to-amorphous transformation, and the 1:2 adduct 6 was formed on irradiation of the pDV.1 crystal which could not be obtained on excitation of the EDA complex in MeCN.
• CYCLOREVERSION OF ARENE ENDOPEROXIDES INDUCED BY ELECTRON-TRANSFER

  Y TAKAHASHI, S MORISHIMA, K WAKAMATSU, T SUZUKI, T MIYASHI

  JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS 1 13 - 14 1994年01月 [査読有り][通常論文]
   

  Cycloreversion of arene endoperoxides 1-4 can be induced by photoexcitation of their electron donor-acceptor complexes with tetracyanoethylene.
• MOLECULAR RECOGNITION THROUGH C-H...O HYDROGEN-BONDING IN CHARGE-TRANSFER CRYSTALS - HIGHLY SELECTIVE COMPLEXATION OF 2,4,7-TRINITROFLUORENONE WITH 2,6-DIMETHYLNAPHTHALENE

  T SUZUKI, H FUJII, T MIYASHI, Y YAMASHITA

  JOURNAL OF ORGANIC CHEMISTRY 57 25 6744 - 6748 1992年12月 [査読有り][通常論文]
   

  Treatment of a dimethylnaphthalene (DMN) isomer mixture with 2,4,7-trinitrofluorenone (TNF) resulted in the predominant formation of 2,6-DMN-TNF (1:1) complex (3) accompanied by a small amount of 2,7-DMN-TNF (1:1) (4). X-ray structural analyses of these charge-transfer crystals showed that coplanar "ribbon"-like networks are formed by C-H...0 hydrogen bonding of TNF and that 3 is thermodynamically more stable than 4 due to the larger interactions through C-H...0 contacts.
• SINGLE-COMPONENT ORGANIC CONDUCTORS BASED ON NEUTRAL RADICALS CONTAINING THE PYRAZINO-TCNQ SKELETON

  Y TSUBATA, T SUZUKI, T MIYASHI, Y YAMASHITA

  JOURNAL OF ORGANIC CHEMISTRY 57 25 6749 - 6755 1992年12月 [査読有り][通常論文]
   

  Pyrazino-TCNQ (1a) prepared from 5,8-diiodoquinoxaline (4a) is, like TCNQ itself, a strong electron acceptor and gives a stable anion radical salt as well as highly conductive charge-transfer crystals with donors. Substituted derivatives 1b-i were similarly prepared from 3,6-diiodo-1,2-phenylenediamine (5) as a common intermediate, and bulky substituents such as the phenyl or pyridyl groups have very little effect on either the redox properties or planar geometry of la. Neutral radicals 3d-g derived from pyridyl-substituted derivatives 1d-g, respectively, are open-shell donor-pi-acceptor systems with high electrical amphotericity designed as a new motif for single-component organic conductors. The powder conductivity of 3f was as high as 3.2 X 10(-5) S cm-1.
• CRYSTAL-STRUCTURES OF METALLIC AND INSULATING MOLECULAR-COMPLEXES BETWEEN NAPHTHACENO[5,6-CD-11,12-C'D']BIS[1,2]DISELENOLE AND 4,8-BIS(DICYANOMETHYLENE)-4H,8H-BENZO[1,2-C-4,5-C']BIS[1,2,5]THIADIAZOLE - (TSEN)(BTDA-TCNQ) AND (TSEN)(BTDA-TCNQ)(C6H5CL)

  K IWASAKI, A UGAWA, A KAWAMOTO, Y YAMASHITA, K YAKUSHI, T SUZUKI, T MIYASHI

  BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 65 12 3350 - 3357 1992年12月 [査読有り][通常論文]
   

  The charge-transfer complex between naphthaceno[5,6-cd-11,12-c'd']bis[1,2]diselenole (TSeN) and 4,8-bis(dicyanomethylene)-4H,8H-benzo[1,2-c:4,5-c']bis[1,2,5]thiadiazole (BTDA-TCNQ) is found to show at least three different types of crystal modifications; insulating Type-I has a (1 : 1 : 1) ratio containing solvent molecules (chlorobenzene), metallic Type-II has a (1 : 1) stoichiometry, and semiconductive Type-III is conjectured to have a (1 : 2) or (2 : 1) stoichiometry. The crystal structures of Type-I and Type-II were determined by a single-crystal X-ray diffraction method. Type-I comprises mixed-stack molecular columns, and Type-II segregated-stack molecular columns. In both types the neighboring columns are linked along short molecular axes by two Se ... N contacts that are shorter than the corresponding van der Waals contact. In the Type-II crystal, there are other short distances between TSeN and BTDA-TCNQ in the direction of the long molecular axes. From the C=C bond length in the C=C(CN)2 group of BTDA-TCNQ, the degrees of charge transfer of these molecular complexes were estimated as 0.2+/-0.3 in Type-I and 0.9+/-0.2 in Type-II.
• EVIDENCE FOR GENERATION OF ELECTRONICALLY EXCITED RADICAL ION IN VERY EXOTHERMIC ELECTRON-TRANSFER FLUORESCENCE QUENCHING

  K KIKUCHI, T KATAGIRI, T NIWA, Y TAKAHASHI, T SUZUKI, H IKEDA, T MIYASHI

  CHEMICAL PHYSICS LETTERS 193 1-3 155 - 160 1992年05月 [査読有り][通常論文]
   

  The free radical yield of electron-transfer fluorescence quenching and the effective encounter distance are studied to determine the quenching mechanism in very exothermic region. Evidence for electronically excited radical generation as the primary quenching product is given for the first time.
• EVIDENCE FOR GENERATION OF ELECTRONICALLY EXCITED RADICAL ION IN VERY EXOTHERMIC ELECTRON-TRANSFER FLUORESCENCE QUENCHING

  K KIKUCHI, T KATAGIRI, T NIWA, Y TAKAHASHI, T SUZUKI, H IKEDA, T MIYASHI

  CHEMICAL PHYSICS LETTERS 193 1-3 155 - 160 1992年05月 [査読有り][通常論文]
   

  The free radical yield of electron-transfer fluorescence quenching and the effective encounter distance are studied to determine the quenching mechanism in very exothermic region. Evidence for electronically excited radical generation as the primary quenching product is given for the first time.
• CLATHRATE FORMATION AND MOLECULAR RECOGNITION BY NOVEL CHALCOGEN CYANO INTERACTIONS IN TETRACYANOQUINODIMETHANES FUSED WITH THIADIAZOLE AND SELENADIAZOLE RINGS

  T SUZUKI, H FUJII, Y YAMASHITA, C KABUTO, S TANAKA, M HARASAWA, T MUKAI, T MIYASHI

  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 114 8 3034 - 3043 1992年04月 [査読有り][通常論文]
   

  The intermolecular contacts between chalcogen atoms and cyano lone pairs were found to stabilize the crystalline state by electrostatic interaction. This interaction is one of the sources of the directionality in crystal packing of organic molecules and causes the formation of various types of inclusion lattices in the charge-transfer (CT) crystals of 1-3. By using highly selective formation of CT crystals with substituted aromatic hydrocarbons, particular isomers such as p-xylene or 2,6-dimethylnaphthalene (2,6-DMN) could be separated from the corresponding isomer mixtures. Lattice-related interaction plays a more significant role than molecular orbital interaction in the observed selectivity for para-disubstituted benzenes. However, the latter interaction is important for the recognition of 2,6-DMN from the 2,7 isomer.
• Tetrathienylethylenes, a New Class of Electron Donors—Dications Twisted by 90° Stabilized by Formation of Polymethine Units

  Takanori Suzuki, Hiroaki Shiohara, Masayuki Monobe, Tomoo Sakimura, Shoji Tanaka, Yoshiro Yamashita, Tsutomu Miyashi

  Angewandte Chemie International Edition in English 31 4 455 - 458 Wiley-Blackwell 1992年04月 [査読有り][通常論文]
   

  With a 90-degrees twist between the two halves, dication 1(2+) is the first ethylene dication with the maximum distortion possible. The stabilization of the positive charge is achieved in the separate halves of the dication by delocalization over polymethine units. 1(2+). whose ClO4- salt melts at about 170-degrees-C with decomposition, is obtained from the electrochemical oxidation of 1. The structure of neutral 1 differs substantially from that of its dication.
• TETRACYANOQUINODIMETHANES FUSED WITH 1,2,5-THIADIAZOLE AND PYRAZINE UNITS

  Y TSUBATA, T SUZUKI, Y YAMASHITA, T MUKAI, T MIYASHI

  HETEROCYCLES 33 1 337 - 348 1992年01月 [査読有り][通常論文]
   

  1,2,5-Thiadiazolopyrazino-TCNQs underwent reversible four-stage one-electron reduction and gave conductive CT complexes with some donors. The X-ray structural analysis of the unsubstituted derivative revealed that the coplanar ''sheet''-like network was formed by interatomic contacts of S--N = C and H--N = C in crystal.
• Metallic behavior stable against Peierls instability in the one-dimensional organic conductor tetraselenotetracene-bis(1,2,5-thiadiazolo)tetracyanoquinodimethane [(TSeT)-(BTDA-TCNQ)]

  A. Ugawa, K. Iwasaki, A. Kawamoto, K. Yakushi, Y. Yamashita, T. Suzuki

  Physical Review B 43 18 14718 - 14721 1991年 [査読有り][通常論文]
   

  Tetraselenotetracene (TSeT) forms a charge-transfer complex with bis(1,2,5-thiadiazolo)tetracyanoquinodimethane (BTDA-TCNQ), the complex showing a metallic behavior down to 1.5 K without undergoing a Peierls transition. The structure consists of segregated columns of TSeT and BTDA-TCNQ molecules, among which there also exist short intermolecular contacts. The polarized reflectance spectra indicate that the material is a one-dimensional metal in contrast to the structural features. The electronic structure is characterized by a one-dimensional conduction band lying on the two-dimensional lattice, which prevents the system from undergoing a Peierls distortion. © 1991 The American Physical Society.
• 4,7-Dimethyl-4,7-dihydro[1,2,5]thiadiazolo[3,4-b]-pyrazin, ein neuer Elektronendonor mit einem 12π-Elektronensystem

  Yoshiro Yamashita, Junko Eguchi, Takanori Suzuki, Chizuko Kabuto, Tsutomu Miyashi, Shoji Tanaka

  Angewandte Chemie 102 6 709 - 710 Wiley-Blackwell 1990年06月 [査読有り][通常論文]
  
• 4,7-Dimethyl-4,7-dihydro[1,2,5]thiadiazolo-[3,4-b]pyrazine, a Novel Electron Donor with a 12π-Electron Ring System

  Yoshiro Yamashita, Junko Eguchi, Takanori Suzuki, Chizuko Kabuto, Tsutomu Miyashi, Shoji Tanaka

  Angewandte Chemie International Edition in English 29 6 643 - 645 Wiley-Blackwell 1990年06月 [査読有り][通常論文]
  
• BENZO[G][1,2,5]THIADIAZOLO[3,4-B]QUINOXALINE-5,10-DIONE AND ITS SELENIUM ANALOG - AN UNUSUAL TYPE OF QUINONES

  Y YAMASHITA, Y TSUBATA, T SUZUKI, T MIYASHI, T MUKAI, S TANAKA

  CHEMISTRY LETTERS 3 445 - 448 1990年03月 [査読有り][通常論文]
  
• A novel reaction of thiirane cation radicals in solution: The formation of 5,6-diphenyl-1,2,3,4-tetrathianes through trisulphurated thiirane cation radical intermediates

  Kamata, M., Murayama, K., Suzuki, T., Miyashi, T.

  Journal of the Chemical Society, Chemical Communications 11 1990年
• 2,2'-(5,8-DIHYDROQUINOXALINE-5,8-DIYLIDENE)BIS(1,3-BENZODITHIOLE)S - A NEW TYPE OF ELECTRON-DONORS

  Y YAMASHITA, T SUZUKI, T MIYASHI

  CHEMISTRY LETTERS 9 1607 - 1610 1989年09月 [査読有り][通常論文]
  
• PREPARATION, PROPERTIES, AND CRYSTAL-STRUCTURE OF A 1,2,5-THIADIAZOLOTETRA-CYANOQUINODIMETHANE

  T SUZUKI, Y YAMASHITA, C KABUTO, T MIYASHI

  JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS 16 1102 - 1103 1989年08月 [査読有り][通常論文]
  
• PHOTOCYCLOADDITION REACTIONS OF TRICYCLO[3.3.1.0/2,8]NONA-3,6-DIEN-9-ONE (BARBARALONE) AND CARBONYL-COMPOUNDS

  T MIYASHI, A KONNO, Y TAKAHASHI, A KANEKO, T SUZUKI, T MUKAI, N KOGA, H IWAMURA

  TETRAHEDRON LETTERS 30 39 5297 - 5300 1989年 [査読有り][通常論文]
  
• BEDT-TTF COMPLEXES WITH PERCYANO SUBSTITUTED ORGANIC-ANIONS

  H YAMOCHI, T TSUJI, G SAITO, T SUZUKI, T MIYASHI, C KABUTO

  SYNTHETIC METALS 27 1-2 A479 - A484 1988年12月 [査読有り][通常論文]
  
• CRYSTAL-STRUCTURE OF BENZENE-BIS[1,2,5]THIADIAZOLOTETRACYANOQUINODIMETHANE (BTDA) COMPLEX - A WEAK CHARGE-TRANSFER COMPLEX STABILIZED BY INCLUSION BEHAVIOR

  T SUZUKI, C KABUTO, Y YAMASHITA, T MUKAI, T MIYASHI

  JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS 13 895 - 896 1988年07月 [査読有り][通常論文]
  
• FORMATION AND SPIN-DENSITY DISTRIBUTION OF THE RADICAL-ANION AND RADICAL TRIANION OF BIS[DIPHENYLPYRADINO]TETRACYANOQUINODIMETHANE STUDIED BY ELECTRON-SPIN-RESONANCE

  M HIRAYAMA, A SEKI, Y YAMASHITA, T SUZUKI, T MIYASHI

  CHEMISTRY LETTERS 5 769 - 772 1988年05月 [査読有り][通常論文]
  
• ELECTRON-SPIN-RESONANCE OBSERVATION OF THE RADICAL TRIANION AND RADICAL-ANION OF BIS(1,2,5-THIADIAZOLO)-TETRACYANOQUINODIMETHANE

  M HIRAYAMA, A SEKI, Y YAMASHITA, T SUZUKI, T MIYASHI

  JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS 7 490 - 491 1988年04月 [査読有り][通常論文]
  
• Bis([1,2,5]thiadiazolo)[3,4-b;3′,4′-e]pyrazin, ein neuer Heterocyclus mit 14 π-Elektronen und hoher Elektronenaffinität

  Yoshiro Yamashita, Kenichi Saito, Takanori Suzuki, Chizuko Kabuto, Toshio Mukai, Tsutomu Miyashi

  Angewandte Chemie 100 3 428 - 429 Wiley-Blackwell 1988年03月 [査読有り][通常論文]
  
• BIS([1,2,5]THIADIAZOLO)[3,4-B-3',4'-E]PYRAZINE, A NOVEL 14-PI-ELECTRON HETEROCYCLE WITH HIGH ELECTRON-AFFINITY

  Y YAMASHITA, K SAITO, T SUZUKI, C KABUTO, T MUKAI, T MIYASHI

  ANGEWANDTE CHEMIE-INTERNATIONAL EDITION IN ENGLISH 27 3 434 - 435 1988年03月 [査読有り][通常論文]
  
• A NEW TYPE OF TWO-DIMENSIONAL ORGANIC CONDUCTORS - ALKYLAMMONIUM BIS[1,2,5]THIADIAZOLOTETRACYANOQUINODIMETHANIDES

  T SUZUKI, C KABUTO, Y YAMASHITA, T MUKAI, T MIYASHI, G SAITO

  BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 61 2 483 - 493 1988年02月 [査読有り][通常論文]
  
• PHOTOCYCLIZATION OF NORBORNADIENES FUSED WITH QUINONE UNITS

  T SUZUKI, Y YAMASHITA, T MUKAI, T MIYASHI

  TETRAHEDRON LETTERS 29 12 1405 - 1408 1988年 [査読有り][通常論文]
  
• ELECTRON-SPIN-RESONANCE OF RADICAL-ANION AND RADICAL TRIANION OF [1,2,5]THIADIAZOLO-TETRACYANONAPHTHOQUINODIMETHANE

  M HIRAYAMA, A SEKI, Y YAMASHITA, T SUZUKI, T MIYASHI

  CHEMISTRY LETTERS 1 67 - 70 1988年01月 [査読有り][通常論文]
  
• ESR of radical anion and radical trianion of [1,2,5]thiadiazolo-tetracyanonaphthoquinodimethane.

  Masatoshi Hirayama, Akihiko Seki, Yoshiro Yamashita, Takanori Suzuki, Tsutomu Miyashi

  Chem. Lett. 1 67 - 70 1988年 [査読有り][通常論文]
  
• AN ANION RADICAL SALT OF A QUINONE FUSED WITH 1,3-DITHIOLE UNITS - CRYSTAL AND MOLECULAR-STRUCTURE OF A TETRAETHYLAMMONIUM SALT OF 2,6-DITHIOXOBENZO[1,2-D-4,5-D']- BIS[1,3]DITHIOLE-4,8-DIONE

  T SUZUKI, C KABUTO, Y YAMASHITA, T MIYASHI

  BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 60 9 3459 - 3461 1987年09月 [査読有り][通常論文]
  
• PREPARATION AND PROPERTIES OF THE DIANION AND THE DIHYDRO DERIVATIVE OF THE BIS[1,2,5]THIADIAZOLO DERIVATIVE OF TETRACYANOQUINODIMETHANE

  Y YAMASHITA, T SUZUKI, T MUKAI

  JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS 15 1184 - 1185 1987年08月 [査読有り][通常論文]
  
• CRYSTAL-STRUCTURE OF TTF.BTDA-TCNQ COMPLEX - A NEW TYPE OF CT COMPLEX WITH AN INCLUSION BEHAVIOR AND A MULTIDIMENSIONAL STRUCTURE

  T SUZUKI, C KABUTO, Y YAMASHITA, T MUKAI

  BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 60 6 2111 - 2115 1987年06月 [査読有り][通常論文]
  
• PREPARATION, PROPERTIES, AND CRYSTAL-STRUCTURE OF [1,2,5]SELENADIAZOLOTETRACYANONAPHTHOQUINODIMETHAN

  T SUZUKI, C KABUTO, Y YAMASHITA, T MUKAI

  CHEMISTRY LETTERS 6 1129 - 1132 1987年 [査読有り][通常論文]
  
• NOVEL QUINONE-TYPE ACCEPTORS FUSED WITH SULFUR HETEROCYCLES AND THEIR HIGHLY CONDUCTIVE COMPLEXES WITH ELECTRON-DONORS

  Y YAMASHITA, T SUZUKI, G SAITO, T MUKAI

  JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS 19 1489 - 1491 1986年10月 [査読有り][通常論文]
  
• CRYSTAL AND MOLECULAR-STRUCTURE OF BIS-1,2,5-THIADIAZOLOTETRACYANO-QUINODIMETHANE - A NOVAL ACCEPTOR FORMING HIGHLY CONDUCTIVE COMPLEXES

  C KABUTO, T SUZUKI, Y YAMASHITA, T MUKAI

  CHEMISTRY LETTERS 9 1433 - 1436 1986年09月 [査読有り][通常論文]
  
• PREPARATION AND PROPERTIES OF TETRACYANOQUINODIMETHANS FUSED WITH PYRAZINE UNITS

  Y YAMASHITA, T SUZUKI, G SAITO, T MUKAI

  CHEMISTRY LETTERS 5 715 - 718 1986年05月 [査読有り][通常論文]
  
• CRYSTAL-STRUCTURES OF MOLECULAR-COMPLEXES OF 2-CHLORO-11,11,12,12-TETRACYANOANTHRAQUINODIMETHANE WITH BENZENE (1-1) AND PYRENE (2-1) - A NOVEL TYPE OF CHARGE-TRANSFER COMPLEXES

  C KABUTO, Y FUKAZAWA, T SUZUKI, Y YAMASHITA, T MIYASHI, T MUKAI

  TETRAHEDRON LETTERS 27 8 925 - 928 1986年 [査読有り][通常論文]
  
• CRYSTAL-STRUCTURES OF MOLECULAR-COMPLEXES OF 2-CHLORO-11,11,12,12-TETRACYANOANTHRAQUINODIMETHANE WITH BENZENE (1-1) AND PYRENE (2-1) - A NOVEL TYPE OF CHARGE-TRANSFER COMPLEXES

  C KABUTO, Y FUKAZAWA, T SUZUKI, Y YAMASHITA, T MIYASHI, T MUKAI

  TETRAHEDRON LETTERS 27 8 925 - 928 1986年 [査読有り][通常論文]
  
• THE SYNTHESIS AND PROPERTIES OF 11, 11, 12, 12-TETRACYANOANTHRAQUINODIMETHAN AND ITS DERIVATIVES

  Y NISHIZAWA, T SUZUKI, Y YAMASHITA, T MIYASHI, T MUKAI

  NIPPON KAGAKU KAISHI 5 904 - 909 1985年 [査読有り][通常論文]
  
• PREPARATION AND PROPERTIES OF A TETRACYANOQUINODIMETHANE FUSED WITH 1,2,5-THIADIAZOLE UNITS

  Y YAMASHITA, T SUZUKI, T MUKAI, G SAITO

  JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS 15 1044 - 1045 1985年 [査読有り][通常論文]
  
• HIGHLY CONDUCTIVE COMPLEXES OF BIS-1,2,5-THIADIAZOLO-TETRACYANOQUINODIMETHAN (BTDA-TCNQ) WITH AMINES

  Y YAMASHITA, T SUZUKI, G SAITO, T MUKAI

  CHEMISTRY LETTERS 11 1759 - 1762 1985年 [査読有り][通常論文]
  
• CHARGE-TRANSFER COMPLEXES OF 11,11,12,12-TETRACYANOANTHRAQUINODIMETHANS WITH VARIOUS DONORS

  T MUKAI, T SUZUKI, Y YAMASHITA

  BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 58 8 2433 - 2434 1985年 [査読有り][通常論文]
  

講演・口頭発表等

• 動的酸化還元系の化学 （特別講演）  [招待講演]

  鈴木孝紀

  第３２回基礎有機化学討論会 2022年09月 口頭発表（基調）
• Hexaarylbutadienes Exhibiting NIR-electrochromism for the Development of H2S-Bioimaging and Photodynamic Therapy  [招待講演]

  Takanori Suzuki

  19th International Symposnium on Novel Aromatic Compounds 2022年07月 口頭発表（招待・特別）
• Studies on Dynamic Redox Systems: Construction of Record-breaking Strained Compounds and Development of Unimolecular Memory  [通常講演]

  鈴木 孝紀

  The 99th CSJ Annual Meeting, Award Lecutre, 2019年03月
• 超結合：共有結合の限界を超えた化学  [通常講演]

  鈴木 孝紀

  日本化学会第９9春季年会特別企画 2019年03月

その他活動・業績

• 柔軟なポリアリールキノジメタン誘導体:結晶擬多形中の立体配座に基づく特異な発光

  菅原一真, 小野利和, 鈴木孝紀, 石垣侑祐 基礎有機化学討論会要旨集 31st (CD-ROM) 2021年
• ビストリアリールメチリウム型大環状ジカチオンの近赤外メカノクロミック発光

  石垣侑祐, 立花拓哉, 菊池モト, 菅原一真, 鈴木孝紀 基礎有機化学討論会要旨集 31st (CD-ROM) 2021年
• 複数の14π芳香族ユニットが直交したジカチオンの特異な酸化還元挙動

  林裕貴, 鈴木孝紀, 石垣侑祐 基礎有機化学討論会要旨集 31st (CD-ROM) 2021年
• 電子授受による動的アセン制御:ヒステリシスを伴う三状態間の相互変換と近赤外吸収スイッチング

  張本尚, 菅原一真, 鈴木孝紀, 石垣侑祐 基礎有機化学討論会要旨集 31st (CD-ROM) 2021年
• 癌細胞増殖抑制作用を持つボタンイボタケ由来パラターフェニル化合物の合成展開

  藤原憲秀, 乗鞍敏夫, 佐藤たくと, 佐野勇介, 櫛部佳祐, 角田隆幸, 上遠野亮, 鈴木孝紀, 岩井邦久, 松江一 秋田応用生命科学研究会第26回講演会 2015年11月 [査読無し][通常論文]
  
• ガンバジュニンD,EおよびテレファンチンDの提出構造の合成

  藤原憲秀, 櫛部佳祐, 佐藤たくと, 乗鞍敏夫, 上遠野亮, 鈴木孝紀, 松江一 日本化学会講演予稿集 94th (4) 2014年
• 水溶性置換基を導入したジアリールエテニル型動的酸化還元系の多重出力型エレクトロクロミズム挙動

  上遠野亮, 花田佳祐, 日笠翔, 石垣侑祐, 藤原憲秀, 山田英俊, 鈴木孝紀 基礎有機化学討論会要旨集 24th 424 2013年08月22日 [査読無し][通常論文]
  
• p-ターフェニル天然物テレファンチンOの合成

  藤原憲秀, 佐藤たくと, 佐野勇介, 乗鞍敏夫, 上遠野亮, 鈴木孝紀, 松江一 日本化学会講演予稿集 93rd (4) 2013年
• ペクテノトキシン2の構造活性相関研究

  鈴木悠記, 藤原憲秀, 古関直, 上遠野亮, 鈴木孝紀, 乗鞍敏夫, 松江一 天然有機化合物討論会講演要旨集(Web) 55th 2013年
• 非対称置換1,1,2,2‐テトラアリールピラセンのフローマイクロ合成:極度に伸長したC‐C結合の置換基効果

  鈴木孝紀, 内村康人, 石垣侑祐, 上遠野亮, 藤原憲秀, 永木愛一郎, 吉田潤一 基礎有機化学討論会要旨集 23rd 389 2012年09月05日 [査読無し][通常論文]
  
• 5,6‐位に異なる置換基を有するアセナフテン誘導体の効率的なフローマイクロ合成と特異な分子構造

  鈴木孝紀, 内村康人, 石垣侑祐, 上遠野亮, 藤原憲秀, 永木愛一郎, 吉田潤一 化学系学協会北海道支部冬季研究発表会講演要旨集 2012 11 2012年01月31日 [査読無し][通常論文]
  
• 貝毒ペクテノトキシン2の全合成

  鈴木悠記, 藤原憲秀, 古関直, 菊地悠太, 村田俊一, 安藝祐一, 岡野梓, 山本冬樹, 河村真理子, 志賀俊介, 村井章夫, 上遠野亮, 河合英敏, 鈴木孝紀, 乗鞍敏夫, 松江一 万有生命科学振興国際交流財団福岡シンポジウム 22nd 2012年
• 三色エレクトロクロミズムを示す非対称ヘキサフェニルエタン誘導体:フローマイクロ法による効率合成と分子内不斉誘導

  石垣侑祐, 河合英敏, 藤原憲秀, 鈴木孝紀, 永木愛一郎, 吉田潤一 基礎有機化学討論会要旨集 22nd 423 2011年09月07日 [査読無し][通常論文]
  
• 点不斉を持つ非対称ヘキサフェニルエタン誘導体:フローマイクロ法による効率合成と特異なエレクトロクロミズム挙動

  石垣侑祐, 河合英敏, 藤原憲秀, 鈴木孝紀, 永木愛一郎, 吉田潤一 日本化学会講演予稿集 91st (4) 1481 2011年03月11日 [査読無し][通常論文]
  
• ペクテノトキシン2の全合成

  藤原憲秀, 鈴木悠記, 古関直, 菊地悠太, 村田俊一, 安藝祐一, 山本冬樹, 河村真理子, 岡野梓, 村井章夫, 河合英敏, 鈴木孝紀, 乗鞍敏夫, 松江一 天然有機化合物討論会講演要旨集 53rd 2011年
• マイクロフロー法により効率合成が可能となった非対称ヘキサフェニルエタン誘導体の特異なエレクトロクロミズム挙動

  石垣侑祐, 西田純一, 河合英敏, 藤原憲秀, 鈴木孝紀, 永木愛一郎, 高林尚史, 吉田潤一 基礎有機化学討論会要旨集 21st 337 2010年09月02日 [査読無し][通常論文]
  
• イミン架橋型ロタキサンの構築と加水分解平衡に与えるイミン架橋ステーションの構造的影響

  河合英敏, 杉野寛佳, 梅原健志, 藤原憲秀, 鈴木孝紀 基礎有機化学討論会予稿集 2P062 2008年 [査読無し][通常論文]
  
• 新規ロタキサン構築法としてのイミン架橋型スレッディングの適用性調査

  河合英敏, 杉野寛佳, 梅原健志, 藤原憲秀, 鈴木孝紀 構造有機化学討論会要旨集 1P-36 2007年 [査読無し][通常論文]
  
• Tetraaryl-o-quinodimethanes: Reductive generation and severely distorted geometry

  Shinichi Iwashita, Takanori Suzuki JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN 64 (9) 958 -968 2006年09月 [査読無し][通常論文]
   

  Introduction of four aryl groups on the highly reactive omicron-quinodimethane (omicron-QDM) skeleton suppresses the intermolecular reactivities. Thus, the unimolecular isomerization through electro-cyclization is the major decomposition path for title molecules. Rational design can prevent thermal isomerization of Ar-4-omicron-QDMs. A new general procedure to generate Ar-4-omicron-QDM has been established here that includes two-electron reduction of the corresponding dications, whose reaction conditions no longer promote electrocyclization of Ar-4-omicron-QDM. Several derivatives of Ar-4-omicron-QDM with the dihydrophenanthrene, dibenzoperylene, or acenaphthene skeleton were isolated for the first time, and the details on their highly strained molecular structures were investigated by low-temperature X-ray analyses. Based on the reversible interconversion between Ar-4-omicron-QDMs and the precursor dications, they represent a new class of electrochromic redox pairs.
• Enantio- and stereocontrolled formation of the bisspiroacetal core of spirolide B

  Ishihara, J., Ishizaka, T., Suzuki, T., Hatakeyama, S. Tetrahedron Letters 45 (42) 7855 -7858 2004年 [査読無し][通常論文]
  
• ESR of the π- Radical Formed by Photoreduction of Bis(1,2,5-selenadiazolo)-tetracyanoquinodimethane in Methanol. Observation of a Large ^<77>Se Hfs

  HIRAYAMA Masatoshi, TERASAKA Toshitaka, MORITA Yoichi, SUZUKI Takanori, YAMASHITA Yosiro, MIYASHI Tsutomu Chemistry letters 1995 (11) 1021 -1022 1995年 [査読無し][通常論文]
   

  A large ⁷⁷Se hfs was observed in the ESR spectrum of a radical generated by photoreduction of the electron acceptor, BSDA-TCNQ(3), with 355 nm laser irradiation in methanol. This spectrum was identified as the anion radical of a proton adduct of 3, which was supported by the MO calculation.
• Benzidine type electron donors fused with 1,2,5-chalcogenadiazole units

  Suzuki, T., Okubo, T., Okada, A., Yamashita, Y., Miyashi, T. Heterocycles 35 (1) 395 -406 1993年 [査読無し][通常論文]
  
• Preparation and properties of tetracyanoquinodimethane radical-anion salts with azaazulenium and diazaazulenium ions

  Yamashita, Y., Suzuki, T., Kobayashi, Y., Mukai, T., Miyashi, T. Synthetic Metals 45 (2) 213 -220 1991年 [査読無し][通常論文]
  
• Preparation and crystal structures of tetracyanoquinodimethans fused with [1,2,5]selenadiazole units.

  Suzuki Takanori, Kabuto Chizuko, Yamashita Yoshiro, Saito Gunzi, Mukai Toshio, Miyashi Tsutomu Chemistry Letters (11) 2285 -2288 1987年 [査読無し][通常論文]
   

  The title electron acceptors, TSDA (2) and BSDA (3), were prepared which crystallize isomorphously with the sulfur analogue, BTDA (1). The molecular interactions are enhanced in 2 and 3 compared with 1, which connect the molecules to form two-dimensionally expanded "sheet-like" networks and their infinite layers.
• 芳香族環および複素環の縮合したテトラシアノキノジメタン類の合成と性質 (導電材料とその応用) -- (電子伝導)

  山下 敬郎, 鈴木 孝紀, 向井 利夫 日本化学会誌 1986 (3) p268 -275 1986年03月
• The Synthesis and Properties of Tetracyanoquinodimethans Fused with Aromatic Rings and Heterocyclic Rings

  Yamashita, Y., Suzuki, T., Mukai, T. Nippon Kagaku Kaishi 1986 (3) 268 -275 1986年 [査読無し][通常論文]
  

特許

• 特願2004-265909:新規なビキサンテン化合物およびビスキサンテニリウム化合物とその製造方法、およびその用途  2004年

  鈴木孝紀, 藤原憲秀, 河合英敏, 田中祥子, 樋口博紀
• 特願2004-031074:新規なビアクリダン化合物およびビスアクリジニウム化合物とその製造法、およびその用途  2004年

  鈴木孝紀, 辻孝, 藤原憲秀, 河合英敏, 樋口博紀, 右田章, 太田賢司
• 特開平2-076830:2,6-ジメチルナフタレンの分離方法  1990年03月16日

  宮仕 勉, 山下 敬郎, 鈴木 孝紀, 藤井 宏  三菱石油株式会社  201103045531160719
• 特開平1-160925:パラキシレンの分離方法  1989年06月23日

  宮仕 勉, 向井 利夫, 山下 敬郎, 鈴木 孝紀, 藤井 宏  三菱石油株式会社  201103099450724858
• 特開昭63-150273:ベンゾキノン誘導体と電子供与体との電荷移動錯体の製造方法  1988年06月22日

  向井 利夫, 山下 敬郎, 鈴木 孝紀  富士ゼロックス株式会社, 向井 利夫  201103059002566719
• 特開昭62-033157:新規化合物、その化合物と電子供与体との電荷移動錯体、及びその化合物の陰イオンあるいは陰イオンラジカルの塩  1987年02月13日

  向井 利夫, 山下 敬郎, 鈴木 孝紀  向井 利夫, 富士ゼロックス株式会社  201103092639449055

受賞

• 2019年03月 日本化学会学術賞
   

  受賞者: 鈴木 孝紀
• 2004年09月 第一回野副鉄男教授記念奨励賞
   

  受賞者: 鈴木 孝紀
• 1996年03月 日本化学会進歩賞
   

  受賞者: 鈴木 孝紀

共同研究・競争的資金等の研究課題

• 有機エレクトロクロミック物質の新展開：近赤外光スイッチによるバイオイメージング

  日本学術振興会：科学研究費助成事業 基盤研究(B)

  研究期間 : 2020年04月 -2025年03月 

  代表者 : 鈴木 孝紀, 石垣 侑祐

   

  研究計画に沿った研究実験を実施し、その実績について、”Generation of hydroxyl radical-activatable ratiometric near-infrared bimodal probes for early monitoring of tumor response to therapy.”L. Wu, Y. Ishigaki, W. Zeng, T. Harimoto, B. Yin, Y. Chen, S. Liao, Y. Liu, Y. Sun, X. Zhang, Y. Liu, Y. Liang, P. Sun, T. Suzuki, G. Song, Q. Fan, D. Ye, Nat. Commun. 2021, 12, 6145. [DOI: 10.1038/s41467-021-26380-y (open access)]の論文にて発表した。
  上記論文では、生体内のヒドロキシラジカルを選択的に検知してイメージングを行う方法を開拓したものであり、ヘキサアリールブタジエン骨格に、適切なアルキル基の置換したアミノ基を導入した化合物が有効であった。またNIR蛍光によるイメージングに、NIR吸収に由来する光音響分光スペクトルを併用することで、定量性の高い手法として確立できた点は特筆に値する。
  一方、物質開発については、ヘキサアリールブタジエンの基本骨格を持ちながらも、酸化還元に際して分子内に反芳香族性骨格であるチエピン、オキセピン骨格が生じることで、よりNIRの長波長部分に吸収をもつ化合物群についての検討を中心に進める計画であった。当該物質の合成には成功しており、今後そのスペクトル特性とイメージング法への応用へ進む段階である。
• 電位入力型ON/OFF機能の付与された双安定性分子ジャンクションの創成

  日本学術振興会：科学研究費助成事業 挑戦的研究(萌芽)

  研究期間 : 2020年07月 -2023年03月 

  代表者 : 鈴木 孝紀

   

  「電位入力型ON/OFF機能の付与された双安定性分子ジャンクションの創成」に関する本研究課題では、分子薄膜の両面に電極が接合された分子ジャンクションについて、エレクトロニクスの高速化とダウンサイジングに不可欠な将来的技術であることを鑑み、薄膜を構成する分子の導電性が外部刺激によって変化する設計のもとで、分子ジャンクションにON/OFF機能を付与する挑戦的内容である。国立シンガポール大学C.A.Nijhuis教授との国際共同研究として実施する。電極接合については、Nijhuis教授らが持つ共融ガリウム-インジウム電極の蒸着技術を用い、Au/分子薄膜//GaOx/EGaIn型のデバイスを構築する。 初年度は、中性分子の酸化電位と新たなC-C結合が形成されることによる二価陽イオン種還元電位に1Vもの差を伴う電気化学的双安定性をもった系として、ビフェニル(BP)とジヒドロフェナントレン(DHP)骨格の変換する動的酸化還元対をモチーフとした分子の合成をおこなった。最終的に、酸化還元部位に対して、金表面に結合可能な２つのジスルフィド部位を有する一連の化合物群を合成した。酸化還元骨格上に導入する置換基によって、動作電位が変化させられることをサイクリックポルタンメトリーで確認した。具体的には、同じアミン系置換基であっても、ピロリジノ基、ジメチルアミノ基、モルホリノ基では、０．３Ｖの変化を観測した。その際、以前に検討したプロトタイプでの問題点であった、遅い結合切断の過程による、変換速度の問題を克服する点を解決できたことも確認した。
• ドナーアクセプター連結型中分子による生物機能/光機能分子創出

  文部科学省：科学研究費補助金（新学術領域（研究領域提案型））

  研究期間 : 2018年04月 -2020年03月 

  代表者 : 鈴木 孝紀
• 安定な1,4-ジイルジカチオンの発生/消失に伴うモノマー/ポリマースイッチング

  文部科学省：科学研究費補助金（競争的萌芽研究）

  研究期間 : 2016年04月 -2019年03月 

  代表者 : 鈴木 孝紀
• 単一有機分子ｎビットメモリ及び抵抗可変型分子ワイヤの提案とそのプロトタイプの創成

  文部科学省：科学研究費補助金(基盤研究(B))

  研究期間 : 2015年 -2019年 

  代表者 : 鈴木 孝紀

   

  中性の電子供与体とカチオン種の相互変換に際してC-C結合の可逆な形成/切断や非常に大きな分子構造変化の起こるdyrex系は、従前の酸化還元系と比べて、開殻中間体の定常濃度が低いこと、及び、酸化電位と還元電位の差異が大きく電気化学的双安定性を有すること、という２つの特徴を持つ。これらは電子授受前後の大きな構造変化に基づく特性であり、個々の分子が１ビットを担う単一分子メモリとなり得る。本研究では、dyrex系を共役鎖でπ拡張した分子が、電子授受で共役のON/OFFスイッチングな”可変抵抗型分子ワイヤ”や”ｎビットメモリ”となり得ることを、そのプロトタイプの構築と特性調査から明らかにした。
• マルチレドックスサイト型オリゴマー中分子による生物機能分子創出

  文部科学省：科学研究費補助金（新学術領域（研究領域提案型））

  研究期間 : 2016年04月 -2018年03月 

  代表者 : 鈴木 孝紀
• イミン架橋制御により動的挙動と動的平衡を制御するダイナミック分子システムの開発

  日本学術振興会：科学研究費助成事業

  研究期間 : 2012年04月 -2015年03月 

  代表者 : 河合 英敏, 鈴木 孝紀

   

  本研究では“イミン架橋制御に基づく構造と運動性の制御”や“非線形的応答を示すアロステリック会合能”を、様々な分子モチーフに適用することによる新たな動的構造制御システム構築を目的とし、①アロステリック会合型超分子ポリマーにおける重合度保持効果、②アロステリック会合能とイミン結合形成を組み合わせた3成分系超分子ポリマーの構築、③分子ギア型アロステリックレセプターの開発、④複数の安定状態を制御できるイミン架橋型ロタキサンの開発、⑤分子ジャイロを指向した籠型分子の構築、⑥アトロプ異性とイミン結合形成、分子認識能を組み合わせることによる分子メモリーを有するマクロサイクルの開発を行った。
• 超分子ロッド：ＭＦＭＳ概念に基づく分子設計の検証

  文部科学省：科学研究費補助金(挑戦的萌芽研究)

  研究期間 : 2013年 -2014年 

  代表者 : 鈴木 孝紀

   

  本申請中でのもっとも重要な命題（MFMS）Maximum Function on Minimum Skeleton（MFMS）は、「如何にして単純な骨格に多用な機能を盛り込むか」であり、今年度は、熱・光・電場などの外部刺激に対してその物性値を可逆的に変化させる応答性分子に注目した。C9,C10位にジ（スピロアクリダン）骨格の置換したジヒドロフェナントレン誘導体1aはヘキサフェニルエタンと類似した部分構造を持ち、電気化学的入力に対してC9－C10『エタン結合』の切断による安定なジカチオン2a2+の生成を伴いながら、UV-Visおよび蛍光スペクトルの変化する多重出力エレクトロクロミズム応答を示す。1a及び2a2+はいずれもヘリシティ、軸不斉といった不斉要素を持つが、室温でもその立体配置は容易に反転する。一方、適切な分子設計を行い1a及び2a2+の立体反転を抑制すれば、ジヒドロフェナントレン誘導体キラルカラムを用いた光学分割が可能であり、また、立体配置を保ったまま対応するジカチオンと相互変換できると考えた。実際にC4,C5位にメチル基を導入した1bやジベンゾ縮環体1cを新たに合成して検討を進めたところ、、1b,cや2b,c2+の立体配置は安定であり、ねじれたπ系を有する光学活性な酸化還元対が非常に大きな円二色性（CD）を示すため、1b,c/2b,c2+の電気化学的相互変換では、これまでの応答に加えCDを更なる出力とした多重出力応答挙動を示すことが明らかとなった。これは、既存の骨格にごく小さな構造的摂動を加えることで、新たな機能を付与できたこと示す例であり、MFMSの遂行が成功したことを意味する。
• 新しい水素結合ネットワーク素材としての縮環マロナミド：次元制御構造構築とその応用

  日本学術振興会：科学研究費助成事業

  研究期間 : 2011年 -2013年 

  代表者 : 河合 英敏, 鈴木 孝紀

   

  本研究では、非常に単純な化合物であるインダンジカルボキサミド誘導体が水素結合形成により強固な２次元シート構造へと集合することを利用し、その構造修飾により多様な構造の次元制御とその応用を目的として研究を行った。種々の置換様式からなる縮環マロナミドはいずれも高い信頼性で２次元シート構造へと集合し、縮環構造の幅の広さに応じシート間の重なり方が制御可能であることを明らかにした。また、両端に縮環マロナミド構造をもつ誘導体では、内部に溶媒分子を取り込んだ３次元格子構造を形成すること、さらに嵩高いトリプチセン骨格を縮環した誘導体では、シートがまるまることで１次元チューブ構造を形成することを明らかにした。
• 集合化を特徴とする動的酸化還元系分子の集積合成：次元的秩序性の外部刺激制御

  文部科学省：科学研究費補助金(新学術領域研究(研究領域提案型))

  研究期間 : 2009年 -2013年 

  代表者 : 鈴木 孝紀

   

  外部刺激に対してその物性値を可逆的に変化させる応答性分子は、将来的に分子素子への展開が期待されるほか、表示材料やメモリーとしての応用が可能である。電気化学的な入力に対して色調を変化させるエレクロトクロミズム系はその代表例であり、可逆な酸化還元反応を行う物質群がその役割を担う。電子授受に際して可逆なC-C 結合の形成／切断を伴う動的酸化還元系は電気化学的双安定性を特徴とし、その機能開発に際して優位性を持つ。本研究では、[1] 集積合成法を駆使して初めて入手可能となった新規物質について、[2]新規に開発された集積合成法により入手可能となった様々な新規物質について、その特異な機能開発研究を実施した
• 世界記録に挑戦する化合物:最長の炭素-炭素結合と超原子価

  文部科学省：科学研究費補助金(基盤研究(B))

  研究期間 : 2009年 -2011年 

  代表者 : 鈴木 孝紀, 藤原 憲秀, 河合 英敏

   

  代表者らは、ヘキサフェニルエタン型分子に関するこれまで10年間の結果をもとに考察を行い、その結合の解裂で生じるジラジカル状態が立体的に近接位に強制されたままであり、且つ、共鳴やペリ環状反応によって閉殻構造に変換されないという条件を満たせば、これまでの常識を超える極度に長い結合を観測できると考えた。この予想をもとにテトラアリールピラセン型分子をモチーフとした研究を行い、中性有機分子での世界最長結合[1.791(3)Å]の観測、及び、長い結合ほど更に結合長が変化し易いという「伸長性」を発見した。
• 動的シクロファン:新しい分子応答系の提案

  文部科学省：科学研究費補助金(萌芽研究)

  研究期間 : 2005年 -2007年 

  代表者 : 鈴木 孝紀, 藤原 憲秀, 河合 英敏

   

  申請者は本課題の中で「動的シクロファン」という概念を提案した。これは、外部刺激によってシクロファンの持つ歪みや骨格構造に摂動を与え、それに付随する渡環相互作用の変化やシクロファンに特徴的な物性値変化を応答出力として取り出すというユニークな試みである。これまでテレフタルアミドの様々誘導体へのp-キシリレンジアンモニウム型ゲストの添加による「超分子シクロファン」の検討を行っている。例えば、応答型レセプター機能を持つシクロファンについての検討を行い、分子内に2つのテレフタルアミド骨格を持ち、,これらが二組の1,4-ビス(フェニルエチニル)ベンゼン発色団で架橋された大環状シクロファンについては、不斉なゲストを錯形成させた時、ゲストのエナンチオマーの一方はねじれ構造への変形を引き起こすが、その鏡像体との錯形成ではホストは長方形の構造のままで変形が誘起されないという興味深い結果が得られている。これらは、円二色性(CD)出力を合わせ持つシグナリングホストとなることものである。上記の成果に基づき今年度は、6置換ベンゼンとなる2,3,5,6-テトラアリールテレフタルアミドをモチーフとして、これらが1)非会合状態ではアミドがアンチ配座となり6つの置換基は非プロペラ配置をとる、2)ジアンモニウムが会合して超分子シクロファンとなると、シン配座になったアミド基のdirecting効果により、プロペラ配座に変化する、3)点不斉の情報がプロペラ構造の動的なヘリシティに効果的に転写されることで動的応答挙動が付与される、という分子プロペラの系を確立に成功した(投稿中)
• 集積型酸化還元系が発現する複合機能の探求と単一分子メモリへの展開

  文部科学省：科学研究費補助金(基盤研究(B))

  研究期間 : 2003年 -2005年 

  代表者 : 鈴木 孝紀, 藤原 憲秀

   

  代表者は、電子移動と結合の組み替えがカップルした「動的酸化還元挙動」に着目し、この独自の概念に基づく分子応答系の構築を行った。本課題の直接的な目的は、応答系を分子素子へと展開しようとする際の新しいパラダイムの創出することであり、その具体的内容は以下の3つである。それらは(1)「動的」挙動を示す電場応答性分子を二次元に集積し、超高密度記録材料を構築するという「単一分子メモリ」の概念を提案し、そのプロトタイプを提示すること;(2)分子集積化に利用できる「新規な超分子リンカー」を探求し、それを基板表面修飾法として利用すること;(3)電子移動とカップルした結合の組み替えが、凝縮相全体の相転移を誘起する「動的液晶相」の創成を行うこと。期間内に、(1)については、ジスルフィドやエチニル基に代表される表面修飾能を持った分子の合成に成功するとともに、多重出力および多重入力型応答機能の実現に成功した。(2)については、ポリエーテル骨格の集合能に着目し、海産天然物にも見られる梯子型ポリエーテルの収束的合成法の開発とその方法論の有効性を示した。いくつかの部分骨格についてはX線構造解析を行い、CH--O水素結合による集合化を確認した。(3)については、パイ骨格の遠隔位に2つのジアリールエテニル基を導入した一連の電子供与性化合物の合成を行い、酸化還元によって可逆なモノマー-オリゴマー変換の起こる系を実現した。分子に長鎖アルキル基を持つアミノフェニル基へと置換することで、ゲル相も現れることから、バルク凝縮相のマクロな挙動を酸化還元によって制御できる系へ発展できることを示した。
• 不斉表面の電気化学的応答とその機能

  文部科学省：科学研究費補助金(萌芽研究)

  研究期間 : 2002年 -2004年 

  代表者 : 鈴木 孝紀

   

  本研究課題の目的は、1)不斉要素を有する有機酸化還元系の構築とその応答機能を開発し、2)それらを表面へと固定できる方法論を応用して表面物性としての機能を引き出すことにある。本年度はそれぞれ、1)テトラヒドロフェナントラアゼピン骨格を有する系の開発、2)表面修飾に利用できるアンカー置換基を有する酸化還元系の開発について検討を行った。a)アゼピン骨格を有するキラルな酸化還元系:不斉要素を有する有機酸化還元系は、電気化学的入力に対して電子スペクトル及び円二色性(CD)スペクトルの双方の出力を与える多重出力型分子応答系となる。大きなCD出力を得るためには、エキシトンカップリングの利用できる軸不斉またはらせん状化合物が望ましい。表題骨格のヘリシティは容易に反転するが、N上にキラルなベンジルアミノ基を導入することで一方のジアステレオマーを優先させることに成功した。これにより、煩雑な光学分割を行わずに感度良くエレクトロキロオプティカル出力が得られる系の構築が可能となった。b)末端アセチレンおよびジスルフィド官能基をする酸化還元系:表面での自己組織化膜の形成を行うためには、表面修飾に利用できるアンカー置換基が導入された機能性酸化還元系を合成する必要がある。これまで動的酸化還元活性が確認されたジスピロジヒドロフェナントレン骨格を有する3種の酸化還元対の、a)ベイ領域へのエチニル基に導入、b)スピロ環上へのプロパルギル基の導入、c)ベイ領域へのジスルフィド官能基の導入された化合物の合成に成功した。前2者は水素終端シリコン表面への固定に、後者は金表面への固定に利用できる官能基を有するものであり、現在膜の調製の検討を行っている。
• 新しい分子応答系:エレクトロキロオプティクス

  文部科学省：科学研究費補助金(基盤研究(B))

  研究期間 : 2001年 -2002年 

  代表者 : 鈴木 孝紀, 辻 孝

   

  多重出力型分子応答系の構築を目指した本研究課題の目的は、電気化学的入力に対して、UV-Vis及びCD(円2色性)という2つのスペクトル出力が得られるエレクトロキロオプティカル(ECO)応答系の構築である。この研究を通じて、単に例の少ない応答系の成功例を増やすばかりではなく、どのような酸化還元対が有効なECO系になり得るのかという分子設計指針が得られたものと確信する。ECO系構築における問題点の1つは、他の応答系の場合と同様、如何にして双安定性を獲得するかという点である。これについては、代表者のこれまでの成果をもとに、「動的酸化還元挙動」を利用すること容易にクリアすることができた。一方、ECO系に特有の問題点としては、如何にして大きなキロオプティカル出力を発生させるかという点がある。即ち、通常の酸化還元対にキラルな置換基を結合させるだけでは、有効なECO系は構築不可能なのである。ここではヘリカルな構造を有するπ電子系を利用すること、また、同一のクロモフォアを2つ組み込み、その間でエキシトンカップリングを起こさせること、という手法を採用することで、非常に大きなCD出力を得ることに成功している。更に、UV-Vis及びCD出力の検出が長波長領域でも可能な化合物の探求、並びに、ECO以外の多重出力型応答系の構築へも研究を展開することができた。後者に関しては特に、高感度検出の可能な蛍光スペクトル出力型分子を合成することで、電気化学的入力に対し、UV-Vis及び蛍光を出力とする、エレクトロフルオリック応答系の構築に成功した。この結果を基に、UV-Vis、CD、蛍光という3つの出力を与える応答系への道も開かれた。
• 特異なスピン共役系の関係と展開

  日本学術振興会：科学研究費助成事業

  研究期間 : 1998年 -2000年 

  代表者 : 小林 啓二, 石黒 勝也, 井上 克己, 岡田 恵次, 阿波賀 邦夫, 鈴木 孝紀, 富岡 秀雄

   

  主な研究実績は以下の三つに大別することができる。 新しい安定スピン共役電子系の開発:立体保護により、半減期が室温で10分近くに及ぶ非常に安定な三重項カルベンを開発した。安定なラジカル種により構成される単一成分分子性金属が見い出された。また、キラルな構造を有する不斉ラジカル種の開発に成功し、不斉分子磁石の構築への指針が提示された。 集合体としてのスピン共役電子系の設計と性質:窒素二座型配位子を中心に、スピン共役電子系を配位子とする自己集積型金属錯体による高スピン種の開発が行われ、配位子におけるスピン伝達の様式が解析できた。また、室温をまたいで磁気的双安定性を示すラジカル集合体結晶が発見され、室温での磁気的性質のスイッチング現象を実現させた。 外部応答を示す動的なスピン共役電子系の研究:プロトン濃度に依存して双極イオン構造とビラジカル構造との平衡が成立する分子開発した。酸性度を磁性をプローブとして計測する方法論の基礎が検討された。電気化学的反応系でも、このようなイオン反応が絡む電子構造スイッチング反応が見い出された。電荷移動を固体摩砕により誘起できることが分かった。固相中に開殻分子種を発生させる手法へと展開が計られ、さらに固相反応の触媒的役割が明らかになった。
• 多点相互作用反応・場として機能する新規環状構造の開発

  日本学術振興会：科学研究費助成事業

  研究期間 : 1999年 -1999年 

  代表者 : 辻 孝, 大北 雅一, 鈴木 孝紀

   

  分子認識や自己認識化には、当該分子が分子形状を維持する剛直性と状況に適応し得る柔軟性を併せ備えていることが求められる。本研究では、5員環部が還元されたインダセンがそのような特性を備え、適切に異なる官能基によって構造修飾することにより、三次元的な相互作用を制御できる点に着目した。 1.インダセン骨格を利用した新規ホスト化合物の合成 5員環はenvelop型配座をとっており、(Z)-置換体では嵩高さの小さな基はaxial位をとってπ-πstacking構造の錯体を形成するのに適した約7.0Aの距離をおいてほぼ平行に配列される。(Z)-置換誘導体の結晶構造解析は、計算による予測を裏付けた。また、2分子が歯車のように互いに噛み合った興味深い結晶構造を明らかにした。若干の置換アリールエチニル体を合成し、そのホスト分子としての機能に検討を加えた。その結果、CT吸収強度に(Z)-体と(E)-体では約9倍の差が認められ、(Z)-体とのより強い錯体形成が認められた。 対応する(E)-置換体では、より嵩高い置換基がequatorial配座をとって逆方向に配列される。4-ピリジル/メトキシカルボニル置換体のX線構造解析は、このことを実証した。共有結合あるいは金属への配列を利用して大環状構造を構築すれば、官能基を大環状構造の環内方向に配列させることができる。大環状の構築とその基質の取り組みの選択性と触媒機能を継続課題として解明する計画である。 2.官能基化したパラフェニレン/エチニレン型マクロサイクルの合成 先に合成を報告したジクロロDewarベンゼンが、官能基化したメタおよびパラフェニレン構造をその折れ曲がり構造を利用して大環状構造に組み込むための合成素子として有用であることを見い出した。1, 2-ジエチニルベンセンとの交互(2:2)環化カップリング、および1,3-ジエチニルベンゼン等価体との(2:4)環化カップリング、保護基の交換、光芳香環化によって官能基化したパラフェニレン/エチニレン型マクロサイクルが得られた。それらのキラル性、空孔への基質特異的取り組みと官能基による活性化は今後の検討課題である。
• 包接・自己集合・自己組織化能を有する新規環状構造の構築と機能開発

  日本学術振興会：科学研究費助成事業

  研究期間 : 1998年 -1999年 

  代表者 : 辻 孝, 大北 雅一, 今井 敏郎, 鈴木 孝紀

   

  本研究では、高度かつ組織的に官能基化された篭形およびチャンネル形成能をもつ大環状化合物を合成し、新規な多点相互作用反応場としての機能を開発することを目指した。 1.インダセン骨格を利用した新規ホスト化合物の合成 (a)π-π stackingに適合した鋏形構造の合成と分子認識 剛直な芳香環と柔軟性をもつ5員環から構成されたインダセン骨格Iは適度な自由度をもつと共に、芳香環および両端の5員環を適切にそれぞれ異なる官能基によって構造修飾することにより、三次元的相互作用を制御できると考えられる。Iの5員環はenvelope形配座をとっており、(Z)-置換体IIでは嵩高さの小さな基はaxial位をとってπ-πstacking構造の錯体を形成するのに適した約7.0Aの距離をおいてほぼ平行に配列されることを見い出した。また、2分子が歯車のように互いに噛み合った興味深い結晶構造を明らかにした。置換アリールエチニル体のホスト分子としての機能に検討を加えた。その結果、(Z)-体がより強い錯体形成能を示すことが示唆された。 (b)多官能基化した空孔をもつ環状構造の構築 アリール基を導入するとequatorial配座優先性は高く、COOR基やCH_2OH基は分子平面に対しほぼ垂直のaxial配座をとることを見い出した。共有結合あるいは金属への配位を利用して大環状構造を構築すれば、それらの基を大環状構造の環内方向に配向させることができる。大環状の構築とその基質取り込みの選択性と触媒機能を、継続課題として解明する計画である。 2.官能基化したパラフェニレン基を組み込んだマクロサイクルの合成 規制された配置をとって官能基化された剛直な大環状構造は、分子認識による錯形成や自己会合による組織体形成等の観点から注目されている。先に比較的容易に合成できることを報告したジクロロDewarベンゼンは、官能基化したメタおよびパラフェニレン構造をその折れ曲がり構造を利用して大環状構造に組み込むための合成素子として有用である。1,2-ジエチニルベンゼンとの交互(2:2)環化カップリング、および、1,3-ジエチニルベンゼン等価体との(2:4)環化カップリング、保護基の交換、光芳香環化によってパラフェニレン/エチニレン型マクロサイクルを得た。他の方法では困難な官能基化したメタおよびパラフェニレン基を組み込んだマクロサイクルの合成が可能と考えられる。
• インダン骨格を利用した超分子形成能を有する基質設計を機能開発

  日本学術振興会：科学研究費助成事業

  研究期間 : 1998年 -1998年 

  代表者 : 辻 孝, 大北 雅一, 今井 敏郎, 鈴木 孝紀

   

  ベンゼン環の両側に飽和5員環が縮環したヘキサヒドロインダセン骨格では、両末端の5員環上の置換基とベンゼン環上の置換基が直交した配向をとることを特徴とする。その結果、それらの置換基を操作することによりx,y,z3軸方向での分子間相互作用を制御できる。本研究では、5員環およびベンゼン環上に水素結合能や金属配位能を有する置換基を導入したインダセン誘導体と、その骨格を複数個環状に結合したマクロサイクルを設計し、その合成と超分子形成能に検討をくわえた。 1. 官能基化したヘキサヒドロインダセン誘導体の合成に関する報告は少ない。そこで、ベンゼン環上に官能基変換が可能なメトキシ基、また、5員環にカルボニル、カルボキシル基等を導入した誘導体の合成法の開発を行い、それらの誘導体合成への道を開いた。 2. ベンゼン環に縮環した5員環は、カルボニル基や二重結合の導入によりベンゼン環と共平面に固定されるが、飽和の場合には比較的大きな配座自由度をもつ。その特性を利用した超分子形成能を有する基質の設計と官能基による構造修飾の可能性に検討を加えた。 3. ヒドリンダセンの2つの5員環にsyn/anti面選択的に置換基を導入することは困難であるが、環状ケトアミドでの容易なエピマー化能を利用し、基質のsyn/anti立体化学に拘わらず、syn体を経由してアミド基間の水素結合によって大環状構造へと自己組織化三量化する基質の設計と開発を行った。
• 多年相互作用反応場開発を指向した新規環状構造の構築と機能

  日本学術振興会：科学研究費助成事業

  研究期間 : 1998年 -1998年 

  代表者 : 辻 孝, 大北 雅一, 今井 敏郎, 鈴木 孝紀

   

  適切な官能基の導入によって、x,y,z座標軸方向での相互作用の制御が可能なヘキサヒドロインダセン(ヒドリンダセン)骨格を主要構成単位とする大環状構造の構築と、その多点相互作用による基質特異的ゲスト分子の取り込み、さらに、立体選択的反応場としての機能開発を目指した研究をおこなった。 1.電子供与性基を置換したヒドリンダセン骨格と、環内部への水素結合受容体の取り込みを目指した水素結合供与(アミド)基から成るマクロサイクルの設計と合成をおこなった。π-π stackingの効果と水素結合によってジニトロベンゼン、ジシアノベンゼン等との基質特異的ホスト-ゲスト錯体形成を狙ったものである。錯体形成は吸収スペクトルの変化によって検知できると考えており、上記の化合物に対する特異的センサーとして、また、反応場としての機能をさらに明かにしてゆく予定である。 2.ヒドリンダセン骨格とジエチニルベンゼンを交互に繋ぎ、大きな空孔をもつ環状構造の構築を進めた。ベンゼン環上の置換基は配座間の相互変換によってその位置関係が大きく変化し、置換基との相互作用による基質の取り込みと排出に際して機能すると考えられる。これらの結果に基いてさらに、ヒドリンダセンのベンゼン環上への水素結合能や金属配位能を有する置換基の導入とそれらの基を利用したチャンネル構造の形成、官能基化された開閉機能を備えた側鎖の導入による篭形構造の構築と多点相互作用によって基質を構造特異的に活性化する反応場の形成に検討を加える予定である。
• インダセン骨格によって構成された包接、自己集合能を有する基質の設計・開発研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 1997年 -1997年 

  代表者 : 辻 孝, 大北 雅一, 今井 敏郎, 鈴木 孝紀

   

  ベンゼン環の両側に飽和5員環が縮環したヘキサヒドロインダセン骨格は、両末端の5員環上の置換基が環骨格にたいして直交した方向の、一方、ベンゼン環上の置換基は5員環上の置換基に対して垂直方向の配向をとることを特徴とする。5員環およびベンゼン環に水素結合能や金属配位能を有する置換基を導入したインダセン誘導体と、その骨格を複数個環状に結合したマクロサイクルの設計と合成に検討を加えた。 1.官能基化したヘキサヒドロインダセン誘導体の合成に関する報告は少ない。そこで、ベンゼン環上に官能基変換が可能なメトキシ基、また、5員環にカルボニル、カルボキシル基等を導入した誘導体の合成法の開発を行い、それらの誘導体合成への道を開いた。 2.ヘキサヒドロインダセン骨格を5員環末端位で二量化し、二重結合の導入、シクロプロパン化によってシクロプロパン環を介したスピロ結合によってインダセン骨格を結び付けた構造を合成した。2つのインダセン骨格が互いに約120℃の角度をなして折れ曲がった構造をしており、今後のマクロサイクル合成の基本となるものである。 3.ベンゼン環に縮環した飽和5員環の比較的大きな自由度や、環状ケトエステルでの容易なエピマ-化能を利用した分子識別能や自己組織化能をもつヘキサヒドロインダセン誘導体を本研究過程で新たに着想し、その合成研究を進めた。X線構造解析の結果、飽和5員環の両末端位置の置換基がインダセン骨格に対してほぼ垂直の配座を優先することが明らかとなったが、この特徴を今後の分子間会合研究に取り入れ、生かすことを計画している。
• 〔1.1〕パラシクロファンの動力学的安定化とその化学特性研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 1996年 -1997年 

  代表者 : 辻 孝, 大北 雅一, 今井 敏郎, 鈴木 孝紀

   

  1.速度論的に安定化された[1.1]パラシクロファンの単離とX線構造解析。 我々が1993年にその合成を初めて報告した[1.1]パラシクロファンとその若干の置換体は、いずれも溶液中-20°C以下でのみ安定に存在し得る化合物であった。本研究において、そのベンゼン環上に-CH_2Si(CH_3)_3,-CON(CH_3)_2基を導入することによって著しく安定化されることを見い出し、単結晶として単離することに成功した。そのX線構造解析は、既存化合物中では最高度に変形したベンゼン環の存在を明らかにした。また、著しい変形にもかかわらず、理論計算から予測されたようにベンゼン環に検知し得るほどの結合交替はなく、良好な芳香族性の維持が示唆された。 2.速度論的に安定化された新規[1.1]パラシクロファンおよび[1.1]ナフタレノファンの合成研究。[4]パラシクロファン系における研究成果に基き、新たにメチレン側鎖上にアルキリデンを導入した[1.1]パラシクロファン誘導体、および、ベンゾ縮環を導入して共役系の拡張と速度論的安定化を兼ね備えた[1.1]ナフタレノファン誘導体の合成を進めた。これらの化合物では、[1.1]パラシクロファンの2つのベンゼン環上に電子的性質を異にする置換基の導入が可能であり、[1.1]パラシクロファンの特徴である強制された渡環相互作用による特性の発現が期待される。 3.[1.1]パラシクロファンの酸化還元挙動の解析。 理論計算は、[1.1]パラシクロファンのジカチオン種では2つのベンゼン環の面間隔の著しい減少と2つのベンゼン環に渡る電子の非局在化による新規な芳香族性の発現を示唆した。しかし、Et,CON(CH_3)_2基を置換した誘導体についてのCV測定では、安定なカチオンラジカル、ジカチオン種の生成は見い出せなかった。速度論的安定化が不十分なためと考えられ、上記(2)の化合物の合成を待ってさらに検討を進める。
• 結晶状態での光誘起電子移動を利用した酸化還元型ホトクロミズム系の構築

  文部科学省：科学研究費補助金(基盤研究(C))

  研究期間 : 1996年 -1997年 

  代表者 : 鈴木 孝紀

   

  本研究は、電子供与体と受容体の二成分からなる電荷移動錯体をモチーフとして、酸化還元型の新しいホトクロミズム系を提案しそれを実現することを目的としている。このような系を実現する為には、一方の成分が動的酸化還元挙動を示すもの、即ち、電子移動に際して可逆な結合生成と切断が起こるものを利用することが必要となる。これにより光照射時にのみ相互変換が起こり暗所では中性状態およびイオン状態の双方が安定に存在するという二重安定性が達成されると予想される。平成8年度にはヘキサアリールエタン型の構造を有する新規電子供与体である9,9,10,10-テトラアリールジヒドロフェナントレン1とその2電子酸化により生成するビス(トリアリールメタン)型ジカチオン色素1についての検討を行ない、平成9年度は電子受容性部分を有するビフェニル型色素を設計し、その還元によってC-C結合形成が起こる系を中心に検討を行なった。後者での中心的研究対象である2,2′-bis[dicyano-1-(4-dimethylaminophenyl)]-biphenyl3は,可視部にジシアノビニルアニリン骨格に由来する吸収極大を示す。そのサイクリックボルタモグラムは、2電子移動によってジヒドロフェナントレン型に閉還していること、また無色のジアニオンは酸化により3を再生することを示唆した。SmI_2によって発生させたジアニオンを酸でクエンチすると、立体特異的にトランス型に閉環した化合物4が高収率で単離された。このものは短時間の加熱によりエナミノニトリル型化合物5へと異性化し、そのものの酸化ではもはや3は生成しなかった。以上の結果は、この系が「書き込み禁止」オプションのついたエレクトロクロミズム応答系となることを示す結果である。本研究で扱った分子群は嵩高い置換基を有するためか、結晶性電荷移動錯体を与えにくく、固体状態での光誘起電子移動反応の検討には至らなかった。
• 新規安定ラジカルの両性多段階酸化還元挙動と単一成分有機電導体への展開

  文部科学省：科学研究費補助金(重点領域研究)

  研究期間 : 1995年 -1995年 

  代表者 : 鈴木 孝紀

   

  現在までに良好な電導性を示す数多くの分子性結晶が知らるようになったが、有機超伝導体を含めてそのほとんど全てが二成分以上から形成されている。これは、有機固体での電導性の担い手となる伝導電子を供給するという不可欠な要因によるものであるが、このこと自体が系の複雑さを増大させ、固体物性を司る結晶構造の制御をより困難にしている事も事実である。このような観点からすると単一成分有機電導体の研究はこの分野の新しい展開方向を指し示すものの一つと考えられる。そこで本課題では電気化学的両性度の高い新規な安定ラジカルを合成、単離しその単一成分有機電導体としての有効性を検討する事を目的として研究を行うことにした。実際の研究では四環性窒素複素環化合物であるキノキサロ[2,3-b]キノキサリン骨格(1)をモチーフとして選んだ。これは、ピラジンに代表される窒素複素環が代表的なW eitz型の酸化還元系を為すため電気化学的両性を付与しやすいこと、また極く限られた系ではあるものの中性ラジカルが安定に単離されている例があることを考慮した分子設計による。母体の1aとメチルトリフレートとの反応で5位が4級化されたカチオン種2aとした。このものの電子受容性は非常に高く、塩化メチレン中で還元電位の測定では+0.66及び-0.20Vに可逆な波形を示した。このことは2aの一電子還元で生成するラジカル種3aが0.86Vという小さなEsum値を持つ電気化学的両性の強い分子であることを予想させる。しかし、ヨウ化物イオンを用いた2aの還元では電子スペクトルで748nmの吸収を有する新しい化学種が観測されたものの半減期が10秒程と不安定な為その単離には至らなかった。そこで1aの1,4,7,10位の4箇所に様々な置換基を導入した化合物から出発しラジカル種3を安定に単離した。これらは10^<-7>から10^<-9>Scm^<-1>程度の電導性を示すことが明らかとなった。これらの値は決して高いものではないが、本研究の分子設計の妥当性を示すものである。
• 高反応性ビラジカル及びカチオンラジカルに関する研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 1994年 -1995年 

  代表者 : 宮仕 勉, MARIANO P.S., MCBRIDE J.M., HILINSKI E.F, DINNOCENZO J, GOODMAN J.L., WAGNER P.J., BERSON J.A., 秋山 公男, 鈴木 孝紀, 高橋 康丈, 池田 浩

   

  本研究は次の2つに大別される。 1.有機光化学におけるビラジカル(BR)とカチオンラジカル(CR)の研究 本研究では光誘起電子移動よる有機化合物の骨格転位におけるBRとCRの相互関係について研究した. 一般に電子受容対(A)との光誘起電子移動で生じた電子供与体基質の非ディストニックCRは容易に結合生成あるいは結合開裂を起こし,より安定なディストニックCR中間体(I^<・+>)へと変化する.溶媒のかご外へ拡散したI^<・+>はしばしばスペクトル的手法により観測され,また分子状酸素やアルコールなどのラジカルトラップ剤により捕捉されるが、イオンペア[I^<・+>/A^<・->]内におけるI^<・+>の反応性はまだ明らかになっていない.この中間体I^<・+>の反応性には二つの可能性がある. ひとつはA^<・->からの逆電子移動反応であり,結果として一重項および三重項BRが生じ,結合開裂あるいは結合生成をへて生成物を最終的に与える.もう一つ考えられる過程は結合開裂あるいは結合生成とそれに引き続く逆電子移動過程である.これらのどちらが反応に関与しているかを明らかにするために,相補的な二つのレーザー技術を用いた.すなわち,CRやBRの直接観測のための時間分解レーザーフラッシュフォトリシス(LFP)と,イオンペア[I^<・+>/A^<・->]のエネルギー評価のための時間分解光音響熱測定法である.ナノ秒時間分解LFPは現有設備で行ったが,ピコ秒時間分解LFP及び光音響熱測定法は,高橋と池田がフロリダ大学とロチェスター大学に共に赴き,共同研究として行った.また秋山はミシガン大学に赴きWagner教授とBRの多重度・電子構造と反応性の研究を行い,CRとの対比を行った.これらの研究の結果,CRとBRを経由する次の三つの光誘起電子移動反応系を見いだした. (1)2,5-ジアリール-1,5-ヘキサジエンの光増感電子移動縮退Cope転位.これは1,4-ジアリールシクロヘキサ-1,4-ジイルCRと1,4-ジアリールシクロヘキサ-1,4-ジイルBRを経由する「CR環化-BR開裂機構」で進行する. (2)2,2-ジアリールメチレンシクロプロパンの光増感電子移動縮退メチレンシクロプロパン転位.これはトリメチレンメタンCR(TMM^<・+>)と対応するBR(TMM)を経由する「CR開裂-BR閉環機構」で進行する. (3)5,5-ジメチル2,3-ビス(1-フェニルビニル)シクロペンタジエンの光誘起電子移動反応による一重項および三重項テトラメチレンエタン型BRの生成.この反応には逆電子移動過程が必要不可欠である. 招聘研究ではMariano教授,Hilinski助教授を招聘し,各々共同研究を行なった. Mariano教授との研究では有機合成上価値の高い反応中間体を直接観測し,反応機構を決定出来たことは意義深い.また,Hilinski助教授との共同研究では,オキサトリメチレンメタン型中間体の直接観測が緊急課題として挙げられ,三重大学工学部富岡秀雄教授の協力を得て低温マトリックスの実験を行った.さらにHilinski助教授との合同討議・情報交換では高反応性BR及びCRの動力学の研究にはピコ秒及びフェムト秒LFPの利用の必要性が改めて指摘された.これらの最先端設備による研究は今後の課題である. 以上の研究により,イオンペア内における逆電移動過程がCRの化学とBRの化学を結ぶ重要な役割を果たしていることが明らかになった.今日まで逆電子移動過程はエネルギーを浪費する「負の過程」として認識されてきていることから,この結論は注目に値する. 2.電荷移動錯体などの固相における光化学の研究 鈴木とエール大学McBride教授の派遣及び招聘により,固相光化学に対する結晶工学的見地からの討議と共同研究を行った.特に日本側の固相不斉光化学の研究はその反応機構はもちろんその合成的応用まで討議が及び,試料供与と測定実験を中心に共同研究を継続していくことが確認された. 本研究では今後も各研究者との共同研究を継続すると共に,アメリカNSF光誘起電子移動センター(ロチェスター大学内)との連携も図り、本研究課題を発展的に拡大する予定である.
• 酸化還元をトリガーとする応答性分子の研究

  文部科学省：科学研究費補助金(一般研究(C))

  研究期間 : 1994年 -1995年 

  代表者 : 鈴木 孝紀

   

  これまで電導性や磁性等の個体物性の発現を目指した多段階酸化還元系の設計に於いては、結晶中での電子の授受を容易にする為に、それに伴う構造変化が微少であることが望ましいとされてきた。このような観点からするとこれらは静的な酸化還元系と見なすことができる。一方、電子授受に伴い分子構造が大きく変化し、更には結合様式が変わってしまう場合でも、全過程としてそれが可逆に繰り返される場合には動的なレドックスサイクルとして区分することができ、これらは応答性分子としての機能が期待される。本研究はこのような動的過程を示す系の設計合成を通じて、それぞれの酸化段階の構造や性質を調べ、更にその変化をたどることにより、これらの応答性分子としての有効性を追求することを目的としている。平成6年度には酸化によって渡環結合が形成されるタイプの電子供与体をモチーフとして研究をおこない、平成7年度は逆に酸化により結合解裂を伴う分子の研究に重点を置いた。初めに研究対象とした2,2′-(シクロアルカン-1,m-ジイリデン)ビス(1,3-ベンゾジチオール)類は、電子供与体として良く知られたジベンゾ-TTF骨格にシクロアルカンを挿入して共役を切断したタイプの化合物であり、続いて研究したトリシクロ型化合物はシクロブタン環に二つの1,3-ベンゾジチオール環がスピロ型に連結された構造を有しているもので互い異性体の関係にある。両者とも容易に2電子酸化されビシクロ骨格を有するジカチオンへと変化する。これらの詳細な検討によりこれらが可逆なレドックス対になる為に適したリングサイズを特定し、その挙動の違いについて考察した。一方、1,3-ベンゾチオリウム自体は強力な発色団とはなり得ない為、次に酸化によりトリアリールメタン系の色素骨格を形成し得るヘキサアリールエタン誘導体の研究に着手した。期待通り単離されたジカチオンは可視部に十万以上のモル吸光係数を持つ安定な化合物で、二電子移動に際して定量的にC-C結合の形成と切断が起るエレクトロミズム系となることが実証された。
• 新規安定ラジカルの両性多段階酸化還元挙動と単一成分有機電導体への展開

  文部科学省：科学研究費補助金(重点領域研究)

  研究期間 : 1994年 -1994年 

  代表者 : 鈴木 孝紀

   

  本研究では電気化学的両性度の高い新規な安定ラジカルを合成単離し、その単一成分有機電導体としての有効性を検討する事を目的としている。実際の分子設計に於いては、電子供与性(D)及び受容性(A)双方の部分構造を一分子内に含むA-π-D^・型の中性ラジカルを設計した。平成6年度にはD^・骨格となるピリジル基のN上に、長さの異なるアルキル鎖を有するR-1の研究を行なった。得られたラジカルは高い電気化学的両性度を有し、またRの長さによってその酸化還元挙動は変化しない。しかし、その電導性はRの長さにより系統的に変化することが見いだされた。メチルおよびペンチル体のX線構造解析によれば、これらのラジカルはいずれもA^<-・>-π-D^+型の分極構造を有していることが示され、また結晶中に於ける分子の重なりも非常に良く似ている。しかし、Rが長くなるにつれて結晶構造の二次元性が顕著に低下し、これが電導性の変化につながっていることが明らかとなった。
• 光誘起電子移動反応による鎖状ポリエン及び慣理化合物の電子移動反応の研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 1992年 -1993年 

  代表者 : 宮仕 勉, 鈴木 孝紀, 池田 浩, 高橋 康丈

   

  光増感電子移動コープ転伝反応についてはエネルギー曲面の問題を追求した。2,5-ジアリール-1,5-ヘキサジエンラジカルカチオンの環化反応の活性化エネルギーをパルスラジオリシスで、中間体シクロヘキサン-1,4-ラジカルカチオンのイオン対のエネルギーを光音響測熱法で測定を行い、その結果から光増感電子移動反応によるコープ転伝反応はラジカルカチオン環化-ジラジカル開環型の2段階反応で起こる事を実証した。この反応に関連する1,4-ジアリール-2,3-ジメチルビシクロヘキサン誘導体の電子移動経由の開環反応を詳細に研究し、増成剤・溶媒極性に依存して反応機構が変化する事実とその反応機構を明らかにした。ジメチレンフランおよびジメチレンピロール誘導体をビススチリンフランおよびピロールの光増成移動反応で生成させ,その存在をレーザーフラシュ法で確認するとともに種々のジェンとの反応速度をレーザーフラッシュ法で求めた。化学的挿捉実験の結果を総合してこれらの非ケキュレ型中間体は茎底状態一重埴と決定した。理論計算結果からもその妥当性が裏付けられた。コープ転伝反応を起こした2,5-ジアリール-1,5-ヘキサジェン等に炭素を増加したヘプロジェン,オクロジェン,ノナジェンの素の光増感電子移動反応も行い,炭素鎖の長さの効果が詳細に研究され,興味ある立体化学で環化する事が判明し,長さの増大で環化効率が著しく減少する事を明らかにした。3種のジビニルベンゼンと強力な電子受容体ビスチアジアゾロテトラシアノキノジメタンとの結晶性電荷移動錯体の固相光化学を行い,電子移動経由の興味ある〔2+2〕型環化付加反応を見出した。
• 芳香環及び複素環の縮合を利用した新規な電子受容体の開発

  日本学術振興会：科学研究費助成事業

  研究期間 : 1988年 -1988年 

  代表者 : 鈴木 孝紀
• 機能性多段階酸化還元系の開発とその応答機能
• Molecular Response System Based on Dynamic Redox Properties

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