Apr. 2023, 北海道大学, ディスティングイッシュトリサーチャー　　　　　　　　　　　　　　　

Apr. 2022, 文部科学省, 令和4年度科学技術分野の文部科学大臣表彰「若手科学者賞」　　　　　　　　　　　　　　　
究極的共有結合の探求と機能創出に関する研究
石垣侑祐

Dec. 2021, 日本化学会, 第71回進歩賞　　　　　　　　　　　　　　　
高歪π電子系化合物の構造制御と機能創出
石垣侑祐

Dec. 2021, 有機合成化学協会, 第40回有機合成化学奨励賞　　　　　　　　　　　　　　　
レドックス化学による高歪有機分子の構築と機能開拓
石垣侑祐

Feb. 2021, 有機合成化学協会, DIC研究企画賞　　　　　　　　　　　　　　　
石垣 侑祐

Oct. 2020, 第6回北海道大学部局横断シンポジウム, ベストプレゼンテーション賞　　　　　　　　　　　　　　　
石垣 侑祐

Mar. 2020, The Chemical Society of Japan, Special Lecturer for Young Chemists in the 100th CSJ Annual Meeting　　　　　　　　　　　　　　　
Yusuke ISHIGAKI

Jan. 2020, 日本化学会北海道支部, 第17回日本化学会北海道支部奨励賞　　　　　　　　　　　　　　　
Yusuke ISHIGAKI

Nov. 2008, 日本化学会北海道支部, 2008年夏季研究発表会 優秀講演賞　　　　　　　　　　　　　　　
石垣 侑祐

Direct evidence for a carbon–carbon one-electron σ-bond
Takuya Shimajiri, Soki Kawaguchi, Takanori Suzuki, Yusuke Ishigaki
Nature, Springer Science and Business Media LLC, 25 Sep. 2024, [Peer-reviewed], [Last author, Corresponding author]
Scientific journal

Structural‐Change‐Induced Two‐Stage Redox Behavior of Pentacenebisquinodimethane with Tricolor Chromism
Yusuke Ishigaki, Shin‐ichi Mizuno, Takashi Harimoto, Takuya Shimajiri, Takanori Suzuki
Chemistry – An Asian Journal, 16 Jul. 2024
Scientific journal

Cation‐Stacking Approach Enabling Interconversion between Bis(xanthylium) and its Reduced Species
Moto Kikuchi, Tomoki Tadokoro, Takuya Tachibana, Shuichi Suzuki, Takanori Suzuki, Yusuke Ishigaki
Chemistry – A European Journal, 04 Jul. 2024
Scientific journal

Thermal Equilibrium Between Quinoid/Biradical Forms Enhancing Electrochemical Amphotericity
Yusuke Ishigaki, Shin‐ichi Mizuno, Kazuma Sugawara, Takumi Hashimoto, Shuichi Suzuki, Takanori Suzuki
Chemistry – A European Journal, 20 Jun. 2024
Scientific journal

Optical Property Control by the Interligand Charge Transfer Excited State in Brominated Homoleptic and Heteroleptic Aluminum Dinuclear Triple-Stranded Helicates
Yuto Konishi, Takumi Ehara, Luxia Cui, Kodai Ueno, Yusuke Ishigaki, Takunori Harada, Takeru Konta, Ken Onda, Yu Hoshino, Kiyoshi Miyata, Toshikazu Ono
Inorganic Chemistry, 63, 25, 11716, 11725, American Chemical Society (ACS), 11 Jun. 2024
Scientific journal

Synthesis and chiroptical properties of cyclic anthraquinodimethane dimer using Au-templated method
Soichiro Sugiyama, Kazuharu Murotani, Fumitaka Ishiwari, Akinori Saeki, Hidetoshi Kawai, Takanori Suzuki, Yoshitaka Tsuchido, Yusuke Ishigaki
Chemistry Letters, 01 Jun. 2024
Scientific journal

Crystallographic and spectroscopic studies on persistent triarylpropargyl cations
Takuya Shimajiri, Taiga Tsue, Shumpei Koakutsu, Yusuke Ishigaki, Takanori Suzuki
Chemical Communications, 2024
Scientific journal

Domino‐Redox Reaction Induced by An Electrochemically Triggered Conformational Change
Takashi Harimoto, Tomoki Tadokoro, Soichiro Sugiyama, Takanori Suzuki, Yusuke Ishigaki
Angewandte Chemie International Edition, 63, 1, e202316753, Wiley, Jan. 2024, [Peer-reviewed], [Last author, Corresponding author]
Scientific journal, 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.

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, 145, 50, 27838, 27849, 20 Dec. 2023, [Peer-reviewed]
Scientific journal, Hydrogen sulfide (H2S) has shown promise for gas therapy. However, it is still controversial whether H2S can remodel the tumor microenvironment (TME) and induce robust antitumor immunity. Here, a tumor-targeting and TME-responsive “smart” lipid nanoparticle (1-JK-PS-FA) is presented, which is capable of delivering and releasing H2S specifically in tumor tissues for on-demand H2S gas and photodynamic immunotherapy. 1-JK-PS-FA enables a burst release of H2S in the acidic TME, which promptly reduces the embedded organic electrochromic materials and consequently switches on near-infrared fluorescence and photodynamic activity. Furthermore, we found that high levels of H2S can reprogram the TME by reducing tumor interstitial fluid pressure, promoting angiogenesis, increasing vascular permeability, ameliorating hypoxia, and reducing immunosuppressive conditions. This leads to increased tumor uptake of 1-JK-PS-FA, thereby enhancing PDT efficacy and eliciting strong immunogenic cell death during 808 nm laser irradiation. Therefore, 1-JK-PS-FA permits synergistic H2S gas and photodynamic immunotherapy, effectively eradicating orthotopic breast tumors and preventing tumor metastasis and recurrence. This work showcases the capacity of H2S to reprogram the TME to enhance H2S gas and immunotherapy.

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, 17, 23, 24355, 24362, American Chemical Society (ACS), 04 Dec. 2023, [Peer-reviewed]
Scientific journal

Influence of structural isomers of naphthalene diimides on photophysical and electrochemical properties
Yusei Yamamoto, Ami Horioka, Luxia Cui, Yusuke Ishigaki, Yu Hoshino, Toshikazu Ono
Chemistry Letters, 53, 2, upad022, Oxford University Press (OUP), 01 Dec. 2023, [Peer-reviewed]
Scientific journal, Abstract

Three structural isomers of naphthalene diimides were synthesized. In all compounds, the electron-withdrawing diimide group exhibits a stable two-step reduction behavior under electrochemical conditions, and it was revealed that their reduction potentials vary significantly depending on the position of the diimide group relative to the naphthalene ring.

Carbon-based Biradicals: Structural and Magnetic Switching
Yusuke Ishigaki, Takashi Harimoto, Takuya Shimajiri, Takanori Suzuki
Chemical Reviews, 123, 24, 13952, 13965, American Chemical Society (ACS), 10 Nov. 2023, [Peer-reviewed], [Invited], [Lead author, Corresponding author]
Scientific journal

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, 29, e202301476, WILEY-V C H VERLAG GMBH, Jul. 2023, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal, 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, CHEMICAL SOC JAPAN, Jul. 2023, [Peer-reviewed], [Corresponding author]
English, Scientific journal, 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, 29, e202301759, WILEY-V C H VERLAG GMBH, Jul. 2023, [Peer-reviewed], [Last author, Corresponding author]
English, Scientific journal, 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, GEORG THIEME VERLAG KG, 12 Apr. 2023, [Peer-reviewed], [Invited]
English, Scientific journal, 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

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, e202300110, Wiley, 23 Mar. 2023, [Peer-reviewed], [Lead author, Corresponding author]
Scientific journal

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, e202203899, Wiley, 16 Mar. 2023, [Peer-reviewed], [Last author, Corresponding author]
Scientific journal

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, 01 Feb. 2023, [Peer-reviewed], [Last author, Corresponding author]
Scientific journal, 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, 12 Jan. 2023, [Peer-reviewed]
Scientific journal, 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.

Vis-NIR-Electrochromic Interconversion of Dithienylmethylium-Type Cyanine Dyes with a σ-Bonded Dimer or Isolable Neutral Radical
Su Gi Chong, Shuichi Suzuki, Takanori Suzuki, Yusuke Ishigaki
Bulletin of the Chemical Society of Japan, 96, 10, 1144, 1149, 2023, [Peer-reviewed], [Invited], [Last author, Corresponding author]
Scientific journal, 4-Methoxyphenyl-substituted di(2-thienyl)methyliums were designed and synthesized as a new class of cationic dyes exhibiting absorption in the visible (Vis) and near-infrared (NIR) region. Their cyanine-type π-conjugation was confirmed by alternation of positive charges along the polymethine chain as well as by a significant disappearance of bond alternation. Upon one-electron reduction of these cations, neutral radicals were generated, which could be isolated as stable entities when an anthryl-type substituent was attached to the central methine carbon while the secondary radical without any substituent quantitatively converted to a σ-bonded dimer. Since both the stable radical and the dimer regenerated the starting cyanine dyes upon oxidation, the present redox pairs can serve as electrochromic materials that exhibit a change in absorption in the Vis-NIR region.

Creation and functional control of near-infrared electrochromic molecules based on parachemical methane structures
Takashi Harimoto, Yusuke Ishigaki
Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry, 81, 10, 963, 977, 2023, [Peer-reviewed], [Invited], [Last author, Corresponding author]
Scientific journal, In recent years, near-infrared (NIR) dyes, exhibiting absorption in the NIR region (750-2500 nm), has been applied to various optical applications such as security marking, photovoltaic cells and chemotherapy of deep tissues in vivo. Electrochromic systems capable of switching NIR absorption are attractive from the viewpoint of applications for material and life science, and thus several examples have been reported to date. The development of organic-based materials is needed to reduce the environmental impact and improve biocompatibility. However, since the redox states of organic NIR dyes are generally unstable, the switching of NIR absorption based on quantitative during their redox interconversion. interconversion To construct is still a challenging organic electrochromic issue regarding systems reversibility capable and of durability ON／OFF switching of NIR-absorbing properties, we have focused on the non-aromatic π -conjugated para-quinodimethane (p-QD) skeleton. Herein, we have shown several studies on the synthesis and functional control of NIR electrochromic molecules based on redox-active p-QD scaffolds. We have elucidated the spectroscopic and electrochemical properties of various arylated quinodimethane derivatives and demonstrated that p-QD building blocks can be versatile components for the development of NIR switchable organic electrochromic systems.

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, Royal Society of Chemistry (RSC), 2023, [Peer-reviewed], [Invited], [Last author, Corresponding author]
Scientific journal, 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.

Ultralong C sp ³-C sp ³Single Bonds Shortened and Stabilized by London Dispersion
Takuya Shimajiri, Yuta Kawakami, Soki Kawaguchi, Yuki Hayashi, Kazuto Hada, Takanori Suzuki, Yusuke Ishigaki
Synlett, 2023, [Peer-reviewed], [Last author, Corresponding author]
Scientific journal, 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.

Strain‐sensitive On‐Surface Ladderization by Non‐Dehydrogenative Heterocyclization
Yujing Ma, Kazuma Sugawara, Yusuke Ishigaki, Kewei Sun, Takanori Suzuki, Shigeki Kawai
Chemistry – A European Journal, Wiley, 20 Dec. 2022, [Peer-reviewed]
Scientific journal

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 – A European Journal, Wiley, 15 Sep. 2022, [Peer-reviewed], [Lead author, Corresponding author], [International Magazine]
English, Scientific journal, 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, Wiley, 08 Aug. 2022, [Peer-reviewed]
English, Scientific journal, 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, Apr. 2022, [Peer-reviewed], [Lead author]
Scientific journal, 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, 21 Jan. 2022, [Peer-reviewed]
Scientific journal, 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.

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, 2022, [Lead author, Corresponding author]
Scientific journal, Two tetraarylanthraquinodimethane (Ar4AQD) 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 Ar4AQD 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).

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, Royal Society of Chemistry (RSC), 2022, [Peer-reviewed], [International Magazine]
English, Scientific journal, 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, [Peer-reviewed], [Lead author, Corresponding author]
Scientific journal, 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.

Redox-Active Hydrocarbons: Isolation and Structural Determination of Cationic States toward Advanced Response Systems
Takashi Harimoto, Yusuke Ishigaki
ChemPlusChem, 87, e202200013, 2022, [Peer-reviewed], [Invited], [Last author, Corresponding author]
Organic chemistry has developed rapidly as a carbon-based science. Particularly, hydrocarbons with aromatic rings have attracted much attention as molecular materials for use in organic electronics. In principle, aromatic species can be constructed if carbon and hydrogen atoms are available. Therefore, revealing the nature of pure hydrocarbons with an (anti)aromatic nature should pave the way for the development of as yet unexplored organic materials. In this Review, we focus on pure hydrocarbons composed of only carbon and hydrogen atoms, and present recent studies on their intrinsic electrochemical and spectroscopic properties and structural characterization of their cationic states. We also address more sophisticated hydrocarbon-based response systems that are capable of modulating their properties in response to external stimuli such as light, heat, and electric potential.

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, [Peer-reviewed], [Lead author]
Scientific journal, 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, Dec. 2021, [Peer-reviewed], [Lead author]
Scientific journal, 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.

A Hydrogen-Bonded Organic Framework Based on Pyrazinopyrazine
Qin Ji, Kiyonori Takahashi, Shin-ichiro Noro, Yusuke Ishigaki, Kenta Kokado, Takayoshi Nakamura, Ichiro Hisaki
Crystal Growth & Design, 21, 8, 4656, 4664, American Chemical Society (ACS), Jul. 2021, [Peer-reviewed], [International Magazine]
Scientific journal

Redox-active tetraaryldibenzoquinodimethanes
Yusuke Ishigaki, Kazuma Sugawara, Tomoki Tadokoro, Yuki Hayashi, Takashi Harimoto, Takanori Suzuki
Chemical Communications, 57, 59, 7201, 7214, Royal Society of Chemistry (RSC), Jul. 2021, [Peer-reviewed], [Invited], [Lead author, Corresponding author], [International Magazine]
English, Scientific journal,

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#
Yusuke Ishigaki, Kota Asai, Takuya Shimajiri, Takanori Suzuki
Chemistry Letters, 50, 6, 1184, 1187, Jun. 2021, [Peer-reviewed], [Lead author], [International Magazine]
Scientific journal, 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.

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, Wiley, 19 Apr. 2021
Scientific journal

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, Georg Thieme Verlag {KG}, Apr. 2021, [Peer-reviewed], [Invited], [Lead author], [International Magazine]
English, Scientific journal, 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.

Redox-active and highly strained hydrocarbons: Control of HOMO levels based on flexibility of covalent bonds
Yusuke Ishigaki
Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry, 79, 4, 290, 299, Apr. 2021, [Peer-reviewed], [Lead author, Corresponding author], [Domestic magazines]
Scientific journal, The carbon - carbon covalent bond is one of the most basic concept in organic chemistry. Bond length, bond angle, and torsion angle among carbon atoms are nearly constant on the basis of the bond order and hybrid orbitals. On the other hand, highly strained hydrocarbons such as sterically-congested and/or curved polycyclic aromatic hydrocarbons have attracted much attention with regard to their characteristic features. Regarding the C-C single bond, whose standard length is 1.54 A, several attempts have been made to elongate the C-C single bond to gain new insight into the chemical bond and understand what happens at the limits of a bond. In contrast to the standard C=C double bond with planarity, the overcrowded ethylenes (OCEs) with bulky substituents can adopt anti-folded, syn-folded and/ or twisted forms due to the steric hindrance around the central C=C double bond, and thus many OCEs exhibit photo- and thermochromic behavior upon exposure to external stimuli. Herein, we focus on redox-active hydrocarbons with two dibenzocycloheptatriene units, where unprecedented flexible C-C bonds based on extremely elongated C-C single bonds and control of HOMO levels were demonstrated. Thus, these highly strained hydrocarbons could be promising candidates for the development of functional materials.

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 - International Edition, 60, 17, 9427, 9432, Apr. 2021, [Peer-reviewed], [International Magazine]
Scientific journal, 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.

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, 10 Mar. 2021, [Peer-reviewed], [Lead author, Corresponding author], [International Magazine]
Scientific journal, 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
Yusuke Ishigaki, Kota Asai, Henri Pierre Jacquot de Rouville, Takuya Shimajiri, Valérie Heitz, Hiroshi Fujii-Shinomiya, Takanori Suzuki
European Journal of Organic Chemistry, 2021, 6, 990, 997, 12 Feb. 2021, [Peer-reviewed], [Lead author], ［Internationally co-authored］, [International Magazine]
Scientific journal, 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.

A hydrogen-bonded organic framework based on redox-active tri(dithiolylidene)cyclohexanetrione
Kilingaru I. Shivakumar, Shin Ichiro Noro, Yuna Yamaguchi, Yusuke Ishigaki, Akinori Saeki, Kiyonori Takahashi, Takayoshi Nakamura, Ichiro Hisaki
Chemical Communications, 57, 9, 1157, 1160, 28 Jan. 2021, [Peer-reviewed], [International Magazine]
Scientific journal, Redox-active hexakis(4-carboxyphenyl) tri(dithiolylidene)cyclohexanetrione (CPDC) was synthesized. The CPDC-based porous framework, constructedviaanomalistic helical hydrogen-bonding, exhibites permanent porosity and photoconductivity.

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, PERGAMON-ELSEVIER SCIENCE LTD, 2021
English, Scientific journal, 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.

Expandability of the covalent bond: A new facet discovered in extremely long Csp3-Csp3 single bonds
Yusuke Ishigaki, Yasuto Uchimura, Takuya Shimajiri, Takanori Suzuki
Bulletin of the Chemical Society of Japan, 94, 4, 1385, 1393, 2021, [Peer-reviewed], [Invited], [Lead author], [International Magazine]
Scientific journal, 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.

9,9'-bi(xanthene)-type hexaphenylethane derivatives as advanced organic electrochromic systems
Takanori Suzuki, Yusuke Ishigaki, Masaki Takata, Jun Ichi Nishida, Takanori Fukushima
Heterocycles, 102, 3, 419, 450, 2021, [Peer-reviewed], [International Magazine]
Scientific journal, 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.

Flexible C–C Bonds: Reversible Expansion, Contraction, Formation, and Scission of Extremely Elongated Single Bonds
Takuya Shimajiri, Takanori Suzuki, Yusuke Ishigaki
Angewandte Chemie International Edition, 59, 49, 22252, 22257, Wiley, 24 Aug. 2020, [Peer-reviewed], [Last author, Corresponding author], [International Magazine]
English, Scientific journal, 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.

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, Wiley, 16 Apr. 2020
Scientific journal

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 International Edition, 59, 16, 6581, 6584, Wiley, 16 Apr. 2020, [Peer-reviewed], [Lead author, Corresponding author], [International Magazine]
English, Scientific journal, 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, Wiley, Apr. 2020, [Peer-reviewed], [Lead author, Corresponding author], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, 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.

A novel condensed heterocyclic quinone with a dibenzofuranobisthiadiazole skeleton
Kazuma Sugawara, Wataru Nojo, Yusuke Ishigaki, Junko Ohkanda, Takanori Suzuki
Heterocycles, 101, 1, 99, 103, 2020, [Peer-reviewed], [International Magazine]
Scientific journal, © 2020 The Japan Institute of Heterocyclic Chemistry – 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.

H2S-Activatable Near-infrared Afterglow Luminescent Probes for Sensitive Molecular Imaging in vivo
L. Wu, Y. Ishigaki, Y. Hu, K. Sugimoto, W. Zeng, T. Harimoto, Y. Sun, J. He, T. Suzuki, X. Jiang, H.-Y. Chen, D. Ye
Nature Communications, 11, 1, in press, Springer Science and Business Media LLC, 2020, [Peer-reviewed], [Lead author], ［Internationally co-authored］, [International Magazine]
Scientific journal, 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.

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, AMER CHEMICAL SOC, Nov. 2019, [Peer-reviewed], [Lead author, Corresponding author], [International Magazine]
English, Scientific journal, 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.

Two-Way Chromic Systems Based on Tetraarylanthraquinodimethanes: Electrochromism in Solution and Mechanofluorochromism in a Solid State
Yusuke Ishigaki, Kazuma Sugawara, Masaki Yoshida, Masako Kato, Takanori Suzuki
Bulletin of the Chemical Society of Japan, 92, 7, 1211, 1217, CHEMICAL SOC JAPAN, Jul. 2019, [Peer-reviewed], [Lead author, Corresponding author], [International Magazine]
English, Scientific journal, 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.

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
Nojo Wataru, Ishigaki Yusuke, Takeda Takashi, Akutagawa Tomoyuki, Suzuki Takanori
Chemistry A European Journal, 25, 32, 7759, 7765, WILEY-V C H VERLAG GMBH, 07 Jun. 2019, [Peer-reviewed], [International Magazine]
English, Scientific journal, 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.

Engineering of electrochromic materials as activatable probes for molecular imaging and photodynamic therapy.
Wu L, Sun Y, Sugimoto K, Luo Z, Ishigaki Y, Pu K, Suzuki T, Chen HY, Ye D
Journal of the American Chemical Society, 140, 47, 16340, 16352, AMER CHEMICAL SOC, Nov. 2018, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, 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
Yusuke Ishigaki, Tomohiro Iwai, Yuki Hayashi, Aiichiro Nagaki, Ryo Katoono, Kenshu Fujiwara, Jun-ichi Yoshida, Takanori Suzuki
Synlett, 29, 16, 2147, 2154, GEORG THIEME VERLAG KG, Oct. 2018, [Peer-reviewed], [Invited], [Lead author], [International Magazine]
English, Scientific journal, 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.

Expandability of a long C-O bond by a scissor effect in acenaphthofuran.
Uchimura Y, Shimajiri T, Ishigaki Y, Katoono R, Suzuki T
Chemical communications (Cambridge, England), 54, 73, 10300, 10303, ROYAL SOC CHEMISTRY, Sep. 2018, [Peer-reviewed], [International Magazine]
English, Scientific journal, 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.

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, Aug. 2018, [Peer-reviewed], [International Magazine]
Scientific journal, © 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.

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, Elsevier Ltd, 09 May 2018, [Peer-reviewed], [International Magazine]
English, Scientific journal, 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.

Narrower HOMO-LUMO gap attained by conformational switching through peripheral polyarylation in 1,4,5,8-tetraaza-9,10-anthraquinodimethanes
Takanori Suzuki, Yusuke Ishigaki, Kazuma Sugawara, Yu Umezawa, Ryo Katoono, Atsushi Shimoyama, Yoshiyuki Manabe, Koichi Fukase, Takanori Fukushima
Tetrahedron, 74, 18, 2239, 2244, Elsevier Ltd, 03 May 2018, [Peer-reviewed], [International Magazine]
English, Scientific journal, 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 DFT 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.

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, Elsevier Inc, 12 Apr. 2018, [Peer-reviewed], [Lead author, Corresponding author], [International Magazine]
English, Scientific journal, 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, Elsevier Ltd, 04 Apr. 2018, [Peer-reviewed], [International Magazine]
English, Scientific journal, 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.

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, 1900, MDPI AG, Nov. 2017, [Peer-reviewed], [Lead author, Corresponding author], [International Magazine]
English, Scientific journal, 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.

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, WILEY-V C H VERLAG GMBH, Jul. 2017, [Peer-reviewed], [International Magazine]
English, Scientific journal, 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.

STEREOSELECTIVE ENCAPSULATION FOR A TRIARYLMETHYLIUM o,o-DIMER BY NATURAL gamma-CYCLODEXTRIN: ORIGIN OF CHIRAL RECOGNITION FOR THE AXIALLY CHIRAL DICATIONIC GUEST
Takanori Suzuki, Jose P. Ceron-Carrasco, Hitomi Tamaoki, Yusuke Ishigaki, Ryo Katoono, Takanori Fukushima, Horacio Perez-Sanchez
HETEROCYCLES, 94, 6, 1123, 1132, PERGAMON-ELSEVIER SCIENCE LTD, Jun. 2017, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, 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.

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, CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS, Mar. 2017, [Peer-reviewed], [Invited], [International Magazine]
English, Scientific journal, 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.

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
Takanori Suzuki, Takuma Kuroda, Hitomi Tamaoki, Sho Higasa, Tatsuo Nehira, Ryo Katoono, Yusuke Ishigaki, Kenshu Fujiwara, Takanori Fukushima, Hidetoshi Yamada
HETEROCYCLES, 95, 2, 816, 829, PERGAMON-ELSEVIER SCIENCE LTD, Jan. 2017, [Peer-reviewed], [International Magazine]
English, Scientific journal, 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.

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, CHEMICAL SOC JAPAN, Jul. 2016, [Peer-reviewed], [International Magazine]
English, Scientific journal, 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.

Redox-Mediated Reversible σ-Bond Formation/Cleavage
Takanori Suzuki, Hitomi Tamaoki, Jun-Ichi Nishida, Hiroki Higuchi, Tomohiro Iwai, Yusuke Ishigaki, Keisuke Hanada, Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Fukushima
Organic Redox Systems: Synthesis, Properties, and Applications, 13, 37, Wiley Blackwell, 21 Dec. 2015
English, In book, The redox-induced change in the bond order occurs not only in the π-conjugated systems but in the system where the σ-bond formation/cleavage is accompanied by electron transfer. Due to the dynamic geometrical changes upon redox reactions, the chromism based on the dyrex systems could be accompanied by more advanced features. Irrespective of the "π/ σ"- or "exo/endo"-type classification, the characteristic features of a dyrex system are facile 2e-transfer nearly at the same potentials and the electrochemical bistability, which are in sharp contrast to those of a conventional redox system. When the two dyrex units are connected with a proper spacer, the resulting dyad would exhibit a unique redox scheme, which is far different from the dyads consisting of conventional redox units. Since the dyrex unit could be potentially used as a "unimolecular molecular memory", the molecule with multiple dyrex units would be developed toward "molecular n-bit memory".

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, PERGAMON-ELSEVIER SCIENCE LTD, Jan. 2015, [Peer-reviewed], [Lead author], [International Magazine]
English, Scientific journal, 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, PERGAMON-ELSEVIER SCIENCE LTD, Jan. 2015, [Peer-reviewed], [Lead author], [International Magazine]
English, Scientific journal, 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.

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, CHEMICAL SOC JAPAN, Jul. 2014, [Peer-reviewed], [International Magazine]
English, Scientific journal, 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.

Acceptor-Donor-Acceptor Oligomers Containing Dithieno[3,2-b:2 ',3 '-d]pyrrole and Thieno[2,3-c]pyrrole-4,6-dione Units for Solution-Processed Organic Solar Cells
Lauren G. Mercier, Amaresh Mishra, Yusuke Ishigaki, Florian Henne, Gisela Schulz, Peter Baeuerle
ORGANIC LETTERS, 16, 10, 2642, 2645, AMER CHEMICAL SOC, May 2014, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
English, Scientific journal, New acceptor-donor-acceptor (A-D-A) oligomers (1 and 2) containing a central dithieno[3,2-b:2',3'-d]pyrrole unit and end-capping thieno[2,3-c]pyrrole-4,6-dione groups have been synthesized and characterized. Bulk heterojunction solar cells were prepared together with PC61BM and PC71BM, and the best results were obtained for the latter acceptor using 1,8-diiodooctane as an additive. Photovoltaic devices containing these oligomers achieved high external quantum efficiencies up to 50%.

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, CHEMICAL SOC JAPAN, Sep. 2013, [Peer-reviewed], [International Magazine]
English, Scientific journal, 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.

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, CHEMICAL SOC JAPAN, May 2012, [Peer-reviewed], [International Magazine]
English, Scientific journal, 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.

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, MDPI AG, Nov. 2011, [Peer-reviewed], [Lead author], [International Magazine]
English, Scientific journal, 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].

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, ROYAL SOC CHEMISTRY, 2010, [Peer-reviewed], [International Magazine]
English, Scientific journal, 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+)).

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, Wiley-Blackwell, Nov. 2009

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, CHEMICAL SOC JAPAN, Jul. 2009, [Peer-reviewed], [International Magazine]
English, Scientific journal, 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.

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, WILEY-V C H VERLAG GMBH, 2009, [Peer-reviewed], [International Magazine]
English, Scientific journal, 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.

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, 07 Sep. 2011
Japanese

世界最長の炭素－炭素結合をつくってわかった、共有結合の柔軟性　　　　　　　　　　　　　　　
石垣 侑祐
academist journal, Dec. 2020, [Single work]

高ひずみ化合物の特性を活かした機能開拓　　　　　　　　　　　　　　　
石垣 侑祐
化学と工業『飛翔する若手研究者』 （日本化学会）, Nov. 2020, [Single work]

分子の歪みが生成物を左右する　　　　　　　　　　　　　　　
石垣 侑祐, 注目の論文
化学 2018年 11 月号（化学同人）, Oct. 2018, [Single work]

世界最長の炭素－炭素単結合を目指して　　　　　　　　　　　　　　　
石垣 侑祐
現代化学 2018年 08 月号（東京化学同人）, Jul. 2018, [Single work]

Dibenzotropylium End-Capped Longest Oligo(9,10-anthrylene)s: Isolation and Exploration of Huge Hydrocarbonic Dications　　　　　　　　　　　　　　　
Yusuke Ishigaki
The 20th International Symposium on Novel Aromatic Compounds, 13 Aug. 2024

有機カチオン化学の開拓　　　　　　　　　　　　　　　
石垣侑祐
第16回未来材料セミナー, 28 Feb. 2024
[Invited]

〔Major achievements〕有機カチオン化学の開拓と機能探究　　　　　　　　　　　　　　　
石垣侑祐
若手研究者のための有機化学札幌セミナー, 01 Nov. 2023
[Invited]

〔Major achievements〕歪んだπ電子系化合物の特異な構造と多彩な応答機能　　　　　　　　　　　　　　　
石垣侑祐
第15回有機π電子系シンポジウム, 16 Dec. 2022
[Invited]

〔Major achievements〕単結晶X線構造解析に基づく高歪有機分子の構造決定と研究展開　　　　　　　　　　　　　　　
石垣侑祐
令和4年（2022年）度日本結晶学会若手の会, 25 Nov. 2022
[Invited]

π-Electronic Molecules with Distorted C-C Covalent Bonds: Reversible Switching of Structure and Physical Properties　　　　　　　　　　　　　　　
Yusuke Ishigaki
International Congress on Pure & Applied Chemistry Kota Kinabalu, 22 Nov. 2022
[Invited]

〔Major achievements〕レドックス化学による高歪有機分子の構築と機能開拓　　　　　　　　　　　　　　　
石垣侑祐
第38回有機合成化学セミナー, 29 Sep. 2022
[Invited]

Redox-Active Strained Molecules with Controllable Structure and Physical Properties　　　　　　　　　　　　　　　
Yusuke Ishigaki
Strasbourg-Japan USIAS symposium on Condensed Conjugation, 12 Sep. 2022
[Invited]

Strained π-Electronic Systems: Control of Structures and Physical Properties by External Stimuli　　　　　　　　　　　　　　　
Yusuke Ishigaki
UHMob International Conference - Organic Semiconductors: From Principles to Applications, 09 Sep. 2022
[Invited]

〔Major achievements〕Redox-active Quinodimethane Derivatives with Overcrowded C=C Bonds　　　　　　　　　　　　　　　
Yusuke Ishigaki
The 25th IUPAC International Conference on Physical Organic Chemistry, 11 Jul. 2022
[Invited]

〔Major achievements〕高歪π電子系化合物の構造制御と機能創出　　　　　　　　　　　　　　　
石垣侑祐
日本化学会第102春季年会, 23 Mar. 2022
23 Mar. 2022 - 26 Mar. 2022, [Invited]

〔Major achievements〕Construction of Stimuli-Responsive π-Electronic Systems with Highly Strained C–C Covalent Bonds　　　　　　　　　　　　　　　
Yusuke Ishigaki
The 3rd CSLT-CSJ Joint Symposium, 12 Mar. 2022
12 Mar. 2022 - 13 Mar. 2022, [Invited]

〔Major achievements〕Strained Hydrocarbons with Switchable Structural and Physical Properties Induced by Photo-, Thermo-, and Electrochemical Input　　　　　　　　　　　　　　　
Yusuke Ishigaki
The 71st JSCC Conference (Electrochemical control of excited states of photo-functional coordination and hybrid compounds -Electrofluorochromism and electrochemiluminescence-), 16 Sep. 2021
16 Sep. 2021 - 19 Sep. 2021, [Invited]

〔Major achievements〕光／熱／電気化学的刺激による分子構造制御と物性変調　　　　　　　　　　　　　　　
石垣侑祐
2021年電気化学秋季大会, 09 Sep. 2021
08 Sep. 2021 - 09 Sep. 2021, [Invited]

Dynamic control of [n] acene structures upon electron transfer: hysteretic three-state redox interconversion accompanied by a change in NIR absorptions　　　　　　　　　　　　　　　
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, 2021
2021 - 2021

Unique redox behavior of orthogonally twisted dications with multiple 14π-aromatic units　　　　　　　　　　　　　　　
林裕貴, 鈴木孝紀, 石垣侑祐
基礎有機化学討論会要旨集, 2021
2021 - 2021

NIR Mechanochromic Luminescence of Bis(triarylmethylium)-type Macrocyclic Dications　　　　　　　　　　　　　　　
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, 2021
2021 - 2021

Polyaryl-substituted Quinodimethane Derivatives with Unique Emission Properties Based on Multi-conformations in Pseudopolymorphs　　　　　　　　　　　　　　　
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, 2021
2021 - 2021

〔Major achievements〕Highly Strained Compounds: Switchable Redox Properties and Flexible C–C bonds　　　　　　　　　　　　　　　
ISHIGAKI Yusuke
Joint Symposium of School of Science & WPI-ICReDD in Hokkaido Univ., 10 Dec. 2020
[Invited]

〔Major achievements〕光による分子構造制御と新奇応答機能　　　　　　　　　　　　　　　
石垣侑祐
第7回"光"機到来！Qコロキウム, 16 Oct. 2020
[Invited]

新規テトラアザアントラキノジメタン誘導体の構築　　　　　　　　　　　　　　　
菅原一真, 石垣侑祐, 鈴木孝紀
日本化学会第100春季年会, Mar. 2020, Japanese, Oral presentation

ポリアリールテトラアザアントラキノジメタン誘導体の結晶多形と⽴体配置　　　　　　　　　　　　　　　
菅原一真, 石垣侑祐, 鈴木孝紀
日本化学会第100春季年会, Mar. 2020, Japanese, Oral presentation

[C-H…C+]架橋型カチオンの1,6-ヒドリドシフトに基づく異性化応答　　　　　　　　　　　　　　　
石垣侑祐, 林裕貴, 若森晋之介, 山田英俊, 鈴木孝紀
日本化学会第100春季年会, Mar. 2020, Japanese, Oral presentation

ビストリアリールメチリウム型⼤環状ジカチオンの構築と応答挙動　　　　　　　　　　　　　　　
石垣侑祐, 立花拓哉, 鈴木孝紀
日本化学会第100春季年会, Mar. 2020, Japanese, Oral presentation

テトラチエニルアントラキノジメタン誘導体の閉殻／開殻スイッチングに基づく応答挙動　　　　　　　　　　　　　　　
石垣侑祐, 橋本拓実, 菅原一真, 鈴木修一, 鈴木孝紀
日本化学会第100春季年会, Mar. 2020, Japanese, Oral presentation

〔Major achievements〕Highly strained hydrocarbons with a hyper covalent bond and/or switchable redox properties by photo- and thermal isomerization　　　　　　　　　　　　　　　
Yusuke ISHIGAKI
日本化学会第100春季年会「第34回若い世代の特別講演」, Mar. 2020, Japanese, Invited oral presentation
[Invited]

〔Major achievements〕Novel Response Systems Based on Unique Structures of Highly Strained Compounds　　　　　　　　　　　　　　　
Yusuke ISHIGAKI
日本化学会北海道支部「第17回北海道支部奨励賞」 受賞講演, 29 Jan. 2020, Japanese, Invited oral presentation
[Invited]

Reversible Expansion and Contraction of an Extremely Elongated Csp3–Csp3 Single Bond Based on Photo- and Thermal Isomerization of Highly Strained Hydrocarbons　　　　　　　　　　　　　　　
SHIMAJIRI Takuya, ISHIGAKI Yusuke, SUZUKI Takanori
The 20th RIES-HOKUDAI International Symposium, Dec. 2019, English, Poster presentation

Tetraarylanthraquinodimethane-type redox systems exhibiting different chromism in solution and in a solid state　　　　　　　　　　　　　　　
SUGAWARA Kazuma, ISHIGAKI Yusuke, SUZUKI Takanori
The 20th RIES-HOKUDAI International Symposium, Dec. 2019, English, Poster presentation

Reversible ON/OFF switching of oxidative properties by photo- and thermal interconversion between configurational isomers of strained hydrocarbons　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, HAYASHI Yuki, SUZUKI Takanori
The 20th RIES-HOKUDAI International Symposium, Dec. 2019, English, Poster presentation

Fine-tuning of Redox Properties of 1,3-Diene-type Electron Donors and Corresponding Dications with NIR Absorption　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, HARIMOTO Takashi, SUGIMOTO Keisuke, SUZUKI Takanori
The 20th RIES-HOKUDAI International Symposium, Dec. 2019, English, Poster presentation

新規高歪み炭化水素の光―熱異性化に基づく酸化特性の可逆的スイッチング【優秀ポスター発表賞】　　　　　　　　　　　　　　　
石垣侑祐, 林裕貴, 鈴木孝紀
第9回CSJ化学フェスタ2019, Oct. 2019, Japanese, Poster presentation

極度に長い結合を有する高歪化合物の分子内光環化反応を鍵とする多段階構造制御　　　　　　　　　　　　　　　
島尻拓哉, 石垣侑祐, 鈴木孝紀
第30回基礎有機化学討論会, Sep. 2019, Japanese, Poster presentation

共役ジエン型電子供与体と近赤外吸収を有するジカチオンとの酸化還元応答【ポスター賞】　　　　　　　　　　　　　　　
石垣侑祐, 張本尚, 杉本佳亮, 菅原一真, 鈴木孝紀
第30回基礎有機化学討論会, Sep. 2019, Japanese, Poster presentation

Hyper Covalent Bond with a Bond Length beyond 1.8 Å in a Highly Strained Aromatic Hydrocarbon　　　　　　　　　　　　　　　
SHIMAJIRI Takuya, ISHIGAKI Yusuke, SUZUKI Takanori
The 18th International Symposium on Novel Aromatic Compounds, Jul. 2019, English, Poster presentation

Molecular Switches with Controllable Oxidative Properties Triggered by Light and Heat　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, HAYASHI Yuki, SUZUKI Takanori
The 18th International Symposium on Novel Aromatic Compounds, Jul. 2019, English, Poster presentation

Tetraarylanthraquinodimethanes exhibiting electrochromism in solution and mechanofluorochromism in solid state　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, SUGAWARA Kazuma, SUZUKI Takanori
The 18th International Symposium on Novel Aromatic Compounds, Jul. 2019, English, Poster presentation

Two-way Chromic Systems Based on Tetraarylanthraquinodimethanes　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, SUGAWARA Kazuma, SUZUKI Takanori
CSE international student symposium 2019 （2nd Asian-French Workshop on Polymer Science）, Jul. 2019, English, Poster presentation

Controllable oxidative properties between syn/anti-folded isomers switched by photo- and thermal isomerization　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, HAYASHI Yuki, SUZUKI Takanori
The 10th CSE-ALP International Summer School, Jul. 2019, English, Poster presentation

分子内コア－シェル型高歪化合物：C–C 単結合の限界への挑戦【Best Poster賞】　　　　　　　　　　　　　　　
島尻拓哉, 石垣侑祐, 鈴木孝紀
第31回万有札幌シンポジウム, Jul. 2019, Japanese, Poster presentation

Reversible switching of oxidative properties of overcrowded ethylenes by photo- and thermal isomerization between syn/anti-folded isomers　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, HAYASHI Yuki, SUZUKI Takanori
14th International Symposium on Functional π-Electron Systems, Jun. 2019, English, Poster presentation

〔Major achievements〕Hyper covalent bond in highly strained hydrocarbon: an expandable C–C single bond with a bond length beyond 1.8 Å　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, SHIMAJIRI Takuya, SUZUKI Takanori
14th International Symposium on Functional π-Electron Systems, Jun. 2019, English, Oral presentation

〔Major achievements〕Unique response systems based on redox-active hydrocarbons with hyper covalent bond or strained double bond　　　　　　　　　　　　　　　
ISHIGAKI Yusuke
Asian International Symposium - Electrochemistry - (The 99th CSJ Annual Meeting), 18 Mar. 2019, English, Invited oral presentation
[Invited]

コア－シェル型高歪化合物の極度に長いＣ–Ｃ単結合と置換基効果　　　　　　　　　　　　　　　
石垣侑祐, 島尻拓哉, 鈴木孝紀
日本化学会第99春季年会, Mar. 2019, Japanese, Oral presentation

大環状ジカチオンの構築と応答挙動　　　　　　　　　　　　　　　
石垣侑祐, 立花拓哉, 林裕貴, 上遠野亮, 鈴木孝紀
化学系学協会北海道支部2019年冬季研究発表会, Jan. 2019, Japanese, Oral presentation

テトラチエニルアントラキノジメタン誘導体の構築と発光性メカノクロミズム　　　　　　　　　　　　　　　
石垣侑祐, 橋本拓実, 菅原一真, 上遠野亮, 鈴木孝紀
化学系学協会北海道支部2019年冬季研究発表会, Jan. 2019, Japanese, Oral presentation

Multi-chromic behavior of tetraarylanthraquinodimethane derivatives: electrochromism in solution and mechanofluorochromism in solid state　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, SUGAWARA Kazuma, KATOONO Ryo, SUZUKI Takanori
The 14th Hokkaido University-Nanjing University-NIMS/MANA Joint Symposium, Dec. 2018, English, Poster presentation

Preparation of 11,11,12,12-tetraarylanthraquinodimethane-type electron donors exhibiting multi-chromic behavior　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, SUGAWARA Kazuma, KATOONO Ryo, SUZUKI Takanori
The 4th International Symposium on Middle Molecular Strategy, Nov. 2018, English, Poster presentation

A Highly Strained Hydrocarbon with a Hyper Covalent Bond Based on the Intramolecular Core-Shell Strategy　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, SHIMAJIRI Takuya, KATOONO Ryo, SUZUKI Takanori
The 6th International Symposium on AMBITIOUS LEADER’S PROGRAM Fostering Future Leaders to Open New Frontiers in Materials Science, Oct. 2018, English, Poster presentation

世界一長い1.8 Åを超えるC–C単結合の創出【優秀ポスター発表賞】　　　　　　　　　　　　　　　
石垣侑祐, 島尻拓哉, 上遠野亮, 鈴木孝紀
第8回CSJ化学フェスタ2018, Oct. 2018, Japanese, Poster presentation

世界最長の炭素－炭素単結合までの道のり　　　　　　　　　　　　　　　
石垣侑祐
北大理学部化学同窓会「るつぼ」セミナー, 28 Sep. 2018, Japanese, Public discourse
[Invited]

Longest C–C single bond with a bond length beyond 1.8 Å based on the intramolecular core-shell strategy　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, SHIMAJIRI Takuya, KATOONO Ryo, SUZUKI Takanori
The Third International Symposium on the Synthesis and Application of Curved Organic π-Molecules & Materials, Sep. 2018, English, Poster presentation
Oxford, UK, [International presentation]

多重クロミズム挙動を示すテトラアリールアントラキノジメタン型電子供与体の構築　　　　　　　　　　　　　　　
石垣侑祐, 菅原一真, 上遠野亮, 鈴木孝紀
第29回基礎有機化学討論会, Sep. 2018, Japanese, Poster presentation
目黒区, [Domestic Conference]

ジベンゾシクロヘプタトリエン誘導体の特異な立体配置に基づく光―熱―酸化還元応答型構造制御　　　　　　　　　　　　　　　
石垣侑祐, 林裕貴, 上遠野亮, 鈴木孝紀
第29回基礎有機化学討論会, Sep. 2018, Japanese, Poster presentation
目黒区, [Domestic Conference]

世界最長の炭素−炭素単結合：1.8 Åを超える超結合の創出　　　　　　　　　　　　　　　
石垣侑祐, 島尻拓哉, 上遠野亮, 鈴木孝紀
第29回基礎有機化学討論会, Sep. 2018, Japanese, Oral presentation
目黒区, [Domestic Conference]

Three-way-output Electrochemical Response by Two-way Structural Modification of Indolocarbazole
NOJO Wataru, KAWADA Yuiki, ISHIGAKI Yusuke, KATOONO Ryo, OHNO Hiroaki, SUZUKI Takanori
日本化学会第98春季年会, Mar. 2018, English, Oral presentation
船橋, [Domestic Conference]

Longest C–C single bond among neutral hydrocarbons with a bond length beyond 1.8 Å based on the intramolecular core-shell strategy
ISHIGAKI Yusuke, SHIMAJIRI Takuya, KATOONO Ryo, SUZUKI Takanori
日本化学会第98春季年会, Mar. 2018, English, Oral presentation
船橋, [Domestic Conference]

動的な8の字キラリティを有するマクロサイクルの縮環多量体における超分子キラリティ(2):o‐フェニレンエチニレン骨格を足場とする縮環三量体
上遠野亮, 坂本和生, 石垣侑祐, 鈴木孝紀
日本化学会第98春季年会, Mar. 2018, Japanese, Oral presentation
船橋, [Domestic Conference]

1,3,5‐トリス(フェニルエチニル)ベンゼンをテンプレートとする大環状分子の合成と錯形成誘起キロプティカル特性
上遠野亮, 河合駿佑, 石垣侑祐, 鈴木孝紀
日本化学会第98春季年会, Mar. 2018, Japanese, Oral presentation
船橋, [Domestic Conference]

動的な8の字キラリティを有するマクロサイクルの縮環多量体における超分子キラリティ(1):o‐フェニレンエチニレン骨格を足場とする縮環二量体
上遠野亮, 青木洸則, 石垣侑祐, 鈴木孝紀
日本化学会第98春季年会, Mar. 2018, Japanese, Oral presentation
船橋, [Domestic Conference]

動的な8の字キラリティを有するマクロサイクルの縮環多量体における超分子キラリティ(3):ヘキサキス(フェニルエチニル)ベンゼンを足場とする縮環四量体
上遠野亮, 小原優大, 齊藤将生, 石垣侑祐, 鈴木孝紀
日本化学会第98春季年会, Mar. 2018, Japanese, Oral presentation
船橋, [Domestic Conference]

テトラアリールアントラキノジメタン型電子供与体の構築とメカノフルオロクロミズム
石垣侑祐, 菅原一真, 島尻拓哉, 上遠野亮, 鈴木孝紀
化学系学協会北海道支部2018年冬季研究発表会, Jan. 2018, Japanese, Oral presentation
札幌, [Domestic Conference]

2つのジベンゾシクロヘプタトリエンを有する高歪み炭化水素の酸化還元応答挙動
石垣侑祐, 林裕貴, 菅原一真, 島尻拓哉, 能條航, 上遠野亮, 鈴木孝紀
化学系学協会北海道支部2018年冬季研究発表会, Jan. 2018, Japanese, Oral presentation
札幌, [Domestic Conference]

〔Major achievements〕ジベンゾシクロヘプタトリエン骨格を有する高歪み炭化水素の特異な性質　　　　　　　　　　　　　　　
石垣侑祐
2017年度高分子・ハイブリッド材料研究センター（PHyM）若手フォーラム, Dec. 2017, Japanese, Invited oral presentation
仙台, [Invited], [Domestic Conference]

Highly strained aromatic hydrocarbons with a bond length of C–C single bond beyond 1.8 Å [Best Poster Award]　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, SHIMAJIRI Takuya, KATOONO Ryo, SUZUKI Takanori
The 18th RIES-HOKUDAI International Symposium, Nov. 2017, English, Poster presentation
Sapporo, Japan, [International presentation]

A Novel Electrochromic System with Perfluoroarenes: Conjugated Diene-type Electron Donor and Its Dication　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, SUGIMOTO Keisuke, KATOONO Ryo, SUZUKI Takanori
The 18th RIES-HOKUDAI International Symposium, Nov. 2017, English, Poster presentation
Sapporo, Japan, [International presentation]

Highly Strained Caged Hydrocarbons with an Ultralong C–C Single Bond　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, SHIMAJIRI Takuya, KATOONO Ryo, SUZUKI Takanori
The 5th International Symposium on AMBITIOUS LEADER’S PROGRAM Fostering Future Leaders to Open New Frontiers in Materials Science, Nov. 2017, English, Poster presentation
Sapporo, Japan, [International presentation]

極度に伸長したC‐C単結合を有するジスピロジベンゾシクロヘプタトリエン誘導体の合成/構造/性質
石垣侑祐, 島尻拓哉, 上遠野亮, 鈴木孝紀
第28回基礎有機化学討論会, Sep. 2017, Japanese, Poster presentation
福岡, [Domestic Conference]

フェニルアセチレンマクロサイクル(PAM)の分子集合と架橋により創り出されるヘリカルキラリティ
上遠野亮, 小原優大, 河合駿佑, 日下慶一, 石垣侑祐, 鈴木孝紀
第28回基礎有機化学討論会, Sep. 2017, Japanese, Oral presentation
福岡, [Domestic Conference]

スピロ縮環型ジヒドロフェナントレン誘導体:立体障害に基づく炭素‐炭素単結合の伸長
石垣侑祐, 林裕貴, 菅原一真, 島尻拓哉, 上遠野亮, 鈴木孝紀
第28回基礎有機化学討論会, Sep. 2017, Japanese, Poster presentation
福岡, [Domestic Conference]

A Novel Redox System Based on Perfluoroarenes: Toward Advanced Response Systems Assembled by SNAr Reaction　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, SUGIMOTO Keisuke, TAMAOKI Hitomi, KATOONO Ryo, SUZUKI Takanori
The 17th International Symposium on Novel Aromatic Compounds, Jul. 2017, English, Poster presentation
Stony Brook, USA, [International presentation]

1.80Åを超えるC‐C単結合:実験値と理論値の比較
石垣侑祐, 島尻拓哉, 内村康人, 上遠野亮, 鈴木孝紀
日本化学会第97春季年会, Mar. 2017, Japanese, Oral presentation
横浜, [Domestic Conference]

複数のベンゾインドロカルバゾール(BIC)骨格を有する多電子供与体の合成と酸化還元特性
鈴木孝紀, 能條航, 石垣侑祐, 上遠野亮
日本化学会第97春季年会, Mar. 2017, Japanese, Oral presentation
横浜, [Domestic Conference]

ジベンゾシクロヘプタトリエンがスピロ縮環したジヒドロピラシレン誘導体：1.8 Åを超えるC−C単結合　　　　　　　　　　　　　　　
石垣侑祐, 島尻拓哉, 上遠野亮, 鈴木孝紀
化学系学協会北海道支部2017年冬季研究発表会, Jan. 2017, Japanese, Oral presentation
札幌, [Domestic Conference]

フッ化アレーン骨格を有する共役ジエン型電子供与体の構築と酸化還元挙動　　　　　　　　　　　　　　　
石垣侑祐, 杉本佳亮, 石割文崇, 上遠野亮, 福島孝典, 鈴木孝紀
化学系学協会北海道支部2017年冬季研究発表会, Jan. 2017, Japanese, Oral presentation
札幌, [Domestic Conference]

A Novel Electrochromic Systems Based on Bis(diarylethenyl)-thiophene Framework Exhibiting a Fluorescence Response　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, KATOONO Ryo, SUZUKI Takanori
The 10th International Symposium on Integrated Synthesis, Nov. 2016, English, Poster presentation
Awaji, Japan, [International presentation]

極限まで伸長したC‐C結合の伸長性:温度上昇に伴う結合の更なる伸長
内村康人, 石垣侑佑, 上遠野亮, 鈴木孝紀
第27回基礎有機化学討論会, Sep. 2016, Japanese, Poster presentation
広島, [Domestic Conference]

三層構造を有するシクロファンの錯体形成誘起CDにおける特異な温度依存性
上遠野亮, 小原優大, 石垣侑祐, 鈴木孝紀
第27回基礎有機化学討論会, Sep. 2016, Japanese, Poster presentation
広島, [Domestic Conference]

キラリティ伝達によらない動的らせん性制御
上遠野亮, 石垣侑祐, 鈴木孝紀
第27回基礎有機化学討論会, Sep. 2016, Japanese, Oral presentation
広島, [Domestic Conference]

ビス(トリアリールメチリウム)とシクロデキストリンの立体選択的錯形成:軸不斉ジカチオンに対するキラル認識の起源
鈴木孝紀, CERON‐CARRASCO Jose P, 玉置瞳美, 石垣侑祐, 上遠野亮, PEREZ‐SANCHEZ Horacio
第27回基礎有機化学討論会, Sep. 2016, Japanese, Poster presentation
広島, [Domestic Conference]

架橋鎖で連結された4,4’‐フェニルエチニリデンジアニリン類の合成とその動的酸化還元挙動に基づくエレクトロクロミズム
鈴木孝紀, 花田佳祐, 石垣侑祐, 樋口博紀, 上遠野亮, 藤原憲秀
第25回基礎有機化学討論会, Sep. 2014, Japanese, Poster presentation
仙台, [Domestic Conference]

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
第24回基礎有機化学討論会, Sep. 2013, Japanese, Poster presentation
文京区, [Domestic Conference]

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
第23回基礎有機化学討論会, Sep. 2012, Japanese, Poster presentation
京都, [Domestic Conference]

水溶性置換基を導入したジアリールエテニル型電子供与体の構築と酸化還元挙動
石垣侑祐, 上遠野亮, 藤原憲秀, 鈴木孝紀
日本化学会第92春季年会, Mar. 2012, Japanese, Oral presentation
横浜, [Domestic Conference]

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2012年冬季研究発表会, Jan. 2012, Japanese
札幌, [Domestic Conference]

Unsymmetrically Substituted Hexaphenylethane Derivatives: Efficient Synthesis by Using Flow Microreactor and Chiral Transmission　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, KAWAI Hidetoshi, FUJIWARA Kenshu, NAGAKI Aiichiro, YOSHIDA Jun-ichi, SUZUKI Takanori
The Seventh International Symposium on Integrated Synthesis, Oct. 2011, English, Poster presentation
Kobe, Japan, [International presentation]

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
第22回基礎有機化学討論会, Sep. 2011, Japanese, Poster presentation
つくば, [Domestic Conference]

キラルリオトロピック液晶のらせん構造の電気化学的制御
樋口博紀, 堀之内智弘, 石垣侑祐, 奥村泰志, 鈴木孝紀, 菊池裕嗣
第60回高分子討論会, Sep. 2011, Japanese, Oral presentation
岡山, [Domestic Conference]

A Novel π-Extended Redox Systems Based on the Bis(diarylethenyl)thiophene Framework Exhibiting Electrochromism　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, HOSHIYAMA Yuki, KAWAI Hidetoshi, FUJIWARA Kenshu, HIGUCHI Hiroki, KIKUCHI Hirotsugu, SUZUKI Takanori
The 14th International Symposium on Novel Aromatic Compounds, Jul. 2011, English, Poster presentation
Eugene, USA, [International presentation]

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
日本化学会第91春季年会, Mar. 2011, Japanese
日本化学会第91春季年会(2011)講演予稿集, [Domestic Conference]

長鎖アルキル基を有するキラルなジヒドロ[5]ヘリセン誘導体の酸化還元挙動に基づく多重出力応答
石垣侑祐, 吉田聡茂, 河合英敏, 藤原憲秀, 鈴木孝紀
化学系学協会北海道支部2011年冬季研究発表会, Jan. 2011, Japanese, Oral presentation
札幌, [Domestic Conference]

A New Series of Electrochromic Systems Based on Bis(diarylethenyl)thiophene Framework　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, HIGUCHI Hiroki, KAWAI Hidetoshi, FUJIWARA Kenshu, SUZUKI Takanori
PACIFICHEM 2010, Dec. 2010, English, Poster presentation
Honolulu, USA, [International presentation]

2,5-ビス(ジアリールエテニル)チオフェンを基本骨格としたπ拡張系の構築とエレクトロクロミズム　　　　　　　　　　　　　　　
石垣侑祐, 樋口博紀, 河合英敏, 藤原憲秀, 鈴木孝紀
第4回有機π電子系シンポジウム, Nov. 2010, Japanese, Poster presentation
神戸, [Domestic Conference]

2,5‐チエニレン(10‐メチル‐9‐メチレンアクリダン)及び高次類縁体の合成と可逆なエレクトロクロミズム挙動
鈴木孝紀, 星山裕希, 石垣侑祐, 三浦洋平, 河合英敏, 藤原憲秀
第21回基礎有機化学討論会, Sep. 2010, Japanese, Poster presentation
名古屋, [Domestic Conference]

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
第21回基礎有機化学討論, Sep. 2010, Japanese, Poster presentation
名古屋, [Domestic Conference]

ねじれたパイ系を有する酸化還元系の多重出入力応答機能
鈴木孝紀, 石垣侑祐, 河合英敏, 藤原憲秀
シンポジウム「モレキュラー・キラリティー」2010, Jul. 2010, Japanese
札幌

2,5‐ビス(ジアリールエテニル)チオフェンを基本骨格とする酸化還元系の構築とエレクトロクロミズム
石垣侑祐, 樋口博紀, 河合英敏, 藤原憲秀, 鈴木孝紀
日本化学会第90春季年会, Mar. 2010, Japanese, Oral presentation
東大阪, [Domestic Conference]

Multi-input-Multi-output Molecular Response System Based on Dynamic Redox Behavior of Binaphthyl-type Stable Dications Exhibiting Solvatochromism　　　　　　　　　　　　　　　
ISHIGAKI Yusuke, KAWAI Hidetoshi, FUJIWARA Kenshu, SUZUKI Takanori
The 12TH SNU and Hokkaido University Joint Symposium On Nano Green Chemistry for Sustainable Society, Nov. 2009, English, Poster presentation
Seoul, South Korea, [International presentation]

ソルバトクロミズムを示すキラルなジヒドロ[5]ヘリセン誘導体の酸化還元挙動に基づく多重入力‐多重出力型応答機能
石垣侑祐, 河合英敏, 藤原憲秀, 鈴木孝紀
第20回基礎有機化学討論会, Sep. 2009, Japanese, Oral presentation
桐生, [Domestic Conference]

不斉記憶の可能なヘキサフェニルエタン型エレクトロクロミズム系の構築とキロオプティカル特性
鈴木孝紀, 和田和久, 石垣侑祐, 河合英敏, 藤原憲秀
第20回基礎有機化学討論会, Sep. 2009, Japanese, Poster presentation
桐生, [Domestic Conference]

Multi-input–Multi-output Molecular Response System Based on 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　　　　　　　　　　　　　　　
SUZUKI Takanori, ISHIGAKI Yusuke, KAWAI Hidetoshi, FUJIWARA Kenshu
Japan-China Joint Symposium on Functional Supramolecular Architectures, Aug. 2009, English, Poster presentation
Sapporo, Japan, [International presentation]

Multi-input-multi-output Molecular Response System Based on Dynamic Redox Behavior of 3,3,4,4-Tetraaryldihydro[5]helicene Derivatives　　　　　　　　　　　　　　　
SUZUKI Takanori, ISHIGAKI Yusuke, KAWAI Hidetoshi, FUJIWARA Kenshu
International Symposium for Environmental Innovation Driven by Chemistry and Catalytic Science, Mar. 2009, English, Poster presentation
Sapporo, Japan, [International presentation]

Multi-input-multi-output molecular response based on the dynamic redox-behavior of chiral dihydro[5]helicene derivatives with four alkoxyphenyl groups
鈴木孝紀, 石垣侑祐, 河合英敏, 藤原憲秀
日本化学会第89春季年会, Mar. 2009, Japanese, Oral presentation
船橋, [Domestic Conference]

不斉記憶の可能なヘキサフェニルエタン型エレクトロクロミズム系の設計と構築
鈴木孝紀, 和田和久, 石垣侑祐, 葭本泰代, 河合英敏, 藤原憲秀
化学系学協会北海道支部2009年冬季研究発表会, Jan. 2009, Japanese, Oral presentation
札幌, [Domestic Conference]

Multi-input-multi-output Molecular Response Systems Based on Dihydro[5]helicene Derivatives with Four Alkoxyphenyl Groups　　　　　　　　　　　　　　　
SUZUKI Takanori, ISHIGAKI Yusuke, KAWAI Hidetoshi, FUJIWARA Kenshu
The 4TH Hokkaido-Nanjing University Joint Symposium, Dec. 2008, English, Poster presentation
Sapporo, Japan, [International presentation]

長鎖アルコキシフェニル基が置換したジヒドロフェナントレン誘導体の溶媒依存型酸化還元挙動
鈴木孝紀, 石垣侑祐, 河合英敏, 藤原憲秀, 池田浩, 狩野佑介, 水野一彦
第19回基礎有機化学討論会, Sep. 2008, Japanese, Poster presentation
大阪, [Domestic Conference]

長鎖アルキル基を有するヘキサフェニルエタン型動的酸化還元系の構築と応答挙動
鈴木孝紀, 石垣侑祐, 樋口博紀, 河合英敏, 藤原憲秀
日本化学会北海道支部2008年夏季研究発表会, Jul. 2008, Japanese, Oral presentation
北見, [Domestic Conference]

長鎖アルキル基を有する動的酸化還元系の合成と応答挙動
鈴木孝紀, 石垣侑祐, 武田貴志, 岩井智弘, 太田英輔, 樋口博紀, 河合英敏, 藤原憲秀
日本化学会北海道支部2008年冬季研究発表会, Jan. 2008, Japanese, Oral presentation
札幌, [Domestic Conference]

先端総合化学特論Ⅱ [分担, 英語]　　　　　　　　　　　　　　　
北海道大学

化学実験Ⅵ：有機化学実験 [分担]　　　　　　　　　　　　　　　
北海道大学

自然科学実験 [共同担当]　　　　　　　　　　　　　　　
北海道大学

一般教育演習：現代有機化学演習 [分担]　　　　　　　　　　　　　　　
北海道大学

有機機器分析 [単独担当]　　　　　　　　　　　　　　　
北海道大学

未踏高密度カチオンを基盤とする機能創製
戦略的な研究開発の推進 戦略的創造研究推進事業 さきがけ
2023 - 2026
石垣 侑祐
本研究では、カチオン部位が規則的に配列した分子を構築することで、高密度カチオンのトポロジーに基づく機能創製を目指します。カチオン部位のトポロジカル配列に基づく包接能の制御及び未踏π共役系分子の構築へと繋げる狙いです。これにより、従来は主に中性分子において開拓されてきた物質探索領域を有機カチオン種へと拡げ、高密度かつ規則的に配列した多価カチオン種を基盤とする未来材料創製に挑戦します。
科学技術振興機構, 北海道大学, Principal investigator

Flexible control of covalent bonds based on redox-active highly strained compounds
Grants-in-Aid for Scientific Research
01 Apr. 2021 - 31 Mar. 2025
石垣 侑祐
本研究では，極度に伸長した結合をもつ高歪化合物，あるいは光／熱などの外部刺激により構造変化を示すレドックス活性分子に着目し，前例のない応答性分子の創出を目的に，以下の三つの課題を並行して進めた。
課題Iでは，限界を超えて伸長した単結合をもつ化合物群の構築が重要となる。これまでに対称／非対称トロポン誘導体の合成法を確立したことから，これらを原料に伸長した結合を有する分子群を合成した。結晶中での結合長を温度可変単結晶X線結晶構造解析により明らかにし，極度に伸長した結合をもつことを見出した。
課題IIでは，先に見出した光／熱異性化を示す分子をベースに，従来にない機能創出を目指して非対称誘導体を設計，合成した。非対称化することで，中央六員環の環反転が異性化制御に重要な役割を担っていることを明らかにした。また，これらの構造変化ダイナミクスの詳細について，理論計算による裏付けを行い，次年度以降につながる分子設計指針を獲得することができた。
課題IIIでは，本研究に先立って合成したビスキノジメタン（BQD）誘導体に着目し，骨格拡張による多価カチオンの合成とアセン創出を目指して研究を実施した。BQD誘導体では，四電子酸化することでペンタセン骨格を有するテトラカチオンが形成する一方，還元過程では二段階の二電子還元が進行することを明らかにし，アントラセン骨格を有するジカチオンを中間体として経由するユニークな特性を有している。これらを踏まえ，現在までに中央骨格のπ拡張を行い，高次アセンの形成を示唆する結果が得られている。
以上の知見を基に，今後さらに研究を加速させる計画である。
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 21H01912

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
科学研究費助成事業 基盤研究(B)
01 Apr. 2020 - 31 Mar. 2025
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。
日本学術振興会, 基盤研究(B), 北海道大学, 20H02719

精密分子設計に基づく超近接π積層の実現と高密度共役状態のレドックス制御　　　　　　　　　　　　　　　
科学研究費助成事業 学術変革領域研究(A)
Apr. 2023 - Mar. 2025
石垣侑祐
日本学術振興会, 北海道大学, Principal investigator, 23H04011

高ひずみ化合物の精密分子合成に基づくメカノクロミックポリマーの開発　　　　　　　　　　　　　　　
2023年度豊田理研スカラー共同研究
Apr. 2023 - Mar. 2024
石垣侑祐, 百合野大雅, 小野利和
公益財団法人 豊田理化学研究所, 北海道大学

近赤外吸収を示す安定な有機多価カチオン種の創成とレドックス応答　　　　　　　　　　　　　　　
2022年度研究助成
Aug. 2022 - Mar. 2024
石垣侑祐
一般財団法人 イオン工学振興財団, 北海道大学, Principal investigator

Construction of super-close pi-dimer toward condensed conjugation based on precise control of interatomic distance
Grants-in-Aid for Scientific Research
10 Sep. 2021 - 31 Mar. 2023
石垣 侑祐
本研究は，本学術変革領域が目指す"X"-conjugationの学理確立に向け，原子間距離を緻密に制御することで，特異な電子状態に基づく未踏機能の実現に寄与することを目的とし、以下の三つの課題を推進している。
課題Iでは，空隙の最小化による高密度共役の実現に向け，『極度に伸長したC-C単結合の切断に基づく超近接πダイマー創製』を進めている。具体的には，長いσ結合種を前駆体とするπダイマー創出アプローチを提案し，実験及び理論計算の両面から検討を実施した。その結果，前駆体であるジカチオン種において3.0 Åを下回る炭素…炭素原子間距離を明らかにし，興味深いレドックス特性を見出した。
課題IIでは，非結合状態のさらなる安定化と，外部刺激による劇的な電子構造変化を目的とし，『ヘテロ原子への展開によるσ結合／超近接πダイマーの外部刺激制御』を推進している。現在までに，窒素原子を導入した誘導体を構築し，合成過程で新規π共役系分子の創出を実現した。これらについてさらなる検討を行う。
課題IIIでは，レドックス活性部位を大環状分子に組み込むことで，それぞれの酸化状態に応じてユニット間距離を高度に制御することを目的とし，『シクロファン型酸化還元系の創製に基づく三次元共役の実現』に挑戦している。これまでに，二つのタイプの大環状ジカチオンを構築し，固相，あるいは溶液相において分子内相互作用の発現を確認している。シクロファン型分子構築法の確立に成功したため，酸化還元による物性変調を達成し，三次元共役の実現へとつなげる。
Japan Society for the Promotion of Science, Grant-in-Aid for Transformative Research Areas (A), Hokkaido University, 21H05468

酸化還元反応を利用した平面π共役系分子の新規構築法の開発　　　　　　　　　　　　　　　
DIC研究企画賞
Apr. 2021 - Mar. 2023
石垣 侑祐
有機合成化学協会, 北海道大学

精密分子合成を基盤とする革新的多孔質有機結晶の創製と機能評価　　　　　　　　　　　　　　　
2021年度豊田理研スカラー共同研究
Apr. 2021 - Sep. 2022
石垣侑祐,百合野大雅,井口弘章,小野利和
公益財団法人 豊田理化学研究所, 北海道大学

Highly Strained Compounds with Seven-Membered Rings: Construction of Unique Structures and Development of Functions
Grants-in-Aid for Scientific Research Grant-in-Aid for Early-Career Scientists
01 Apr. 2019 - 31 Mar. 2022
Yusuke ISHIGAKI
The carbon-carbon covalent bond is one of the most basic concept in organic chemistry. Bond length and bond angle among carbon atoms are nearly constant on the basis of the bond order and hybrid orbitals. On the other hand, highly strained compounds have attracted much attention with regard to their characteristic features. Regarding the C-C single bond, several attempts have been made to elongate the C-C single bond to gain new insight into the chemical bond and understand what happens at the limit of a bond. In addition, while the standard C=C double bond prefers a planar geometry, overcrowded ethylenes with bulky substituents can adopt folded and/or twisted forms due to the steric hindrance around the central C=C double bond.
In this study, focusing on highly strained π-electronic systems, a control of structures and physical properties based on extremely elongated C-C single bonds and highly strained C=C double bonds was accomplished.
Japan Society for the Promotion of Science, Grant-in-Aid for Early-Career Scientists, Hokkaido University, Principal investigator, Competitive research funding, 19K15528

分子構造スイッチングに基づく革新的応答系の開発　　　　　　　　　　　　　　　
2020年度豊田理研スカラー
Apr. 2020 - Mar. 2021
石垣侑祐
公益財団法人 豊田理化学研究所, 北海道大学, Principal investigator

硫化水素で活性化される近赤外色素プローブの開発:バイオイメージングと医療への応用　　　　　　　　　　　　　　　
第33回ノバルティス研究奨励金
Apr. 2020 - Mar. 2021
石垣侑祐
公益財団法人 ノバルティス科学振興財団, 北海道大学, Principal investigator

特異な構造変化を示す超混雑エチレン類の開発とその応用　　　　　　　　　　　　　　　
工学研究奨励援助金
2020 - 2021
石垣侑祐
公益財団法人 服部報公会, 北海道大学

高歪み化合物に基づく新奇応答性分子の開発　　　　　　　　　　　　　　　
若手研究加速事業
Apr. 2019 - Mar. 2020
ISHIGAKI Yusuke
Hokkaido University, 北海道大学, Principal investigator

世界最長の炭素－炭素単結合に基づく新規応答機能の発現　　　　　　　　　　　　　　　
笹川科学研究助成
Apr. 2019 - Feb. 2020
石垣 侑祐
公益財団法人 日本科学協会, Principal investigator, Competitive research funding

分子内コアーシェル構造を鍵とする「超結合」 の概念確立と機能開拓　　　　　　　　　　　　　　　
研究助成
Sep. 2018 - Aug. 2019
Yusuke ISHIGAKI
TOBE MAKI Scholarship Foundation, Principal investigator, Competitive research funding

Toward the realization of higher-order response system exhibiting expandability/fissionability of the extremely elongated C-C single bond
Grants-in-Aid for Scientific Research Grant-in-Aid for Research Activity Start-up
26 Aug. 2016 - 31 Mar. 2018
Ishigaki Yusuke
The C-C single bond length of 1.791(3) angstrom has been considered the longest value among neutral organic compounds. Expandability/fissionability of such a long bond in crystals plays an important role for construction of response system. Toward the realization of higher-order response system, further longer C-C bond could work efficiently due to large expandability of the weakened bond. Therefore, we have designed a compound with a bond length beyond 1.8 angstrom.
In this study, a highly strained hydrocarbon, which has the longest C-C single bond with a bond length of 1.806(2) angstrom, has been synthesized based on the intramolecular "core-shell strategy": the weak C-C bond (core) is protected by the shape-persistent sp2 carbon framework (shell). We proposed to term the C-C bond with a bond length of 1.8-2.0 angstrom "hyper covalent bond".
Japan Society for the Promotion of Science, Grant-in-Aid for Research Activity Start-up, Hokkaido University, Principal investigator, Competitive research funding, 16H06591

長鎖アルキル基を有する酸化還元系分子の集積化:次元的秩序性の実現と外部刺激制御
Grants-in-Aid for Scientific Research Grant-in-Aid for JSPS Fellows
2010 - 2012
Yusuke ISHIGAKI
長鎖アルキル基を有する酸化還元系分子の集積化に向け,前年度は酸化還元系分子を非対称化させることで新たな特性の付与を目指した研究を展開した。
本年度の研究では,ジアリールエテニル型化合物のアリール基上に水溶性置換基を導入することで,ジカチオン状態と中性状態のどちらも水に可溶な酸化還元系の構築を目指した。今回合成した7種類の化合物は,酸化種が共役で安定化されるもの,オリゴマー化するもの,あるいは分子内で環化するものなど,中心骨格の種類により特徴づけられる様々な応答挙動を示すと期待した。さらに,ジアルキルアミノフェニル基を有するカチオン種は水中でも安定であるため,可逆な酸化還元に基づくエレクトロクロミズム挙動は水中でも観測できると考えた。
合成は,ジアルデヒド体を出発物質とするWittig-Horner反応により行い,7つの水溶性化合物をそれぞれ良好な収率で得た。これらの化合物はヨウ素により容易にカチオン種へと酸化され,得られた酸化種はZn還元により元の中性体を再生することを確認した。
続いて電気化学応答を調査すると,中心骨格にアントラセンを有する誘導体がジクロロメタン中と水中のどちらでも等吸収点を有するクリーンな酸化還元挙動を示し,キノイド型の酸化種と相互変換することを明らかにした。また,ビナフチル型誘導体においては分子内での結合形成・切断に伴って可逆性の高い酸化還元挙動を示すことを見出した。これらの誘導体は有機溶媒及び水に十分可溶であるため,溶媒による酸化還元挙動の変化や,長鎖アルキル基の効果による水中での凝集体の観測など,さらなる展開が期待できるものである。
Japan Society for the Promotion of Science, Grant-in-Aid for JSPS Fellows, Hokkaido University, Principal investigator, Competitive research funding, 10J00648

Bachelor's degree program, School of Science

Master's degree program, Graduate School of Chemical Sciences and Engineering

Doctoral (PhD) degree program, Graduate School of Chemical Sciences and Engineering