Researcher Database

Takanori Suzuki
Faculty of Science Chemistry Organic and Biological Chemistry
Professor

Researcher Profile and Settings

Affiliation

  • Faculty of Science Chemistry Organic and Biological Chemistry

Job Title

  • Professor

Degree

  • Doctor of Science, April 1988, Tohoku University(Tohoku University)

URL

Research funding number

  • 70202132

J-Global ID

Research Interests

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

Research Areas

  • Life sciences / Bioorganic chemistry
  • Nanotechnology/Materials / Structural/physical organic chemistry
  • Nanotechnology/Materials / Functional solid-state chemistry
  • Nanotechnology/Materials / Synthetic organic chemistry
  • Manufacturing technology (mechanical, electrical/electronic, chemical engineering) / Electronic devices and equipment
  • Life sciences / Bioorganic chemistry
  • Nanotechnology/Materials / Structural/physical organic chemistry

Academic & Professional Experience

  • 2006/04 - Today Hokkaido University Faculty of Science, Department of Chemistry
  • 2002/04 - 2006/03 北海道大学大学院理学研究科化学専攻 教授
  • 1995/01 - 2002/03 Hokkaido University School of Science
  • 1989/04 - 1994/12 Tohoku University Faculty of Science, Department of Chemistry
  • 1988/04 - 1989/03 JSPS PD (東北大学理学部化学科)

Education

  • 1986/04 - 1988/04  東北大学大学院理学研究科化学専攻博士後期課程(短縮修了)
  •        - 1988  Tohoku University  Graduate School, Division of Natural Science
  • 1984/04 - 1986/03  Tohoku University
  •        - 1986  Tohoku University  Graduate School, Division of Natural Science
  • 1980/04 - 1984/03  Tohoku University  Faculty of Science
  •        - 1984  Tohoku University  Faculty of Science

Association Memberships

  • 基礎有機化学会   日本化学会   有機合成化学協会   

Research Activities

Published Papers

  • Wataru Nojo, Yusuke Ishigaki, Takashi Takeda, Tomoyuki Akutagawa, Takanori Suzuki
    Chemistry – A European Journal Wiley 2019/06 [Refereed][Not invited]
  • Ryo Katoono, Kazuki Sakamoto, Takanori Suzuki
    Chemical Communications Royal Society of Chemistry ({RSC}) 2019 [Refereed][Not invited]
  • Ryo Katoono, Keiichi Kusaka, Yuki Saito, Kazuki Sakamoto, Takanori Suzuki
    Chemical Science Royal Society of Chemistry ({RSC}) 2019 [Refereed][Not invited]
  • Luyan Wu, Yidan Sun, Keisuke Sugimoto, Zhiliang Luo, Yusuke Ishigaki, Kanyi Pu, Takanori Suzuki, Hong-Yuan Chen, Deju Ye
    Journal of the American Chemical Society American Chemical Society ({ACS}) 2018/11 [Refereed][Not invited]
  • Yusuke Ishigaki, Tomohiro Iwai, Yuki Hayashi, Aiichiro Nagaki, Ryo Katoono, Kenshu Fujiwara, Jun-ichi Yoshida, Takanori Suzuki
    SYNLETT 29 (16) 2147 - 2154 0936-5214 2018/10 [Refereed][Not invited]
     
    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.
  • Wataru Nojo, Hitomi Tamaoki, Yusuke Ishigaki, Ryo Katoono, Kenshu Fujiwara, Takanori Fukushima, Takanori Suzuki
    ChemPlusChem Wiley 84 (6) 634  2018/08 [Refereed][Not invited]
  • Yusuke Ishigaki, Takuya Shimajiri, Takashi Takeda, Ryo Katoono, Takanori Suzuki
    Chem 4 (4) 795 - 806 2451-9294 2018/04/12 [Refereed][Not invited]
     
    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.
  • Yasuto Uchimura, Takuya Shimajiri, Yusuke Ishigaki, Ryo Katoono, Takanori Suzuki
    Chemical Communications Royal Society of Chemistry ({RSC}) 2018 [Refereed][Not invited]
  • Ryo Katoono, Yudai Obara, Keiichi Kusaka, Takanori Suzuki
    Chemical Communications 54 (7) 735 - 738 1364-548X 2018 [Refereed][Not invited]
     
    We synthesized molecular assemblies of a ring and rod that were covalently bound in a molecule. The bridged components were helically arranged in a threaded or unthreaded form to show unique chiroptical properties based on shape-persistent m-phenylacetylene rings with six, five and four units and phenylene-ethynylene rods.
  • Ryo Katoono, Keiichi Kusaka, Yuki Tanaka, Kenshu Fujiwara, Takanori Suzuki
    Organic and Biomolecular Chemistry 16 (7) 1167 - 1171 1477-0520 2018 [Refereed][Not invited]
     
    We demonstrate a chiroptical switching system with a simple molecule. The molecule contains a pair of chromophores of diphenylacetylene that are linked with a diyne bond and arranged to exert exciton coupling in helically folded forms with (M)- or (P)-helicity. A tertiary amide group is attached to each end of the looped molecule. The amide carbonyls were used to capture a ditopic hydrogen-bonding guest. A chiral auxiliary group on the amide nitrogen acted as a chiral handle to control the helical-sense preference of dynamic helical forms of the loop. The helical-sense preference is brought about by an intramolecular transmission of point chirality associated with the loop. The preferred sense was switched upon complexation with an achiral additive through the formation of hydrogen bonds. In both states, before and after complexation, the helical-sense preferences were controlled through two-way transmission of the single chiral source.
  • Ryo Katoono, Yudai Obara, Kenshu Fujiwara, Takanori Suzuki
    Chemical Science 9 (8) 2222 - 2229 2041-6539 2018 [Refereed][Not invited]
     
    When two planes stacked one above the other are twisted, they provide a dynamic pair of helical conformations with (M)- or (P)-helicity. We designed a three-layer cyclophane that consists of two such dynamic pairs: the top and middle planes, and the middle and bottom planes. Hence, several global conformations could be created for the overall molecule, e.g., double-helical forms with a pair with the same helicity [(M,M) or (P,P)], and a meso-like form with a pair with a different helicity (M,P). These conformations dynamically interconvert to each other in solution. Chiroptical properties were given by the helical-sense preference of the double-helical forms, which was brought about through complexation with a chiral hydrogen-bonding guest. In terms of the conformational energy in a complexed state, when a desirable relationship between double-helical and meso-like forms was attained, complexation-induced circular dichroism was enhanced at elevated temperatures and decreased at lowered temperatures.
  • Yuiki Kawada, Shunsuke Ohmura, Misaki Kobayashi, Wataru Nojo, Masaki Kondo, Yuka Matsuda, Junpei Matsuoka, Shinsuke Inuki, Shinya Oishi, Chao Wang, Tatsuo Saito, Masanobu Uchiyama, Takanori Suzuki, Hiroaki Ohno
    Chemical Science 9 (44) 8416 - 8425 2041-6520 2018 [Refereed][Not invited]
     

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

  • Yusuke Ishigaki, Yuki Hayashi, Kazuma Sugawara, Takuya Shimajiri, Wataru Nojo, Ryo Katoono, Takanori Suzuki
    MOLECULES 22 (11) 1420-3049 2017/11 [Refereed][Not invited]
     
    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.
  • 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 2192-6506 2017/07 [Refereed][Not invited]
     
    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.
  • Eisuke Ohta, Hiromitsu Uehara, Ying Han, Kazuhisa Wada, Hidenori Noguchi, Ryo Katoono, Yusuke Ishigaki, Hiroshi Ikeda, Kohei Uosaki, Takanori Suzuki
    ChemPlusChem Wiley-Blackwell 82 (7) 2017/07 [Refereed][Not invited]
  • Hitomi Tamaoki, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki
    Angewandte Chemie International Edition Wiley-Blackwell 55 (7) 2586  1433-7851 2016/02 [Refereed][Not invited]
  • Hitomi Tamaoki, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki
    Angewandte Chemie Wiley-Blackwell 128 (7) 2628  2016/02 [Refereed][Not invited]
  • Ryo Katoono, Takanori Suzuki
    Chem. Commun. Royal Society of Chemistry ({RSC}) 52 (5) 1031  1359-7345 2016 [Refereed][Not invited]
  • Takanori Suzuki, Yuto Sakano, Tomohiro Iwai, Shinichi Iwashita, Youhei Miura, Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara, Yasushi Tsuji, Takanori Fukushima
    ChemInform Wiley-Blackwell 46 (38) no  2015/09 [Refereed][Not invited]
  • Ryo Katoono, Yuki Tanaka, Keiichi Kusaka, Kenshu Fujiwara, Takanori Suzuki
    JOURNAL OF ORGANIC CHEMISTRY 80 (15) 7613 - 7625 0022-3263 2015/08 [Refereed][Not invited]
     
    We demonstrate two types of inversion of a helical preference upon the 1:1 complexation of a dynamic figure eight molecule with a guest molecule through the controlled transmission of point chirality. We designed a series of macrocycles that prefer a nonplanar conformation with figure eight chirality. These macrocycles are composed of a chirality-transferring unit (terephthalamide) and a structure-modifying unit (two o-phenylene rings spaced with a varying number of triple bonds). The former unit provides a binding site for capturing a guest molecule through the formation of hydrogen bonds. The attachment of chiral auxiliaries to the former unit induces a helical preference for a particular sense through the intramolecular transmission of point chirality. For relatively small-sized macrocycles, the preferred sense was reversed upon complexation with an achiral guest. Contrary preferences before and after complexation were both seen for chiral auxiliaries associated with a figure eight host through two-way intramolecular transmission of the single chiral source. Alternatively, the helical preference induced in relatively large-sized macrocycles was reversed only when a figure eight host formed a 1:1 complex with a particular enantiomeric guest through the supramolecular transmission of point chirality in the guest. This stereospecific inversion of a helical preference is rare.
  • Takanori Suzuki, Yu Umezawa, Yuto Sakano, Hitomi Tamaoki, Ryo Katoono, Kenshu Fujiwara
    CHEMISTRY LETTERS 44 (7) 905 - 907 0366-7022 2015/07 [Refereed][Not invited]
     
    11,11,12,12-Tetrakis (4-methoxyphenyl)-1,4-diaza-2,3-diphenyl- and -1,4,5,8-tetraaza-2,3,6,7-tetraphenylanthraquinodimethanes (1 and 2) adopt a bent geometry. They undergo reversible redox interconversion with twisted dications 1(2+) and 2(2+), exhibiting a vivid change in color (electrochromism). Treatment with acid also induced drastic color change due to the formation of protonated species H-1(+) and H-2(+) (halochromism), thus demonstrating their two-way-input chromic behavior.
  • Takanori Suzuki, Takashi Takeda, Eisuke Ohta, Kazuhisa Wada, Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara
    ChemInform Wiley-Blackwell 46 (18) no  2015/04 [Refereed][Not invited]
  • Yasuto Uchimura, Takashi Takeda, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 54 (13) 4010 - 4013 1433-7851 2015/03 [Not refereed][Not invited]
     
    Upon reduction of a 1H-cyclobuta[de] naphthalene-4,5-diylbis(diarylmethylium) species, a new C-C bond is formed between the C-alpha and C-ortho atoms of the two chromophores, which presents an unprecedented coupling pattern for the dimerization of two trityl units. By attaching an annulated cyclobutane ring at the opposite peri position of the naphthalene core, the distance between the C-alpha carbon atoms was elongated beyond the limit of sigma-bond formation through "scissor effects". The suppression of C-alpha-C-alpha bond formation, which would lead to hexaphenylethane-type compounds, is key to the first successful isolation of the alpha,o-adducts. The 5-diarylmethylene-6-triarylmethyl-1,3-cyclohexadiene unit in the alpha,o-adducts is stable, and isomerization of the cyclohexadiene unit into an aromatic system was not observed. The newly formed C-alpha-C-ortho bond was cleaved upon two-electron oxidation to regenerate the dicationic dye.
  • Yasuto Uchimura, Takashi Takeda, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Wiley-Blackwell 54 (13) 4010 - 4013 1433-7851 2015/03 [Refereed][Not invited]
     
    Upon reduction of a 1H-cyclobuta[de] naphthalene-4,5-diylbis(diarylmethylium) species, a new C-C bond is formed between the C-alpha and C-ortho atoms of the two chromophores, which presents an unprecedented coupling pattern for the dimerization of two trityl units. By attaching an annulated cyclobutane ring at the opposite peri position of the naphthalene core, the distance between the C-alpha carbon atoms was elongated beyond the limit of sigma-bond formation through "scissor effects". The suppression of C-alpha-C-alpha bond formation, which would lead to hexaphenylethane-type compounds, is key to the first successful isolation of the alpha,o-adducts. The 5-diarylmethylene-6-triarylmethyl-1,3-cyclohexadiene unit in the alpha,o-adducts is stable, and isomerization of the cyclohexadiene unit into an aromatic system was not observed. The newly formed C-alpha-C-ortho bond was cleaved upon two-electron oxidation to regenerate the dicationic dye.
  • Takanori Suzuki, Takashi Takeda, Eisuke Ohta, Kazuhisa Wada, Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara
    CHEMICAL RECORD 15 (1) 280 - 294 1527-8999 2015/02 [Refereed][Not invited]
     
    10-Methylacridinium is a stable aromatic cation exhibiting yellow-orange color and strong green fluorescence (FL), and can be used as a versatile building block in constructing a wide variety of novel -electron systems. The dications with the two chromophores connected by a proper spacer undergo reversible dyrex (dynamic redox) behavior, and C-C bond formation/cleavage is accompanied by their redox reactions. The prototype is biphenyl-2,2-diylbis(10-methylacridinium), which exhibits electrochromic response with ON/OFF switching of FL during the reversible interconversion with the di(spiroacridan)-type electron donor. Slight structural alteration under the concept of MFMS (maximum function on the minimum skeleton) endowed the dyrex system with metal-binding or chiroptical properties, which could be modified by the redox reactions. Some of the di(spiroacridan) derivatives generated from bis(10-methylacridinium)s have extreme structural parameters, such as the greatest C-C bond length ever reported.
  • Yasuto Uchimura, Takashi Takeda, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki
    Angewandte Chemie Wiley-Blackwell 127 (13) 4082  2015/02 [Refereed][Not invited]
  • Yasuto Uchimura, Takashi Takeda, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki
    Angewandte Chemie International Edition Wiley-Blackwell 54 (13) 4125  2015/02 [Refereed][Not invited]
  • Yuto Sakano, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki
    CHEMICAL COMMUNICATIONS 51 (76) 14303 - 14305 1359-7345 2015 [Not refereed][Not invited]
     
    Two-proton or two-electron transfer of the title biphenolic dication proceeds nearly simultaneously to induce 2,6'/2',6- or 6,6'-bond formation to give dioxapyrene or dihydrophenanthrene derivatives, respectively, with vivid changes in color (halochromism and electrochromism).
  • Yuta Hirose, Kenshu Fujiwara, Takafumi Saito, Ryo Katoono, Takanori Suzuki
    HETEROCYCLES 91 (1) 76 - 103 0385-5414 2015/01 [Refereed][Not invited]
     
    The stereoselective synthesis of the A-ring of armatol A, a natural polycyclic ether triterpene from the red alga Chondria armata, was achieved in a non-biomimetic way. The synthesis employed Ireland-Claisen rearrangement of an ester, prepared from a bromo-substituted chiral building block, for the construction of C6 and C7 stereocenters and a relay ring-closing olefin metathesis for the seven-membered ring formation.
  • Yuto Sakano, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki
    CHEMICAL COMMUNICATIONS Royal Society of Chemistry ({RSC}) 51 (76) 14303 - 14305 1359-7345 2015 [Refereed][Not invited]
     
    Two-proton or two-electron transfer of the title biphenolic dication proceeds nearly simultaneously to induce 2,6'/2',6- or 6,6'-bond formation to give dioxapyrene or dihydrophenanthrene derivatives, respectively, with vivid changes in color (halochromism and electrochromism).
  • Yusuke Ishigaki, Satoshige Yoshida, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Fukushima, Takanori Suzuki
    HETEROCYCLES 90 (1) 126 - 135 0385-5414 2015/01 [Refereed][Not invited]
     
    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.
  • Ryo Katoono, Shunsuke Kawai, Kenshu Fujiwara, Takanori Suzuki
    CHEMICAL SCIENCE 6 (11) 6592 - 6600 2041-6520 2015 [Refereed][Not invited]
     
    We describe a quantitative analysis of the complexation-induced inversion of a screw-sense preference based on a conformationally dynamic double-helix structure in a macrocycle. The macrocycle is composed of two twisting units (terephthalamide), which are spaced by two strands (1,3-bis(phenylethynyl)benzene), and is designed to generate a double-helix structure through twisting about a C-2 axis in a conrotatory manner. The attachment of chiral auxiliaries to the twisting units induces a helical preference for a particular sense of (M)- or (P)-helicity through the intramolecular transmission of chirality to dynamic double helices. The twisting unit can also act as a binding site for capturing a guest molecule, and, in a complexed state, the preferred screw sense of the dynamic double-helix structure is reversed to exhibit the contrary preference. We quantitatively monitored the complexation-induced inversion of the screw-sense preference using H-1 NMR spectroscopy, which enabled us to observe independently two species with (M)- or (P)-helicity in both the absence and presence of a guest molecule. Inversion of the screw-sense preference was induced upon complexation with an achiral guest as well as a chiral guest.
  • Yusuke Ishigaki, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki
    HETEROCYCLES 90 (1) 136 - 143 0385-5414 2015/01 [Refereed][Not invited]
     
    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.
  • Yusuke Ishigaki, Satoshige Yoshida, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Fukushima, Takanori Suzuki
    HETEROCYCLES 90 (1) 126 - 135 0385-5414 2015/01 [Refereed][Not invited]
     
    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.
  • Yuta Hirose, Kenshu Fujiwara, Takafumi Saito, Ryo Katoono, Takanori Suzuki
    HETEROCYCLES 91 (1) 76 - 103 0385-5414 2015/01 [Refereed][Not invited]
     
    The stereoselective synthesis of the A-ring of armatol A, a natural polycyclic ether triterpene from the red alga Chondria armata, was achieved in a non-biomimetic way. The synthesis employed Ireland-Claisen rearrangement of an ester, prepared from a bromo-substituted chiral building block, for the construction of C6 and C7 stereocenters and a relay ring-closing olefin metathesis for the seven-membered ring formation.
  • Ryo Katoono, Shunsuke Kawai, Kenshu Fujiwara, Takanori Suzuki
    CHEMICAL SCIENCE 6 (11) 6592 - 6600 2041-6520 2015 [Refereed][Not invited]
     
    We describe a quantitative analysis of the complexation-induced inversion of a screw-sense preference based on a conformationally dynamic double-helix structure in a macrocycle. The macrocycle is composed of two twisting units (terephthalamide), which are spaced by two strands (1,3-bis(phenylethynyl)benzene), and is designed to generate a double-helix structure through twisting about a C-2 axis in a conrotatory manner. The attachment of chiral auxiliaries to the twisting units induces a helical preference for a particular sense of (M)- or (P)-helicity through the intramolecular transmission of chirality to dynamic double helices. The twisting unit can also act as a binding site for capturing a guest molecule, and, in a complexed state, the preferred screw sense of the dynamic double-helix structure is reversed to exhibit the contrary preference. We quantitatively monitored the complexation-induced inversion of the screw-sense preference using H-1 NMR spectroscopy, which enabled us to observe independently two species with (M)- or (P)-helicity in both the absence and presence of a guest molecule. Inversion of the screw-sense preference was induced upon complexation with an achiral guest as well as a chiral guest.
  • Yusuke Ishigaki, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki
    HETEROCYCLES 90 (1) 136 - 143 0385-5414 2015/01 [Refereed][Not invited]
     
    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.
  • Ryo Katoono, Keiichi Kusaka, Kenshu Fujiwara, Takanori Suzuki
    CHEMISTRY-AN ASIAN JOURNAL 9 (11) 3182 - 3187 1861-4728 2014/11 [Not refereed][Not invited]
     
    Dynamic helicity in a folded macrocycle and control of the helical preference are described. We designed macrocycle 1 with a dual mode of folding through the integration of two flexible units that are arranged twice to form a cyclic structure. As a folding unit, we used a terephthalamide skeleton and a Z-shaped hydrocarbon: the former acted as a control unit to induce a preference of a particular sense of dynamic helicity and the latter was just a spacer. A terephthalamide unit provided a binding site for capturing a ditopic hydrogen-bonding guest when it adopted helically folded syn forms (M/P). Thus, only the terephthalamide unit controlled the helical sense of dynamic helicity in a folded macrocycle through the supramolecular transmission of chirality upon complexation with a chiral ditopic guest. In addition, chirality on a host could also contribute to the control of the helical preference in a folded macrocycle, which led to exceptionally enhanced chiroptical signals.
  • Ryo Katoono, Keiichi Kusaka, Kenshu Fujiwara, Takanori Suzuki
    CHEMISTRY-AN ASIAN JOURNAL 9 (11) 3182 - 3187 1861-4728 2014/11 [Refereed][Not invited]
     
    Dynamic helicity in a folded macrocycle and control of the helical preference are described. We designed macrocycle 1 with a dual mode of folding through the integration of two flexible units that are arranged twice to form a cyclic structure. As a folding unit, we used a terephthalamide skeleton and a Z-shaped hydrocarbon: the former acted as a control unit to induce a preference of a particular sense of dynamic helicity and the latter was just a spacer. A terephthalamide unit provided a binding site for capturing a ditopic hydrogen-bonding guest when it adopted helically folded syn forms (M/P). Thus, only the terephthalamide unit controlled the helical sense of dynamic helicity in a folded macrocycle through the supramolecular transmission of chirality upon complexation with a chiral ditopic guest. In addition, chirality on a host could also contribute to the control of the helical preference in a folded macrocycle, which led to exceptionally enhanced chiroptical signals.
  • Ryo Katoono, Yuki Tanaka, Kenshu Fujiwara, Takanori Suzuki
    JOURNAL OF ORGANIC CHEMISTRY 79 (21) 10218 - 10225 0022-3263 2014/11 [Refereed][Not invited]
     
    A foldable cyclic oligomer 1 consisting of three terephthalamide units spaced with a 3-fold o-phenylene unit presented a dynamic pair of enantiomeric forms through molecular folding, to which the external chirality on a ditopic guest [(S,S)-2 or (R,R)-2] was supramolecularly transferred to prefer a particular sense of dynamic helicity [(M,M)-/(P,P)-1 and (M,M,P)-/(P,P,M)-1]. In the macrocycle, the terephthalamide units acted as exotopic binding sites to fold into helical forms upon complexation. The internal chirality associated with a host [(R,R,R,R,R,R)-1b] had no preference in a helical sense in the absence of a guest. Instead, the internal chirality was responsible for the signal modulation that it was cooperatively or competitively transferred in response to the external chirality on a guest (S,S)-2 or (R,R)-2. During the diastereomeric complexation, a particular sense of dynamic helicity was favored due to cooperative transmission of chirality when the helical preference was matched between the host and guest. Alternatively, the host complexed with an antipodal guest underwent a drastic change in conformation upon a change in temperature.
  • Takanori Suzuki, Yuto Sakano, Yusuke Tokimizu, Youhei Miura, Ryo Katoono, Kenshu Fujiwara, Naoki Yoshioka, Nobutaka Fujii, Hiroaki Ohno
    CHEMISTRY-AN ASIAN JOURNAL 9 (7) 1841 - 1846 1861-4728 2014/07 [Refereed][Not invited]
     
    Electron-donating dihydrobenzindolocarbazoles (BICs) 1a-c, which adopt planar disk-shaped geometries, were prepared by gold(I)-catalyzed cyclization as a key step. Due to the presence of a 1,4-phenylenediamine (PD) moiety in the framework, they undergo reversible one-electron oxidation to the corresponding Wurster's Blue (WB)-type species that exhibits NIR absorptions up to lambda=1200 nm. In the case of the N,N'-dimethyl derivative, cation radical 1c(+center dot) is stable enough to be isolated as a salt and Xray analysis indicated paraquinoid-type bond alternation in the WB core unit, whereas the bond lengths in the peripheral benzene rings are identical to those in the neutral donor. Upon electrochemical interconversion, the redox pairs of 1a-c and 1a-c(+center dot) exhibited an electrochromic response in the UV/Vis/NIR region, which was accompanied by a drastic change in the fluorescence spectrum because only neutral donors 1a-c are highly emissive (Phi(F): 0.7-0.8).
  • Yuto Sakano, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki
    CHEMISTRY LETTERS 43 (7) 1143 - 1145 0366-7022 2014/07 [Refereed][Not invited]
     
    Tetrakis(4-methoxyphenyl)anthraquinodimethane 1(b) with a bent geometry undergoes reversible redox interconversion with twisted dication 1(t)(2+) exhibiting a vivid change in color (electrochromism) accompanied by a drastic structural change. Electrochemical oxidation of bianthraquinodimethane 2(b) with a doubly bent structure to bianthrylidene-type twisted dication 2(t)(2+) proceeded smoothly, whereas the reverse conversion was less effective because 2(t)(2 center dot) generated upon reduction of 2(t)(2+) is a long-lived species to undergo side reactions.
  • 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 0366-7022 2014/07 [Refereed][Not invited]
     
    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.
  • Takashi Takeda, Yasuto Uchimura, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki
    ChemInform Wiley-Blackwell 45 (30) no  2014/07 [Refereed][Not invited]
  • Takanori Suzuki, Yusuke Kuroda, Kazuhisa Wada, Yuto Sakano, Ryo Katoono, Kenshu Fujiwara, Fumitoshi Kakiuchi, Takanori Fukushima
    CHEMISTRY LETTERS 43 (6) 887 - 889 0366-7022 2014/06 [Refereed][Not invited]
     
    Upon electrochemical oxidation of configurationally stable (M)-4,5-dimethyl-9,10-dihydrophenanthrene attached with two spiroacridan units at the C9 and C10 positions [(M)-1c], a three-way-output response by UV vis, FL, and CD spectra was realized via clean conversion to the corresponding bond-dissociated dication (R-ax)-2c(2+). Similar gradual changes were induced upon standing of an aerated MeCN solution of (M)-1c after the addition of CF3CO2H because the elongated C9 C10 bond was also cleaved by oxidative protonolysis to give (R-ax)-2c(2+).
  • Takanori Suzuki, Yuto Sakano, Yusuke Tokimizu, Youhei Miura, Ryo Katoono, Kenshu Fujiwara, Naoki Yoshioka, Nobutaka Fujii, Hiroaki Ohno
    Chem. Asian J. Wiley-Blackwell 9 (7) 1967  2014/06 [Refereed][Not invited]
  • Keiji Tanino, Takumasa Yamada, Fumihiko Yoshimura, Takanori Suzuki
    CHEMISTRY LETTERS 43 (5) 607 - 609 0366-7022 2014/05 [Refereed][Not invited]
     
    A series of 4-cyanoazulene derivatives 1-5 were synthesized from 4-cyanohexahydroazulen-l-one, which was efficiently obtained by the annulation of the seven-membered ring on the cyclopentenone skeleton via the divinylcyclopropane rearrangement. This synthetic protocol is also effective in preparing 1,1'-bi(4-cyanoazulene) (6) and its p-phenylene-extended derivative 7, which undergo multistage redox reactions exhibiting electrochemical amphotericity.
  • Takanori Suzuki, Yuto Sakano, Tomohiro Iwai, Shinichi Iwashita, Youhei Miura, Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara, Yasushi Tsuji, Takanori Fukushima
    PURE AND APPLIED CHEMISTRY 86 (4) 507 - 516 0033-4545 2014/04 [Refereed][Not invited]
     
    Electron-donating 1,1,4,4-tetraarylbutadiene is a representative electrochromic dye, and the same chromophore can be found in 9,10-bis(diarylmethylene)-9,10-dihydrophenanthrene (dibenzo-oQD) albeit in a fixed s-cis geometry. Unlike thermodynamically unstable 7,7,8,8-tetraaryl-o-quinodimethane, spontaneous electrocyclization is prohibited by dibenzo-annulation. Several derivatives of dibenzo-oQD were successfully generated despite highly strained geometry caused by steric hindrance between the bulky diarylmethylene units. Their precursors are phenanthrene-9,10-diyl bis(diarylmethylium) dyes (PDM2+) stabilized by four electron-donating alkoxy groups. The redox pairs of dibenzo-oQD/PDM2+ exhibit vivid change in color upon redox interconversion (electrochromism). Both dibenzo-oQD and PDM2+ adopt a helical conformation, whose configuration is unstable. When a chiral alkoxy substituent is attached on each of the aryl groups, the point chirality is successfully transmitted to helicity of PDM2+. Resulting diastereomeric biasing is the key for dibenzo-oQD/PDM2+ to exhibit the two-way-output response (e.g., UV-vis and CD). In addition, much more strained quinodimethane derivatives, 1,2-bis(diarylmethylene) acenaphthene and 1,16-diaryldibenzo[b, n] perylene, were also generated from the dicationic precursors, demonstrating that the reductive transformation can serve as a useful protocol to generate severely deformed pi-conjugated systems.
  • Kenshu Fujiwara, Yuki Suzuki, Nao Koseki, Yu-ichi Aki, Yuta Kikuchi, Shun-ichi Murata, Fuyuki Yamamoto, Mariko Kawamura, Toshio Norikura, Hajime Matsue, Akio Murai, Ryo Katoono, Hidetoshi Kawai, Takanori Suzuki
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 53 (3) 780 - 784 1433-7851 2014/01 [Refereed][Not invited]
     
    Pectenotoxin-2 (PTX2) is a shellfish toxin and has a non-anomeric spiroacetal, which is not stabilized by an anomeric effect. The selective construction of the non-anomeric spiroacetal has been a major problem in the synthesis of PTX2. Described herein is the stereoselective total synthesis of PTX2 via the isomerization of anomeric spiroacetal pectenotoxin-2b (PTX2b). The synthesis of PTX2b was achieved by a simple process including sulfone-mediated assembly of spirocyclic and bicyclic acetals and subsequent macrocyclization by ring-closing olefin metathesis. Finally, the selective construction of PTX2 was accomplished by the early termination of a dynamic transition process to equilibrium in the acid-catalyzed isomerization of anomeric PTX2b. [6,6]-Spiroacetal pectenotoxin-2c (PTX2c) was also synthesized from PTX2b. The cytotoxicity assay of the synthetic compounds against HepG2 and Caco2 cancer cells showed a potency of the order: PTX2 >> PTX2b > PTX2c.
  • Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki
    CHEMICAL COMMUNICATIONS 50 (41) 5438 - 5440 1359-7345 2014 [Refereed][Not invited]
     
    A tristerephthalamide host exhibited two helical geometries with (M)- and (P)- helicity, respectively, in terms of the twisting direction of a two-layer structure, and the helical preference switched upon complexation with a ditopic guest. In both uncomplexed and complexed states, the intramolecular transmission of chirality was responsible for the control of helicity.
  • Takanori Suzuki, Yasuto Uchimura, Fumika Nagasawa, Takashi Takeda, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Kei Murakoshi, Takanori Fukushima, Aiichiro Nagaki, Jun-ichi Yoshida
    CHEMISTRY LETTERS 43 (1) 86 - 88 0366-7022 2014/01 [Refereed][Not invited]
     
    Low-temperature X-ray analyses on several pseudopolymorphs (solvate crystals) revealed that the C-1-C-2 bond length of the highly congested title molecule can adopt quite different values [1.700(6)-1.739(6)angstrom]. Such an unusual observation indicates that the ultralong covalent bond is endowed with "expandability," thus the prestrained bond can be elongated or shortened very easily accompanied by only a minute change in energy, which can be compensated by intermolecular perturbation in the crystal.
  • Ryo Katoono, Keiichi Kusaka, Shunsuke Kawai, Yuki Tanaka, Keisuke Hanada, Tatsuo Nehira, Kenshu Fujiwara, Takanori Suzuki
    ORGANIC & BIOMOLECULAR CHEMISTRY 12 (47) 9532 - 9538 1477-0520 2014 [Not refereed][Not invited]
     
    We designed hexakis(phenylethynyl) benzene derivatives with a tertiary amide group on each blade to achieve a helically biased propeller arrangement through the complexation-induced intramolecular transmission of point chirality. A hydrogen-bonding ditopic guest was captured at two amide groups, and thus could pair two neighboring blades to form a supramolecular cyclic structure, in which an auxiliary chiral group associated with a blade acted as a chiral handle to control the helical bias, while the chiral auxiliary did not exert any helical influence on the dynamic helicity in the absence of a guest due to the high flexibility of each blade.
  • Takashi Takeda, Yasuto Uchimura, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki
    CHEMICAL COMMUNICATIONS 50 (30) 3924 - 3927 1359-7345 2014 [Refereed][Not invited]
     
    Due to purely steric effects of acridine units, acenaphthylene-1,2-diyldi(9-acridine) has a long C=C bond [1.3789(19) angstrom] while maintaining its sp(2) hybridized nature and bond order.
  • Kazuhisa Wada, Yuna Chiba, Takashi Takeda, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki
    HETEROCYCLES 88 (2) 945 - 952 0385-5414 2014/01 [Refereed][Not invited]
     
    The configuration of helical dicationic dyes 2(2+) with a dihydrodibenzoxepinone unit is stable, whereas the corresponding neutral electron donors 1 with a tetrahydrophenanthroxepinone skeleton easily undergo ring-flip. Thanks to their electrochemical bistability, electron exchange between 1 and 2(2+) is prohibited. Thus, the above electrochromic pairs 1/2(2+) can serve as new members of less well-explored redox-based chiral-memory units.
  • Kazuhisa Wada, Yuna Chiba, Takashi Takeda, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki
    HETEROCYCLES 88 (2) 945 - 952 0385-5414 2014/01 [Refereed][Not invited]
     
    The configuration of helical dicationic dyes 2(2+) with a dihydrodibenzoxepinone unit is stable, whereas the corresponding neutral electron donors 1 with a tetrahydrophenanthroxepinone skeleton easily undergo ring-flip. Thanks to their electrochemical bistability, electron exchange between 1 and 2(2+) is prohibited. Thus, the above electrochromic pairs 1/2(2+) can serve as new members of less well-explored redox-based chiral-memory units.
  • Ryo Katoono, Hidetoshi Kawai, Masakazu Ohkita, Kenshu Fujiwara, Takanori Suzuki
    Chemical Communications 49 (88) 10352 - 10354 1359-7345 2013/11/14 [Refereed][Not invited]
     
    Propeller-shaped dynamic helicity was generated in a hexakis(phenylethynyl) benzene framework that preferred a particular sense to afford a strong CD signal, which was realized by the cooperative transmission of point chiralities upon complexation with a chiral guest through a threefold binding site presented by a syn-formed terephthalamide. © 2013 The Royal Society of Chemistry.
  • Kenshu Fujiwara, Yuki Suzuki, Nao Koseki, Yu-ichi Aki, Yuta Kikuchi, Shun-ichi Murata, Fuyuki Yamamoto, Mariko Kawamura, Toshio Norikura, Hajime Matsue, Akio Murai, Ryo Katoono, Hidetoshi Kawai, Takanori Suzuki
    Angewandte Chemie Wiley-Blackwell 126 (3) 799  2013/11 [Refereed][Not invited]
  • Toshiyuki Hamura, Ryosuke Nakayama, Keisuke Hanada, Yuto Sakano, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki
    CHEMISTRY LETTERS 42 (10) 1244 - 1246 0366-7022 2013/10 [Refereed][Not invited]
     
    1,3-Bis[4-(dimethylamino)phenyl]isobenzofuran (1a) and a derivative were efficiently prepared through a sequence of reactions in a single batch reactor (time integration). The o-quinodimethane-type pi-conjugation in 1a was confirmed by bond alternation determined by a low-temperature X-ray analysis. Brightly colored heterocycle 1a undergoes reversible two-stage one-electron oxidation, and electrolysis of 1a induces a vivid change in UV-vis-NIR. absorptions exhibiting several isosbestic points (electrochromism).
  • Kazuhisa Wada, Takashi Takeda, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki
    CHEMISTRY LETTERS 42 (10) 1194 - 1196 0366-7022 2013/10 [Refereed][Not invited]
     
    By attaching bulky substituents at the bay region of di(spiroacridan)-substituted dihydrophenanthrene la, the prestrained C-9-C-10 bond in the dihydrophenanthrene (DHP) skeleton of le le is expanded from 1.634(2) to 1.649(3)-1.652(6)angstrom, which demonstrates the bond expansion through remote steric effects. Twisting deformation of the DHP skeleton is the key to transfer the steric bulkiness from the C-4/C-5 positions to cause the additional strain in the C-9-C-10 bond.
  • Takanori Suzuki, Yuulci Hoshiyama, Kazuhisa Wada, Yusuke Ishigaki, Youhei Miura, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Fukushima
    CHEMISTRY LETTERS 42 (9) 1004 - 1006 0366-7022 2013/09 [Refereed][Not invited]
     
    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.
  • Takanori Suzuki, Yusuke Toldmizu, Yuto Sakano, Ryo Katoono, Kenshu Fujiwara, Saori Naoe, Nobutaka Fujii, Hiroaki Ohno
    CHEMISTRY LETTERS 42 (9) 1001 - 1003 0366-7022 2013/09 [Refereed][Not invited]
     
    Through gold(I)-catalyzed cascade cyclization as a key step, the title electron donor was prepared, which adopts a planar geometry, as confirmed by an X-ray analysis. Due to 1,4-phenylenediamine moiety incorporated in the framework, it undergoes reversible one-electron oxidation. Upon electrolysis, it exhibited an electrochromic response in the UV-vis-NIR region, which was accompanied by a drastic change in the fluorescence spectrum since only the neutral donor is highly fluorescent.
  • Takashi Takeda, Yasuto Uchimura, Hidetoshi Kawai, Ryo Katoono, Kenshu Fujiwara, Takanori Suzuki
    CHEMISTRY LETTERS 42 (9) 954 - 962 0366-7022 2013/09 [Refereed][Not invited]
     
    Over the past few decades, many studies have been conducted on ultralong C-C bonds (bond length greater than 1.7 angstrom). This highlight review discusses the molecular design of ultralong C-C bonds and their bonding properties, especially their "expandability." In particular, the ultralong C-C bonds in tetraarylpyracene derivatives can change in length by adopting a slightly different conformation in the crystalline state. This expandability of ultralong C-C bonds could be due to the smaller decrease in bond energy at a longer interatomic distance (>1.7 angstrom). This interesting property can be applied to stimulus-responsive materials, as illustrated in the thermochromism of a bis(methylacridan)-substituted pyracene crystal, since the thermally induced change in bond-length modifies the HOMO-LUMO gap.
  • Naoto Kinashi, Kenshu Fujiwara, Takayuki Tsunoda, Ryo Katoono, Hidetoshi Kawai, Takanori Suzuki
    TETRAHEDRON LETTERS Elsevier {BV} 54 (34) 4564 - 4567 0040-4039 2013/08 [Refereed][Not invited]
     
    A method for the stereoselective construction of the C8'-O-C6" ether of nigricanoside-A, an antimitotic natural product from the green alga Avrainvillea nigricans, has been developed based on chirality-transferring Ireland-Claisen rearrangement. The method was successfully applied to the synthesis of simple models for the C20 lipid chain/galactosyl glycerol segment of the natural product. (C) 2013 Elsevier Ltd. All rights reserved.
  • Takanori Suzuki, Hitomi Tamaoki, Ryo Katoono, Kenshu Fujiwara, Junji Ichikawa, Takanori Fukushima
    CHEMISTRY LETTERS Chemical Society of Japan 42 (7) 703 - 705 0366-7022 2013/07 [Refereed][Not invited]
     
    Octafluorobiphenyl-2,2'-diylbis(diarylmethylium) dye 2a(2+) prepared from 1,2-dibromotetrafluorobenzene is interconvertible with colorless dihydrophenanthrene donor la. By the SNAr reactions of la with acetylides, pi-extended analogues 1b and 1c were obtained. Their electrochromic behavior is accompanied by a drastic absorption change not only in the visible but also UV region, because the torsion angle of the biaryl unit is modified upon redox reactions.
  • Takanori Suzuki, Takuma Kuroda, Hitomi Tamaoki, Sho Higasa, Ryo Katoono, Kenshu Fujiwara, Takanori Fukushima, Hidetoshi Yamada
    CHEMISTRY LETTERS 42 (7) 706 - 708 0366-7022 2013/07 [Refereed][Not invited]
     
    Upon oxidation of the title heterocycles with dimethylamino groups, elemental sulfur is extruded to form dicationic dyes, which regenerate the heterocycles by the reaction with Na2S. The electrolysis of the heterocycles induces a drastic change in UV-vis spectrum exhibiting several isosbestic points. The bay-region substituents enhance configurational stability, so the optically pure heterocycle can be obtained in terms of helicity of one-handedness, and its chromism is accompanied by a large chiroptical response as detected by CD spectroscopy.
  • Hidetoshi Kawai, Tatsuya Utamura, Erina Motoi, Tomoko Takahashi, Hiroyoshi Sugino, Manabu Tamura, Masakazu Ohkita, Kenshu Fujiwara, Takao Saito, Takashi Tsuji, Takanori Suzuki
    Chemistry - A European Journal 19 (14) 4513 - 4524 0947-6539 2013/04/02 [Not refereed][Not invited]
     
    The macrocyclization of 2,6-diethynyl hydrindacenes (1) with functional groups at mutually perpendicular positions results in the formation of novel macrocycles which, as a result of the hindered rotation of the hydrindacene units, possess directionally persistent peripheral functionalities. The two hydrindacene units in the dimer macrocycle (2) have been shown to interact electronically through their respective butadiyne moieties, whereas the trimer macrocycle (3) demonstrates a moderate degree of geometrical flexibility as a result of the five-membered hydrindacene rings. In addition, these trimer macrocycles contain a central cavity suitably sized for the inclusion of various solvent molecules. These new macrocycles can be further modified by introducing π-conjugated side groups, such as styryl and thienyl groups, as well as by attaching a variety of peripheral ester groups. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • Keisuke Nogoshi, Daisuke Domon, Kenshu Fujiwara, Natsumi Kawamura, Ryo Katoono, Hidetoshi Kawai, Takanori Suzuki
    TETRAHEDRON LETTERS Elsevier {BV} 54 (7) 676 - 680 0040-4039 2013/02 [Refereed][Not invited]
     
    The EF-ring of ciguatoxin 3C, a marine toxin from the dinoflagellate Gambierdiscus toxicus, was stereoselectively synthesized by iterative use of a cyclic ether formation process based on chirality-transferring Ireland-Claisen rearrangement and ring-closing olefin metathesis. (c) 2012 Elsevier Ltd. All rights reserved.
  • Takanori Suzuki, Yuto Sakano, Tomohiro Iwai, Shinichi Iwashita, Youhei Miura, Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara, Yasushi Tsuji, Takanori Fukushima
    CHEMISTRY-A EUROPEAN JOURNAL Wiley-Blackwell 19 (1) 117 - 123 0947-6539 2013/01 [Refereed][Not invited]
     
    When two benzene rings are fused to a tetraaryl-o-quinodimethane skeleton, sterically hindered helical molecules 1 acquire a high thermo-dynamic stability. Because the tetraarylbutadiene subunit contains electrondonating alkoxy groups, 1 undergo reversible two-electron oxidation to 2(2+), which can be isolated as deeply colored stable salts. Intramolecular transfer of the point chirality (e. g., sec-butyl) on the aryl groups to helicity induces a diastereomeric preference in dications 2b(2+) and 2c(2+), which represents an efficient method for enhancing circular-dichroism signals. Thus, those redox pairs can serve as new electrochiroptical response systems. X-ray analysis of dication 2(2+) revealed pi-pi stacking interaction of the diarylmethylium moities, which is also present in solution. The stacking geometry is the key contributor to the chirosolvatochromic response.
  • Daisuke Domon, Kenshu Fujiwara, Natsumi Kawamura, Ryo Katoono, Hidetoshi Kawai, Takanori Suzuki
    Natural Product Communications 8 (7) 929 - 934 1934-578X 2013 [Not refereed][Not invited]
     
    A new variant of fused cyclic ether synthesis based on Ireland-Claisen rearrangement and ring-closing olefin metathesis (RCM) was developed. The Ireland- Claisen rearrangement of a (Z)-3-alkoxyprop-2-en-1-yl glycolate ester having a cyclic ether on the oxygen at C3 of the (Z)-prop-2-en-1-yl group stereoselectively produced an anti-α,β-dialkoxyester, which was successfully transformed to a fused bicyclic ether via a reaction sequence including RCM.
  • Youhei Miura, Hiroshi Chiba, Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara, Shuichi Suzuki, Keiji Okada, Takanori Suzuki
    TETRAHEDRON LETTERS 53 (48) 6561 - 6564 0040-4039 2012/11 [Refereed][Not invited]
     
    Upon the one-electron reduction of N-methylquinoxalino[2,3-b]quinoxaliniums 2, neutral radicals 1 without any bulky protecting groups were generated and isolated as stable solids, which exhibit electric conductivity (sigma = 10(-7) 10(-9) S cm(-1)) as a single-component organic material due to high electrochemical amphotericity (Delta E = ca. 0.9 V). (C) 2012 Elsevier Ltd. All rights reserved.
  • Hiroyoshi Sugino, Hidetoshi Kawai, Takeshi Umehara, Kenshu Fujiwara, Takanori Suzuki
    CHEMISTRY-A EUROPEAN JOURNAL 18 (43) 13722 - 13732 0947-6539 2012/10 [Refereed][Not invited]
     
    Imine-bridged rotaxanes are a new type of rotaxane in which the axle and macrocyclic ring are connected by imine bonds. We have previously reported that in imine-bridged rotaxane 5, the shuttling motion of the macrocycle could be controlled by changing the temperature. In this study, we investigated how the axle and macrocycle structures affect the construction of the imine-bridged rotaxane as well as the dynamic equilibrium between imine-bridged rotaxane 5 and [2]rotaxane 7 by using various combinations of axles (1?A,B), macrocycles (2?ae), and side-stations (XYL and TEG). In the threading process, the flexibility of the macrocycle and the substituent groups at the para position of the aniline moieties affect the preparation of the threaded imines. The size of the imine-bridging station and the macrocyclic tether affects the hydrolysis of the imine bonds under acidic conditions.
  • Kenshu Fujiwara, Takuto Sato, Yusuke Sano, Toshio Norikura, Ryo Katoono, Takanori Suzuki, Hajime Matsue
    JOURNAL OF ORGANIC CHEMISTRY American Chemical Society ({ACS}) 77 (11) 5161 - 5166 0022-3263 2012/06 [Refereed][Not invited]
     
    The first total synthesis of natural, unsymmetrical 2',3'-diacyloxy-p-terphenyls, thelephantin O (1) and terrestrins C and D (2 and 3, respectively), was achieved via a practical route which was also applicable to the synthesis of the symmetrical diesters vialinin A/terrestrin A. (4) and terrestrin B (5). Compounds 1-5 exhibited cytotoxicity against cancer cells (HepG2 and Caco2) with IC50 values of 13.6-26.7 mu mol/L.
  • 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 0366-7022 2012/05 [Refereed][Not invited]
     
    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.
  • Hiroyoshi Sugino, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Suzuki
    CHEMISTRY LETTERS 41 (1) 79 - 81 0366-7022 2012/01 [Refereed][Not invited]
     
    Condensation reactions of macrocyclic diamines 1 and cyclohexane-1,4-dicarbaldehydes 2 with the substituents at 1,4-positions gave a series of macrocage molecules that can be considered molecular gyroscopes. The gyro-rotational behavior of the cyclohexane rotor is largely affected by the degree of steric requirement of the substituents, and isolation of syn-isomer suggests stepwise motion in the macrocages attached with bulky substituents on the rotor.
  • Takanori Suzuki, Hitomi Tamaoki, Kazuhisa Wada, Ryo Katoono, Tatsuo Nehira, Hidetoshi Kawai, Kenshu Fujiwara
    CHEMICAL COMMUNICATIONS Royal Society of Chemistry ({RSC}) 48 (22) 2812 - 2814 1359-7345 2012 [Refereed][Not invited]
     
    The ratio of the easily interconverting rotational isomers of biphenyl-2,2'-diylbis[bis(4-dimethylaminophenyl)methylium] (R)/(S)-1a(2+) can be biased to prefer an R configuration upon 1 : 1 complexation with gamma-cyclodextrin in water. Through the reaction with Na2S, the preference of 1a(2+) @gamma-CyD for an axial chirality of R can be fixed as the M-helicity of dihydrothiepin 2.
  • Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Suzuki
    Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry 70 (6) 640 - 650 0037-9980 2012 [Not refereed][Not invited]
     
    This article describes the chirality sensing systems based on changes in conformation of dynamic terephthalamide hosts from a nonhelical form to a helical form with biasing to prefer one handedness upon complexation with a chiral guest through supramolecular transmission of chirality. The syn form is endowed with the ability to capture a ditopic guest through hydrogen bonds at the amide carbonyls thus in a complexed state, a strong CD signal is produced thanks to a helical conformation induced by the conformational change and a biased handedness. Attachment of chirality to the terephthalamide host itself leads to an intrinsic preference in the sense of dynamic helicity in a helical syn form. Cooperative transmission of chiralities within the host and from the guest enables to further design an advanced sensing system with stereospecific chiroptical modulation, based on a stereospecific change in conformation of the chiral dynamic host upon complexation with a pair of enantiomeric guests.
  • Yusuke Ishigaki, Takanori Suzuki, Jun-ichi Nishida, Aiichiro Nagaki, Naofumi Takabayashi, Hidetoshi Kawai, Kenshu Fujiwara, Jun-ichi Yoshida
    MATERIALS 4 (11) 1906 - 1926 1996-1944 2011/11 [Refereed][Not invited]
     
    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].
  • Kenshu Fujiwara, Yuki Suzuki, Nao Koseki, Shun-ichi Murata, Akio Murai, Hidetoshi Kawai, Takanori Suzuki
    TETRAHEDRON LETTERS Elsevier {BV} 52 (43) 5589 - 5592 0040-4039 2011/10 [Refereed][Not invited]
     
    The C8-C20 segment of pectenotoxin-2 was efficiently synthesized in 16% overall yield in 22 steps from L-malic acid via an improved route. (C) 2011 Elsevier Ltd. All rights reserved.
  • Youhei Miura, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Suzuki
    CHEMISTRY LETTERS 40 (9) 975 - 977 0366-7022 2011/09 [Refereed][Not invited]
     
    Due to the high-lying HOMO of the substituents and the low-lying LUMO inherited by the heterocyclic skeleton, the title quinoxalinoquinoxalines 1 exhibit absorption bands which extend to the NIR region, whereas the dihydro derivatives 2 are less colored but emit strong green fluorescence. Thus, the present pairs can serve as novel redox dyes for drastic spectral changes.
  • Masakazu Ohkita, Ayataka Endo, Kimihiro Sumiya, Hajime Nakanotani, Takanori Suzuki, Chihaya Adachi
    JOURNAL OF LUMINESCENCE Elsevier {BV} 131 (7) 1520 - 1524 0022-2313 2011/07 [Refereed][Not invited]
     
    4,4'-bis(N-carbazolyl)tolan (BCT) and 4,4'-bis[N-(3,6-di-t-butyl)carbazolyl]tolan (BCT-t-Bu) were synthesized as pi-expanded analogs of 4,4'-bis(N-carbazolyl)biphenyl. Their photophysical characteristics both in solution and films were thoroughly investigated. Interestingly, the phosphorescence spectrum of BCT was significantly medium-dependent, and the emission maximum was red-shifted by 131 nm from 489 nm in solution at 77 K to 620 nm in a deposited film at 5 K. suggesting the presence of strong intermolecular interactions in the film. BCT and BCT-t-Bu were found to be useful as host materials for fluorescence-based organic light emitting diodes (OLEDs). However, their low triplet energy levels in films negated their potential to act as hosts in phosphorescence-based OLEDs. (C) 2011 Elsevier B.V. All rights reserved.
  • Atsushi Takemura, Yasushi Katagiri, Kenshu Fujiwara, Hidetoshi Kawai, Takanori Suzuki
    TETRAHEDRON LETTERS Elsevier {BV} 52 (11) 1222 - 1224 0040-4039 2011/03 [Refereed][Not invited]
     
    The synthesis of the C22-C37 segment of prorocentin, isolated from the dinoflagellate Prorocentrum lima, was achieved. Because the relative stereochemical relationship between C26 and other stereocenters (C28/C31/C32 established as R*/R*/R*) in the C22-C37 region of natural prorocentin has not yet been determined, both epimers at C26 of the C22-C37 segment were selectively constructed. The synthesis was based on a 5-exo epoxide ring opening reaction to form an oxolane (E-ring). Brown asymmetric methallylation to install the C26-stereocenter, acryloylation of the resulting alcohol, and ring-closing olefin metathesis to establish the Z-olefin at C23/C24. (C) 2011 Elsevier Ltd. All rights reserved.
  • Takanori Suzuki, Takashi Takeda, Yasuyo Yoshimoto, Takayuki Nagasu, Hidetoshi Kawai, Kenshu Fujiwara
    ChemInform Wiley-Blackwell 41 (39) no  2010/09 [Refereed][Not invited]
  • Kenshu Fujiwara, Yuta Hirose, Daisuke Sato, Hidetoshi Kawai, Takanori Suzuki
    TETRAHEDRON LETTERS 51 (32) 4263 - 4266 0040-4039 2010/08 [Refereed][Not invited]
     
    Armatol F, isolated from the red alga Chondria armata as a polyether triterpene, has a solitary oxepane (A-ring) and a fused tricyclic ether moiety (BCD-ring). The A-ring features a rare cis-relationship between the hydroxy group at the quaternary carbon C6 and the carbon chain at C7. As part of our program toward the total synthesis of armatol F, a new stereoselective method for the construction of the C6 and C7 stereocenters has been developed based on chirality-transferring Ireland-Claisen rearrangement. The A-ring skeleton has also been synthesized from the rearrangement product by a process including ring-closing olefin metathesis. (C) 2010 Elsevier Ltd. All rights reserved.
  • Kenshu Fujiwara, Keita Tanaka, Yasushi Katagiri, Hidetoshi Kawai, Takanori Suzuki
    TETRAHEDRON LETTERS 51 (34) 4543 - 4546 0040-4039 2010/08 [Refereed][Not invited]
     
    Armatol F, isolated from the red alga Chondria armata as a polyether triterpene, has a fused tricyclic ether moiety (BCD-ring) with an unusual cis ring junction at C18-C19 between the C- and D-rings. En route to the total synthesis of armatol F, the stereoselective construction of the C18 and C19 stereocenters by Ireland-Claisen rearrangement and the formation of the C-ring by relay ring-closing olefin metathesis were established through the synthesis of monocyclic (C-ring) and bicyclic (BC-ring) model compounds. (C) 2010 Elsevier Ltd. All rights reserved.
  • Takanori Suzuki, Youhei Miura, Tatsuo Nehira, Hidetoshi Kawai, Kenshu Fujiwara
    CHEMISTRY LETTERS 39 (7) 695 - 697 0366-7022 2010/07 [Refereed][Not invited]
     
    Not only the configuration at the C5 and C6 stereocenters but also the intra/intermoleculer hydrogen-bonding mode are determinant for the sense of mobile helicity of the dihydrophenanthroline unit in the title diols in solution. Thus, drastic changes in chiroptical signals are induced through conformational switching of 1 upon addition of protic solvent and/or acid.
  • Takanori Suzuki, Takashi Takeda, Yasuyo Yoshimoto, Takayuki Nagasu, Hidetoshi Kawai, Kenshu Fujiwara
    PURE AND APPLIED CHEMISTRY Walter de Gruyter {GmbH} 82 (4) 1033 - 1044 0033-4545 2010/04 [Refereed][Not invited]
     
    A series of title carbocations was generated and isolated as stable salts. X-ray analyses revealed a preference for an unsymmetric structure in which the bridging hydrogen is localized on one of the two triarylmethane units. NMR spectroscopy showed a similar preference in solution. The bridging hydrogen fluctuates between the two chromophores in solution, and the energy barrier for the H shift is linearly correlated with the C center dot center dot center dot C(+) separation determined by X-ray. According to an extrapolation, the energy barrier should decrease when the C center dot center dot center dot C(+) separation is less than 2.7 angstrom, which suggests a new model for isolable pure organic species with a three-center two-electron bond.
  • Takanori Suzuki, Takashi Takeda, Yasuyo Yoshimoto, Takayuki Nagasu, Hidetoshi Kawai, Kenshu Fujiwara
    PURE AND APPLIED CHEMISTRY Walter de Gruyter {GmbH} 82 (4) 1033 - 1044 0033-4545 2010/04 [Refereed][Not invited]
     
    A series of title carbocations was generated and isolated as stable salts. X-ray analyses revealed a preference for an unsymmetric structure in which the bridging hydrogen is localized on one of the two triarylmethane units. NMR spectroscopy showed a similar preference in solution. The bridging hydrogen fluctuates between the two chromophores in solution, and the energy barrier for the H shift is linearly correlated with the C center dot center dot center dot C(+) separation determined by X-ray. According to an extrapolation, the energy barrier should decrease when the C center dot center dot center dot C(+) separation is less than 2.7 angstrom, which suggests a new model for isolable pure organic species with a three-center two-electron bond.
  • Tatsuo Nehira, Yasuyo Yoshimoto, Kazuhisa Wada, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Suzuki
    CHEMISTRY LETTERS 39 (3) 165 - 167 0366-7022 2010/03 [Not refereed][Not invited]
     
    Acridine-based novel fluorophores 1/2 with a helical dihydrodibenzoxepin/azepine skeleton exhibit halochromic response upon addition of Bronsted acid in CH2Cl2, thus giving UV-vis and fluorescence spectral changes. By using the optically resolved species [(M)-1/2], circular dichroism (CD) and fluorescence detected-CD (FDCD) signals were also changed drastically, thus demonstrating four-way-output response thanks to configurational stability of helicity and efficient exciton coupling.
  • Takanori Suzuki, Yasuyo Yoshimoto, Kazuhisa Wada, Takashi Takeda, Hidetoshi Kawai, Kenshu Fujiware
    HETEROCYCLES 80 (1) 149 - 155 0385-5414 2010/01 [Not refereed][Not invited]
     
    The title dication (1(2+)) was generated by oxidative bond cleavage of a 4,5-dihydoropyrene derivative (2) with two spiro(10-methylacridan) units. Despite the skewed deformation of the arylene spacer, two cationic chromophores in 1(2+) are forced to face in a proximity with a very short interatomic separation of 2.98(1) angstrom between carbenium centers (X-ray), which makes the LUMO level of 1 much lower than that of biphenyl-2,2'-diyl-type dication (3(2+)).
  • Takanori Suzuki, Kazuhisa Wada, Yusuke Ishigaki, Yasuyo Yoshimoto, Eisuke Ohta, Hidetoshi Kawai, Kenshu Fujiwara
    CHEMICAL COMMUNICATIONS 46 (23) 4100 - 4102 1359-7345 2010 [Refereed][Not invited]
     
    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+)).
  • Takanori Suzuki, Yasuyo Yoshimoto, Kazuhisa Wada, Takashi Takeda, Hidetoshi Kawai, Kenshu Fujiware
    HETEROCYCLES 80 (1) 149 - 155 0385-5414 2010/01 [Refereed][Not invited]
     
    The title dication (1(2+)) was generated by oxidative bond cleavage of a 4,5-dihydoropyrene derivative (2) with two spiro(10-methylacridan) units. Despite the skewed deformation of the arylene spacer, two cationic chromophores in 1(2+) are forced to face in a proximity with a very short interatomic separation of 2.98(1) angstrom between carbenium centers (X-ray), which makes the LUMO level of 1 much lower than that of biphenyl-2,2'-diyl-type dication (3(2+)).
  • Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Suzuki
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 131 (46) 16896 - 16904 0002-7863 2009/11 [Refereed][Not invited]
     
    The secondary terephthalamide host la-H attached to four aryl blades was prepared from tetrabromide 2a by Suzuki-Miyaura coupling and undergoes a conformational change from a nonpropeller anti-form to a propeller-shaped syn-form upon complexation with ditopic guests such as p-xylylenediammonium derivatives (RR)/(SS)-3 (chirality generation). Through transmission of the point chiralities attached on the nitrogens in the chiral guests to the mobile helicity in 1a-H, the propeller-shaped host in the complex is biased to prefer a particular handedness (chirality biasing). While chiral guests with simple point chiralities such as (R,R)/(S,S)-3 exhibit only very weak CD activity, complexation with the dynamic propeller host 1 a-H results in much stronger chiroptical signals (chiroptical enhancement). The chirality generation-chirality biasing protocol was successfully applied to a neurotransmitter, (-)-phenylephrine 4, acting as a chiral ditopic guest. When the chiral auxiliaries are attached to the host as in (R,R)-1b-H, complexation with (S,S)-3 causes CD enhancement but not with (R,R)-3, due to chiral recognition.
  • Takanori Suzuki, Shintaro Mikuni, Yusuke Ishigaki, Hiroki Higuchi, Hidetoshi Kawai, Kenshu Fujiwara
    ChemInform Wiley-Blackwell 40 (44) 2009/11 [Refereed][Not invited]
  • Takashi Takeda, Hidetoshi Kawai, Rainer Herges, Eva Mucke, Yoshitaka Sawai, Kei Murakoshi, Kenshu Fujiwara, Takanori Suzuki
    TETRAHEDRON LETTERS 50 (26) 3693 - 3697 0040-4039 2009/07 [Refereed][Not invited]
     
    There is evidence that the crystalline-state thermochromic behavior of dispiropyracene acr-1 with an ultralong C-C bond [1.791(3) angstrom at 413 K, 1.771(3) angstrom at 93K] might be due to thermal generation of a bond-dissociated triplet diradical. The C(1)-C(2) bond lengths (d) in the newly prepared 1,1,2,2-tetraarylpyracenes 1a-e [1.717(4)-1.761(4) angstrom at 113/123/153 K] are also much larger than the standard value for C(sp(3))-C(sp(3)) (1.54 angstrom). The fact that there is no correlation between d and the radical-stabilizing parameter (sigma(center dot)) provides evidence that there is no contribution from a crystallographic artifact caused by contamination of the diradical in the crystal of 1 at room temperature or below. Further indication for the covalent nature of the ultralong C-C bond in tetraphenylpyracene 1c was attained by Raman spectroscopy, showing the far Fed-shifted C(1)-C(2) Stretching vibration (638 cm(-1)) and by the theoretical prediction of very large vertical singlet-triplet energy gap (58.3 kcal mol(-1) at the UB3LYP/6-31G* level). However, at elevated temperatures bond dissociation might occur forming a triplet diradical. (C) 2009 Elsevier Ltd. All rights reserved.
  • Takanori Suzuki, Youhei Miura, Ryuuichi Tamaki, Hidetoshi Kawai, Kenshu Fujiwara
    CHEMISTRY LETTERS 38 (7) 670 - 671 0366-7022 2009/07 [Refereed][Not invited]
     
    A series of X-ray analyses on the newly prepared title molecules have revealed that the one-dimensional rod-like structures are commonly present in the crystals of trans-dihydrophenan-throlinediols. The architecture is of interest from the viewpoint of supramolecular chirality because homochiral diol molecules with the same sense of helicity are connected in a head-to-tail fashion by a pair of N center dot center dot center dot H-O hydrogen bonds.
  • Takanori Suzuki, Shintaro Mikuni, Yusuke Ishigaki, Hiroki Higuchi, Hidetoshi Kawai, Kenshu Fujiwara
    CHEMISTRY LETTERS 38 (7) 748 - 749 0366-7022 2009/07 [Refereed][Not invited]
     
    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.
  • Kata Mlinarić-Majerski, Helena Dodziuk, Tatyana N. Gribanova, Vladimir I. Minkin, Ruslan M. Minyaev, Takanori Suzuki, Takashi Takeda, Hidetoshi Kawai, Kenshu Fujiwara, Vladimir Y. Lee, Akira Sekiguchi
    Strained Hydrocarbons: Beyond the van-t Hoff and Le Bel Hypothesis 33 - 102 2009/05/08 [Refereed][Not invited]
  • Kenshu Fujiwara, Natsumi Kawamura, Hidetoshi Kawai, Takanori Suzuki
    TETRAHEDRON LETTERS Elsevier {BV} 50 (11) 1236 - 1239 0040-4039 2009/03 [Refereed][Not invited]
     
    The asymmetric synthesis of an acyclic anti-beta-alkoxy ether was achieved by the Ireland-Claisen rearrangement of Z-3-aikoxy-2-propenyl glycolate ester, prepared from Garner's aldehyde, a glycolic acid derivative, and ethynyl N,N-diisopropylcarbamate. The resulting acyclic ether was facilely converted to seven- and eight-membered cyclic ethers via processes involving ring-closing olefin metatheses. (C) 2009 Elsevier Ltd. All rights reserved.
  • Strained Hydrocarbon (Chap 2.5 Ultralong C-C Bond)
    Wiley-VCH 2009 [Not refereed][Not invited]
  • Takanori Suzuki, Yasuyo Yoshimoto, Takashi Takeda, Hidetoshi Kawai, Kenshu Fujiwara
    CHEMISTRY-A EUROPEAN JOURNAL 15 (9) 2210 - 2216 0947-6539 2009 [Refereed][Not invited]
     
    The isolation and low-temperature X-ray analyses of a series of intramolecular methylacridan-methylacridinium complexes have been achieved. The two chromophores are in close proximity due to an arylene spacer, such as a phenanthrene-4,5-diyl or biphenyl-2.2'-diyl unit. These bridged carbocations prefer the C-H localized structure both in solution and in the solid state. The bridging hydrogen atom undergoes a facile intramolecular hydride shift from one carbon atom to another in solution, and the energy barrier is linearly correlated with the intramolecular C center dot center dot center dot C(+) distance in the solid state geometry, as determined by single-crystal X-ray analyses. By extrapolation from the data, the delocalized three-center bond of [C-H-C](+) would be formed when the C center dot center dot center dot C(+) distance is less than 2.7 angstrom.
  • Takanori Suzuki, Yusuke Ishigaki, Tomohiro Iwai, Hidetoshi Kawai, Kenshu Fujiwara, Hiroshi Ikeda, Yusuke Kano, Kazuhiko Mizuno
    CHEMISTRY-A EUROPEAN JOURNAL 15 (37) 9434 - 9441 0947-6539 2009 [Refereed][Not invited]
     
    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.
  • Takeshi Umehara, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Suzuki
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 130 (42) 13981 - 13988 0002-7863 2008/10 [Refereed][Not invited]
     
    The construction and switching properties of a novel class of molecular shuttles 1 with imine-bonding stations for macrocyclic diamine parts are reported. Studies on dithioacetalized [2]rotaxane 4 with two hydrogen-bonding stations and a masked imine-bonding station showed that protonation of a macrocycle increases the shuttling barrier due to hydrogen-bond formation between NH(3)(+) groups and the TEG-stations. Hydrolysis of the imine-bonds of the imine-bridged molecular shuttles 1b,c with TEG-stations could exclusively give the [2]rotaxane 2b,c center dot 2H(2+), With the macrocycle hydrogen-bonded with the TEG-station. In contrast, la without TEG-stations gave an equilibrated mixture of la, monoimine 3a center dot H(+), and 2a center dot 2H(2+) under similar acidic hydrolytic conditions. The equilibrium between 1b,c and 2b,c center dot 2H(2+) to control the position of the macrocycle could be successfully switched to either side by applying acidic hydrolytic or dehydrating conditions. Furthermore, the equilibrium was largely biased to [2]rotaxane 2b,c center dot 2H(2+) under acidic hydrolytic conditions and could be reversed in favor of bis-imine 1b,c just by heating. This is a successful example of a molecular shuttle exhibiting entropy-driven translational isomerism with remarkable positional discrimination. An examination of thermodynamic parameters showed that imine-bond hydrolyses and the formation of hydrogen bonds between the macrocycle and the station are thermodynamically matched processes, because both processes are enthalpically favored and accompanied by a loss of entropy. The combination of imine-bonding and hydrogen-bonding station in a rotaxane system is the key to realizing the clear entropy-driven positional switching of the macrocycle observed.
  • Hidetoshi Kawai, Takashi Takeda, Kenshu Fujiwara, Makoto Wakeshima, Yukio Hinatsu, Takanori Suzuki
    Chem. Eur. J. Wiley-Blackwell 14 (19) 000  2008/06 [Refereed][Not invited]
  • Takahiro Katagiri, Kenshu Fujiwara, Hidetoshi Kawai, Takanori Suzuki
    Tetrahedron Letters Elsevier {BV} 49 (20) 000  2008/05 [Refereed][Not invited]
  • Takanori Suzuki, Takashi Takeda, Hidetoshi Kawai, Kenshu Fujiwara
    PURE AND APPLIED CHEMISTRY 80 (3) 547 - 553 0033-4545 2008/03 [Refereed][Not invited]
     
    The longer C-C bond than the standard (1.54 angstrom) is so weakened that it is cleaved easily, as found in the parent hexaphenylethane (HPE). However, the compounds with an ultralong C-C bond (1.75 angstrom) can be isolated as stable solids when the bond-dissociated species does not undergo any reactions other than bond reformation. This is the central point in designing the highly strained HPEs, which were obtained by two-electron reduction of the corresponding dications. Steric repulsion of "front strain" is the major factor to expand the central C-C bond of HPEs. During the detailed examination of the ultralong C-C bond, the authors discovered the intriguing phenomenon of "expandability": the C-C bond length can be altered over a wide range by applying only a small amount of energy (1 kcal mol(-1)) supplied by crystal packing force. This observation indicates that the much longer C-C bond than the shortest nonbonded contact (1.80 angstrom) will be realized under the rational molecular design concept.
  • Tetrahedron Lett., 49, 233-237 (2008). 000  2008 [Not refereed][Not invited]
  • Ryo Katoono, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Suzuki
    CHEMICAL COMMUNICATIONS (40) 4906 - 4908 1359-7345 2008 [Refereed][Not invited]
     
    The syn-atropisomers of the title bis(tertiary amide)s were designed as six-bladed molecular propellers based on the ''directing effects'' of amide dipoles; the helicity of the propeller is biased to prefer one handedness upon the attachment of point chirality to the amide nitrogens to attain stronger circular-dichroism activity than for the non-propeller-shaped anti-isomers.
  • Takanorl Suzuki, Kenji Ohta, Tatsuo Nehira, Hiroki Higuchi, Eisuke Ohta, Hidetoshi Kawai, Kenshu Fujiwara
    TETRAHEDRON LETTERS 49 (5) 772 - 776 0040-4039 2008/01 [Refereed][Not invited]
     
    Upon the attachment of N-(R)-2-phenylethylamide moieties to the acridinium units of the title dication, intramolecular hydrogen bonds induce a diastereomeric preference in terms of axial chirality (70% de at -40 degrees C in CH(2)Cl(2)). Thus, external stimuli induce not only UV-vis and fluorescence spectra changes but also changes in the CD and fluorescence-detected CD (FDCD) spectra, realizing unprecedented four-way-output molecular response systems. (C) 2007 Elsevier Ltd. All rights reserved.
  • Eisuke Ohta, Tatsuo Nehira, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Suzuki
    TETRAHEDRON LETTERS 49 (5) 777 - 781 0040-4039 2008/01 [Refereed][Not invited]
     
    Presence or absence of electron-accepting dye chromophores is the key function for ON/OFF switching of fluorescence from the dihydrodibenzo[c,g]phenanthrene skeleton in 2(2+)/3. The helical fluorophore in 2(2+) could be generated stereoselectively upon electrolysis of binaphthylic donor 1 through intramolecular chirality transmission. Huge chiroptical signals are easily detected by circular dichroism, (CD) and fluorescence-detected CD (FDCD) techniques to realize novel four-way-output response. (C) 2007 Elsevier Ltd. All rights reserved.
  • Akiyoshi Goto, Kenshu Fujiwara, Ayako Kawai, Hidetoshi Kawai, Takanori Suzuki
    ORGANIC LETTERS 9 (26) 5373 - 5376 1523-7060 2007/12 [Refereed][Not invited]
     
    The EF-ring segment of ciguatoxin 3C, a causative toxin of ciguatera fish poisoning, was synthesized in three major steps: 1,4-addition for the C20O-C27 bond connection, chirality transferring anti selective [2,3]-Wittig rearrangement for the construction of the anti-2-hydroxyalkyl ether part, and ring-closing olefin metathesis for the F-ring formation.
  • Kenshu Fujiwara, Jota Naka, Takahiro Katagiri, Daisuke Sato, Hidetoshi Kawai, Takanori Suzuki
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 80 (6) 1173 - 1186 0009-2673 2007/06 [Not refereed][Not invited]
     
    The synthesis of the A- and F-rings of goniodomin A (1), which is a stereochemically unidentified antifungal agent isolated from dinoflagellate Alexandrium hiranoi, was performed to determine of the relative stereochemistry of these parts. The relative stereochemistry of the A- and F-rings was first deduced from Murakami's NMR data, and model compounds corresponding to these parts were then synthesized. The synthetic A-ring model, of which the structure was established by X-ray crystallographic analysis, showed good agreement with the natural A-ring on the basis of J and NOE behavior in the H-1 NMR spectroscopy. The chemical shifts in H-1 and C-13 NMR specta and J(32-OH-H33) of the synthetic F-ring model having a 33S,34R configuration also agreed with those of the F-ring of 1. Thus, the relative stereochemistry of the A- and F-rings of 1 was elucidated.
  • Kenshu Fujiwara, Yu-ichi Aki, Fuyuki Yamamoto, Mariko Kawamura, Masanori Kobayashi, Azusa Okano, Daisuke Awakura, Shunsuke Shiga, Akio Murai, Hidetoshi Kawai, Takanori Suzuki
    TETRAHEDRON LETTERS 48 (26) 4523 - 4527 0040-4039 2007/06 [Refereed][Not invited]
     
    In this study, we synthesized the C8-C20 and C21-C30 segments of the diarrhetic shellfish toxin pectenotoxin 2. The C8C20 segment was assembled from a phosphonate corresponding to the C8-C15 segment (prepared from L-malic acid in 19 steps) and an aldehyde corresponding to the C16-C20 segment (synthesized from 3-methyl-3-butenol in nine steps) by a twelve-step process including the Homer-Wadsworth-Emmons reaction, regio- and stereoselective reduction of the resulting enone, diastereoselective epoxidation, and 5-exo epoxide cleavage forming the C-ring. The C21-C30 segment was constructed in 13 steps from (S)-glycidol via a route involving E-ring formation by 5-exo epoxide cleavage and stereoselective methylation at C27 by the Evans method. (c) 2007 Elsevier Ltd. All rights reserved.
  • Takanori Suzuki, Tomohiro Iwai, Eisuke Ohta, Hidetoshi Kawai, Kenshu Fujiwara
    TETRAHEDRON LETTERS 48 (20) 3599 - 3603 0040-4039 2007/05 [Refereed][Not invited]
     
    Huge CD amplitude (A = +538) was attained by diastereomeric preference (50% de) for the title dication with two bis[4(R)-sec-butoxyphenyl]methylium units in benzene at 23 degrees C. Intramolecular pi-pi stacking is the origin for effective transmission of point chirality to axial chirality to attain the chiroptical enhancement of 400-times. Thanks to the strong CD signaling, chiroptical changes upon electrolysis could be readily detected, thus realizing a new class of clectrochiroptical response systems. Chiroptical properties could also be modified by solvent polarity. (C) 2007 Elsevier Ltd. All rights reserved.
  • Takanori Suzuki, Ryuuichi Tamaki, Eisuke Ohta, Takashi Takeda, Hidetoshi Kawai, Kenshu Fujiwara, Masako Kato
    TETRAHEDRON LETTERS 48 (22) 3823 - 3827 0040-4039 2007/05 [Refereed][Not invited]
     
    The spiro-acridan/acridinium-based dynamic redox pair (1/2(2+)) transduces the electrochemical input into UV-vis and fluorescence spectra, whereas the 2,2 '-bipyridine units in I works as a bidentate ligand for metal ions. X-ray structural analyses of this redox pair and the corresponding Zn-complexes [1-ZnI2/2(2+)-Zn2+(OTf-)(4)] demonstrate drastic structural changes upon electron-transfer, thus metal binding properties are modified by redox reactions. (C) 2007 Elsevier Ltd. All rights reserved.
  • Takanori Suzuki, Eisuke Ohta, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Fukushima
    SYNLETT 2007 (6) 851 - 869 0936-5214 2007/04 [Refereed][Not invited]
     
    'Dynamic redox systems' is the name given to a certain class of compounds that can be reversibly converted into the corresponding charged species accompanied by C-C bond formation/cleavage upon electron transfer. This account details the two major motifs (hexaphenylethane derivatives and butane-1,4-diyl dications) that have been developed in the principal author's group.
  • Shinichi Iwashita, Takanori Suzuki
    ChemInform Wiley-Blackwell 38 (8) 2007/02 [Refereed][Not invited]
  • Takashi Takeda, Hidetoshi Kawai, Kenshu Fujiwara, Takanori Suzuki
    CHEMISTRY-A EUROPEAN JOURNAL 13 (28) 7915 - 7925 0947-6539 2007 [Refereed][Not invited]
     
    Isolation and low-temperature X-ray analyses of intramolecular triarylmethane-triarylmethylium complexes with a naphthalene-1,8-diyl-type skeleton have been achieved. These bridged cations prefer a C-H localized structure both in solution and in the solid state. The bridging hydrogen undergoes a facile intramolecular 1,5-hydride shift from one carbon to another in solution. The C-H delocalized geometry is suggested to be the transition-state structure of the degenerate rearrangement. Charge-transfer interaction from the triarylmethane to the triarylmethylium units is evident in the electronic spectra. This interaction stabilizes the present cations. Low reactivity toward Bronsted acids indicates that these species are not the reaction intermediates in the acid-assisted long-bond cleavage of 1, 1,2,2-tetraarylace-naphthene derivatives.
  • Takanori Suzuki, Shoko Tanaka, Hidetoshi Kawai, Kenshu Fujiwara
    CHEMISTRY-AN ASIAN JOURNAL 2 (1) 171 - 177 1861-4728 2007 [Refereed][Not invited]
     
    The title heterocyclic donors undergo reversible C-C bond formation/cleavage upon electron transfer (dynamic redox behavior). The helical sense in both neutral and cationic states is interconvertible by facile ring flipping. The pi-type asymmetric center on the azepine nitrogen atom induces a significant degree of diasteromeric preference, thus endowing strong CD activity based on exciton coupling. Chi-roptical properties could be modified not only by redox reactions but also by heat and protonation. The present redox pairs can serve as unprecedented three-way-input (e, H+, Delta) and two-way-Output (UV/Vis, CD) response systems.
  • Shinichi Iwashita, Takanori Suzuki
    J. Syn. Org. Chem., Jpn. The Society of Synthetic Organic Chemistry, Japan 64 (9) 958 - 968 0037-9980 2006/09/01 [Refereed][Not invited]
     
    Introduction of four aryl groups on the highly reactive o-quinodimethane (o-QDM) skeleton suppresses the intermolecular reactivities. Thus, the unimolecular isomerization through electro-cyclization is the major decomposition path for title molecules. Rational design can prevent thermal isomerization of Ar4-o-QDMs. A new general procedure to generate Ar4-o-QDM has been established here that includes two-electron reduction of the corresponding dications, whose reaction conditions no longer promote electrocyclization of Ar4-o-QDM. Several derivatives of Ar4-o-QDM with the dihydrophenanthrene, dibenzoperylene, or acenaphthene skeleton were isolated for the first time, and the details on their highly strained molecular structures were investigated by low-temperature X-ray analyses. Based on the reversible interconversion between Ar4-o-QDMs and the precursor dications, they represent a new class of electrochromic redox pairs.
  • Ayumi Takizawa, Kenshu Fujiwara, Eriko Doi, Akio Murai, Hidetoshi Kawai, Takanori Suzuki
    TETRAHEDRON 62 (31) 7408 - 7435 0040-4020 2006/07 [Refereed][Not invited]
     
    Convergent synthesis of the common FGHI-ring part (54) of ciguatoxins was achieved via the following key steps: (i) the Nozaki-Hiyama-Kishi reaction connecting the F-ring part (6) with the I-ring part (7); (ii) regio- and stereoselective epoxidation; (iii) the 6-exo-epoxide opening reaction forming simultaneously the H-ring and the quaternary asymmetric center at C30; (iv) inversion of the C29 stereocenter by a two-step oxidation/reduction process, where the successful inversion depended on proper management of the steric environment of the substrate; and (v) final reductive cyclization constructing the G-ring. (c) 2006 Elsevier Ltd. All rights reserved.
  • Hidetoshi Kawai, Takeshi Umehara, Kenshu Fujiwara, Takashi Tsuji, Takanori Suzuki
    Angew. Chem. Wiley-Blackwell 118 (26) 4387  2006/06 [Refereed][Not invited]
  • R Katoono, H Kawai, K Fujiwara, T Suzuki
    TETRAHEDRON LETTERS 47 (10) 1513 - 1518 0040-4039 2006/03 [Refereed][Not invited]
     
    Conformation of novel terephthalamide hosts 1 changes from anti to syn upon complexation with a bidentate guest (2 or 3). Chiral sense in the helical syn-form of the double-armed host molecules 1 is biased by the asymmetric centers on the chiral guest [(R,R)1(S,S)-2a], which can be detected by the drastic change in circular dichroism (CD) spectrum thanks to the exciton coupling of two chromophores ('arms') linked to the amide nitrogens. Asymmetric centers on the host molecule also exhibit preference for the twisting direction upon change in geometry from the anti- to syn-form. Thus, the achiral guests (2b or 3) can also be detected by modulation of CD spectrum upon complexation with the chiral host [(,R,R)-1a]. (c) 2006 Elsevier Ltd. All rights reserved.
  • Hidetoshi Kawai, Takeshi Umehara, Kenshu Fujiwara, Takashi Tsuji, Takanori Suzuki
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 45 (26) 4281 - 4286 1433-7851 2006 [Refereed][Not invited]
  • A Takizawa, K Fujiwara, E Doi, A Murai, H Kawai, T Suzuki
    TETRAHEDRON LETTERS 47 (5) 747 - 751 0040-4039 2006/01 [Refereed][Not invited]
     
    The common FGHI-ring part (2) of ciguatoxins has been synthesized from the F- and I-ring parts (6 and 5, respectively). The Nozaki-Hiyama-Kishi coupling of 6 with 5 followed by regio- and stereoselective epoxidation at C29 and C30 afforded an epoxide (4), which was transformed into a tricyclic compound (3) corresponding to the F-HI-ring part by 6-exo-epoxide opening and the subsequent inversion of the C29 stereocenter. Reductive cyclization of 3 forming the C31-O26 bond of the G-ring successfully produced 2. (c) 2005 Elsevier Ltd. All rights reserved.
  • T Suzuki, S Iwashita, T Yoshino, H Kawai, K Fujiwara, M Ohkita, T Tsuji, K Ono, M Takenaka
    TETRAHEDRON LETTERS 47 (4) 467 - 471 0040-4039 2006/01 [Refereed][Not invited]
     
    Severely deformed title quinodimethanes [1,2-bis(diarylmethylene)acenaphthenes] 1 have been designed and prepared as novel electrochromic materials, which can be reversibly interconverted with the deeply colored dicationic dyes 1(2+) with acenaphthylene-1,2-diyl skeleton. The X-ray analysis of 1 revealed that the inner two aryl groups are forced to overlap in proximity, which can account for the facile electrocyclization process to the isomer. By combination of reversible electrochemical transformation with irreversible isomerization process, the present system provides a prototype for novel molecular response systems equipped with the 'write-protect' option. (c) 2005 Elsevier Ltd. All rights reserved.
  • Daisuke Domon, Kenshu Fujiwara, Yuko Ohtaniuchi, Akihiro Takezawa, Sayaka Takeda, Hidekazu Kawasaki, Akio Murai, Hidethoshi Kawai, Takanori Suzuki
    ChemInform Wiley-Blackwell 37 (5) 2006/01 [Refereed][Not invited]
  • Kenshu Fujiwara, Saori Yoshimoto, Ayumi Takizawa, Shin-ichiro Souma, Hirofumi Mishima, Akio Murai, Hidetoshi Kawai, Takanori Suzuki
    ChemInform Wiley-Blackwell 37 (3) 2006/01 [Refereed][Not invited]
  • Daisuke Domon, Kenshu Fujiwara, Akio Murai, Hidethoshi Kawai, Takanori Suzuki
    ChemInform Wiley-Blackwell 37 (5) 2006/01 [Refereed][Not invited]
  • H Kawai, T Takeda, K Fujiwara, T Inabe, T Suzuki
    CRYSTAL GROWTH & DESIGN 5 (6) 2256 - 2260 1528-7483 2005/11 [Not refereed][Not invited]
     
    A large difference of 0.064(3) angstrom for a chemically equivalent C-sp(3) - C-sp(3) bond was observed among crystallographically independent molecules with different conformations (conformational isomorphs) of a hexaphenylethane derivative, dispiro[(10-methylacridan)-9,1'-pyracene-2',9"-(10-methylacridan)I (1): triclinic, P (1) over bar, a = 17.6990 angstrom, b = 18.1110 angstrom, c = 18.844(3) angstrom, alpha = 111.183(2)degrees, beta = 93.828(1)degrees, gamma = 102.130(2)degrees, V = 5438.5(14) angstrom(3), T = - 180 degrees C, Z = 8 (four independent molecules: A, N, B, and B'). While B and B' adopt the skewed conformation to reduce steric repulsion in 1, in other positions of the crystal, molecules A and X adopt the eclipsed conformation, which induces a much longer bond length [1.771(3) and 1.758(3) angstrom versus 1.712(2) and 1.707(2) angstrom].
  • D Domon, K Fujiwara, Y Ohtaniuchi, A Takezawa, S Takeda, H Kawasaki, A Murai, H Kawai, T Suzuki
    TETRAHEDRON LETTERS Elsevier {BV} 46 (48) 8279 - 8283 0040-4039 2005/11 [Refereed][Not invited]
     
    The C42-C52 part of ciguatoxin CTX3C (1) was synthesized from tri-O-acetyl D-glucal. The synthetic segment had a tetrahydropyran ring corresponding to the 'C49-reduced' L-ring of 1, designed to avoid side reactions due to acid-labile C49 acetal carbon during acidic reductive conditions planned in further synthesis toward 1. The vicinal dimethyl part at C47-C48 was constructed by a stepwise conjugate addition/methylation procedure. The C50-C52 unit was installed by Grignard addition of the C-3 unit followed by of the spirocyclic acetal. Stereoselective assembly of the C42-C44 part was achieved by Brown's asymmetric crotylboration. (c) 2005 Elsevier Ltd. All rights reserved.
  • D Domon, K Fujiwara, A Murai, H Kawai, T Suzuki
    TETRAHEDRON LETTERS 46 (48) 8285 - 8288 0040-4039 2005/11 [Refereed][Not invited]
     
    Convergent synthesis of the IJKLM-ring part (2) of ciguatoxin CTX3C has been achieved from the I-ring and the L-ring parts (4 and 5) in total eight steps in 27% overall yield. The carbanion derived from 4, stabilized by a dimethyldithioacetal S-oxide group, was readily reacted with aldehyde 5 to give an adduct, which was facilely transformed into the corresponding alpha,epsilon-dihydroxy ketone 3. The JK-ring formation from 3 under reductive conditions followed by oxidative M-ring cyclization efficiently led to the pentacyclic ether 2. Improved synthesis of 6, a synthetic intermediate for 4, was also established. (c) 2005 Elsevier Ltd. All rights reserved.
  • K Fujiwara, S Yoshimoto, A Takizawa, S Souma, H Mishima, A Murai, H Kawai, T Suzuki
    TETRAHEDRON LETTERS 46 (40) 6819 - 6822 0040-4039 2005/10 [Refereed][Not invited]
     
    Laurencin was efficiently synthesized from a C-glycoside derivative based on ring expansion of the oxane part of the starting compound into an eight-membered cyclic ether via a ring-cleavage/ring-closing olefin metathesis process, stereoselective introduction of a brotno group at C4, and convergent construction of the side-chain part using a lithiated enyne unit. (c) 2005 Elsevier Ltd. All rights reserved.
  • H Kawai, T Takeda, K Fujiwara, T Suzuki
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 127 (35) 12172 - 12173 0002-7863 2005/09 [Refereed][Not invited]
     
    The intramolecular triarylmethane-methylium complex with an averaged C2v-symmetry was successfully generated by N-methylation of the acridine-acridan hybrid. Theoretical calculation and VT-NMR analyses in solution indicate the unsymmetric geometry for the three-center bond, which was finally confirmed crystallographically. Significant degree of CT interaction is induced through the very short C-H⋯C+ contact. Copyright © 2005 American Chemical Society.
  • Atsushi Takemura, Kenshu Fujiwara, Ken Shimawaki, Akio Murai, Hidetoshi Kawai, Takanori Suzuki
    Tetrahedron Elsevier {BV} 61 (31) 7392  2005/08 [Refereed][Not invited]
  • T Suzuki, K Ichioka, H Higuchi, H Kawai, K Fujiwara, M Ohkita, T Tsuji, Y Takahashi
    JOURNAL OF ORGANIC CHEMISTRY 70 (14) 5592 - 5598 0022-3263 2005/07 [Refereed][Not invited]
     
    A series of butterfly-shaped tetracyanoanthraquinodimethanes (TCNAQs) with a chiral amide auxiliary 1a-f were prepared from the corresponding anthraquinones. They are stronger acceptors than the unsubstituted derivative and undergo one-wave two-electron reduction. They form weak electron-donor-acceptor (EDA) complexes with the title pinacol 2. Upon charge-transfer excitation of these complexes, dihydro-TCNAQs 3 and 1,8-dianisoylnaphthalene 4 were efficiently formed, the latter of which is the product of a retropinacol reaction via 2(+.). Partial enantiodifferentiation of rac-2 was realized during the photoreactions with 2-[(R)-1-phenylethylcarbamoyl]-TCNAQ la in CD3CN. Thus, optically active (S,S)-(+)-pinacol 2 (12.3% ee at 54% conversion; 21.5% ee at 70% conversion) was recovered from the photolyzates. This reaction represents a new and rare example of the pseudokinetic resolution of tert-alcohol accompanied by C-C bond fission. Significant differences in the association constants for the diastereomeric EDA complexes are responsible for the observed enantiodifferentiation.
  • K Fujiwara, A Goto, D Sato, H Kawai, T Suzuki
    TETRAHEDRON LETTERS Elsevier {BV} 46 (20) 3465 - 3468 0040-4039 2005/05 [Refereed][Not invited]
     
    A simple stereoselective synthesis of cis- and trans-2,3-disubstituted medium-sized cyclic ethers has been developed based on geometry-selective synthesis of 3-alkoxy-2-propenyl glycolate esters, Ireland-Claisen rearrangement of the glycolate esters, and ring-closing olefin metathesis. (c) 2005 Elsevier Ltd. All rights reserved.
  • Shinichi Iwashita, Eisuke Ohta, Hiroki Higuchi, Hidetoshi Kawai, Kenshu Fujiwara, Kazunori Ono, Masami Takenaka, Takanori Suzuki
    ChemInform Wiley-Blackwell 36 (10) 2005/03 [Refereed][Not invited]
  • R Katoono, H Kawai, K Fujiwara, T Suzuki
    CHEMICAL COMMUNICATIONS (41) 5154 - 5156 1359-7345 2005 [Refereed][Not invited]
     
    Upon complexation of a rectangular-shaped achiral macro-cyclic host with chiral guests, twisting deformation occurs to induce exciton-type bisignated CD, whereas a chiral rectangular host undergoes a similar structural change only with the matching enantiomer of a chiral guest.
  • E Ohta, H Higuchi, H Kawai, K Fujiwara, T Suzuki
    ORGANIC & BIOMOLECULAR CHEMISTRY 3 (16) 3024 - 3031 1477-0520 2005 [Not refereed][Not invited]
     
    Incorporation in the dihydro[ 5] helicene framework prevents deprotonation of the title dications by steric factors, thus allowing their isolation as deeply colored stable salts. Based on the reversible interconversion with the electron-donating binaphthylic diolefins, they constitute a new class of electrochromic systems, in which C-C bond making/breaking is accompanied by two-electron transfer. Optically pure (R)-binaphthylic donors are interconvertible with the 1,4-dications with the R,R-configuration. The very large molar ellipticity makes it possible for them to be used as electrochiroptical response systems, by which the electrochemical input is transduced into two spectral outputs, i.e. UV-Vis and circular dichroism. Structurally related push-pull-type bis(quinonemethide)s also exhibit a similar multi-output electrochemical response.
  • H Kawai, R Katoono, K Fujiwara, T Tsuji, T Suzuki
    CHEMISTRY-A EUROPEAN JOURNAL 11 (3) 815 - 824 0947-6539 2005/01 [Refereed][Not invited]
     
    The molecular recognition of catecholamines by hydrindacene-based receptors 1 and 2, as well as the durene-based receptor 3, and the guest-induced conformational changes are reported. These receptors selectively bind adrenaline and dopamine salts through the guests' ammonium group and 3-hydroxyl group on the aromatic ring. In the case of adrenaline, an additional hydrogen bond with a benzylic hydroxyl group is formed. In 2% CD3CN/CDCl3, the association constants are of the order of 10(4)m(-1), which is much larger than with guests without the 3-hydroxyl groups (10(3)m(-1)). The two amide groups of receptor 1 can rotate freely around the C-aromatic-C-amide bond, whereas the tert-amide in 2 changes between two stable conformations at a slow enough rate to allow detection by H-1 NMR spectroscopy. In the absence of a guest molecule, the syn-conformer is less stable than the anti-conformer. On complex formation with adrenaline, the syn-conformer becomes dominant due to an intramolecular dipole-reversal effect in addition to multipoint hydrogen bonding.
  • H Kawai, T Takeda, K Fujiwara, T Suzuki
    TETRAHEDRON LETTERS 45 (45) 8289 - 8293 0040-4039 2004/11 [Refereed][Not invited]
     
    The extremely long C-C bond [1.696(3) Angstrom] in the colorless dispiroacenaphthene-type hexaphenylethane is cleaved readily upon electrochemical transformation into the orange colored naphthalene-1,8-diylbis(acridinium), in which the two cationic units are forced to overlap in a face-to-face manner exhibiting the shortest C+...C+ interatomic contact of 2.927(7) Angstrom among the values ever reported. (C) 2004 Elsevier Ltd. All rights reserved.
  • T Suzuki, S Tanaka, H Higuchi, H Kawai, K Fujiwara
    TETRAHEDRON LETTERS 45 (46) 8563 - 8567 0040-4039 2004/11 [Refereed][Not invited]
     
    The long C-C bonds (1.614(2)-1.630(2) Angstrom) in newly prepared title donors 2-6 are cleaved upon two-electron oxidation to afford the bond-dissociated dicationic dyes 2(2+)-6(2+), whose electron affinities are stronger than the corresponding biphenyl-2,2'-diyl dications 1(2+) due to the spatial proximity of two xanthenylium units. Not only UV-vis but also fluorescence spectra changed drastically upon electrolysis since only colorless neutral donors are fluorescent. (C) 2004 Elsevier Ltd. All rights reserved.
  • R Katoono, H Kawai, K Fujiwara, T Suzuki
    TETRAHEDRON LETTERS 45 (46) 8455 - 8459 0040-4039 2004/11 [Refereed][Not invited]
     
    2,9-Diaza-1,10-dioxo[10]paracyclophanes were prepared in short steps from the terephthaloyl chlorides via the corresponding 4,6-diyne derivatives, and the amide groups on the bridge endow the skeleton with the guest-binding properties as demonstrated by complexation with adrenaline by hydrogen bonds. The chiral auxiliaries on the bridge induce diastereomeric preference in terms of the planar chirality for the octadehydro derivative with a rigid diyne unit in crystal. (C) 2004 Elsevier Ltd. All rights reserved.
  • A Takemura, K Fujiwara, A Murai, H Kawai, T Suzuki
    TETRAHEDRON LETTERS 45 (41) 7567 - 7571 0040-4039 2004/10 [Refereed][Not invited]
     
    A synthetic method for a branched ether system was developed. The method was based on Lewis-acid-promoted gamma-position selective reduction of a gamma-alkoxy beta,gamma-unsaturated alpha-silyloxy nitrile, prepared through a process including intermolecular hetero-Michael reaction of a 2-butynoate ester derivative with an alcohol. The method was efficiently applied to the synthesis of fused medium-ring ethers involving the EF-ring segment (2) of ciguatoxin (1). (C) 2004 Elsevier Ltd. All rights reserved.
  • Kenshu Fujiwara, Daisuke Sato, Manabu Watanabe, Hiroshi Morishita, Akio Murai, Hidetoshi Kawai, Takanori Suzuki
    ChemInform Wiley-Blackwell 35 (43) 2004/10 [Refereed][Not invited]
  • K Fujiwara, A Goto, D Sato, Y Ohtaniuchi, H Tanaka, A Murai, H Kawai, T Suzuki
    TETRAHEDRON LETTERS 45 (38) 7011 - 7014 0040-4039 2004/09 [Refereed][Not invited]
     
    Convergent synthesis of the ABCDE-ring part (2) of ciguatoxin CTX3C (1) has been achieved. A carbanion stabilized by a dimethyldithioacetal S-oxide group in the AB-ring part (4) readily reacted with an aldehyde group in the E-ring part (5). The resulting adduct was facilely converted to the corresponding beta,gamma-unsaturated alpha,epsilon-dihydroxy ketone (3). The subsequent reductive hydroxy-ketone-cyclization reactions constructed the CD-ring part efficiently. Thus, the ABCDE-ring part (2) was concisely synthesized in 10 steps in 11% overall yield from the AB-ring and the E-ring parts (4 and 5). (C) 2004 Elsevier Ltd. All rights reserved.
  • K Fujiwara, D Sato, M Watanabe, H Morishita, A Murai, H Kawai, T Suzuki
    TETRAHEDRON LETTERS 45 (27) 5243 - 5246 0040-4039 2004/06 [Refereed][Not invited]
     
    Concise construction of the trans-fused 7/7/6/6 tetracyclic ether part of hemibrevetoxin B (1) was achieved by a convergent strategy based on coupling reaction of an acyl anion equivalent, reductive cyclization of an alpha,epsilon-dihydroxyketone, and introduction of a methyl group at the central ring junction by the Nicolaou method. The resultant tetracyclic ether was transformed into the known intermediate, which was already converted to 1 by the Yamamoto group, thereby completing the formal total synthesis of 1. (C) 2004 Elsevier Ltd. All rights reserved.
  • H Kawai, T Nagasu, T Takeda, K Fujiwara, T Tsuji, M Ohkita, JI Nishida, T Suzuki
    TETRAHEDRON LETTERS 45 (23) 4553 - 4558 0040-4039 2004/05 [Refereed][Not invited]
     
    (8-Diarylmethyl-1-naphthyl)bis(4-dimethylaminophenyl)methyliums (aryl=C6H5, 4-IC6H4, and 4-MeOC6H4) were generated by hydride shift from (4-dimethylaminophenyl)methyl group to the diarylmethylium unit at peri-positions of naphthalene. Successful isolation and low-temperature X-ray analysis indicated that they are novel C-H bridged carbocations, which prefer the localized structure with a short contact of C-H... C+ rather than the delocalized one with a three-centered-two-electron bond of (C... H...C)+. (C) 2004 Elsevier Ltd. All rights reserved.
  • H Higuchi, K Ichioka, H Kawai, K Fujiwara, M Ohkita, T Tsuji, T Suzuki
    TETRAHEDRON LETTERS 45 (15) 3027 - 3030 0040-4039 2004/04 [Refereed][Not invited]
     
    The newly prepared tetracyanoanthraquinodimethane (TCNAQ) derivatives 1a,b with a chiral auxiliary are good electron acceptors and exhibit weak circular dichroism (CD) based on the absorption of TCNAQ. The twin-type electron acceptor 1c with two TCNAQ units shows larger ellipticity by exciton coupling. UV-vis, CD, and fluorescence spectra were changed drastically upon electrochemical reduction of 1c, which demonstrates the unprecedented three-way-output response system. (C) 2004 Elsevier Ltd. All rights reserved.
  • H Kawai, R Katoono, K Nishimura, S Matsuda, K Fujiwara, T Tsuji, T Suzuki
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY American Chemical Society ({ACS}) 126 (16) 5034 - 5035 0002-7863 2004/04 [Refereed][Not invited]
  • T Suzuki, S Miyanari, H Kawai, K Fujiwara, T Fukushima, T Miyashi, Y Yamashita
    TETRAHEDRON 60 (9) 1997 - 2003 0040-4020 2004/02 [Refereed][Not invited]
     
    The X-ray analyses of the title electron acceptors (1) revealed their butterfly-shaped deformed geometry, which is not affected by the pyridyl group attached at 2-position of the pyrazino-TCNNQ skeleton. Small differences between the first and second reduction potentials (ca. 0.1 V) in pyrazino-TCNNQs show that their anion radicals (1(-.)) are prone to disproportionate into the neutral (1) and dianionic (1(2-)) species. The thermodynamically unstable anion radical species based on the pyrazino-TCNNQ skeleton could be isolated as inner salts upon electrochemical reduction of the derivatives having an N-methylpyridinium moiety at 2-position (2(+)). The zwitterionic open-shell species (2) constitute a novel class of radicals that exhibit semiconducting behavior as a single component thanks to the high electrochemical amphotericity. (C) 2004 Elsevier Ltd. All rights reserved.
  • T Suzuki, M Saito, H Kawai, K Fujiwara, T Tsuji
    TETRAHEDRON LETTERS Elsevier {BV} 45 (2) 329 - 333 0040-4039 2004/01 [Refereed][Not invited]
     
    The title electron donors were prepared by the double condensation reactions of 2,2',3,3'-tetraamino-4,4'-bis(l-pyrrolidinyl)biphenyl with 1,2-diketones. They adopt twisted conformations in crystal, yet the reversible two-stage one-electron oxidation process suggests the planar geometries for the oxidized species. Depending on the nature of substituents on the pyrazine ring, this pi-system can be endowed additional features such as chiroptical properties or metal coordination ability. (C) 2003 Elsevier Ltd. All rights reserved.
  • S Iwashita, E Ohta, H Higuchi, H Kawai, K Fujiwara, K Ono, M Takanaka, T Suzuki
    CHEMICAL COMMUNICATIONS 10 (18) 2076 - 2077 1359-7345 2004 [Refereed][Not invited]
     
    Oxidative cyclization of 2,2'-bis(dianisylethenyl) biphenyl yielded the dicationic salt of phenanthrene-9,10-diylbis( dianisylmethylium), which in turn afforded the severely congested title molecule as the first stable tetraaryl-o-quinodimethane derivative upon reduction.
  • Masakazu Ohkita, Chihaya Adachi, Miki Kawano, Takanori Suzuki
    HETEROCYCLES Japan Institute of Heterocyclic Chemistry 63 (7) 1537  2004 [Refereed][Not invited]
  • M Ohkita, K Sano, K Ono, K Saito, T Suzuki, T Tsuji
    ORGANIC & BIOMOLECULAR CHEMISTRY 2 (17) 2421 - 2425 1477-0520 2004 [Refereed][Not invited]
     
    Kinetic stabilization of the o-quinoidal 3,4-benzotropone system was investigated. The parent 3,4-benzotropone 1 undergoes rapid [pi8+pi10] dimerization in fluid solution even at -78degreesC while triptycene-fused derivative 5 having a tert-butyl group at the C(6) position of the tropone moiety was found to be stable indefinitely under similar conditions. The relative importance of the triptycene moiety and the tert-butyl group in 5 for the kinetic stabilization was evaluated.
  • M Ohkita, K Sano, T Suzuki, T Tsuji, T Sato, H Niino
    ORGANIC & BIOMOLECULAR CHEMISTRY 2 (7) 1044 - 1050 1477-0520 2004 [Refereed][Not invited]
     
    pi-Extended o-quinoidal tropone derivatives, naphtho[2,3-c] tropone (3) and anthro[2,3-c] tropone (4), have been investigated theoretically as well as experimentally. The geometrical optimization of 3, 4, and related compounds at the B3LYP level employing 6-31G* basis set as well as the GIAO calculations at the RHF level employing the 6-31+G* basis set have been performed to evaluate the contributions of the polarized resonance forms to these molecules. The GIAO calculated NICS(1) values indicate that the aromaticities of the tropone rings of o-quinoidal 3 and 4 are significantly increased as compared with that of parent tropone (1) at the expense of the fused benzenoid rings, consistent with the significant electronic polarization of these molecules in the ground state. On the other hand, the fusion of a benzene or naphthalene ring to the 2,3- or 4,5-position of tropone leads to diminution of aromaticity in the resulting tropone moiety. Experimentally, irradiation of 6,7-(2', 3'-naphtho) bicyclo[3.2.0] hepta-3,6-dien-2-one (10) in a rigid glass at - 196 degreesC leads to the formation of 3, which exhibits a characteristic UV-Vis absorption extending to 700 nm and undergoes rapid [pi12 + pi14] dimerization upon thawing the glass. In contrast, 6,7-(2', 3'-anthro) bicyclo[3.2.0] hepta-3,6-dien-2-one (11) showed no sign of isomerization to 4 under the same reaction conditions.
  • J Ishihara, Y Ikuma, S Hatakeyama, T Suzuki, A Murai
    TETRAHEDRON 59 (51) 10287 - 10294 0040-4020 2003/12 [Refereed][Not invited]
     
    Azadirachtin is a C-seco, limonoid, derived from the neem tree. Previously, we reported the synthesis of the right and left segments of azadirachtin, in addition to the coupling reaction of the modeled ester utilizing Claisen rearrangement. Herein we report the transformation of the modeled rearrangement product into a tricyclic dihydrofuran, which would be expected to have bioactivity against insects. (C) 2003 Elsevier Ltd. All rights reserved.
  • T Suzuki, Y Tsubata, Y Obana, T Fukushima, T Miyashi, M Saito, H Kawai, K Fujiwara, K Akiyama
    TETRAHEDRON LETTERS 44 (43) 7881 - 7884 0040-4039 2003/10 [Not refereed][Not invited]
     
    The title electron donors 1 as well as their conjugate bases 2(-) undergo reversible two-stage one-electron oxidation. ESR analysis indicated the important contribution of zwitterionic structure for radicals 2(.). Bis(zwitterionic) but not quinoid structure was suggested for p-4, generated from the twin-type dianionic donor P-4(2-) with a p-phenylene spacer. (C) 2003 Elsevier Ltd. All rights reserved.
  • T Suzuki, A Migita, H Higuchi, H Kawai, K Fujiwara, T Tsuji
    TETRAHEDRON LETTERS Elsevier {BV} 44 (36) 6837 - 6840 0040-4039 2003/09 [Refereed][Not invited]
     
    The newly prepared title donor 1 has a very long C-C bond [1.635(2) Angstrom], which was readily cleaved upon oxidation to. give dication 2(2+) containing two 10-methylacridinium chromophores. Colorless donor 1 (E-ox +0.18 V) is non-fluorescent whereas orange dication 2(2+) (E-red -0.27 V) emits strong green fluorescence, so that, this pair can be considered as a novel redox switch for fluorescence with high electrochemical bistability. (C) 2003 Elsevier Ltd. All rights reserved.
  • T Suzuki, A Migita, H Higuchi, H Kawai, K Fujiwara, T Tsuji
    TETRAHEDRON LETTERS Elsevier {BV} 44 (36) 6837 - 6840 0040-4039 2003/09 [Refereed][Not invited]
     
    The newly prepared title donor 1 has a very long C-C bond [1.635(2) Angstrom], which was readily cleaved upon oxidation to. give dication 2(2+) containing two 10-methylacridinium chromophores. Colorless donor 1 (E-ox +0.18 V) is non-fluorescent whereas orange dication 2(2+) (E-red -0.27 V) emits strong green fluorescence, so that, this pair can be considered as a novel redox switch for fluorescence with high electrochemical bistability. (C) 2003 Elsevier Ltd. All rights reserved.
  • H Higuchi, E Ohta, H Kawai, K Fujiwara, T Tsuji, T Suzuki
    JOURNAL OF ORGANIC CHEMISTRY American Chemical Society ({ACS}) 68 (17) 6605 - 6610 0022-3263 2003/08 [Refereed][Not invited]
     
    2,2'-[2,2-Bis(4-dimethylaminophenyl)ethenyl]biphenyl (1) is a strong electron donor that undergoes oxidative C-C bond formation to give a stable dication rac-2(2+), the 9,10-dihydrophenanthrene derivative substituted with two bis(4-dimethylaminophenyl)methylium chromophores. This dication salt regenerates the starting diolefin 1 by reductive C-C bond breaking, thus realizing a new electrochronic system with high electrochemical bistability and a vivid change in color from yellow to deep blue. Similarly, the binaphthylic diolefin rac-3 and the helicene-type dication rac-4(2+) are interconvertible upon two-electron transfer. Both the UV-vis and CD spectra changed drastically upon electrochemical transformation between optically pure 3 and 4(2+), which represents a new electrochiroptical system.
  • T Suzuki, T Nagasu, H Kawai, K Fujiwara, T Tsuji
    TETRAHEDRON LETTERS Elsevier {BV} 44 (32) 6095 - 6098 0040-4039 2003/08 [Refereed][Not invited]
     
    Oxidation of 1,2,2-tris(4-dimethylaminophenyl)- and 2,2-bis(4-dimethylaminophenyl)-1-phenylacenaphthen-1-ols 1a,b with I-2 induced the C-1-C-2 bond fission to give 8-aroylnaphthalen-1-yl-bis(4-dimethylaminophenyl)carbenium derivatives 2a,b(+), the intramolecular Lewis acid-base pairs. Treatment of 1 with HBF4 did not induce the expected C-OH bond heterolysis but caused fission of CO-H and C-1-C-2 bonds to give exactly the same carbenium 2(+). (C) 2003 Elsevier Ltd. All rights reserved.
  • T Suzuki, T Nagasu, H Kawai, K Fujiwara, T Tsuji
    TETRAHEDRON LETTERS Elsevier {BV} 44 (32) 6095 - 6098 0040-4039 2003/08 [Refereed][Not invited]
     
    Oxidation of 1,2,2-tris(4-dimethylaminophenyl)- and 2,2-bis(4-dimethylaminophenyl)-1-phenylacenaphthen-1-ols 1a,b with I-2 induced the C-1-C-2 bond fission to give 8-aroylnaphthalen-1-yl-bis(4-dimethylaminophenyl)carbenium derivatives 2a,b(+), the intramolecular Lewis acid-base pairs. Treatment of 1 with HBF4 did not induce the expected C-OH bond heterolysis but caused fission of CO-H and C-1-C-2 bonds to give exactly the same carbenium 2(+). (C) 2003 Elsevier Ltd. All rights reserved.
  • Takanori Suzuki, Hiroki Higuchi, Takashi Tsuji, Jun-ichi Nishida, Yoshiro Yamashita, Tsutomu Miyashi
    ChemInform Wiley-Blackwell 34 (23) 2003/06 [Refereed][Not invited]
  • T Suzuki, J Nishida, E Hirota, M Ohkita, T Tsuji
    SYNTHETIC METALS 133 357 - 358 0379-6779 2003/03 [Not refereed][Not invited]
     
    The electrochiroptical systems are a new type of transducers that transform the electrochemical input into the UV-Vis as well as chiroptical outputs. Several previous examples are briefly reviewed. The new concept to realize the drastic chiroptical response is proposed. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Takanori Suzuki, Hiroki Higuchi, Takashi Tsuji, Jun-ichi Nishida, Yoshiro Yamashita, Tsutomu Miyashi
    Springer Series in Chemical Physics Springer Science $\mathplus$ Business Media 70 3 - 24 0172-6218 2003/01/22 [Refereed][Not invited]
     
    "Dynamic redox systems" is the name given to a certain class of compounds that can be reversibly converted into the corresponding charged species upon electron transfer (ET) but accompanied by drastic structural changes and/or covalent bond making/breaking. Although transformation between the neutral and charged species proceeds quantitatively in most cases, their electrochemical processes are irreversible owing to the chemical reactions followed by ET. This situation endows the "dynamic redox pairs" with very high bistability, which is a prerequisite in order to construct the molecular response systems. This chapter first describes the principle of the "dynamic redox properties", and then classifies the compounds into several categories from the viewpoint of the type of structrual changes. After the properties of representative molecules in each category have been described in detail, their expected use as unimolecular devices is commented on in the final part of the chapter.
  • Suzuki, T.; Higuchi, H.; Tsuji, T.; Nishida, J.; Yamashita, Y.; Miyashi, T.: Dynamic Redox Systems: Toward the Realization of Unimolecular Memory, 3-24 (Nakamura, T.; Matsumoto, T.; Tada, H.; Sugiura, K. "Chemistry of Nanomolecular Systems", Springer, ・・・
    2003 [Not refereed][Not invited]
     
    Suzuki, T.; Higuchi, H.; Tsuji, T.; Nishida, J.; Yamashita, Y.; Miyashi, T.: Dynamic Redox Systems: Toward the Realization of Unimolecular Memory, 3-24 (Nakamura, T.; Matsumoto, T.; Tada, H.; Sugiura, K. "Chemistry of Nanomolecular Systems", Springer, Berlin) (2003)
  • T Tsuji, M Okuyama, M Ohkita, H Kawai, T Suzuki
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 125 (4) 951 - 961 0002-7863 2003/01 [Refereed][Not invited]
     
    Kinetic stabilization of the [4]paracyclophane skeleton by the introduction of substituents, which serve to sterically hinder reactions at the reactive bridgehead sites, and properties of the resultant [4]paracyclophanes are investigated in this study. Modification of the property of [4]paracyclophane by functionalization is also intended. [4]Paracyclophanes are designed to be derived from the corresponding Dewar benzene isomers via their photochemical aromatization, and the requisite 1,4-bridged Dewar benzenes bearing sterically demanding functional groups are prepared. Irradiation of these precursors under matrix isolation at 77 K leads to the formation of [4)paracyclophanes, which exhibit characteristic electronic absorption spectra. The half-lives of the generated species vary widely from less than 1 min at -90 degreesC to 0.5 h at -20 degreesC, depending on the type of substituents and the pattern of substitution. One of the derivatives, 24, is stable enough and its content in the irradiated mixture is high enough to permit the measurement of the H-1 NMR spectrum. The recorded spectrum, which is reproduced very well by theoretical calculations using the GIAO method at the hybrid HF-DFT (B3LYP/6-31+G*) level, suggests the sustenance of rather strong diatropicity in its severely bent benzene moiety. Calculations on the bent benzene whose geometry is constrained to that calculated for 24 support that aromaticity is retained to a significant extent as compared to that of planar benzene, as judged by the magnetic criteria of aromaticity, that is, diamagnetic susceptibility exaltation and nucleus-in dependent chemical shift. The reason for the retention of aromaticity despite the severe bending of the benzene ring is discussed. Cyclophane 24 is so strained that it exceeds the corresponding Dewar benzene precursor in energy and thermally reverts to the latter with a half-life of 15 +/- 5 min at -20 degreesC (DeltaG(double dagger) = 18.3 +/- 0.3 kcal mol(-1)).
  • Takanori Suzuki, Rie Yamamoto, Hiroki Higuchi, Erika Hirota, Masakazu Ohkita, Takashi Tsuji
    J. Chem. Soc., Perkin Trans. 2 Royal Society of Chemistry ({RSC}) (11) 1937 - 1942 1470-1820 2002/10 [Refereed][Not invited]
     
    Upon two-electron oxidation of the title electron donor 1a, the elongated central C9-C10 bond [1.656(5) Å (X-ray)] is cleaved to give the biphenyl-2,2′-diyl bis(xanthenylium) dye 2a+2, which regenerates the colorless dispiro compound 1a by two-electron reduction. The presence of isosbestic points in the UV-Vis spectra during the electrochemical oxidation of 1a to 2a+2 indicates the negligible steady-state concentration of the intermediate cation radical. Interconversion between optically resolved 1a and 2a+2 is accompanied by drastic changes in the CD spectra again with several isosbestic points, and racemization of (P)- and (M)-1a and (S)- and (R)-2a+2 does not occur at ambient conditions. This redox pair represents a new motif for the multi-output response system, where the electrochemical input is transduced into two independent spectral outputs.
  • Jun-ichi Nishida, Takanori Suzuki, Takashi Tsuji
    ChemInform Wiley-Blackwell 33 (26) no  2002/07 [Refereed][Not invited]
  • Jun-ichi Nishida, Takanori Suzuki, Takashi Tsuji
    J. Syn. Org. Chem., Jpn. The Society of Synthetic Organic Chemistry, Japan 60 (1) 40  2002 [Refereed][Not invited]
  • M Ohkita, M Kawano, T Suzuki, T Tsuji
    CHEMICAL COMMUNICATIONS (24) 3054 - 3055 1359-7345 2002 [Refereed][Not invited]
     
    The crystallization of 2,4,6-triethynyl-1,3,5-triazine (2) leads to a pi-stacked layered structure of a C(sp)-H...N hydrogen-bonded unique hexagonal network structure, which may be regarded as a supramolecular analogue of a hitherto unknown graphyne network: in-plane intermolecular interactions are short and linear H...N contacts (2.31 and 2.34 Angstrom) and the interlayer separation is 3.23 Angstrom.
  • T Suzuki, T Tsuji, T Okubo, A Okada, Y Obana, T Fukushima, T Miyashi, Y Yamashita
    JOURNAL OF ORGANIC CHEMISTRY 66 (26) 8954 - 8960 0022-3263 2001/12 [Refereed][Not invited]
     
    4,7-Bis(dialkylamino)benzo[c] [1,2,5]chalcogenadiazoles are a novel class of organic dyes that undergo reversible two-stage one-electron oxidation as well as one-electron reduction. They exhibit absorption maxima in the long-wavelength region, which are assigned as intramolecular charge transfer bands from the phenylenediamine moiety to the electron-accepting heterocycle. Their redox properties as well as molecular and crystal structures are affected by the alkyl substituents on the amino nitrogen and/or by the chalcogen atom (O, S, Se) in the heterocycle.
  • T Suzuki, H Higuchi, M Ohkita, T Tsuji
    CHEMICAL COMMUNICATIONS (17) 1574 - 1575 1359-7345 2001/09 [Refereed][Not invited]
     
    Upon oxidative dimerization of pale yellow Ar2C-CHPh 1 (Ar = 4-Me2NC6H4), deep blue 1,4-dication 2(2+) was obtained as a stable salt, which was transformed into I by reductive C-C bond fission; deprotonation of 22+ gave intense yellow diene 3, which was interconvertible with violet dication 4(2+) by two-electron transfer, thus exhibiting two distinct modes of electrochromism before and after proton transfer.
  • Jun-ichi Nishida, Takanori Suzuki, Masakazu Ohkita, Takashi Tsuji
    Angewandte Chemie Wiley-Blackwell 113 (17) 3351  2001/09 [Refereed][Not invited]
  • Masakazu Ohkita, Takanori Suzuki, Takashi Tsuji, Keitaro Nakatani
    Chemical Communications Royal Society of Chemistry ({RSC}) (16) 1454 - 1455 1359-7345 2001/08/21 [Refereed][Not invited]
     
    The crystallization of 4-ethynylpyridine (1) and 4-(4-ethynylphenyl)ethynylpyridine (2) leads to C(sp)-H···N hydrogen bonded straight tapes that further assemble into polar crystals, in the case of 2, and show intense powder SHG response, 8 times more efficient than crystalline urea.
  • Takanori Suzuki, Tsuyoshi Yoshino, Masakazu Ohkita, Takashi Tsuji
    ChemInform Wiley-Blackwell 32 (7) no  2001/02 [Refereed][Not invited]
  • T. Suzuki, S. Miyanari, Y. Tsubata, T. Fukushima, T. Miyashi, Y. Yamashita, K. Imaeda, T. Ishida, T. Nogami
    Journal of Organic Chemistry American Chemical Society ({ACS}) 66 (1) 216 - 224 0022-3263 2001/01/12 [Refereed][Not invited]
     
    N,N′-Dicyanonaphthoquinodiimines fused with a pyrazine ring 1 were prepared from the corresponding quinones 4. The new acceptors 1 have a planar π-system and undergo reversible two-stage 1e-reduction. Quaternization of the pyridyl substituent in 1d-f gave pyridinium derivatives 2d+, 2e+, and R-3+, respectively, which are stronger acceptors that undergo three-stage 1e-reduction. Upon electrochemical reduction of these cations, novel radicals 2d·, 2e·, and R-3· were generated and isolated as stable solids. The molecular geometries determined by X-ray analysis indicated that these radicals adopt a zwitterionic structure, in which the unpaired electron is located on the quinodiimine unit but not on the pyridyl group. These novel radicals undergo facile and reversible 1e-oxidation as well as two-stage 1e-reduction. The observed amphotericity endows the radicals with electrical conductivities (10-5 to 10-9 S cm-1), and these thus represent a new motif for singlecomponent organic semiconductors.
  • T Suzuki, M Yamada, M Ohkita, T Tsuji
    HETEROCYCLES 54 (1) 387 - 394 0385-5414 2001/01 [Not refereed][Not invited]
     
    One electron oxidation of 4-(2-tetrathiafulvalenyl)phenyl substituted dicyanomethylides (1-) gave black solids of the title radicals (1(.)). They exhibit quite high electrochemical amphotericity, which may be responsible for their good electrical conductivities (sigma = ca. 10(-7) S cm(-1)) as a single component. Isomeric radicals (2(.)) with a m-phenylene spacer could not be obtained under the similar conditions probably due to insufficient delocalization of the unpaired electron.
  • Masakazu Ohkita, Takanori Suzuki, Keitaro Nakatani, Takashi Tsuji
    Chem. Lett. Chemical Society of Japan (10) 988  2001 [Refereed][Not invited]
  • Takanori Suzuki, Kazunori Ono, Hidetoshi Kawai, Takashi Tsuji
    J. Chem. Soc., Perkin Trans. 2 Royal Society of Chemistry ({RSC}) (9) 1798  2001 [Refereed][Not invited]
  • Takanori Suzuki, Masahiro Yamada, Masakazu Ohkita, Takashi Tsuji
    HETEROCYCLES Japan Institute of Heterocyclic Chemistry 54 (1) 387  2001 [Refereed][Not invited]
  • Hidetoshi Kawai, Takanori Suzuki, Masakazu Ohkita, Takashi Tsuji
    Chem. Eur. J. Wiley-Blackwell 6 (22) 4177  2000/11 [Refereed][Not invited]
  • Hidetoshi Kawai, Takanori Suzuki, Masakazu Ohkita, Takashi Tsuji
    Chem. Eur. J. Wiley-Blackwell 6 (22) 4177  2000/11 [Refereed][Not invited]
  • Hidetoshi Kawai, Takanori Suzuki, Masakazu Ohkita, Takashi Tsuji
    Chem. Eur. J. Wiley-Blackwell 6 (22) 4177  2000/11 [Refereed][Not invited]
  • Masakazu Ohkita, Kieko Sano, Sotoyuki Dohba, Yuko Fujita, Takanori Suzuki, Takashi Tsuji
    ChemInform Wiley-Blackwell 31 (41) no  2000/10 [Refereed][Not invited]
  • T Suzuki, T Yoshino, J Nishida, M Ohkita, T Tsuji
    JOURNAL OF ORGANIC CHEMISTRY 65 (18) 5514 - 5521 0022-3263 2000/09 [Refereed][Not invited]
     
    A series of 1,3,5-trithianes 1-3 having diarylmethylene units were designed as novel electron donors giving highly colored cationic species upon oxidation. They were prepared along with the dithiane and dithiazine derivatives 4-6 by the reactions of lithiated heterocycles with diaryl ketones followed by dehydration. Voltammetric analyses indicate that a large structural change and/or transannular bonding are induced during their electrochemical oxidation. Mono(diarylmethylene) derivative 1a exhibits electrochromism with vivid change in color from faintly yellow to deep blue with concomitant rotation around the exocyclic bond. Both of the strongly colored salts obtained upon oxidation of 2,4-bis- and 2,4,6-tris(diarylmethylene)-1,3,5-trithianes (2aa and 3) consist of the dications with a 1,2,4-trithiane ring, suggesting the easy skeletal rearrangement of the transannular dications with a trithiabicylo[3. 1.0]hexane ring. Upon reduction of these salts were obtained bright yellow 12 and 13, respectively, with high electron-donating properties due to the tetraarylbutadiene-type conjugation, thus giving another class of electrochromic compounds.
  • T Suzuki, K Ono, J Nishida, H Takahashi, T Tsuji
    JOURNAL OF ORGANIC CHEMISTRY 65 (16) 4944 - 4948 0022-3263 2000/08 [Refereed][Not invited]
     
    9,10-Dihydrophenanthrene derivatives 1-3 with electron-donating and/or -accepting groups at their 9,10-positions were prepared, and their precise molecular structures were determined by X-ray analyses at 203 K. The long C-9-C-10 bond [1.646(4) Angstrom] in the hexaarylethane-type compound 1 with four electron-donating groups is mainly caused by steric interaction. Push-pull type substitution does not induce the elongation of the central bond in the present system; the corresponding distance in 9,9-bis(4-dimethylaminophenyl)-10,10-dicyano derivative 2 [1.599(4) Angstrom] is intermediate between those of 1 and the tetracyano compound 3 [1.587(2) Angstrom].
  • M Ohkita, K Ando, T Suzuki, T Tsuji
    JOURNAL OF ORGANIC CHEMISTRY 65 (14) 4385 - 4390 0022-3263 2000/07 [Refereed][Not invited]
     
    A general synthetic approach to strained p-phenylene-based acetylenic macrocycles is described. A key feature in this approach is exploitation of Dewar benzene as an angular p-phenylene synthon. Thus, 1,4-acetal-bridged 2,5-dichloro(Dewar benzene) 5, prepared in four steps from dimethyl acetylenedicarboxylate and 1,2-dichloroethylene, is applied as such a building block in the syntheses of strained macrocycles 13 and anti-20. For the synthesis of 13, m-phenylene units are used as spacers and modified Eglington-Glaser coupling is applied for the macrocyclization step. For the synthesis of anti-20, on the other hand, o-phenylene units are used as spacers and Sonogashira coupling is applied for the macrocyclization step. Macrocycles 13 and anti-20 are characterized crystallographically? and their strained nature is reflected mainly in the deviation of the acetylene units from linearity; the C=C-C angles range from 168.7(3)degrees to 179.9(3)degrees in 13 and from 168.0(5)degrees to 171.4(4)degrees in anti-20, Macrocycle 13 shows unique conformational property, namely, the p-phenylene units arranged in parallel in the rectangular framework rotate freely about the long axes, as evidenced by the H-1 NMR studies. Macrocycle anti-20 exhibits a Stokes shift of 179 nm, which is exceptionally large for phenylacetylene macrocycles, presumably owing to the characteristic stacking structure.
  • Takanori Suzuki, Jun-ichi Nishida, Masakazu Ohkita, Takashi Tsuji
    Angewandte Chemie International Edition Wiley-Blackwell 39 (10) 1804 - 1806 1433-7851 2000/05/15 [Refereed][Not invited]
     
    The hitherto unknown 1,2,6-tricyclononane derivatives 1 (X = O, S) were readily obtained upon the electrochemical 2 electron reduction of 22+ in air (see scheme). Oxidative deoxygenation of the colorless peroxides 1 regenerates the orange 22+ ions.
  • Takanori Suzuki, Jun-ichi Nishida, Masakazu Ohkita, Takashi Tsuji
    Angew. Chem. Int. Ed. Wiley-Blackwell 39 (10) 1804  2000/05 [Refereed][Not invited]
  • Takanori Suzuki, Tsuyoshi Yoshino, Masakazu Ohkita, Takashi Tsuji
    Journal of the Chemical Society, Perkin Transactions 1 Royal Society of Chemistry ({RSC}) (20) 3417  2000 [Refereed][Not invited]
  • Masakazu Ohkita, Kohta Ando, Ken-ichi Yamamoto, Takanori Suzuki, Takashi Tsuji
    Chemical Communications Royal Society of Chemistry ({RSC}) (1) 83  2000 [Refereed][Not invited]
  • Takanori Suzuki, Tsuyoshi Yoshino, Jun-ichi Nishida, Masakazu Ohkita, Takashi Tsuji
    ChemInform Wiley-Blackwell 31 (51) no  2000 [Refereed][Not invited]
  • Masakazu Ohkita, Kieko Sano, Sotoyuki Dohba, Yuko Fujita, Takanori Suzuki, Takashi Tsuji
    Journal of the Chemical Society, Perkin Transactions 1 Royal Society of Chemistry ({RSC}) (12) 1971  2000 [Refereed][Not invited]
  • Masakazu Ohkita, Takanori Suzuki, Takashi Tsuji
    ChemInform Wiley-Blackwell 31 (2) no  2000/01 [Refereed][Not invited]
  • Takanori Suzuki, Takashi Tsuji, Takanori Fukushima, Setsuko Miyanari, Tsutomu Miyashi, Yasuyuki Sakata, Tsutomu Kouda, Hiroki Kamiyama
    ChemInform Wiley-Blackwell 31 (2) no  2000/01 [Refereed][Not invited]
  • Takanori Suzuki, Takashi Tsuji, Takanori Fukushima, Setsuko Miyanari, Tsutomu Miyashi, Yasuyuki Sakata, Tsutomu Kouda, Hiroki Kamiyama
    The Journal of Organic Chemistry American Chemical Society ({ACS}) 64 (19) 7107  1999/09 [Refereed][Not invited]
  • Takanori Fukushima, Nobuharu Okazeri, Tsutomu Miyashi, Kazuharu Suzuki, Yoshiro Yamashita, Takanori Suzuki
    Tetrahedron Letters Elsevier {BV} 40 (6) 1175  1999/02 [Refereed][Not invited]
  • Takanori Fukushima, Nobuharu Okazeri, Tsutomu Miyashi, Kazuharu Suzuki, Yoshiro Yamashita, Takanori Suzuki
    Tetrahedron Letters Elsevier {BV} 40 (6) 1175  1999/02 [Refereed][Not invited]
  • Masakazu Ohkita, Takanori Suzuki, Takashi Tsuji
    Chemical Communications Royal Society of Chemistry ({RSC}) (19) 1999  1999 [Refereed][Not invited]
  • Hidetoshi Kawai, Takanori Suzuki, Masakazu Ohkita, Takashi Tsuji
    Angewandte Chemie International Edition Wiley-Blackwell 37 (6) 817  1998/04 [Refereed][Not invited]
  • Hidetoshi Kawai, Takanori Suzuki, Masakazu Ohkita, Takashi Tsuji
    Angewandte Chemie International Edition Wiley-Blackwell 37 (6) 817  1998/04 [Refereed][Not invited]
  • Hidetoshi Kawai, Takanori Suzuki, Masakazu Ohkita, Takashi Tsuji
    Angewandte Chemie Wiley-Blackwell 110 (6) 827  1998/03 [Refereed][Not invited]
  • Takanori Suzuki, Jun-ichi Nishida, Takashi Tsuji
    Chemical Communications Royal Society of Chemistry ({RSC}) (13) 1331  1998 [Refereed][Not invited]
  • Takanori Suzuki, Jun-ichi Nishida, Takashi Tsuji
    Chemical Communications Royal Society of Chemistry ({RSC}) (20) 2193  1998 [Refereed][Not invited]
  • Takanori Suzuki, Jun-ich Nishida, Takashi Tsuji
    Angewandte Chemie International Edition in English Wiley-Blackwell 36 (12) 1329  1997/07 [Refereed][Not invited]
  • Takanori Suzuki, Jun-Ich Nishida, Takashi Tsuji
    Angewandte Chemie Wiley-Blackwell 109 (12) 1387  1997/06 [Refereed][Not invited]
  • Takanori Suzuki, Takanori Fukushima, Tsutomu Miyashi, Takashi Tsuji
    Angewandte Chemie International Edition in English Wiley-Blackwell 36 (22) 2495  1997 [Refereed][Not invited]
  • Takanori Suzuki, Masahide Kondo, Tatsuo Nakamura, Takanori Fukushima, Tsutomu Miyashi
    Chemical Communications Royal Society of Chemistry ({RSC}) (23) 2325  1997 [Refereed][Not invited]
  • Yasutake Takahashi, Hitoshi Ohaku, Shin-ichi Morishima, Takanori Suzuki, Hiroshi Ikeda, Tsutomu Miyashi
    Journal of the Chemical Society, Perkin Transactions 1 Royal Society of Chemistry ({RSC}) (4) 319  1996 [Refereed][Not invited]
  • Teruo Kurihara, Takanori Suzuki, Hidetsugu Wakabayashi, Sumio Ishikawa, Kimio Shindo, Yuji Shimada, Hiroshi Chiba, Tsutomu Miyashi, Masafumi Yasunami, Tetsuo Nozoe
    Bulletin of the Chemical Society of Japan Chemical Society of Japan 69 (7) 2003  1996 [Refereed][Not invited]
  • M Hirayama, T Terasaka, Y Yamashita, T Susuki, T Miyashi, Y Usui
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 68 (12) 3337 - 3339 0009-2673 1995/12 [Refereed][Not invited]
     
    ESR study of the anion radical produced by the reduction of the title compound (DTB-BDTD) with potassium metal in 1,2-dimethoxyethane is reported. In addition to the satellites of O-17, C-13, and S-33, the second-generation satellite lines of extremely low intensity, arising from both C-13 and S-33 isotopes in natural abundance, have been detected. It was found that these satellites vary markedly in line width among each component of its multiplet. This line width effect was used to determine the sign of hfs constants of these magnetic nuclei, and the resulting signs agreed well with those estimated from the spin densities obtained by the McLachlan procedure and the INDO method.
  • Yasutake Takahashi, Hitoshi Ohaku, Shin-ichi Morishima, Takanori Suzuki, Tsutomu Miyashi
    Tetrahedron Letters Elsevier {BV} 36 (29) 5207  1995/07 [Refereed][Not invited]
  • Yasutake Takahashi, Hitoshi Ohaku, Shin-ichi Morishima, Takanori Suzuki, Tsutomu Miyashi
    Tetrahedron Letters Elsevier {BV} 36 (29) 5207  1995/07 [Refereed][Not invited]
  • Takanori SUZUKI
    J. Syn. Org. Chem., Jpn. The Society of Synthetic Organic Chemistry, Japan 53 (5) 403  1995 [Refereed][Not invited]
  • Masatoshi Hirayama, Manabu Itasaka, Takanori Suzuki, Yoshiro Yamashita, Tsutomu Miyashi
    Chem. Lett. Chemical Society of Japan (7) 511  1995 [Refereed][Not invited]
  • Masatoshi Hirayama, Toshitaka Terasaka, Manabu Itasaka, Takanori Suzuki, Yoshiro Yamashita, Tsutomu Miyashi
    Chem. Lett. Chemical Society of Japan (9) 837  1995 [Refereed][Not invited]
  • Takanori Suzuki, Takanori Fukushima, Yoshiro Yamashita, Tsutomu Miyashi
    J. Am. Chem. Soc. American Chemical Society ({ACS}) 116 (7) 2793  1994/04 [Refereed][Not invited]
  • Takanori Suzuki, Tomoo Sakimura, Shoji Tanaka, Yoshiro Yamashita, Hiroaki Shiohara, Tsutomu Miyashi
    Journal of the Chemical Society, Chemical Communications Royal Society of Chemistry ({RSC}) (12) 1431  1994 [Refereed][Not invited]
  • Koichi Kikuchi, Tomoharu Katagiri, Taeko Niwa, Yasutake Takahashi, Takanori Suzuki, Hiroshi Ikeda, Tsutomu Miyashi
    Chemical Physics Letters Elsevier {BV} 193 (1-3) 155  1992/05 [Refereed][Not invited]
  • Koichi Kikuchi, Tomoharu Katagiri, Taeko Niwa, Yasutake Takahashi, Takanori Suzuki, Hiroshi Ikeda, Tsutomu Miyashi
    Chemical Physics Letters Elsevier {BV} 193 (1-3) 155  1992/05 [Refereed][Not invited]
  • Takanori Suzuki, Hiroaki Shiohara, Masayuki Monobe, Tomoo Sakimura, Shoji Tanaka, Yoshiro Yamashita, Tsutomu Miyashi
    Angewandte Chemie International Edition in English Wiley-Blackwell 31 (4) 455  1992/04 [Refereed][Not invited]
  • Tsutomu Miyaji, Yoshiaki Tsubota, Takanori Suzuki, Yoshiro Yamashita, Toshio Mukai, Tsutomu Miyashi
    HETEROCYCLES Japan Institute of Heterocyclic Chemistry 33 (1) 337  1992 [Refereed][Not invited]
  • Yoshiaki Tsubata, Takanori Suzuki, Tsutomu Miyashi, Yoshiro Yamashita
    The Journal of Organic Chemistry American Chemical Society ({ACS}) 57 (25) 6749  1992 [Refereed][Not invited]
  • Kentaro Iwasaki, Akito Ugawa, Atsushi Kawamoto, Yoshiro Yamashita, Kyuya Yakushi, Takanori Suzuki, Tsutomu Miyashi
    Bulletin of the Chemical Society of Japan Chemical Society of Japan 65 (12) 3350  1992 [Refereed][Not invited]
  • Yoshiro Yamashita, Junko Eguchi, Takanori Suzuki, Chizuko Kabuto, Tsutomu Miyashi, Shoji Tanaka
    Angewandte Chemie Wiley-Blackwell 102 (6) 709  1990/06 [Refereed][Not invited]
  • Yoshiro Yamashita, Junko Eguchi, Takanori Suzuki, Chizuko Kabuto, Tsutomu Miyashi, Shoji Tanaka
    Angewandte Chemie International Edition in English Wiley-Blackwell 29 (6) 643  1990/06 [Refereed][Not invited]
  • Yoshiro Yamashita, Yoshiaki Tsubata, Takanori Suzuki, Tsutomu Miyashi, Toshio Mukai, Shoji Tanaka
    Chem. Lett. Chemical Society of Japan (3) 445  1990 [Refereed][Not invited]
  • Takanori Suzuki, Yoshiro Yamashita, Chizuko Kabuto, Tsutomu Miyashi
    Journal of the Chemical Society, Chemical Communications Royal Society of Chemistry ({RSC}) (16) 1102  1989 [Refereed][Not invited]
  • Yoshiro Yamashita, Takanori Suzuki, Tsutomu Miyashi
    Chem. Lett. Chemical Society of Japan (9) 1607  1989 [Refereed][Not invited]
  • Yoshiro Yamashita, Kenichi Saito, Takanori Suzuki, Chizuko Kabuto, Toshio Mukai, Tsutomu Miyashi
    Angewandte Chemie Wiley-Blackwell 100 (3) 428  1988/03 [Refereed][Not invited]
  • Y YAMASHITA, K SAITO, T SUZUKI, C KABUTO, T MUKAI, T MIYASHI
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION IN ENGLISH 27 (3) 434 - 435 0570-0833 1988/03 [Refereed][Not invited]
  • Masatoshi Hirayama, Akihiko Seki, Yoshiro Yamashita, Takanori Suzuki, Tsutomu Miyashi
    Chem. Lett. Chemical Society of Japan (1) 67  1988 [Refereed][Not invited]
  • Masatoshi Hirayama, Akihiko Seki, Yoshiro Yamashita, Takanori Suzuki, Tsutomu Miyashi
    Journal of the Chemical Society, Chemical Communications Royal Society of Chemistry ({RSC}) (7) 490  1988 [Refereed][Not invited]
  • Takanori Suzuki, Chizuko Kabuto, Yoshiro Yamashita, Toshio Mukai, Tsutomu Miyashi
    Journal of the Chemical Society, Chemical Communications Royal Society of Chemistry ({RSC}) (13) 895  1988 [Refereed][Not invited]
  • Takanori Suzuki, Chizuko Kabuto, Yoshiro Yamashita, Toshio Mukai, Tsutomu Miyashi, Gunzi Saito
    Bulletin of the Chemical Society of Japan Chemical Society of Japan 61 (2) 483  1988 [Refereed][Not invited]
  • Takanori Suzuki, Chizuko Kabuto, Yoshiro Yamashita, Toshio Mukai
    Chem. Lett. Chemical Society of Japan (6) 1129  1987 [Refereed][Not invited]
  • Yoshiro Yamashita, Takanori Suzuki, Toshio Mukai
    Journal of the Chemical Society, Chemical Communications Royal Society of Chemistry ({RSC}) (15) 1184  1987 [Refereed][Not invited]
  • Takanori Suzuki, Chizuko Kabuto, Yoshiro Yamashita, Tsutomu Miyashi
    Bulletin of the Chemical Society of Japan Chemical Society of Japan 60 (9) 3459  1987 [Refereed][Not invited]
  • Chizuko Kabuto, Yoshimasa Fukazawa, Takanori Suzuki, Yoshiro Yamashita, Tsutomu Miyashi, Toshio Mukai
    Tetrahedron Letters Elsevier {BV} 27 (8) 925  1986/01 [Refereed][Not invited]
  • Yoshiro Yamashita, Takanori Suzuki, Gunzi Saito, Toshio Mukai
    Chem. Lett. Chemical Society of Japan (5) 715  1986 [Refereed][Not invited]
  • Yoshiro Yamashita, Takanori Suzuki, Gunzi Saito, Toshio Mukai
    Journal of the Chemical Society, Chemical Communications Royal Society of Chemistry ({RSC}) (19) 1489  1986 [Refereed][Not invited]
  • Chizuko Kabuto, Takanori Suzuki, Yoshiro Yamashita, Toshio Mukai
    Chem. Lett. Chemical Society of Japan (9) 1433  1986 [Refereed][Not invited]
  • Chizuko Kabuto, Yoshimasa Fukazawa, Takanori Suzuki, Yoshiro Yamashita, Tsutomu Miyashi, Toshio Mukai
    Tetrahedron Letters Elsevier {BV} 27 (8) 925  1986/01 [Refereed][Not invited]
  • Yoshiro Yamashita, Takanori Suzuki, Toshio Mukai, Gunzi Saito
    Journal of the Chemical Society, Chemical Communications Royal Society of Chemistry ({RSC}) (15) 1044  1985 [Refereed][Not invited]
  • Yoshiro Yamashita, Takanori Suzuki, Gunzi Saito, Toshio Mukai
    Chem. Lett. Chemical Society of Japan (11) 1759  1985 [Refereed][Not invited]
  • Toshio Mukai, Takanori Suzuki, Yoshiro Yamashita
    Bulletin of the Chemical Society of Japan Chemical Society of Japan 58 (8) 2433  1985 [Refereed][Not invited]

Conference Activities & Talks

  • Studies on Dynamic Redox Systems: Construction of Record-breaking Strained Compounds and Development of Unimolecular Memory  [Not invited]
    鈴木 孝紀
    The 99th CSJ Annual Meeting, Award Lecutre,  2019/03
  • 超結合:共有結合の限界を超えた化学  [Not invited]
    鈴木 孝紀
    日本化学会第99春季年会特別企画  2019/03

Industrial Property Rights

  • 特願2004-265909:新規なビキサンテン化合物およびビスキサンテニリウム化合物とその製造方法、およびその用途  2004年
    鈴木孝紀, 藤原憲秀, 河合英敏, 田中祥子, 樋口博紀
  • 特願2004-031074:新規なビアクリダン化合物およびビスアクリジニウム化合物とその製造法、およびその用途  2004年
    鈴木孝紀, 辻孝, 藤原憲秀, 河合英敏, 樋口博紀, 右田章, 太田賢司

Awards & Honors

  • 2019/03 The Chemical Society of Japan Academic Award
     
    受賞者: SUZUKI Takanori
  • 2004/09 第一回野副鉄男教授記念奨励賞
     
    受賞者: 鈴木 孝紀
  • 1996/03 日本化学会進歩賞
     
    受賞者: 鈴木 孝紀

Research Grants & Projects

  • ドナーアクセプター連結型中分子による生物機能/光機能分子創出
    文部科学省:科学研究費補助金(新学術領域(研究領域提案型))
    Date (from‐to) : 2018/04 -2020/03 
    Author : 鈴木 孝紀
  • 安定な1,4-ジイルジカチオンの発生/消失に伴うモノマー/ポリマースイッチング
    文部科学省:科学研究費補助金(競争的萌芽研究)
    Date (from‐to) : 2016/04 -2019/03 
    Author : 鈴木 孝紀
  • 文部科学省:科学研究費補助金(基盤研究(B))
    Date (from‐to) : 2015 -2019 
    Author : 鈴木 孝紀
  • マルチレドックスサイト型オリゴマー中分子による生物機能分子創出
    文部科学省:科学研究費補助金(新学術領域(研究領域提案型))
    Date (from‐to) : 2016/04 -2018/03 
    Author : 鈴木 孝紀
  • 文部科学省:科学研究費補助金(挑戦的萌芽研究)
    Date (from‐to) : 2013 -2014 
    Author : 鈴木 孝紀
     
    本申請中でのもっとも重要な命題(MFMS)Maximum Function on Minimum Skeleton(MFMS)は、「如何にして単純な骨格に多用な機能を盛り込むか」であり、今年度は、熱・光・電場などの外部刺激に対してその物性値を可逆的に変化させる応答性分子に注目した。C9,C10位にジ(スピロアクリダン)骨格の置換したジヒドロフェナントレン誘導体1aはヘキサフェニルエタンと類似した部分構造を持ち、電気化学的入力に対してC9-C10『エタン結合』の切断による安定なジカチオン2a2+の生成を伴いながら、UV-Visおよび蛍光スペクトルの変化する多重出力エレクトロクロミズム応答を示す。1a及び2a2+はいずれもヘリシティ、軸不斉といった不斉要素を持つが、室温でもその立体配置は容易に反転する。一方、適切な分子設計を行い1a及び2a2+の立体反転を抑制すれば、ジヒドロフェナントレン誘導体キラルカラムを用いた光学分割が可能であり、また、立体配置を保ったまま対応するジカチオンと相互変換できると考えた。実際にC4,C5位にメチル基を導入した1bやジベンゾ縮環体1cを新たに合成して検討を進めたところ、、1b,cや2b,c2+の立体配置は安定であり、ねじれたπ系を有する光学活性な酸化還元対が非常に大きな円二色性(CD)を示すため、1b,c/2b,c2+の電気化学的相互変換では、これまでの応答に加えCDを更なる出力とした多重出力応答挙動を示すことが明らかとなった。これは、既存の骨格にごく小さな構造的摂動を加えることで、新たな機能を付与できたこと示す例であり、MFMSの遂行が成功したことを意味する。
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(新学術領域研究(研究領域提案型))
    Date (from‐to) : 2009 -2013 
    Author : TAKANORI SUZUKI
     
    Electrochromism is a representative function of organic redox systems, by which electrochemical input is reversibly transduced into UV-Vis spectral output. Based on our previous studies on "dynamic redox (dyrex)" systems that undergo reversible C-C bond-formation/-cleavage upon electron transfer, we envisaged that the assembled multiple functions would be endowed under the novel molecular design, and such materials could be prepared exclusively only by using newly developed synthetic methods based on integrated reactions. This work can be divided into two parts: [1] studies on NOVEL MATERIALS exhibiting dynamic redox behavior prepared by integrated reactions; and [2] characterization and exploration of organic redox systems newly prepared by NOVEL INTEGRATED REACTIONS. Most of the research results have been published.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 2009 -2011 
    Author : Takanori SUZUKI, Kenshu FUJIWARA, Hidetoshi KAWAI
     
    Based on our own results for hexaphenylethane derivative studied so far, it has been proposed that the compound with a ultralong C-C bond would be generated as a stable entity when the two unpaired electron are forced to stay in a proximity in the corresponding diradical without isomerization into the closed-shell species through resonance/peri-cyclic reactions. Based on the above concept have been designed a series of tetraarylpyracenes where the longest C-C bond ever [1.791(3)Å] was determined experimentally. The expandability of such prestrained bonds was also uncovered.
  • 文部科学省:科学研究費補助金(萌芽研究)
    Date (from‐to) : 2005 -2007 
    Author : 鈴木 孝紀, 藤原 憲秀, 河合 英敏
     
    申請者は本課題の中で「動的シクロファン」という概念を提案した。これは、外部刺激によってシクロファンの持つ歪みや骨格構造に摂動を与え、それに付随する渡環相互作用の変化やシクロファンに特徴的な物性値変化を応答出力として取り出すというユニークな試みである。これまでテレフタルアミドの様々誘導体へのp-キシリレンジアンモニウム型ゲストの添加による「超分子シクロファン」の検討を行っている。例えば、応答型レセプター機能を持つシクロファンについての検討を行い、分子内に2つのテレフタルアミド骨格を持ち、,これらが二組の1,4-ビス(フェニルエチニル)ベンゼン発色団で架橋された大環状シクロファンについては、不斉なゲストを錯形成させた時、ゲストのエナンチオマーの一方はねじれ構造への変形を引き起こすが、その鏡像体との錯形成ではホストは長方形の構造のままで変形が誘起されないという興味深い結果が得られている。これらは、円二色性(CD)出力を合わせ持つシグナリングホストとなることものである。上記の成果に基づき今年度は、6置換ベンゼンとなる2,3,5,6-テトラアリールテレフタルアミドをモチーフとして、これらが1)非会合状態ではアミドがアンチ配座となり6つの置換基は非プロペラ配置をとる、2)ジアンモニウムが会合して超分子シクロファンとなると、シン配座になったアミド基のdirecting効果により、プロペラ配座に変化する、3)点不斉の情報がプロペラ構造の動的なヘリシティに効果的に転写されることで動的応答挙動が付与される、という分子プロペラの系を確立に成功した(投稿中)
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 2003 -2005 
    Author : Takanori SUZUKI, Kenshu FUJIWARA
     
    This project has been planned to develop new design concepts on the novel organic responding molecules based on the integration of redox active molecules. The major themes to be tackled with are as follows : (1) Redox response systems with electrochemical bistability and surface modifying properties ; (2) New synthetic strategy for the fused- polyether structures ; (3) Redox active molecules with phase transition properties triggered by external stimuli.We have succeeded in preparing redox systems to meet the requirement in the first theme, and some of them are further endowed with multi-input and multi-output fuctionalities. The disuflide unit or ethynyl groups were selected that act as surface-binding linkers for Au an Si, respectively. Preparation of SAM and examination toward the realization of unimolecular memory are now under way.The fused-polyether skeleton found in some marine natural products should be a suitable motif for studying the aggregation by weak C-H--O hydrogen bonds. In the second theme, facile and general convergent strategy was developed for a variety of polyether skeleton. Based on the newly developed protocol based on the reaction between an aldehyde and an acylanion equivalent, we could synthesize polyetheral natural product (hemibrevetoxin B) and the large segments of ciguatoxins with 4-5 ether units. X-ray analyses on some of them have revealed that several short C-H--O contacts were observed that connect tape-shaped polyethers tol the stacked or dimeric strucures. Not only natural but also non-natural polyethers are shown worth investigated.Reversible oligomerization of bis(diarylethenyl)arenes-type electron donors upon oxidation is the outstanding achievement in terms of the third theme. Deeply-colored polycation oligomers could be isolated as stable salts that regenerated the starting monomeric donors upon reduction. By attaching long alkyl chains on the aryl groups, some of these materials act as organic gelators, thus giving a new desing concept for the dynamic mesophase, whose properties can be modulated by electrochemical input.
  • 文部科学省:科学研究費補助金(萌芽研究)
    Date (from‐to) : 2002 -2004 
    Author : 鈴木 孝紀
     
    本研究課題の目的は、1)不斉要素を有する有機酸化還元系の構築とその応答機能を開発し、2)それらを表面へと固定できる方法論を応用して表面物性としての機能を引き出すことにある。本年度はそれぞれ、1)テトラヒドロフェナントラアゼピン骨格を有する系の開発、2)表面修飾に利用できるアンカー置換基を有する酸化還元系の開発について検討を行った。a)アゼピン骨格を有するキラルな酸化還元系:不斉要素を有する有機酸化還元系は、電気化学的入力に対して電子スペクトル及び円二色性(CD)スペクトルの双方の出力を与える多重出力型分子応答系となる。大きなCD出力を得るためには、エキシトンカップリングの利用できる軸不斉またはらせん状化合物が望ましい。表題骨格のヘリシティは容易に反転するが、N上にキラルなベンジルアミノ基を導入することで一方のジアステレオマーを優先させることに成功した。これにより、煩雑な光学分割を行わずに感度良くエレクトロキロオプティカル出力が得られる系の構築が可能となった。b)末端アセチレンおよびジスルフィド官能基をする酸化還元系:表面での自己組織化膜の形成を行うためには、表面修飾に利用できるアンカー置換基が導入された機能性酸化還元系を合成する必要がある。これまで動的酸化還元活性が確認されたジスピロジヒドロフェナントレン骨格を有する3種の酸化還元対の、a)ベイ領域へのエチニル基に導入、b)スピロ環上へのプロパルギル基の導入、c)ベイ領域へのジスルフィド官能基の導入された化合物の合成に成功した。前2者は水素終端シリコン表面への固定に、後者は金表面への固定に利用できる官能基を有するものであり、現在膜の調製の検討を行っている。
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 2001 -2002 
    Author : Takanori SUZUKI, Takashi TSUJI
     
    This research project is intended to construct the novel molecular response systems that transduce the electrochemical input into two kinds of spectral outputs, they are UV-Vis and CD spectra. These materials are named as "electrochiroptical response systems", and considered as promising candidates for use as chiral redox memories. Compared with the extensively studied electrochromic materials giving the UV-Vis spectral change as a sole output, there have been only a few successful examples reported so far. Based on our previous results on the multi-stage redox systems endowed with high electrochemical bistability, we have designed several chiral electron donors that can be reversibly transformed into the stable dicationic species. They exhibited drastic changes in UV-Vis as well as CD spectra during the interconversion. The high amplitude in CD signals is one of the central points to be considered in the molecular design, and we have realized it by exciton coupling of two identical chromophores located at the proper positions in these molecules. We are now planning to fix these molecules on the metal surface by making SAM, so that these molecules can be used as molecular devices.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(C))
    Date (from‐to) : 1996 -1997 
    Author : Takanori SUZUKI
     
    The research project is intended to construct the novel redox-type photochromic systems based on the photoinduced electron transfer reactions of electron-donor-acceptor complexes in the crystalline state. In order to realize such an idea it is essential to develop a new type of redox molecules exhibiting bistability. Thus, the redox pairs were designed so as to undergo reversible C-C bond formation and cleavage upon electron transfer. The research started from examining the interconversion hexaphenylethane derivatives 1 and dicationic bis (triarylmethane) dyes 2. It has been found that they constitute the dynamic and reversible redox pair showing vivid change in color and drastic structural change upon electron transfer. They surely are the promising candidate for the present purpose. Unfortunately, however, attempts to obtain the CT crystal of 1 with a variety of electron donors have been unsuccessful, preventing me from realizing my initial proposal. Next, the biphenyl-type electron acceptors having dicyanovinyl moieties were investigated. 2,2'-Disubstituted derivative was found to undergo C-C bond formation upon two-electron reduction. By combining the further isomerization of the reduction product, the latter system constitute a prototype of the novel electrochromic system with "write protect" option.
  • 文部科学省:科学研究費補助金(重点領域研究)
    Date (from‐to) : 1995 -1995 
    Author : 鈴木 孝紀
     
    現在までに良好な電導性を示す数多くの分子性結晶が知らるようになったが、有機超伝導体を含めてそのほとんど全てが二成分以上から形成されている。これは、有機固体での電導性の担い手となる伝導電子を供給するという不可欠な要因によるものであるが、このこと自体が系の複雑さを増大させ、固体物性を司る結晶構造の制御をより困難にしている事も事実である。このような観点からすると単一成分有機電導体の研究はこの分野の新しい展開方向を指し示すものの一つと考えられる。そこで本課題では電気化学的両性度の高い新規な安定ラジカルを合成、単離しその単一成分有機電導体としての有効性を検討する事を目的として研究を行うことにした。実際の研究では四環性窒素複素環化合物であるキノキサロ[2,3-b]キノキサリン骨格(1)をモチーフとして選んだ。これは、ピラジンに代表される窒素複素環が代表的なW eitz型の酸化還元系を為すため電気化学的両性を付与しやすいこと、また極く限られた系ではあるものの中性ラジカルが安定に単離されている例があることを考慮した分子設計による。母体の1aとメチルトリフレートとの反応で5位が4級化されたカチオン種2aとした。このものの電子受容性は非常に高く、塩化メチレン中で還元電位の測定では+0.66及び-0.20Vに可逆な波形を示した。このことは2aの一電子還元で生成するラジカル種3aが0.86Vという小さなEsum値を持つ電気化学的両性の強い分子であることを予想させる。しかし、ヨウ化物イオンを用いた2aの還元では電子スペクトルで748nmの吸収を有する新しい化学種が観測されたものの半減期が10秒程と不安定な為その単離には至らなかった。そこで1aの1,4,7,10位の4箇所に様々な置換基を導入した化合物から出発しラジカル種3を安定に単離した。これらは10^<-7>から10^<-9>Scm^<-1>程度の電導性を示すことが明らかとなった。これらの値は決して高いものではないが、本研究の分子設計の妥当性を示すものである。
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(一般研究(C))
    Date (from‐to) : 1994 -1995 
    Author : Takanori SUZUKI
     
    The research project is intended to construct the organic redox systems which exhibit the electrochemical response such as electrochromism. In order to realize such molecular systems a new way of molecular designing was adopted where (1) the charged species would be stabilized by formation of strong chromophores with large pi-conjugation but not by aromatization and (2) drastic structural changes should be occurred during the electron transfer. These conditions are quite different from what had been used to design the multi-stage redox systems for a long time. The "dynamic redox behavior"is the central concept in this work, thus the redox pairs were designed so as to undergo reversible C-C bond formation andcleavage upon electron transfer. Dibenzo-TTF derivatives inserted with a cycloalkane ring as well as their isomersof the tricyclic skeleton were studiedin detail as prototypes. Some molecules studies here were proven to be thereversible dynamic redox systems . In orderr to construct the electrochromic systems other molecules containing triarylmethane dye skeletons were designed. The reversible interconversion between hexaarylethane derivatives and bis (triarylmethane) dications was demonstrated .
  • 文部科学省:科学研究費補助金(重点領域研究)
    Date (from‐to) : 1994 -1994 
    Author : 鈴木 孝紀
     
    本研究では電気化学的両性度の高い新規な安定ラジカルを合成単離し、その単一成分有機電導体としての有効性を検討する事を目的としている。実際の分子設計に於いては、電子供与性(D)及び受容性(A)双方の部分構造を一分子内に含むA-π-D^・型の中性ラジカルを設計した。平成6年度にはD^・骨格となるピリジル基のN上に、長さの異なるアルキル鎖を有するR-1の研究を行なった。得られたラジカルは高い電気化学的両性度を有し、またRの長さによってその酸化還元挙動は変化しない。しかし、その電導性はRの長さにより系統的に変化することが見いだされた。メチルおよびペンチル体のX線構造解析によれば、これらのラジカルはいずれもA^<-・>-π-D^+型の分極構造を有していることが示され、また結晶中に於ける分子の重なりも非常に良く似ている。しかし、Rが長くなるにつれて結晶構造の二次元性が顕著に低下し、これが電導性の変化につながっていることが明らかとなった。
  • 機能性多段階酸化還元系の開発とその応答機能
  • Molecular Response System Based on Dynamic Redox Properties

Educational Activities

Teaching Experience

  • Structural Organic Chemistry
    開講年度 : 2018
    課程区分 : 修士課程
    開講学部 : 総合化学院
    キーワード : ホスト-ゲスト化学・キラリティ
  • Molecular Chemistry (Structural and Physical Organic Chemistry)
    開講年度 : 2018
    課程区分 : 修士課程
    開講学部 : 総合化学院
    キーワード : 化学 有機化学 構造有機化学 結晶性物質 多形 非平衡 相転移 分子間相互作用 X線構造解析 長い結合
  • Freshman Seminar
    開講年度 : 2018
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 化学、有機化学、天然物化学、有機金属化学、機能性有機化学、レポートの書き方、プレゼンテーションの準備方法、効果的なプレゼンテーションとは
  • Laboratory Work in Chemistry VI
    開講年度 : 2018
    課程区分 : 学士課程
    開講学部 : 理学部
    キーワード : 基礎化学,物理化学,無機化学,分析化学,有機化学,生物化学 このうち化学実験Ⅵ は、有機化学
  • Fundamental Organic Chemistry
    開講年度 : 2018
    課程区分 : 学士課程
    開講学部 : 理学部
    キーワード : <<理学部選択必修科目>> (大項目)有機化学 (小項目)物理有機化学、構造有機化学、反応有機化学、有機電子論、反応機構、立体化学


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