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古荘 義雄

所属部署名生命科学講座(化学)
職名教授
 
 
更新日: 17/11/17 09:59

研究者基本情報

氏名

    古荘 義雄

所属(マスタ)

  • 生命科学講座(化学) 教授

学位

  • 博士(工学)(東京大学)

所属学協会

    アメリカ化学会 , 日本化学会 , 高分子学会 , 有機合成化学協会 , 近畿化学協会 , 光化学協会

委員歴

  • 2017年10月- 現在日本化学会 代議員
  • 2017年03月- 現在日本化学会近畿支部 幹事
  • 2014年08月- 2016年07月日本学術振興会 特別研究員等審査会専門委員および国際事業委員会書面審査員
  • 2010年08月- 2012年07月日本学術振興会 特別研究員等審査会専門委員および国際事業委員会書面審査員
  • 2008年11月- 2010年10月日本化学会 東海支部代議員

経歴

  • 2015年09月- 現在滋賀医科大学(教授)
  • 1995年- 2003年 大阪府立大学工学部応用化学科・助手
  • 2003年- 2008年 科学技術振興機構ERATO八島超構造らせん高分子プロジェクト・グループ・リーダー
  • 2008年- 2011年 名古屋大学大学院工学研究科物質制御工学専攻・准教授
  • 2011年- 2015年08月- 近畿大学分子工学研究所・准教授

研究活動情報

研究分野

  • 基礎化学 / 有機化学
  • 複合化学 / 合成化学
  • 複合化学 / 高分子化学
  • 複合化学 / 機能物質化学

研究キーワード

    キラリティ・円二色性・水素結合・自己集合・結晶構造

論文

  • Reversible capture and release of carbon dioxide by binary system of polyamidine and polyethylene glycol
    Furusho Yoshio, Endo Takeshi
    POLYMER BULLETIN 74(4) 1207-1219 2017年04月 [査読有り]
  • Reversible capture and release of aromatic amines by vicinal tricarbonyl compound
    Tatsuya Yuki, Tatsuya Yuki, Morio Yonekawa, Yoshio Furusho, Yoshihisa Sei, Ikuyoshi Tomita, Takeshi Endo
    Tetrahedron 72 2868-2873 2016年06月
    © 2016 Elsevier Ltd. All rights reserved.In this paper, we report reversible capture and release of aromatic amines by diphenylpropanetrione (DPPT). Addition of aromatic amines to the central carbonyl group occurred readily at ambient temperature to provide the aromatic amine adducts of DPPT (DPPT-aromatic amines), which has a hemiaminal structure. On the other hand, washing a solution of DPPT-aromatic amine with diluted hydrochloric acid (HCl) enabled successful recovery of DPPT to demonstrate the reversible nature of this system.
  • Homo-double helix formation of an optically active conjugated polymer bearing carboxy groups and amplification of the helicity upon complexation with achiral and chiral amines
    Wataru Makiguchi, Shinzo Kobayashi, Keisuke Furukawa, Hiroki Iida, Yoshio Furusho, Yoshio Furusho, Eiji Yashima
    Journal of Polymer Science, Part A: Polymer Chemistry 53 990-999 2015年04月
    © 2015 Wiley Periodicals, Inc.An optically active, m-terphenyl-based π-conjugated polymer bearing carboxy groups was synthesized by the copolymerization of the diethynyl monomer bearing a carboxy group with (S,S)-2,5-bis(2-methylbutoxy)-1,4-dibromobenzene using Sonogashira reaction. The copolymer showed a weak circular dichroism (CD) in the main-chain chromophore region due to a homo-double helix formation with an excess helical handedness biased by the chiral alkoxy substituents through self-association. However, upon complexation with achiral amines, such as piperidine, the CD intensity of the polymer significantly increased resulting in the formation of a greater excess one-handed homo-double helix via hydrogen-bonded inclusion complexation with the achiral amines between each strand, leading to the amplification of the helicity. A preferred-handed homo-double helix was also induced in the polymer in the presence of nonracemic amines. The effect of the achiral and chiral amines on the homo-double helix formation was investigated by comparing the CD spectra of the polymer to those of its model dimer.
  • Homo-double helix formation of an optically active conjugated polymer bearing carboxy groups and amplification of the helicity upon complexation with achiral and chiral amines
    Wataru Makiguchi, Shinzo Kobayashi, Keisuke Furukawa, Hiroki Iida, Yoshio Furusho, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Journal of Polymer Science, Part A: Polymer Chemistry 2015年01月
    © 2015 Wiley Periodicals, Inc.An optically active, m-terphenyl-based π-conjugated polymer bearing carboxy groups was synthesized by the copolymerization of the diethynyl monomer bearing a carboxy group with (S,S)-2,5-bis(2-methylbutoxy)-1,4-dibromobenzene using Sonogashira reaction. The copolymer showed a weak circular dichroism (CD) in the main-chain chromophore region due to a homo-double helix formation with an excess helical handedness biased by the chiral alkoxy substituents through self-association. However, upon complexation with achiral amines, such as piperidine, the CD intensity of the polymer significantly increased resulting in the formation of a greater excess one-handed homo-double helix via hydrogen-bonded inclusion complexation with the achiral amines between each strand, leading to the amplification of the helicity. A preferred-handed homo-double helix was also induced in the polymer in the presence of nonracemic amines. The effect of the achiral and chiral amines on the homo-double helix formation was investigated by comparing the CD spectra of the polymer to those of its model dimer.
  • Reversible fixation and release of carbon dioxide with a binary system consisting of polyethylene glycol and polystyrene-bearing cyclic amidine pendant group
    Mina Sakuragi, Mina Sakuragi, Naoto Aoyagi, Yoshio Furusho, Takeshi Endo
    Journal of Polymer Science, Part A: Polymer Chemistry 52 2025-2031 2014年07月
    In this study, we investigated the CO2-capture/release behavior of the polystyrene-bearing cyclic amidine pendant groups, which was synthesized via free radical polymerization of HCl salt of the corresponding styrene monomer followed by neutralization. For comparison, we also prepared the polystyrene bearing N-formyl-1,3-propanediamine pendant groups through the hydrolysis of the cyclic amidine group by treatment with an alkaline solution. First, we examined the CO2-capture/release behaviors of the amidine and amine monomers in aqueous solution in terms of conductivity. The conductivity of a wet DMSO solution of the amidine monomer increased upon CO2 bubbling at 25 C and reached a stationary value of about 11 mS/m, which indicated the formation of the bicarbonate salt. Conversely, the conductivity decreased to its original value upon N2 bubbling at 50 C, reflecting the complete release of the trapped CO2 molecules. Both solutions showed the changes in the conductivity with quick responses, and no appreciable difference was observed between them. We then investigated the CO2-capture/release behaviors of the amidine and amine polymers, by taking advantage of the binary system with polyethylene glycol, and found that the binary system with the amidine polymer captured and released CO2 more efficiently than that with the amine polymer. © 2014 Wiley Periodicals, Inc.
  • Supramolecular polymer gels formed from carboxy-terminated telechelic polybutadiene and polyamidine through amidinium-carboxylate salt bridge
    Yoshio Furusho, Takeshi Endo
    Journal of Polymer Science, Part A: Polymer Chemistry 52 1815-1824 2014年07月
    In this article, we report the preparation and properties of the bulk supramolecular polymer gels prepared from a polybutadiene based on the amidinium-carboxylate salt bridge, highlighting the difference from a well-established network system based on carboxylic acid and amine. We have prepared the amidinium-carboxylate salt bridge-based supramolecular polymer gels from a carboxy-terminated telechelic polybutadiene and a linear polyamidine having N,N′-di-substituted acetamidine group in the main chain. FTIR analysis along with Small angle X-ray scattering measurements indicated that the salt bridge was attributed to the gelation through three-dimensional network formation. Virtually no fluidity was observed for the supramolecular gel containing equimolar amounts of the carboxyl group and the amidine group, which showed a high G′ value of about 1 MPa at room temperature and a T gel of 37 C. For comparison, the supramolecular polymer gels crosslinked by ammonium-carboxylate salt were prepared using a linear polyethyleneimine instead of the polyamidine. The gel with equimolar amounts of the carboxyl group and the secondary amino group showed liquid-like fluidity with a G′ value of about 0.01 MPa at room temperature, which was attributed to the fact that a certain amount of the carboxyl group remained as its free form without salt formation, as evidenced by FTIR analysis. Copyright © 2014 Wiley Periodicals, Inc.
  • Reversible crosslinking and decrosslinking of polymers containing alcohol moiety using an acyclic bifunctional vicinal triketone
    Morio Yonekawa, Morio Yonekawa, Yoshio Furusho, Toshikazu Takata, Takeshi Endo
    Journal of Polymer Science, Part A: Polymer Chemistry 52 921-928 2014年04月
    In this article, we report reversible crosslinking and decrosslinking systems of commercially available alcoholic polymers, using a bifunctional vicinal triketone (bistriketone) as a crosslinking reagent. A small amount of the bistriketone (0.2 equiv of the tricarbonyl moiety relative to the OH group of the polymer) was added to a solution of poly(2-hydroxyethyl methacrylate) (PHEMA) in dimethyl sulfoxide (DMSO). After 4 days, the networked polymer was obtained as a yellow-colored gel in 97% yield. Conversely, the resulting gel could be decrosslinked by treatment with MeOH for 4 days to recover the original PHEMA in 94% yield as well as the bistriketone in 54% yield. The network formation and dissociation behaviors were investigated in detail by 1H NMR and size exclusion chromatography experiments. Similarly to PHEMA, reversible crosslinking and decrosslinking of poly(vinyl alcohol) were achieved by addition of the bistriketone and by treatment of the resulting gel with H2O/DMSO (1/9, v/v), respectively. © 2014 Wiley Periodicals, Inc.
  • Convenient synthesis of acyclic guanidines from isothiouronium iodides and amines without protection of the amino groups
    Naoto Aoyagi, Yoshio Furusho, Takeshi Endo
    Synlett 25 983-986 2014年01月
    Acyclic guanidines were obtained in one step by reaction of isothiouronium iodides with an equimolar amount of various amines in tetrahydrofuran. The reactions proceeded under ambient conditions without N-protection/deprotection to afford the corresponding substituted guanidines in quantitative yields. © Georg Thieme Verlag Stuttgart New York.
  • Supramolecular organogels formed through complementary double-helix formation
    Motonori Banno, Zong Quan Wu, Zong Quan Wu, Wataru Makiguchi, Yoshio Furusho, Yoshio Furusho, Eiji Yashima
    ChemPlusChem 79 35-44 2014年01月
    Optically active amidine ((R)-1) and achiral carboxylic acid (2) dimers with a m-terphenyl backbone linked by a 1,4-phenylene diacetylene unit form a double helix, (R)-1.2, through complementary amidinium-carboxylate salt bridges in THF. Upon the addition of poor solvents, such as n-hexane, the duplex forms an organogel as a result of supramolecular polymerization of the duplex by intermolecular rearrangement of the salt bridges. In sharp contrast, an analogous racemic duplex composed of achiral amidine residues and an optically active duplex linked by a shorter diacetylene unit with a higher binding affinity than that of (R)-1.2 does not show any gelation. The supramolecular fluorescent gels exhibit reversible thermoand chemoresponsive behavior. The chiroptical properties of the gels, the mechanism of gelation, and the amplification of helical chirality during the gelation of (R)-1.2 in the absence and presence of its enantiomeric counterpart, (S)-1.2, and a racemic duplex, consisting of achiral amidine and carboxylic acid dimers, were investigated by following changes in the absorption and circular dichroism spectra. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • Effective synthesis of cyclic carbonates from carbon dioxide and epoxides by phosphonium iodides as catalysts in alcoholic solvents
    Naoto Aoyagi, Yoshio Furusho, Takeshi Endo
    Tetrahedron Letters 54 7031-7034 2013年12月
    Phosphonium iodides effectively catalyzed the reaction of CO2 and epoxides under mild conditions such as ordinary pressure and ambient temperature in 2-propanol, and the corresponding five-membered cyclic carbonates were obtained in high yields. © 2013 Elsevier Ltd. All rights reserved.
  • Capture and release of CO2 by polyamidine
    Yoshio Furusho, Takeshi Endo
    Journal of Polymer Science, Part A: Polymer Chemistry 51 3404-3411 2013年08月
    By CO2 bubbling into an aqueous dimethyl sulfoxide solution, the polyamidine (Poly-Amd) prepared from hexamethylenediamine and triethyl orthoacetate was converted to the bicarbonate salt, Poly-AmdH·HCO 3, which formed aggregates. Conversely, the aggregates disappeared upon Ar bubbling to release the captured CO2, reverting to Poly-Amd completely. Polyethyleneimine (PEI) also reversibly captured and released CO2 molecules in solution by bubbling CO2 and Ar, respectively, in an alternate manner. No appreciable difference was observed between Poly-Amd and PEI in CO2 capture in solution. The binary system consisting of Poly-Amd and polyethylene glycol (PEG) captured CO 2 efficiently at ordinary pressure and reached a stationary state within 200 h, at which 66% of the amidine groups bound CO2 molecules, which was released upon exposure to a N2 flow. In contrast to the binary system with Poly-Amd, the binary system of PEI with PEG did not capture CO2 efficiently, and only 5.7% of the amino groups bound CO 2 molecules after 600 h. © 2013 Wiley Periodicals, Inc.
  • Fast equilibrium of zwitterionic adduct formation in reversible fixation-release system of CO2 by amidines under dry conditions
    Naoto Aoyagi, Naoto Aoyagi, Yoshio Furusho, Yoshihisa Sei, Takeshi Endo, Takeshi Endo
    Tetrahedron 69 5476-5480 2013年07月
    We investigated the fixation of CO2 by several amidines in solution and found that simple monocyclic amidines fixed CO2 under dry conditions to quantitatively afford the corresponding bicarbonates through hydrolysis of the zwitterionic adducts by adventitious water. In contrast, linear amidines did not form the bicarbonates under the same conditions, while 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) could not effectively trap CO 2. The CO2 fixed by the monocyclic amidines was quantitatively released by argon bubbling at a temperature as low as 60 C. The CO2 fixation-release process could be repeated several times without loss of the high efficiency. © 2013 Elsevier Ltd. All rights reserved.
  • Photocontrolled template-directed synthesis of complementary double helices assisted by amidinium-carboxylate salt bridge formation
    Junki Tanabe, Daisuke Taura, Hidekazu Yamada, Yoshio Furusho, Yoshio Furusho, Eiji Yashima
    Chemical Science 4 2960-2966 2013年07月
    The template-directed imine-bond forming reactions between chiral amidines or achiral carboxylic acids monomers bearing a formyl or an amino group at one end were remarkably accelerated 34- or 10-fold in chloroform in the presence of the corresponding optically inactive carboxylic acid dimer or optically active amidine dimer linked by a trans-azobenzene unit as the template, respectively. The cis-azobenzene-linked carboxylic acid template markedly slowed the monomer conversions, and hence a reversible photocontrolled dimerization was achieved by light-induced cis-trans isomerization upon alternative irradiation with UV and visible light. © 2013 The Royal Society of Chemistry.
  • Synthesis and X-ray structural analysis of an acyclic bifunctional vicinal triketone, its hydrate, and its ethanol-adduct
    Morio Yonekawa, Morio Yonekawa, Yoshio Furusho, Yoshihisa Sei, Toshikazu Takata, Takeshi Endo
    Tetrahedron 69 4076-4080 2013年05月
    We have synthesized and fully characterized an acyclic bifunctional vicinal tricarbonyl compound, its hydrate, and its ethanol-adduct, which could be converted to one another by utilizing the reversible addition-elimination of water or ethanol. X-ray single crystal study revealed that the bistriketone expanded and contracted by 10-30% in length during the interconversion. © 2013 Elsevier Ltd. All rights reserved.
  • Formation of a homo double helix of a conjugated polymer with carboxy groups and amplification of the macromolecular helicity by chiral amines sandwiched between the strands
    Wataru Makiguchi, Shinzo Kobayashi, Yoshio Furusho, Yoshio Furusho, Eiji Yashima
    Angewandte Chemie - International Edition 52 5275-5279 2013年05月
    Sandwiched amines: A π-conjugated polymer with carboxy groups self-associates to form a racemic double helix. In contrast, with chiral amines it forms a unique one-handed double helix, in which the strands sandwich pairs of chiral amines through cyclic hydrogen-bonding networks (see picture). The chiral information of the amines is transferred to the polymer backbones with remarkable amplification of the helical chirality. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • Synthesis of helically twisted [1 + 1]macrocycles assisted by amidinium-carboxylate salt bridges and control of their chiroptical properties
    Yuji Nakatani, Yoshio Furusho, Eiji Yashima
    Organic and Biomolecular Chemistry 11 1614-1623 2013年03月
    A series of optically active, helically twisted [1 + 1]macrocycles connected via o-, m-, and p-linkages (o-2, m-2, and p-2) was prepared from the corresponding linear duplexes stabilized by complementary amidinium-carboxylate salt bridges bearing two arms with terminal vinyl groups at both ends through the ring-closing metathesis reaction in the good yields of 67, 92, and 96%, respectively. The chiroptical properties of the macrocycles were dependent on the linker geometries and could be controlled by acid-base interactions and zinc coordination, the changes in which were detected by their CD and absorption spectral changes and fluorescence colors. © 2013 The Royal Society of Chemistry.
  • Convenient synthesis of cyclic carbonates from CO2 and epoxides by simple secondary and primary ammonium iodides as metal-free catalysts under mild conditions and its application to synthesis of polymer bearing cyclic carbonate moiety
    Naoto Aoyagi, Yoshio Furusho, Takeshi Endo
    Journal of Polymer Science, Part A: Polymer Chemistry 51 1230-1242 2013年03月
    Hydroiodides of secondary and primary amines effectively catalyzed the reaction of carbon dioxide and epoxides under mild conditions such as ordinary pressure and ambient temperature, to obtain the corresponding five-membered cyclic carbonates in moderate to high yields. Detailed investigation showed that the catalytic activity was highly affected by the counter anions of the ammonium salts; the iodides catalyzed efficiently the carbonate-forming reactions, whereas the bromide and chloride counterparts exhibited almost no catalysis. We also revealed that two important factors on the amine moieties that affected the catalytic reactions. First, the catalytic activity increased with increasing bulkiness of the substituents on the ammonium nitrogen atoms. Second, the catalysis became more efficient as the parent amines become more basic. Dicyclohexylammonium iodide was the best catalyst among the ammonium salts investigated in this study. As an application of this reaction system, we synthesized homo- and copolymers bearing epoxide pendant groups as substrates, which were converted with high efficiency into the corresponding homo- and copolymers bearing cyclic carbonate pendant groups under 1 atm at 45 °C. All polymers were easily purified simply by precipitation in water, and were isolated in high yields (>95%). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013. Copyright © 2012 Wiley Periodicals, Inc.
  • Radical ring-opening polymerization of five-membered cyclic vinyl sulfone using p-toluenesulfonyl halides
    Shimon Tanaka, Yoshio Furusho, Takeshi Endo
    Journal of Polymer Science, Part A: Polymer Chemistry 51 222-227 2013年01月
    Radical ring-opening polymerizations of a five-membered cyclic vinyl sulfone monomer, 2-vinylthiolane-1,1-dioxide (VTDO), was carried out by using p-toluenesulfonyl iodide (TosI) and bromide (TosBr) as radical initiators, and the corresponding ring-opened polymer (PVTDO) was obtained. Both TosI and TosBr were found to work as the radical initiators for the polymerization of VTDO in bulk. The use of TosI gave PVTDOs with a broad, multimodal distribution of molecular weight in low yields. When 10 mol % of TosBr was employed, the isolated yield of PVTDO reached 49%, and the obtained PVTDO had a relatively narrow, monomodal molecular weight distribution of 1.8 with an Mn of 4100. © 2012 Wiley Periodicals, Inc.
  • Chiral amplification in double-stranded helical polymers through chiral and achiral amidinium-carboxylate salt bridges
    Wataru Makiguchi, Shinzo Kobayashi, Yoshio Furusho, Eiji Yashima
    Polymer Journal 44 1071-1076 2012年11月
    A series of m-terphenyl-based random copolymers of chiral and achiral amidines, and their complementary homopolymers of achiral carboxylic acids were prepared by the copolymerization of a p-diiodobenzene derivative, with the diethynyl monomers containing a chiral or achiral amidine group and a carboxyl group using the Sonogashira coupling reaction. The obtained chiral/achiral amidine copolymers assembled into a double-stranded helical structure upon complexation with the complementary achiral homopolymer of carboxylic acids through interstrand amidiniumcarboxylate salt bridges. The complexes exhibited characteristic induced cotton effects in the π-conjugated main-chain chromophore regions, indicating that the interstrand duplexes possess a preferred-handed double-helical structure. The effect of the chiral and achiral amidine contents on the amplification of the helical chirality (the sergeants and soldiers effect) during the interstrand double-helix formation was investigated by comparing the cotton effect patterns and intensities of the duplexes with those of the corresponding all-chiral amidine-based double-helical polymer. © 2012 The Society of Polymer Science, Japan (SPSJ) All rights reserved.
  • Reversible cross-linking and de-cross-linking system of polystyrenes bearing the monohydrate structure of vicinal tricarbonyl group through water-alcohol exchange reactions at ambient conditions
    Morio Yonekawa, Yoshio Furusho, Takeshi Endo
    Macromolecules 45 6640-6647 2012年08月
    We describe in this paper reversible cross-linking and de-cross-linking system based on a polystyrene derivative bearing monohydrate structure of vicinal tricarbonyl groups with 1,6-hexanediol utilizing the direct water-alcohol exchange reactions on the vicinal tricarbonyl groups. By employing diphenylpropanetrione as a unit model compound for the polymer, we have demonstrated that the water-alcohol exchange reactions could be carried out reversibly in both directions by changing solvents. Notably, the water-alcohol exchange reactions proceeded without any catalysts and under mild conditions. For example, an equimolar mixture of the hydrate of diphenylpropanetrione and benzyl alcohol in chloroform (0.5 M) reached equilibrium after standing at ambient temperature within 48 h, where the content ratio of the benzyl alcohol adduct increased up to 49%. The reaction rate and the position of the equilibrium were highly affected by the concentrations of the substrates as well as the reaction temperature. By virtue of the above characteristic features of the water-alcohol exchange reactions, the polystyrene derivative bearing monohydrate structure of vicinal tricarbonyl group (2.0 M) was cross-linked with 1,6-hexanediol (0.2 equiv of OH group to the tricarbonyl unit) in acetone at ambient temperature for 5 days to afford the networked polymer in almost quantitative yield. On the other hand, the networked polymer was treated with an excess of water at ambient temperature for 3 days to afford the original linear polymer in high yield as a result of de-cross-linking through the water-alcohol exchange reaction. The cross-linking and de-cross-linking behavior was also evidenced by SEC analysis of the reaction mixture. © 2012 American Chemical Society.
  • Synthesis and extension/contraction motion of spiroborate-based double-stranded helicates consisting of substituted oligophenol strands
    Kazuhiro Miwa, Kaori Shimizu, Heejun Min, Yoshio Furusho, Eiji Yashima
    Tetrahedron 68 4470-4478 2012年06月
    A new class of ortho- and meta-substituted tetraphenols at the terminal phenyl residues with a biphenylene unit in the middle were synthesized and the effect of the substitution position on the spiroborate-based double-stranded helicate formation with sodium borohydride was investigated. The ortho-substitution considerably hampered the spiroborate formation between the terminal biphenol units and the boron atoms, whereas the meta-substituted oligomers formed a double-stranded helicate bridged by spiroborate groups accommodating a sodium cation in the center, which displayed an extension and contraction motion triggered by the removal and addition of sodium ions in solution. © 2011 Elsevier Ltd. All rights reserved.
  • Thermodynamic and kinetic stabilities of complementary double helices utilizing amidinium-carboxylate salt bridges
    Hidekazu Yamada, Zong Quan Wu, Yoshio Furusho, Eiji Yashima
    Journal of the American Chemical Society 134 9506-9520 2012年06月
    A series of dimer strands consisting of m-terphenyl backbones bearing complementary chiral or achiral amidines and achiral carboxylic acid residues connected by various types of linkers, such as diacetylene, Pt(II)-acetylide, and p-diethynylbenzene linkages, were synthesized by a modular strategy, and their chiroptical properties on the complementary double helix formations were investigated by absorption, circular dichroism (CD), and 1H NMR spectroscopies. The thermodynamic and kinetic stabilities of the complementary double helices assisted by amidinium-carboxylate salt bridges are highly dependent on their linkages, and the thermodynamic analyses of the dimer duplexes revealed that the association constants increased in the order: Pt(II)-acetylide linker < p-diethynylbenzene linker < diacetylene linker, which is in agreement with the reverse order of their bulkiness. The substituents on the amidine groups were also found to affect the stabilities on the duplexes and the association constants increased in the order: isopropyl < (R)-1-phenylethyl < cyclohexyl. In addition, the introduction of electron-donating and/or electron-withdrawing substituents at the phenyl groups of the p-diethynylbenzene linkers connecting the amidine and carboxylic acid units, respectively, tends to stabilize the complementary double helices, especially in polar solvents, such as DMSO, due to the attractive charge-transfer interactions between the aromatic linkers, although the salt bridge formation is hampered in DMSO. Furthermore, the kinetic analyses of the chain exchange reactions for the duplexes bearing diacetylene and p-diethynylbenzene linkages showed that these were slow processes with negative ΔS ‡ values, meaning that the chain exchange reactions proceed via direct exchange pathways. In contrast, those for the duplexes bearing Pt(II)-acetylide linkages were fast processes supported by positive ΔS ‡ values, suggesting that the chain exchange reactions proceed via dissociation-exchange ones. The helix-inversion kinetics investigated for the racemic dimer duplexes composed of achiral amidines based on variable-temperature 1H NMR measurements indicated that the barriers for the helix-inversion increased in the order: Pt(II)-acetylide linker, p-diethynylbenzene linker < diacetylene linker. © 2012 American Chemical Society.
  • Diastereoselective imine-bond formation through complementary double-helix formation
    Hidekazu Yamada, Yoshio Furusho, Eiji Yashima
    Journal of the American Chemical Society 134 7250-7253 2012年05月
    Optically active amidine dimer strands having a variety of chiral and achiral linkers with different stereostructures are synthesized and used as templates for diastereoselective imine-bond formations between two achiral carboxylic acid monomers bearing a terminal aldehyde group and racemic 1,2-cyclohexanediamine, resulting in a preferred-handed double helix stabilized by complementary salt bridges. The diastereoselectivity of the racemic amine is significantly affected by the chirality of the amidine residues along with the rigidity and/or chirality of the linkers in the templates. NMR and kinetic studies reveal that the present imine-bond formation involves a two-step reversible reaction. The second step involves formation of a preferred-handed complementary double helix assisted by the chiral amidine templates and determines the overall reaction rate and diastereoselectivity of the amine. © 2012 American Chemical Society.
  • Remarkably efficient catalysts of amidine hydroiodides for the synthesis of cyclic carbonates from carbon dioxide and epoxides under mild conditions
    Naoto Aoyagi, Yoshio Furusho, Takeshi Endo
    Chemistry Letters 41 240-241 2012年03月
    Hydroiodides of amidines effectively catalyzed the reaction of CO 2 and epoxides under mild conditions such as ordinary pressure and ambient temperature, and the corresponding 5-membered cyclic carbonates were obtained in moderate to high yields. © 2012 The Chemical Society of Japan.
  • Synthesis and helical structure of spiroborate-based double-stranded helicate with oligophenol strands bearing bipyridine units
    Yoshio Furusho, Kazuhiro Miwa, Ryo Asai, Eiji Yashima
    Chemistry - A European Journal 17 13954-13957 2011年12月
    Double wrapping: A new spiroborate-based double-stranded helicate was prepared from tetraphenol strands with a bipyridine unit in the middle and NaBH 4. The X-ray single-crystallographic analysis revealed that the helicate adopts a double helical structure, in which the two Na cations with a very short distance of 3.1 Å (see figure), were held in the center of the complex. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • Synthesis and optical resolution of a Cu(i) double-stranded helicate with ketimine-bridged tris(bipyridine) ligands
    Yoshio Furusho, Yoshio Furusho, Yoshio Furusho, Hidetoshi Goto, Hidetoshi Goto, Ken Itomi, Hiroshi Katagiri, Hiroshi Katagiri, Toyoharu Miyagawa, Toyoharu Miyagawa, Eiji Yashima, Eiji Yashima
    Chemical Communications 47 9795-9797 2011年09月
    A tetranuclear Cu(i) double-stranded helicate was synthesized from ketimine-bridged tris(bipyridine) ligands and Cu(i) ions, and the racemate was successfully resolved by diastereomeric salt formation using an optically pure phosphate anion followed by anion exchange with NaPF6 without racemization. © 2011 The Royal Society of Chemistry.
  • Synthesis of complementary double-stranded helical oligomers through chiral and achiral amidinium-carboxylate salt bridges and chiral amplification in their double-helix formation
    Hiroshi Ito, Hiroshi Ito, Masato Ikeda, Masato Ikeda, Takashi Hasegawa, Takashi Hasegawa, Yoshio Furusho, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Journal of the American Chemical Society 133 3419-3432 2011年03月
    A series of complementary molecular strands from 2-mer to 5-mer that are composed of m-terphenyl units bearing chiral/achiral amidine or achiral carboxyl groups linked via Pt(II) acetylide complexes were synthesized by sequential stepwise reactions, and their chiroptical properties on the double-helix formation were investigated by circular dichroism (CD) and 1H NMR spectroscopies. In CHCl3, the "all-chiral" amidine strands consisting of (R)- or (S)-amidine units formed preferred-handed double helices with the complementary achiral carboxylic acid strands through the amidinium-carboxylate salt bridges, resulting in characteristic induced CDs in the Pt(II) acetylide complex regions, indicating that the chiral substituents on the amidine units biased a helical sense preference. The Cotton effect patterns and intensities were highly dependent on the molecular lengths. The complementary double-helix formation was also explored using the chiral/achiral amidine strands with different sequences in which a chiral amidine unit was introduced at the center (center-chiral) or a terminus (edge-chiral) of the amidine strands. The effect of the sequences of the chiral and achiral amidine units on the amplification of chirality (the "sergeants and soldiers" effect) in the double-helix formation was investigated by comparing the CD intensities with those of the corresponding all-chiral amidine double helices with the same molecular lengths. Variable-temperature CD experiments of the all-chiral and chiral/achiral amidine duplexes demonstrated that the Pt(II)-linked complementary duplexes are dynamic and their chiroptical properties including the chirality transfer from the chiral amidine unit to the achiral amidine ones are significantly affected by the molecular lengths, sequences, and temperatures. On the basis of the above results together with molecular dynamics simulation results, key structural features of the Pt(II)-linked oligomer duplexes and the effect of the chiral/achiral amidine sequences on the amplification of chirality are discussed. © 2011 American Chemical Society.
  • Synthesis and function of double-stranded helical polymers and oligomers
    Yoshio Furusho, Eiji Yashima
    Macromolecular Rapid Communications 32 136-146 2011年01月
    The design and synthesis of artificial helical polymers and oligomers has attracted much interest, in connection with fascinating biological helices and their sophisticated functions as well as possible applications in novel chiral materials. The last half-century has seen a significant advancement in the synthesis of single-stranded helical polymers and oligomers, since the discovery of the helical structure of isotactic polypropylene. In contrast, the chemistry of double-stranded helical counterparts is still premature. This paper highlights our recent achievements in the synthesis, structures, and functions of double-stranded helical polymers and oligomers, stressing an important role of supramolecular chemistry in the design and synthesis of double helices with a controlled helical sense. This paper describes recent developments in the synthesis and functions of double helical polymers and oligomers, highlighting our recent results. Although the artificial double helices are still underdeveloped, significant progress in supramolecular chemistry has fortunately established a robust platform for generating a variety of supramolecular synthons. Now the time is ready to explore the chemistry of artificial double helices. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • A hetero-stranded double helix composed of m-diethynylbenzene-based complementary molecular strands stabilized by amidinium-carboxylate salt bridges
    Zong Quan Wu, Yoshio Furusho, Hidekazu Yamada, Eiji Yashima
    Chemical Communications 46 8962-8964 2010年12月
    A hetero-stranded double helix with a controlled helix sense was designed and synthesized from an optically active dimeric amidine and its complementary achiral dicarboxylic acid strand with conjugated m-diethynylbenzene backbones, being stabilized by the salt bridges. © 2010 The Royal Society of Chemistry.
  • Amidinium carboxylate salt bridges as a recognition motif for mechanically interlocked molecules: Synthesis of an optically active [2]catenane and control of its structure
    Yuji Nakatani, Yoshio Furusho, Eiji Yashima
    Angewandte Chemie - International Edition 49 5463-5467 2010年07月
    (Figure Presented) Salty catenane: An optically active [2]catenane was synthesized by utilizing an amidinium carboxylate salt bridge (see picture). The relative motion of the two macrocyclic components was completely controlled by an acid/base or Zn2+/cryptand couple. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • Ion-triggered spring-like motion of a double helicate accompanied by anisotropic twisting
    Kazuhiro Miwa, Yoshio Furusho, Eiji Yashima
    Nature Chemistry 2 444-449 2010年06月
    Molecules that extend and contract under external stimuli are used to build molecular machines with nanomechanical functions. But although common in biological systems, such extension and contraction motions with helical molecules have rarely been accompanied by unidirectional twisting in synthetic systems. Here we show that sodium ions can trigger the reversible anisotropic twisting of an enantiomeric double-stranded helicate, without racemization. An optically active helicate consisting of two tetraphenol strands bridged by two spiroborate groups sandwiches a sodium ion. On removal of the central sodium-through addition of a cryptand [2.2.1] in solution-the double helicate extends. Crystallographic and nuclear magnetic resonance studies reveal that the extended helicate is over twice as long as the initial molecule, and is twisted in the right-handed direction. Circular dichroism analysis suggests that the twisting doesn't affect the helicate's handedness. This anisotropic extension-contraction process is reversibly triggered by the successive addition and removal of sodium ions in solution. © 2010 Macmillan Publishers Limited. All rights reserved.
  • Complementary double helix formation through template synthesis
    Hidekazu Yamada, Yoshio Furusho, Yoshio Furusho, Hiroshi Ito, Eiji Yashima, Eiji Yashima
    Chemical Communications 46 3487-3489 2010年05月
    The dimerization of carboxylic acid derivatives bearing an amino or a formyl group at one end was significantly enhanced in benzene in the presence of an optically active amidine dimer to afford a complementary double helix stabilized with salt bridges. © 2010 The Royal Society of Chemistry.
  • Axle length effect on photoinduced electron transfer in triad rotaxane with porphyrin, [60]fullerene, and triphenylamine
    Atula S D Sandanayaka, Atula S D Sandanayaka, Hisahiro Sasabe, Yasuyuki Araki, Nobuhiro Kihara, Yoshio Furusho, Toshikazu Takata, Osamu Ito
    Journal of Physical Chemistry A 114 5242-5250 2010年04月
    Photoinduced multiple electron-transfer processes of a newly synthesized rotaxane with one acceptor and two donors are studied with the time-resolved fluorescence and absorption methods. In this rotaxane, zinc porphyrin (ZnP) with a crown-ether necklace is employed as a photosensitized electron donor; through the crown-ether, a short axle with C60 and triphenylamine (TPA) at both terminals is penetrating as an electron acceptor and a hole-shift, respectively (abbreviated as (ZnP;C60-(AS)-TPA) Rot). The time-resolved fluorescence and transient absorption measurements reveal that the through-space electron-transfer processes take place via the excited states of the ZnP unit to the spatially arranged C 60 moiety, giving the radical ion pair (ZnṖ+;C 60--(AS)-TPA)Rot in polar solvents. Consecutively, (ZnP;C60--(AS)-TPA ̇+)Rot is also generated by the through-space hole-shift between ZnP and TPA, in addition to the through-bond charge separation via the excited state of the C60 moiety. Both radial ion pairs have lifetimes of 320-420 ns, which are longer than those of the previously reported similar rotaxane with cationic longer axle (150-170 ns). © 2010 American Chemical Society.
  • Successive catalytic reactions specific to Pd-based rotaxane complexes as a result of wheel translation along the axle
    Norihito Miyagawa, Masahiro Watanabe, Takanori Matsuyama, Yasuhito Koyama, Toshiyuki Moriuchi, Toshikazu Hirao, Yoshio Furusho, Toshikazu Takata
    Chemical Communications 46 1920-1922 2010年03月
    Rotaxane-structure-specific Pd-catalyzed rearrangement of propargyl or allyl urethane groups to oxazolidinone moieties proceeded efficiently. The conversion took place successively by the translation of the wheel along the axle, thus providing a novel macrocyclic catalytic system. © The Royal Society of Chemistry 2010.
  • Double-stranded supramolecular assembly through salt bridge formation between rigid and flexible amidine and carboxylic acid strands
    Hiroki Iida, Munenori Shimoyama, Yoshio Furusho, Eiji Yashima
    Journal of Organic Chemistry 75 417-423 2010年01月
    (Chemical Equation Presented) A series of monomeric strands consisting of m-terphenyl backbones with chiral rigid C-linked (3) and flexible N-linked (5) formamidines and achiral carboxylic acid (4) and flexible carboxymethyl (6) residues were synthesized, and their duplex formations through amidinium-carboxylate salt bridges were investigated by NMR, circular dichroism (CD), and UV-visible spectroscopies. The salt bridge-derived duplex formation was largely dependent on the structures of the formamidine and carboxylic acid strands, and the C-linked formamidine strand 3 formed a more stable duplex with the complementary carboxylic acid strands (4 and 6) than did the flexibleN-linked formamidine strand 5. The single crystal X-ray analysis revealed that the duplex 5·4 has a skewed right-handed double helical structure. A complementary duplex dimer was also synthesized from the dimers of 5 and 4 joined by diacetylene linkers. Variable-temperature CD measurements indicated that the duplex possesses a dynamic double helical structure resulting from the flexible N-linked formamidine units. © 2009 American Chemical Society.
  • Axle charge effects on photoinduced electron transfer processes in rotaxanes containing porphyrin and [60]fullerene
    Hisahiro Sasabe, Hisahiro Sasabe, Atula S D Sandanayaka, Atula S D Sandanayaka, Nobuhiro Kihara, Nobuhiro Kihara, Yoshio Furusho, Yoshio Furusho, Toshikazu Takata, Toshikazu Takata, Yasuyuki Araki, Osamu Ito
    Physical Chemistry Chemical Physics 11 10908-10915 2009年11月
    Two rotaxanes containing zinc porphyrin (ZnP) with crown ether and [60]fullerene (C60) with cationic and neutral axles are synthesized. Optimized structures calculated by molecular orbital methods indicate that the rotaxane with an ammonium cation in the center of the axle has a shorter distance between the C60 and ZnP moieties than that of the rotaxane with a neutral axle because of acylation of the ammonium cation, which draws away the C60 and ZnP moieties by releasing the interaction with the crown ether. The charge-transfer interaction is revealed by absorption spectra for the rotaxane with a short distance, but not for the rotaxane with a long distance, which strongly affects the rates and efficiencies of photoinduced electron-transfer and energy-transfer processes via the excited singlet states of the ZnP and C60 moieties and their triplet states, as revealed by the time-resolved fluorescence and absorption measurements. The rate of the charge recombination of the radical ion pair of the rotaxane with a neutral axle is slower than that of the rotaxane with a cationic axle, due to the loose structure of the former rotaxane, which results from the long distance between the C60 anion radical and the ZnP cation radical. © the Owner Societies 2009.
  • Helical polymers: Synthesis, structures, and functions
    Eiji Yashima, Katsuhiro Maeda, Hiroki Lida, Yoshio Furusho, Kanji Nagai, Kanji Nagai
    Chemical Reviews 109 6102-6211 2009年11月
    The synthesis process, structures and functions of helical polymers was reviewed. The static and dynamic helical polymers differ through their helix inversion barriers. As a consequence, the former helical conformations are locked during the polymerization under kinetic control, while the latter helical conformations are thermodynamically controlled. It has also been studied that helical conformations of dynamic helical polymers can also be locked, as demonstrated by the unique memory effect observed in dynamic helical poly(phenylacetylene)s and poly(phenyl isocyanide)s induced by chiral guest molecules. In addition, either static or dynamic helical polymers with an excess single-handedness can be prepared by the polymerization of monomers with the identical framework, but bearing different substituents. Apart from the breadth of single-stranded helical polymers and oligomers, the design and synthetic strategies for doublestranded helical polymers and oligomers remain limited, regardless of the natural model, the double-helical DNA.
  • Development of synthetic double helical polymers and oligomers
    Yoshio Furusho, Eiji Yashima
    Journal of Polymer Science, Part A: Polymer Chemistry 47 5195-5207 2009年10月
    There is growing interest in the design and synthesis of artificial helical polymers and oligomers, in connection with biological importance as well as development of novel chiral materials. Since the discovery of the helical structure of isotactic polypropylene, a significant advancement has been achieved for synthetic polymers and oligomers with a single helical conformation for about half a century. In contrast, the chemistry of double helical coun-terparts is still premature. This short review highlights the recent advances in the synthesis, structures, and functions of double helical polymers and oligomers, featuring an important role of supramolecular chemistry in the design and synthesis of double helices. Although the artificial, double helices reported to date are still limited in number, recent advancement of supramolecular chemistry provides plenty of structural motifs for new designs. Therefore, artificial double helices hold great promise as a new class of compounds. © 2009 Wiley Periodicals, Inc.
  • Double helix formation of poly(m-phenylene)s bearing achiral oligo(ethylene oxide) pendants and transformation into an excess of one-handed single helix through cholate binding in water
    Teng Ben, Teng Ben, Yoshio Furusho, Yoshio Furusho, Hidetoshi Goto, Hidetoshi Goto, Kazuhiro Miwa, Eiji Yashima, Eiji Yashima
    Organic and Biomolecular Chemistry 7 2509-2512 2009年07月
    A water-soluble poly(m-phenylene) bearing an achiral oligo(ethylene oxide) chain at the 5-position was synthesized by the Ni(0)-mediated homo-coupling polycondensation of a 3,5-dibromophenol monomer. The poly(m-phenylene) adopted a single helical conformation in protic media and self-assembled into a double helix in water through aromatic interaction, while it took a random-coil conformation in chloroform. Upon the addition of sodium cholate in water, the double helical poly(m-phenylene) was transformed into single strands, which bound the cholate molecules to form an excess of one-handed single helix. © The Royal Society of Chemistry 2009.
  • Double helix formation of oligoresorcinols in water: Thermodynamic and kinetic aspects
    Hidetoshi Goto, Hidetoshi Goto, Hidetoshi Goto, Yoshio Furusho, Yoshio Furusho, Yoshio Furusho, Yoshio Furusho, Kazuhiro Miwa, Kazuhiro Miwa, Kazuhiro Miwa, Kazuhiro Miwa, Eiji Yashima, Eiji Yashima, Eiji Yashima, Eiji Yashima
    Journal of the American Chemical Society 131 4710-4719 2009年04月
    We previously reported that the oligoresorcinols formed double-stranded helices in neutral water through interstrand aromatic interactions. In the present study, we synthesized a new series of oligomers from the 2mer to the 15mer to explore the thermodynamics, kinetics, and mechanism of the double helix formation of the oligoresorcinols in water. The double helix formation was dependent on the chain length of the oligomers and significantly affected by solvent, pH, salt, and temperature. The free energy change (-?G) for the double helix formation linearly increased with the chain length from the 4mer to the 11mer (ΔΔG = -0.94 kcal mol -1 unit -1), whereas it did not change for the oligomers longer than the 11 mer. The van't Hoff analysis of the 9mer revealed that the double helix formation was an enthalpically driven process (ΔH = -27 ± 1.5 kcal mol -1 and ΔS = -70 ± 5 cal mol -1 K -1), which was consistent with the upfield shifts in the 1H NMR spectra and the hypochromicity of the absorption spectra as a result of the interstrand aromatic interactions in water. Furthermore, the kinetic analysis of the chain exchange reaction between the double helices of the optically active and optically inactive 11mers revealed a small ΔS ‡, suggesting that the chain exchange proceeds not via the dissociation-association pathway, but via the direct exchange pathway. © 2009 American Chemical Society.
  • Helicity induction on water-soluble oligoresorcinols in alkaline water and their application to chirality sensing
    Hidetoshi Goto, Hidetoshi Goto, Yoshio Furusho, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Chemical Communications 1650-1652 2009年03月
    Oligoresorcinol oligomers were found to adopt a single-stranded helical conformation in alkaline water through intramolecular hydrogen bonds, of which a helix-sense bias was induced by the addition of water-soluble chiral compounds, such as ammonium salts, amines and alcohols. © The Royal Society of Chemistry.
  • Polyrotaxane networks formed via rotaxanation utilizing dynamic covalent chemistry of disulfide
    Tuya Bilig, Tomoya Oku, Yoshio Furusho, Yasuhito Koyama, Shigeo Asai, Toshikazu Takata
    Macromolecules 41 8496-8503 2008年11月
    Polyrotaxane networks were synthesized from a mixture of poly(crown ether)s (2-5) as a trunk polymer and dumbbell-shaped bifunctional secondary ammonium salt 6 bearing a disulfide linkage and bulky end caps as a cross-linking agent in the presence of a catalytic amount of benzenethiol via a reversible thiol-disulfide interchange reaction. Trunk polymers 2-4 were prepared by copolymerization of bis(hydroxymethyl)dibenzo-24-crown-8-ether 1 and comonomers. Poly(crown ether) 5 bearing a poly(tetrahydrofuran) (PTHF) spacer was also synthesized from 1 and PTHF with 4,4′-methylenebis(phenyl isocyanate) (MDI) in N,N-dimethylacetamide (DMAc) at room temperature. The treatment of these poly(crown ether)s (2-5) with axle component 6 in the presence of benzenethiol gave the corresponding polyrotaxane networks (7-10) in quantitative yields. We confirmed the cross-linking process by monitoring the 1H NMR spectral change during the polymerization. Thermal properties, swelling, and dynamic viscoelasticity of these polyrotaxane networks were evaluated. Polyrotaxane network 10 bearing 5 afforded higher swelling and elasticity than those of other networks because of the flexibility of the trunk polymer as wheel components. © 2008 American Chemical Society.
  • Sequence- and chain-length-specific complementary double-helix formation
    Hiroshi Ito, Yoshio Furusho, Yoshio Furusho, Toshihide Hasegawa, Eiji Yashima, Eiji Yashima
    Journal of the American Chemical Society 130 14008-14015 2008年10月
    The artificial sequential strands consisting of two, three, or four m-terphenyl groups joined by diacetylene linkers with complementary binding sites, either the chiral amidine (A) or achiral carboxyl (C) group, were synthesized in a stepwise manner. Using circular dichroism and 1H NMR spectroscopies along with liquid chromatography, we showed that, when three dimeric molecular strands (AA, CC, and AC) or six trimeric molecular strands (AAA, CCC, AAC, CCA, ACA, and CAC) were mixed in solution, the complementary strands were sequence-specifically hybridized to form one-handed double-helical dimers AA-CC and (AC)2 or trimers AAA-CCC, AAC-CCA, and ACA-CAC, respectively, through complementary amidinium-carboxylate salt bridges. Upon the addition of CCA to a mixture of AAA, AAC, and ACA, the AAC-CCA double helix was selectively formed and then isolated from the mixture by chromatography. Moreover, the homo-oligomer mixtures of amidine or carboxylic acid from the monomers to tetramers (A, AA, AAAA, C, CC, and CCCC) assembled with a precise chain length specificity to form A-C, AA-CC, and AAAA-CCCC, which were separated by chromatography. © 2008 American Chemical Society.
  • Single- and double-stranded helical polymers: Synthesis, structures, and functions
    Eiji Yashima, Eiji Yashima, Katsuhiro Maeda, Katsuhiro Maeda, Yoshio Furusho, Yoshio Furusho
    Accounts of Chemical Research 41 1166-1180 2008年09月
    Biological macromolecules, such as DNA and proteins, possess a unique and specific ordered structure, such as a right-handed double helix or a single α-helix. Those structures direct the sophisticated functions of these molecules in living systems. Inspired by biological helices, chemists have worked to synthesize polymers with controlled helicity, not only to mimic the biological helices but also to realize their functions. Although numerous synthetic polymers that fold into a single-handed helix have been reported, double-stranded helical polymers are almost unavailable except for a few oligomers. In addition, the exact structures of most helical polymers remain obscure. Therefore, the development of a conceptually new method for constructing double-stranded helical polymers and a reliable method for unambiguously determining the helical structures are important and urgent challenges in this area. In this Account, we describe the recent advances in the synthesis, structures, and functions of single- and double-stranded helical polymers from our group and others and provide a brief historical overview of synthetic helical polymers. We found unique macromolecules that fold into a preferred-handed helix through noncovalent bonding interactions with spedfic chiral guests. During the noncovalent helidty induction process, these guest molecules significantly amplified chirality in a dynamic helical polymer. During the intensive exploration of the helidty induction mechanism, we observed an unusual macromolecular helical memory in dynamic helical polymers. Furthermore, we found that rigid-rod helical poly(phenylacetylene)s and poly(phenyl isocyanide)s showing a cholesteric or smectic liquid crystal self-assemble to form two-dimensional crystals with a controlled helical conformation on solid substrates upon exposure to solvent vapors. We visualized their helical structures including the helical pitch and handedness by atomic force microscopy (AFM). We propose a modular strategy to construct complementary double helices by employing chiral amidinium-carboxylate salt bridges with m-terphenyl backbones. The double-stranded helical structures were characterized by circular dichroism in solution and X-ray diffraction of the crystals or the direct AFM observations. Serendipitously, we found that oligoresorcinols self-assemble into well-defined double helices resulting from interstrand aromatic stacking in water. These oligoresorcinols bound cyclic and linear oligosaccharides in water to form rotaxanes and hetero-double helices, respectively. The examples presented in this Account demonstrate the notable progress in the synthesis and structural determination of helical polymers including single- and double-stranded helices. Not only do we better understand the prindple underlying the generation of helical conformations, but we have also used the knowledge of these unique helical structures to develop novel helical polymers with specific functions. © 2008 American Chemical Society.
  • Double-stranded helical polymers consisting of complementary homopolymers
    Takeshi Maeda, Yoshio Furusho, Yoshio Furusho, Shin Ichiro Sakurai, Jiro Kumaki, Kento Okoshi, Eiji Yashima, Eiji Yashima
    Journal of the American Chemical Society 130 7938-7945 2008年06月
    Two complementary homopolymers of chiral amidines and achiral carboxylic acids with m-terphenyl-based backbones were synthesized by the copolymerization of a p-diiodobenzene derivative with the diethynyl monomers bearing a chiral amidine group and a carboxyl group using the Sonogashira reaction, respectively. Upon mixing in THF, the homopolymer strands assembled into a preferred-handed double helix through interstrand amidinium-carboxylate salt bridges, as evidenced by its absorption, circular dichroism, and IR spectra. In contrast, when mixed in less polar solvents, such as chloroform, the complementary strands kinetically formed an interpolymer complex with an imperfect double helical structure containing a randomly hybridized cross-linked structure, probably because of strong salt bridge formations. This primary complex was rearranged into the fully double helical structure by treatment with a strong acid followed by neutralization with an amine. High-resolution atomic force microscopy revealed the double-stranded helical structure and enabled the determination of the helical sense. © 2008 American Chemical Society.
  • Synthesis and helix formation of poly(m-phenylene)s bearing optically active oligo(ethylene oxide) side chains in protic media
    Ben Teng, Ben Teng, Hidetoshi Goto, Kazuhiro Miwa, Hiroaki Goto, Kazuhide Morino, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Macromolecules 41 4506-4509 2008年06月
    The synthesis and the single-helix formation of the poly(m-phenylene) bearing an optically active oligo(ethylene oxide) chain at 5-position in protic media have been reported. Poly(m-phenylene), P1H, was prepared by the nickel-mediated homocoupling polymerization of the 3,5-dibromophenol monomer in N,N-dimethylformamide (DMF). The single-helical conformation of P1H was investigated by a molecular mechanics calculation study on a 5-methoxy-m-phenylene 30-mers, PMP30. It was been confirmed that P1H adopts a single-helical conformation with the aid of aromatic interactions in protic media, indicating that the poly(m-phenylene) is a useful structural motif for helical foldamers. As P1H is soluble and forms a single helix in protic media containing water, it is expected to bind certain water-soluble biomolecules with some recognition.
  • Synthesis and function of artificial double helices
    Yoshio Furusho, Eiji Yashima
    Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry 65 1121-1133 2007年11月
    This account mainly describes the synthesis and functions of novel artificial double helices recently developed by our group. We have proposed the first design rationale for artificial double helices with a controlled helicity by employing chiral amidinium-carboxylate salt bridges with m-terphenyl ligands, and synthesized several artificial double helices together with triple- and quadruple-stranded helices. An artificial double helix bearing Pt(II)-acetylide complex moieties has proven effective as a catalyst for the asymmetric cyclopropanation, demonstrating that the chiral space provided by double helices can be effective for asymmetric catalytic reactions. Furthermore, we have serendipitously discovered a spiroborate-based double helicate bearing oligophenol strands and water-soluble double helices of oligoresorcinols. The oligoresorcinol double helices bound cyclic and linear oligosaccharides in water to form rotaxanes and hetero-double helices, respectively, with a remarkable selectivity for the glucosidic linkage patterns and chain lengths.
  • Enantioselective synthesis of complementary double-helical molecules that catalyze asymmetric reactions
    Takashi Hasegawa, Takashi Hasegawa, Yoshio Furusho, Hiroshi Katagiri, Eiji Yashima, Eiji Yashima
    Angewandte Chemie - International Edition 46 5885-5888 2007年08月
    Two twisted: Optically active double helices were synthesized through a twist-sense bias induced by a chiral phosphine ligand on one of the complementary metallostrands followed by a ligand-exchange reaction with an achiral bidentate ligand, which replaces the chiral ligand, to bridge the two strands. Furthermore, the double helices can efficiently catalyze asymmetric cyclopropanation. (Figure Presented). © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.
  • Photoresponsive double-stranded helices composed of complementary strands
    Yoshio Furusho, Yoshie Tanaka, Takeshi Maeda, Masato Ikeda, Eiji Yashima, Eiji Yashima
    Chemical Communications 3174-3176 2007年08月
    A photoresponsive single-handed double helical supramolecule composed of complementary strands bearing azobenzene moieties underwent a reversible trans-cis-isomerization regulated by photoirradiation, resulting in a change in its molecular length. © The Royal Society of Chemistry.
  • Double helical oligoresorcinols specifically recognize oligosaccharides via heteroduplex formation through noncovalent interactions in water
    Hidetoshi Goto, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Journal of the American Chemical Society 129 9168-9174 2007年07月
    We report on the oligosaccharide recognition through noncovalent interactions in water based on a unique supramolecular homoduplex-to- heteroduplex transformation of the oligoresorcinol nonamer as a fully artificial receptor. The oligoresorcinol forms a double helix in water, which unravels and entwines upon complexation with specific oligosaccharides with a particular chain length and glucosidic linkage pattern, thus generating the heteroduplex with an excess one-handed helical conformation that can be readily monitored and further quantified by absorption, circular dichroism, and NMR spectroscopies. © 2007 American Chemical Society.
  • Multicomponent cylindrical assemblies driven by amidinium-carboxylate salt-bridge formation
    Hiroshi Katagiri, Yoshie Tanaka, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Angewandte Chemie - International Edition 46 2435-2439 2007年06月
    An unexpected twist: Three chiral amidine-functionalized strands and two benzenetricarboxylic acid molecules self-assemble into a 3:2 cylindrical complex with controlled helicity through amidinium-carboxylate salt-bridge formation. A related 4:2 cylindrical complex composed of two zinc porphyrin units and four chiral strands twists into one direction upon encapsulation of 4,4′-bipyridine through coordination to the zinc centers (see picture). (Figure Presented). © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.
  • Molecular design and synthesis of artificial double helices
    Yoshio Furusho, Eiji Yashima
    Chemical Record 7 1-11 2007年04月
    This account describes novel artificial double helices recently developed by our group. We have designed and synthesized the double helices consisting of two complementary, m-terphenyl-based strands that are intertwined through chiral amidinium-carboxylate salt bridges. Due to the chiral substituants on the amidine groups, the double helices adopted an excess one-handed helical conformation in solution as well as in the solid state. By extending the modular strategy, we have synthesized double helices bearing Pt(II) linkers, which underwent the double helix-to-double helix transformations through the chemical reactions of the Pt(II) complex moieties. In addition, artificial double-stranded metallosupramolecular helical polymers were constructed by combining the salt bridges and metal coordination. In contrast to the design-oriented double helices based on salt bridges, we have serendipitously developed a spiroborate-based double helicate bearing oligophenol strands. The optical resolution of the helicate was successfully attained by a diastereomeric salt formation. We have also unexpectedly found that oligoresorcinols consisting of a very simple repeating unit self-assemble into double helices with the aid of aromatic interactions in water. Furthermore, a bias in the twist sense of the double helices can be achieved by incorporating chiral substituents at both ends of the strands. © 2007 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.
  • Supramolecular control of unwinding and rewinding of a double helix of oligoresorcinol using cyclodextrin/adamantane system
    Hidetoshi Goto, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Journal of the American Chemical Society 129 109-112 2007年01月
    The double helix of the oligoresorcinol nonamer formed in water was unwound by β-cyclodextrin (β-CD), and the resulting single strands of the nonamer threaded the β-CD to form a twisted [3]-pseudorotaxane with a controlled helicity. Upon the addition of an adamantane, the single strand of the oligoresorcinol nonamer was expelled out of the β-CD wheels, thus regenerating the double helix. This supramolecularly controlled, reversible unwinding and rewinding of the double helix is unique and can be readily monitored by spectroscopic techniques. © 2007 American Chemical Society.
  • Application of soluble poly(phenylenevinylene) wrapped in amylose to organic light-emitting diodes
    Shunsuke Nishino, Tatsuo Mori, Tatsuo Mori, Sayaka Tanahara, Katsuhiro Maeda, Masato Ikeda, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Molecular Crystals and Liquid Crystals 471 29-38 2007年01月
    Non-substituted poly(phenylenevinylene) (PPV) is an insoluble material. Ikeda et al. synthesized Amylose-PPV (APPV), which is PPV wrapped in amylose, by applying precursor route synthesis of PPV in the presence of amylase; APPV is soluble in dimethylsulfoxide. Comparison of the absorbance and the PL spectrum of APPV film with those of other organic films indicated the PL efficiency of APPV film as 0.28-0.43. The PL efficiency of PPV film is 0.27. Therefore, the amylose wrapping might improve the PL efficiency of PPV. The OLEDs emitted a green light when the OLEDs were fabricated with APPV as an emitting layer.
  • Construction of double-stranded metallosupramolecular polymers with a controlled helicity by utilizing amidinium-carboxylate salt bridges
    Yoshio Furusho, Masato Ikeda, Takashi Hasegawa, Takashi Hasegawa, Yoshie Tanaka, Eiji Yashima, Eiji Yashima
    Polymer Preprints, Japan 55 5243-5244 2006年12月
    We designed and synthesized a supramolecular duplex comprised of complementary m-terphenyl-based strands bearing a chiral amidine or achiral carboxylic acid together with two pyridine groups at the four ends. Supramolecular polymerization of the duplex with cis-PtPh2(dmso) 2 in 1,1,2,2-tetrachloroethane produced the double-stranded metallosupramolecular polymer with a controlled helicity of which the two complementary metallostrands are intertwined through the amidinium-carboxylate salt bridges. The structures and hydrodynamic dimensions of the metallosupramolecular polymers were characterized by 1H NMR, diffusion ordered NMR, dynamic light scattering, absorption, and CD measurements. The polymeric structure was also visualized by atomic force microscopy.
  • Photoinduced electron transfer processes in three component rotaxanes with porphyrins, [60]fullerene and triphenylamine
    Hisahiro Sasabe, Yoshio Furusho, Atula S D Sandanayaka, Yasuyuki Araki, Nobuhiro Kihara, Kazuhiko Mizuno, Akiya Ogawa, Toshikazu Takata, Osamu Ito
    Journal of Porphyrins and Phthalocyanines 10 1346-1359 2006年12月
    Electron transfer processes occurring through-space and through-bond were studied for novel mechanically linked triad [2]rotaxanes, which contain a porphyrin (MP) unit as a pendant and [60]fullerene (C60) and triphenylamine (TPA) moieties as stopper groups at the axle ends (abbreviated as (MP;C60-TPA)rot+ with MP = H2P or ZnP. The photophysical properties were investigated by means of time-resolved fluorescence and transient absorption measurements with changing solvent polarity. The charge separation took place mainly via (1MP*; C60-TPA)rol+ and (MP;1C60*- TPA)rot+ in polar solvents. Within the charge-separated states of triads (MP;C60-TPA)rol+, hole-shift and/or back electron transfer took place competitively. The lifetime of the charge separation state of (ZnP;C60-TPA)rol+ was similar to that of dyad (C 60-TPA)rol+ (140 ns in dimethylformamide), whereas that of (H2P;C60-TPA)rol+ was as long as 230 ns, suggesting two final charge separation states such as (MP;C60•-TPA•+)rot+ and (MP •+;C60•--TPA)rot+ depending on the kind of porphyrin. Copyright © 2006 Society of Porphyrins & Phthalocyanines.
  • A luminescent poly(phenylenevinylene)-amylose composite with supramolecular liquid crystallinity
    Masato Ikeda, Yoshio Furusho, Kento Okoshi, Sayaka Tanahara, Katsuhiro Maeda, Shunsuke Nishino, Tatsuo Mori, Eiji Yashima, Eiji Yashima
    Angewandte Chemie - International Edition 45 6491-6495 2006年10月
    (Chemical Equation Presented) Going straight: A luminescent composite of poly(p-phenylenevinylene) (PPV) and amylose was synthesized by direct polymerization of the precursor monomer in aqueous media in the presence of amylose. The PPV-amylose composite consists of a rigid-rod PPV segment threaded into a flexible amylose tube and self-assembles into liquid-crystalline phases. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.
  • Self-assembly of multinuclear complexes with enantiomerically pure chiral binaphthoxy imine ligands: Effect of the alkyl spacer connecting two binaphthyl units on the metal binding
    Takeshi Maeda, Yoshio Furusho, Yoshio Furusho, Motoo Shiro, Toshikazu Takata, Toshikazu Takata
    Chirality 18 691-697 2006年09月
    Metal complexing behavior of enantiomerically pure α,ω- diiminoalkanes possessing the two terminal binaphthyl units (L1 and L2) was studied. The ligands L1 and L2 were prepared by the reaction of optically pure 2′-butoxy-3-formyl-2-hydroxy-1,1′- binaphthyl with propane and pentane diamines. Reactions of L1 and L2 with equimolar amount of Cu(OAc)2 afforded quantitatively multinuclear complexes 1. The structure of 1 was confirmed by MALDI-TOF MS spectroscopy, X-ray single-crystal-structure analysis, and UV/vis and CD spectroscopic analyses. The reaction of L1 having a 1,3-propanediyl spacer resulted in the formation of a self-assembled product, which was assigned as enantiopure trinuclear circular helicate 1a, while the ligand having a 1,5-pentanediyl spacer L2 gave a different self-assembled product, dinuclear side-by-side complex 1b. The circular dichroism (CD) spectrum of 1a in solution showed intense Cotton effects in both the π-π* transition of the naphthalene units and the LMCT region of the N,O-chelate moieties. The CD spectrum of 1b was completely different from that of 1a; in particular the Cotton effects in the LMCT region were very weak, contrary to those of 1a. These results suggest that 1a retains some chirality induced on the N,O-chelating moieties even in solution, while the induced chirality on the N,O-chelating moieties in 1b is not very significant, being consistent with the consequences of the X-ray single-crystal-structure studies. © 2006 Wiley-Liss, Inc.
  • Double helix-to-double helix transformation, using platinum(II) acetylide complexes as surrogate linkers
    Yoshio Furusho, Yoshie Tanaka, Eiji Yashima, Eiji Yashima
    Organic Letters 8 2583-2586 2006年06月
    We describe novel optically active double helices consisting of complementary strands stabilized by amidinium-carboxylate salt bridges. The m-terphenyl groups of each strand are joined by trans-Pt(II) acetylide complexes with pendant PPh3 ligands as the surrogate linker, which converts to cis counterparts by a ligand exchange reaction with cis-1,2- bis(diphenylphosphino)ethylene, resulting in the formation of double helices with different structures. Subsequent iodine-promoted reductive elimination on the Pt(II) atoms generates the fully organic, enantiomerically pure double helices. © 2006 American Chemical Society.
  • Oligoresorcinols fold into double helices in water
    Hidetoshi Goto, Hiroshi Katagiri, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Journal of the American Chemical Society 128 7176-7178 2006年06月
    We report the first double helices with a controlled helicity in water based on oligoresorcinols as a new, simplest water-soluble structural motif. The molecular strands of the oligoresorcinols self-assemble into double helices with the aid of aromatic interactions in water as characterized by 1H NMR and absorption spectroscopies together with the X-ray crystallographic study of the pentamer. The double helix formation is sensitive to the chain length, solvent composition, and temperature. Moreover, a bias in the screw sense of the double helices was achieved by covalently attaching chiral substituents to both ends of the molecular strands. Copyright © 2006 American Chemical Society.
  • Construction of double-stranded metallosupramolecular polymers with a controlled helicity by combination of salt bridges and metal coordination
    Masato Ikeda, Yoshie Tanaka, Takashi Hasegawa, Takashi Hasegawa, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Journal of the American Chemical Society 128 6806-6807 2006年05月
    We describe the construction of the first double-stranded metallosupramolecular helical polymers. We designed and synthesized a supramolecular duplex comprised of complementary m-terphenyl-based strands bearing a chiral amidine or achiral carboxylic acid together with two pyridine groups at the four ends. Supramolecular polymerization of the duplex with cis-PtPh2(DMSO)2 in 1,1,2,2-tetrachloroethane produced the double-stranded metallosupramolecular polymer with a controlled helicity of which the two complementary metallostrands are intertwined through the amidinium-carboxylate salt bridges. The structures and hydrodynamic dimensions of the metallosupramolecular polymers were characterized by 1H NMR, diffusion-ordered NMR, dynamic light scattering, absorption, and CD measurements. The polymeric structure was also visualized by atomic force microscopy. Copyright © 2006 American Chemical Society.
  • Prolongation of the lifetime of the charge-separated state at low temperatures in a photoinduced electron-transfer system of [60]fullerene and ferrocene moieties tethered by rotaxane structures
    G. Abraham Rajkumar, Atula S D Sandanayaka, Kei Ichiro Ikeshita, Yasuyuki Araki, Yoshio Furusho, Toshikazu Takata, Osamu Ito
    Journal of Physical Chemistry B 110 6516-6525 2006年05月
    A rotaxane tethering both fullerene (C60) and ferrocene (Fc) moieties (abbreviated as (C60;Fc)rotax+) was synthesized in a good yield by the urethane end-capping of pseudorotaxane based on the crown ether -secondary amine motif. In (C60;Fc)rotax+, the C60 group serving as an electron acceptor is attached to the crown ether wheel, through which the axle with a Fc group acting as an electron donor on its end penetrates. The intrarotaxane photoinduced energy-transfer and electron-transfer processes between C60 and Fc in (C 60;Fc)rotax+ have been investigated by time-resolved transient absorption and fluorescence measurements with changing solvent polarity. Nanosecond transient absorption measurements of the rotaxane demonstrated that the charge-separated state (C60-Fc +)rotax+ is formed mainly via the excited triplet state of C60 in polar solvents. The lifetime of (C60-;Fc+)rotax+ was evaluated to be 20 ns in dimethylformamide (DMF) at room temperature. With lowing temperature, the lifetime of (C60-;Fc+)rotax+ extends to 270 ns in DMF at - 65°C, due to the structural changes leaving C 60- and Fc+ at a relatively long distance in the low-temperature region. © 2006 American Chemical Society.
  • Photoinduced electron transfer processes in rotaxanes containing [60]fullerene and ferrocene: Effect of axle charge on light-induced molecular motion
    Atula S D Sandanayaka, Hisahiro Sasabe, Yasuyuki Araki, Nobuhiro Kihara, Yoshio Furusho, Toshikazu Takata, Osamu Ito
    Australian Journal of Chemistry 59 186-192 2006年03月
    Two rotaxanes containing [60]fullerene (C60) as pendants on a crown-ether necklace, to which ferrocene (Fc) as axle stoppers were added, have been synthesized. One rotaxane has an ammonium cation in the centre of the axle (C60;Fc)Rot+ and the other has a neutral axle (C 60;Fc)Rot. Optimized structures, calculated using a molecular orbital method, suggest that in the ground states (C 60;Fc)Rot+ has a shorter distance between C60 and Fc than that of (C60;Fc)Rot. In both rotaxanes, efficient intra-rotaxane photoinduced electron-transfer processes have been observed by the selective excitation of C60 which acts as a photosensitized electron acceptor. The rates and efficiencies of the charge-separation and charge-recombination processes were evaluated by time-resolved fluorescence and transient absorption measurements with changing solvent polarity. From the different kinetic parameters between (C 60;Fc)Rot+ and (C60;Fc)Rot, the light-induced molecular motions of these rotaxanes in the excited states and charge-separated states were separately revealed. © CSIRO 2006.
  • Synthesis and optical resolution of a double helicate consisting of ortho-linked hexaphenol strands bridged by spiroborates
    Hiroshi Katagiri, Toyoharu Miyagawa, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Angewandte Chemie - International Edition 45 1741-1744 2006年03月
    (Figure Presented) Double Twist: The first spiroborate-based helicate was synthesized and shown to be stable in the solid state as well as in solution. The double-stranded structure (see picture) was characterized by 1H NMR spectroscopy, ESI MS, and X-ray crystallographic studies. The racemic helicates were resolved by the formation of a diastereomeric, optically active ammonium salt. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.
  • Synthesis of [60]fullerene-functionalized rotaxanes
    Hisahiro Sasabe, Kei Ichiro Ikeshita, G. Abraham Rajkumar, Nobuhiro Watanabe, Nobuhiro Kihara, Yoshio Furusho, Kazuhiko Mizuno, Akiya Ogawa, Toshikazu Takata
    Tetrahedron 62 1988-1997 2006年02月
    Synthesis of [60]fullerene (C60)-functionalized rotaxanes via Diels-Alder reactions with C60 is described. Diels-Alder reaction of C60 and sulfolene moiety as masked diene attached on the wheels of rotaxanes results in high yields of C60 incorporation. Rotaxanes are prepared by tin-catalyzed urethane-forming end-capping reaction with isocyanate of pseudorotaxane having the wheel carrying C60 functionality as introduced by the Diels-Alder reaction. The Diels-Alder reaction was accomplished as end-capping reaction between C60 and pseudorotaxane bearing sultine moiety as masked diene on the axle terminal. A variety of C 60-containing [2]rotaxanes was prepared in moderate to good yields by these Diels-Alder protocols. © 2005 Elsevier Ltd. All rights reserved.
  • Temperature-driven switching of helical chirality of poly[(4-carboxyphenyl) acetylene] induced by a single amidine enantiomer and memory of the diastereomeric macromolecular helicity
    Takashi Hasegawa, Takashi Hasegawa, Kazuhide Morino, Yoshie Tanaka, Hiroshi Katagiri, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Macromolecules 39 482-488 2006年01月
    Two novel optically active amidines, (R,R)-N,N′-bis(1-phenylethyl)-2, 4,6-triphenylbenzamidine [(R,R)-2] and (R,R)-N,N′-bis(1-phenylethyl) benzamidine [(R,R)-3] were synthesized, and their helicity induction abilities for poly[(4-carboxyphenyl)acetylene] (poly-1) in dimethyl sulfoxide (DMSO) were investigated by UV-visible and circular dichroic spectroscopies. Poly-1 exhibited a split-type induced circular dichroism (ICD) in the polymer backbone region in the presence of the optically active amidines due to a predominantly one-handed helical conformation. The ICD pattern of poly-1 complexed with the bulky (R,R)-2 ([(R,R)-2]/[poly-1] = 1) dramatically changed in DMSO and the Cotton effect signs reversibly inverted by changing the temperature, whereas the complex of poly-1 with the less bulky (R,R)-3 complex did not show such a temperature-driven change in the ICD. These results indicate that the helix-sense of poly-1 induced by (R,R)-2 through noncovalent acid-base interactions undergoes a transition from one helix to another in response to temperature. Furthermore, the diastereomeric right- and left-handed helices of poly-1 induced by (R,R)-2 at different temperatures could be separately memorized by the replacement of (R,R)-2 with achiral amines, thus generating enantiomeric helices of the mirror images of each other. © 2006 American Chemical Society.
  • Photoinduced electron and energy transfer processes in rotaxanes containing zinc porphyrin as pendant and [60]fullerene and ferrocene as axle ends
    Mio Maes, Hisahiro Sasabe, Nobuhiro Kihara, Yasuyuki Araki, Yoshio Furusho, Kazuhiko Mizuno, Toshikazu Takata, Osamu Ito
    Journal of Porphyrins and Phthalocyanines 9 724-734 2005年12月
    Photoinduced electron-transfer processes of a newly synthesized rotaxane containing porphyrinatozinc (ZnP), [60]fullerene (C60), and ferrocene (Fc) have been studied in terms of the time-resolved fluorescence and transient absorption measurements in polar and nonpolar solvents. In this rotaxane, (ZnP;C60-Fc)rotax, ZnP was chosen as a pendant of a crown-ether necklace, through which an axle with C60 and Fc at both termini was penetrated. By the selective excitation of the ZnP moiety in a nonpolar solvent, energy transfer predominantly takes place to the C 60 moiety of (ZnP;C60-Fc)rotax. In polar solvents, charge-separation process takes place via the excited singlet state of the ZnP moiety in addition to the energy-transfer process. From the nanosecond transient absorption spectra, a clear absorption band of the C60•- moiety was observed at 1000 nm as well as a broad absorption in the 600-800 nm region due to ZnP•+, suggesting the generation of (ZnP•+;C60•--Fc)rotax in the first step. Afterward, the hole-transferring process from ZnP •+ to Fc is thermodynamically possible, although this process is not fast because of its through-space process character. The final lifetimes of the C60•- moiety were evaluated to be 290 and 370 ns in benzonitrile and DMF, respectively. The ratios of the charge-separation rates to charge-recombination rates were ca. 1000, indicating that (ZnP;C 60-Fc)rotax affords an efficient photosynthetic model. Copyright © 2005 Society of Porphyrins & Phthalocyanines.
  • Photoinduced intramolecular electron-transfer processes in [60]fullerene and N,N-bis(biphenyl)aniline molecular systems in solutions
    Atula S D Sandanayaka, Kei Ichiro Ikeshita, G. Abraham Rajkumar, Yoshio Furusho, Yasuyuki Araki, Toshikazu Takata, Osamu Ito
    Journal of Physical Chemistry A 109 8088-8095 2005年09月
    Photoinduced intramolecular charge-separation and charge-recombination processes in covalently connected C60-(spacer)-bis(biphenyl)aniline (C60-sp-BBA) and C60-((spacer)-bis(biphenyl)aniline) 2 (C60-(sp-BBA)2) have been studied by time-resolved fluorescence and transient absorption methods. Since a flexible alkylthioacetoamide chain was employed as the spacer, the folded structures in which the BBA moiety approaches the G60 moiety were obtained as optimized structures by molecular orbital calculations. The observed low fluorescence intensity and the short fluorescence lifetime of the C60 moiety of these molecular systems indicated that charge separation takes place via the excited singlet state of the G60 moiety in a quite fast rate and high efficiency even in the nonpolar solvent toluene, which was a quite new observation compared with reported dyads with different spacers. From the absorption bands at 880 and 1000 nm in the nanosecond transient absorption spectra, generations of C60•--sp-BBA •+ and C60•--(sp-BBA •+)(sp-BBA) were confirmed. The rates of charge separation and charge recombination for C60-(sp-BBA)2 are faster than those for C60-sp-BBA, suggesting that one of the BBA moieties approaches the C60 moiety by pushing another BBA moiety because of the flexible spacers. © 2005 American Chemical Society.
  • Photoinduced electron- And energy-transfer processes of [60]fullerene covalently bonded with one and two zinc porphyrin(s): Effects of coordination of pyridine and diazabicyclooctane to Zn atom
    Atula S D Sandanayaka, Kei Ichiro Ikeshita, Yasuyuki Araki, Nobuhiro Kihara, Yoshio Furusho, Toshikazu Takata, Osamu Ito
    Journal of Materials Chemistry 15 2276-2287 2005年06月
    C60-zinc porphyrin (ZnP) dyad (ZnP-C60) and triad (ZnP-C60-ZnP) were synthesized to probe energy-transfer and electron-transfer processes in the absence and presence of pyridine and diazabicyclooctane (DABCO). The syntheses of C60-ZnP and ZnP-C 60-ZnP were carried out by Diels-Alder cycloaddition between sulfolene moiety-containing porphyrin and C60. The photoinduced electron-transfer processes between the spatially positioned C60 and ZnP in the dyad and triad systems were investigated by time-resolved transient absorption and fluorescence measurements with changing solvent polarity. Upon excitation of the ZnP moiety, charge separation via an excited singlet state of ZnP takes place competitively with energy transfer to C60 generating the excited singlet state of C60, from which charge-separated states (ZnṖ+-C60̇- and ZnP ̇+-C60̇--ZnP) are also generated in polar solvents. Rates and efficiencies of energy transfer and charge separation for the triad are higher than those of the dyad. The generated chargeseparated species recombine with lifetimes in the rage of 240-330 ns in polar solvents such as DMF, PhCN, and THF for both dyad and triad. In o-dichlorobenzene, although the lifetimes of charge-separated states are very short (<20 ns), coordination of DABCO and pyridine to ZnP in the dyad and triad producing relatively stable coordinated complexes gives rise to prolongation of the charge-separated states up to 460 ns. © The Royal Society of Chemistry 2005.
  • A modular strategy to artificial double helices
    Yoshie Tanaka, Hiroshi Katagiri, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Angewandte Chemie - International Edition 44 3867-3870 2005年06月
    (Figure Presented) No metal required: Double-helical assemblies can be constructed through hydrogen bonds upon formation of amidinium-carboxylate salt bridges (see schematic representation). The double-helical structures formed including the helix sense are predictable by this approach. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA.
  • Syntheses of [60]fullerene and N,N-bis(4-biphenyl)aniline-tethered rotaxane: Photoinduced electron-transfer processes via singlet and triplet states of [60]fullerene
    Atula S D Sandanayaka, Kei Ichiro Ikeshita, Nobuhiro Watanabe, Yasuyuki Araki, Yoshio Furusho, Yoshio Furusho, Nobuhiro Kihara, Toshikazu Takata, Toshikazu Takata, Osamu Ito
    Bulletin of the Chemical Society of Japan 78 1008-1017 2005年06月
    A rotaxane containing [60]fullerene (C60) and N,N-bis(4-biphenyl)aniline (BBA) moieties was synthesized. In this structure, C60 acting as an electron acceptor, is attached to the crown-ether ring through which the axle with terminal BBA moieties acting as electron donors on both ends is penetrating. This rotaxane had a neutral amide moiety in the center of the axle in which two BBA moieties act as stoppers. The intra-rotaxane photoinduced electron-transfer processes of the C60 and BBA moieties were investigated by time-resolved transient absorption and fluorescence measurements while changing solvent polarity and temperature. Time-resolved transient absorption measurements of the rotaxanes confirmed that the long-lived charge-separated state (C60.-; BBA.+)rotaxane was formed via both the excited singlet and triplet states of Q60 (1Q60* and 3C60*, respectively) in polar solvents. The rate constants for charge-separation process were evaluated to be in the range of (3.6-3.7) × 108 s-1 via 1Q60* and (5.1-5.6) × 107 s -1 via 3C60* in the ratio of (0.36-0.38):(0.43-0.51). The rate constants of charge recombination were 2.5 × 106 s-1 and 4.4 × 106 s -1, corresponding to the lifetimes of the charge-separated states of 400 ns and 230 ns in THF and benzonitrile, respectively. By the temperature dependences, the activation free-energy changes of charge-separation process via 3Q60* were evaluated to be 0.10 eV, while those of the charge-recombination process were estimated to be 0.03 eV in THF and benzonitrile. These low activation energies are one of the characteristics of through-space electron transfer in the rotaxanes. © 2005 The Chemical Society of Japan.
  • Dual memory of enantiomeric helices in a polyacetylene induced by a single enantiomer
    Toyoharu Miyagawa, Akira Furuko, Katsuhiro Maeda, Hiroshi Katagiri, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Journal of the American Chemical Society 127 5018-5019 2005年04月
    We report the dual memory of both the enantiomeric right- and left-handed helical conformations induced in a polyacetylene based on the temperature-stimulated helicity inversion of the polymer. The polyacetylene folds into a one-handed helix induced by noncovalent bonding interactions with a single enantiomeric amine. The induced helix underwent a reversible inversion of the helicity by temperature. The diastereomeric right- and left-handed helices obtained at different temperatures could be further memorized when the optically active amine was replaced by an achiral diamine, generating right- and left-handed helices of the mirror images of each other. Consequently, both enantiomeric helices can be produced with a high efficiency from dynamically diastereomeric helical polyacetylenes induced by a single enantiomer. Copyright © 2005 American Chemical Society.
  • Photoinduced intramolecular electron-transfer processes in [60]fullerene-(spacer)-N,N-bis(biphenylyl)aniline dyad in solutions
    G. Abraham Rajkumar, G. Abraham Rajkumar, Atula S D Sandanayaka, Kei Ichiro Ikeshita, Mitsunari Itou, Yasuyuki Araki, Yoshio Furusho, Yoshio Furusho, Nobuhiro Kihara, Osamu Ito, Toshikazu Takata, Toshikazu Takata
    Journal of Physical Chemistry A 109 2428-2435 2005年03月
    Intramolecular photoinduced charge-separation and charge-recombination processes in a covalently connected C60-(spacer)-N,N-bis(biphenylyl) aniline (C60-spacer-BBA) dyad, in which the center-to-center distance of the electron acceptor and electron donor is 15 Å, have been studied by time-resolved fluorescence and transient absorption methods. The observed low fluorescence intensity and the short fluorescence lifetime of the C60 moiety of the dyad in PhCN and THF indicate that charge separation takes place via the excited singlet state of the C60 moiety at a quite fast rate and a high efficiency. The nanosecond transient absorption spectra in PhCN and THF showed the broad absorption bands at 880 and 1100 nm, which were attributed to C60-spacer-BBA•+. The charge-separated state decays with a lifetime of 330-360 ns in PhCN and THF at room temperature. From temperature dependence of the charge-recombination rate constants, the reorganization energy was evaluated to be 0.77-0.87 eV, which indicates that the charge-recombination process is in the inverted region of the Marcus parabola. With lowering temperature, the contribution of charge separation via the excited triplet state of the C60 moiety increases due to an increase in solvation of C60•--spacer-BBA•+. © 2005 American Chemical Society.
  • Synthesis and photoinduced electron transfer processes of rotaxanes bearing [60]fullerene and zinc porphyrin: Effects of interlocked structure and length of axle with porphyrins
    Atula S D Sandanayaka, Nobuhiro Watanabe, Kei Ichiro Ikeshita, Yasuyuki Araki, Nobuhiro Kihara, Yoshio Furusho, Yoshio Furusho, Osamu Ito, Toshikazu Takata
    Journal of Physical Chemistry B 109 2516-2525 2005年02月
    Three rotaxanes, with axles with two zinc porphyrins (ZnPs) at both ends penetrating into a necklace pending a C60 moiety, were synthesized with varying interlocked structures and axle lengths. The intra-rotaxane photoinduced electron transfer processes between the spatially positioned C 60 and ZnP in rotaxanes were investigated. Charge-separated (CS) states (ZnṖ+, C60̇-) rotaxane are formed via the excited singlet state of ZnP ( 1ZnP*) to the C60 moiety in solvents such as benzonitrile, THF, and toluene. The rate constants and quantum yields of charge separation via 1ZnP* decrease with axle length, but they are insensitive to solvent polarity. When the axle becomes long, charge separation takes place via the excited triplet state of ZnP (3ZnP*). The lifetime of the CS state increases with axle length from 180 to 650 ns at room temperature. The small activation energies of charge recombination were evaluated by temperature dependence of electron-transfer rate constants, probably reflecting through-space electron transfer in the rotaxane structures. © 2005 American Chemical Society.
  • Synthesis of novel interlocked systems utilizing a palladium complex with 2,6-pyridinedicarboxamide-based tridentate macrocyclic ligand
    Yoshio Furusho, Takanori Matsuyama, Toshikazu Takata, Toshiyuki Moriuchi, Toshikazu Hirao
    Tetrahedron Letters 45 9593-9597 2004年12月
    A new rotaxane synthesis utilizing square-planar palladium complex is described. A new protocol for the high yield synthesis of interlocked molecules is described. Palladium(II) complex including a 2,6-pyridinedicarboxamide-based tridentate macrocycle 2 was allowed to react with a 2,6-disubstituted pyridine derivative bearing two hydroxyl groups at both termini 3b to yield the corresponding Pd(II) complex 4b quantitatively. An acid catalyzed end-capping of 4b with a bulky isocyanate gave Pd(II) complex 5b in 96% yield, which was treated with carbon monoxide to afford [2]rotaxane 6b quantitatively. © 2004 Elsevier Ltd. All rights reserved.
  • Polyrotaxanes and polycatenanes: Recent advances in syntheses and applications of polymers comprising of interlocked structures
    Toshikazu Takata, Nobuhiro Kihara, Yoshio Furusho
    Advances in Polymer Science 171 1-75 2004年12月
    Syntheses and applications of interlocked polymers, polyrotaxanes, and polycatenanes, including corresponding oligomers are reviewed with emphasis on (i) synthesis of interlocked polymers consisting of interlocked structures as the monomer-linking units (genuine "topological" polymers), and (ii) application of the interlocked polymers in both bulk and molecular levels. Further, the review also refers to a few important polyrotaxanes and polycatenane which are still unknown despite many synthetic challenges attempted so far. The review mainly summarizes the recent progress in the chemistry of polyrotaxanes and polycatenanes during this decade, in terms of kind of ring systems.
  • Synthesis of side-chain polyrotaxane via radical polymerizations of vinylic pseudorotaxane monomers having paraquat-type macrocycle as a wheel component
    Toshikazu Takata, Toshihide Hasegawa, Nobuhiro Kihara, Yoshio Furusho
    Polymer Journal 36 927-932 2004年12月
    The side-chain polyrotaxane was synthesis by radical polymerizations of vinylic pseudorotaxane monomers having paraquat-type macrocycle as a wheel component. The synthesis of 3,5-di-t-butylnbenzoic acid ester and acrylic acid ester was also presented. It was demonstrated that the pseudorotaxane monomer strategy in side-chain type polyrotaxane synthesis have some advantageous characteristics including facile and certain introduction of rotaxane units into polymer, easy synthesis of various polyrotaxanes. The procedure for polymerization of pseudorotaxane monomer was also presented.
  • Is the tert-butyl group bulky enough to end-cap a pseudorotaxane with a 24-crown-8-ether wheel?
    Yuya Tachibana, Yuya Tachibana, Nobuhiro Kihara, Yoshio Furusho, Yoshio Furusho, Toshikazu Takata
    Organic Letters 6 4507-4509 2004年11月
    (Chemical equation presented) Although rotaxane chemists have long believed that the tert-butyl group is bulkier than the cavity of dibenzo-24-crown-8- ether (DB24C8), it is essentially smaller than the cavity of DB24C8. The tert-butyl (or 4-tert-butylphenyl) group can actually function as an end-cap of DB24C8-based rotaxanes when the intercomponent interaction is effectively operative. When such attractive interaction is removed, deslippage occurs.
  • Synthesis and shuttling behavior of rotaxanes consisting of crown ether wheel and disulfide dumbbell with two ammonium centers
    Yoshio Furusho, Ryoko Sanno, Tomoya Oku, Toshikazu Takata
    Bulletin of the Korean Chemical Society 25 1641-1644 2004年11月
    Several [2]- and [3]rotaxanes bearing some functional groups on their wheel components and spacers with different lengths between two ammonium centers on their dumbbell components were prepared in good yields from dibenzo-24-crown-8- ether derivatives and dumbbell-shaped bis(sec-ammonium salt)s having a centrally located disulfide linkage, by utilizing the reversible thiol-disulfide interchange reaction. The shuttling behaviors of the [2]rotaxanes were investigated by 1H NMR by use of the spin polarization transfer-selective inversion recovery technique. It was found that the change in spacer length in the axle resulted in a drastic change in shuttling rate of the [2]rotaxanes, although the introduction of the functional groups to the wheels did not affect the shuttling behavior at all.
  • End-capping of a pseudorotaxane via diels-alder reaction for the construction of C60-terminated [2]rotaxanes
    Hisahiro Sasabe, Nobuhiro Kihara, Yoshio Furusho, Kazuhiko Mizuno, Akiya Ogawa, Toshikazu Takata
    Organic Letters 6 3957-3960 2004年10月
    (Chemical Equation Presented) The Diels-Alder reaction of various dienophiles such as C60 with a pseudorotaxane having a sultine moiety afforded corresponding [2]-rotaxanes in moderate yields. The introduction of a porphyrin moiety on the wheel component considerably enhanced the efficiency of the end-capping reaction with C60.
  • Design and synthesis of chiral poly(binaphthyl salen zinc complex) and application of the asymmetric field based on its helical conformation to a catalytic asymmetric reaction
    Takeshi Maeda, Takeshi Takeuchi, Yoshio Furusho, Toshlkazu Takata
    Journal of Polymer Science, Part A: Polymer Chemistry 42 4693-4703 2004年09月
    According to a rational design of helices (i.e., fusing C2 chiral binaphthyl units and metallosalen complexes inevitably results in the formation of helical polymers), chiral poly(binaphthyl salen zinc complexes (3-Zn) were synthesized from an (R)-3,3′-diformylbinaphthol derivative, α,ω-diamines, and zinc acetate or diethylzinc. Their helical structures were well supported by their infrared, ultraviolet, and circular dichroism spectra, in addition to MM calculations and a CPK model study. The catalysis of 3-Zn during the asymmetric addition of diethylzinc to aldehydes was investigated. In the presence of 5 unit mol % 3-Zn, diethylzinc reacted with benzaldehyde to yield 1-phenyl-1-propanol in high yields (∼100%) and with high enantioselectivity (∼95%). The asymmetric yield of 1-phenyl-1-propanol increased significantly as the temperature was lowered, whereas both the asymmetric yield and the absolute configuration were drastically changed as the structure of the diamine unit of 3-Zn was varied. Several aromatic aldehydes were converted into their corresponding alcohols with high enantioselectivity. © 2004 Wiley Periodicals, Inc.
  • Photoinduced electron-transfer processes between [C60]fulIerene and triphenylamine moieties tethered by rotaxane structures. Through-space electron transfer via excited triplet states of [60]fullerene
    Atula S D Sandanayaka, Hisahiro Sasabe, Yasuyuki Araki, Yoshio Furusho, Yoshio Furusho, Osamu Ito, Toshikazu Takata, Toshikazu Takata
    Journal of Physical Chemistry A 108 5145-5155 2004年06月
    Two rotaxanes tethering [60]fullerene (C 60) and triphenylamine (TPA) moieties were synthesized in good yields by the urethane end-capping method using a crown ether-secondary amine motif. In these rotaxanes, the C 60 group serving as electron acceptor is attached to the crown ether wheel through which the axle with a TPA group acting as electron donor on its terminal penetrates. One rotaxane has an ammonium moiety, whereas the other has a neutral amide moiety in the center of the axle. The corresponding reference compounds without rotaxane structures were also prepared. The intra-rotaxane photoinduced electron-transfer processes of C 60 and TPA have been investigated by time-resolved transient absorption and fluorescence measurements with changing solvent polarity and temperature. Nanosecond transient absorption measurements of these rotaxanes demonstrated that the long-lived charge-separated state (C 60.-,TPA .+) rotaxane is formed via the excited triplet state of C 60 ( 3C 60*) in polar solvents. The rate constants for the charge separation process were in the range of (5-8) × 10 7 s -1, while the rate constants of charge recombination were in the range of (3-6) × 10 6 s -1, corresponding to the lifetimes of the charge-separated states of 170-300 ns. Both rate constants depended on rotaxane structure, solvent polarity, and temperature. The activation free energy changes of charge separation and recombination processes were evaluated to be 0.01-0.03 and 0.03-0.06 eV by temperature dependences, respectively. Such low activation energies may be related to through-space electron transfer in these rotaxanes. On the other hand, in a covalently connected TPA-C 60 dyad, fast charge separation from the excited singlet state and fast charge recombination were observed through bonds in polar solvents.
  • A concept for recyclable cross-linked polymers: Topologically networked polyrotaxane capable of undergoing reversible assembly and disassembly
    Tomoya Oku, Yoshio Furusho, Toshikazu Takata
    Angewandte Chemie - International Edition 43 966-969 2004年02月
    It's physical: A novel concept for recyclable cross-linked polymers is presented by utilizing mechanical linkages in a polyrotaxane network capable of undergoing reversible assembly and disassembly (see schematic representation).
  • Dynamic covalent chemistry in rotaxane synthesis. Slipping approach to [2]rotaxane utilizing reversible cleavage-rebondage of trityl thioether linkage
    Yoshio Furusho, Tomoya Oku, G. Abraham Rajkumar, Toshikazu Takata
    Chemistry Letters 33 52-53 2004年01月
    A [2]rotaxane was synthesized in a high yield from a dumbbell-shaped sec-ammonium salt having trityl thioether and 3,5-di-t-butylphenyl groups at the both ends and dibenzo-24-crown-8-ether, through the slipping, utilizing the reversible cleavage-rebondage of the trityl thioether linkage.
  • Synthesis of [2]- and [3]Rotaxanes by an End-Capping Approach Utilizing Urethane Formation
    Yoshio Furusho, Hisahiro Sasabe, Daisuke Natsui, Ken Ichi Murakawa, Toshikazu Takata, Toshikazu Takata, Toshiro Harada
    Bulletin of the Chemical Society of Japan 77 179-185 2004年01月
    Several axle-shaped sec-ammonium salts having hydroxy groups at the terminal ends were allowed to react with 3,5-dimethylphenyl isocyanate in the presence of dibenzo-24-crown-8 ether (DB24C8) in CHCl3 by the catalysis of dibutyltin dilaurate to afford the corresponding [2]rotaxanes in good yields. Several Lewis acids other than dibutyltin dilaurate were effective for the end-capping. Although N,N-dimethylacetamide was not a suitable solvent, the use of chlorobenzene and nitromethane as solvents gave the [2]rotaxane in high yields. When a C2-chiral 26-membered crown ether, prepared from biphenyl-2,2′,6,6′-tetrol and L-tartaric acid, was employed instead of DB24C8, the corresponding optically active [2]rotaxane was isolated in 47% yield. The present method was successfully applied to the synthesis of [3]rotaxane by employing hexamethylene diisocyanate. Thus, end-capping by acid-catalyzed urethane formation from alcohol and isocyanate was demonstrated to be an effective protocol for the synthesis a variety of rotaxanes, based on the sec-ammonium salt/crown ether recognition motif.
  • Rotaxane-Stabilized Thiophosphonium Salt from Disulfide and Phosphine
    Tomoya Oku, Tomoya Oku, Tomoya Oku, Tomoya Oku, Yoshio Furusho, Yoshio Furusho, Yoshio Furusho, Toshikazu Takata, Toshikazu Takata, Toshikazu Takata, Toshikazu Takata
    Organic Letters 5 4923-4925 2003年12月
    (Equation Presented) The reaction of a rotaxanated disulfide with hexamethylphosphorustriamide afforded a stable thiophosphonium salt in rotaxanated form. The structure of the thioposphonium salt was confirmed by spectroscopic and X-ray crystal structure analyses. The successful isolation of this salt was attributed to the special stabilization capability of the rotaxane structure.
  • Dynamic covalent approach to [2]- and [3]rotaxanes by utilizing a reversible thiol-disulfide interchange reaction
    Yoshio Furusho, Tomoya Oku, Toshihide Hasegawa, Akiyoshi Tsuboi, Nobuhiro Kihara, Toshikazu Takata
    Chemistry - A European Journal 9 2895-2903 2003年06月
    A dynamic covalent approach to disulfide-containing [2]- and [3]rotaxanes is described. Symmetrical dumbbell-shaped compounds with two secondary ammonium centers and a central located disulfide bond were synthesized as components of rotaxanes. The rotaxanes were synthesized from the dumbbell-shaped compounds and dibenzo-[24]crown-8 (DB24C8) with catalysis by benzenethiol. The yields of isolated rotaxanes reached about 90% under optimized conditions. A kinetic study on the reaction forming [2]rotaxane 2a and [3]rotaxane 3a suggested a plausible reaction mechanism comprising several steps, including 1) initiation, 2) [2]rotaxane formation, and 3) [3]rotaxane formation. The whole reaction was found to be reversible in the presence of thiols, and thermodynamic control over product distribution was thus possible by varying the temperature, solvent, initial ratio of substrates, and concentration. The steric bulk of the end-capping groups had almost no influence on rotaxane yields, but the structure of the thiol was crucial for reaction rates. Amines and phosphines were also effective as catalysts. The structural characterization of the rotaxanes included an X-ray crystallographic study on [3]rotaxane 3a.
  • Photoinduced intrarotaxane electron transfer between zinc porphyrin and [60]fullerene in benzonitrile
    Nobuhiro Watanabe, Nobuhiro Kihara, Yoshio Furusho, Toshikazu Takata, Yasuyuki Araki, Osamu Ito
    Angewandte Chemie - International Edition 42 681-683 2003年02月
    A through-space superexchange mechanism appears to be responsible for charge recombination (CR) following photoexcitation and charge separation (CS) in rotaxanes containing zinc porphyrin and C60 moieties (see picture), as suggested by the low activation energy of this process. Furthermore, the charge-separated state is relatively long-lived.
  • Synthesis and properties of optically active polycarbonates having long Alkyl chains on the main chain consisting of C2-chiral binaphthyl units
    Toshikazu Takata, Masanori Goto, Yoshio Furusho, Takashi Kato
    Kobunshi Ronbunshu 59 778-786 2002年12月
    Binaphthol derivatives having long alkyl chains on 6- and 6' -positions (1) were synthesized from (R)-binaphthol. Polycondensation of 1 with bis(4-nitrophenyl) carbonate yielded the corresponding polycarbonate (2, Mn ca. 5000). 2 was also synthesized via a cyclic carbonate (8) derived from 1. The structure simulation of 2 using MM 2 parameters suggested that it adopts a columnar shape of nanometer size. In the CD spectra, 2 showed the opposite Cotton effects to those of the unit model (9), indicating that 2 adopts a stable helical conformation in solution. The intensity of the Cotton effects of 2 decreased with an increase in temperature, suggesting that the helical structure is disordered at high temperatures. Thermal analysis of 2 was also examined by DSC.
  • Photoreaction of cinnamate with nitrogen monoxide catalyzed by metallosalen complexes
    Yoshio Furusho, Yow hei Sohgawa, Nobuhiro Kihara, Toshikazu Takata
    Bulletin of the Chemical Society of Japan 75 2025-2029 2002年09月
    Ethyl cinnamate was allowed to react with nitrogen monoxide (NO) by photoirradiation in the presence of metallosalen complexes (4), oxygen, and axial ligands for 4 to yield furoxan derivatives (6). Oxygen and axial ligands are indispensable for this reaction. Photoirradiation enhanced the yield of 6. Lowering the reaction temperature increased the yield of 6 up to 55% (at -5°C).
  • Synthesis of [2]rotaxanes by tritylative endcapping of in situ formed pseudorotaxanes having thiol or hydroxyl functionality on the axle termini
    Yoshio Furusho, G. Abraham Rajkumar, Tomoya Oku, Toshikazu Takata
    Tetrahedron 58 6609-6613 2002年08月
    Tritylative endcapping of an in situ formed pseudorotaxane consisting of dibenzo-24-crown-8 and an axle having a thiol group at the end by treatment with trityl hexafluorophosphate at room temperature gave the corresponding sulfide-type [2]rotaxane in high yields. Treatment of the pseudorotaxane having a hydroxyl group at the axle terminal with trityl hexafluorophophate followed by addition of a base such as triethylamine afforded the corresponding ether-type [2]rotaxane in good yields. © 2002 Elsevier Science Ltd. All rights reserved.
  • Synthesis and structure of poly(binaphthyl salen manganese complex) and its application to asymmetric epoxidation
    Takeshi Maeda, Yoshio Furusho, Toshikazu Takata, Toshikazu Takata
    Chirality 14 587-590 2002年07月
    Poly(binaphthyl salen manganese complex)es 3-Mn were synthesized from a 3,3′-diformylbinaphthol derivative, α,ω-diamines, and Mn(OAc)2. Their helical structures were well-supported by their IR, UV, and CD spectra. The catalysis of 3-Mn in an asymmetric epoxidation was investigated. © 2002 Wiley-Liss, Inc.
  • Photochemical or thermal chelate exchange in the ruthenium coordination sphere of complexes of the Ru(phen)2L family (L = diimine or dinitrile ligands)
    Etienne Baranoff, Jean Paul Collin, Junko Furusho, Yoshio Furusho, Anne Chantal Laemmel, Jean Pierre Sauvage
    Inorganic Chemistry 41 1215-1222 2002年03月
    Complexes of the type Ru(phen)2L2+, where L is a substituted bipyridine family member, have been prepared, and their photochemical substitution reactions have been investigated. In the presence of a bis-benzonitrile derivative, acting as a bidentate chelate, photoexpulsion of L is performed under the action of visible light, with quantitative formation of new complexes of the type Ru(phen)2L′2+ (L′ = bis-nitrile ligand). Several complexes have been characterized by X-ray crystallography. In particular, the bis-benzonitrile complexes could be crystallized, and the structure of these compounds, containing a 13-, 14-, or 15-membered metal incorporating ring, was obtained. By heating Ru(phen)2L′2+ with a bipy derivative in refluxing ethylene glycol, quantitative formation of the starting complex [Ru(phen)2L2+] was carried out. The present series of compounds presents properties that could be profitably used in the design and construction of multicomponent systems acting as photochemically driven molecular machines.
  • Synthesis of calix[4]arene and porphyrin tethering four chiral five-membered cyclic carbonates
    Toshikazu Takata, Hideyuki Takagi, Yoshio Furusho
    Enantiomer 7 129-132 2002年03月
    Calix[4]arene tethering four chiral five-membered cyclic carbonates 1c was synthesized by O-glycidylation of p-tert-butylcalix[4]-arene 1a with (R)-glycidyl tosylate, followed by carbonation with carbon dioxide catalyzed by lithium bromide. Porphyrin tethering chiral five-membered cyclic carbonates 2c was similarly synthesized.
  • First poly[3]rotaxane synthesized through the noncovalent step-growth polymerization of a homoditopic dumbbell compound and a macrocycle with a reversible thiol-disulfide interchange reaction
    Tomoya Oku, Yoshio Furusho, Toshikazu Takata
    Journal of Polymer Science, Part A: Polymer Chemistry 41 119-123 2002年01月
    A previous study introduced a new synthetic method for [2]rotaxane and [3]rotaxane under thermodynamic control, which uses the reversible cleavage-recombination process of the disulfide bond in the presence of a catalytic amount of thiol. This paper discusses the first synthesis of poly[3]rotaxane by the application of this method to homoditopic molecules.
  • Polyslipping: A new approach to polyrotaxane-like assemblies
    Yow Hei Sohgawa, Hiroki Fujimori, Junko Shoji, Yoshio Furusho, Nobuhiro Kihara, Toshikazu Takata
    Chemistry Letters 774-775 2001年12月
    "Polyslipping", that is, multiple slipping of dumbbell components into macrocyclic ones having the appropriate size complementarity, of bis-ammonium salt 1 and bis-crown ether 5 in acetone or acetonitrile afforded polyrotaxane-like assembly 6, which quantitatively reverted to the monomers 1 and 5 by dissolving in DMSO.
  • A rational design of helix: Absolute helix synthesis by binaphthyl-salen fusion
    Yoshio Furusho, Takeshi Maeda, Takeshi Takeuchi, Nobuaki Makino, Toshikazu Takata
    Chemistry Letters 1020-1021 2001年12月
    A rational design of helical molecules is presented. Fusing chiral binaphthyl units and metallosalen complexes resulted in formation of molecules which inevitably adopt certain helical conformations.
  • Synthesis of side-chain polyrotaxane by radical polymerizations of pseudorotaxane monomers consisting of crown ether wheel and acrylate axle bearing bulky end-cap and ammonium group
    Toshikazu Takata, Hiroaki Kawasaki, Nobuhiro Kihara, Yoshio Furusho
    Macromolecules 34 5449-5456 2001年07月
    The mixing of an acrylate la bearing secondary ammonium salt moiety and terminal di-tert-butylphenyl group with dibenzo-24-crown-8 (DB24C8) afforded the pseudorotaxane monomer 2a. The association constant Ka was 18 L mol-1 in CDCl3 at 25 °C. An equimolar mixture of la and DB24C8 was heated at 60 °C for 20 h in benzene (0.5 M) in the presence of AIBN to give side-chain-type polyrotaxane in 66% yield. The incorporation ratio of the rotaxane unit, which is denoted by R, in the polyrotaxane was 0.42. The R value increased as the polymerization temperature decreased or the dielectric constant of the solvent decreased. The effect of the molar ratio [DB24C8]/[1a] on the R value was complicated since DB24C8 itself enhanced the polarity of the system. The R value increased until [DB24C8]/[1a] reached 1.0 in benzene, chlorobenzene, and 1,2-dichloroethane. When [DB24C8]/[1a] > 1, however, the R value increased gradually as [DB24C8]/[1a] increased in polar solvent such as 1,2-dichloroethane, while the R value rather decreased in less polar solvent such as benzene. The copolymerization of 2a and styrene afforded the corresponding copolymer. The composition of the rotaxane unit could be controlled by the feed ratio of styrene, while the ratio of complexation of the ammonium group, i.e., rotaxane content to total acrylate, remained almost constant. The acylative neutralization of the resulting polyrotaxane afforded a nonionic polyrotaxane.
  • Chemical modification of amide-based catenanes and rotaxanes II. Synthesis of tertiary amine [2]catenanes and [2]rotaxanes via N-methylation followed by borane reduction of secondary amide [2]catenanes and [2]rotaxanes and mobility of their components
    Nobuhiro Watanabe, Yoshio Furusho, Nobuhiro Kihara, Toshikazu Takata, Kazushi Kinbara, Kazuhiko Saigo
    Bulletin of the Chemical Society of Japan 74 149-155 2001年01月
    Secondary amide [2]catenane 1a was converted to the corresponding tertiary amide [2]catenane 1b by repetitive treatment with a methylating system of CH 3I and KOH in DMSO. The amide functions of 1b were reduced with borane in refluxing THF to give the corresponding tertiary amine [2]catenane 1c. Their structures were characterized by NMR, IR, and FAB-MS spectroscopies. An X-ray crystallographic analysis of 1c showed that its solid-state structure was stabilized by a CH-π interaction between the p-xylylene and m-xylylene units, together with a π-π stacking interaction between the two m-xylylene units. A variable temperature 1H NMR study suggested that 1c had components of highly enhanced mobility in CDCl 3, even at lower temperature, although a much weaker interaction, such as the CH-π interaction, existed between their components in solution. Tertiary amine [2]rotaxane 3c was obtained from the corresponding secondary amide [2]rotaxane 3a by a procedure similar to that used for 1a. The 1H NMR spectra indicated that the mobility of the components of 3c is sufficiently high even at lower temperature.
  • On the stereoselectivity in bisdihydroxylation of 1,5-cyclooctadiene with osmium tetroxide
    K. Kawazoe, Y. Furusho, S. Nakanishi, T. Takata
    Synthetic Communications 31 2107-2112 2001年01月
    In the bisdihydroxylation of 1,5-cyclooctadiene with OsO4, use of a stoichiometric amount of OsO4 yielded a 1:1 mixture of syn- and anti-isomers, while use of a catalytic amount of OsO4 gave only syn-(1R*,2S*,5R*,6S*)-cyclooctane-1,2,5,6-tetrol. This syn-selectivity was attributed to the favorable formation of an intramolecular osmium(VI) bisglycolate ester in the catalytic reaction.
  • Chemical modification of amide-based catenanes and rotaxanes I. Synthesis of secondary amine [2]catenanes and [2]rotaxanes by the borane reduction of secondary amide [2]catenanes and [2]rotaxanes and mobility of their components
    Yoshio Furusho, Junko Shoji, Nobuhiro Watanabe, Nobuhiro Kihara, Tomohiro Adachi, Toshikazu Takata
    Bulletin of the Chemical Society of Japan 74 139-147 2001年01月
    Various secondary amine [2]catenanes and [2]rotaxane were prepared by borane reduction of the corresponding secondary amide [2]catenanes and [2]rotaxane. Their structures were characterized by NMR, IR, and FAB-MS spectroscopies. The mobility of the components in solution was examined by 1H NMR spectroscopy. The substituents on the isophthaloyl units of the catenanes prevented complete circumrotation of the macrocyclic components ("half rotation"). On the other hand, macrocyclic ring components bearing unsubstituted isophthaloyl units completely circumrotated through the other faster than on the 1H NMR time scale ("full rotation"). In the case of the secondary amine [2]catenanes, no hydrogen bonding interaction between the secondary amino groups was observed. A dynamic 1H NMR study showed a highly enhanced mobility of the components of the secondary amine [2]catenanes and [2]rotaxane compared with the corresponding amide compounds, even at lower temperature.
  • Synthesis of diarylsulfoximines by the Friedel-Crafts reaction of sulfonimidoyl chlorides
    Y. Furusho, Y. Okada, T. Takata
    Bulletin of the Chemical Society of Japan 73 2827-2828 2000年12月
    In the presence of an equimolar amount of FeCl 3, sulfonimidoyl chlorides were allowed to react with aromatic compounds to give the corresponding sulfoximines. Structure of the sulfonimidoyl chlorides and the aromatic compounds had considerable influence on the yield of the sulfoximines.
  • "Unlock-lock" approach to [2] and [3]rotaxanes: Entering of a ring through disulfide linkage that is unlocked by thiol "key"
    Yoshio Furusho, Toshihide Hasegawa, Akiyoshi Tsuboi, Nobuhiro Kihara, Toshikazu Takata
    Chemistry Letters 18-19 2000年12月
    Bifunctional secondary ammonium salt bearing disulfide linkage at the center and bulky group at the both termini was mixed with dibenzo-24-crown-8. During reversible cleavage of the disulfide linkage catalyzed by benzenethiol, crown ether entered the disulfide linkage to afford corresponding [2] and [3]rotaxanes.
  • A photochromic system based on photochemical or thermal chelate exchange on Ru(phen)2L2+ (L = diimine or dinitrile ligand)
    E. Baranoff, J. P. Collin, Y. Furusho, A. C. Laemmel, J. P. Sauvage
    Chemical Communications 1935-1936 2000年10月
    In the presence of a bidentate chelate containing two convergent nitrile groups, Ru(phen)2L2+ (L = sterically hindering aromatic diimine ligand; phen = 1,10-phenanthroline) undergoes a photochemical reaction leading to quantitative replacement of the diimine by the bis-nitrile ligand; the reverse reaction takes place upon heating, also quantitatively.
  • Optically active poly- and oligo(biphenyl carbonate)s as stable helical molecules
    Ken Ichi Murakawa, Yoshio Furusho, Toshikazu Takata
    Chemistry Letters 93-94 1999年12月
    Low molecular weight polycarbonate ((R)-2) derived from polycondensation of (R)-4,4′,6,6′-tetramethyl-2,2′-dihydroxybiphenyl ((R)-3) showed large Cotton effect at 210 nm compared with its unit model. CD spectra of model oligomers of (R)-2 (2-8mers) obtained by stepwise synthesis and their structure simulation suggested that (R)-2 and higher oligomers can hold a stable left-handed helix.
  • Synthesis and structure of [2]catenated tertiary octamide and octamine
    Nobuhiro Watanabe, Yoshio Furusho, Nobuhiro Kihara, Toshikazu Takata, Kazushi Kinbara, Kazuhiko Saigo
    Chemistry Letters 915-916 1999年12月
    Treatment of [2]catenated sec. octamide (1) with methyl iodide under an alkaline condition gave the corresponding N-methylated tert. octamide (2) which was reduced to [2]catenated tert. octamine (3). The structures of 2 and 3 were studied by Xray crystal structure and 1H NMR analyses.
  • Radically polymerizable pseudorotaxane monomers: Versatile building units for side chain polyrotaxane synthesis
    Toshikazu Takata, Hiroaki Kawasaki, Satoko Asai, Nobuhiro Kihara, Yoshio Furusho
    Chemistry Letters 111-112 1999年12月
    Side chain polyrotaxanes were synthesized from radically polymerizable pseudorotaxane monomers (DB24C8·1) which were composed of secondary ammonium salts having (meth)acryl group at one end and bulky stopper at the other end (1a and 1b) and dibenzo-24-crown-8 (DB24C8). Both radical polymerization of DB24C8·1 and copolymerization of DB24C8·1a with styrene afforded corresponding polymers having rotaxane moieties in the side chains (2a, 2b, and 3).
  • Synthesis and structure of optically active helical poly- and oligocarbonates consisting of C2-chiral biphenyl unit
    Toshikazu Takata, Ken Ichi Murakawa, Yoshio Furusho
    Polymer Journal 31 1051-1056 1999年12月
    Enantiomerically pure (R)-4,4′,6,6′-tetramethyl-2,2′-dihydroxybiphenyl ((R)-6) and the corresponding cyclic carbonate were prepared along with racemic ones ((±)-6 and (±)-7). The X-ray crystallographic analysis of (±)-7 supported the proposed cyclic carbonate structure. Anionic ring-opening polymerization of cyclic carbonate (R)-7 with t-BuOK in THF gave thoroughly insoluble materials. Alternatively, soluble polycarbonate ((R)-5) with low molecular weight was synthesized by polycondensation of (R)-6. The model oligomers of (R)-5 (2-8 mers) were synthesized. (R)-5 exhibited large negative Cotton effect around 210 nm compared with that of its unit model ((R)-9) in the CD spectra. CD spectral study and structure simulation of the model oligomers ((R)-11-13) suggested that (R)-5 and higher oligomers can hold a stable left-handed helix in solution.
  • Conjugate addition-approach to end-capping of pseudorotaxanes for rotaxane synthesis
    Toshikazu Takata, Hiroaki Kawasaki, Satoko Asai, Yoshio Furusho, Nobuhiro Kihara
    Chemistry Letters 223-224 1999年12月
    Conjugate addition of 4-tert-butylbenzenethiol to pseudorotaxane having terminal α,β-unsaturated ester group under radical condition afforded the corresponding aryl sulfide-capped rotaxane, while conjugate addition of sodium 4-tert-butylbenzenesulfinate under acidic condition also yielded aryl sulfone-capped rotaxane.
  • Design of multidentate pyrrolic ligands by N-modification: Synthesis of N-monomethyl, monoethyl, dimethyl, trimethyl, and tetramethylporphyrinogens
    Yoshio Furusho, Hiroaki Kawasaki, Saburo Nakanishi, Takuzo Aida, Toshikazu Takata
    Tetrahedron Letters 39 3537-3540 1998年05月
    Five possible N-methylated and N-monoethylated meso- octaethylporphyrinogens were prepared by N-alkylation of lithiated meso- octaethylporphyrinogens with alkyl iodides in the presence of crown ether. The crystal structure of 3b was established by X-ray crystal structure analysis.
  • Optically active poly(aryl carbonates) consisting of axially chiral units. Chiral binaphthyl group induced helical polymer
    Toshikazu Takata, Yoshio Furusho, Ken Ichi Murakawa, Takeshi Endo, Hideo Matsuoka, Takashi Hirasa, Jyuho Matsuo, Masahiko Sisido
    Journal of the American Chemical Society 120 4530-4531 1998年05月
  • A catenated cyclic octamine: A noncovalently bonded molecular system without attractive interaction between the two units
    Toshikazu Takata, Junko Shoji, Yoshio Furusho
    Chemistry Letters 881-882 1997年12月
    A novel [2]catenane consisted of two cyclic tetramine units (6) was prepared and characterized in terms of mobility of the units. The preparation of 6 was performed by reduction of the corresponding cyclic octamide-type [2]catenane (3) with borane. Varying temperature NMR study indicated that the units of 6 actually move or rotate quite freely unlike those of 3, evidently suggesting a noncovalently bonded molecule without attractive interaction 1 between the two units.
  • Synthesis and polymerization of cyclic carbonates containing a binaphthyl moiety
    Toshikazu Takata, Hideo Matsuoka, Takashi Hirasa, Jyuho Matsuo, Takeshi Endo, Yoshio Furusho
    Kobunshi Ronbunshu 54 974-981 1997年12月
    Synthesis and anionic ring-opening polymerization of aromatic cyclic carbonates were investigated. Detailed studies with 2,2′-biphenol and 1,1′-bi(2-naphthol) as diols showed that the synthesis with 2 mol of p-nitrophenyl chloroformate and 2 mol of a tertiary amine afforded the best results (yields of the corresponding cyclic carbonates 3 and 5 were ca. 80%). Preparation using phosgene dimer resulted in good yield of 3 but was not suitable for 5. Stability of 5 was low enough to react with methanol only by mixing to give an adduct readily. High ring-opening ability of 5 based on its strained ring was suggested from the structure simulation of 3 and 5. Anionic ring-opening polymerization of 5 initiated with t-BuOK and the related alkalis proceeded smoothly to give a polycarbonate quantitatively (M̄ n ca. 15000). This polymer could also be obtained by polycondensation using 1,1′-bi(2-naphthol) and bis(4-nitrophenyl)carbonate. Thermal analysis, powder X-ray analysis, and volume change on polymerization were studied.
  • Guest-responsive structural changes of porphyrinogen inclusion crystals: A long-range cooperative effect on guest inclusion
    Yoshio Furusho, Takuzo Aida
    Chemical Communications 2205-2206 1997年12月
    meso-Octaethylporphyrinogen inclusion crystals with lower alcohols undergo reversible guest-responsive structural changes, for which a long-range cooperative effect with a Hill coefficient of 40 is observed.
  • Synthesis and optical resolution of axially dissymmetric pyrroles and pyrocolls: New catalysts for the enantioselective addition of diethylzinc to aromatic aldehydes
    Yoshio Furusho, Akihiro Tsunoda, Takuzo Aida
    Journal of the Chemical Society - Perkin Transactions 1 183-190 1996年01月
    The novel axially dissymmetric pyrroles, 4-methyl-3-(2′-methoxy-1′-naphthyl)pyrrole-2-carboxylates 1 and 4-ethyl-3-(10′-methoxy-9′-phenanthryl)pyrrole-2-carboxylates 3 were synthesized from the corresponding nitroalkenes and ethyl isocyanoacetate. Optical resolution of compounds 1 was achieved via crystallization of a diastereoisomeric mixture of the (R)-1-phenylethyl esters 1d, while the antipodes of compound 3b spontaneously resolved upon crystallization of the racemate. The rotational barrier (ΔG‡) at 25°C about the pyrrole-phenanthrene bond in compound 3b (160 kJ mol-1) was 30 kJ mol-1 higher than that about the pyrrole-naphthalene bond in compound 1b. The carboxylate 1b or 3b lost optical activity upon lactonization, while the resulting lactone 2 opened diastereoselectively by reaction with lithium (S)-1-phenylethylamide. The antipodes of compounds 1a and 3a were converted respectively without racemization into axially dissymmetric pyrocolls, 1,6-bis(2′-hydroxy-1′-naphthyl)-2,7-dimethylpyrocoll 5a and 2,7-diethyl-1,6-bis(10′-hydroxy-9′-phenanthryl)pyrocoll 6a, both of which effectively catalysed enantioselective addition of Et2Zn to aromatic aldehydes.
  • The axially dissymmetric pyrrole as a novel chiral building block: Synthesis, characterization and application to the first 'predetermined' synthesis of a chiral atropisomeric porphyrin with molecular asymmetry
    Yoshio Furusho, Takuzo Aida, Shohei Inoue
    Journal of the Chemical Society, Chemical Communications 653-655 1994年12月
    The first axially dissymmetric pyrroles, 4-methyl-3-(2′-methoxy- 1′-naphthyl)pyrrole-2-carboxylates 1, were synthesized, characterized by X-ray crystallography and circular dichroism analysis, and applied to the first 'predetermined' synthesis of a chiral atropisomeric porphyrin with molecular asymmetry, (R,R,R,R)- and (S,S,S,S)- 2,7,12,17-tetramethyl-3,8,13,18- tetrakis(2′-methoxy-1′-naphthyl)porphyrin.

講演・口頭発表等

  • Synthesis of liquid crystalline inclusion complexes of luminescent poly(phenylenevinylene)s with amylose
    Kazumi Tamura, Masato Ikeda, Yoshio Furusho, Kento Okoshi, Sayaka Tanahara, Katsuhiro Maeda, Eiji Yashima, Eiji Yashima
    Polymer Preprints, Japan 2006年12月
    We have developed a convenient synthetic method of a luminescent poly(p-phenylenevinylene) (PPV)-amylose composite by direct polymerization of the precursor monomer in aqueous media in the presence of amylose. The PPV was encapsulated in the amylose tube and was soluble in DMSO. Moreover, we found that amylose, which is too flexible to form a liquid crystal (LC), exhibited an LC when the PPV was threaded into the amylose tube, resulting in a rigid rod assembly.
  • Oligoresorcinols-simplest water-soluble double helices in water
    Hidetoshi Goto, Hiroshi Katagiri, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Polymer Preprints, Japan 2006年12月
    The molecular strands of the oligoresorcinol 9mer self-assemble into double helices with the aid of aromatic interactions in water as characterized by 1H NMR and absorption spectroscopies together with the X-ray crystallographic study of the pentamer. The double helix formation is sensitive to the chain length, solvent composition, and temperature. Moreover, a bias in the screw sense of the double helices was achieved by covalently attaching chiral substituents to both ends of the molecular strands.
  • Synthesis and function of an artificial double-stranded helical polymer by use of amidinium-carboxylate salt bridge and coordination bond formations
    Masato Ikeda, Yoshie Tanaka, Takashi Hasegawa, Takashi Hasegawa, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Polymer Preprints, Japan 2006年10月
    By mixing a chiral m-terphenylamidine with two pyridine groups at both ends and an achiral m-terphenylcarboxylic acid with two pyridine groups at both ends in 1,1,2,2-tetrachloroethane, the corresponding supramolecular duplex was obtained. Polycondensation of the duplex and platinum(II) complex cis-Ph 2Pt(dmso) 2 in 1,1,2,2-tetrachloroethane yielded the doubly-stranded supramolecular polymer linked through Pt-pyridine bonds together with the salt bridges. The Cotton effect observed for the supramolecular polymer in the platinum complex region (400 nm) suggests that the supramolecular polymer adopts a double helical structure.
  • Double helices utilizing amidinium-carboxylate salt bridge formation: Double helix-to-double helix transformation using platinum(II) acetylide complexes as surrogate linkers
    Yoshio Furusho, Yoshie Tanaka, Masato Ikeda, Takashi Hasegawa, Hiroshi Katagiri, Eiji Yashima, Eiji Yashima
    Polymer Preprints, Japan 2006年10月
    We synthesized a novel optically active double helix consisting of complementary strands stabilized by the formation of chiral amidinium-achiral carboxylate salt bridge. Each strand has a frans-Pt(II) acetylide complex moiety with pendant triphenylphosphine ligands as the linker. The double helix was converted to another double helix by ligand exchange with cis-1,2- bis(diphenylphosphino)ethylene. Furthermore, the reductive elimination of the Pt(II) acetylide complex moieties generated the corresponding fully-organic double helix.
  • Solvent-induced switching of the helical chirality of poly((4- carboxyphenyl)acetylene) induced by an optically active amidine and memory of the diastereomeric macromolecular helicity
    Kazuhide Morino, Kenji Miura, Takashi Hasegawa, Takashi Hasegawa, Yoshie Tanaka, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Polymer Preprints, Japan 2006年10月
    We recently reported that helical poly-1 induced by an optically active amidine ((R,R)-2) showed helix-helix transition in response to temperature, and the diastereomeric right- and left-handed helices of poly-1 induced by (R,R)-2 could be separately memorized by the replacement of (R,R)-2 with achiral amines. In this study, we have found that the helix-sense of poly-1 induced by (R,R)-2 underwent a transition from one helix to another in response to the change of solvent composition. Furthermore, the right- and left-handed helices of poly-1 induced by (R,R)-2 in DMSO/pyridine (7/3) and DMSO/acetonitrile (7/3), respectively, could be memorized when (R,R)-2 was replaced by achiral amines.
  • Synthesis of cylindrical complexes through multi-component self-assembly driven-by amidinium-carboxylate salt bridge formation
    Yoshie Tanaka, Hiroshi Katagiri, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Polymer Preprints, Japan 2006年10月
    Upon mixing an amidine dimer and 1,3,5-benzenetricarboxylic acid at the ratio of 3:2, a cylindrical complex was formed through multi-component self-assembly driven by amidinium-carboxylate salt bridge formation. The cylindrical structure of the complex was confirmed by 1H NMR and mass spectroscopies. The X-ray crystallographic analysis of the complex revealed that it had a cavity with a diameter of ca. 1 nm and adopted a triply-stranded helical structure in the solid state.
  • Structure and aggregation behavior of oligophenol derivatives in water
    Hidetoshi Goto, Hiroshi Katagiri, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Polymer Preprints, Japan 2006年10月
    The 1H NMR signals of the oligoresorcinol 9mer in methanol-d 4 shifted to higher magnetic fields with an increase in D 2O content and the molar absorbance of the oligoresorcinol 9mer in methanol-d 4 decreased with increasing the amount of D 2O. Similarly, the oligoresorcinol 6mer exhibited an upfield shift and a hypochromic effect, whereas such effects could not be observed for the 3mer. The degrees of aggregation of the 3, 6, and 9mers in water were estimated to be 1. 1.5, and 1.9, respectively, by VPO measurements. Thus, the above results strongly suggest that the oligoresorcinols longer than the 3mer self-assemble to form bimolecular aggregates in water.
  • Synthesis and optical resolution of a double helicate consisting of ortho-linked oligophenol strands bridged by spiroborates
    Hiroshi Katagiri, Toyoharu Miyagawa, Toshihide Hasegawa, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Polymer Preprints, Japan 2006年10月
    A new spiroborate-based helicate was synthesized by treating an ortho-linked hexaphenol with NaBH 4 in 1,2-dichloroethane-ethanol. The X-ray crystallographic analysis revealed that it adopted a double-stranded helical structure bridged by two spiroborate units in the solid state. The ESI-MS and NMR studies showed that the complex retains the double-stranded helical structure in solution. The optical resolution of the helicate was achieved by diastereomeric salt formation using an enantiomerically-pure ammonium salt. The diastereomeric helicates were further converted to the corresponding enantiomers by cation exchange with an achiral ammonium cation without racemization.
  • Helicity induction on poly((4-carboxyphenyl)acetylene) with optically active amidines and its helixsense inversion and memory
    Takashi Hasegawa, Kazuhide Morino, Yoshio Furusho, Katsuhiro Maeda, Eiji Yashima, Eiji Yashima
    Polymer Preprints, Japan 2005年12月
    We have already found that the macromolecular helicity of cis-transoidal poly((4-carboxyphenyl)acetylene) (poly-1) forms a predominantly one-handed helix upon complexation with an optically active amine and the induced helical chirality can be memorized when the optically active amine is replaced by achiral amines. In this study, we have found that poly-1 can also form a prevailing one-handed helix in the presence of novel, optically active amidines such as N,N′-(R,R)-bis(phenylethyl)-2,4,6-triphenylbenzamidine ((R,R)-2). Furthermore, the helical conformation of poly-1 induced by (R,R)-2 inverts from one helix to another in response to temperature, and the right-and left-handed helices of poly-1 can be separately memorized by the replacement of (R,R)-2 with achiral amines.
  • Synthesis of inclusion complexes of conjugated polymers with amylose
    Masato Ikeda, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Polymer Preprints, Japan 2005年12月
    In this study, we investigated the synthesis of water-soluble amylose-PPV composites obtained by polymerization of the PPV monomer in an aqueous solution of amylose. The amylose-PPV composites were soluble in aqueous DMSO. 1H NMR spectra of the composite showed that the interior polymer consisted of the PPV units and a small amount of the precursor units. The composite showed the absorption and fluorescence being characteristic of PPV. In the CD spectra, the composite exhibited Cotton effects at around the absorption region of the PPV units, which suggests that the PPV units adopt a chiral twisted conformation. These results as well as other analytical ones such as SEC and XRD support the encapsulated structure of the PPV polymer in the amylose tube.
  • Structure and asymmetric catalysis of poly(metallo-salen complex)
    Takeshi Maeda, Yoshio Furusho, Toshikazu Takata, Toshikazu Takata
    Polymer Preprints, Japan 2005年12月
    Helical polymers based on metallo-ligand coordination, poly(binaphthyl- copper salen) complexes 1-Cu were synthesized from (R)-3,3'-diformylbinaphthols, diaminocyclohexane, and copper acetate. The helical conformation resulted from a restricted freedom of movement around polymer main chain by the metallo-ligand bonding. Elememtal analysis showed that the incorporation ratio of copper ions in the polymers for 1-Cu is quantitative. Both IR spectrum of 1-Cu and a few uniform series of peaks corresponding to 1-Cu (peak interval of 705 mass units) in the MALDI-TOF MS profile showed the reaction of poly(Schiff base) 1-2H with Cu(II) ions yielded corresponding poly(salen-Cu(II) complex) 1-Cu. UV-vis spectra, circular dichroism spectra, and MM calculations and EXAFS analysis of 1-Cu supported its helical structures. The catalysis of 1-Cu in the asymmetric cyclopropanation of styrene with diazoacetates was investigated. A significant enantiomeric enrichment in the products was confirmed in the reaction with ethyl diazoacetate, indicating the characteristic catalysis.
  • Design and synthesis of artificial double helices by a modular approach
    Yoshie Tanaka, Hiroshi Katagiri, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Polymer Preprints, Japan 2005年12月
    A chiral 2'-amidino-m-terphenyl dimer and an achiral 2'-carboxy-m-terphenyl dimer were synthesized. 1H NMR and ESI-MS in organic solvents such as chloroform showed that they formed the supramolecular duplex through the amidinium-carboxylate salt bridges. The X-ray crystallographic analysis of the duplex revealed that it adopted a right-handed double helical conformation in the solid state. The CD spectra of the duplex exhibited strong split Cotton effects around the absorbance of the diacetylene linkages (300-370 nm), suggesting that the duplex adopts the double helical structure in solution.
  • Helical structures induced on oligophenol derivatives in water
    Hidetoshi Goto, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Polymer Preprints, Japan 2005年12月
    Poly- and oligo(m-phenylene)s are known to form helical structures in the crystals, but are considered to take random-coil conformations in solution. In this study, water-soluble oligophenol derivatives (3-9merH) bearing hydroxy residues on the m-phenylene backbones were synthesized in a stepwise manner using transition metal-catalyzed cross-coupling reactions and the chiroptical properties of the oligomers were investigated by use of absorption and CD spectroscopies. Upon addition of various optically active compounds in water, the oligomers exhibited induced circular dichroisms, which suggested a predominant one-handed helix formation.
  • Construction of chiral duplex by use of interaction between amidine and carboxylic acid
    Yoshie Tanaka, Hiroshi Katagiri, Yoshio Furusho, Eiji Yashima, Eiji Yashima
    Polymer Preprints, Japan 2005年12月
    A chiral 2′-amidino-m-terphenyl dimer and an achiral 2′-carboxy-m-terphenyl dimer were synthesized. 1H NMR and ESI-MS showed that in organic solvents such as chloroform, they formed the supramolecular duplex through the amidinium-carboxylate salt bridges. The X-ray crystallographic analysis of the duplex revealed that it adopted a right-handed double helical conformation in the solid state. The CD spectra of the duplex exhibited strong split Cotton effects around the absorbance of the diacetylene linkages (300-370 nm), suggesting that the duplex adopts the double helical structure in solution.

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