詳細

今井　喜胤 （イマイ　ヨシタネ）

  • 理工学部 応用化学科　教授
Last Updated :2024/04/23

コミュニケーション情報 byコメンテータガイド

  • コメント

    光化学とキラルテクノロジーを組み合わせ、機能性円偏光発光(CPL)材料（3次元（3D）ディスプレイ用発光体など）の開発を行っています。

  • 報道関連出演・掲載一覧

    ＜報道関連出演・掲載一覧＞ ●2023/8/24 　電子デバイス産業新聞 　白金錯体のみを用いた円偏光LEDの開発について ●2023/4/27 　電子デバイス産業新聞 　フルカラー有機円偏光発光ダイオードの開発について 研究室HP:https://www.apch.kindai.ac.jp/laboratory/imai/

研究者情報

学位

  • 博士（工学）（大阪大学）

ホームページURL

科研費研究者番号

  • 80388496

J-Global ID

研究キーワード

  • 非古典的円偏光発光   磁気円偏光発光   ペプチド   キラル   超分子   蛍光   光学活性   ホスト   CPL   分子認識   円偏光二色性   固体   有機発光体   円偏光発光   発光   

現在の研究分野（キーワード）

    光化学とキラルテクノロジーを組み合わせ、機能性円偏光発光(CPL)材料（3次元（3D）ディスプレイ用発光体など）の開発を行っています。

研究分野

  • ナノテク・材料 / 機能物性化学

経歴

  • 2023年04月 - 現在  近畿大学理工学部応用化学科教授
  • 2015年04月 - 2023年03月  近畿大学理工学部応用化学科准教授
  • 2009年04月 - 2015年03月  近畿大学理工学部応用化学科講師
  • 2007年04月 - 2009年03月  近畿大学理工学部応用化学科助教
  • 2004年04月 - 2007年03月  近畿大学理工学部応用化学科助手
  • 2000年04月 - 2004年03月  科学技術振興事業機構創造科学技術推進事業黒田カイロモルフォロジーPJ博士研究員

学歴

  • 1998年04月 - 2000年03月   日本学術振興会特別研究員
  •         - 2000年03月   大阪大学大学院   工学研究科   分子工学専攻
  •         - 1995年03月   大阪大学   工学部   応用化学科

所属学協会

  • 日本化学会有機結晶部会   光化学協会   日本ペプチド学会   色材協会   日本油化学会   有機合成化学協会   高分子学会   日本化学会   

研究活動情報

論文

  • Seika Suzuki; Yuta Yamamoto; Maho Kitahara; Ryuta Shikura; Shigeyuki Yagi; Yoshitane Imai
    Journal of Materials Chemistry C 12 10 3430 - 3436 2024年02月 
    Electroluminescent devices such as circularly polarised organic light-emitting diodes (CP-OLEDs) fabricated by conventional methods do not exhibit adequate circularly polarised electroluminescence (CPEL) with high circular polarisation. Therefore, new approaches for CPEL and CP-OLED systems are needed. We developed an external-magnetic-field-driven CP-OLED device that emits red CPEL by integrating an achiral optically inactive phosphorescent platinum(ii) porphyrin luminophore (PtOEP) in the emission layer (EML). This magnetic CP-OLED system can simultaneously emit circularly polarised light with opposite rotations from the EML in the N-up and S-up directions of the applied magnetic field. By utilising this mechanism that allows simultaneous emission upon the application of a magnetic field and the reflection-reversal property of circularly polarized light, we may suppress the decrease in both the luminosity and circular polarisation of CPEL. The direction of rotation of CPEL was successfully reversed by switching the Faraday geometry of the applied magnetic field. This approach can promote the development of novel CP-OLED devices.
  • Masahiro Ikeshita; Shinya Watanabe; Seika Suzuki; Shota Tanaka; Shingo Hattori; Kazuteru Shinozaki; Yoshitane Imai; Takashi Tsuno
    Chemical Communications 2024年 
    A chiral platinum(II) complex with a helical Schiff-base [4]helicence ligand exhibits intense red circularly polarized phosphorescence (CPP) with a glum of 0.010 in the dilute solution state. The intense CPP...
  • Masahiro Ikeshita; Shinya Watanabe; Seika Suzuki; Maho Kitahara; Yoshitane Imai; Takashi Tsuno
    Chemistry – An Asian Journal 2023年12月 
    Boron complexes with Schiff‐base [4]helicene ligands were synthesized. These complexes were characterized by NMR spectroscopy and their helical molecular structures were unequivocally established by X‐ray diffraction (XRD) analysis. The helical boron complexes exhibited efficient photoluminescence under UV irradiation, and the circularly polarized luminescence (CPL) properties were investigated for optically pure samples. Density functional theory (DFT) calculations were conducted to further understand their photophysical properties including chiroptical responses.
  • Seika Suzuki; Kosuke Kaneko; Tomonori Hanasaki; Motohiro Shizuma; Yoshitane Imai
    ChemPhotoChem 2023年12月 
    To obtain chiral luminescent nematic liquid crystals (N*‐LCs), two sets of chiral perylene luminescent materials (R,R)/(S,S)‐N,N′‐bis(1‐cyclohexylethyl)perylene‐3,4,9,10‐tetracarboxylic diimide [(R,R)/(S,S)‐CPDI] and (R,R)/(S,S)‐N,N′‐bis(1‐phenylethyl)perylene‐3,4,9,10‐tetracarboxylic diimide [(R,R)/(S,S)‐BPP] were prepared and doped into a nematic liquid crystal (N‐LC), 5CB. The obtained liquid crystals N*‐LC‐CPDI and N*‐LC‐BPP emitted stronger circularly polarized luminescence (CPL) signals than the CPDI‐ and BPP‐containing chiral poly(methyl methacrylate) (PMMA) luminescent films owing to higher helical twist power. When a direct current (DC) electric field was applied to N*‐LC, a reversible CPL response was obtained due to the field‐induced phase transition from the chiral nematic phase to the nematic phase. This demonstrated the successful construction of an ''on–off–on'' CPL system based on a DC electric field and was attributed to the change in the liquid crystalline organization from a uniformly lying helical structure to a planar one. This work can provide an effective strategy for the development of functional CPL devices in which the CPL can be regulated by applying a DC electric field to the N*‐LC.
  • Yoshitane Imai; Yuta Yamamoto; Seika Suzuki; Kengo Hara; Maho Kitahara; Shigeyuki Yagi
    Organic Electronics 122 2023年11月 
    This study developed an external magnetic field–driven organic light-emitting diode (OLED) that can emit tunable circularly polarized electroluminescence (CPEL) by incorporating achiral optically inactive phosphorescent organic Pt(II) luminophores in the emission layer. The experimental results showed that in the proposed magnetic circularly polarized OLED (MCP-OLED) system, the luminescent color (luminescent wavelength) of magnetic CPEL (MCPEL) can be controlled by adjusting the concentration of achiral organometallic Pt(II) luminophores in the emission layer. Furthermore, MCPEL inversion was controlled by switching the Faraday geometric configuration of the applied magnetic field.
  • Masahiro Ikeshita; Nobuyuki Hara; Yoshitane Imai; Takeshi Naota
    Inorganic Chemistry 2023年08月
  • Masahiro Ikeshita; Yuki Tani; Maho Kitahara; Yoshitane Imai; Takashi Tsuno
    Bulletin of the Chemical Society of Japan 2023年08月
  • Maho Kitahara; Kengo Hara; Seika Suzuki; Hiroshi Iwasaki; Shigeyuki Yagi; Yoshitane Imai
    Organic Electronics 119 2023年08月 
    In this study, optically inactive racemic phosphorescent iridium(III) luminophores were embedded into the luminescent active layer of each device, and red–green–blue–yellow (RGBY)-full-color external magnetic field-driven circularly polarized electroluminescence (CPEL) was generated from organic light-emitting diodes (OLEDs). The optically inactive organic iridium(III) luminophores selected for this study were IrIII(piq)3 and IrIII(ppy)3, composed of achiral organic ligands with homoleptic tris-cyclometalated structures, and IrIII(F2-ppy)2(pic) and IrIII(BT)2(acac), with heteroleptic bis-cyclometalated structures, where piq, ppy, F2-ppy, pic, BT, and acac refer to 1-phenylisoquinolinate, 2-phenylpyridinate, 2-(4′, 6′-difluorophenyl)pyridinate, picolinate, 2-phenylbenzo[d]thiazolate, and acetylacetonate, respectively. As a result, full-color magnetic CPELs (MCPELs) were successfully generated from each magnetic circularly polarized OLED (MCP-OLED) with high efficiency, despite the use of chirality-free organic iridium(III) luminophores. In this MCP-OLED system, the direction of rotation of the MCPEL can be controlled by the ligand environment of the IrIII luminophore (homoleptic or heteroleptic structure) and the direction of the applied magnetic field (Faraday geometry).
  • Masahiro Ikeshita; Taichi Oka; Maho Kitahara; Seika Suzuki; Yoshitane Imai; Takashi Tsuno
    Chemistry Letters 52 7 556 - 559 2023年05月
  • Masahiro Ikeshita; Kota Orioku; Kana Matsudaira; Maho Kitahara; Yoshitane Imai; Takashi Tsuno
    ChemPhotoChem 2023年03月
  • Yoshitane Imai; Yuki Mimura; Yuki Motomura; Ryoya Ikemura; Motohiro Shizuma; Mizuki Kitamatsu
    Bulletin of the Chemical Society of Japan 96 3 268 - 273 2023年03月 
    It is important to optimize the photoexcited-state conformation of chiral luminescent molecules to enhance the intensity of circularly polarized luminescence (CPL) and control the direction of CPL rotation. In pyrenyl peptide luminophores, the intensity and sign of CPL is determined by the solvent and intramolecular distance between pyrenyl units in addition to peptide chirality. However, the control of CPL properties in water is difficult, and new methods to control CPL in water are required. In this study, we achieved amplification and control of the sign of excimer-origin CPL by adding γ-cyclodextrin to a flexible bipyrenyl peptide luminophore with two arginine groups in water.
  • Kenta Suzuki; Hiroki Fukuda; Hayato Toda; Yoshitane Imai; Yuki Nojima; Masashi Hasegawa; Eiji Tsurumaki; Shinji Toyota
    Tetrahedron 132 133243 - 133243 2023年02月
  • Kazuhisa Yamasumi; Kentaro Ueda; Yohei Haketa; Yusuke Hattori; Masayuki Suda; Shu Seki; Hayato Sakai; Taku Hasobe; Ryoya Ikemura; Yoshitane Imai; Yukihide Ishibashi; Tsuyoshi Asahi; Kazuto Nakamura; Hiromitsu Maeda
    Angewandte Chemie International Edition 62 8 2023年01月
  • Takumi Kuroda; Maho Kitahara; Shigeyuki Yagi; Yoshitane Imai
    Frontiers in Chemistry 11 2023年 
    An achiral optically inactive organic luminophore, 4CzIPN, exhibits circularly polarized thermally activated delayed fluorescence when photoexcited under an external magnetic field. By embedding this luminophore in an active emission layer, an external-magnetic-field-induced circularly polarized electroluminescent device is developed in this study. The Faraday geometry of the applied magnetic field completely controls the direction of rotation of 4CzIPN-derived circularly polarized luminescence and electroluminescence.
  • Yuna Kamimoto; Ryoya Ikemura; Yoshitane Imai; Norimitsu Tohnai; Shoko Yamazaki; Eiji Nakata; Hiroshi Takashima
    RSC Advances 13 1914 - 1922 2023年01月 [査読有り]
  • Masahiro Ikeshita; Taichi Oka; Maho Kitahara; Yoshitane Imai; Takashi Tsuno
    ChemPhotoChem 2022年12月
  • Kazuteru Usui; Nozomi Narita; Ryosuke Eto; Seika Suzuki; Atsushi Yokoo; Kosuke Yamamoto; Kazunobu Igawa; Naoko Iizuka; Yuki Mimura; Tomohiro Umeno; Shota Matsumoto; Masashi Hasegawa; Katsuhiko Tomooka; Yoshitane Imai; Satoru Karasawa
    Chemistry – A European Journal 2022年10月
  • Koki Ishii; Sakura Tsuchitani; Miyu Toyama; Hajime Shigeto; Shohei Yamamura; Takashi Ohtsuki; Yoshitane Imai; Mizuki Kitamatsu
    Bioorganic & medicinal chemistry letters 71 128838 - 128838 2022年09月 
    We developed a method for detecting DNA by excimer fluorescence from two peptide nucleic acids (PNAs) modified with a pyrene (Pyr). The two PNA-Pyr probes were prepared by solid-phase peptide synthesis, and we assessed fluorescence from the mixture of probes with DNA. From the results, excimer fluorescence derived from the two PNA-Pyr probes forming hybrids with the complementary DNA was observed, and the two probes showed the maximum excimer/monomer ratio when the probes and DNA were hybridized at a 1:1:1 ratio, indicating that the PNA-Pyr probes can detect target DNA. Furthermore, we adjusted the spatial arrangement between the two PNA-Pyr hybrids formed on the DNA to promote optimal excimer formation. As a result, optimal excimer formation was achieved by spacing the two nucleobases between the formed two hybrids and further inserting a hexamethylene linker (C6) between the PNA and Pyr of the PNA-Pyr probe on one side.
  • Qingyu Wang; Zhiyi Song; Masayoshi Bando; Takunori Harada; Yoshitane Imai; Hayato Toda; Naofumi Naga; Tamaki Nakano
    Macromolecules 55 13 5390 - 5402 2022年07月
  • Masahiro Ikeshita; Takuho Yamamoto; Shinya Watanabe; Maho Kitahara; Yoshitane Imai; Takashi Tsuno
    Chemistry Letters 2022年06月
  • Aoba Kanesaka; Yuki Nishimura; Akira Yamaguchi; Yoshitane Imai; Toshiko Mizokuro; Hiroyuki Nishikawa
    Bulletin of the Chemical Society of Japan 95 5 751 - 758 2022年05月
  • Ryo Amasaki; Maho Kitahara; Takahiro Kimoto; Michiya Fujiki; Yoshitane Imai
    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY 2022 10 2022年04月 
    Ambidextrous magnetic circularly polarized luminescence (MCPL) and redshift in photoluminescence (PL) spectra are observed from two types of achiral soluble diamagnetic perovskite-Pb-quantum dots in toluene solution at room temperature, when subjected to external north-up and south-up magnetic fields of 1.7 T. The magnitude of the MCPL, g(MCPL), is in the order of |g(MCPL)|=10(-3) within a wavelength range of 480-580 nm. The wavelength and the sign of the MCPL spectra can be controlled by the types of perovskite constituent atom and the direction of the magnetic field, respectively.
  • Risa Honda; Nobuyuki Hara; Yoshitane Imai; Ken-ichi Sugiura
    CHEMISTRYSELECT 7 8 2022年02月 
    Treatment of p-toluenesulfonic acid on bipyrenol in PhCl gave a pyrene-fused furan. The expansion of the molecule induced a narrow HOMO-LUMO gap, multiple redox processes showing both oxidation and reduction, and a bathochromic shift in the absorption spectrum. A small Stokes shift was caused by the rigidity of the molecule. The structures and electronic states were estimated by theoretical considerations. We found that the heteroatom containing a [5]helicene molecule shows racemization through a planar transition state.
  • Masahiro Ikeshita; Hongxi He; Maho Kitahara; Yoshitane Imai; Takashi Tsuno
    RSC Advances 12 53 34790 - 34796 2022年 
    Circularly polarized luminescence properties of chiral boron difluoride complexes bearing a diethylamino group successfully controlled by external environment.
  • Masahiro Ikeshita; Takato Suzuki; Kana Matsudaira; Maho Kitahara; Yoshitane Imai; Takashi Tsuno
    Physical Chemistry Chemical Physics 2022年 
    A series of chiral Schiff-base boron difluoride complexes was synthesized and their photophysical properties were examined. These complexes showed multi-colour (blue, yellow and red) photoluminescence in solution and in the...
  • Masahiro Ikeshita; Momo Mizugaki; Takahiro Ishikawa; Kana Matsudaira; Maho Kitahara; Yoshitane Imai; Takashi Tsuno
    Chemical Communications 2022年 
    The handedness of circularly polarized luminescence (CPL) of Zn(II) complexes with chiral Schiff-base ligand can be controlled by coordination geometry changes in solution and in the solid state. The relationships...
  • Zhiyi Song; Hiroyasu Sato; Adriana Pietropaolo; Qingyu Wang; Shuhei Shimoda; Heshuang Dai; Yoshitane Imai; Hayato Toda; Takunori Harada; Yukatsu Shichibu; Katsuaki Konishi; Masayoshi Bando; Naofumi Naga; Tamaki Nakano
    CHEMICAL COMMUNICATIONS 58 7 1029 - 1032 2022年01月 
    Optically active linear polyurethane and a cyclic dimer were synthesized from 2,7-diisocyanatofluorene and 2,2 '-dihydroxy-1,1 '-binaphthyl. The circular dichroism (CD) spectral intensity of the polymer was amplified at a higher concentration through aggregate formation, while circularly polarized light (CPL) emission was not enhanced. The cyclic dimer's CPL emission was largely amplified (g(lum) 1.1 x 10(-2)) due to intermolecular excimer formation through aggregation, while the CD intensity was not affected.
  • Kengo Hara; Ami Morimoto; Kana Matsudaira; Satoko Suzuki; Shigeyuki Yagi; Michiya Fujiki; Yoshitane Imai
    CHEMPHOTOCHEM 2022年01月 
    This work reports the development of external magnetic field (EMF) driven, ambidextrous, circularly polarized electroluminescence (CPEL) devices, by embedding racemic mixtures of phosphorescent organoiridium(III) emitters in the active emitting layer. Homoleptic tris-cyclometalated Ir(III)(ppy)(3) and heteroleptic bis-cyclometalated Ir(III)(ppy)(2)(acac) (ppy = 2-phenylpyridinate, acac = acetylacetonate) were used as the representative organoiridium(III) compounds. Chiroptical inversion of CPEL was influenced by the ligand environment in the Ir(III) complexes (homoleptic or heteroleptic), as well as the Faraday geometry.
  • Masahiro Ikeshita; Sho Furukawa; Takahiro Ishikawa; Kana Matsudaira; Yoshitane Imai; Takashi Tsuno
    CHEMISTRYOPEN 11 4 2022年01月 
    The relationship between the coordination geometry and photophysical properties of trans-bis[(beta-iminomethyl)naphthoxy]platinum(II) was investigated both experimentally and theoretically. A series of platinum(II) complexes with differently substituted iminomethyl groups were synthesized, and their photophysical properties were examined in solution, in the crystalline, and in the PMMA film-dispersed state, respectively (PMMA=poly(methyl methacrylate)). These complexes showed structure-dependent emission spectra, in which the color of the luminescence in the crystalline state varied over a range of about 40 nm depending on the specific bowl-shaped molecular structure. The chiral complexes with (R,R)- and (S,S)-configurations were found to have structure-dependent chiroptical properties both in solution and the PMMA film-dispersed state such that the intensity of circular dichroism (CD) and circularly polarized luminescence (CPL) were enhanced with bulky cyclic substituents at the nitrogen atoms. A theoretical study using density functional theory (DFT) and time-dependent (TD)-DFT calculations revealed that the enhancement of chiroptical responses is due to the amplification of the magnetic dipole moment caused by the distortion of the square planar geometry.
  • Takahiro Kimoto; Mako Okuno; Naoyoshi Nunotani; Nobuhito Imanaka; Michiya Fujiki; Yoshitane Imai
    Inorganic Chemistry Communications 134 109034 - 109034 2021年12月
  • Maho Kitahara; Kohei Mishima; Nobuyuki Hara; Motohiro Shizuma; Aoba Kanesaka; Hiroyuki Nishikawa; Yoshitane Imai
    ASIAN JOURNAL OF ORGANIC CHEMISTRY 10 11 2969 - 2974 2021年11月 
    Three types of chiral perylene diimide luminophores bearing ethynyl, phenyl, and ethynylphenyl substituents (BPP-Ethy, BPP-Ph, and BPP-EthyPh) at the bay positions were prepared. The chiroptical properties of the compounds in their solution (in CHCl3) and polymethyl methacrylate (PMMA)-film solid states were investigated. Similar to the chiral BPP molecules bearing no substituents at the bay position, BPP-Ethy, BPP-Ph, and BPP-EthyPh luminophores emitted no clear circularly polarized luminescence (CPL) in CHCl3 solution. In contrast, the chiral BPP-Ethy, BPP-Ph, and BPP-EthyPh luminophores exhibited intense aggregation-induced enhanced CPL (AIEnh-CPL) in the PMMA-film state; BPP exhibited similar properties. Although the four luminophores were of the same absolute configurations, the CPL signs of the chiral BPP-EthyPh were opposite to those of BPP, BPP-Ethy, and BPP-Ph. This could be attributed to the effects of the substituents at the bay position.
  • Yoshitane Imai
    CHEMPHOTOCHEM 5 11 969 - 973 2021年11月 
    In general, circularly polarized luminescence (CPL) is generated by a chiral luminophore, that is, chiral structures and chiral packing styles are essential for organic and organometallic luminophores to exhibit CPL properties. However, it is difficult to introduce a chiral structure into inorganic and metal-cluster luminophores. In this minireview, we have reported magnetic circularly polarized luminescence (MCPL) systems. Upon the application of an external magnetic field, achiral and racemic luminophores too can exhibit MCPL. Such MCPL systems are beneficial for developing versatile CPL systems from various luminophores, which could prospectively cover a wide range of UV-visible-near-infrared regions.
  • Maho Kitahara; Seika Suzuki; Kana Matsudaira; Shigeyuki Yagi; Michiya Fujiki; Yoshitane Imai
    CHEMISTRYSELECT 6 41 11182 - 11187 2021年11月 
    The development of phosphorescent organometallic molecules, capable of full-colour circularly polarised luminescence with a controlled polarised sign in the absence of any chiral chemical influences, presents a significant scientific and engineering challenge. The current study describes the first red-green-blue-yellow (RGBY) coloured, nearly mirror-image magnetic circularly polarised luminescence (MCPL) in dimethyl sulfoxide and dichloromethane, from four optically inactive Iridium(III) complexes viz. Ir(III)(piq)(3), Ir(III)(ppy)(3), Ir(III)(F-2-ppy)(2)(pic), and Ir(III)(BT)(2)(acac), bearing achiral organic cyclometalated and ancillary ligands. The absolute value of the anisotropy factors, |g(MCPL)|, ranging from 0.9x10(-3) to 2.5x10(-3) in the presence of an external 1.6 T magnetic field was nearly identical to the enantiomerically pure Iridium (III) complexes at zero-magnetic fields. Unexpectedly, when the same north-up/south-up Faraday geometries were used, the MCPL signs were inverted due to the achiral ligands.
  • Suguru Ito; Ryohei Sekine; Masayasu Munakata; Masatoshi Asami; Takashi Tachikawa; Daiki Kaji; Kohei Mishima; Yoshitane Imai
    ChemPhotoChem 5 10 876 - 876 2021年10月
  • Suguru Ito; Ryohei Sekine; Masayasu Munakata; Masatoshi Asami; Takashi Tachikawa; Daiki Kaji; Kohei Mishima; Yoshitane Imai
    CHEMPHOTOCHEM 5 10 920 - 925 2021年10月 
    Despite the recent increased interest in organic small molecule luminophores that exhibit circularly polarized luminescence (CPL) or mechanochromic luminescence (MCL), MCL behavior in chiral luminophores that display solid-state CPL still remains elusive. Herein, it is reported that a chiral diamine-linked bispyrene derivative exhibits a rare MCL behavior in response to two different types of mechanical stimuli, namely utrasonication and grinding. Moreover, an unprecedented switching of solid-state CPL has been achieved for the chiral bispyrene between two states that can respond to the different mechanical stimuli. These findings should help to advance the development of practical CPL materials.
  • Hayato Toda; Shuhei Otake; Akari Ito; Makoto Miyasaka; Michiya Fujiki; Yoshitane Imai
    CHEMPHYSCHEM 22 20 2058 - 2062 2021年10月 
    This paper reports the first magnetic circularly polarized luminescence (MCPL) characteristics of racemic helicenes, including four unsubstituted [n]helicenes (n=3,4,5,7) and two [4]helicene derivatives bearing methoxy substituents, in tetrahydrofuran (THF) and dimethyl sulfoxide (DMSO) solutions. The value of |g(MCPL)| was calculated to be of the order of 10(-3) T-1 within 350-430 nm under the north-up (N-up) and south-up (S-up) Faraday geometries in an external magnetic field of 1.6 T. The [n]-dependent MCPL signs were altered by the N-up and S-up geometries.
  • Masashi Hasegawa; Yuki Ishida; Hiroaki Sasaki; Sumire Ishioka; Kazuteru Usui; Nobuyuki Hara; Maho Kitahara; Yoshitane Imai; Yasuhiro Mazaki
    Chemistry – A European Journal 2021年09月
  • Mika Sawai; Sayaka Matsumoto; Yuki Mimura; Yoshitane Imai; Shoko Yamazaki; Nobuko Kanehisa; Norimitsu Tohnai; Eiji Nakata; Hiroshi Takashima
    Journal of Inclusion Phenomena and Macrocyclic Chemistry 102 1-2 133 - 142 2021年09月
  • Kohei Mishima; Daiki Kaji; Michiya Fujiki; Yoshitane Imai
    CHEMPHYSCHEM 22 17 1728 - 1737 2021年09月 
    Herein, magnetic circularly polarized luminescence (CPL) (MCPL) spectroscopy was conducted to analyze an Eu-III(hfa)(3) complex with three chiral P-III-ligands. Resultantly, (R)-chirality luminophores with S-up orientation and (S)-chirality luminophores with N-up orientation were observed to possess symmetrical mirror image spectra, i. e., they were enantiomers. Similarly, the (R)-chirality luminophores with N-up orientation and the (S)-chirality luminophores with S-up orientation were also enantiomers. Contrarily, (R)-S-up and (S)-S-up were diastereomers and did not possess a mirror-image relationship. Likewise, (R)-N-up and (S)-N-up were diastereomers. The J-dependency of g(MCPL) and g(CPL) datasets suggested that the N-up/S-up external magnetic field, with the aid of chiral P-III-ligands, increased the g(MCPL) values by two-to sixteen-fold and modulated the g(MCPL) signs at J=1-4. Additionally, the origins of the nonideal mirror-symmetric CPL and MCPL spectral characteristics of Eu-III(hfa)(3) with three chiral P-III-ligands were discussed in terms of parity (space-inversion, P)-symmetry, time-reversal (T)-symmetry, and PT-symmetry laws.
  • Yoshitane Imai
    CHEMISTRY LETTERS 50 6 1131 - 1141 2021年06月 
    Circularly polarized luminescence (CPL) has attracted significant attention in the fields of chiral photonics and optoelectronic materials science. In a CPL-emitting system, a chiral luminophore derived from chiral molecules is usually essential, and a pair of enantiomeric luminophores is indispensable for the typical selective-emission of right- and left-handed CPL. This review focuses on non-classical CPL systems that do not use pairs of enantiomers and introduces symmetry-breaking CPL systems that do not use optically active molecules, and covers photoexcited chiral-switching, spontaneous-resolution, crypto-chirality, and magnetic CPL.
  • Tomokazu Kinoshita; Yoshitane Imai; Gaku Fukuhara
    JOURNAL OF PHYSICAL CHEMISTRY B 125 22 5952 - 5958 2021年06月 
    Hydrostatically pressurized spectroscopic and lifetime decay analyses of optically active perylene bisimides were demonstrated in the pressure range of 0.1-320 MPa to show a pi-stacked aggregation. The hydrostatic pressure-induced excitation and circular dichroism spectral changes of the fluorescence perylene dye enabled us to differentiate the slight pressure-sensitive aggregates. This work will lead to a new strategy for creating a pressure-responsive supramolecular polymerization material.
  • Takahiro Kimoto; Yuki Mimura; Michiya Fujiki; Yoshitane Imai
    CHEMISTRY LETTERS 50 5 916 - 919 2021年05月 
    Herein, we report an example of red-green-blue full-color magnetic circularly polarized luminescence (MCPL) from three inorganic luminophores in their solid powder form and upon embedding in poly(methyl methacrylate) films; they were examined in the photoexcited state under the Faraday geometry with a 1.6 T permanent magnet in the absence of chiral chemical influences. The MCPL signs associated with g(MCPL) = +/- 6 x 10(-3) were controllable solely by changing north-up and south-up geometries.
  • Nobuyuki Hara; Maho Kitahara; Takaharu Sugimura; Hayato Toda; Motohiro Shizuma; Akari Ito; Makoto Miyasaka; Michiya Fujiki; Yoshitane Imai
    Physical chemistry chemical physics : PCCP 2021年03月 
    Diamagnetic achiral pyrene and phenanthrene derivatives substituted with electron-donating hydroxyl/methoxy groups and electron-withdrawing carboxylic acid groups exhibited clear magnetic circularly polarised luminescence (MCPL) spectra at 360-460 nm in dilute solvents upon the application of N-up and S-up Faraday geometries under an external magnetic field of 1.6 T. Their MCPL signs were also susceptible upon application of the same Faraday geometry.
  • Kana Matsudaira; Atsushi Izumoto; Yuki Mimura; Yoshiro Kondo; Satoko Suzuki; Shigeyuki Yagi; Michiya Fujiki; Yoshitane Imai
    Physical chemistry chemical physics : PCCP 23 9 5074 - 5078 2021年03月 
    Optically inactive, paramagnetic Ir(iii)(ppy)3 and Ir(iii)(ppy)2(acac) (ppy: 2-phenylpyridinate and acac: acetylacetonate) showed nearly mirror-symmetric magnetic circularly polarised luminescence (MCPL) spectra in dilute dichloromethane and dimethyl sulfoxide under N-up and S-up geometries in a 1.6-T magnetic field. However, the MCPL signs of Ir(iii)(ppy)3 and Ir(iii)(ppy)2(acac) under the same N-up (or S-up) Faraday geometry were opposite to each other when one ppy was replaced with an acac. This ligand exchange approach provides facile control of the MCPL sign, irrespective of the Faraday geometry.
  • Yuki Mimura; Michiya Fujiki; Yoshitane Imai
    CHEMICAL PHYSICS LETTERS 767 2021年03月 
    Ambidextrous magnetic circularly polarized luminescence (MCPL) is observed for the first time from five kinds of achiral soluble diamagnetic CdS/ZnS core-shell quantum dots in toluene and aqueous solutions, dispersed in poly(methyl methacrylate) film, and as solid powders when subjected to external north-up and south-up magnetic fields of 1.6 Tesla. The magnitude of MCPL, g(MCPL), is on the order of vertical bar g(MCPL)vertical bar = 10(-3) between 400 and 460 nm. The sign of these MCPL spectra is controlled solely by the direction of the magnetic field.
  • Kana Matsudaira; Yuki Mimura; Junichi Hotei; Shigeyuki Yagi; Ken-ichi Yamashita; Michiya Fujiki; Yoshitane Imai
    CHEMISTRY-AN ASIAN JOURNAL 16 8 926 - 930 2021年03月 
    The magnetic circularly polarized luminescence (MCPL) and photoluminescence (PL) spectra of achiral (2,3,7,8,12,13,17,18-octaethylporphyrinato)platinum(II), PtOEP, and [2-(4 ',6 '-difluorophenyl)pyridinato-N,C-2 ']platinum(II) acetylacetonate-O,O, F-2-ppyPt(acac), in toluene and dichloromethane solutions were recorded under an external magnetic field of 1.6 T with N-up and S-up Faraday geometries. The MCPL signs of PtOEP and F-2-ppyPt(acac) were controlled solely by changing the N-up and S-up geometries. The MCPL/PL wavelengths of F-2-ppyPt(acac) in solutions were varied by the ratio of the monomeric and excimeric species.
  • Takashi Otani; Takuma Sasayama; Masashi Horiuchi; Shunnosuke Okauchi; Hidetoshi Kawai; Maho Kitahara; Yoshitane Imai; Takanori Shibata
    HELVETICA CHIMICA ACTA 104 4 2021年03月 
    We achieved a two-type synthesis of quinoxaline-fused polyaza[5]- and [7]helicenes through consecutive N-H/C-H coupling with a hypervalent iodine reagent as a key reaction. By fusing electron-deficient quinoxaline, these polyazahelicenes constitute an efficient donor-acceptor type of molecule with absorption edges that reach up to approximately 650 nm. Evaluating the chiroptical properties reveals that the polyazahelicene exhibits a rare orange circularly polarized glow with a luminescence dissymmetry factor (g(lum) value) of 0.003.
  • Yuki Nojima; Masashi Hasegawa; Nobuyuki Hara; Yoshitane Imai; Yasuhiro Mazaki
    CHEMISTRY-A EUROPEAN JOURNAL 2021年02月 
    Double-twisted cyclic binaphthyls, in which two naphthalenes are tethered by -O(CH2)(n)O- linkage (n=1-3), have been synthesized. X-ray analyses and DFT calculations revealed a tightly constrained stereogenic figure-eight geometry. Tethering of two naphthalenes by short linkage forces a small dihedral angle, and the cyclic binaphthyls with short tether (n=1, 2) exhibit remarkable boosting of the g(lum) value (1.0-1.6x10(-2)) in circularly polarized luminescence (CPL) and unusual g(lum)/g(abs) ratios (0.93-1.3). These experimental high |g(lum)| values are in accord with the results of excited state TD-DFT calculations, which show transannular interactions and that consequent extensive delocalization occurs throughout the figure-eight pi-core. As a result, the present figure-eight luminophore promote the elongation of the magnetic transition dipole moment that results in significant increases in g(lum) values.
  • Kenta Sato; Masashi Hasegawa; Yuki Nojima; Nobuyuki Hara; Tomohiko Nishiuchi; Yoshitane Imai; Yasuhiro Mazaki
    Chemistry – A European Journal 27 4 1160 - 1160 2021年01月
  • Kenta Sato; Masashi Hasegawa; Yuki Nojima; Nobuyuki Hara; Tomohiko Nishiuchi; Yoshitane Imai; Yasuhiro Mazaki
    CHEMISTRY-A EUROPEAN JOURNAL 27 4 1164 - 1164 2021年01月 
    Invited for the cover of this issue are Masashi Hasegawa, Yoshitane Imai, Yasuhiro Mazaki and co-workers at Kitasato University, Kindai University and Osaka University. The image depicts a stereogenic twisted cycloparaphenylene that exhibits circularly polarized luminescence in a polymethyl methacrylate thin film. Read the full text of the article at 10.1002/chem.202004283.
  • Yuki Mimura; Yuki Motomura; Mizuki Kitamatsu; Yoshitane Imai
    ASIAN JOURNAL OF ORGANIC CHEMISTRY 10 1 149 - 153 2021年01月 
    Determining the conformation of a chiral luminescent molecule in its ground state as well as in its photoexcited state is difficult. In the case of a pyrenyl peptide, the sign of its circularly polarised luminescence (CPL) is determined by the solvent or the intramolecular distance between its pyrenyl units; consequently, a new method for controlling CPL in water is required. Herein, we report that chiral LL-oligopeptide luminophores bearing two fluorescent pyrenyl and hydrophilic arginine units exhibit clear excimer-origin circularly polarised luminescence (CPL) at 480-510 nm in aqueous solution. The CPL sign is tuneable by altering the number and positions of the arginine units on the edges of the chiral peptide backbone.
  • Kenta Sato; Masashi Hasegawa; Yuki Nojima; Nobuyuki Hara; Tomohiko Nishiuchi; Yoshitane Imai; Yasuhiro Mazaki
    CHEMISTRY-A EUROPEAN JOURNAL 27 4 1323 - 1329 2021年01月 
    A curved stereogenic [6]paraphenylene ([6]PP), anchoring a chiral binaphthyl scaffold at 7,7'-positions, was prepared and investigated for its properties as a solid-state circularly polarized luminescence (CPL) dye. X-ray analysis revealed a helically twisted structure of PP units induced by axial chirality of binaphthyl framework. The curved [6]PP exhibits fluorescence in powder and polymethyl methacrylate (PMMA) film as well as solution. A significant increase in quantum yield was observed for a non-fluid PMMA film owing the suppression of the molecular motion. The g(CPL) values of the dye in solution and as PMMA film were almost the same (4.3-4.4x10(-3)) and lager than that in powder. TD-DFT calculations in the excited state suggest that the exciton can be delocalized into a twisted PP unit to produce a larger magnetic transition dipole moment.
  • Hayato Toda; Nobuyuki Hara; Michiya Fujiki; Yoshitane Imai
    RSC ADVANCES 11 3 1581 - 1585 2021年01月 
    Although 12 diamagnetic fused aromatics with or without substituents exhibit mirror-symmetric magnetic circularly polarised luminescence (MCPL) through N-up and S-up Faraday geometries under a magnetic field intensity of 1.6 T, their signs (single and multiple) and magnitudes depend strongly on either the aromatic structures or the peripheral positions of the substituents.
  • Yuki Mimura; Yuki Motomura; Mizuki Kitamatsu; Yoshitane Imai
    PROCESSES 8 12 2020年12月 
    Chiral organic and organometallic luminophores that possess circularly polarized luminescence (CPL) properties in the near-ultraviolet to near-infrared region have several useful applications. However, the CPL properties are subject to inherent factors of the compounds; to date, studies on the CPL properties influenced by amino acids and peptides are scarce. Consequently, we developed peptide-pyrene organic luminophores exhibiting various CPL properties. It is conceivable that the peptide-pyrene organic luminophores can be obtained as aggregates when dissolved in a solution. It is also possible that the formation of aggregates makes it difficult to accurately examine the CPL of the peptide in the solution. This study showed that the introduction of sterically hindered 2-aminoisobutyric acid (Aib) units into the peptide backbone inhibits aggregate formation. The resulting luminophores exhibit CPL properties owing to the presence of pyrene units. The results of this study can form a basis for the design of future materials that use peptide-pyrene organic luminophores.
  • Yoshitane Imai
    SYMMETRY-BASEL 12 11 2020年11月 
    Circularly polarized luminescence (CPL) has attracted significant attention in the fields of chiral photonic science and optoelectronic materials science. In a CPL-emitting system, a chiral luminophore derived from chiral molecules is usually essential. In this review, three non-classical CPL (NC-CPL) systems that do not use enantiomerically pure molecules are reported: (i) supramolecular organic luminophores composed of achiral organic molecules that can emit CPL without the use of any chiral auxiliaries, (ii) achiral or racemic luminophores that can emit magnetic CPL (MCPL) by applying an external magnetic field of 1.6 T, and (iii) circular dichroism-silent organic luminophores that can emit CPL in the photoexcited state as a cryptochiral CPL system.
  • Genki Namba; Yuki Mimura; Yoshitane Imai; Ryo Inoue; Yasuhiro Morisaki
    CHEMISTRY-A EUROPEAN JOURNAL 26 65 14871 - 14877 2020年11月 
    Optically active X-shaped molecules based on the planar chiral [2.2]paracyclophane building block were prepared, in which di(methoxy)terphenyl units were stacked on the central benzene rings. At 25 degrees C, anisolyl rings freely rotate in solution, while in the crystal form, they are fixed by intramolecular CH-pi interactions, thereby leading to the expression of the axial chirality, i.e., propeller chirality was exhibited by the planar chiral [2.2]paracyclophane moiety. The X-shaped molecule exhibited good circularly polarized luminescence (CPL) profiles with moderate Phi(PL) and a large g(lum) value in the order of 10(-3) at 25 degrees C, in solution. In contrast, at -120 degrees C, dual CPL emission with opposite signs was observed. According to the theoretical studies, the rotary motion of the anisolyl units is suppressed in the excited states, and so emission from two isomers could be observed. These results demonstrate that the axial chirality was controlled by the planar chirality, leading ultimately to propeller chirality.
  • Yuki Mimura; Yuki Motomura; Mizuki Kitamatsu; Yoshitane Imai
    TETRAHEDRON LETTERS 61 39 2020年09月 [査読有り]
     
    We prepared eight novel chiral arginine-bipyrenyl oligopeptides with different intramolecular distances between two organic luminophore fluorescent pyrene units and investigated their chiroptical properties in water at ambient temperature. These luminophores are highly soluble in water because of the presence of two arginine units; because they carry two pyrene units, they emit strong excimer circularly polarized luminescence (CPL) in the range of 450-600 nm (vertical bar gCPL vertical bar approximate to (0.1-0.5) x 10(-2)). When the number of atoms between the two intramolecular pyrenes units was even, the sign of the CPL signals was negative (-), whereas when the atom number was odd, the sign of the CPL signals was positive (+), even in water. (C) 2020 Elsevier Ltd. All rights reserved.
  • Kei Fujise; Eiji Tsurumaki; Gaku Fukuhara; Nobuyuki Hara; Yoshitane Imai; Shinji Toyota
    CHEMISTRY-AN ASIAN JOURNAL 15 16 2456 - 2461 2020年08月 [査読有り]
     
    Polycyclic aromatic hydrocarbons consisting of three fused anthracene units were designed as new pi-conjugated compounds having helical structures. These expanded helicenes were synthesized by Pt-catalyzed cycloisomerization of the corresponding ethynyl-substituted precursors. The nonplanar and helical structure was confirmed by X-ray analysis and DFT calculations, and the barrier to helical inversion was estimated to be 34 kJ mol(-1). The enantiomers of the diphenyl derivative were successfully resolved by chiral HPLC. Enantiopure samples showed good chiroptical performance in the CD (|Delta epsilon| 1380 L mol(-1)cm(-1)) and CPL (|g(lum)| 0.013) spectra, and these values were considerably large for simple organic molecules. The unique chiroptical properties are discussed on the basis of the molecular structure and the electronic state with the aid of time-dependent DFT calculations.
  • Hana Okada; Nobuyuki Hara; Daiki Kaji; Motohiro Shizuma; Michiya Fujuiki; Yoshitane Imai
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 22 25 13862 - 13866 2020年07月 [査読有り]
     
    Two chiral binaphthyl (BNp) derivatives bearing oppositely oriented ester linkers to two pyrene (Py) moieties [(R)/(S)-1 and (R)/(S)-2] enabled Py-origin circularly polarized luminescence (CPL), magnetic CPL (MCPL), and circular dichroism (CD). (R)-1 that exhibited (-)-sign CD showed (+)-sign Py-excimer CPL but did not exhibit MCPL. Conversely, (R)-2, with (-)-sign CD, did not show excimer-origin CPL, but exhibited clear Py-monomer MCPL.
  • Hiroki Yoshikawa; Gaku Nakajima; Yuki Mimura; Takahiro Kimoto; Yoshiro Kondo; Satoko Suzuki; Michiya Fujiki; Yoshitane Imai
    DALTON TRANSACTIONS 49 28 9588 - 9594 2020年07月 [査読有り]
     
    Five optically inactive Eu-III(hfa)(3), Tb-III(hfa)(3), Eu-III(acac)(3)center dot Phen, Tb-III(acac)(3)center dot Phen and Eu-III(hfa)(3)center dot BDPB (hfa: hexafluoroacetylacetonate, acac: acetylacetonate, BDPB: 2,2'-bis(diphenylphosphino)biphenyl and Phen: phenanthroline) complexes showed clear mirror-image magnetic circularly polarised luminescence (MCPL) spectra in CHCl3, acetone, and DMF solutions, in a poly(methyl methacrylate) film, a KBr pellet and bulk powder at room temperature under 1.6 T as an external magnetic field with Faraday geometry. The signs of the MCPL signals were determined via N-up and S-up geometries. The g(MCPL) values of Eu-III(hfa)(3) and Tb-III(hfa)(3) were +/-(0.046-2.0) x 10(-2) T-1 at the D-5(0) -> F-5(J) transitions (J = 1-4) in the range of 590 nm and 703 nm and +/-(0.0081-1.0) x 10(-2) T-1 at the D-5(4) -> F-7(J) transitions (J = 3-6) in the range of 480 nm and 630 nm, respectively. Interestingly, the photoluminescence spectra of Eu-III(hfa)(3) and Tb-III(hfa)(3) in CHCl3 and acetone under 1.6 T considerably redshifted by 10-114 cm(-1), while those of Eu-III(acac)(3)center dot Phen and Tb-III(acac)(3)center dot Phen did not reveal detectable redshifts.
  • Hiroaki Mizuno; Mizuki Kitamatsu; Yoshitane Imai; Gaku Fukuhara
    CHEMPHOTOCHEM 4 7 502 - 507 2020年07月 [査読有り]
     
    Fluorogens or luminescence materials that show manipulatable emissive responses toward various external stimuli, such as, temperature, solvent, salt, and pH, hold great promise for some applications. Hydrostatic pressure, as one external stimulus, can manipulate conformational changes in the ground state and subsequent photophysical properties in the excited state of an appropriately designed material. In this study, we controlled not only the chiroptical but also the emissive properties of smart fluorescence materials, namely peptide-pyrene conjugates, and also examined the origins of the optical properties by means of several spectroscopic techniques under high pressure. The location of the chromophores and the appended bulky substituent on the peptide scaffold play pivotal roles in influencing the pressure-induced properties. The present work gives new perspectives for energy-related luminescent materials which respond to hydrostatic pressure, providing an attractive alternative to other common external stimuli.
  • Daiki Kaji; Hana Okada; Nobuyuki Hara; Yoshiro Kondo; Satoko Suzuki; Makoto Miyasaka; Michiya Fujiki; Yoshitane Imai
    CHEMISTRY LETTERS 49 6 674 - 676 2020年06月 [査読有り]
     
    Molecular pyrene, 1-hydroxylpyrene, and 2-hydroxypyrene in chloroform and embedded in poly(methyl methacrylate) film reveal mirror-image magnetic circularly polarized luminescence (MCPL) when south (S)-up or north (N)-up direction of the longitudinal external magnetic field of 1.6 T to unpolarized incident light (Faraday geometry) is employed. The vertical bar g(MCPL)vertical bar magnitude is on the order of 10(-3) T-1 in 374-416 nm. The sign of MCPL is controlled by the S-up and N-up geometry and by the position (1- or 2-) of the hydroxy group.
  • Daiki Kaji; Masumi Kitayama; Nobuyuki Hara; Keishiro Yoshida; Sae Wakabayashi; Motohiro Shizuma; Kazunori Tsubaki; Yoshitane Imai
    JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY 397 2020年06月 [査読有り]
     
    The circularly polarized luminescence (CPL) signs of Eu(III) luminophores coordinated to axially chiral binaphthyl derivatives carrying acetic acid residues [(R,R,R)-4] were inverted compared to those bearing compounds (R)-1-3 by inserting bulky naphthalene units into the binaphthyl backbone. The suitable steric difference between the phenyl group and the highly bulky naphthalene group on the binaphthyl backbone causes a chiral coordination change for all ligands on Eu(III). This substituent domino effect on the 1,1,1,5,5,5-hexafluoropentane-1,4-dione (hfa) ligands on Eu(III) caused by the bulky naphthyl group on the binaphthyl ligand causes the apparent change of the CPL sign in the photo-excited state, although (R)-1-3/Eu and (R,R,R)-4/Eu exhibited the same circular dichroism sign in the ground state.
  • Nobuyuki Hara; Motohiro Shizuma; Takunori Harada; Yoshitane Imai
    RSC ADVANCES 10 19 11335 - 11338 2020年03月 [査読有り]
     
    Two types of planar chiral [2,2]paracyclophane-pyrene luminophores (1 and 2) with different binding positions of the fluorescent pyrene units were synthesised. (R)/(S)-1 with 1-pyrene units exhibited green intermolecular excimer circularly polarised luminescence (CPL) at 530 nm in the KBr-pellet, but exhibited no CPL signal in dilute CHCl3 solution. In contrast, (R)/(S)-2 with 2-pyrene units exhibited a blue intramolecular excimer CPL at 450 nm in CHCl3 solution. This is the first example of using the binding position of pyrene and the external environment to tune the type (inter- or intramolecular) and chiroptical sign of excimer CPL.
  • Hideaki Takano; Natsumi Shiozawa; Yoshitane Imai; Kyalo Stephen Kanyiva; Takanori Shibata
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 142 10 4714 - 4722 2020年03月 [査読有り]
     
    Chiral polycyclic aromatic hydrocarbons (PAHs) are expected to have unusual physical properties due to their chirality and expanded pi-conjugated system. Indeed, PAHs are promising compounds as chiral recognizers and organic semiconductors. Therefore, an efficient method for the synthesis of chiral PAHs is strongly desired. In contrast to helically chiral PAHs, there are only limited examples of the enantioselective synthesis of axially chiral PAHs. Herein, we report the catalytic enantioselective synthesis of benzo[b]fluoranthene-based axially chiral PAHs in excellent yields and enantioselectivities (up to >99%, >99% ee) by regioselective cleavage of the sterically hindered C-C bond of biphenylenes. The consecutive cyclizations could provide polycyclic PAHs with two chiral axes. The obtained chiral PAHs have high epsilon values (up to epsilon = 8.9 x 10(4)), quantum yields (up to Phi = 0.67), and circularly polarized luminescence (CPL) property (vertical bar g(lum)vertical bar = up to 3.5 x 10(-3)).
  • Ryo Takishima; Yuji Nishii; Tomoaki Hinoue; Yoshitane Imai; Masahiro Miura
    BEILSTEIN JOURNAL OF ORGANIC CHEMISTRY 16 325 - 336 2020年03月 [査読有り]
     
    A series of optically active bisbenzofuro[2,3-b:3',2'-e]pyridine (BBZFPy) derivatives was synthesized starting with the readily available (S)- and (R)-1,1'-bi-2-naphthols through a palladium-catalyzed multiple intramolecular C-H/C-H coupling as the key ring-closure step. The effect of terminal tert-butyl substituents on the BBZFPy skeleton was systematically investigated to uncover a unique aggregation-induced enhancement of CPL characteristics in the solid state. The crystal structures of the coupling products were also evaluated by single crystal X-ray analysis and the well-ordered intermolecular stacking arrangements appeared to be responsible for the enhanced CPL.
  • Heshuang Dai; Yukatsu Shichibu; Yoshitane Imai; Nobuyuki Hara; Katsuaki Konishi; Yue Wang; Zhiyi Song; Tamaki Nakano
    POLYMER CHEMISTRY 11 6 1134 - 1144 2020年02月 [査読有り]
     
    Polyaddition between 2,2'-dihydroxy-1,1'-binaphthyl (BINOL) and 1,4-diisocyanatobenzene (14DIB) and that between BINOL and 1,3-diisocyanatobenzene (13DIB) were conducted leading to optically active, helical polyurethanes, poly(BINOL-alt-14DIB) and poly(BINOL-alt-13DIB), respectively. In BINOL-14DIB systems, cyclic dimers were formed along with helical, linear poly(BINOL-alt-14DIB) where the content of dimers was higher at a lower ee of BINOL and the yield of higher-molar-mass, linear polymers was higher at a higher ee of BINOL in feed. (R,R)-, (R,S)-, and (S, S)-Cyclic dimers were completely resolved and separated by chiral HPLC. The (R,S)-cyclic dimer was preferred over (R,R)-and (S, S)-cyclic dimers, while in the reaction using racemic BINOL, the (R,R)-cyclic dimer was preferred over the other isomers at 25-75% ee of (R)-BINOL in feed. Poly(BINOL-alt-14DIB) is proposed to be composed of sequences with rather contiguous (R)-BINOL units as the majority component with rather sporadically incorporated (S)-units as the minor component. Helical sense excess appears to be greater than expected from the ee of BINOL units in the chain, suggesting that (S)-BINOL units sporadically incorporated in a rather contiguous (R)-BINOL unit sequence become a part of the left-handed helical conformation controlled by the chiral influence of contiguous (R)-BINOL units. In addition, the chiral conformation of poly (BINOL-alt-14DIB) and BINOL-14DIB cyclic dimers appeared to be stabilized or enhanced in the solid state. The BINOL-13DIB systems produced linear dimers as major components of the dimer whose content was almost constant regardless of the ee of BINOL in feed. Poly(BINOL-alt-13DIB) is proposed to be composed of sequences with rather randomly distributed (R)- and (S)-BINOL units and may be characterized by sharp, left-handed turns based on BINOL chirality forming a longer-pitched, left-handed helix.
  • Yoshitane Imai
    JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN 78 2 148 - 157 2020年02月 [査読有り]
     
    Recently, the development of optically active luminophores that can emit circularly polarized luminescence (CPL) with high functionalities, such as a high dissymmetry factor (g(CPL)) and a high quantum yield (Phi(F)), has attracted attention in the field of chiroptical organic materials. However, the design of chiral luminophores that bear CPL tuning, switching, memory, and elimination has been hampered by the fact that the relationship between the structure of the photoexcited state and the chirality of the photoexcited state of chiral luminophores is not yet fully understood.Typically, a pair of enantiomeric organic fluorophores is indispensable for the emission of opposite CPL. Unfortunately, it is not always easy to prepare both enantiomers. Hence, it is necessary to find an alternative, non-classical route for controlling the sign of CPL in chiral fluorophores without the use of a fluorophore that has opposite chirality. In this paper, we report a non-classical approach for controlling the sign, wavelength, and intensity of the CPL. We report that in binaphthyl-derived fluorophores having the same axial chirality, the CPL sign can be controlled by 1) altering the dihedral angle of the axially chiral binaphthyl units, 2) tuning the linkers between the binaphthyl and fluorescent units, 3) selecting the bonding position of the fluorescent unit, 4) taking advantage of the neighboring effect between the fluorescent units, and 5) selecting appropriate organic host matrices. These non-classical methods may be useful for the development of novel chiral organic fluorophores, particularly when one of the enantiomers is easily accessible in nature. This non-classical approach to control the sign of CPL is instrumental for the development of novel chiral fluorescent systems.
  • Yuki Mimura; Takuya Sato; Yuki Motomura; Hiroki Yoshikawa; Motohiro Shizuma; Mizuki Kitamatsu; Yoshitane Imai
    RSC ADVANCES 10 5 2575 - 2580 2020年01月 [査読有り]
     
    Chiral oligopeptide-naphthalene/Eu(III) hybridized luminophores emit strong circularly polarised solution-state luminescence (CPL) from Eu(III) at 592 and 614 nm (vertical bar g(CPL)vertical bar <= 2.1 x 10(-2)). Although the peptide ligands have matching absolute configurations, the CPL sign is controllable by varying the number of naphthalene units and peptide/Eu(iii) coordination ratio.
  • Taniguchi, Ayano; Hara, Nobuyuki; Shizuma, Motohiro; Tajima, Nobuo; Fujiki, Michiya; Imai, Yoshitane
    PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES 18 12 2859 - 2864 2019年12月 [査読有り]
     
    Planar-chiral Phanephos, containing the coordinatable P(III), formed P(III)/Tb(III)(hfa)(3) hybrid luminophores that successfully emitted characteristic circularly polarised luminescence (CPL) due to D-5(4) -> F-7(5) transitions in solution. On the other hand, BINAP, containing P(III)-O as axially chiral ligand, exhibited no detectable CPL with Tb(III)(hfa)(3).
  • Hara Nobuyuki; Okuda Koji; Shizuma Motohiro; Tajima Nobuo; Imai Yoshitane
    CHEMISTRYSELECT 4 35 10209 - 10213 2019年09月 [査読有り]
  • Kaji Daiki; Ikeda Shintaro; Takamura Kenya; Tajima Nobuo; Shizuma Motohiro; Mori Tadashi; Miyasaka Makoto; Imai Yoshitane
    CHEMISTRY LETTERS 48 8 874 - 876 2019年08月 [査読有り]
  • Ishioka Sumire; Hasegawa Masashi; Hara Nobuyuki; Sasaki Hiroaki; Nojima Yuki; Imai Yoshitane; Mazaki Yasuhiro
    CHEMISTRY LETTERS 48 7 640 - 643 公益社団法人 日本化学会 2019年07月 [査読有り]
     

    To elucidate the effect of π-conjugation length on chiroptical properties in circular dichroism (CD) and circularly polarized luminescence (CPL) spectra, stereogenic oligophenylenes containing biphenyl and terphenyl units linked by a planar chiral [2.2]paracyclophane were synthesized. Both compounds are highly emissive, and their chiroptical responses depend on the conjugation length. However, extended π-conjugation exhibited smaller dissymmetry factor (g-value) both in absorption and emission spectra.

  • Watanabe Kouhei; Taniguchi Ayano; Kaji Daiki; Hara Nobuyuki; Hosoya Tomomasa; Kanesaka Aoba; Harada Takunori; Nishikawa Hiroyuki; Imai Yoshitane
    TETRAHEDRON 75 21 2944 - 2948 2019年05月 [査読有り]
     
    Organic fluorescent molecules are gaining importance because of their potential applications in many devices. Optically active N,N'-bis((1R)-1-naphthylethyl)perylene-3,4,9,10-tetracarboxylic diimide [(R,R)-1-BNP and N,N'-bis((1R)-2-naphthylethyl)perylene-3,4,9,10-tetracarboxylic diimide [(R,R)-2-BNP] and their antipode, [(S,S)-1-BNP and (S.S)-2-BNP], emit aggregation-induced enhanced (AIEnh) circularly polarized luminescence (CPL) on both a solid organic polymer film (poly(methyl methacrylate)) and solid inorganic KBr pellet. An opposite chirality is essential for generating CPL of inverted sign. However, a pair of enantiomeric organic molecules may not always be easy to prepare. Interestingly, the chiral perylene fluorophores synthesized in this study can emit both positive and negative AIEnh-CPL in the solid state, depending on their position on the naphthylene groups. In addition, no CPL was observed in these compounds from their dilute solutions. (C) 2019 Elsevier Ltd. All rights reserved.
  • Nojima Yuki; Hasegawa Masashi; Hara Nobuyuki; Imai Yoshitane; Mazaki Yasuhiro
    CHEMICAL COMMUNICATIONS 55 19 2749 - 2752 2019年03月 [査読有り]
     
    A series of cyclic oligomers with Dn symmetry (n = 2-5) based on chiral (R)/(S)-binaphthyl exhibiting intensive chiroptical properties were synthesized by using a Ni(0)-catalyzed coupling reaction. The intensity and the handedness of circularly polarized luminescence (CPL) were dependent on the ring size of the cyclic oligomers, in which the 1,1'-binaphthyl moieties form s-cis (n = 2, 3) or s-trans (n = 4, 5) conformers in the excited state. The relationship between the structure and chiroptical properties is discussed with the aid of X-ray analysis and DFT calculations.
  • Kosaka Tomoyo; Iwai Satono; Fukuhara Gaku; Imai Yoshitane; Mori Tadashi
    CHEMISTRY-A EUROPEAN JOURNAL 25 8 2011 - 2018 2019年02月 [査読有り]
  • Taniguchi Ayano; Kaji Daiki; Hara Nobuyuki; Murata Ryosuke; Akiyama Shogo; Harada Takunori; Sudo Atsushi; Nishikawa Hiroyuki; Imai Yoshitane
    RSC ADVANCES 9 4 1976 - 1981 2019年 [査読有り]
     
    Solid-state organic fluorescent materials are important for the development of electroluminescent sensing devices. Herein, we report that N,N'-bis((R)-1-phenylethyl) perylene-3,4,9,10-tetracarboxylic diimide [(R,R)-BPP] and its antipode [(S,S)-BPP], which contain extended pi-electrons through planar perylenes, emit solid-state aggregation-induced-enhanced (AIEnh) circularly polarised luminescence (CPL) in inorganic (KBr) pellets and organic-polymer-film (PMMA- and myo-IPU-film) states; this CPL is difficult to observe in solution. These chiral perylene fluorophores emit AIEnh-CPL with high dissymmetry factors (g(CPL)) (up to 2.4 x 10(-3)) and high quantum yields (Phi(F), up to 0.43) in the three solid matrices.
  • Katakami Chiaki; Kamo Shogo; Torii Ayame; Hara Nobuyuki; Imai Yoshitane; Taniguchi Tohru; Monde Kenji; Okabayashi Yusuke; Hosokai Takuya; Kuramochi Kouji; Tsubaki Kazunori
    JOURNAL OF ORGANIC CHEMISTRY 83 23 14610 - 14616 2018年12月 [査読有り]
     
    Both enantiomers of axially chiral bis-(dinaphthofuran) were prepared in only two steps from 1'-hydroxy-4'-methoxy-2,2'-binaphthalenyl-1,4-dione, followed by optical resolution via high-performance liquid chromatography (HPLC) using a chiral stationary phase (CSP). The absolute configurations were determined by comparison of experimental and calculated vibrational circular dichroism (VCD) spectra. Synthetic bis(dinaphthofuran) exhibited a broad and unstructured emission derived from an intramolecular excimer in both solution and solid state. The methylene bridge brings both chromophores close to each other and induces significant changes in the photophysical behavior. Chiral bis(dinaphthofuran) displayed a bathochromic shift in emission, as compared to the racemic mixture in the solid state. Furthermore, the compounds showed high circularly polarized luminescence (CPL) with a dissymmetry factor (g(lum)) of 10(-3) at 405 nm upon excitation at 265 nm in a methanol solution. This compound serves as a model for the design and synthesis of organic materials having CPL activity.
  • Mimura Yuki; Kitamura Sayaka; Shizuma Motohiro; Kitamatsu Mizuki; Imai Yoshitane
    ORGANIC & BIOMOLECULAR CHEMISTRY 16 37 8273 - 8279 2018年10月 [査読有り]
     

    We found that chiral oligopeptides bearing two-pendant pyrenyl units exhibited circularly polarised luminescence (CPL) originating from intramolecular excimers in various solvents, and the sign of their CPL signals depended on the solvent and piperidine unit in peptide chain.

  • Hara Nobuyuki; Tajima Nobuo; Kuroda Reiko; Imai Yoshitane
    JOURNAL OF OLEO SCIENCE 67 10 1247 - 1252 2018年10月 [査読有り]
  • Hara Nobuyuki; Yanai Masaki; Kaji Daiki; Shizuma Motohiro; Tajima Nobuo; Fujiki Michiya; Imai Yoshitane
    CHEMISTRYSELECT 3 35 9970 - 9973 2018年09月 [査読有り]
  • Wang Yue; Wang Rong; Imai Yoshitane; Hara Nobuyuki; Wan Xinhua; Nakano Tamaki
    NEW JOURNAL OF CHEMISTRY 42 18 14713 - 14716 2018年09月 [査読有り]
  • Hara Nobuyuki; Okazaki Mamoru; Kitatobe Takumi; Tajima Nobuo; Shizuma Motohiro; Sudo Atsushi; Fujihara Hisashi; Fujiki Michiya; Imai Yoshitane
    CHEMISTRY LETTERS 47 9 1200 - 1202 2018年09月 [査読有り]
  • Sato Takuya; Hara Nobuyuki; Yoshida Keishiro; Tajima Nobuo; Tsubaki Kazunori; Imai Yoshitane
    TETRAHEDRON 74 34 4471 - 4475 2018年08月 [査読有り]
     
    Extending the pi-conjugation of chiral rotatable oligonaphthyl derivatives results in longer circularly polarised luminescence (CPL) wavelengths and increased unpolarised-photoluminescence (PL) quantum yields. The CPL was observed to shift to a significantly longer wavelength and the PL quantum yield was greatly improved when the number of naphthyl units was extended from two (dimer) to four (tetramer). On the other hand, the wavelength and quantum yield increased less in moving from the tetramer to the octamer in solution and solid films. (C) 2018 Elsevier Ltd. All rights reserved.
  • Takuya Sato; Nobuyuki Hara; Nobuo Tajima; Atsushi Sudo; Michiya Fujiki; Yoshitane Imai
    Tetrahedron Letters 59 17 1619 - 1622 2018年04月 [査読有り]
     
    Although chiral 1,1′-binaphthalene-2,2′-diyl-O,O-bis(N,N-dimethylthiocarbamate) (1) revealed no circularly polarized luminescence (CPL) signals, Newman–Kwart rearrangement of O-thiocarbamate groups at 1 yielded clear CPL signals from 1,1′-binaphthalene-2,2′-diyl-S,S-bis(N,N-dimethylthiocarbamate) (2), which acts as a CPL-gen molecule.
  • Risa Watanabe; Nobuyuki Hara; Yoshitane Imai; Masashi Hasegawa; Sumire Ishioka; Yasuhiro Mazaki; Ken-Ichi Sugiura
    ChemistrySelect 3 13 3576 - 3581 2018年04月 [査読有り]
     
    Motivated by the chiral supramolecular structures of chlorophylls in photosynthesis proteins, i. e., special pairs present in purple photosynthetic bacteria, photosystems-I, and -II, a chiral porphyrin dimer was designed, synthesized, and resolved to give optically pure forms. Synthesis of the dimer was achieved by using 5,10-diarylporphyrin as the starting material. The stereochemistry of the dimer was speculated by comparing experimentally and theoretically obtained circular dichroism spectra. Clear circularly polarized luminescence spectra were obtained at 636 nm with dimensionless Kuhn's anisotropy value of ∼2.0 × 10−3.
  • Shoma Nakanishi; Nobuyuki Hara; Natsuki Kuroda; Nobuo Tajima; Michiya Fujiki; Yoshitane Imai
    Organic and Biomolecular Chemistry 16 7 1093 - 1100 2018年 [査読有り]
     
    A C2-symmeric binaphthyl framework bearing phenanthrene as the emitter exhibited circularly polarised luminescence (CPL) in dilute solutions. The CPL and circular dichroism signs of the luminophores were altered by solvents (chloroform, methanol, acetonitrile, and dimethylformamide). DFT and TD-DFT calculations indicated that the dihedral angle between the phenanthrene and naphthyl rings was responsible for the apparent sign inversion. The role of solvent molecules in the ground and photoexcited states was discussed based on Hansen solubility parameters (δ, δd, δp and δh).
  • Nobuyuki Hara; Daiki Kaji; Koji Okuda; Motohiro Shizuma; Nobuo Tajima; Yoshitane Imai
    Chemistry Letters 47 7 894 - 896 2018年 [査読有り]
     
    The introduction of aromatic substituents onto the binaphth-yl backbone of axially chiral binaphthyl organic fluorophores shifts their circularly polarized luminescence (CPL) wavelengths to higher values and may induce CPL sign inversion. Herein, we succeeded in increasing the CPL wavelength without inverting the CPL sign by introducing an alkenyl group onto the binaphthyl backbone.
  • Takumi Kitatobe; Yuki Mimura; Shintaro Tsujimoto; Nobuo Tajima; Michiya Fujiki; Yoshitane Imai
    TETRAHEDRON 73 49 6856 - 6862 2017年12月 [査読有り]
     
    Chiral, ionic C-2-symmetric binaphthyl fluorophores with amphipathic "property can emit circularly polarized luminescence (CPL) in the near-UV region when dissolved in either water or methanol. Despite the same axial chirality (R or S) of the binaphthyl units, the open- and closed-style fluorophores induced sign inversion of CPL and circular dichroism (CD) signals in water. The dihedral angle of the binaphthyl C-2-axis appears to determine the signs of CPL and CD signals even in water. (C) 2017 Elsevier Ltd. All rights reserved.
  • Nobuyuki Hara; Mamoru Okazaki; Motohiro Shizuma; Shinsuke Marumoto; Nobuo Tajima; Michiya Fujiki; Yoshitane Imai
    CHEMISTRYSELECT 2 32 10317 - 10322 2017年11月 [査読有り]
     
    Chiroptical signs in circularly polarised luminescence (CPL) of Eu(III) luminophores coordinated to C-2-symmetric binaphthyl ring carrying carboxylic acids, (R)-1 (and (S)-1)) and (R)-2 (and (S)-2)) were inverted by inserting two oxymethylene spacers between the ring and the acids. The subtle difference in reorganization between (R)-1 and (R)-2 causes the apparent CPL sign-swapping characteristics. We assume that (R)-2 is more likely to undergo this reorganization rather than (R)-1 because of the highly flexible spacer and vice versa. The subtle difference in the rotational freedom of the ligands with and without the two spacers causes the opposite CPL signs although (R)-1/Eu and (R)-2/Eu had the same CD sign in the ground state. This was proven by experimental and theoretical data.
  • Nobuyuki Hara; Mamoru Okazaki; Motohiro Shizuma; Shinsuke Marumoto; Nobuo Tajima; Michiya Fujiki; Yoshitane Imai
    CHEMISTRYSELECT 2 32 10316 - 10316 2017年11月 [査読有り]
  • Yuki Mimura; Sayaka Kitamura; Motohiro Shizuma; Mizuki Kitamatsu; Michiya Fujiki; Yoshitane Imai
    CHEMISTRYSELECT 2 26 7759 - 7764 2017年09月 [査読有り]
     
    The photoexcited and ground state chiralities of enantiopure oligopeptides bearing two pyrenyl groups (DD-2/LL-2: four methylene spacer between two pyrenyl groups and DD-1/LL-1: no methylene spacer thereof) in eight common organic solvents (CHCl3, CH2Cl2, MeOH, CH3CN, DMF, NMP, DMAc, and acetone) were investigated by means of circularly polarized luminescence (CPL) and circular dichroism (CD) spectroscopies. It was found that chiroptical signs of pyrene-origin CPL and CD signals largely depend on the nature of solvents and are susceptible to the methylene spacer. Actually, the excimer-origin CPL signs at 450-510 nm of DD-1/LL-1 in DMF were (-)/(+), respectively, while those in other solvents were oppositely (+)/(-), respectively. On the other hand, in DD-2/LL-2, the excimer-origin CPL signs were (-)/(+) in CH2Cl2 (and CHCl3), respectively, and (+)/(-) in MeOH/DMF/NMP/DMAc, respectively. The solvent dependent and the methylene spacer dependent CD sign inversion of DD-1/LL-1 and DD-2/LL-2 were also found. These results led to conclude that the solvent molecule and the methylene spacer collaboratively affect both the ground state chirality and the photoexcited chirality.
  • Mizuki Kitamatsu; Michiya Fujiki; Yoshitane Imai
    CHEMISTRYSELECT 2 26 7758 - 7758 2017年09月 [査読有り]
  • Suguru Ito; Kengo Ikeda; Shoma Nakanishi; Yoshitane Imai; Masatoshi Asami
    CHEMICAL COMMUNICATIONS 53 47 6323 - 6326 2017年06月 [査読有り]
     
    Herein, an unprecedented switching of circularly polarized luminescence (CPL) is described for chiral 4,6-bis(1-(pyren-1-ylamino) propyl) dibenzo[b,d] furan (1). The CPL band of chiral diamine 1, which contains two pyrene rings, can be switched between the monomer and excimer emission regions under concomitant inversion of the handedness, simply by changing the concentration of the fluorophore. In contrast, the maximum photoluminescence (PL) intensity is always observed in the monomer region, regardless of the concentration. The reversal of the intensity ratio of monomer and excimer emission between PL and CPL was attributed to a stronger CPL (broken vertical bar g(em)broken vertical bar = similar to 3-4 x 10(-3)) contribution from the minor excimer component, which should exhibit an efficient chiral environment around the dimeric pyrenes.
  • Yuki Mimura; Tomoki Nishikawa; Ryo Fuchino; Shiho Nakai; Nobuo Tajima; Mizuki Kitamatsu; Michiya Fujiki; Yoshitane Imai
    ORGANIC & BIOMOLECULAR CHEMISTRY 15 21 4548 - 4553 2017年06月 [査読有り]
     
    Multiple pyrenes as pendants of enantioimpure di-/tripeptides (abbreviated as N-LD-C, N-DL-C, N-LLD-C and N-DDL-C) showed pyrene-origin CPL and CD signals, which were associated with conflicting CPL-/CD-signs, compared to the corresponding enantiopure di-/tri-peptides.
  • Yuki Kono; Nobuyuki Hara; Motohiro Shizuma; Michiya Fujiki; Yoshitane Imai
    DALTON TRANSACTIONS 46 16 5170 - 5174 2017年04月 [査読有り]
     
    Complexes of Eu(III)(hfa)(3) with a C-2-symmetric planar P(III) ligand exhibited intense circularly polarised luminescence (CPL) due to D-5(0) -> F-7(1) and D-5(0) -> F-7(2) transitions, with the signs and shapes of CPL signals depending on the choice of solvent (acetone or chloroform).
  • Akihiro Sako; Koji Okuda; Nobuo Tajima; Reiko Kuroda; Yoshitane Imai
    TETRAHEDRON 73 15 2068 - 2073 2017年04月 [査読有り]
     
    Three novel naphthoquinone-based heterocyclic pigments, 2-methyl-3-[(1-methyl-1H-imidazol-2-yl) thio-1,4-naphthalenedione, (4-methyl-4H-1,2,4-triazol-3-yl)thio-1,4-naphthalenedione, and (1-methyl-1H-tetrazol-5-yl)thio]-1,4-naphthalenedione, are synthesized, and their optical properties in both solution and solid states are investigated. Depending on the heteroarylthio ring in the pigment, variation in optical properties is observed, e.g. characteristic colours for each pigment in the solution and solid states. The achiral pigment containing the 1-methyl-1H-tetrazol-5-yl ring exhibits a chiral space group and a CD signal in the solid state. (C) 2017 Elsevier Ltd. All rights reserved.
  • Masataka Toyoda; Yoshitane Imai; Tadashi Mori
    JOURNAL OF PHYSICAL CHEMISTRY LETTERS 8 1 42 - 48 2017年01月 [査読有り]
     
    Chiral boron dipyrromethenes (BPs) enjoy high fluorescence efficiency at visible to near-IR wavelength regions with a reasonable range of dissymmetry factors. Here, we demonstrate that the (quasi)propeller chirality, similarly to hexagonal propeller in hexaarylbenzene, can be effectively induced in heptaarylated BP. In addition, supramolecular dimer was formed at low temperatures in nonpolar solvent, which exhibits strong bisignate Cotton effects at BP transitions (the couplet amplitude A = 193 M(-1)cm(-1)) in the circular dichroism (CD). Due to the bulky substituents on the propeller blades, but with void space around boron atoms, BP chromophores in the dimer are aligned in a head-to-tail manner with a small torsion (phi approximate to 15 degrees), to avoid fluorescence quenching usually observed in H-type dimer of BPs exhibiting strong circularly polarized luminescence (CPL) signals (g(lum) = 2.0 x 10(-3) Phi(lum)=0.45). Such supramolecular dimer formation would be viewed as an alternative approach for designing and developing novel chiroptical materials.
  • Mamoru Okazaki; Takaya Mizusawa; Kazuki Nakabayashi; Mao Yamashita; Nobuo Tajima; Takunori Harada; Michiya Fujiki; Yoshitane Imai
    JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY 331 115 - 119 2016年12月 [査読有り]
     
    For the selective emission of positive- and negative-sign circularly polarized luminescence (CPL), two chiral organic luminophores with opposing chirality are generally needed. In this study, the solution state CPL sign of an axially chiral binaphthylacetic acid organicluminophore was successfully controlled by changing the solvent from chloroform (or methanol) to dimethylformamide (or acetonitrile). (C) 2016 Elsevier B.V. All rights reserved.
  • Takuya Sato; Nobuo Tajima; Hiroki Ueno; Takunori Harada; Michiya Fujiki; Yoshitane Imai
    TETRAHEDRON 72 44 7032 - 7038 2016年11月 [査読有り]
     
    C-2-symmetric binaphthol derivatives bearing two bulky C-3-symmetric triphenylsilyl side groups, open-style 3,3'-bis(triphenylsilyl)-1,1'-bi-2-naphthol and closed-style 3,3'-bis(triphenylsilyl)-1,1'-binaphthyl-2,2'-diyl hydrogenphosphate, emit circularly polarized luminescence (CPL) in the near-UV region when dissolved in chloroform and embedded into a poly(methyl methacrylate) film and KBr crystal. Despite the same axial chirality (S or R) of the binaphthol frameworks, the C-3-symmetric triphenylsilyl side groups induced a sign inversion in the CPL and circular dichroism (CD) signals. The possibility of rotation of the C-2-axis by the bulky groups determines the sign inversion of CPL and CD signals. (C) 2016 Elsevier Ltd. All rights reserved.
  • Takaya Mizusawa; Takuya Sato; Yoko Kitayama; Nobuo Tajima; Michiya Fujiki; Yoshitane Imai
    CHEMISTRYSELECT 1 13 3398 - 3404 2016年08月 [査読有り]
     
    Chiral organic fluorophores have recently received growing interest in the field of chiral photoluminescence. We examined chiral binaphthyl organic fluorophores bearing phenyl substituents, observing that they exhibited fluorescence properties in solution. The sign of circularly polarizsed luminescence (CPL) of binaphthyl fluorophores was controlled by changing the solvent from the weakly polar chloroform to the highly polar dimethylformamide or methanol. Moreover, the CPL behaviour was tailored by introducing phenyl substituents into the binaphthyl unit and by replacing hydroxyl moieties with ethoxy groups.
  • Hirotaka Akiyama; Akihiro Sako; Nobuo Tajima; Motohiro Shizuma; Reiko Kuroda; Yoshitane Imai
    TETRAHEDRON 72 17 2109 - 2115 2016年04月 [査読有り]
     
    The naphthoquinone pigment 2-methyl-3-(4- or 2-methylphenylthio)-1,4-naphthalenedione exhibits characteristic optical properties in both the solution and solid states. In the solid state, the position of the methyl (Me) group in the pigment imparts a range of characteristic colours. In the solution state, the 2-Me-substituted pigment exhibits solvatochromism, and this solvatochromic character is the opposite of that exhibited by the 2-OH-substituted pigment. (C) 2016 Elsevier Ltd. All rights reserved.
  • Tomoki Nishikawa; Sayaka Kitamura; Mizuki Kitamatsu; Michiya Fujiki; Yoshitane Imai
    CHEMISTRYSELECT 1 4 831 - 835 2016年04月 [査読有り]
     
    We prepared 16 novel chiral peptide-pyrene organic luminophores with different distances between the fluorescent pyrene groups and investigated their properties in CHCl3 at room temperature. The peptide-pyrene organic luminophores bearing two pyrene groups emit strong excimer circularly polarized luminescence (CPL) in the solution state. Two pendant pyrenyl groups in a series of chiral oligopeptides clearly revealed excimer CPL in chloroform at 480-490 nm (vertical bar g(em)vertical bar approximate to (2-8) x 10(-3)). When the distance between the two pyrenes increased, the sign of the CPL signals was inverted twice, while the sign of the corresponding circular dichroism (CD) signals was retained, (vertical bar g(CD)vertical bar approximate to (3-8) x 10(-5)).
  • Shoma Nakanishi; Kazuki Nakabayashi; Takaya Mizusawa; Nozomu Suzuki; Sibo Guo; Michiya Fujiki; Yoshitane Imai
    RSC ADVANCES 6 101 99172 - 99176 2016年 [査読有り]
     
    A C-2-symmetric binaphthyl-based luminophore connected to two luminescent pyrene pendants was designed to express cryptochirality, as demonstrated by the ultraweak circular dichroism signals observed in their ground state. The observed results were due to the unrestricted rotational freedom of the flexible ester wires between the binaphthyl and pyrene moieties in the absence of light. Finally, the C-2-symmetric luminophore revealed photoexcited chirality, as confirmed by intense circularly polarised luminescence.
  • Yuki Kono; Kazuki Nakabayashi; Sayaka Kitamura; Motohiro Shizuma; Michiya Fujiki; Yoshitane Imai
    RSC ADVANCES 6 46 40219 - 40224 2016年 [査読有り]
     
    The coordination of Eu(III) (from Eu(III)(hfa)(3)) by chiral P(III) (from BINAP) led to circularly polarised luminescence in dilute solutions on the order of vertical bar g(em)vertical bar approximate to 10(-2) at D-5(0) -> F-7(1) and vertical bar g(em)vertical bar approximate to 10(-3) at D-5(0) -> F-7(2) transitions regardless of the coordinating ability of the solvent (i.e., in non-coordinating ethanol-free chloroform and coordinating acetone).
  • Kazuki Nakabayashi; Sayaka Kitamura; Nozomu Suzuki; Sibo Guo; Michiya Fujiki; Yoshitane Imai
    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY 1 64 - 69 2016年01月 [査読有り]
     
    The circularly polarised luminescence and circular dichroism signs of the blue circularly polarised luminescence generated by two photoexcited pyrenes as puppets are controlled by the wire structure of the C-2-symmetric binaphthyl as puppeteer. The experimental results, though at variance with theoretical simulation, offer a rational design in the photoexcited and ground state chiralities of luminophores.
  • Kamrul Hassan; Ken-ichi Yamashita; Kazunori Hirabayashi; Toshio Shimizu; Kazuki Nakabayashi; Yoshitane Imai; Takashi Matsumoto; Akihito Yamano; Ken-ichi Sugiura
    CHEMISTRY LETTERS 44 11 1607 - 1609 2015年11月 [査読有り]
     
    Axially chiral biaryls based on pyrene, 1,1'-bipyrene-2,2'-diol derivatives 2, were designed and synthesized from 2-hydroxypyrene. Simple optical resolution was carried out and the absolute configuration was determined by diffraction study. Title compounds 2 and corresponding menthylcarbonate 4 showed clear circularly polarized luminescence (CPL) spectra. The degree of dimensionless Kuhn's anisotropy in the photoexcited state (vertical bar g(em)vertical bar) of 2 and 4 were ca. 3.6 x 10(-4) and ca. 1.2 x 10(-3), respectively. Noteworthy properties were as follows: 1) high fluorescent quantum yields of 2 and 4, 0.57 and 0.80, respectively, in marked contrast to that of BINOL, 0.04 and 2) bathochromic shifts of lambda(CPL).
  • Yuki Kono; Kazuki Nakabayashi; Sayaka Kitamura; Reiko Kuroda; Michiya Fujiki; Yoshitane Imai
    TETRAHEDRON 71 23 3985 - 3989 2015年06月 [査読有り]
     
    Chiral organic compounds in the photoexcited state are potential chiral luminophores. Photoluminescence properties of these compounds can be measured using circularly polarised luminescence (CPL) spectroscopy. Axially chiral binaphthyl BINAP in CHCI3 solution or the KBr-dispersed state exhibits no significant CPL signal. Herein, we report the first CPL spectrum of BINAP by doping into a poly(methyl methacrylate) (PMMA) organic polymeric matrix. For comparison, CPL data of BINAPO, a structural analogue of BINAP, were collected. Contrarily to BINAP, BINAPO showed a clear CPL signal in all three states. (C) 2015 Elsevier Ltd. All rights reserved.
  • Naoya Taniguchi; Kazuki Nakabayashi; Takunori Harada; Nobuo Tajima; Motohiro Shizuma; Michiya Fujiki; Yoshitane Imai
    CHEMISTRY LETTERS 44 5 598 - 600 2015年05月 [査読有り]
     
    Unlike in the solution state, the first circularly polarized luminescence (CPL) property of the axially chiral binaphthyl fluorophore bearing two fluorescent terthiophene units was successfully observed by chirality transfer from axially chiral binaphthyl to the terthiophenes, followed by amplified CPL signals in the solid state.
  • Tomoyuki Amako; Kazuki Nakabayashi; Atsushi Sudo; Michiya Fujiki; Yoshitane Imai
    ORGANIC & BIOMOLECULAR CHEMISTRY 13 10 2913 - 2917 2015年03月 [査読有り]
     
    We investigated the ground- and photoexcited-state chiralities of two chiral fluorophores with a rigid framework embedded in two achiral polyurethanes as the solid matrices. As the fluorophores, we used two pairs of atropisomeric binaphthyl derivatives, (R)-(-)-1,1'-binaphthyl-2,2'-diyl hydrogen phosphate [(R)-1a] and (R)-(-)-(3,5-dioxa-4-phosphacyclohepta-[2,1-a:3,4-a']dinaphthalen-4-yl)-dimethylamine [(R)-1b], and for comparison, their optical antipodes (S)-1a and (S)-1b. As the solid matrices, we used two soluble achiral polyurethanes (2a and 2b) derived from the naturally occurring myo-inositol as the building block, because these polymers had a high glass transition temperature of similar to 150 degrees C. The chiral fluorophores in the polyurethanes emitted circularly polarised luminescence with a high circular anisotropy of similar to 0.6-1.5 x 10(-3). Regardless of the matrix, (R)- and (S)-1a had nearly mirror-image chiroptical properties in the ground and photoexcited states, as did (R) -and (S)-1b.
  • Yoshitane Imai
    J. Jpn. Soc. Colour Mater. 88 11 383 - 387 一般社団法人 色材協会 2015年 [招待有り]
     
    発光には，左回転・右回転二種類の円偏光発光（CPL）が存在し，一般の発光は，左回転・右回転二種類のCPLが混在している。CPLは，現在の液晶に多用される直線偏光とは異なる光学特性を有し，各種分野での応用・利用が期待されている。本稿では，軸不斉を有する光学活性ビナフチル化合物を発光性材料として用い，当研究室で見いだした特徴的なCPL特性，ならびにその非古典的CPL特性制御について紹介する。
  • Tomoki Nishikawa; Nobuo Tajima; Mizuki Kitamatsu; Michiya Fujiki; Yoshitane Imai
    ORGANIC & BIOMOLECULAR CHEMISTRY 13 47 11426 - 11431 2015年 [査読有り]
     
    Among L- and D-oligopeptides with multiple pyrenes as pendants, the dipeptides with two and three pyrenes showed blue-coloured circularly polarised luminescence as high as vertical bar g(em)vertical bar approximate to (0.86-1.1) x 10(-2) at around 450 nm, reflecting from exciton couplets of twisted pyrenes.
  • Takashi Wakabayashi; Sayaka Kitamura; Hideyuki Tabata; Reiko Kuroda; Yoshitane Imai
    CRYSTENGCOMM 17 16 3064 - 3069 2015年 [査読有り]
     
    A supramolecular benzothiophene heterocyclic host complex was successfully prepared by combining benzo[b] thiophene-3-acetic acid and chiral (1R, 2S)-2-amino-1,2-diphenylethanol. Four types of n-alkyl alcohols could be stored as guests in one-dimensional channel-like cavities composed of 2(1)-helical columnar network structures. The release temperatures of the stored guest alcohols could be multiply tuned according to the type of the benzothiophene unit in the complex.
  • Sayaka Kitamura; Kazuki Nakabayashi; Takashi Wakabayashi; Nobuo Tajima; Michiya Fujiki; Yoshitane Imai
    RSC ADVANCES 5 83 67449 - 67453 2015年 [査読有り]
     
    Circularly polarized luminescent properties of C2-symmetrical binaphthyl molecular systems bearing two achiral anthracenes as luminophores were tuned by solely exploiting photoexcited-state chirality transfer from the binaphthyl to anthracenes when open-or closed-type binaphthyl structure as non-luminophore were chosen.
  • Tomoyuki Amako; Kazuki Nakabayashi; Nozomu Suzuki; Sibo Guo; Nor Azura Abdul Rahim; Takunori Harada; Michiya Fujiki; Yoshitane Imai
    CHEMICAL COMMUNICATIONS 51 39 8237 - 8240 2015年 [査読有り]
     
    2,2-Dimethyl-1,3-dioxolane connected to two pyrene moieties through flexible wires in chloroform exhibited cryptochirality in the ground state, as proven by the lack of detectable circular dichroism signals. This cryptochirality was deciphered in the photo-excited state by circularly polarised luminescence signals.
  • Yoko Kitayama; Kazuki Nakabayashi; Takashi Wakabayashi; Nobuo Tajima; Michiya Fujiki; Yoshitane Imai
    RSC ADVANCES 5 1 410 - 415 2015年 [査読有り]
     
    The signs of circularly polarised luminescence and circular dichroism of chiral biaryl fluorophores in the CHCl3-dissolved state (solution state) and the PMMA-film-dispersed state (solid state) were successfully controlled by modifying the internal axial chirality and the axial bonding position of the biaryl units.
  • Kazuki Nakabayashi; Tomoyuki Amako; Nobuo Tajima; Michiya Fujiki; Yoshitane Imai
    CHEMICAL COMMUNICATIONS 50 87 13228 - 13230 2014年11月 [査読有り]
     
    The fluorescent modes and signs of the circularly polarized luminescence of an axially chiral binaphthyl-pyrene organic fluorophore were successfully controlled by changing from a fluidic chloroform solution to a glassy poly(methyl methactylate) solid film.
  • Kouhei Ookuma; Tomoyuki Amako; Hiyori Aoyama; Tomohiro Sato; Nobuo Tajima; Reiko Kuroda; Yoshitane Imai
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 592 1 209 - 217 2014年03月 [査読有り]
     
    Charge-transfer (CT) complexes were prepared using racemic (rac)-10,10 '-dihydroxy-9,9 '-biphenanthryl, which has a large and highly pi-conjugated phenanthrene ring, as the electron donor and p-benzoquinone as the electron acceptor. This CT system showed a polymorphism.
  • Taiga Tatsumi; Yoshitane Imai; Kakuhiro Kawaguchi; Naoko Miyano; Isao Ikeda
    JOURNAL OF OLEO SCIENCE 63 2 137 - 140 2014年02月 [査読有り]
     
    We evaluated the antimicrobial activities of a cationic Gemini surfactant, trans-1,4-bis [2-(alkanoyloxy)ethyldimethylammonio]-2-butene dichloride [II-m-2(t-butene)] and its derivatives against Gram-positive and Gram-negative microorganisms. The II-m-2(t-butene) compound was previously shown to have good surface activity and biodegradability. A dodecanoyloxy derivative (m = 12) of II-m-2(t-butene) showed excellent antimicrobial activity against Gram-positive Streptococcus aureus [minimum inhibitory concentration (MIC): 7.8 mu g/mL] and Gram-negative Escherichia coli (MIC: 31.2 mu g/mL).
  • Masato Hirayama; Yuhei Kobayashi; Yuki Tanaka; Tomohiro Sato; Takunori Harada; Nobuo Tajima; Reiko Kuroda; Michiya Fujiki; Yoshitane Imai
    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY 4 719 - 724 2014年02月 [査読有り]
     
    Unlike in the solution state, the circularly polarized luminescence (CPL) of the chiral oxazoline compound 4-(4-isopropyl-4,5-dihydrooxazol-2-yl)benzonitrile, having one oxazoline unit, was observed in the solid state. On the other hand, although the CPL of the chiral oxazoline compound 1,4-bis(4-isopropyl-4,5-dihydrooxazol-2-yl)benzene, having two oxazoline units, was not observed, its circular dichroism (CD) property changed significantly according to the state (i.e., solution or solid state).
  • Tomoyuki Amako; Kazuki Nakabayashi; Tadashi Mori; Yoshihisa Inoue; Michiya Fujiki; Yoshitane Imai
    CHEMICAL COMMUNICATIONS 50 85 12836 - 12839 2014年 [査読有り]
     
    Tethering four 1- versus 2-naphthyls to the same chiral scaffold derived from tartaric acid led to oppositely signed circularly polarized luminescence (CPL) and circular dichroism (CD) in solution, which not only reveals the decisive role of the spatial arrangement of chromophores/fluorophores in determining the chiroptical behaviors but also provides us with a versatile tool for switching the signs of CPL and CD without using the antipodal scaffold.
  • Takunori Harada; Naoki Kajiyama; Kei Ishizaka; Reona Toyofuku; Katsuki Izumi; Kazuo Umemura; Yoshitane Imai; Naoya Taniguchi; Kenji Mishima
    CHEMICAL COMMUNICATIONS 50 76 11169 - 11172 2014年 [査読有り]
     
    The chiroptical properties of an anionic meso-tetrakis(4-sulfonatophenyl) porphyrin (TPPS) complexed with cationic surfactants were enhanced by interaction with silver nanoparticles (AgNPs) in acidic solution. Improvement in chiroptical properties was revealed by circular dichroism (CD) and circularly polarized luminescence (CPL), with vertical bar g(abs)vertical bar and vertical bar g(lum)vertical bar values reaching 0.05 and 0.001 at 303 K, respectively.
  • Takashi Wakabayashi; Tomoyuki Amako; Hideyuki Tabata; Reiko Kuroda; Yoshitane Imai
    CRYSTAL GROWTH & DESIGN 14 1 32 - 37 2014年01月 [査読有り]
     
    Supramolecular 3-chlorobenzo[b]thiophene heterocyclic host complex composed of chiral (1R,2S)-2-amino-1,2-diphenylethanol was successfully prepared using 3-chlorobenzo[b]thiophene-2-carboxylic acid. Four types of guest n-alkyl alcohols could be stored in one-dimensional channel-like cavities composed of chiral 2(1)-helical columnar network structures. The release properties of the guest alcohol changed depending on the length of the alkyl chain in the alcohol.
  • Yuki Tanaka; Hideyuki Tabata; Nobuo Tajima; Reiko Kuroda; Yoshitane Imai
    CRYSTENGCOMM 16 9 1741 - 1748 2014年 [査読有り]
     
    Although fluorescent, column-like supramolecular network structures were previously obtained by using 2-naphthalenecarboxylic acid and benzylamine or fluorobenzylamine, the use of chlorobenzylamine or bromobenzylamine results in column-like or 2D-layered network supramolecular structures, indicating that crystal structures can be controlled by altering the type and position of the substituent on the benzylamine component.
  • Yoko Kitayama; Tomoyuki Amako; Nozomu Suzuki; Michiya Fujiki; Yoshitane Imai
    ORGANIC & BIOMOLECULAR CHEMISTRY 12 25 4342 - 4346 2014年 [査読有り]
     
    Circularly polarised luminescence (CPL) and photoluminescence (PL) properties of pi-conjugated (R)- and (S)-2,2'-diphenyl-4-biphenanthrol (VAPOL) exhibited an efficient CPL (similar to 1.3 x 10(-3)) with a quantum yield (Phi(F)) of 0.20 at 376 nm. By comparison, (R)- and (S)-3,3-diphenyl-2,2-bi-1-naphthol (VANOL) exhibited no CPL or PL.
  • Hirotaka Akiyama; Takafumi Inoue; Nobuo Tajima; Reiko Kuroda; Yoshitane Imai
    ORGANIC & BIOMOLECULAR CHEMISTRY 12 40 7965 - 7970 2014年 [査読有り]
     
    Naphthoquinone pigments 2-methyl-3-(4- or 2-hydroxyphenylthio)-1,4-naphthalenedione show characteristic optical properties in solution and in the solid state. The position of the OH group in the pigment leads to varied optical properties, including a characteristic colour, in the solid state. The pigment with a 2-OH substituent displays solvatochromism in solution, and that with a 4-OH substituent displays optical chirality in the solid state.
  • Eiki Yotsumoto; Takafumi Inoue; Takashi Wakabayashi; Tomoyuki Amako; Nobuo Tajima; Reiko Kuroda; Yoshitane Imai
    JOURNAL OF MOLECULAR STRUCTURE 1056 189 - 193 2014年01月 [査読有り]
     
    The novel compounds 2-methyl-3-(2-chlorophenylthio)-1,4-naphthalenedione and 2-methyl-3-(3-chlorophenylthio)-1,4-naphthalenedione were successfully synthesized. Although the color of three types of 2-methyl-3-[2-chloro (or 3-chloro or 4-chloro)phenylthio]-1,4-naphthalenedione in solution are similar, the solid-state color of these compounds could be easily changed according to the position of the chloro group in the phenylthio ring. (C) 2013 Elsevier B.V. All rights reserved.
  • Noriaki Iwase; Yuta Shigeno; Takashi Wakabayashi; Tomohiro Sato; Nobuo Tajima; Reiko Kuroda; Yoshitane Imai
    CRYSTENGCOMM 16 2 159 - 163 2014年 [査読有り]
     
    Using p-benzoquinone and its derivatives as electron acceptors, charge-transfer (CT) complexes with a large bisphenol A derivative, i.e., alpha,alpha'-bis(4-hydroxyphenyl)-1,4-diisopropylbenzene, were successfully formed. The complexation behavior and color of the CT complexes varied with the crystallization method and p-benzoquinone derivative. This CT system may be applicable for sensitive and visible recovery and indication of large bisphenol A derivatives.
  • Naoya Taniguchi; Ryutaro Shimomaki; Tomoyuki Amako; Tomohiro Sato; Hayato Tokutome; Nobuo Tajima; Reiko Kuroda; Michiya Fujiki; Yoshitane Imai
    ASIAN JOURNAL OF ORGANIC CHEMISTRY 2 8 681 - 687 2013年08月 [査読有り]
     
    A spontaneously resolved chiral fluorescent system was prepared from achiral 4-(2-arylethynyl) benzoic acid and racemic (rac)-1-phenylethylamine. Although functional chiral organic materials are usually prepared from chiral molecules, the chiral organic fluorophore described herein is successfully generated from achiral and racemic molecules to form a system that emits circularly polarized luminescence (CPL) in the solid state.
  • Takaya Kimoto; Tomoyuki Amako; Nobuo Tajima; Reiko Kuroda; Michiya Fujiki; Yoshitane Imai
    ASIAN JOURNAL OF ORGANIC CHEMISTRY 2 5 404 - 410 2013年05月 [査読有り]
     
    The signs of solid-state circularly polarized luminescence (CPL) of axially chiral binaphthyl organic fluorophores were successfully controlled by changing the environment of their solid-state matrices from a poly(methyl methacrylate) (PMMA) film-dispersed state to a KBr pellet-dispersed state.
  • Tomoyuki Amako; Takaya Kimoto; Nobuo Tajima; Michiya Fujiki; Yoshitane Imai
    TETRAHEDRON 69 13 2753 - 2757 2013年04月 [査読有り]
     
    The circularly polarized luminescence (CPL) property of (R)-(-)-1,1'-binaphthyl-2,2'-diyl hydrogen phosphate with axial chirality has been previously reported, unfortunately, CPL from (R)-(-)-3,3'-bis(4-nitrophenyl)-1,1'-binaphthyl-2,2'-diyl hydrogen phosphate with a 4-nitorobenzene group could not be observed in this work. However, CPL from the naphthalene unit was observed for (R)-(-)-3,3'-bis[3,5-bis(trifluoromethyl)phenyl]-1,1'-binaphthyl-2,2'-diyl hydrogen phosphate with a bis(trifluoromethyl) phenyl group. Interestingly, in (R)-3,3'-bis(9-anthracenyl)-1,1'-binaphthyl-2,2'-diyl hydrogen phosphate with an anthracene group, CPL was emitted from the anthracene unit due to efficient intramolecular chiral transfer. (C) 2013 Elsevier Ltd. All rights reserved.
  • Tomoyuki Amako; Takaya Kimoto; Nobuo Tajima; Michiya Fujiki; Yoshitane Imai
    RSC ADVANCES 3 19 6939 - 6944 2013年 [査読有り]
     
    The solution-dissolved-state circular dichroism (CD) and the circularly polarized luminescence (CPL) of chiral binaphthyl fluorophores was controlled by both the axial chirality of the binaphthyl units as well as by the effect of neighboring binaphthyl units.
  • Yuhei Kobayashi; Yuki Tanaka; Tomohiro Sato; Michiya Fujiki; Reiko Kuroda; Yoshitane Imai
    CRYSTENGCOMM 15 31 6259 - 6263 2013年 [査読有り]
     
    A chiral anthracene fluorescence system was developed from achiral 2-anthracenecarboxylic acid and 1-naphthylmethylamine. Although chiral functional organic materials are usually prepared using chiral molecules, in this system, a chiral supramolecular organic fluorophore, which exhibited fluorescence in the solid state, was prepared from achiral molecular components.
  • Yuhei Kobayashi; Tomohiro Sato; Yuki Tanaka; Takunori Harada; Reiko Kuroda; Yoshitane Imai
    CRYSTENGCOMM 15 23 4624 - 4630 2013年 [査読有り]
     
    Although three types of 2-naphthalenecarboxylic acid supramolecular organic fluorophores are obtained by using benzylamine, the resulting crystal structures using fluorobenzylamine instead of benzylamine is limited, and only two types of 2-naphthalenecarboxylic acid supramolecular organic fluorophores with different optical properties are formed. In addition, the formation of these supramolecular organic fluorophores can be controlled by changing the position of the fluorine substituent or the crystallization method.
  • Tomoyuki Amako; Takunori Harada; Nozomu Suzuki; Kenji Mishima; Michiya Fujiki; Yoshitane Imai
    RSC ADVANCES 3 45 23508 - 23513 2013年 [査読有り]
     
    The chiroptical properties of two viscous chiral fluorophores, (R)-2,2'-hepthoxy-1,1'- binaphthyl [(R)-1] and its antipode [(S)- 1], dispersed in inorganic (KBr and KCl) and organic polymer ( PMMA and PS) matrices are studied in the photoexcited and ground states. Both (R)-1 and (S)-1 emit circularly polarised luminescence (CPL) with a high quantum efficiency in these solid matrices (15-58%) and in chloroform solution (14%).
  • Naoki Shiota; Yumeko Sakoda; Takafumi Kinuta; Yoshitane Imai
    JOURNAL OF INCLUSION PHENOMENA AND MACROCYCLIC CHEMISTRY 74 1-4 369 - 374 2012年12月 [査読有り]
     
    Solid-state disulfonic acid/amine fluorescent host complexes including methanol (MeOH) as guests were successfully prepared using 4,4'-biphenyldisulfonic acid and 2-naphthylethylamine as component molecules. Although the crystal structure of the obtained host complex is similar to that of the corresponding dicarboxylic acid/amine host complex, the solid-state photo-luminescence quantum yield of the disulfonic acid/amine fluorescent host complex is increased relative to those of the corresponding dicarboxylic acid/amine host complex.
  • Shintaro Hige; Naoki Shiota; Yuhei Kobayashi; Takashi Wakabayashi; Tomohiro Sato; Yoshitane Imai
    TETRAHEDRON 68 48 9999 - 10004 2012年12月 [査読有り]
     
    Three types of supramolecular benzoheterocyclic host complexes were successfully prepared using (1R,2S)-2-amino-1,2-diphenylethanol and three types of benzoheterocyclic (benzothiophene, benzofuran, and benzopyrrole) acid derivatives. The host complexes had one-dimensional (1D) channel-like cavities that were formed by the assembly of two-component 2(1)-helical columnar network structures, which included guest alcohol molecules. The release behavior of the guest molecules could be tuned by the type of heterocyclic ring in the supramolecular host complex. (C) 2012 Elsevier Ltd. All rights reserved.
  • Naoki Shiota; Yumeko Sakoda; Takafumi Kinuta; Yoshitane Imai
    Journal of Inclusion Phenomena and Macrocyclic Chemistry 74 1-4 369 - 374 2012年12月 [査読有り]
     
    Solid-state disulfonic acid/amine fluorescent host complexes including methanol (MeOH) as guests were successfully prepared using 4,4′- biphenyldisulfonic acid and 2-naphthylethylamine as component molecules. Although the crystal structure of the obtained host complex is similar to that of the corresponding dicarboxylic acid/amine host complex, the solid-state photo-luminescence quantum yield of the disulfonic acid/amine fluorescent host complex is increased relative to those of the corresponding dicarboxylic acid/amine host complex. © 2012 Springer Science+Business Media B.V.
  • Takaya Kimoto; Nobuo Tajima; Michiya Fujiki; Yoshitane Imai
    CHEMISTRY-AN ASIAN JOURNAL 7 12 2836 - 2841 2012年12月 [査読有り]
     
    The solution-dispersed-state and polymer-dispersed-state circular dichroism (CD) and circularly polarized luminescence (CPL) properties of chiral binaphthyl fluorophores could be controlled by the choice of open- or closed-type substituents on the binaphthyl units and by the axial chirality of the binaphthyls.
  • Naoki Shiota; Takafumi Kinuta; Tomohiro Sato; Takaya Kimoto; Yoshitane Imai
    LETTERS IN ORGANIC CHEMISTRY 9 8 559 - 562 2012年10月 [査読有り]
     
    We successfully prepared a novel supramolecular network complex having one-dimensional (1D) channel-like cavities by using 2-naphthylethylamine and 2,2'-bithiophene-5,5'-dicarboxylic acid. The EtOH molecules in this complex were trapped as guests in 1D channel-like cavities formed by the assembly of characteristic two-dimensional (2D) layered hydrogen- and ionic-bonded network structures.
  • Takafumi Kinuta; Nobuo Tajima; Michiya Fujiki; Mitsuo Miyazawa; Yoshitane Imai
    TETRAHEDRON 68 24 4791 - 4796 2012年06月 [査読有り]
     
    The chiroptical signs in circularly polarized luminescence (CPL) and circular dichroism (CD) spectra of chiral binaphthyl fluorophores in solution were found to be controllable by changing the dihedral angle of the binaphthyl unit regardless of the same axial chirality. (C) 2012 Elsevier Ltd. All rights reserved.
  • Noriaki Nishiguchi; Takafumi Kinuta; Tomohiro Sato; Yoko Nakano; Takunori Harada; Nobuo Tajima; Michiya Fujiki; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    CRYSTAL GROWTH & DESIGN 12 4 1859 - 1864 2012年04月 [査読有り]
     
    The solid-state circular dichroism (CD) of a 4-[2-(methylphenyl)ethynyl]benzoic acid/amine supramolecular organic fluorophore can be controlled by changing the position of the methyl substituent of the methylphenylethynyl unit on the achiral. 4-[2-(methylphenyl)ethynyl]benzoic acid component molecule, instead of changing the chirality of the chiral amine component molecule.
  • Naoki Shiota; Shintaro Hige; Takafumi Kinuta; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    JOURNAL OF MOLECULAR STRUCTURE 1014 32 - 37 2012年04月 [査読有り]
     
    Three types of supramolecular heterocyclic host complexes were successfully prepared using chiral (1R,2S)-2-amino-1,2-diphenylethanol and three basic types of heterocyclic (thiophene, furan, and pyrrole) acid derivatives. These host complexes are composed of a chiral 2(1)-helical columnar network structure. It also contains channel-like cavities formed by the assembly of these chiral 2(1)-helical columns, which include guest alcohol molecules. (C) 2012 Elsevier B.V. All rights reserved.
  • Noriaki Nishiguchi; Takafumi Kinuta; Tomohiro Sato; Yoko Nakano; Hayato Tokutome; Nobuo Tajima; Michiya Fujiki; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    CHEMISTRY-AN ASIAN JOURNAL 7 2 360 - 366 2012年02月 [査読有り]
     
    The solid-state chiral optical properties (circular dichroism and circularly polarized luminescence) of a 2-naphthalenecarboxylic acid/amine supramolecular organic fluorophore can be controlled by changing the aryl unit of the chiral 1-arylethylamine component of the molecule rather than altering the chirality of the 1-arylethylamine itself.
  • Takafumi Kinuta; Tomohiro Sato; Nobuo Tajima; Yoshio Matsubara; Mitsuo Miyazawa; Yoshitane Imai
    CRYSTENGCOMM 14 3 1016 - 1020 2012年 [査読有り]
     
    The novel pigment 3,3 '-(4,4 '-biphenyldiylbisthio)bis-2-methyl-1,4-naphthoquinone comprising two naphthoquinone units was successfully synthesized. This pigment exhibits three conformational polymorphs, all of which have different colors (light red, red, and deep red).
  • Takahiro Okuno; Yumeko Sakoda; Takafumi Kinuta; Tomohiro Sato; Hayato Tokutome; Nobuo Tajima; Yoko Nakano; Michiya Fujiki; Reiko Kuroda; Yoshitane Imai
    CRYSTENGCOMM 14 14 4819 - 4825 2012年 [査読有り]
     
    Chiral carboxylic acid/amine and sulfonic acid/amine supramolecular organic complexes composed of biphenyl units were successfully prepared using achiral biphenylcarboxylic acid (or biphenylsulfonic acid) derivatives and chiral 1-phenylethylamine as component molecules. The solid-state circular dichroism (CD) and fluorescent properties of the supramolecular complexes change significantly with the type and number of binding groups.
  • Yuhei Kobayashi; Takafumi Kinuta; Tomohiro Sato; Takunori Harada; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    CRYSTENGCOMM 14 4 1468 - 1472 2012年 [査読有り]
     
    By using achiral fluorescent 2-naphthalenecarboxylic acid with achiral benzylamine, three types of polymorphic supramolecular organic fluorophores with different optical properties are created. These include a racemic supramolecular fluorophore and chiral fluorophores. These polymorphic supramolecular fluorophores can be controlled by changing the crystallization method.
  • Noriaki Iwase; Yuhei Kobayashi; Takafumi Kinuta; Tomohiro Sato; Nobuo Tajima; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    CRYSTENGCOMM 14 24 8599 - 8605 2012年 [査読有り]
     
    Charge-transfer (CT) complexes with bisphenol A and its derivatives were successfully formed by solid co-grinding crystallization with p-benzoquinone and its derivatives as electron acceptors. The complexation behavior and color of the obtained CT complexes varied with the type of bisphenol A and p-benzoquinone derivatives that were used.
  • Takaya Kimoto; Naoki Shiota; Takafumi Kinuta; Tomohiro Sato; Nobuo Tajima; Hayato Tokutome; Reiko Kuroda; Michiya Fujiki; Yoshio Matsubara; Yoshitane Imai
    TETRAHEDRON 67 40 7775 - 7779 2011年10月 [査読有り]
     
    Solid-state chiral supramolecular thiophene fluorophore has been successfully prepared by using chiral (R)-1-(2-naphthyl)ethylamine and 5-bromothiophene-2-carboxylic acid. This chiral supramolecular thiophene fluorophore is formed by assembling chiral 2(1)-helical columnar network structures composed of (R)-1-(2-naphthyl)ethylamine and 5-bromothiophene-2-carboxylic acid. This supramolecular organic fluorophore exhibits circularly polarized luminescence (CPL) even in the solid state. (C) 2011 Elsevier Ltd. All rights reserved.
  • Takafumi Kinuta; Tomohiro Sato; Yoko Nakano; Takunori Harada; Nobuo Tajima; Michiya Fujiki; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY 220 2-3 134 - 138 2011年05月 [査読有り]
     
    It is important to first determine the solid-state chiral optical properties of basic fluorescence supramolecular building blocks that can form a network structure via intermolecular interactions. Although the circularly polarized luminescence (CPL) properties of (R)-1,1'-binaphthyl-2,2'-dicarboxylic acid with axial chirality could not be measured in either the solution or solid states, those of (R)-1,1'-binaphthyl-2,2'-diyl hydrogen phosphate with axial chirality were successfully measured in both states. The solid-state CPL originates from the intramolecular interaction of single molecule, rather than intermolecular interactions in the crystal. (C) 2011 Elsevier B.V. All rights reserved.
  • Noriaki Nishiguchi; Takafumi Kinuta; Yoko Nakano; Takunori Harada; Nobuo Tajima; Tomohiro Sato; Michiya Fujiki; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    CHEMISTRY-AN ASIAN JOURNAL 6 4 1092 - 1098 2011年04月 [査読有り]
     
    The solid-state chiral optical properties of a 4-(2-arylethynyl)-benzoic acid/amine supramolecular organic fluorophore can be controlled by changing the arylethynyl group of the achiral 4-(2-arylethynyl)-benzoic acid component molecule rather than the chirality of the amine component molecule.
  • Noriaki Nishiguchi; Tomohiro Sato; Takafumi Kinuta; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    CRYSTAL GROWTH & DESIGN 11 3 827 - 831 2011年03月 [査読有り]
     
    Supramolecular organic fluorophores composed of a one-dimensional (1D) column network structure were successfully developed using three types of 1-phenylethylamine derivatives as amine molecules and 2-naphthalenecarboxylic acid as a fluorescent acid molecule. These supramolecular organic fluorophores are formed by changing the style of the 1D columnar network structure and its packing arrangement, and their solid-state fluorescence properties are tuned according to their changes.
  • Naoki Shiota; Takahiro Okuno; Takafumi Kinuta; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    CRYSTENGCOMM 13 5 1683 - 1686 2011年 [査読有り]
     
    A solid-state fluorescence host complex was prepared by assembly of a two-dimensional (2D) layered hydrogen-and ionic-bonded network structure composed of 2-naphthylethylamine and 2,6-naphthalenedicarboxylic acid. In this complex, the MeOH guest molecules are one-dimensionally trapped in channel-like cavities formed by the characteristic 2D layered network structures. This supramolecular host complex including MeOH shows fluorescence in the solid state.
  • Tatsuya Ukegawa; Takafumi Kinuta; Tomohiro Sato; Nobuo Tajima; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    TETRAHEDRON 66 45 8756 - 8762 2010年11月 [査読有り]
     
    A colored charge-transfer (CT) host complex is formed using racemic (rac)-10,10'-dihydroxy-9,9'-biphenanthryl, which has a large and widely pi-conjugated phenanthrene ring, as the electron donor and 2,5-disubstituted-1,4-benzoquinone as the electron acceptor. This CT host complex can include aromatic molecules as guests and its color and diffuse reflectance spectra (DRS) change according to the type of guest molecules included. Characteristically, it is possible to tune the color and DRS of the inclusion CT complex by changing the type of the component 2,5-disubstituted-1,4-benzoquinone. (C) 2010 Elsevier Ltd. All rights reserved.
  • Takafumi Kinuta; Tomohiro Sato; Nobuo Tajima; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    JOURNAL OF MOLECULAR STRUCTURE 982 1-3 45 - 49 2010年10月 [査読有り]
     
    Charge-transfer complexes composed of 1,1'-bi-2-naphthol as an electron donor and viologen derivatives as electron acceptors exhibit thermochromic properties in the solid state without dramatical isomerization of the component molecules such as proton transfer. (C) 2010 Elsevier B.V. All rights reserved.
  • Takafumi Kinuta; Tomohiro Sato; Takunori Harada; Nobuo Tajima; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    JOURNAL OF MOLECULAR STRUCTURE 982 1-3 16 - 21 2010年10月 [査読有り]
     
    The achiral compound 2-methyl-3-(4-bromophenylthio)-1,4-naphthalenedione shows conformational and color polymorphism. The relationship between the conformational and color polymorphs (chirality and color) of 2-methyl-3-arylthio-1,4-naphthalenediones can change according to the type of arylthio group. (C) 2010 Elsevier B.V. All rights reserved.
  • Naoki Shiota; Takafumi Kinuta; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    TETRAHEDRON 66 30 5589 - 5593 2010年07月 [査読有り]
     
    A tunable supramolecular thiophene host system with a chiral channel-like cavity is developed using (1R,2S)-2-amino-1,2-diphenylethanol. This thiophene host system possesses a chiral helical columnar structure. The chiral cavities are formed by the self-assembly of the helical column, and guest molecules are included by varying the helical structure and packing arrangement of this column. (C) 2010 Elsevier Ltd. All rights reserved.
  • Yoshitane Imai; Kensaku Komon; Nobuo Tajima; Takafumi Kinuta; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara
    JOURNAL OF LUMINESCENCE 130 6 954 - 958 2010年06月 [査読有り]
     
    By introducing carboxyl and n-alkyl groups into a biphenyl molecule, we can increase the photoluminescence quantum yields of biphenyl derivatives in the solid state. The solid-state fluorescence maxima (lambda(em)) of 4-biphenylcarboxylic acid derivatives change according to the n-alkyl group introduced. (C) 2010 Elsevier B.V. All rights reserved.
  • Naoki Shiota; Takafumi Kinuta; Tomohiro Sato; Nobuo Tajima; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    Crystal Growth and Design 10 3 1346 - 1350 2010年03月 [査読有り]
     
    A supramolecular thiophene host system showing solid-state fluorescence has been prepared by using chiral (l R,2S)-2-amino-l,2-diphenylethanol and two basic types of thiophene acid derivatives. This host system has a chiral 2 1 -helical columnar structure and channel-like cavities formed by the self-assembly of 21-helical columns guest molecules are included in these cavities. © 2009 American Chemical Society.
  • Tatsuya Ukegawa; Takafumi Kinuta; Tomohiro Sato; Nobuo Tajima; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    CHEMISTRY LETTERS 39 3 257 - 259 2010年03月 [査読有り]
     
    A colored supramolecular charge-transfer (CT) host complex composed of racemic rac-[9,9 '-biphenanthryl]-10,10 '-diol, having a large and widely pi-conjugated phenanthrene ring, as an electron donor and 2,5-dimethyl-1,4-benzoquinone as an electron acceptor has been developed. The molecular recognition properties (guest inclusion behavior and color) of the CT complex can be tuned by using electron donor molecules with different steric bulkiness and electron-donating properties.
  • Yoshitane Imai; Naoki Shiota; Takafumi Kinuta; Takahiro Okuno; Yoko Nakano; Takunori Harada; Tomohiro Sato; Michiya Fujiki; Reiko Kuroda; Yoshio Matsubara
    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY 7 1353 - 1357 2010年03月 [査読有り]
     
    A chiral anthracenecarboxylic acid/amine supramolecular organic fluorophore composed of a 2D layered network structure was developed by combining 1-amino-2-indanol and 2-anthracenecarboxylic acid molecules. This 2D, chiral fluorophore exhibits circularly polarized luminescence (CPL) without quenching the fluorescence in the solid state.
  • Naoki Shiota; Takafumi Kinuta; Tomohiro Sato; Nobuo Tajima; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    CRYSTAL GROWTH & DESIGN 10 3 1341 - 1345 2010年03月 [査読有り]
     
    A supramolecular thiophene host system showing solid-state fluorescence has been prepared by using chiral (1R,2S)-2-amino-1,2-diphenylethinol and two basic types of thiophene acid derivatives. This host system has a chiral 2(1)-helical columnar structure and channel-like cavities formed by the self-assembly of 2(1)-helical columns; guest molecules are included in these cavities.
  • Takafumi Kinuta; Nobuo Tajima; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    JOURNAL OF MOLECULAR STRUCTURE 964 1-3 27 - 30 2010年02月 [査読有り]
     
    A novel charge-transfer (CT) host system with a 1 D column-like structure is developed. This 1D column-like structure is formed by the CT interactions between wrac-6,6'-dibromo-1,1'-bi-2-naphthol (rac-1) and 1,1'-dimethyl-4,4'-bipyridinium dichloride (MVCl(2)). n-Alkyl alcohol molecules (guest molecules) can be introduced into the CT host system by tuning of the packing of its I D CT column-like structure. The diffuse reflectance spectra (DRS) of this host system are sensitive to the type of guest molecules. (C) 2009 Elsevier B.V. All rights reserved.
  • 62. 固体蛍光を示す二成分系超分子ホスト錯体の創製
    今井喜胤
    化学工業 865 - 870 2010年 [招待有り]
  • Takafumi Kinuta; Emi Yokoyama; Tomohiro Sato; Nobuo Tajima; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    CRYSTENGCOMM 12 5 1394 - 1396 2010年 [査読有り]
     
    The achiral compound 2-(2-naphthylthio or 2-quinolinethio)-3methylcyclohexen- 1-one was found to crystallize in the chiral space group P2(1)2(1)2(1). In one crystal, only one-handedness was found. In particular, although 2-(2-naphthylthio)-3-methylcyclohexen-1-one showed conformational polymorphism, both polymorphs were chiral crystals.
  • Yoshitane Imai; Katuzo Murata; Yoko Nakano; Takunori Harada; Takafumi Kinuta; Nobuo Tajima; Tomohiro Sato; Michiya Fujiki; Reiko Kuroda; Yoshio Matsubara
    CRYSTENGCOMM 12 6 1688 - 1692 2010年 [査読有り]
     
    The solid-state chiral optical properties of a 1-pyrenesulfonic acid/amine supramolecular organic fluorophore could be controlled by changing the type of the aromatic ring and not the chirality of the chiral amine component molecule in the solid state.
  • Takafumi Kinuta; Kensaku Kamon; Nobuo Tajima; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    SUPRAMOLECULAR CHEMISTRY 22 4 221 - 227 2010年 [査読有り]
     
    A chiral charge-transfer (CT) complex was formed using achiral 9,10-bis(3,5-dihydroxyphenyl)anthracene (BDHA) as an electron donor and achiral 1,1'-dimethyl-4,4'-bipyridinium dichloride (MVCl2) as an electron acceptor. This chiral CT complex can include n-alkyl alcohol molecules as guests. On the other hand, when 1,1'-diphenyl-4,4'-bipyridinium dichloride and 1,1'-dibenzyl-4,4'-bipyridinium dichloride were used as electron acceptors, achiral CT complexes without guests were formed. It was found that the chiral crystallisation of the BDHA/MVCl2-CT host system was caused by steric and electric intermolecular interactions between host component molecules BDHA and MVCl2 during crystallisation.
  • Takafumi Kinuta; Tomohiro Sato; Nobuo Tajima; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    CRYSTENGCOMM 12 11 3483 - 3486 2010年 [査読有り]
     
    Although both enantiomers of two-substituted ether-and imide-bridged biphenyl compounds 1-3 are present in equal amounts at equilibrium in a solution, chiral crystals composed of one of the axially chiral enantiomers could be isolated by crystallization from the solution without any outside chiral source.
  • Noriaki Iwase; Takafumi Kinuta; Nobuo Tajima; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    CRYSTENGCOMM 12 10 3195 - 3200 2010年 [査読有り]
     
    By using p-benzoquinone as an electron acceptor, charge-transfer (CT) complexes with bisphenol A and its derivatives were successfully prepared by crystallization from a solution or solid-grinding crystallization. The colors of the obtained CT complexes varied with the type of bisphenol A derivative. This CT system may be used as a sensitive and visible indicator for bisphenol A derivatives.
  • Takafumi Kinuta; Kensaku Kamon; Takunori Harada; Yoko Nakano; Nobuo Tajima; Tomohiro Sato; Michiya Fujiki; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY 33 5760 - 5764 2009年11月 [査読有り]
     
    A solid-state, chiral, helical, columnar, organic fluorophore having a pi-conjugated phenylene ethynylene unit was prepared by using 4-[2-(4-methylphenyl)ethynyl]benzoic acid and 1-phenylethylamine. Such a chiral pi-conjugated organic fluorophore can be obtained from achiral and racemic component molecules, and it exhibits circularly polarized luminescence (CPL) in the solid state. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
  • Yoshitane Imai; Kensaku Kamon; Kakuhiro Kawaguchi; Nobuo Tajima; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara
    LETTERS IN ORGANIC CHEMISTRY 6 7 588 - 592 2009年10月 [査読有り]
     
    Guest molecules (benzene and 1,4-dioxane) can be incorporated into 9,10-dipentafluorophenylanthracene (DPFPA) by tuning the arrangement of its one-dimensional (1D) column-like structure with CF-pi interactions of its pentafluorophenyl group in the solid state. The two guest molecules are trapped in cavities due to benzene-anthracene edge-to-face and CH-pi interactions with DPFPA, respectively.
  • Takafumi Kinuta; Yuko Kise; Kensaku Kamon; Nobuo Tajima; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara; Yoshitane Imai
    TETRAHEDRON LETTERS 50 42 5786 - 5789 2009年10月 [査読有り]
     
    A novel charge-transfer (CT) host system is developed using CT complexes composed of rac-3,3'-dihydroxy-1,1'-bi-2-naphthol and 1,1'-dibenzyl-4,4'-bipyridinium dichloride. This CT host complex has a 1D channel-like cavity in which guest (MeOH and EtOH) molecules can be discharged and adsorbed. The color and DRS of the CT crystals change according to the presence of guest molecules in the host complex. (C) 2009 Elsevier Ltd. All rights reserved.
  • Hiroshi Takashima; Satomi Shibata; Yuka Sekiguchi; Yoshitane Imai; Keiichi Tsukahara
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 82 10 1250 - 1257 2009年10月 [査読有り]
     
    In order to understand the detailed mechanisms of stereoselective photoinduced electron-transfer (ET) reactions of zinc-substituted myoglobin (ZnMb) with optically active viologens by flash photolysis, we prepared new optically active agents, such as (R,R)- and (S,S)-1,1'-bis(3-hydroxy-2-methylpropyl)-4,4'-bipyridinediylium dichloride ([BMV]Cl-2). The photo-excited triplet state of ZnMb, (3)(ZnMb)*, was successfully quenched by (R,R)- and (SS)-[BMV](2+) ions to form the radical pair of ZnMb cation (ZnMb(center dot+)) and (R,R)- and (S,S)-[BMV](center dot+), followed by a thermal back ET reaction to the ground state. The ratio of the rate constants (k(q)) for ET quenching at 25 degrees C, k(q)(R,R)/k(q)(S,S) = 1.1, indicates that the (R,R)-[BMV](2+) preferentially quenches (3)(ZnMb)*. The selectivity of the rate constants (k(b)) for the back ET from (R,R)- and (SS)-[BMV](center dot+) to ZnMb(center dot+) at 25 degrees C was k(b)(R,R)/k(b)(S,S) = 0.83. The highest stereoselectivity of 1.3 for [BMV](center dot+) was found at low temperature (10 degrees C) in the thermal back ET reaction, where Delta Delta H not equal(R-S) = 6.2 +/- 1.9 kJ mol(-1) and Delta Delta S not equal(R-S) = 19 +/- 2 J mol(-1) K-1 were obtained. The structural differences between [BMV](2+) and the other viologens imply that the bulky aromatic substituent seems to be more important than the distance from the chiral center to the viologen moiety in order to enhance the ET stereoselectivity.
  • Yoshitane Imai; Kensaku Kamon; Takafumi Kinuta; Nobuo Tajima; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara
    CRYSTAL GROWTH & DESIGN 9 9 4096 - 4101 2009年09月 [査読有り]
     
    A charge-transfer (CT) complex composed of rac-3,3'-dibromo-1,1'-bi-2-naphthol as an electron donor and 1,1'-dimethyl-4-4'-bipyridinium, dichloride as an electron acceptor serves as a host system. This CT host system exhibits multiple molecular recognition property (selective inclusion behavior, change in color, and diffuse reflectance spectra of inclusion complex depending oil the included guest).
  • Yoshitane Imai; Katuzo Murata; Yoko Nakano; Takunori Harada; Tomohiro Sato; Nobuo Tajima; Michiya Fujiki; Reiko Kuroda; Yoshio Matsubara
    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY 19 3244 - 3248 2009年07月 [査読有り]
     
    By using (R)-1-phenylethylamine as a chiral molecule and 1-pyrenesulfonic acid as a fluorescent molecule, a chiral supramolecular organic fluorophore composed of a 2D layered structure was successfully developed. This chiral supramolecular fluorophore possesses circularly polarized luminescence (CPL) properties in the solid state. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
  • Yoshitane Imai; Takafumi Kinuta; Kensaku Kamon; Nobuo Tajima; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara
    CRYSTAL GROWTH & DESIGN 9 5 2393 - 2397 2009年05月 [査読有り]
     
    Chiral and racemic charge-trans fer (CT) complexes of the 1,1'-bi-2-naphthol system with tetrafluoro-1,4-benzoquinone (TFBQ) were successfully formed by using chiral and racemic 6,6'-dimethyl-1,1'-bi-2-naphthol as an electron donor. The crystal structures of CT complexes of 6,6'-dimethyl-1,1'-bi-2-naphthol with TFBQ were investigated using X-ray crystallographic analyses.
  • Yoshitane Imai; Kensaku Kamon; Takafumi Kinuta; Tomohiro Sato; Nobuo Tajima; Reiko Kuroda; Yoshio Matsubara
    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY 15 2519 - 2525 2009年05月 [査読有り]
     
    A colored, two-component, supramolecular, host system has been developed. This supramolecular host system uses a charge-transfer (CT) complex composed of racemic (rac)-1,1'-bi-2-naphthol, which acts as an electron donor, and 2,5-substituted 1,4-benzoquinone, which acts as an electron acceptor. This CT host system can selectively include aromatic guest molecules into a channel-like cavity by tuning the packing of the electron-donor and electron-acceptor molecules. Characteristically, the color and diffuse reflectance spectra (DRS) of the inclusion CT complex can be tuned by changing the type of the component 2,5-substituted 1,4-benzoquinone. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
  • Yoshitane Imai; Takafumi Kinuta; Kensaku Kamon; Nobuo Tajima; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara
    TETRAHEDRON 65 18 3740 - 3744 2009年05月 [査読有り]
     
    By using 9,10-bis(3,5-dihydroxyphenyl)anthracene as an electron donor and 1,1'-dimethyl-4,4'-bipyridinium dichloride as an electron acceptor, a spontaneously resolved charge-transfer (CT) complex is formed. This CT complex can include n-alkyl alcohol molecules as guests, and the DRS of this CT complex change with the type of component guest molecules. (C) 2009 Elsevier Ltd. All rights reserved.
  • Yoshitane Imai; Katuzo Murata; Kakuhiro Kawaguchi; Takunori Harada; Yoko Nakano; Tomohiro Sato; Michiya Fujiki; Reiko Kuroda; Yoshio Matsubara
    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY 9 1335 - 1339 2009年03月 [査読有り]
     
    A novel crystalline supramolecular organic fluorophore having a 2(1)-helical columnar structure has been prepared by solid-state co-grinding crystallization using crystals of 2-anthracenecarboxylic acid and (R)-1-(2-naphthyl)ethylamine. Although many organic fluorophores lose their fluorescence in the solid state, this supramolecular organic fluorophore exhibits fluorescence even in the solid state. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
  • Yoshitane Imai; Kensaku Kamon; Shingo Kido; Takunori Harada; Nobuo Tajima; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara
    CRYSTENGCOMM 11 4 620 - 624 2009年 [査読有り]
     
    By using an axially chiral 6,6'-disubstituted-1,1'-bis-2-naphthol as the electron donor, we successfully formed chiral charge-transfer (CT) complexes with 1,2,4,5-tetracyanobenzene (TCNB) and examined their crystal structures.
  • Yoshitane Imai; Katuzo Murata; Kensaku Kamon; Takafumi Kinuta; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara
    CRYSTAL GROWTH & DESIGN 9 1 602 - 605 2009年01月 [査読有り]
     
    A two-component supramolecular host system having multiple chiral points (central, axial, and helical), which can include an n-alkyl alcohol molecule, was successfully formed by combining (11R,12R)-9,10-dihydro-9,10-ethanoanthracene-11,12-diamine with central chirality and (S)-1,1'-binaphthyl-2,2'-dicarboxylic acid with axial chirality. The helical chirality of this host system was induced by the central and axial chiralities of the component molecules in solid state.
  • Yoshitane Imai; Takafumi Kinuta; Keiko Nagasaki; Takunori Harada; Tomohiro Sato; Nobuo Tajima; Yoh Sasaki; Reiko Kuroda; Yoshio Matsubara
    CRYSTENGCOMM 11 7 1223 - 1226 2009年 [査読有り]
     
    An achiral compound, 2-methyl-3-(2-naphthalenylthio)-1,4-naphthalenedione, shows conformational and color polymorphism, and each polymorph shows different optical properties and can be controlled by changing crystallization conditions.
  • Yoshitane Imai; Kensaku Kamon; Takafumi Kinuta; Nobuo Tajima; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara
    CRYSTAL GROWTH & DESIGN 8 10 3493 - 3496 2008年10月 [査読有り]
     
    A guest-dependent charge-transfer (CT) host system was found that was composed of racemic (rac)-1, 1'-bi-2-naphthol as an electron donor and 2-chloro-5-methyl-benzoquinone as an electron acceptor; in this complex, aromatic guests (benzene/toluene), electron-acceptor guests (tetrafluoro-1,4-benzoquinone (TF-BQ)), or alcohol guests (ethanol) can variously be included by changing the packing of electron-donor and -acceptor molecules. When ethanol was used as a guest, a chiral CT complex including ethanol was obtained.
  • Yoshitane Imai; Kensaku Kamon; Shingo Kido; Tomohiro Sato; Nobuo Tajima; Reiko Kuroda; Yoshio Matsubara
    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY 28 4784 - 4789 2008年10月 [査読有り]
     
    A charge-transfer (CT) complex composed of racemic rac-10,10'-dihydroxy-9,9'-biphenanthryl as the electron-donor and the diquaternary derivative of 4,4'-bipyridinium (viologen) as the electron-acceptor has been formed by the inclusion of guest molecules. The color and diffuse reflectance spectra of this inclusion CT complex are sensitive to the guest molecules, and their properties can be tuned by changing the component viologen derivatives. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).
  • Yoshitane Imai; Kensaku Kamon; Katuzo Murata; Takunori Harada; Yoko Nakano; Tornohiro Sato; Michiya Fujiki; Reiko Kuroda; Yoshio Matsubara
    ORGANIC & BIOMOLECULAR CHEMISTRY 6 19 3471 - 3475 2008年10月 [査読有り]
     
    A spontaneous resolution chiral fluorescent system is prepared by using 2-anthracenecarboxylic acid, and racemic (rac)-1-phenylethylamine or rac-1-cyclohexylethylamine. Although chiral functional organic materials are usually prepared using chiral molecules, in this system, a chiral organic fluorophore, which exhibits fluorescence in the solid state, is prepared from achiral and rac molecules.
  • Yoshitane Imai; Katuzo Murata; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara
    ORGANIC LETTERS 10 17 3821 - 3824 2008年09月 [査読有り]
     
    A supramolecular host system composed of a 2D layered structure was developed by combining 1,2-diphenylethylenediamine and N-phenyliminodiacetic acid. This 2D layered structure was formed by a hydrogen- and ionic-bonded network between 2(1)-helical columns.
  • Yoshitane Imai; Katuzo Murata; Natsuyo Asano; Yoko Nakano; Kakuhiro Kawaguchi; Takunori Harada; Tomohiro Sato; Michiya Fujiki; Reiko Kuroda; Yoshio Matsubara
    CRYSTAL GROWTH & DESIGN 8 9 3376 - 3379 2008年09月 [査読有り]
     
    By using achiral fluorescent 2-anthracenecarboxylic acid with achiral benzylamine, a chiral 2(1)-helical columnar organic fluorophore having circularly polarized luminescence (CPL) in the solid state is created. Although this system exhibits polymorphism, the polymorphism can be controlled by changing the crystallization method.
  • Yoshitane Imai; Katuzo Murata; Hideki Matsuno; Kensaku Kamon; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara
    CHEMISTRY LETTERS 37 7 726 - 727 2008年07月 [査読有り]
     
    A chiral supramolecular organic fluorophore is developed by using achiral biphenyl-4-carboxylic acid and rac-1-phenylethylamine. This fluorophore is a spontaneously resolved chiral fluorescence system.
  • Yoshitane Imai; Kakuhiro Kawaguchi; Hideki Matsuno; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara
    TETRAHEDRON 64 20 4585 - 4589 2008年05月 [査読有り]
     
    A tunable supramolecular phenylacetylene host system with a chiral channel-like cavity is developed by using (1R,2S)-2-amino-1,2-diphenylethanol. This host system possesses a chiral 2(1)-helical columnar structure; chiral cavities are constructed by the self-assembly of the 2(1)-helical column, and guest molecules are included by varying the packing of this column. (C) 2008 Elsevier Ltd. All rights reserved.
  • Yoshitane Imai; Kakuhiro Kawaguchi; Katuzo Murata; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara
    ORGANIC LETTERS 10 3 469 - 471 2008年02月 [査読有り]
     
    In a two-component columnar host system composed of racemic (rac)-1,2-diphenylethylenediamine and rac-1,1'-binaphthyl-2,2'-dicarboxylic acid, a cavity tuning mechanism resulted from changes in the structure of the columns using a specific combination of the following four molecules: (1R,2R)-1, (1S,2S)-1, (R)-2, and (S)-2.
  • Yoshitane Imai; Kakuhiro Kawaguchi; Tomohiro Sato; Nobuo Tajima; Reiko Kuroda; Yoshio Matsubara
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 487 153 - 159 2008年 [査読有り]
     
    9,10-Diphenylanthracene (DPA) permits the inclusion of guest molecules (hexafluorobenzene and 1,4-dioxane) by changing the arrangement of its two-dimensional layers and the size of the cavities formed by these layers in a solid state. In particular, the 1,4-dioxane guest molecules are trapped along the cavities by CH-pi interactions with DPA. Crystal data for hexafluorobenzene inclusion complex in DPA,triclinic, space group P (1) over bar, a=6.118(2), b=7.571(2), c=12.982(4) angstrom, alpha=78.366(4)degrees, beta=85.001(5)degrees, gamma=81.687(5)degrees, U=581.7(3)degrees angstrom(3), Z=2. Crystal data for 1,4-dioxane inclusion complex in DPA, triclinic, space group P (1) over bar, a=5.931(1), b=7.625(1), c=12.103(1) angstrom, alpha=85.404(2)degrees, beta=76.300(2)degrees, gamma=82.909(2)degrees, U=526.96(9) angstrom(3), Z=2.
  • Yoshitane Imai; Kenta Kawano; Yoko Nakano; Kakuhiro Kawaguchi; Takunori Harada; Tomohiro Sato; Michiya Fujiki; Reiko Kuroda; Yoshio Matsubara
    NEW JOURNAL OF CHEMISTRY 32 7 1110 - 1112 2008年 [査読有り]
     
    The sign of circularly polarized luminescence (CPL) of a chiral 2(1)-helical columnar organic fluorophore was successfully controlled in the solid-state by changing an achiral fluorescence component molecule, and not by using a chiral component molecule with opposite chirality.
  • Yoshitane Imai; Katuzo Murata; Hideki Matsuno; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara
    CRYSTENGCOMM 10 8 947 - 950 2008年 [査読有り]
     
    A supramolecular host complex with multiple chiral points, which can include an alkyl alcohol, was successfully formed by combining (1R,2S)-2-amino-1,2-diphenylethanol and (S)-1,1'-binaphthyl-2,2'-diyl hydrogen phosphate.
  • Reiko Kuroda; Tomohiro Sato; Yoshitane Imai
    CRYSTENGCOMM 10 12 1881 - 1890 2008年 [査読有り]
     
    Co-grinding of crystals of diols (electron donor) and benzoquinone (BQ, electron acceptor), and in some cases with crystals of a third aromatic compound, produces charge transfer (CT) complex crystals in the solid state without going through an obvious amorphous state, followed by a change in colour and in powder X-ray diffraction patterns. A milling power above a threshold is required for the new CT complex crystal formation, however, in some cases simple mixing of pulverized crystals is good enough to initiate the transformation. On exposing the CT complex crystals to air, without any mechanochemical force, they revert to the starting diol crystals by losing sublimable BQ molecules, rearranging hydrogen bonds and establishing a three-dimensional periodicity. Remarkably, solid-state and conventional solution crystallization give different results, i.e., formation or non-formation of CT complex crystals, or formation of different crystals with different colours. The phenomenon is surprisingly frequent and all three two-component CT systems and six out of the nine three-component systems investigated, exhibit different crystallization behaviour. A quartet structure where two BQ molecules are sandwiched by two naphthols was formed in the crystal obtained from solid-state crystallization. A new triplet CT complex structure in which a BQ is sandwiched by a naphthol and a biphenyl is also reported.
  • Yoshitane Imai; Katuzo Murata; Kakuhiro Kawaguchi; Tomohiro Sato; Nobuo Tajima; Reiko Kuroda; Yoshio Matsubara
    CHEMISTRY-AN ASIAN JOURNAL 3 3 625 - 629 2008年 [査読有り]
     
    A solid-state fluorescent host system was created by self-assembly of a 2(1)-helical columnar organic fluorophore composed of (1R,2S)-2-amino-1,2-diphenylethanol and fluorescent 1-pyrenecarboxylic acid. This host system has a characteristic 2(1)-helical columnar hydrogen- and ionic-bonded network. Channel-like cavities are formed by self-assembly of this column, and various guest molecules can be included by tuning the packing of this column. Moreover, the solid-state fluorescence of this host system can change according to the included guest molecules. This occurs because of the change in the relative arrangement of the pyrene rings as they adjust to the tuning of the packing of the shared 2(1)-helical column, according to the size of the included guest molecules. Therefore, this host system can recognize slight differences in molecular size and shape.
  • Yoshitane Imai; Kakuhiro Kawaguchi; Nobuo Tajima; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara
    CHEMICAL COMMUNICATIONS 3 362 - 364 2008年 [査読有り]
     
    Spontaneously resolvable conglomerate crystals are obtained by combining racemic (rac)-1,1'-binaphthyl-2,2'-dicarboxylic acid and rac-1,2-diphenylethylenediamine, and this spontaneous resolution system is induced by water which is present in the crystallization solvent.
  • Yoshitane Imai; Keiko Nagasaki; Katuzo Murata; Kakuhiro Kawaguchi; Takunori Harada; Yoko Nakano; Tomohiro Sato; Michiya Fujiki; Reiko Kuroda; Yoshio Matsubara
    CRYSTENGCOMM 10 8 951 - 953 2008年 [査読有り]
     
    By using racemic (rac)-2-amino-1,2-diphenylethanol and achiral fluorescent 1-fluorenecarboxylic acid, a two-component columnar host system with multiple molecular response (guest-dependent spontaneous resolution and fluorescence) properties in the solid state was created.
  • Yoshitane Imai; Kensaku Kamon; Takafumi Kinuta; Nobuo Tajima; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara
    TETRAHEDRON 63 48 11928 - 11932 2007年11月 [査読有り]
     
    Chiral charge-transfer (CT) complexes composed of a chiral 1,1 '-bi-2-naphthol cluster as the electron donor and 1,1 '-dibenzyl-4,4 '- bipyridinium dichloride as the electron acceptor serve as a host system for molecular recognition. CT complexes that include guest alcohols show different diffuse reflectance spectra (DRS) depending on the included guest. (c) 2007 Elsevier Ltd. All rights reserved.
  • Yoshitane Imai; Shingo Kido; Kensaku Kamon; Takafumi Kinuta; Tomohiro Sato; Nobuo Tajima; Reiko Kuroda; Yoshio Matsubara
    ORGANIC LETTERS 9 24 5047 - 5050 2007年11月 [査読有り]
     
    A charge-transfer (CT) complex, composed of 10,10'-dihydroxy-9,9'-biphenanthryl as the electron donor and 1,1'-dimethyl-4,4'-bipyridinium dichloride as the electron acceptor, is formed only by the inclusion of guest molecules. The color of this inclusion CT complex is sensitive to the component guest molecules.
  • Yoshitane Imai; Kensaku Kamon; Takafurni Kinuta; Tajima Nobuo; Tornohiro Sato; Reiko Kuroda; Yoshio Matsubara
    TETRAHEDRON LETTERS 48 36 6321 - 6325 2007年09月 [査読有り]
     
    A charge-transfer (CT) complex, composed of rac-3,3 '-dibromo-1,1 '-bi-2-naphthol as the electron donor and 1,1 ' dimethyl-4,4 '-bipyridinium dichloride as the electron acceptor, is formed only by the inclusion of specific guest molecules. The color of this inclusion CT complex is sensitive to the component guest molecules. (c) 2007 Elsevier Ltd. All rights reserved.
  • Yoshitane Imai; Kakuhiro Kawaguchi; Katuzo Murata; Tomohiro Sato; Reiko Kuroda'; Yoshio Matsubara
    CRYSTAL GROWTH & DESIGN 7 9 1676 - 1678 2007年09月 [査読有り]
     
    A tunable supramolecular host system with multiple chiral points was developed by combining (1S,2S)-1,2-cyclohexanediamine and (R)-1,1'-binaphthyl-2,2'-dicarboxylic acid.
  • Yoshitane Imai; Katuzo Murata; Kakuhiro Kawaguchi; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara
    ORGANIC LETTERS 9 17 3457 - 3460 2007年08月 [査読有り]
     
    A solid-state fluorescence sensing system was created by using a chiral supramolecular organic fluorophore having a channel-like cavity composed of (1R,2S)-2-amino-1,2-diphenylethanol as a chiral molecule and 2-anthracenecarboxylic acid as a fluorescence molecule.
  • Yoshitane Imai; Kakuhiro Kawaguchi; Katuzo Murata; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara
    CHEMISTRY LETTERS 36 6 812 - 813 2007年06月 [査読有り]
     
    A chiral supramolecular host system was developed by combining (1R,2R)-1,2-diphenylethylenediamine and benzenediacetic acid derivatives. These supramolecular complexes are constructed by the self-assembly of a chiral 2D-layered network structure with multiple chiral points derived from chiral transfers.
  • Yoshitane Imai; Kakuhiro Kawaguchi; Takunori Harada; Tomohiro Sato; Masaaki Ishikawa; Michiya Fujiki; Reiko Kuroda; Yoshio Matsubara
    TETRAHEDRON LETTERS 48 16 2927 - 2930 2007年04月 [査読有り]
     
    By using (IR,2R)-1,2-diphenylethylenediamine as a chiral molecule and 2-anthracenecarboxylic acid as a fluorescent molecule, we created a chiral supramolecular organic fluorophore having circularly polarized luminescence properties in the solid-state. (c) 2007 Elsevier Ltd. All rights reserved.
  • Yoshitane Imai; Junichi Kitazawa; Tomohiro Sato; Nobuo Tajima; Reiko Kuroda; Yoshio Matsubara; Zen-ichi Yoshida
    TETRAHEDRON 63 9 1995 - 1999 2007年02月 [査読有り]
     
    Two simple biphenyl compounds, I and 11, linked by diethyl ether chains have been synthesized. These biphenyl compounds are able to respectively rotate about an internal axis. From X-ray analyses, it was found that the 2,2'-linked biphenyl compound I can transmit the same axial chirality of the biphenyl backbones through the diethyl ether chains. On the other hand, in the 3,3'-linked biphenyl compound II, the opposite axial chirality of the biphenyl backbones is transmitted. (c) 2006 Elsevier Ltd. All rights reserved.
  • Yoshitane Imai; Kakuhiro Kawaguchi; Katuzo Asai; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara
    CRYSTENGCOMM 9 6 467 - 470 2007年 [査読有り]
     
    A complex with a chiral channel-like cavity which can incorporate various n-alkyl alcohols and reversibly discharge and adsorb them, was successfully formed by combining chiral 1,2-diphenylethylenediamine ((1S,2S)-1) and biphenylacetic acid (2).
  • Yoshitane Imai; Kakuhiro Kawaguchi; Tomohiro Sato; Reiko Kuroda; Yoshio Matsubara
    TETRAHEDRON LETTERS 47 45 7885 - 7888 2006年11月 [査読有り]
     
    A tunable chiral host system was developed by the self-assembly of a chiral 2(1)-column structure formed from (1R,2R)-1,2-diphenylethylenediamine and dicarboxylic acid. This host system can include guest molecules by changing the packing of a chiral 21-column enantioselectively. (c) 2006 Elsevier Ltd. All rights reserved.
  • Yoshitane Imai; Nobuo Tajima; Tomohiro Sato; Reiko Kuroda
    ORGANIC LETTERS 8 14 2941 - 2944 2006年07月 [査読有り]
     
    Charge-transfer (CT) complexes composed of 1,1-bi-2-naphthol derivatives as an electron donor and p-benzoquinone as an acceptor serve as an excellent host system for visual molecular recognition. This is because they form inclusion crystals with guest aromatic compounds which display remarkably different colors depending on the structure of the component molecules and on the method of crystallization (i.e., solution crystallization or solid cogrinding of component crystals).
  • Y Imai; T Kinuta; T Sato; N Tajima; R Kuroda; Y Matubara; Z Yoshida
    TETRAHEDRON LETTERS 47 21 3603 - 3606 2006年05月 [査読有り]
     
    By using three types of viologen derivatives, we synthesized chiral charge-transfer (CT) complexes with an axially chiral 1,1'-bi-2-naphthol molecule and successfully controlled the crystal structure and inclusion ability of the third component by changing the viologens. (c) 2006 Elsevier Ltd. All rights reserved.
  • Y Imai; M Takeshita; T Sato; R Kuroda
    CHEMICAL COMMUNICATIONS 10 1070 - 1072 2006年 [査読有り]
     
    By using (1R, 2R)-1,2-diphenylethylenediamine as a single enantiopure compound, we achieved a novel successive optical resolution of more than one kind of racemic compound through supramolecular crystallization.
  • Y Imai; T Sato; R Kuroda
    CHEMICAL COMMUNICATIONS 26 3289 - 3291 2005年 [査読有り]
     
    A novel tunable multi-chiral supramolecular host system was developed from non-chiral dicarboxylic acid and (1R, 2R)-diphenylethylenediamine via chirality transfer, which enabled highly efficient optical resolution of secondary alkyl alcohols by simple crystallization of host compounds from alcohol solution.
  • R Kuroda; K Higashiguchi; S Hasebe; Y Imai
    CRYSTENGCOMM 6 463 - 468 2004年09月 [査読有り]
     
    Either co-milling or simple mixing of benzoquinone (BQ) and diol crystals of varied melting point temperature produces adduct crystals through very slow and gradual molecular diffusion processes in the solid state. Their formation process was compared and discussed based on the crystal structures of the starting diols and the diol-BQ adducts.
  • EY Cheung; SJ Kitchin; KDM Harris; Y Imai; N Tajima; R Kuroda
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 125 48 14658 - 14659 2003年12月 [査読有り]
  • R Kuroda; Y Imai
    MENDELEEV COMMUNICATIONS 3 148 - 149 2003年05月 [査読有り]
     
    Spontaneous rearrangement of hydrogen bonding in a crystalline phase was observed in molecular crystals, which included sublimable benzoquinones.
  • Imai Yoshitane; Tajima, N; Sato, T; Kuroda, R
    Chirality 14 7 604 - 609 2002年07月 [査読有り]
     
    Molecular recognition in solid-state crystallization involving derivatives of 1,1'-bi-2-naphthol and benzoquinone was studied. No adduct crystal was formed when crystals of biphenyl were further added as a third component to a grinding mixture of crystals of chiral 1,1'-bi-2-naphthol and benzoquinone, which by itself did not form an adduct. This contrasts with the case in which further addition of naphthalene crystals to the same mixture produced a new red crystal. Adduct formations using chiral 6,6'-dibromo-1,1'-bi-2-naphthol in place of 1,1'-bi-2-naphthol were also studied. In this case, adducts were produced either with or without biphenyl as a third compound, but the colors of the adducts differed significantly in the two cases: red and bluish-black. The same three-component adduct crystals were produced from solid-grinding and solution crystallization and the structure was determined by X-ray diffractometry. Based on the crystal structures, theoretical calculations were carried out to compare the mechanism of colorations in the binary and the ternary complexes.
  • R Kuroda; Y Imai; N Tajima
    CHEMICAL COMMUNICATIONS 23 2848 - 2849 2002年 [査読有り]
     
    Co-grinding of crystals of racemic-bis-beta-naphthol (rac-BN) and benzoquinone (BQ) produces a novel crystal adduct through crystal sheering and molecular diffusion processes in the solid state, which is structurally distinct from adducts obtained from solution or melt.
  • Kuroda, R; Imai Yoshitane; Sato, T
    Chirality 13 9 588 - 594 2001年10月 [査読有り]
     
    New adduct crystals were obtained by simply mixing/grinding component crystals of bis-beta -naphthol (BN) derivatives with benzoquinone (BQ) under solvent-free conditions. Chiral recognition was found to operate during this process and either a racemic or a chiral crystal of a BN derivative produced an adduct crystal with BQ by solid-state crystallization. The chirality preference changed subtly according to the molecular structure of the BN derivative. Even in circumstances in which no adduct was formed, addition of a third component, such as crystals of naphthalene, to the grinding mixture yielded an adduct crystal. Remarkably, these adduct crystals were found to decompose spontaneously with time and revert to the starting crystal of the BN derivative by losing BQ molecules from the crystal lattice. Local melting of crystals by the grinding pressure was found unlikely to be the mechanism of adduct formation. Overall, these results demonstrate that molecules in the solid state could change their relative location and hydrogen bonding partners, thereby exerting chiral discrimination. Chirality 13:588-594, 2001. (C) 2001 Wiley-Liss, Inc.
  • WB Zhang; H Yoshinaga; Y Imai; T Kida; Y Nakatsuji; Ikeda, I
    SYNLETT 10 1512 - 1514 2000年10月 [査読有り]
     
    Several tetrasubstituted oxazolinylferrocene ligands were prepared, and with these ligands, up to 97% chemical yield and 93% ee were afforded in asymmetric alkylation of benzaldehyde with diethylzinc. It was found that the C-2-symmetric ligands afforded almost the same enantioselectivity but different catalytic activity with their diastereomer, C-1-symmetric ligands, in this test reaction. The bulkiness of the substituent on the oxazoline ring has significant effect on the enantioselectivity and particularly on catalytic activity. These effects of the symmetry and the bulkiness of the substituent on the oxazoline ring of the ligands on asymmetric catalysis have been rarely reported. A plausible mechanism is proposed.
  • Y Imai; WB Zhang; T Kida; Y Nakatsuji; Ikeda, I
    JOURNAL OF ORGANIC CHEMISTRY 65 11 3326 - 3333 2000年06月 [査読有り]
     
    Novel C-2-symmetric chiral bisoxazoline ligands 1 were easily prepared from enantiomerically pure 2-amino alcohols and achiral 2,2'-biphenyldicarboxylic acid via the corresponding amide and mesylate as intermediates. Since these ligands bear only two ortho-substituents on the biphenyl backbone, the biphenyl axis is not fixed, and the two diastereomers of these ligands exist in equilibrium in solution. Interestingly, when the ligands 1 were coordinated with a metal ion, only one of the two possible diastereomer complexes, an (S,aS,S)-complex, can be formed depending on the combination of the ligand and the metal ion. Thus, copper(I) afforded only the (S,aS,S)-complexes with all ligands 1, while zinc(II), palladium(II), and silver(I) afforded the (S,aS,S)-complexes as the sole product only with Ib, which has a bulky tert-butyl group on the oxazoline ring, and a mixture of the two diastereomer complexes with 1a,c,d. The copper(I)-catalyzed asymmetric cyclopropanation of styrene with diazoacetate proceeded successfully with these ligands and good to excellent enantioselectivities were afforded.
  • Y Imai; S Matsuo; WB Zhang; Y Nakatsuji; Ikeda, I
    SYNLETT 2 239 - 241 2000年02月 [査読有り]
     
    Novel C-2-symmetric bisoxazoline ligands 4 and 5 having an axis-fixed and -unfixed biaryl backbone, respectively, and a hydroxyl group in the substituent of the oxazoline ring, were prepared from biaryl dicarboxylic acids and L-serine methyl ester hydrochloride through the corresponding bisoxazolines 7 and the biphenyl derivative bearing a methoxycarbonyl substituent as the intermediate. With these ligands, up to 88% ee was afforded for the asymmetric alkylation of benzaldehyde with diethylzinc.
  • Y Imai; WB Zhang; T Kida; Y Nakatsuji; Ikeda, I
    SYNLETT 8 1319 - 1321 1999年08月 [査読有り]
     
    A novel axial chiral sulfur-oxazoline ligand with a biphenyl backbone 3 exists as a mixture of two diastereomers in equilibrium in solution. However, when this ligand was coordinated with palladium(II), only one of the two possible diastereomeric complexes, (S,aS)-7, was formed. With this ligand, up to 82% ee was attained for the palladium-catalyzed asymmetric allylic allkylation.
  • Imai Yoshitane; Zhang, W; Kida, T; Nakatsuji, Y; Ikeda, I
    Chem. Lett. 3 243 - 244 1999年03月 [査読有り]
     
    Upon complexation with Pd(II), both chiral 1,1'-bis(oxazolinyl)ferrocene ligand 1 and its planar chiral derivative 2 afforded the corresponding 1:2 ligand-Pd(II) complex. On the other hand, upon complexation with copper(I) chloride, both 1 and 2 afforded only one of the two possible diastereomeric 1:1 ligand-Cu(I) complexes. The twists of the two Cp rings of the copper(I) complexes of 1 and 2 are opposite to each other, which is ascribed to the effect of the planar chirality in 2.
  • Y Imai; WB Zhang; T Kida; Y Nakatsuji; Ikeda, I
    TETRAHEDRON LETTERS 39 24 4343 - 4346 1998年06月 [査読有り]
     
    Novel diphenylphosphinooxazoline ligands with a chiral binaphthyl backbone were prepared. It was interestingly found that the two diastereomeric ligands afforded two enantiomeric products, respectively, with excellent catalytic activities and enantioselectivities for the palladium-catalyzed allylic alkylation, regardless of the identical (S)-oxazoline ring existing in both ligands. This is the first example using an (S)-oxazoline ligand to afford an (R)-product for this reaction. (C) 1998 Elsevier Science Ltd. All rights reserved.
  • Y Imai; WB Zhang; T Kida; Y Nakatsuji; Ikeda, I
    TETRAHEDRON LETTERS 38 15 2681 - 2684 1997年04月 [査読有り]
     
    The two diastereomers of novel C-2-symmetric bisoxazoline ligand bearing only two ortho-substituents 4 exist in equilibrium in solution, However, when the ligand was coordinated with Cu(I), only one of the two possible diastereomeric complexes, 5-(S,S,S), was formed. With this complex as a chiral catalyst, up to 92% ee was attained for the asymmetric cyclopropanation of styrene with diazoacetate. (C) 1997 Elsevier Science Ltd.
  • Y Imai; WB Zhang; T Kida; Y Nakatsuji; Ikeda, I
    TETRAHEDRON-ASYMMETRY 7 8 2453 - 2462 1996年08月 [査読有り]
     
    Novel C-2-symmetric chiral bisoxatoline ligands with four asymmetric centers were readily synthesized from the two enantiomers of tartaric acid and several aminoacids via the corresponding bis(beta-hydroxylamide)s and dimesylates as successive intermediates. With these novel chiral bisoxazoline ligands, rhodium(I)-catalyzed hydrosilylation of acetophenone was carried out and the effects of the combination of the four asymmetric centers as well as the substituent on oxazoline ring of the ligands on the reaction were studied. Copyright (C) 1996 Elsevier Science Ltd

書籍

  • Advances in Organic Crystal Chemistry, Comprehensive Reviews 2020
    Yoshitane Imai (担当:分担執筆範囲:Circularly Polarized Luminescence from Solid-State Chiral Luminophores)Springer 2020年
  • Circularly Polarized Luminescence of Isolated Small Organic Molecules
    Yoshitane Imai (担当:分担執筆範囲:Circularly Polarized Luminescence of Axially Chiral Binaphthyl Fluorophores)Springer 2020年
  • Advances in Organic Crystal Chemistry, Comprehensive Reviews 2015
    Yoshitane Imai (担当:分担執筆範囲:Solid-State Circularly Polarized Luminescence of Chiral Supramolecular Organic Fluorophore)Springer 2015年

MISC

受賞

  • 2019年 日本油化学会オレオマテリアル賞
  • 2009年 コニカミノルタ画像科学進歩賞（平成21年）

共同研究・競争的資金等の研究課題

  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2023年04月 -2027年03月 
    代表者 : 今井 喜胤; 八木 繁幸
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2021年04月 -2024年03月 
    代表者 : 靜間 基博; 今井 喜胤
     
    円偏光発光(CPL)特性を有するフレキシブルな構造を有する分子認識化合物を合成し、ゲスト化合物の添加で容易にCPLのキラルスイッチングおよび発光波長制御が行える材料の創成することを目的とする。 今年度は中心のオキシエチレン鎖がゲストとして想定しているカチオン類とのバインディングサイトであり、キラル源として単糖を用いる。両末端に蛍光発光部位を有し、ゲストの錯形成でホストが擬似環状構造になることで２つの蛍光発光部位の配置を変えることができ、発光挙動を制御できると考えて分子設計をした。 ガラクトースから多段階有機合成によりすべての水酸基がアセチル化した合成中間体を合成した。カチオンゲストとのバインディングサイトとなる糖骨格をつなぐオキシエチレン鎖の長さが異なるホストを合成した。オキシエチレン鎖の長さは波長制御の鍵となると考えたためである。初めにガラクトースをアセトンアセタール化した。これを種々の長さのオキシエチレン骨格の両末端にWilliamsonエーテル合成で連結した。３つの生成物それぞれを酸加水分解によりアセタールを除去後、無水酢酸とピリジン中で反応してアセチル化した。臭化水素と反応して臭化グリコシドを合成した。ハロゲン化グリコシドと発光部位である1-ピレンメタノールとを炭酸銀を触媒としてKoenigs-Knorr反応でグリコシル化した。目的物はMSおよびNMRで確認した。当初目的の完全メチル化体を合成するまでは至らなかったが、最終目的物の2段階前の中間体の合成を行うことができた。合成手順、手法を確立することができた。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2021年07月 -2023年03月 
    代表者 : 今井 喜胤
     
    本研究の目的は、アキラルあるいは光学不活性な有機発光体からフレミングの左手則に従って外部電場による円偏光発光(CPL)の発生と左右性の制御が可能であることを実証することにある。近年、キラル（光学活性）な有機発光体を用いた円偏光発光ダイオード（CP-OLED）の研究が活発に行われているものの、有機化学の常識からすれば、左右一組のCP-OLEDを実現するにはR・S対のCPL分子材料とその原料を必要とする。 そこで、化学的不斉源を持たないアキラルあるいは光学不活性な発光体から、外部電場、外部磁場によりCPL発光が可能になれば、不斉合成や光学分割などの操作が不要になり、CPL材料設計の自由度が格段に広がる。工業的視点からも、革新的手法に繋がる。 本研究では、まず、ラセミ体の光学的に不活性なルテニウム発光体に外部磁場を印加することにより磁気円偏光発光(MCPL)の発現について検討した。溶液中、PLおよびMCPLを測定したところ、ラセミ体であるにもかかわらず、明確なモノマーPLおよびMCPLを観測することに成功した。興味深いことに、同一のルテニウム発光体において外部磁場を反転させたところ、外部磁場の方向がS→NとN→Sでは、MCPLの符号を反転させることに成功した。この成果は、今後の電気化学発光(ECL)デバイスの開発につながる成果と期待される。
  • 科学技術振興機構：産学が連携した研究開発成果の展開 研究成果展開事業 研究成果最適展開支援プログラム(A-STEP) トライアウト トライアウト
    研究期間 : 2022年 -2023年 
    代表者 : 今井 喜胤
     
    光には右回転と左回転、二種類の回転する光・円偏光発光(CPL)が存在する。本研究では、アキラルあるいは光学不活性な発光体を発光層に用い、デバイスに外部磁場を印加することにより、CPLを発する磁場駆動OLED(MCP-OLED)、磁場駆動電気化学発光デバイス(MCP-LEC)の開発を行う。
  • 日本学術振興会：科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2020年04月 -2022年03月 
    代表者 : 今井 喜胤
     
    本研究課題は、発光体を、エラストマーなどの有機高分子中あるいは無機固体中にドーピングすることにより、機能性を有するソフト円偏光発光(CPL)材料を開発するものである。機能性ソフトCPL材料への展開を指向し、外部環境を変化させることにより、CPL特性を制御できる非古典的円偏光発光(NC-CPL)システムについて検討した。 まず、ぺリレン骨格のベイポジションのπ共役を拡張した新規光学活性ペリレンジイミド発光体の合成に高収率で成功した。有機高分子PMMA-filmに、合成したぺリレンジイミド発光体をドープし、CPLスペクトルを測定したところ、ペリレン由来のCPLを観測し、置換基を拡張することにより異方性の増加が観測された。興味深いことに、置換基の違いにより、同じキラリティーを有しているにも関わらずCPL符号の完全な反転が観測された。 続いて、ラセミ体の有機-無機ハイブリッドイリジウム発光体Ir(Ⅲ)(piq)3, Ir(Ⅲ)(ppy)3, Ir(Ⅲ)(F2-ppy)2(pic)および Ir(Ⅲ)(BT)2(acac)において、赤色、緑色、青色、黄色の磁気円偏光発光(MCPL)特性の発現に成功した。外部磁場の方向を反転させることにより、MCPLの符号を反転させることに成功した。この有機イリジウム(III)錯体Ir(III)(ppy)3とIr(III)(ppy)2(acac)を発光層に埋め込むことにより，外部磁場誘起円偏光電界発光(MCPEL)デバイスを開発した。このデバイスは、CPELを発し、その光の回転方向は、Ir(III)錯体の配位子の種類とファラデー配置に基づく磁気の方向で制御することに成功した。
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    研究期間 : 2019年04月 -2022年03月 
    代表者 : 村井 利昭; 平田 洋子; 宇田川 太郎; 今井 喜胤
     
    炭素上にキラリティーを有する分子に加えて、炭素以外の典型元素化合物のキラリティー制御に関する基礎的な概念の構築や，実際の化合物群の合成、それら化合物の物質機能の解明と利用は、合成化学における重要な課題である。特に周期表第三周期以降の元素へのキラリティーの選択的導入により、光学活性配位子としての応用だけでなく、光学活性な酸あるいは塩基触媒、キラル分子の識別、生理活性の発現や、蛍光発光部位との組み合せによる円偏光発光の実現など、合成化学を端緒とした、生命化学や材料化学への展開を指向した多彩な機能創出が期待できる。そこで本研究では、P-キラルリン化合物を導く独自の反応開発をベースに、合成化学、生化学さらには材料化学分野でも、発展性のある低分子有機化合物群の提供を目指してきた。 具体的にはビナフチル基を有する四配位五価リン化合物を出発化合物として、われわれが世界で初めて発見したキラリティー転写反応を経たリン原子上キラルな光学活性化合物の一般的合成法の開発を基盤として、新しい分子キラリティーの世界を開拓している。ここでリン原子上には、単結合で三種類の異なる置換基を導入でき、また形式的二重結合を介して、三通りの元素すなわち酸素、硫黄、セレン原子を連結することができるため、数多くの誘導体を描くことができると同時に、それぞれを高効率、高選択的に導くことがここでの目的であり、実際にそれぞれの場合の反応条件の最適化を行ってきた。また一連のリン原子上での反応経路の詳細を、取りうるすべての中間体を自動的に発見できる GRRM法を用いた理論計算によって解析した。ついで得られた化合物群を基軸として光学活性ルイス塩基触媒を提供するとともに、得られた化合物群の毒性評価と細胞内シグナルタンパク質の挙動解析を経た構造活性相関に関する知見を蓄積してきた。
  • 革新的キラル発光および評価技術の創成
    国立研究開発法人科学技術振興機構：CREST
    研究期間 : 2021年04月 -2022年03月
  • 日本学術振興会：科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2019年04月 -2021年03月 
    代表者 : 今井 喜胤
     
    一般的に、有機-無機ハイブリッド発光体、有機発光体から円偏光発光(CPL)を作り出す場合、光学活性な発光体を用いる。本研究では、ラセミ体あるいはアキラルな有機-無機ハイブリッド発光体、有機発光体を用い、外部磁場を用いることにより、磁気円偏光発光(MCPL)の発出を試みた。 ラセミ体のEu(III)(hfa)3, Tb(III)(hfa)3などのランタノイド発光体や、それらに各種有機配位子を組み合わせた有機-ランタノイドハイブリッド発光体に外部磁場を印加し、MCPLを測定したところ、ラセミ体であるにもかかわらず、Eu(III)、Tb(III)由来のシャープな10-2~10-3/T-1 オーダーのMCPLを観測することに成功した。さらに、磁場の方向(N-UpあるいはS-Up)を変えることにより、MCPLの回転方向を制御することにも成功した 量子ドットは、その粒子径を変えることで発光波長を変えることができる。そこで、アキラルな量子ドットCdS/ZnSに外部磁場を印加することによるMCPL特性について検討した。その結果、CdS/ZnS(粒子径:4.5 nm)は固体状態とPMMA状態で、外部磁場を印加することにより、410 nm付近にS-Up(S→N)で正(+)のMCPLを示し、N-Upでは負(-)のMCPLを示した。 さらに、無機発光体、Y2O3:Eu (赤), BaMgAl10O17:Eu, Mn (緑) BaMgAl10O17:Eu (青)を粉末状態でMCPL特性評価したところ、キラリティを持たないにも関わらず極大MCPL波長(λMCPL)608 nm, 511 nm, 441 nmでそれぞれMCPLを観測することに成功した。
  • 日本学術振興会：科学研究費助成事業 基盤研究(C)
    研究期間 : 2018年04月 -2021年03月 
    代表者 : 今井 喜胤
     
    当研究室ではこれまでに、円偏光発光(CPL)特性を備えた各種光学活性ペプチド-ピレン有機発光体の開発に成功している。 本研究では、光学活性ペプチド-ピレン有機発光体にピぺリジンユニットを導入することによる、溶媒依存CPL特性の制御について検討した。 ピぺリジンユニットを導入した光学活性ペプチドのCPLスペクトルを、ジクロロメタン溶液中、およびDMF溶液中、測定した。その結果、両溶媒においてCPLを観測することに成功し、そのCPL波長は、ジクロロメタン溶液中では449 nm、DMF溶液中では488 nmであった。興味深いことに、ピぺリジンユニットを導入することにより、ピぺリジンユニット導入前のペプチド-ピレン有機発光体で観測された溶媒依存CPL反転が、阻害されることを見出した。 以上、光学活性ペプチド-ピレン発光体において、ピペリジンユニットの有無により、CPLの溶媒依存チューニング特性を制御することに成功した。
  • 日本学術振興会：科学研究費助成事業 基盤研究(C)
    研究期間 : 2015年04月 -2018年03月 
    代表者 : 今井 喜胤
     
    一般的手法により、左回転の光を出す円偏光発光(CPL)発光体、右回転の光を出すCPL発光体を得るには、有機合成的手法を用い、分子構造のどこかに、それぞれ右手と左手の関係にある不斉炭素（[R]および[S]）などの導入が必要である。本研究では、有機合成的手法をできるだけ回避し、光学活性な発光性分子を、各種物性を有する有機あるいは無機マトリックス中にドーピングすることにより、光の回転方向の制御に成功した。
  • ペプチドを利用した新奇円偏光発光(CPL)素材の開発
    新素材情報財団研究助成金：
    研究期間 : 2017年 
    代表者 : 今井喜胤
  • 日本学術振興会：科学研究費助成事業 基盤研究(C)
    研究期間 : 2012年04月 -2015年03月 
    代表者 : 今井 喜胤; 黒田 玲子
     
    機能の異なる2種類の機能性分子（発光性分子と光学活性分子あるいは光学活性有機発光体とマトリックス）を組み合わせることにより、円偏光発光(CPL)特性を有する光学活性ハイブリッド超分子有機発光体の開発に成功した。さらに、同じ軸性キラリティーを有する光学活性ビナフチル有機発光体において、光学活性ビナフチルの二面体角の角度の違い、光学活性ビナフチルユニットの永久双極子モーメントの方向の違い、さらには外部マトリックスの違いにより、CPLの回転方向の制御に成功した。
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    研究期間 : 2010年04月 -2014年03月 
    代表者 : 藤木 道也; 今井 喜胤; 黒田 玲子
     
    パリティー非保存説の妥当性を検証するため円二色分光法による測定解析を可能にする紫外・可視吸収発光性の高分子を用い、1.アキラル系→ホモキラル系、2. ラセミ系→ホモキラル系の構築を通じて、光学不活性な世界から光学活性な世界へ至るシナリオを描くことを目指した。シグマ共役ポリシランとパイ共役高分子を用い、良溶媒・貧溶媒を最適化して左右どちらかの光学活性高分子を発生した。リモネンキラリティー転写法、円偏光キラリティー転写法により発生させた光学活性π共役らせん高分子の発生に伴う 円偏光吸収特性, 旋光度分散、円偏光発光特性において左右の差異が認められ、パリティー非保存の可能性が示唆された。
  • 非古典的手法による次世代円偏光発光スイッチ・増幅システムへの挑戦
    池谷科学技術振興財団：
    研究期間 : 2014年 
    代表者 : 今井喜胤
  • 日本学術振興会：科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2011年04月 -2013年03月 
    代表者 : 今井 喜胤
     
    一般的に、光学活性材料のキラリティーに基づく光学特性を反転させるには、逆のキラリティーを有する光学活性分子を用いる。 本研究では、同じ絶対配置を有する軸不斉ビナフチル化合物の非古典的CPL特性制御について検討を行った。 軸不斉ビナフチル化合物として、光学活性な(S)-2,2'-Diethoxy-1,1'-binaphthyl [(S)-1]および(S)-2,2'-(1,4-Butylenedioxy)-1,1'-binaphthyl [(S)-2]を用いた。はじめに、(S)-1, 2のchloroform溶液中の蛍光スペクトルの測定を行ったところ、極大蛍光波長 = 365、368 nm でそれぞれ蛍光特性を示した。次に、(S)-1, 2のchloroform溶液中でのCPLスペクトルを測定した。興味深い事に、g-因子約+0.001, -0.0014と、同じ軸不斉を有しているにもかかわらず、(S)-1と (S)-2では、CPLスペクトルの符号が反転していた。これらCPLスペクトルの符号の反転について検討するため、円偏光二色性(CD)スペクトルを同様に、chloroform溶液中で測定した。その結果、g-因子約 +0.0002, -0.00096と、CDスペクトルの最長波長の符号にも反転が観測された。これは、同じ絶対配置を有する軸不斉ビナフチル化合物の置換基の種類を変えることにより、ビナフチルの二面体角が変化し、CD及びCPLスペクトルの符号が反転したものだと考えられる。同様に、(S)-1, 2における固体film状態でのCD及びCPLスペクトルの符号の制御にも成功した。以上、軸不斉ビナフチル化合物において、軸斉キラリティーの違いではなく、ビナフチルユニットの二面体角の違いによる左右のCPLの作り分けに成功した。
  • 非古典的概念に基づくレアメタルフリー3次元(3D)ディスプレイ用発光材料の開発
    高橋産業経済研究財団：
    研究期間 : 2013年 
    代表者 : 今井喜胤
  • 産学が連携した研究開発成果の展開 研究成果展開事業 研究成果最適展開支援プログラム(A-STEP) 探索タイプ
    研究期間 : 2011年 -2012年 
    代表者 : 今井 喜胤
     
    本研究課題は、「green chemistry」に基づき、合成的手法の使用をできるだけ回避し、金属(メタル)元素を用いず、非メタル系高輝度有機円偏光発光(CPL)素子及びその開発指針を探索するものである。本研究では、以下のような成果を得ることに成功した。 1. フェニルエチルアミン超分子発光体において、構成分子をビフェニルスルホン酸からビフェニルジスルホン酸にすることにより、超分子中の分子ネットワークが強固になり、蛍光(PL)特性が増加することを見出した。 2. 3成分系超分子有機発光体においても、固体蛍光特性を示すことを見出した。 3. 従来の概念を打ち破り、同じ絶対配置の軸不斉化合物から、軸不斉の角度を制御することにより、円偏光発光(CPL)の符号を制御する事に成功した。
  • 戦略的な研究開発の推進 戦略的創造研究推進事業 ALCA(先端的低炭素化技術開発) 探索ステージ
    研究期間 : 2011年 -2012年 
    代表者 : 今井 喜胤
  • 環境調和型レアメタルフリー3次元(3D)ディスプレイ用有機発光体の創製
    一樹工業技術奨励会：
    研究期間 : 2012年 
    代表者 : 今井喜胤
  • 既存概念を打ち破る光学活性有機発光体の非古典的光学特性制御
    住友電工グループ社会貢献基金：
    研究期間 : 2012年 
    代表者 : 今井喜胤
  • 日本学術振興会：科学研究費助成事業 若手研究(B)
    研究期間 : 2010年 -2011年 
    代表者 : 今井 喜胤
     
    発光には、左巻き、右巻き2種類の円偏光発光(CPL)が存在する。これまで、CPL特性を有する固体超分子有機発光体の開発は、ほとんど行われていない。本研究では、機能の異なる2種類の単分子(発光性カルボン酸分子と光学活性アミン分子)を、弱い相互作用で組み合わせることにより、CPL特性を有する2成分系光学活性超分子有機発光体の開発に成功した。さらに、適切な2構成分子で空孔を形成させ、そこに、別の有機分子を取り込むことにより、より拡張した3成分系超分子有機発光体の開発にも成功している。
  • 日本学術振興会：科学研究費助成事業 若手研究(B)
    研究期間 : 2008年 -2009年 
    代表者 : 今井 喜胤
     
    これまで数多くの発光性分子認識試薬が開発されているが、そのほとんどが溶液中での使用を目的としている。一方、分析時に溶媒を必要としない固体状態で使用できる発光性分子認識試薬が、近年注目を浴びているが、その報告例は少ない。本研究では、発光性カルボン酸分子と、性質の異なるアミン分子を組み合わせることにより、固体状態で使用でき、かつ分子包接特性と発光特性の両方を有する発光性超分子ホストシステムの開発に成功した。
  • 日本学術振興会：科学研究費助成事業 特別研究員奨励費
    研究期間 : 1998年 -1999年 
    代表者 : 今井 喜胤

委員歴

  • 2018年06月 - 現在   高分子学会関西支部   高分子学会関西支部地区幹事
  • - 現在   色材協会関西支部   運営委員
  • - 現在   日本油化学会関西支部   幹事
  • - 現在   日本化学会有機結晶部会   幹事

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