研究者詳細 - 依馬　正

B,N-Embedded Helical Nanographenes Showing an Ion-Triggered Chiroptical Switching Function 査読

Chihiro Maeda, Sayaka Michishita, Issa Yasutomo, Tadashi Ema

Angewandte Chemie - International Edition 2025年

担当区分：最終著者,　責任著者掲載種別：研究論文（学術雑誌）

Intramolecular oxidative aromatic coupling of 3,6-bis(m-terphenyl-2’-yl)carbazole provided a bis(m-terphenyl)-fused carbazole, while that of 3,6-bis(m-terphenyl-2’-yl)-1,8-diphenylcarbazole afforded a bis(quaterphenyl)-fused carbazole. Borylation of the latter furnished a B,N-embedded helical nanographene binding a fluoride anion via a structural change from the three-coordinate boron to the four-coordinate boron. The anionic charge derived from the fluoride anion is stabilized over the expanded π-framework, which leads to the high binding constant (Ka) of 1×105 M−1. The four-coordinate boron species was converted back to the parent three-coordinate boron species with Ag+, and the chiroptical switch between the three-coordinate boron and four-coordinate boron species has been achieved via the ion recognition with the change in the color and glum values.

DOI： 10.1002/anie.202418546

Terpolymerization reactions of epoxides, CO<inf>2</inf>, and the third monomers toward sustainable CO<inf>2</inf>-based polymers with controllable chemical and physical properties 招待査読

Koichi Nakaoka, Tadashi Ema

Chemical Communications 61 ( 1 ) 46 - 60 2025年

担当区分：最終著者,　責任著者掲載種別：研究論文（学術雑誌）

Carbon dioxide (CO2) serves as a cheap, abundant, and renewable C1 building block for the synthesis of organic compounds and polymers. Selective and efficient CO2 fixation processes are still challenging because of the kinetic and thermodynamic stability of CO2. Among various CO2 fixation processes, the ring-opening copolymerization (ROCOP) of epoxides and CO2 gives aliphatic polycarbonates with high atom economy, although the chemical and physical properties of the resulting polycarbonates are not necessarily satisfactory. Introducing the third monomers into this ROCOP system provides new terpolymers, and the thermal, optical, mechanical or degradation properties can be added or tuned by incorporating new polymer backbones derived from the third monomers at the expense of the CO2 content. Here we review the terpolymerization reactions of epoxides, CO2, and the third monomers such as cyclic anhydrides, lactones, lactides, heteroallenes, and olefins. The development of catalysts and the control of the polymer structures are described together with the chemical and physical properties of the resulting polymers.

DOI： 10.1039/d4cc04615c

Synthesis and Postfunctionalization of Acrylate-Appended Poly(cyclohexene carbonate)s: Modulation of Properties of CO<inf>2</inf>-Based Polymers 査読

Chihiro Maeda, Hina Inoue, Tadashi Ema

Macromolecules 58 ( 3 ) 1571 - 1577 2025年

担当区分：最終著者,　責任著者掲載種別：研究論文（学術雑誌）

Functional CO2-based polycarbonates are expected to be sustainable materials. Herein, a bifunctional aluminum porphyrin catalyzed the terpolymerization of cyclohexene oxide (CHO), acrylate-appended CHO, and CO2 to provide poly(cyclohexene carbonate)s (PCHCs) with acrylate groups. Postfunctionalization of PCHCs via Michael addition or Heck reaction enabled the incorporation of thiol, amine, and aromatics into PCHCs with high selectivity and efficiency. PCHCs with the flexible long alkyl chains showed a glass-transition temperature (Tg) of down to 52 °C, which was much lower than that of PCHC (127 °C). In sharp contrast, PCHCs with rigid pyrenyl groups showed Tg values of up to 152 °C and fluorescence emission. Thus, a wide range of polymers were obtained by robust and sustainable synthetic methods, and the functional groups modulated the properties of the CO2-based polycarbonates.

DOI： 10.1021/acs.macromol.4c02881

Recent development of azahelicenes showing circularly polarized luminescence

Chihiro Maeda, Tadashi Ema

Chemical Communications 61 ( 25 ) 4757 - 4773 2025年

Terpolymerization of Propylene Oxide, CO<inf>2</inf>, and p-Toluenesulfonyl Isocyanate for the Synthesis of Poly(urethane-carbonate): p-Toluenesulfonyl Isocyanate Acts as a Backbiting Suppressor

Satoshi Muranaka, Io Yamamoto, Tadashi Ema

ACS Applied Polymer Materials 6 ( 24 ) 15366 - 15374 2024年12月

掲載種別：研究論文（学術雑誌）

Terpolymerization of propylene oxide, CO2, and p-toluenesulfonyl isocyanate (TsNCO) was catalyzed by bifunctional AlIII porphyrin catalysts to afford polyurethane-poly(propylene carbonate), PU-PPC, with high CO2 contents of up to 39 wt %. TsNCO acted as a backbiting suppressor at the initial stage of the terpolymerization, contributing to the selective formation of PU-PPC. In contrast to the high electrophilicity of TsNCO, the carbamate anion generated by the reaction of TsNCO with the alkoxide intermediate has modest nucleophilicity owing to the tosyl group, which allows for the smooth formation of the PU units and the subsequent elongation of the PPC units on the catalyst to selectively produce PU-PPC. Terpolymers having the PU and PPC units in a 1:1 ratio had glass transition temperature (Tg) of 86-104 °C, while those with higher PPC contents had Tg values of 39-40 °C. Block copolymer PU-b-PPC, which was synthesized in a one-pot two-step manner, showed two Tg values at 45 and 76 °C. Pure PU showed 10% weight loss temperature (Td10) at 230 °C, while PU-PPC with high PPC contents showed Td10 at 236-254 °C. They were degradable upon UV light irradiation and heat treatment, while they were resistant to acid. The terpolymerization strategy using TsNCO as a backbiting suppressor potentially enables one to create CO2-based polymers such as plastics and elastomers with degradability controlled by UV light or heat.

DOI： 10.1021/acsapm.4c03431

Cyclic Azahelicene Dimers Showing Bright Circularly Polarized Luminescence and Selective Fluoride Recognition 査読

Chihiro Maeda, Issa Yasutomo, Tadashi Ema

Angewandte Chemie - International Edition 63 ( 30 ) e202404149 2024年7月

担当区分：最終著者,　責任著者掲載種別：研究論文（学術雑誌）

Although helicenes are promising molecules, the synthetic difficulty and tediousness have often been problems, and only small amounts of optically pure helicenes have been obtained by using chiral HPLC in most cases. Herein, aza[7]helicenes or closed-aza[7]helicenes with (1R)-menthyl substituents were selectively synthesized via the intramolecular Scholl reaction, and the diastereomeric pairs were separated by silica gel column chromatography. The optically pure helicenes were further transformed into the corresponding cyclic dimers, and the chiroptical properties were investigated. The rigid π-frameworks of the dimers led to the high molar extinction coefficients and fluorescence quantum yields, while the twisted helicene moieties induced clear Cotton effects and CPL in the visible region, and the high CPL brightness (BCPL) was achieved. Furthermore, the cyclic dimers were found to have the macrocyclic cavity with the two NH groups suitable for the selective binding of a fluoride anion, which induced significantly redshifted fluorescence and CPL in the red region.

DOI： 10.1002/anie.202404149

Temperature-Induced Sign Inversion of Circularly Polarized Luminescence of Binaphthyl-Bridged Tetrathiapyrenophanes 査読

Kazuto Takaishi, Fumiya Yoshinami, Yoshihiro Sato, Tadashi Ema

Chemistry - A European Journal 30 ( 32 ) e202400866 2024年6月

担当区分：最終著者,　責任著者掲載種別：研究論文（学術雑誌）

D2-symmetric (R)-binaphthyl-bridged pyrenophanes containing thioether bonds were synthesized. The pyrenophanes exhibited the temperature-induced sign inversion of circularly polarized luminescence (CPL) while maintaining the emission wavelength and reversibility. The Δglum value reached 0.02, and the FL quenching by heat was negligible. The sign inversion of CPL originates from the inversion of intramolecular excimer chirality associated with excitation dynamics. The two pyrenes form a kinetically trapped left-handed twist excimer at low temperatures, while they form a thermodynamically favored right-handed twist excimer at high temperatures. The thioether linkers can impart flexibility suitable for the inversion of chirality of the excimers.

DOI： 10.1002/chem.202400866

Skeletal Formation of Carbocycles with CO<inf>2</inf>: Selective Synthesis of Indolo[3,2-b]carbazoles or Cyclophanes from Indoles, CO<inf>2</inf>, and Phenylsilane 査読

Sha Li, Shoko Nakahara, Taishin Adachi, Takumi Murata, Kazuto Takaishi, Tadashi Ema

Journal of the American Chemical Society 146 ( 22 ) 14935 - 14941 2024年6月

担当区分：最終著者,　責任著者掲載種別：研究論文（学術雑誌）

The catalytic reactions of indoles with CO2 and phenylsilane afforded indolo[3,2-b]carbazoles, where the fused benzene ring was constructed by forming two C-H bonds and four C-C bonds with two CO2 molecules via deoxygenative conversions. Nine-membered cyclophanes made up of three indoles and three CO2 molecules were also obtained, where the cyclophane framework was constructed by forming six C-H bonds and six C-C bonds. These multicomponent cascade reactions giving completely different carbocycles were switched simply by choosing the solvent, acetonitrile or ethyl acetate.

DOI： 10.1021/jacs.4c04097

Synthesis of hydroxy acids via the light-driven carboxylation of epoxides with CO<inf>2</inf> 査読

Chihiro Maeda, Ren Kumemoto, Rio Tanaka, Tadashi Ema

Chemistry Letters 53 ( 5 ) upae086 2024年5月

担当区分：最終著者,　責任著者掲載種別：研究論文（学術雑誌）

Light-driven ring-opening carboxylation of epoxides with CO2 provided β-hydroxy acids via sequential single electron transfer (SET), followed by reaction with CO2. This reaction condition was applicable to aryl epoxides and oxetanes with (hetero)polycyclic aromatics to give the corresponding β- and γ-hydroxy acids, respectively, with high chemoselectivity.

DOI： 10.1093/chemle/upae086

Terpolymerizations of cyclohexene oxide, CO<inf>2</inf>, and isocyanates or isothiocyanates for the synthesis of poly(carbonate-urethane)s or poly(carbonate-thioimidocarbonate)s 査読

Koichi Nakaoka, Satoshi Muranaka, Io Yamamoto, Tadashi Ema

Polymer Chemistry 15 ( 8 ) 707 - 713 2024年1月

担当区分：最終著者,　責任著者掲載種別：研究論文（学術雑誌）

Terpolymerization of cyclohexene oxide (CHO), CO2, and aryl isothiocyanates produced poly(carbonate-thioimidocarbonate)s with gradient character, while that of CHO, CO2, and aryl isocyanates furnished poly(carbonate-urethane)s with random sequences. The former underwent partial degradation upon acid treatment or UV irradiation, while the latter was stable under the same conditions.

DOI： 10.1039/d3py01165h

Selective Conversions of CO<inf>2</inf> into Value-Added Chemicals via Cooperative Catalysis Using Multifunctional Catalysts 査読

Tadashi Ema

Bulletin of the Chemical Society of Japan 96 ( 7 ) 693 - 701 2023年7月

担当区分：筆頭著者,　責任著者掲載種別：研究論文（学術雑誌）

Carbon dioxide (CO2) is not only a greenhouse gas but also a renewable carbon source for organic synthesis. Here we have summarized our studies on the conversions of CO2 into value-added chemicals via cooperative catalysis using multifunctional catalysts. For example, bifunctional metalloporphyrin catalysts with quaternary ammonium halides were developed for the selective synthesis of cyclic carbonates or polycarbonates from epoxides and CO2. Bifunctional MgII and ZnII porphyrins showed high catalytic activity for the synthesis of cyclic carbonates, while bifunctional AlIII porphyrins catalyzed the copolymerization of cyclohexene oxide and CO2 to give poly(cyclohexene carbonate). The high catalytic activities resulted from the cooperative action of the central metal ion and the quaternary ammonium salts. Chiral catalysts for the kinetic resolution of terminal or internal epoxides with CO2 were also developed. In addition, macrocyclic multinuclear metal complex Zn5L3, which was synthesized by the self-assembly of Zn(OAc)2 and a BINOL derivative (L), catalyzed the reduction of CO2 with phenylsilane to produce various useful synthetic intermediates and organic compounds.

DOI： 10.1246/bcsj.20230099

Synthesis and Photophysical Properties of Dihetero[8]circulenes 査読

Chihiro Maeda, Koki Akiyama, Tadashi Ema

Organic Letters 25 ( 21 ) 3932 - 3935 2023年6月

One‐Pot Synthesis of Aldehydes or Alcohols from CO 2 via Formamides or Silyl Formates 査読

Fan Yang, Yuta Saiki, Koichi Nakaoka, Tadashi Ema

Advanced Synthesis & Catalysis 365 ( 6 ) 877 - 883 2023年3月

One-Pot Synthesis of Dihydropyrans via CO2 Reduction and Domino Knoevenagel/oxa-Diels–Alder Reactions 査読

Kazuto Takaishi, Ritsuki Nishimura, Yuha Toda, Hajime Morishita, Tadashi Ema

Organic Letters 25 ( 9 ) 1370 - 1374 2023年3月

Circularly polarized luminescence from porphyrin-containing (supra)molecular systems 招待査読

Chihiro Maeda, Issa Yasutomo, Kazuto Takaishi, Tadashi Ema

Journal of Porphyrins and Phthalocyanines 27 ( 07n10 ) 903 - 911 2023年2月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：World Scientific Pub Co Pte Ltd

Functional dyes showing circularly polarized luminescence (CPL) have attracted considerable attention. Porphyrins and porphyrinoids have characteristic properties useful for the development of CPL materials, although the examples of CPL-active porphyrins and porphyrinoids are still limited. Here we have summarized recent progress in CPL-active systems containing porphyrins or phthalocyanines, which are classified into the following four categories: (i) porphyrins with chiral sources; (ii) axially chiral porphyrin dimers; (iii) self-assembled porphyrins; (iv) porphyrin-sensitized CPL dyes.

DOI： 10.1142/s108842462330001x

Circularly polarized luminescence in molecular recognition systems: Recent achievements 招待査読

Kazuto Takaishi, Chihiro Maeda, Tadashi Ema

Chirality 35 ( 2 ) 92 - 103 2023年2月

担当区分：最終著者,　責任著者掲載種別：研究論文（学術雑誌）出版者・発行元：Wiley

Abstract

Circularly polarized luminescence (CPL) dyes are recognized to be new generation materials and have been actively developed. Molecular recognition systems provide nice approaches to novel CPL materials, such as stimuli‐responsive switches and chemical sensing materials. CPL may be induced simply by mixing chiral or achiral, luminescent or nonluminescent host and guest; there are several combinations. Molecular recognition can potentially save time and effort to construct well‐ordered chiral structures with noncovalent attractive interactions as compared with the multi‐step synthesis of covalently bonded dyes. It is a challenging subject to engage molecular recognition events with CPL, and it is important and interesting to see how it is achieved. In fact, simple molecular recognition systems can even enable the fine adjustment of CPL performance and detailed conformational/configurational analysis of the excited state. Here we overview the recent achievements of simple host–guest complexes capable of exhibiting CPL, summarizing concisely the host/guest structures, CPL intensities, and characteristics.

DOI： 10.1002/chir.23522