American Chemical Society (ACS) Acta Medica Okayama 0024-9297 58 3 2025 Synthesis and Postfunctionalization of Acrylate-Appended Poly(cyclohexene carbonate)s: Modulation of Properties of CO2-Based Polymers 1571 1577 EN Chihiro Maeda Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Hina Inoue Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Tadashi Ema Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University 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. No potential conflict of interest relevant to this article was reported.

Royal Society of Chemistry (RSC) Acta Medica Okayama 1359-7345 61 25 2025 Recent development of azahelicenes showing circularly polarized luminescence 4757 4773 EN Chihiro Maeda Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Tadashi Ema Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Recently, a variety of circularly polarized luminescence (CPL) dyes have been developed as next-generation chiroptical materials. Helicenes, ortho-fused aromatics, have been recognized as some of the most promising CPL dyes. Although typical carbohelicenes show CPL, weak fluorescence is often emitted in the blue region. In contrast, heteroatom-embedded helicenes (heterohelicenes) can show intense fluorescence and CPL in the visible region because heteroatoms alter the electronic states of helicene frameworks. Among various heterohelicenes, nitrogen-embedded helicenes (azahelicenes) have unique features such as facile functionalization and sensitive responses to acid/base or metal ions. Furthermore, polycyclic aromatic hydrocarbons (PAHs) containing azaborine units have been recognized as excellent luminescent materials, and the helical derivatives, B,N-embedded helicenes, have been rapidly growing recently. In this feature article, we review and summarize the synthesis and chiroptical properties of azahelicenes, which are classified into imine-type and amine-type azahelicenes and B,N-embedded helicenes. CPL switching systems of azahelicenes are also reviewed. No potential conflict of interest relevant to this article was reported.

Wiley Acta Medica Okayama 1433-7851 64 8 2025 B,N‐Embedded Helical Nanographenes Showing an Ion‐Triggered Chiroptical Switching Function e202418546 EN Chihiro Maeda Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Sayaka Michishita Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Issa Yasutomo Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Tadashi Ema Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University 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. No potential conflict of interest relevant to this article was reported.

Royal Society of Chemistry (RSC) Acta Medica Okayama 1759-9954 14 37 2023 Catalytic synthesis and physical properties of CO2-based cross-linked poly(cyclohexene carbonate)s 4338 4343 EN Chihiro Maeda Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Kenta Kawabata Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Kaito Niki Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Yuma Sako Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Takumi Okihara Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Tadashi Ema Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Bifunctional aluminum porphyrins (0.001 mol%) catalyzed the terpolymerization of cyclohexene oxide (CHO), bis(CHO), and CO2 to give cross-linked polycarbonates (CLPs) under solvent-free conditions. A small amount of bis(CHO) acted as a cross-linking agent, and the use of only 0.1 mol% bis(CHO) to CHO produced polymers of quite large sizes. The thermal and mechanical properties of CLPs could be altered by changing the structure and amount of bis(CHO), and the CLPs showed improved thermal stability and tensile strength as compared to linear poly(cyclohexene carbonate)s (PCHCs). The degradation of the CLPs was also investigated, and the selective cleavage of the cross-links was achieved by UV light irradiation to give linear PCHCs. The present study disclosed the potentials of cross-linking terpolymerization for the preparation of various CLPs with a constant CO2 content (31 wt%). No potential conflict of interest relevant to this article was reported.

Royal Society of Chemistry Acta Medica Okayama 2041-6520 11 22 2020 Aluminum porphyrins with quaternary ammonium halides as catalysts for copolymerization of cyclohexene oxide and CO2: metal–ligand cooperative catalysis 5669 5675 EN Jingyuan Deng Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo Manussada Ratanasak Institute for Catalysis, Hokkaido University Yuma Sako Graduate School of Natural Science and Technology, Okayama University Hideki Tokuda Graduate School of Natural Science and Technology, Okayama University Chihiro Maeda Graduate School of Natural Science and Technology, Okayama University Jun-ya Hasegawa Institute for Catalysis, Hokkaido University Kyoko Nozaki Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo Tadashi Ema Graduate School of Natural Science and Technology, Okayama University Bifunctional AlIII porphyrins with quaternary ammonium halides, 2-Cl and 2-Br, worked as excellent catalysts for the copolymerization of cyclohexene oxide (CHO) and CO2 at 120 °C. Turnover frequency (TOF) and turnover number (TON) reached 10 000 h－1 and 55 000, respectively, and poly(cyclohexene carbonate) (PCHC) with molecular weight of up to 281 000 was obtained with a catalyst loading of 0.001 mol%. In contrast, bifunctional MgII and ZnII counterparts, 3-Cl and 4-Cl, as well as a binary catalyst system, 1-Cl with bis(triphenylphosphine)iminium chloride (PPNCl), showed poor catalytic performances. Kinetic studies revealed that the reaction rate was first-order in [CHO] and [2-Br] and zero-order in [CO2], and the activation parameters were determined: ΔH‡ = 12.4 kcal mol－1, ΔS‡ = －26.1 cal mol－1 K－1, and ΔG‡ = 21.6 kcal mol－1 at 80 °C. Comparative DFT calculations on two model catalysts, AlIII complex 2′ and MgII complex 3′, allowed us to extract key factors in the catalytic behavior of the bifunctional AlIII catalyst. The high polymerization activity and carbonate-linkage selectivity originate from the cooperative actions of the metal center and the quaternary ammonium cation, both of which facilitate the epoxide-ring opening by the carbonate anion to form the carbonate linkage in the key transition state such as TS3b (ΔH‡ = 13.3 kcal mol－1, ΔS‡ = －3.1 cal mol－1 K－1, and ΔG‡ = 14.4 kcal mol－1 at 80 °C). No potential conflict of interest relevant to this article was reported.