研究者詳細 - 依馬　正

Chiral exciplex dyes showing circularly polarized luminescence: Extension of the excimer chirality rule

Kazuto Takaishi, Sho Murakami, Kazuhiro Iwachido, Tadashi Ema

Chemical Science 12 ( 43 ) 14570 - 14576 2021年11月

掲載種別：研究論文（学術雑誌）

A series of axially chiral binaphthyls and quaternaphthyls possessing two kinds of aromatic fluorophores, such as pyrenyl, perylenyl, and 4-(dimethylamino)phenyl groups, arranged alternately were synthesized by a divergent method. In the excited state, the fluorophores selectively formed a unidirectionally twisted exciplex (excited heterodimer) by a cumulative steric effect and exhibited circularly polarized luminescence (CPL). They are the first examples of a monomolecular exciplex CPL dye. This versatile method for producing exciplex CPL dyes also improved fluorescence intensity, and the CPL properties were not very sensitive to the solvent or to the temperature owing to the conformationally rigid exciplex. This systematic study allowed us to confirm that the excimer chirality rule can be applied to the exciplex dyes: left- and right-handed exciplexes with a twist angle of less than 90° exhibit (-)- and (+)-CPL, respectively. This journal is

DOI： 10.1039/d1sc04403f

Facile Synthesis of Azahelicenes and Diaza[8]circulenes through the Intramolecular Scholl Reaction

Chihiro Maeda, Shuichi Nomoto, Koki Akiyama, Takayuki Tanaka, Tadashi Ema

Chemistry - A European Journal 27 ( 63 ) 15699 - 15705 2021年11月

掲載種別：研究論文（学術雑誌）

Carbazole-based aza[7]helicenes and hetero[9]helicenes were successfully obtained via the intramolecular Scholl reaction of 3,6-bis(biphenyl-2-yl)carbazole congeners, while the reaction of 3,6-bis(naphthylphenyl)-appended carbazole gave a triple helicene via an unexpected simultaneous double aryl rearrangement. DFT calculations suggested that the rearrangement proceeded via an arenium cation intermediate. In addition, the reaction of methoxy-appended substrate gave an azahepta[8]circulene via the concurrent C−C bond formation. These helical dyes showed circularly polarized luminescence. The azahepta[8]circulene was further transformed into deeply saddle-distorted dibenzodiaza[8]circulenes as the first example of its solution-based synthesis and unambiguous structural determination.

DOI： 10.1002/chem.202102269

C-Methylenation of anilines and indoles with CO<inf>2</inf>and hydrosilane using a pentanuclear zinc complex catalyst

Kazuto Takaishi, Hiroyasu Kosugi, Ritsuki Nishimura, Yuya Yamada, Tadashi Ema

Chemical Communications 57 ( 65 ) 8083 - 8086 2021年8月

掲載種別：研究論文（学術雑誌）

The one-stepC-methylenation of anilines and indoles with CO2and phenylsilane was catalyzed by a pentanuclear ZnIIcomplex to give diarylmethanesviageminal C-H and C-C bond formation. It is proposed that the zinc-hydride complex generatedin situis a catalytically active species and that bis(silyl)acetal is a key intermediate. When aniline was used as a substrate, both theC-methylenation andN-methylation proceeded.

DOI： 10.1039/d1cc03675k

Circularly Polarized Luminescence Liquids Based on Siloxybinaphthyls: Best Binaphthyl Dihedral Angle in the Excited State

Kazuto Takaishi, Tomoki Matsumoto, Miyu Kawataka, Tadashi Ema

Angewandte Chemie - International Edition 60 ( 18 ) 9968 - 9972 2021年4月

掲載種別：研究論文（学術雑誌）

A series of axially chiral 1,1′-binaphthyls with trialkylsiloxy (OSiR3) groups were synthesized. Among them, 1 a–c possessing OSiR3 groups at the 7,7′-positions and methyl groups at the 2,2′-positions were liquids at room temperature, and the neat liquids showed circularly polarized luminescence (CPL) (R=Bu; Φfl,liquid=0.21, |glum,liquid|=1.6×10−3). The |glum,liquid| value is the highest of pure liquids. These compounds remained liquid over a broad range of temperatures, down to −50 °C. Time-dependent DFT calculations indicated that in the excited state, the binaphthyls adopt a transoid conformation with a small angle between the electric and magnetic transition dipole moments (θμ,m=77°), which is a key factor in their CPL activity. The best binaphthyl dihedral angle in the excited state is approximately 110°.

DOI： 10.1002/anie.202101226

Synthesis and electronic properties of carbazole-based core-modified diporphyrins showing near infrared absorption

Chihiro Maeda, Takuma Shirakawa, Tadashi Ema

Chemical Communications 56 ( 95 ) 15048 - 15051 2020年12月

掲載種別：研究論文（学術雑誌）

Directly linked carbazole-based core-modified diporphyrin D2 and fused diporphyrin F2 were synthesized. These diporphyrins showed significant electronic interactions and conjugation allowing for redshifted near infrared (NIR) absorption and small HOMO-LUMO gaps as confirmed by NIR absorption spectroscopy, cyclic voltammetry (CV) measurements, and DFT calculations. This journal is

DOI： 10.1039/d0cc06289h

Aggregation-Induced Circularly Polarized Luminescence from Boron Complexes with a Carbazolyl Schiff Base

Chihiro Maeda, Shuichi Nomoto, Kazuto Takaishi, Tadashi Ema

Chemistry - A European Journal 26 ( 57 ) 13016 - 13021 2020年10月

掲載種別：研究論文（学術雑誌）

A variety of carbazolyl-appended Schiff bases were readily synthesized from 1-formylcarbazoles and aniline derivatives. Boron complexation of the resulting ligands allowed for facile preparation of new carbazole-based BODIPY analogues showing solid-state fluorescence. Furthermore, some dyes were converted into chiral compounds through the Et2AlCl-mediated incorporation of a binaphthyl unit. The chiral dyes showed aggregation-induced fluorescence and circularly polarized luminescence (CPL) with the ΦF and glum of up to 0.22 and −3.5×10−3, respectively, in the solid state. The solid-state fluorescence and CPL were well characterized by the crystal packing analyses and DFT calculations.

DOI： 10.1002/chem.202001463

Tetrameric and Hexameric Porphyrin Nanorings: Template Synthesis and Photophysical Properties

Chihiro Maeda, Shoki Toyama, Naoki Okada, Kazuto Takaishi, Seongsoo Kang, Dongho Kim, Tadashi Ema

Journal of the American Chemical Society 142 ( 37 ) 15661 - 15666 2020年9月

掲載種別：研究論文（学術雑誌）

Hexameric and tetrameric porphyrin nanorings, Z6T6 and Z4T4, were synthesized in 53% and 14% yields, respectively, by the Sonogashira-type self-oligomerization of porphyrin monomer 1 using hexadentate template T6 and tetrapyridylporphyrin template T4. Template-free nanorings Z6 and Z4 were also prepared. The femtosecond transient absorption measurements revealed fast excitation energy hopping (EEH) along these nanorings with hopping rates of 2-5 ps. Treatment of Z6 with chiral template CT6 gave Z6CT6 showing circular dichroism (CD) and circularly polarized luminescence (CPL) in the absorption and fluorescence regions of Z6, respectively, which indicates chirality transfer from CT6 to Z6.

DOI： 10.1021/jacs.0c07707

Aluminum porphyrins with quaternary ammonium halides as catalysts for copolymerization of cyclohexene oxide and CO<inf>2</inf>: metal-ligand cooperative catalysis

Jingyuan Deng, Manussada Ratanasak, Yuma Sako, Hideki Tokuda, Chihiro Maeda, Jun Ya Hasegawa, Kyoko Nozaki, Tadashi Ema

Chemical Science 11 ( 22 ) 5669 - 5675 2020年6月

掲載種別：研究論文（学術雑誌）

Bifunctional AlIIIporphyrins with quaternary ammonium halides,2-Cland2-Br, worked as excellent catalysts for the copolymerization of cyclohexene oxide (CHO) and CO2at 120 °C. Turnover frequency (TOF) and turnover number (TON) reached 10 000 h−1and 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 MgIIand ZnIIcounterparts,3-Cland4-Cl, as well as a binary catalyst system,1-Clwith 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−1K−1, and ΔG‡= 21.6 kcal mol−1at 80 °C. Comparative DFT calculations on two model catalysts, AlIIIcomplex2′and MgIIcomplex3′, allowed us to extract key factors in the catalytic behavior of the bifunctional AlIIIcatalyst. 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 asTS3b(ΔH‡= 13.3 kcal mol−1, ΔS‡= −3.1 cal mol−1K−1, and ΔG‡= 14.4 kcal mol−1at 80 °C).

DOI： 10.1039/d0sc01609h

Synthesis of silyl formates, formamides, and aldehydesviasolvent-free organocatalytic hydrosilylation of CO<inf>2</inf>

Takumi Murata, Mahoko Hiyoshi, Manussada Ratanasak, Jun Ya Hasegawa, Tadashi Ema

Chemical Communications 56 ( 43 ) 5783 - 5786 2020年5月

掲載種別：研究論文（学術雑誌）

Carbon dioxide (CO2) was used as a C1 source to prepare silyl formates, formamides, and aldehydes. Tetrabutylammonium acetate (TBAA) catalyzed the solvent-freeN-formylation of amines with CO2and hydrosilane to give formamides including Weinreb formamide, Me(MeO)NCHO, which was successively converted into aldehydes by one-pot reactions with Grignard reagents.

DOI： 10.1039/d0cc01371d

Azahelicene-Fused BODIPY Analogues Showing Circularly Polarized Luminescence

Chihiro Maeda, Keiji Nagahata, Takuma Shirakawa, Tadashi Ema

Angewandte Chemie - International Edition 59 ( 20 ) 7813 - 7817 2020年5月

掲載種別：研究論文（学術雑誌）

Helical carbazole-based BODIPY analogues were readily synthesized via aza[7]helicenes. The structures of azahelicene-incorporated BF2 dyes were elucidated by x-ray diffraction analysis. DFT calculations revealed that the π-conjugated system expanded from the helicene moiety to the BODIPY framework. The azahelicene-fused boron complexes showed the Cotton effects and the circularly polarized luminescence (CPL) in the visible region. Furthermore, an axially chiral binaphthyl group was attached to the helically chiral dyes, which enhanced the chiroptical properties.

DOI： 10.1002/anie.202001186

Minimization of Amounts of Catalyst and Solvent in NHC-Catalyzed Benzoin Reactions of Solid Aldehydes: Mechanistic Consideration of Solid-to-Solid Conversion and Total Synthesis of Isodarparvinol B

Kenta Iwai, Masakazu Ono, Yoshiko Nanjo, Tadashi Ema

ACS Omega 5 ( 17 ) 10207 - 10216 2020年5月

掲載種別：研究論文（学術雑誌）

Attempts were made to minimize the amounts of catalyst and solvent in the NHC-catalyzed benzoin reactions of solid aldehydes. In some case, solid-to-solid conversions proceeded in the solvent-free NHC-catalyzed benzoin reactions. Even if a mixture of the substrate, N-heterocyclic carbene (NHC) precursor, and inorganic base was initially a powdery solid, the reaction did proceed at reaction temperature lower than the melting points of each compound. The solid mixture partially melted or became a slurry or suspension in the meantime. We call this solid/liquid mixture a semisolid state. The reaction giving an optically active product was faster than that giving a racemic mixture of the same product. Melting-point depression was observed for a series of mixtures of the substrate and product in different substrate/product ratios. Solvent-free solid-to-solid conversions were accelerated by the formation of a semisolid state resulting from the melting-point depression of the solid substrate accompanied by the product formation. In the case of solid substrates with high melting points, melting-point depression was useless, and the addition of a small amount of solvent was needed. The first total synthesis of isodarparvinol B was achieved via the NHC-catalyzed intramolecular benzoin reaction using a small amount of solvent as an additive.

DOI： 10.1021/acsomega.0c01141

Synthesis and Chiroptical Properties of Chiral Carbazole-Based BODIPYs

Chihiro Maeda, Keita Suka, Keiji Nagahata, Kazuto Takaishi, Tadashi Ema

Chemistry - A European Journal 26 ( 19 ) 4261 - 4268 2020年4月

掲載種別：研究論文（学術雑誌）

A series of carbazole-based boron dipyrromethenes (BODIPYs) 2 a–g bearing binaphthyl units have been synthesized by the Et2AlCl-mediated reaction of the corresponding BODIPY difluorides 1 a–g with 1,1′-binaphthalene-2,2′-diol. Substituents such as halogen, nitrile, and amino groups were tolerated under the reaction conditions, and the reaction of the phenylethynyl-substituted 1 h gave (R,R)-3 h bearing two binaphthyl units. The chiroptical properties of these dyes with different substituents were investigated by UV/Vis, CD, fluorescence, and circularly polarized luminescence (CPL) spectroscopy. The CD spectra showed Cotton effects in the absorption region of the BODIPY moieties. In addition, they showed CPL both in solution and in the solid state. Interestingly, several dyes recorded higher glum values in the solid state, probably due to intermolecular interactions. Because (R,R)-3 h recorded relatively low glum values, the diastereomer (R,S)-3 h was prepared. The (R,S) diastereomer showed intense CPL, which suggests a synergetic effect of the two binaphthyl groups. Finally, chiral carbazole-based BODIPY dimers have been synthesized for the first time and their chiroptical properties were investigated. They showed redshifted fluorescence and CPL, which reached the near-IR (NIR) region in the solid state.

DOI： 10.1002/chem.201904954

Solvent-Induced Sign Inversion of Circularly Polarized Luminescence: Control of Excimer Chirality by Hydrogen Bonding

Kazuto Takaishi, Kazuhiro Iwachido, Tadashi Ema

Journal of the American Chemical Society 142 ( 4 ) 1774 - 1779 2020年1月

掲載種別：研究論文（学術雑誌）

A series of pyrenes sandwiched by axially chiral 1,1′-binaphthyls were synthesized. Among them, (R,R)-3 possessing 2-hydroxy-3,3′-dimethylbinaphthyls exhibited solvent-dependent inversion of the sign of circularly polarized luminescence (CPL) without a change in emission wavelength. The (-)- and (+)-CPL were detected in nonpolar and polar solvents, respectively, with glum values of -0.012 and +0.012. This switching property originates from the inversion of excimer chirality caused by the presence or absence of intermolecular hydrogen bonds in the excited state. The CPL intensity was also changed by variation of the temperature and concentration.

DOI： 10.1021/jacs.9b13184