Bulletin of the Chemical Society of Japan

Saigo, Masaki; Shimoda, Yuushi; Ehara, Takumi; Ryu, Tomohiro; Miyata, Kiyoshi; Onda, Ken

doi: 10.1246/bcsj.20210403pmid: N/A

We investigated the correlation between the photophysical properties and detailed excited-state characteristics of a multiple-resonance-type thermally activated delayed fluorescence (TADF) molecule, DABNA-1, using time-resolved infrared vibrational spectroscopy. By comparing the distinctive vibrational spectra in the fingerprint region (1000–1700 cm−1) to the simulated spectra, we found the optimal calculation conditions for density functional theory calculations to retrieve the vibrational spectra. Based on the calculations, the excited-state geometries and molecular orbitals in the lowest excited singlet (S1) and triplet (T1) states, as well as the ground state (S0), were determined. Consequently, we revealed that the similarity between the potential surfaces of T1 and S0 suppressed non-radiative decay and improved the high fluorescence quantum yield via TADF. Furthermore, we calculated the spin-orbit coupling matrix elements (SOCMEs) considering the experimentally confirmed geometries, and revealed that twisting of the main skeleton increases the SOCMEs.

Fujiwara, Masahiro

doi: 10.1246/bcsj.20210421pmid: N/A

Composite catalysts consisting of Fe-Zn oxides and H-ZSM-5 were very effective for the selective production of aromatic hydrocarbons by CO2 hydrogenation. The ratios of aromatic hydrocarbons in all hydrocarbons were beyond 80 C-mol% using these catalysts. When the weight ratio of Fe-Zn oxide and H-ZSM-5 was optimized, the ratio of aromatic hydrocarbons reached more than 90 C-mol%. The Fe-Zn oxides acted as methanol synthesis catalyst in the composite catalyst, forming aromatic hydrocarbons by methanol-to-hydrocarbons reaction over H-ZSM-5. Two aromatic hydrocarbons, p-xylene and 1,2,4-trimethylbenzene, were mainly obtained by the shape selectivity effect of H-ZSM-5. The composite catalyst deactivated by coke formation could be regenerated by air flow treatment.

Tahara, Keishiro; Takezaki, Shun; Ozawa, Yoshiki; Abe, Masaaki

doi: 10.1246/bcsj.20210425pmid: N/A

The use of earth-abundant and inexpensive Co catalysts for carbon-hydrogen (C–H) bond activation has received increasing attention because of the advantages including air stability. Although directing groups have been effectively introduced in substrates to promote C(sp3)–H activation through chelation assistance, there is a lack of basic information about the isolated alkyl-Co complexes containing directing groups as polydentate ligands. In this study, we report the synthesis and characterization of an alkyl-Co(III) complex 2Co, prepared from a N,N′-bis(8-quinolyl)malonamide derivative, the malonyl fragment of which was disubstituted by two ethyl groups. 2Co was straightforwardly obtained from a Co(II) salt without any use of chemical oxidants but in the presence of air, through selective β-C(sp3)–H activation. The combined NMR spectroscopic and X-ray crystal structural analyses revealed that the malonamide substrate was converted into a pentadentate ligand with an N4C set, acquiring a helical configuration around the Co(III) center. The non-innocent ligand properties of 2Co were unambiguously confirmed by UV–vis spectroscopic, electrochemical, and DFT studies. Thermolysis of 2Co enabled C(sp3)–N reductive elimination in the absence of chemical oxidants. The present study provides important insights into the reactivity of alkyl-Co(III) complexes with a defined coordination geometry around the Co center toward designing elaborate C(sp3)–H functionalization systems.

Juji, Shotaro; Oishi, Motoi

doi: 10.1246/bcsj.20210437pmid: N/A

The effect of preservation temperature on the DNA dissociation and functional stability of two types of DNA-modified gold nanoparticles (GNPs) was studied. The cryopreservation of both GNPs for 56 days has fully prevented the DNA dissociation and maintained the toehold-mediated DNA displacement reaction capacity without any aggregation of GNPs.

Matsuhashi, Chihiro; Fujisawa, Hiroki; Ryu, Meguya; Tsujii, Tetsuya; Morikawa, Junko; Oyama, Hironaga; Uekusa, Hidehiro; Maki, Shojiro; Hirano, Takashi

doi: 10.1246/bcsj.20210445pmid: N/A

Adamantylideneadamantane 1,2-dioxetane (Adox), one of the most stable 1,2-dioxetanes, was used to investigate the kinetic properties of its chemiluminescent thermolytic reaction in the crystalline state by monitoring chemiluminescence (CL) in real time. Soon after heating of single crystals at 140 °C, it was found that the thermolytic reactions of Adox in the crystals proceeded with zero-order kinetics for several minutes. During the period showing the zero-order kinetics, CL intensities were dependent on the volumes of crystals, and the inside crystals were maintained in a thermal steady state with a constant thermal diffusivity. After this period, the heated crystals of Adox started to break showing different kinetics. This study indicates that a crystalline-state CL reaction is useful to track its progress in real time for analyzing the kinetics.

Pradipta, Ambara R; Michiba, Hiroyuki; Kubo, Anna; Fujii, Motoko; Tanei, Tomonori; Morimoto, Koji; Shimazu, Kenzo; Tanaka, Katsunori

doi: 10.1246/bcsj.20210387pmid: N/A

Recently, we found that a bulky 2,6-diisopropylphenyl azide is more reactive than a simple phenyl azide toward acrolein. Herein, we conjugated tetramethylrhodamine (TAMRA) to the bulky phenyl azide and utilized it as a second-generation click-to-sense (CTS) probe to analyze cancer by targeting the cellular acrolein. Subsequently, we observed that this second-generation CTS probe could distinguish breast cancer tissues with higher sensitivity than the first-generation CTS probe. Moreover, adding Rh2(OAc)4 to the system promotes the formation of a metal carbenoid intermediate that accelerates the covalent attachment of the probe to an organelle in the cancer cells.

Ochiai, Hikari; Miura, Tomoaki; Ikoma, Tadaaki; Minoura, Mao; Nakano, Haruyuki; Matano, Yoshihiro

doi: 10.1246/bcsj.20220002pmid: N/A

The synthesis, excited state dynamics, and substituent effect on the 1O2-generation efficiency of several copper(II) complexes of 5,15-diazaporphyrin (CuDAPs) bearing peripheral substituents are reported. 10,20-Diaryl-CuDAPs were prepared via a new method consisting of metal-templated cyclization and N-dealkylation as key steps. The effect of the β-substituents on the optical and redox properties of CuDAP was stronger than that of the meso-aryl groups, which can be explained by considering the characteristics of the HOMO and LUMO of the DAP ring. The excited state dynamics and 1O2-generation efficiency of CuDAPs were studied using time-resolved spectroscopic techniques; the electronic effect of the meso-aryl groups on the triplet lifetime and 1O2-generation quantum yield was relatively weak, whereas that of the β-(1-pyrazolyl) groups was appreciable. The analysis of the temperature dependence of phosphorescence spectra of 10,20-bis(2,4,6-trimethylphenyl)-CuDAP allowed the energy gap between the excited trip-quartet and trip-doublet states to be determined. The relatively long triplet lifetimes of CuDAPs show their potential for future application as photosensitizers.

Liu, Mengqin; Cui, Yixiao; Zhang, Yaping; An, Ran; Li, Lin; Park, Soyoung; Sugiyama, Hiroshi; Liang, Xingguo

doi: 10.1246/bcsj.20210400pmid: N/A

Two complementary mini single-stranded DNA circles can hybridize with each other and form Z-B-chimera with a stable left-handed duplex part under low ionic strength conditions. However, we do not know clearly whether this left-handed part has Z-DNA conformation or a new left-handed one. In this study, 2′-OMe-thG, a fluorescent nucleobase, was introduced to detect the formation of Z-DNA conformation at a fixed point of sequence simply by measuring fluorescence change under various conditions. Results showed that the base pair at the modified site formed and the corresponding duplex structure took the Z-conformation in the Z-B-chimera. Z-DNA can form at low ionic strength such as 1.0 mM MgCl2, 75 mM NaCl or 140 mM KCl, which is lower than that of physiological ionic conditions. We also found that formation of Z-DNA becomes more difficult at lower pH (pH <6). This straightforward approach can be used to investigate Z-DNA formation by observing the fluorescence. Formation of Z-B-chimera can be used as a versatile tool to understand Z-DNA characteristics as well as its biological significance.

Sakamoto, Atsuya; Budiutama, Gekko Patria; Takayama, Yoshihiro; Morohashi, Naoya; Hattori, Tetsutaro

doi: 10.1246/bcsj.20210438pmid: N/A

An open-chain carboxylic acid host with a chiral sulfinyl group (4) was synthesized from 3,3′-thiobis[(5-tert-butyl-2-hydroxyphenyl)acetic acid] (2) by oxidation of the epithio linkage with mCPBA, followed by acid-catalyzed monoesterification with propan-1-ol. The monoester was resolved via diastereomeric salt formation using quinidine as a resolving agent. The absolute configuration of (+)-4 was assigned to be (R) by X-ray analysis.

Nakazono, Kazuki; Hosaka, Shuya; Yamada, Yasuhiro; Sato, Satoshi

doi: 10.1246/bcsj.20210447pmid: N/A

The vapor-phase hydrogenation of acetoin (AC) to 2,3-butanediol (2,3-BDO) was investigated over SiO2-supported Ni (Ni/SiO2) catalysts prepared by impregnation assisted with organic additives. Among 14 catalysts with different organic additives, the Ni/SiO2 prepared with citric acid (CA) was found to show the highest activity. The Ni/SiO2 catalyst prepared with CA has a much higher hydrogenation ability for AC and a higher selectivity to 2,3-BDO than typical noble metal catalysts. In addition, it was preferable that the hydrogenation of AC was conducted at a low temperature in the hydrogenation-dehydrogenation equilibrium between AC and 2,3-BDO to provide 2,3-BDO selectively.