title: Characterization of cationic diarylethene by electron spin resonance and absorption spectra-ratio of open/closed-ring isomers.
abstract: Electrochemical cyclization/cycloreversion reactions of a diarylethene, 1,2-bis(3-methyl-2-thienyl)perfluorocyclopentene, are examined experimentally by electron spin resonance (ESR) and absorption spectra. To understand the ESR spectrum, the hyperfine coupling constants are calculated by the density functional theory (DFT) with the B3LYP exchange-correlation functional. The averaged values of the hyperfine coupling constants are approximated by imposing the C(2) symmetry on the structure of the diarylethene. We found that the spectral width of the ESR is significantly different between the open- and closed-ring isomers. This is due to the difference in the pi-conjugation between two isomers. The ESR spectral width analysis could, thus, be used to identify the isomerization of the radical species, which involve the change of the pi-conjugation. The experimentally observed spectrum is found to be the mixture of the open- and closed-ring isomers of the diarylethene. The excitation energies of the cationic diarylethenes are further identified by the SAC-CI calculations.
authors.affiliation: Mitsubishi Chemical Group, Science and Technology Research Center, Inc. and CREST-JST, 1000 Kamoshida-cho, Aoba-ku, Yokohama, 227-8502 Japan. yokojima@rc.m-kagaku.cp.jp
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yokojima
authors.forename: Kenji
authors.initials: K
authors.lastname: Matsuda
authors.forename: Masahiro
authors.initials: M
authors.lastname: Irie
authors.forename: Akinori
authors.initials: A
authors.lastname: Murakami
authors.forename: Takao
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Nakamura
mesh_terms: D002412:Cations; D003500:Cyclization; D003517:Cyclopentanes / Q000737:chemistry*; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D005030:Ethylenes / Q000737:chemistry*; D007536:Isomerism; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010777:Photochemistry; D013054:Spectrophotometry, Atomic; D014466:Ultraviolet Rays
chemical_list: D002412:Cations; D003517:Cyclopentanes; D005030:Ethylenes