title: New photoswitching unit for magnetic interaction: diarylethene with 2,5-bis(arylethynyl)-3-thienyl group.
abstract: Photoswitching of the intramolecular magnetic interaction was demonstrated using diarylethenes with 2,5-bis(arylethynyl)-4-methyl-3-thienyl side group. Two nitroxide radicals were placed at each end of the 2,5-bis(arylethynyl)-4-methyl-3-thienyl group. Three kinds of aryl groups, 2,5-thienylene, p-phenylene, and m-phenylene groups, were used in the arylethynyl moiety. The diarylethene photoswitching units have an extended pi-conjugated chain on one side of the diarylethene. The photochromic reactivity was dependent on the arylethynyl group. Diarylethenes with m-phenylene group showed an efficient photochromic reactivity. Along with the photochromic reaction the diarylethenes showed photoswitching of an ESR spectrum originating from the change in the magnetic interaction between two unpaired electrons. The open-ring isomer showed stronger exchange interaction than the photogenerated closed-ring isomer. The magnetic interaction between two radicals via the pi-conjugated chain was altered by photocyclization due to the change of the hybrid orbital at the 2-position of the thiophene ring from sp(2) to sp(3).
authors.affiliation: Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Kyushu University, Higashi-ku, Fukuoka 812-8581, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Tanifuji
authors.forename: Masahiro
authors.initials: M
authors.lastname: Irie
authors.forename: Kenji
authors.initials: K
authors.lastname: Matsuda
mesh_terms: D003500:Cyclization; D005030:Ethylenes / Q000138:chemical synthesis / Q000737:chemistry* / Q000528:radiation effects*; D005609:Free Radicals / Q000138:chemical synthesis / Q000737:chemistry; D008280:Magnetics; D015394:Molecular Structure; D010777:Photochemistry; D013876:Thiophenes / Q000138:chemical synthesis / Q000737:chemistry* / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D005030:Ethylenes; D005609:Free Radicals; D013876:Thiophenes