title: Multistate photochromism of 1-phenylnaphthalene-bridged imidazole dimer that has three colorless isomers and two colored isomers.
abstract: A new type of the bridged imidazole dimer with a 1-phenylnaphthalene moiety that bridges two diphenylimidazole units at the 2- and 2'-positions was synthesized and the photochemical and thermochemical properties were investigated. This molecule shows unique multistate photochromism, in which the stable colorless 1,2'-isomers A and B photochemically isomerize to the colorless 2,2'-isomer through the short-lived biradical with a half-life of 180 ns at 25 °C. The 2,2'-isomer thermally returns to the 1,2'-isomers A and B through the colored isomer at elevated temperatures. The 1,2'-isomers A and B, the 2,2'-isomer, and the colored isomer were isolated, and their molecular structures were determined by X-ray crystallographic analysis. These isomers are stable at room temperature and can be almost fully converted to the 2,2'-isomer by light irradiation. This study serves the useful strategy for the molecular design of a new type of negative photochromic molecules applicable to switch molecular properties by visible light irradiation.
authors.affiliation: Department of Chemistry, School of Science and Engineering, Aoyama Gakuin University , 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Yamaguchi
authors.forename: Sayaka
authors.initials: S
authors.lastname: Hatano
authors.forename: Jiro
authors.initials: J
authors.lastname: Abe