Photochromism of bis(2-alkyl-1-benzothiophen-3-yl)perfluorocyclopentene derivatives

Photochromism of bis(2-n-alkyl-1-benzothiophen-3-yl)perfluorocyclopentene derivatives has been studied in solution as well as in the single crystalline phase. Introduction of the long alkyl chains at 2-positions of bis(1-benzothiophen-3-yl)perfluorocyclopentene was found to increase the cyclization quantum yield and induce bathochromic shifts of the absorption spectra of the closed-ring isomers. The derivatives with ethyl, propyl, and butyl substituents at the 2-positions exhibit photochromism even in the single crystalline phase.