X-ray crystallographic study on single-crystalline photochromism of 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene

Single-crystalline photochromism of 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentane was studied by X-ray crystallography. The crystal was irradiated with linearly polarized monochromatic 360 nm light and analyzed with an X-ray diffractometer. The X-Ray crystallographic analysis showed that the conversion from the open-ring to the closed-ring isomers was as much as 8% and that the reaction proceeded in a conrotatory mode. Two sulfur atoms and reactive carbon atoms in the thiophene rings clearly changed their positions. The photogenerated closed-ring isomers completely returned to the initial open-ring isomers in the crystal by irradiation with 650 nm light.