Photochromism of Metal Complexes Composed of Diarylethene Ligands and ZnCl₂

Metal complexes composed of ZnCl2 and bidentate 1,2-bis(2-methyl-5-(4-pyridyl)-3-thienyl)perfluorocyclopentene (1a) and monodentate 1-(2-methyl-5-phenyl-3-thienyl)-2-(2-methyl-5-(4-pyridyl)-3-thienyl)perfluorocyclopentene (2a) photochromic ligands were prepared. X-ray crystallographic analyses showed the formation of a coordination polymer and a discrete 2:1 complex for 1a·ZnCl2 and 2a2·ZnCl2, respectively. While the 2a2·ZnCl2 crystal underwent photochromic reaction in the crystalline state by alternate irradiation with UV and visible light, the 1a·ZnCl2 crystal did not show any photoreactivity. The difference in the photochromic behavior was explained by the difference in the conformation of the diarylethenes in the crystals.