Fatigue Mechanism of Photochromic 1,2-Bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene

Abstract
The fatigue mechanism of photochromic 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene was studied in hexane solution. Upon irradiation with ultraviolet light, two kinds of by-products were produced in addition to normal photochromic reactions. The major by-product was isolated by HPLC, and was characterized by 1H NMR and absorption spectroscopies and X-ray crystallographic analysis. A minor by-product was also isolated and analyzed with a mass spectrometer. Based on the molecular structural analysis a possible photofatigue mechanism of the dithienylethene was proposed.