Mechanism of Photochromic Transformations and Photodegradation of an Asymmetrical 2,3-Diarylcyclopentenone
The mechanistic study of photochromism and photodegradation of an asymmetrical thiophene-containg 2,3–diarylcyclopent-2-en-1-one bearing a thiophene and a benzothiophene rings (3-(2,5-dimethiltiofen-3-il)-2-(2-methil-1-benzyltiofen-3-il)cyclopent-2-en-1-on, compound 1) has been performed using stationary photolysis, nanosecond laser flash photolysis and time-resolved luminescence. Photochromic properties of 1 are typical for diarylethenes involving light-induced transitions between open form 1A and closed form 1B. Photodegradation occurs via two mechanisms. The first oxygen-free mechanism is the formal 1,2-dyotropic rearrangement. The second oxygen-dependent mechanism includes excitation of 1A to the triplet state, its quenching by dissolved oxygen and oxidation of the initial compound by singlet oxygen.