a series of diarylethene compounds with a thiophene bridging unit have been synthesized to investigate the relationship between molecular structure and photochromic properties. In particular, the fluorescence properties related to compound 1 were investigated. The results showed that a six-membered ring carrying an electron-donating sulfur atom and an electron-withdrawing carbonyl group is necessary to form a "push-pull" system for the fluorescence of 1.

A series of diarylthiophenes containing sulfone groups were synthesized using selective sulfur oxidation of benzothiophene group by meta-chloroperoxybenzoic acid at room temperature, and their photophysical and chemical properties were studied. These compounds exhibited good photochromic behavior with a good fatigue property under consecutive ultraviolet (UV) and visible irradiation. The ring-closed form emitted fluorescence upon UV excitation and the wavelength of fluorescence varied depending on the substituent. Compounds 2-5 exhibited high conversion ratios, reaching 95% for compound 5, the benzoyl derivative, under UV irradiation. This high conversion is thought to be due to the lower quantum yield of the ring-opening reaction compared to the ring-closing reaction.