Kinetics and mechanism of photochromic transformations of a 2,3-diarylcyclopentenone

Abstract

Photochemistry of recently synthesized 2,3-bis-(2,5-dimethylthiophen-3-yl-cyclopent-2-en-1-one) (diarylcyclopentenone, 1A) as a characteristic representative of photochromic 2,3-diarylcyclopent-2-en-1-ones (DCPs) was examined by means of stationary an nanosecond laser flash photolysis. Quantum yields of forward and backward photochemical reactions and molar absorption coefficient of the closed form were measured. Contradictions in the literature values of these parameters were eliminated. In laser flash photolysis experiments the formation of the 1A open form triplet state was exhibited, and the rate constants of the reactions of its decay were measured. 1A demonstrates rather low fatigue resistance, as any of other DCPs. In spite of the triplet state formation, photodegradation of 1A is not caused by the reactions of singlet oxygen.