Photoprocesses in 2-Benzylidene-5-(Pyridin-3-ylmethylene)cyclopentanone and Its Derivatives in Acetonitrile

Spectral, luminescent, and time-resolved properties of 2-bezylidene-5-(pyridin-3-ylmethylene)cyclopentanone and its derivatives with electron-donating substituents (diethylamino, methoxy, methylthio, and dimethoxy) on the benzene cycle have been studied in acetonitrile at room temperature. The presence of substituents causes a long-wavelength shift of the absorption band maximum by 26–114 nm in comparison with the unsubstituted dienone and a long-wavelength shift of the fluorescence maximum by 43–125 nm in comparison with the methoxy derivative. Under laser irradiation of oxygen-free dienone solutions, intersystem crossing to the triplet state occurs with a half-life of 0.7–1.5 μs. A stable photoproduct is formed for the methoxy, methylthio, and dimethoxy derivatives of dienone.