Photoprocesses of Bis(diethylaminobenzylidene)cyclopentanone upon Nanosecond Laser and Continuous Irradiation in Acetonitrile

Spectral, luminescent, and kinetic properties of 2,5-bis(4-diethylaminobenzylidene)cyclopentanone (ketocyanine, A) in air-saturated and oxygen-free acetonitrile have been studied. The ns-Laser and continuous photoexcitation of A results in a product B undergoing in the oxygen-free solution the intersystem crossing into the triplet state with the lifetime of 1 µs. The photoinduced conversion of A into B occurs within a time shorter than 1 µs and is manifested in a decrease in both the fluorescence intensity of A and absorbance at 457 nm and in the appearance of a new absorption at λ > 535 nm. The product B undergoes photoinduced conversion to the parent A via both the excited singlet and triplet states of B.