Photophysics, Photochemistry, and Kinetics of Photochromic Fulgides

Article abstract of DOI:10.1021/j100403a018

Nine different substituted bismethylene succinic anhydrides (fulgides) have been examined by microsecond and nanosecond laser flash techniques.In addition, fluorescence lifetimes have been determined for some fulgides.No triplet transients have been observed and oxygen (vs. nitrogen) has no effect on the spectra, or the kinetics of formation (<1 ns) or disappearance (>400 μs) of the colored photoproduct.The relative quantum yield of photocoloration of one fulgide is observed to significantly increase with shorter wavelength excitation (266 nm) vs. longer wavelength (355 nm).This is discussed and considered in terms of earlier observations of a decrease in the quantum yield of fluorescence with increasing energy of excitation.All data strongly suggest that an excited singlet state of ?,?_* character is the originating state for photochorism/photochemistry.