A quantum-chemical study of the effect of complexation on the spectral and luminescent properties and photolysis of cresol

The effects of methyl substitution and complexation on the spectral and luminescent properties of the phenol molecule and on the photodissociation of its OH bond are studied by methods of quantum chemistry. It is shown that methyl substitution at the ortho or para positions of phenol does not affect markedly the electronic spectrum or photophysical processes in the phenol molecule. The reasons for the dependence of the quantum yield of fluorescence gamma on the excitation energy and the type of solvent are ascertained. Thus, the decrease in gamma with increasing energy of excitation is associated with a higher efficiency of the photodissociation of the OH bond, whereas the increase in gamma in proton-donating solvents is attributed to the increase by similar to2000 cm(-1) of the activation energy of photoreaction upon formation of an H bond with solvent molecules. The mechanism of the photoreaction is established. (C) 2004 MAIK "Nauka/Interperiodica".