Photophysics and Photochemistry of Diphenyl Sulfone. 2. Investigation of the S1 Decay Pathways

Article abstract of DOI:10.1021/j100339a035

An extensive analysis of the S₁ deactivation pathways of diphenyl sulfone (DPS) in alcohols and some other solvents is presented.The combined results of steady-state photolysis, time-resolved fluorescence, and steady-state fluorescence measurements at variable temperature and of S₁ <*> -> T₁ intersystem crossing quantum yield determinations enable a complete characterization of the S₁ photophysics and photochemistry of DPS to be obtained.The main S₁ decay channel appears to be an activated S₁ <*> -> T_n intersystem crossing (E_a ca. 2 kcal/mol), other than S₁ <*> -> T₁.Although the fluorescence emission and S₁ <*> -> T₁ quantum yields show some solvent dependence, they play minor roles in the solvents studied.The state eventually reached in the S₁ <*> -> T_n activated intersystem crossing is proposed to be a dissociative ₃??* state localized on a C-S bond, on the basis of experimental evidence and of some preliminary theoretical data.A simple rationalization of the observations is provided by a model potential energy diagram obtained as an extension of the one previously proposed to account for the results concerning the T₁ decay of the same molecule.Two hypotheses on the mechanisms of the above-mentioned S₁ <*> -> T_n activated intersystem crossing are put forward and briefly discussed.