Solvent isotope effect on the fluorescence of azoalkanes

Abstract

A study of fluorescence quantum yields and fluorescence lifetimes of the cyclic azoalkanes I and II reveals a striking dependence of Φ F and τ F on solvent and on isotopic substitution (OH å OD). A mechanism involving specific deactivation of the fluorescent state from a hydrogen bonded complex is proposed to rationalize the data. The observation that the quantum yield for decomposition of I does not correlate with the variation of fluorescence parameters with solvent and isotopic change leads to the conclusion that the state responsible for photoreaction proceeds the fluorescent state.