Photophysics of ANS. IV. Electron transfer quenching of ANS in alcoholic solvents and mixtures

ANS is observed to decay from the fluorescent state with distributed kinetics in nearly pure ethanol solvent, notwithstanding that in mixed ethanol/water solvents the decay is discrete and biexponential. The origin of this behavior is investigated. In particular, a theory of electron transfer theory in the adiabatic regime is adduced, with specific involvement of solvent cage structure in the form of the solvent-electron polaron wave function. Properties of various polarons for various solvent systems are predicted and, for the case of ethanol and cyclohexanol, employed to generate the observed Arrhenius-type decay parameters in a quantitative fashion.