| Abstract
| - The reversible proton dissociation and geminate recombination of photoacids is studied as a function oftemperature in monols, diols, and glycerol. For this purpose, we use a strong photoacid 5,8-dicyano-2-naphthol(DCN2) (p≈ −4.5 in water), capable of transferring a proton to alcohols. The experimental data areanalyzed by the Debye−Smoluchowski equation, which is solved numerically with boundary conditions toaccount for the reversibility of the reaction. At high temperature, the proton-transfer rate is almost temperatureindependent, whereas at low temperature, the rate constant has strong temperature dependence. The unusualtemperature dependence is explained using Borgis−Hynes proton transfer theory, based on the Landau−Zener curve crossing formulation. The high-temperature behavior of the rate constant denotes the nonadiabaticlimit, whereas the low-temperature behavior denotes the adiabatic limit. We have used an approximateexpression for the proton-transfer rate, which bridges the nonadiabatic and the solvent controlled adiabaticlimit to fit the temperature dependence curve of the experimental proton-transfer rate constant.
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