Solvent reorganization triggers photo-induced solvated electron generation in phenol

Abstract

The analysis of the absorption spectrum and density of states of a cluster of phenol solvated with 15 water molecules indicates that the reorganization of the water molecules, facilitating the formation of solvated electrons, is a plausible mechanism in the photodissociation of phenol. Using quantitative wavefunction analysis, we demonstrate that while charge-transfer states involving electron transfer from phenol to water are mainly dark, a considerable number of them exists below the maximum of the ππ* absorption band and could be populated by internal conversion. These low-lying charge-transfer states do not show extended O–H distances, but are found for large electron–hole separations at which several water molecules can solvate and stabilize the transferred electron. Thus, charge-transfer states in solvated phenol can be stabilized by two factors: (i) elongation of the O–H bond, as was extensively discussed in the past, and (ii) reorganization of solvent molecules, as it is shown here.