Electron-Driven Proton Transfer Along H2O Wires Enables Photorelaxation of πσ* States in Chromophore-Water Clusters.

The fates of photochemically formed πσ* states are one of the central issues in photobiology due to their significant contribution to the photostability of biological matter, formation of hydrated electrons, and the phenomenon of photoacidity. Nevertheless, our understanding of the underlying molecular mechanisms in aqueous solution is still incomplete. In this paper, we report on the results of nonadiabatic photodynamics simulations of microhydrated 2-aminooxazole molecule employing algebraic diagrammatic construction to the second order. Our results indicate that electron-driven proton transfer along H2O wires induces the formation of πσ*/S0 state crossing and provides an effective deactivation channel. Because we recently have identified a similar channel for 4-aminoimidazole-5-carbonitrile [Szabla, R.; Phys. Chem. Chem. Phys. 2014, 16, 17617-17626 ], we conclude this mechanism may be quite common to all heterocyclic compounds with low-lying πσ* states.