A simple dipole isomerization model for non-equilibrium solvation dynamics in reactions in polar solvents

Abstract

Abstract A simple model for dipole isomerization reactions in polar solvents is studied. A full dynamical treatment at the generalized Langevin equation level reveals several non-equilibrium solvation regimes in which the rate constant differs considerably from the standard equilibrium solvation, transition state theory predictions. In addition, the solvent is found to be heavily involved in the reaction coordinate, in contrast to the standard equilibrium solvation view. The marked differences from a Kramers Langevin equation level description are also described. In each regime, the rate constant and reaction coordinate are found analytically, and typical reaction system-solvent trajectories are displayed. A related normal-mode description convenient for strong reaction system-nearest-neighbor solvent dipole interactions is constructed. In this perspective, non-equilibrium solvation effects on rates and reaction coordinates are interpreted in terms of a bias of the reactive motion towards the direction of least friction.