PNNL

Abstract

In this article we discuss how the solvent energy-gap reaction coordinate arising in weak-overlap charge-transfer theory may be generalized to include nonequilibrium solvation effects in variational transition statetheory (VTST) for arbitrary reactions of neutral or charged species. The discussion also indicates how theparameters of weak-overlap charge-transfer theory may be related to the potential energy surface of a reactionand the potential of mean force. This synthesis of aspects of weak-overlap charge-transfer theory and variationaltransition state theory provides a clearer picture of the usefulness and limitations of the energy-gap coordinatein Marcus theory or in more general contexts. Furthermore, it furnishes a new view of the role of solventcoordinates in electronically adiabatic reactions. As an example, we show how VTST provides a way to treatsolute vibrational coordinates and collective solvation coordinates in a comparable way in the computationalmodeling of aqeuous proton-transfer reactions including quantum mechanical vibrations and multidimensionaltunneling effects.