Reductive electron transfer of dimethyl disulfide in hydrated electron clusters: The critical role of solvation and dynamic hydrogen bonding

Abstract

Understanding the reactivity of hydrated electrons, especially the role of solvent dynamics, remains a key challenge. Its reaction with dimethyl disulfide, a system whose known highly exothermicity contrasts with its low electron affinity, using density functional theory based molecular dynamics simulations is investigated. This work reveals a mechanism gated by a critical S···H hydrogen bond, which enables a kinetically challenging electron transfer step. The overall exothermicity is not driven by electron transfer itself but by a large release of solvation energy that stabilizes the nascent radical anion of dimethyl disulfide. Following the electron transfer, the system undergoes a complex solvent reorganization driven by dynamic hydrogen bonding, where a relaxation of the initial hydrated electron cavity competes with the stabilization of the resulting radical anion. These findings suggest that insufficient solvation can either kinetically hinder the initial electron transfer or by subsequently failing to stabilize the anion, promote S-S bond cleavage.