Hydrogen Bond Dynamics in the Solvation Shell on Proton Transfer in Aqueous Solution

Molecular dynamics (MD) simulations based on the multistate empirical valence bond model have been performed to study the proton transfer (PT) process in aqueous solution. This study focuses on the details of the hydrogen bond (HB) dynamics in the solvation shells of an excess proton accompanied by PT events. The HB dynamics analyses show that the three water molecules in the first solvation shell of hydronium (H3O+) tend to break their accepted HB to maintain a distorted Eigen (H9O4+) configuration. The results from MD simulations show that the cleavage and formation of accepted HBs on the water ligands in the first solvation shell of the proton acceptor water molecule and donor water molecule are crucial to drive the PT. Moreover, the water-donated and -accepted HBs around the H3O+ solvation shells are inequivalent, induced by the excess proton. Coupled with the PT, the donated HBs are enhanced on the proton acceptor side, while, in contrast, the accepted HBs are weakened on the same side.