Solvent relaxation and proton transfer in the (H5O2)+(H2O)4 species

Abstract

The proton-transfer process in the (H₅O₂)⁺ and (H₅O₂)⁺(H₂O)₄ species has been studied by means of the semi-empirical CNDO/2 and MINDO/3 methods and ab initio calculations using the 3-21G basis set. It has been found that the interoxygen distance does not remain constant in these processes. When four outer molecules are arranged such that they are solvating the four outer hydrogens of the (H₅O₂)⁺ cation, the minimum in which the proton is located midway between the two oxygen atoms is broken down into two minima in which the hydrogen bonds are asymmetric. Solvent relaxation plays an important role in proton transfer, the proton adjusting its position upon changes in solvation.