Proton Transfer in Water Polymers as a Model for Intime and Solvent-Separated Ion Pairs

Abstract

SCF-CNDO/2 calculations, including the continuum solvent effects via an extended version of the generalized Born formula, have been performed for H30+··.(H20) •.•. OH- and (H20) •... Hp+ ... OH- species (n = 0,1,2). The proton potential curves were ealculated by both varying the position of one of the intervening protons and varying the positions of al! of them simultaneously, in a chain of water molecules. The oxygen and remaining hydrogen atoms were kept fixed at several intermolecular distances. By these procedures an intime ion-pair strueture and a one- and two-solvent-separated ion-pair structure were respectively generated. Qualitative results show a stabilization of the intime ion-pair strueture with respect to the solvent-separated one. This effect is even more pronounced when additional water molecules are ineorporated into the chain.