TUNNEL EFFECT IN PROTON-TRANSFER

Semiempirical computations were carried out to determine the tunneling rates in the case of coupled motion of two protons along the reaction coordinate. The following molecular systems were studied for medium intermolecular distances (A—B = 2.72 or 2.75 Å); +AH—BH—A, where A was NH3 or H2O and BH was HF or H2O. In the cases where the bridge was HF, solvation was modeled with just one water molecule attached to each side of the perpendicular axis through HF at 2.75 Å. Coupled motion of three protons was also included in the case of H3O—H2O—H2O—H2O. Copyright © 1990 John Wiley & Sons, Inc.