Proton Transfer Potentials in Hydrogen-Bonded Systems: (H5O2)+

Document Type

Article

Journal/Book Title/Conference

International Journal of Quantum Chemistry

Volume

18

Issue

S7

Publisher

John Wiley & Sons, Inc.

Publication Date

3-5-1980

First Page

199

Last Page

206

Abstract

Ab initio molecular orbital calculations at the split-valence shell level are used to examine a theory of proton transport across biomembranes involving the transfer of protons along hydrogen-bonded chains. Potentials for central proton motion in (H2OHOH2)+ are calculated using the 4-31G basis set. This procedure is shown to provide results in close agreement with more extended calculations including electron correlation. A potential with a shallow single minimum corresponding to a centrally located proton is obtained for small interoxygen separations. However, for separations greater than about 2.4 Å, double-well potentials are calculated. The potentials are relatively insensitive to the inclusion of additional H2O molecules or geometry optimizations. The effects of angular distortions of the hydrogen bond on the barriers separating the two minima are investigated. Small distortions of less than 20d̀ or so increase the barriers slightly, but a sharp rise is noted for greater distortions. In addition, rotations of the two water molecules in opposite directions produce the largest increase in proton transfer barriers.

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