Unified description of hydrogen bonding and of proton transfer by a two-state effective Hamiltonian

TL;DR

This paper introduces a two-state effective Hamiltonian model that unifies the understanding of hydrogen bonding and proton transfer, providing insights into bond classification, empirical correlations, and predicting UV photo-dissociation phenomena.

Contribution

It presents a simple, chemically motivated Hamiltonian model that explains hydrogen bonding, proton transfer, and related empirical correlations, addressing the longstanding 'H-bond puzzle.'

Findings

Provides a unified framework for hydrogen bonds and proton transfer.

Describes empirical correlations between R, binding energies, and vibrational frequencies.

Predicts UV photo-dissociation of H-bonded complexes via an excited state.

Abstract

An effective Hamiltonian is considered for hydrogen bonding between two molecules due to the quantum mechanical interaction between the orbitals of the H-atom and the donor and acceptor atoms in the molecules. The Hamiltonian acts on two diabatic states and has a simple chemically motivated form for its matrix elements. The model gives insight into the "H-bond puzzle", describes different classes of bonds, and empirical correlations between the donor-acceptor distance R and binding energies, bond lengths, and the softening of vibrational frequencies. A key prediction is the UV photo-dissociation of H-bonded complexes via an excited electronic state with an exalted vibrational frequency.