Coupled Anharmonic Vibrational Dynamics of the Hydrogen Bond in Binary Complexes

Abstract

We report anharmonic vibrational analyses of the coupling between the red-shifted high frequency HFstretching vibrations and low frequency intermolecular modes in the hydrogen-bonded complexes thiirane-HF and H2 O-HF. The important non-diagonal anharmonicities found in high-level ab initio calculations are consistent with recent experimental results. The physical origin of the coupling mechanism implies that a physically correct treatment of hydrogen-bond induced vibrational red shifts requires a vibrational treatment far beyond the customary one-dimensional approach combined with large basis set electronic structure calculations.