Resonance-assisted hydrogen bonds revisited. Resonance stabilization vs. charge delocalization

Phys Chem Chem Phys. 2013 Feb 21;15(7):2514-22. doi: 10.1039/c2cp43562d. Epub 2013 Jan 15.

Abstract

The origins of stabilization in the short strong hydrogen bonds commonly referred to as "resonance-assisted" (RAHB) have been revisited using the modern valence-bond theory, the hybrid variational-perturbational interaction energy decomposition scheme and atoms in molecules (AIM) analysis. Dimers of carboxylic acids and amides have been chosen as the model structures for intermolecular RAHBs, while for the intramolecular case malondialdehyde and its substituted derivatives have been selected. The estimated (negligible) resonance stabilization energies and relative magnitudes of interaction energy components indicate that the origin of stabilization in the studied complexes is charge-delocalization. Although in the case of intramolecular RAHBs the resonance effects are much more pronounced, still they are a relatively minor contribution to the total stabilization energy. In fact, the estimated resonance stabilization energies diminish with an increasing strength of the hydrogen bond (as indicated by AIM and structural descriptors).