The nature of hydrogen bonding plays a vital role in understanding the structure and properties of substances, the mechanism and trend of chemical reaction processes, and therefore has been widely studied by experimental and theoretical chemists. Valence bond theory provides intuitive chemical understanding and new perspectives to weak interactions (including hydrogen bonding), and related works can be found in the following articles published by our team:

1. Red-Shifting versus Blue-Shifting Hydrogen Bonds:Perspective from Ab Initio Valence Bond Theory, J. Phys. Chem. A 2016, 120,2749−2756

2. Valence Bond Based Energy Decomposition AnalysisScheme and Its Application to Cation−π Interactions, J. Phys. Chem. A 2018,122, 5886−5894 

Recently, Sason Shaik from Hebrew University and coworkers applied the valence bond theory to the study of nine hydrogen bond systems, including  (F---H–F)^-, (HO---H–OH)^-, (CN---H–NC)^-, (NC---H–CN)^-, H₂CO---H–NH₂, H₂O---H–OH, H₃N---H–CF₃, HF---H–F and H₃N---H–F.

The calculation results show that the hydrogen bond interaction is dominated by polarization (ΔE_POL) and charge transfer (ΔE_CT). In different energy decomposition analysis (EDA) methods, which of these two interactions dominates the strength of hydrogen bond is inconsistent; however, the sum of these two terms for different hydrogen bond systems obtained by valence bond theory shows the same trend as the results obtained by various EDA methods.

This study provides a new understanding of the nature of hydrogen bond interactions through the calculation of valence bond theory, that is, polarization and charge transfer are entangled in hydrogen bond interactions, and their relative values may be interdependent.

It is also found that the covalence-ion resonance energy (charge transfer energy) of the hydrogen bond is in linearly with the dissociation energy of the corresponding hydrogen bond. This means it is possible to indirectly evaluated the strength of hydrogen bond by experiments via measuring the dissociation energy of the hydrogen bond.

The analysis of valence bond wave function shows that the ionic structure of hydrogen bond system enhances the electropositivity of hydrogen bond acceptor compared with free water molecules. In the case of water dimers, the ionic structure enhances the electric field of the O−H bonds outside the water cluster, leading to an unexpected REDOX reaction and contributing to the catalytic reaction of water droplets and water-hydrophobic interfaces.

Reference：

Valence BondTheory Allows a Generalized Description of Hydrogen Bonding

Sason Shaik,* David Danovich, and Richard N. Zare*

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