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How resonance assists hydrogen bonding interactions: An energy decomposition analysis
Author(s) -
Beck John Frederick,
Mo Yirong
Publication year - 2006
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.20523
Subject(s) - chemistry , hydrogen bond , intermolecular force , resonance (particle physics) , delocalized electron , interaction energy , chemical physics , covalent bond , valence bond theory , computational chemistry , crystallography , atomic physics , molecular orbital , molecule , organic chemistry , physics
Block‐localized wave function (BLW) method, which is a variant of the ab initio valence bond (VB) theory, was employed to explore the nature of resonance‐assisted hydrogen bonds (RAHBs) and to investigate the mechanism of synergistic interplay between π delocalization and hydrogen‐bonding interactions. We examined the dimers of formic acid, formamide, 4‐pyrimidinone, 2‐pyridinone, 2‐hydroxpyridine, and 2‐hydroxycyclopenta‐2,4‐dien‐1‐one. In addition, we studied the interactions in β‐diketone enols with a simplified model, namely the hydrogen bonds of 3‐hydroxypropenal with both ethenol and formaldehyde. The intermolecular interaction energies, either with or without the involvement of π resonance, were decomposed into the Hitler‐London energy (Δ E HL ), polarization energy (Δ E pol ), charge transfer energy (Δ E CT ), and electron correlation energy (Δ E cor ) terms. This allows for the examination of the character of hydrogen bonds and the impact of π conjugation on hydrogen bonding interactions. Although it has been proposed that resonance‐assisted hydrogen bonds are accompanied with an increasing of covalency character, our analyses showed that the enhanced interactions mostly originate from the classical dipole–dipole (i.e., electrostatic) attraction, as resonance redistributes the electron density and increases the dipole moments in monomers. The covalency of hydrogen bonds, however, changes very little. This disputes the belief that RAHB is primarily covalent in nature. Accordingly, we recommend the term “resonance‐assisted binding (RAB)” instead of “resonance‐assisted hydrogen bonding (RHAB)” to highlight the electrostatic, which is a long‐range effect, rather than the electron transfer nature of the enhanced stabilization in RAHBs. © 2006 Wiley Periodicals, Inc. J Comput Chem 28: 455–466, 2007