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A Direct Proof of the Resonance‐Impaired Hydrogen Bond (RIHB) Concept
Author(s) -
Lin Xuhui,
Wu Wei,
Mo Yirong
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201705424
Subject(s) - intramolecular force , delocalized electron , resonance (particle physics) , hydrogen bond , chemistry , valence bond theory , bond order , single bond , low barrier hydrogen bond , three center two electron bond , acceptor , covalent bond , computational chemistry , bond length , crystallography , atomic physics , molecule , molecular orbital , stereochemistry , physics , quantum mechanics , crystal structure , group (periodic table) , organic chemistry
The concept of resonance‐enhanced hydrogen bond (RAHB) has been widely accepted and applied as it highlights the positive impact of π‐conjugation on intramolecular H‐bonds. However, electron delocalization is directional and there is a possibility that π‐resonance goes from the H‐bond acceptor to the H‐bond donor, leading to a negative impact on H‐bonds. Here we used the block‐localized wavefunction (BLW) method which is a variant of ab initio valence bond (VB) theory and able to derive strictly electron‐localized structures self‐consistently, to quantify the interplay between H‐bond and π‐resonance in the terms of geometry, energetics and spectral properties. The comparison of geometrical optimizations with and without π‐resonance shows that conjugation can indeed either enhance or weaken intramolecular H‐bonds. We further experimented with various substituents attached to either the H‐bond acceptor and/or H‐bond donor side(s) to tune the H‐bonding strength in both directions.