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Vibrational spectra and potential energy distributions for 1‐benzyl‐1 H ‐imidazole by normal coordinate analysis
Author(s) -
James C.,
Ravikumar C.,
Jayakumar V. S.,
Hubert Joe I.
Publication year - 2009
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.2160
Subject(s) - natural bond orbital , chemistry , aromaticity , intramolecular force , intermolecular force , imidazole , hydrogen bond , molecule , steric effects , computational chemistry , density functional theory , raman spectroscopy , crystallography , stereochemistry , physics , organic chemistry , quantum mechanics
The Fourier‐transform (FT) Raman and infrared (IR) spectra of the crystallized novel pharmaceutical molecule 1‐benzyl‐1 H ‐imidazole (BI) were recorded and analyzed. The geometry, intermolecular hydrogen bond, and harmonic vibrational wavenumbers of BI were investigated with the help of B3PW91 density functional theory (DFT) methods. The detailed interpretation of the vibrational spectra was carried out with the aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). The aromaticities of the imidazole and phenyl rings were studied using the standard harmonic oscillator model of aromaticity (HOMA) index. Natural bond orbital (NBO) analysis on BI was carried out to demonstrate the various intramolecular interactions that are responsible for the stabilization of this molecule leading to its medicinal activity. The potential energy profile corresponding to the torsion around the bridge bonds connecting the two rings was drawn to explain the steric and/or electronic effects using potential energy surface (PES) scan studies. The pronounced double‐bond localization in the imidazole ring upon intermolecular H‐bonding appears to be the cause for its enhanced aromaticity. Copyright © 2008 John Wiley & Sons, Ltd.