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A computational NQR study on the hydrogen‐bonded lattice of cytosine‐5‐acetic acid
Author(s) -
Mirzaei Mahmoud,
Hadipour Nasser L.
Publication year - 2007
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.20845
Subject(s) - electric field gradient , quadrupole , nuclear quadrupole resonance , chemistry , basis set , hydrogen bond , gaussian , molecule , density functional theory , computational chemistry , molecular physics , atomic physics , nuclear magnetic resonance , physics , organic chemistry
A computational study at the level of density functional theory (DFT) employing 6‐311++G** standard basis set was carried out to evaluate nuclear quadrupole resonance (NQR) spectroscopy parameters in cytosine‐5‐acetic acid (C5AA). Since the electric field gradient (EFG) tensors are very sensitive to the electrostatic environment at the sites of quadruple nuclei, the most possible interacting molecules with the target one were considered in a five‐molecule model system of C5AA using X‐ray coordinates transforming. The hydrogen atoms positions were optimized and two model systems of original and H‐optimized C5AA were considered in NQR calculations. The calculated EFG tensors at the sites of 17 O, 14 N, and 2 H nuclei were converted to their experimentally measurable parameters, quadrupole coupling constants and asymmetry parameters. The evaluated NQR parameters reveal that the nuclei in original and H‐optimized systems contribute to different hydrogen bonding (HB) interaction. The comparison of calculated parameters between optimized isolated gas‐phase and crystalline monomer also shows the relationship between the structural deformation and NQR parameters in C5AA. The basis set superposition error (BSSE) calculations yielded no significant errors for employed basis set in the evaluation of NQR parameters. All the calculations were performed by Gaussian 98 package of program. © 2007 Wiley Periodicals, Inc. J Comput Chem 2008