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Keywords:

correlations between h-bond parameters, dff(b3lyp) calculations, water complexes of pyridine and imidazole analogs, molecules modeling cytosine, ab-initio calculations, theoretical calculations, isocytosine tautomers, ar matrices, nitrogen bases, h2o, monomer, Science & Technology, Physical Sciences, Chemistry, Physical, Chemistry, correlations between H-bond parameters, DFF(B3LYP) calculations, MOLECULES MODELING CYTOSINE, AB-INITIO CALCULATIONS, THEORETICAL CALCULATIONS, ISOCYTOSINE TAUTOMERS, AR MATRICES, NITROGEN BASES, H2O, MONOMER, 0306 Physical Chemistry (incl. Structural), 0307 Theoretical and Computational Chemistry, Inorganic & Nuclear Chemistry, 3402 Inorganic chemistry

Abstract:

Relations between selected experimentally observed matrix isolation FT-IR and/or DFT(B3LYP)/6-31++G** predicted parameters are investigated for a series of 1: 1 water complexes of pyridine and imidazole derivatives. Regular correlations are observed for: (i) the experimental and calculated OH tretching frequency shifts; (ii) the ratio between the observed and calculated IR stretching frequencies of the water OH group involved in the hydrogen bond and the proton affinity of the hydrogen bonding site (N atom) of the base; (iii) the H-bond interaction energy and the OH stretching frequency shift; (iv) the calculated OH and N...H distances and the interaction energy of the H-bond; and (v) the interaction energy of the H-bond and the square root of the intensity enhancement of the OH stretching mode. These correlations are restricted to structurally similar systems (i.e. to the pyridine or the imidazole analogs). These correlations demonstrate that the DFT(B3LYP) method is very suitable to predict trends in the parameters related to the H-bonding. (C) 2003 Elsevier Science B.V. All rights reserved.