Hydrogen bonded nicotinic acid-water complexes studied by ab-initio and density functional theory

Achchhe Lal*, Neha Shukla and

Abstract

Molecular structure and Vibrational spectra of Nicotinic Acid (NA)–Water (W) complexes with stoichiometric ratios ranging from 2:1 (NA2W) to 1:3 (NAW3) Complexes have been studied by means of quantum chemical calculations using HF and B3LYP methodology and the 6-311++G(d, p) basis set. It was found that the strength of hydrogen bond between the hydrogen and the nitrogen increases with increasing the number of water molecules. Structural parameters of the optimized geometries, total energies and dipole moment have been calculated. We show that increasing the number of water molecules strength of the binding energy as well as bond length between N and H decreases i.e. stability increases. The ring-breathing mode frequency ʋ1 of the reference system NA has been chosen as a marker band to the strengths of hydrogen bonding. IR intensity and Raman activity corresponding to the ringbreathing mode frequency ʋ1 have been calculated for three numbers of hydrated complexes of Nicotinic Acid.