A gradient-corrected density functional study of structure, harmonic vibrational frequencies and charge distribution of benzenesulfonate anion on the ground-state potential energy surface

Abstract

A density functional study of the structure, harmonic vibrational force field, and charge distribution of benzenesulfonate anion combined with a solid-state FT-IR study of sodium benzenesulfonate is presented. Two combinations of exchange/correlation functionals (BLYP and B3LYP) were employed within the quantum chemical approach, using the standard double-zeta quality 6-31+G(d) basis set for orbital expansion. The DFT predicted structure of the studied species is in a very good agreement with the available crystallographic data (significantly better in comparison with our previous HF SCF results for benzenesulfonate and 4-methylbenzenesulfonate anions). Both the B3LYP and BLYP/6-31+G(d) vibrational analyses of the benzenesulfonate anion confirmed our previously proposed reassignments of several vibrational bands of this system based on the HF SCF/6-31+G(d) vibrational force field. The B3LYP predicted vibrational frequencies are superior to the BLYP ones. The Mulliken population analysis predicts a strong anionic charge delocalization over the phenyl ring (−0.54 and −0.56e, B3LYP and BLYP levels correspondingly), whereas according to the electrostatic potential derived schemes, it is mainly localized within the SO3 group. The latter result seems to be more in line both with the observed hydrogen bonding in the solid crystalline hydrates and with chemical intuition.