An ab initio study of the structure and energetics of the bisulfite ion in the gas phase and in aqueous solution

Ab initio molecular orbital methods, employing large basis sets and the MP2, B3LYP and BD(T) correlation approaches, have been used to study the two low energy isomers of bisulfite (HSO3-) in the gas phase and in aqueous solution. Explicit solvation is found to be essential to predict the correct order of isomer stability and yields an excellent prediction of the relative energies of the C-1 and C-3v forms. The effect of explicit solvent on molecular geometry must be included to allow accurate prediction of the observed NMR shifts, which are calculated using the GIAO method. The vibrational frequencies are also calculated. The results of our study are discussed in terms of the role of bisulfite in the atmospheric oxidation of SO2. (C) 1997 Elsevier Science B.V.