Ab initio molecular orbital calculations of the structures and vibrational spectra of some molecular complexes containing sulphur dioxide

The properties of a number of electron donor–acceptor and hydrogen-bonded complexes formed between sulphur dioxide and the series of molecules ammonia, water, hydrogen fluoride, phosphine, hydrogen sulphide and hydrogen chloride have been determined by means of ab initio molecular orbital calculations. The properties of interest are the interaction energies, the molecular structures and, particularly, the vibrational spectra. The natures of the complexes formed, the trends in the interaction energies, the perturbations of the monomer structures and the wavenumber shifts and infrared intensity ratios have been rationalized in terms of the properties of the partner molecules in the complexes. The properties of the complexes have also been compared with those of a parallel series of aggregates in which the Lewis acid molecule is boron trifluoride, and the effect of substituting boron trifluoride by sulphur dioxide has been discussed.