Ab initio studies of the properties of some halogen-bonded complexes of ammonia, water, phosphine and hydrogen sulphide

Ab initio calculations, at the second order level of Møller–Plesset perturbation theory and with Dunning’s augmented correlation-consistent polarised valence triple-zeta basis set, have been carried out on two series of molecular complexes. One set consists of the common bases ammonia, water, phosphine and hydrogen sulphide and the electron-acceptor halogens difluorine, dichlorine and dibromine, and the other comprises the interhalogens bromine fluoride, chlorine fluoride and bromine chloride as electron acceptors, with the same set of four bases. The interaction energies, molecular structures, vibrational spectra and charge distribution properties of the complexes have been computed, and the adducts have been characterised as halogen-bonded complexes. The trends in the values of these properties correlate with systematic changes in the base and the halogen species. The computed physical data are in quite good agreement with such experimental results as are available, while the anomalous features of some of the properties of the complexes with phosphine have been rationalised.