Experimental and theoretical studies of molecular complexes.

Abstract

The binary complexes comprising the molecules hydrogen fluoride, hydrogen chloride, water, hydrogen sulphide, ammonia, phosphine, methane and silane have been studied by ab initio molecular orbital theory thus generating a matrix of eight by eight molecular complexes. The structures, energetics and vibrational spectra of these molecular complexes, both homodimers and heterodimers, have been studied at the second order level of Møller-Plesset perturbation theory using the 6-31G** basis set, by means of the Gaussian 92 computer program. The self consistent field interaction energies have been further dissected into their various components according to the Morokuma scheme, using the Monstergauss computer program. An analysis of the computed interaction energies of the complexes has also been carried out. A complete normal mode analysis, identifying the normal modes of Vibration, has been carried out using the Vibra program. The infrared spectra of some of the associated species have also been determined experimentally by means of the matrix isolation technique using argon and nitrogen as matrix gases. The combined use of the theoretical and experimental approaches has enabled reliable vibrational assignments to be made, which have been used in determining the molecular structures of the aggregates formed on complexation.