An ab initio investigation of some hydrogen-bonded complexes of methanol and dimethylamine

The hydrogen-bonded molecular complexes formed between methanol and dimethylamine, as proton donors, and the series of proton acceptors trimethylamine, dimethyl ether, methyl fluoride, trimethyl phosphine, dimethyl sulphide and methyl chloride, have been studied by means of ab initio molecular orbital theory, at the second order level of Møller–Plesset perturbation theory, and using the 6-311++G(d,p) basis set. The properties determined were the molecular structures, the interaction energies and the vibrational spectra. The results show that, based on the trends in the values of these properties, the order of strength of interaction per proton donor is methanol > dimethylamine and the order per proton acceptor is trimethylamine > dimethyl ether > methyl fluoride for the first row bases and trimethyl phosphine > dimethyl sulphide > methyl chloride for the second row. The first row proton acceptors consistently form stronger hydrogen-bonded complexes than their counterparts from the second row.