Conventional H-bond (X-H•••Y) vs. X-H•••π interaction?: A theoretical investigation of the nature of borazine-hydrogen halide interactions

High level ab initio calculations have been performed on the borazine-HX (X=F, Cl, Br and I) systems at MP2/6-31 I + + G** level. In the global minimum of B3N3H6-HX, the hydrogen of HX inclined to pointing a nitrogen of the borazine ring. The interaction becomes weaker as one progresses from HF to HI. The binding energies of the borazine complexes are lower than those of the corresponding benzene complexes (about 4 kJ/mol), with the exception of that of HE The symmetry adapted perturbation theory (SAPT) calculations were carried out to decompose the binding energy of these complexes into individual interaction energy components. Both electrostatic, inductive and dispersive energies are important in the description of these interactions. The contribution of electrostatic energies decreases and the dispersion energy increases on moving from HF to HI. A similar result was obtained for the benzene-HX complexes. It was indicated that the conventional H-bond become weaker and the strength of the X-H center dot center dot center dot pi interaction enhanced as one progresses from HF to HI in the borazine-HX complexes.