Comparison in the complexes of oxygen-containing σ-electron donor with hydrogen halide and dihalogen molecules

Ab initio and “Atoms in Molecules” studies have been carried on the intermolecular interactions between oxygen-containing σ-electron donors B (B = H2O, H2CO, (CH2)2O) and hydrogen halide HY and dihalogen molecules XY (X, Y = F, Cl, Br). The geometries, energies and topological characteristics of hydrogen-bonded systems have been compared with those of halogen-bonded systems. In general, many properties of the halogen bond are analogous to those of the hydrogen bond. For the same electron acceptor H or X atom, the properties such as bond distance, binding energy, electron density and charge transfer decrease in the sequence of B···HF > B···HCl > B···HBr, B···ClF > B···Cl2, B···BrF > B···BrCl > B···Br2. The bond distance, frequency shift and electron density may be applied as the measure of strength of hydrogen and halogen bond. The decrease in the atomic dipolar polarization and the atomic volume are dependent of the strength of halogen-bonded interaction, while they are independent of the strength of hydrogen-bonded interaction.