On the nature of halogen bond - The Kohn-Sham molecular orbital approach

The nature of halogen bonding is investigated for a set of H3CX…OCH2 and F3CX…OCH2 (X = Cl, Br, I) molecular complexes. The Kohn-Sham MO investigation indicates effective stabilizing charge transfer/polarization interaction, while electrostatic interaction contributes only slightly to the total bonding interaction, being systematically overbalanced by exchange repulsion. Thus, the covalent nature of halogen bonding may be expected on the basis of the obtained results. What is more, the halogen atom, being Lewis acid in halogen bonding, may simultaneously act as Lewis base in hydrogen bonding. The same mechanism of anisotropic charge distribution on halogen atom is responsible for this dual character.