Halogen bond with the multivalent halogen acting as the Lewis acid center

The halogen bond in complexes of BrF3 and BrF5 is analyzed where the trivalent and pentavalent bromine centers interact as the Lewis acid with the nitrogen Lewis base centers of HCN and N2 molecules as well as with the F−, Cl− and Br− anions. The halogen bonds analyzed here possess characteristics typical for other interactions as for example for the hydrogen bond or the halogen bond with the monovalent halogen center. However there are differences; the whole sphere of the multivalent Br-center is characterized by the positive electrostatic potential thus it acts as the Lewis acid, while the halogen monovalent atoms are usually characterized by the dual character since they may act simultaneously as the Lewis acid and as the Lewis base. The Quantum Theory of Atoms in Molecules and the Natural Bond Orbital method are applied here.