Halogen bonding with dihalogens and interhalogens

Abstract

The fact that iodine forms complexes with Lewis bases has been recognized since at least the middle of the nineteenth century. With the development of X-ray crystallography and modern spectroscopic techniques, the directionality and strength of halogen bonds has been determined. Halogen bonds between dihalogens and Lewis bases fall into four main categories: simple adducts, bridging adducts, amphoteric adducts, and adducts that are both bridging and amphoteric. In the case of very strong interactions between the electron donor and the dihalogen, the halogen-halogen bond is broken, leading to ionic or oxidative addition products. The theoretical description of the halogen bond has also progressed, in parallel with the development of increasingly sophisticated theories of bonding. Relatively accurate predictions of structural parameters and interaction energies are now possible, but they present a challenge to available computational hardware and software.