What makes halogen bonds stick? From high accuracy to simple models

Halogen bonds have seen application in variety of settings - from small gas-phase complexes through to liquid crystals and nanomaterials, but the nature of the interaction itself isn't particularly well understood. Using high-accuracy theoretical chemistry methods, such as explicit correlation and symmetry adapted perturbation theory, we have begun to probe the underlying mechanism of halogen bonding and validated a set of rules for predicting the structures of small complexes. This also provides some insight into the linearity of the interaction when compared to analogous hydrogen bonds.

Analysis of the highly accurate data has allowed us to develop a simple model for the prediction of halogen bond interaction energies that are typically accurate to within 2 kJ/mol. The implications of this model in terms of physical insights into the underlying mechanism of interaction and the interesting cases where halogen bonds display significant charge transfer will be discussed.