Intramolecular halogen bonding: an interacting quantum atoms study

In this paper, we study the nature of recently synthesized intramolecular halogen bonds (Widner et al. in J Org Chem 79: 6269-6278, 2014) within the framework of atoms-in-molecules theory using the interacting quantum atoms energy decomposition. This scheme not only enables us to determine the stabilizing or destabilizing character of such interactions depending on the nature of the halogen atom and of the main substituents, but also provides a clear estimation of electrostatic and covalency contributions. Furthermore, it affords useful tools for the rationalization of the sometimes unusual observed topologies through the exchange channels competition paradigm. Finally, comparisons with intermolecular halogen bonds are presented, and terminology issues are discussed in light of some unexpected counterintuitive results.