Halogen atoms in organic compounds typically can be found at the periphery of molecules. For this reason, they are ideally positioned to be involved in intermolecular interactions. It is well-known that the electron density around the halogen nucleus is highly anisotropic so that halogens can serve both as electron-acceptors and -donors. While we acknowledge that the terminology used to name noncovalent interactions given by halogen atoms has to be as unifying as possible, it is our opinion it has always to be done in keeping with the electrophile/nucleophile role the halogen atom plays. The term halogen bonding has been introduced for describing any noncovalent interaction involving halogens as acceptors of electron density. In our opinion, its use also to address interactions in which halogen atoms functions as electron-donors is conceptually misleading and contrasts with the clear tendency, well-documented in the literature, to name such -X---H-Y interactions differently (i.e. hydrogen bonds).
This project will attempt to give a modern definition of halogen bonding that is as inclusive as possible. Also, intermolecular interactions will be categorized logically considering the physical forces involved.