Halogen ... phenyl supramolecular interactions in the solid state: hydrogen versus halogen bonding and directionality

Halogen bonding is a supramolecular interaction that was first described 150 years ago and whose crystallographic description was awarded a Nobel prize in 1969. After having been overlooked for a long time, its applicability for molecular recognition processes has increasingly been recognized by the scientific community over the past decade. A comprehensive statistical analysis of the solid-state structures deposited in the Cambridge Structural Database is presented herein that clearly shows that halogen bonding to the pi-system of a phenyl moiety is frequent and can be directional.