Adding to sigma holes in halogen bonds

Chemists should no longer ignore charge transfer when explaining supramolecular halogen bonds, a type of bond known since the mid-19th Century. A typical halogen bond (depicted as three dots) in a compound R-X...Y. R–X is the halogen bond donor, where R is a group covalently bonded to halogen X, and Y is a halogen bond acceptor. Now, Jonathan Thirman and Martin Head-Gordon, from the University of California, Berkeley, and their colleagues have used a new computational method based on energy decomposition analysis to investigate various halogen bonds to come to their conclusion that charge transfer should be considered along with the previously known sigma-holes.