Testing the reality of F··F halogen bonds

Abstract

Crystal structures show F atoms of neighboring molecules sitting close to one another and are presumed to help stabilize the crystal via halogen bonds. The possibility of such F··F halogen bonds is tested via DFT calculations that consider first the actual crystal geometry, and then proceed to a more general set of systems without the constraints of the packing forces within the crystal. It is shown that these F··F contacts offer little if any in the way of stabilization, and should not be categorized as halogen bonds.