Directionality of intermolecular C-F•••F-C interactions in crystals: experimental and theoretical charge density study

Bonding intermolecular F center dot center dot center dot F interactions were analyzed in crystal of a fluorinated benzene derivative using topological analysis of experimental charge density distribution. It was found that the values of electron density and potential energy density in bond critical points of the F center dot center dot center dot F interactions in crystal depended on the distance between the fluorine atoms, rather than on the corresponding C-F center dot center dot center dot F angles. The directionality of these F center dot center dot center dot F interactions was demonstrated by DFT-D and MP2 calculations for model hexafluorobenzene dimers. Possible discrepancies between dimerization energies computed by ab initio methods and via empirical correlations are discussed.