Comment on "Analysis of CF · · · FC interactions on cyclohexane and naphthalene frameworks".

Intramolecular CF···FC interactions in selected organofluorine compounds (all-syn-1,2,3,4- and all-syn-1,2,4,5-tetrafluorocyclohexane, 1,8-difluoronaphthalene, 4,5-difluorophenanthrene, 2,2',5,5'-tetrafluorobiphenyl) were studied at the MP2/aug-cc-pVDZ level using the recently developed noncovalent interaction (NCI) method. For the optimized minima, all CF···FC interactions that are identified by this method are classified as attractive, even in those cases where suitable isodesmic reaction energies fail to provide evidence for an energetic stabilization. Possible relations between these interactions and the observable JFF spin-spin coupling constant values are discussed.