F or O, Which One Is the Better Hydrogen Bond (Is It?) Acceptor in C-H•••X-C (X- = F-, O=) Interactions

Three sets of statistical analyses have been performed to evaluate whether C-F or C=O is the better C-H hydrogen bond acceptor and to understand the nature and preferred geometry of the CH-F-C interactions. The first analysis uses Hirshfeld surface of the molecules, which shows that C=O is a better hydrogen bond acceptor than C-F, though C-H center dot center dot center dot F-C interactions also play an important role in crystal packing. The second analysis compares the population densities of C-H center dot center dot center dot F-C interactions at different H center dot center dot center dot F distances and at different CH center dot center dot center dot F or C-F center dot center dot center dot H angles. This analysis shows the directional nature of this interaction. The third analysis shows which combinations of the C-H center dot center dot center dot F andaC-F center dot center dot H angles are preferred by the C-H center dot center dot center dot F-C interactions.