Intermolecular Interactions of Organic Fluorine Seen in Perspective

In this study, we have assessed the influence that different types of fluorine interactions have on how molecules pack. This was done by taking each type of interaction in turn and establishing the ratio of its frequency of occurrence in organic crystal structures to the frequency expected if packing were random. The results allow us to see fluorine interactions in perspective: which are the most influential and which the least. Only a few of the interactions occur more often than would be expected by chance, and those few are not the strongest interactions that fluorine can make. The intramolecular environment of fluorine can strongly influence the interactions it makes, despite the general view that this element has low polarizability. The amphiphilic nature of the trifluoromethyl group is clearly seen, but F···F interactions between −CF3 fluorine atoms occur appreciably more often than expected by chance only in centrosymmetric structures. Many other insights were obtained in this objective analysis of the interactions of organic fluorine.