Further Evidence on the Importance of Fluorous–Fluorous Interactions in Supramolecular Chemistry: A Combined Structural and Computational Study

The
solid-state structures of CF3(CF2)5CH2CO2H and a fluorous triazole are
reported, both of which display a wide variety and large number of
noncovalent interactions in their packing. The solid-state structure
of CF3(CF2)5CH2CO2H is stabilized by multiple F···F contacts
but only one C–H···F–C interaction, as
well as O–H···O and C–H···O
hydrogen bonds. In contrast to other reported structures, the torsion
angles in the fluorous chain are close to 180°, which means that
the fluorine atoms are eclipsed. A DFT study of the interactions in
both compounds show that F···F interactions, along
with stacking and C–H···F and C–H···O
contacts, are individually weakly energetically stabilizing, but collectively,
they can give rise to interaction energies of up to 13 kcal mol–1. A topological approach to the interactions using
atoms-in-molecules (AIM) theory reveals that there are bond critical
points between the C–F···F–C interactions
as well as C–F···H–C interactions that
are not recognized when using only the van der Waals distances.