Can the -CF 3 Group Act as a Tight, Well-Defined Hydrogen Bond Acceptor? A Clear Crystallographic CF 2 -F···H-N + Interaction Says Yes.

The CF 3 group is well noted for being noninteractive with other functional groups. In this Note, we present a highly rigid model system containing a significant hydrogen bonding interaction between a charged N-H donor and a CF 3 acceptor that challenges this accepted wisdom. Spectroscopic and single crystal X-ray crystallography data characterize this interaction, consistent with a weak to moderate hydrogen bond that would be difficult to observe in an intermolecular system.