The Power of Nonconventional Phenyl C-H•••N Hydrogen Bonds: Supportive Crystal-Packing Force and Dominant Supramolecular Engineering Force

The role of phenyl C-(HN)-N-... interactions in crystal engineering is explored with a variety of fluorinated phenyl-containing compounds. In particular, we show that this interaction can guide the formation of one-dimensional phenyl C-H...N hydrogen-bonded ribbons with, for example, 4-(2,3,5,6-tetrafluorophenylethynyl)pyridine. The interaction is shown to also control the formation of self-complementary homodimers with 3-(2,3,4,5-tetrafluorophenylethynyl)pyridine. We also demonstrate that the phenyl C-(HN)-N-... hydrogen bond interaction is capable of enticing co-crystallization of molecules such as 2,3,5,6,2',3',5',6'-octafluorobiphenyl and 4,4'-dipyridyl. Finally, we describe the use of an intramolecular scaffold to evaluate the effect of electron-withdrawing substituents on the strength of a phenyl C-(HN)-N-... hydrogen bond.