Contributions of the ionic lattice, nonangular substituents, and perfluoroaromatic π-stacking to the solid states of derivatives of N-benzyl- 2-phenylpyridinium bromide

A study of the crystal packing of six derivatives of N-benzyl-2- phenylpyridinium bromide demonstrated the potential importance of synergism between π-stacking interactions and steric substituent effects in the determination of molecular orientations in an ionic lattice. N-Benzyl-2- phenylpyridinium bromide was substituted with 4-methoxybenzyl, 4-cyanobenzyl, 4-trifluoromethylbenzyl, 4-trifluoromethyl-2,3,5,6-tetrafluorobenzyl, and 2,3,4,5,6-pentafluorobenzyl. Nonangular para substituents on the benzyl ring gave rise to predictable changes in the solid state. These substituents anchored and aligned the molecules by complete or partial interdigitation. The increased stability of perfluoroarene/arene interactions vs arene/arene interactions were manifest in the presence of the strong ionic lattice. The fact that electronic perturbation in π-stacked oriented molecules in these crystals demonstrated partial orthogonality between the directional forces involved in the establishment of the ionic lattice and the much weaker directional contributions to the lattice energy from π-stacking.