Engineering polar crystal structures by π–π stacking of N-perfluoroarylbenzimidazoles

1-(4-Nitrilo-2,3,5,6-tetrafluorophenyl)benzimidazole, 2, and 1-(2,3,5,6-tetrafluoropyridyl)-2-methylbenzimidazole, 4, crystallize in the polar space groups Cc and Pca21, respectively. Both structures arise from π–π stacking interactions. For 2 the stacking gives rise to columns of alternating complementary rings that are approximately orthogonal. For 4 the stacking leads to parallel columns, with the polarity arising from the arrangement of the resulting sheets of molecules, between which there are no π–π stacking interactions. The syntheses of 2 and 4 and related perfluoroarylbenzimidazoles are also reported.