Synthesis of Perfluoroaryl Heterocycles To Provide Synthons For Crystal Engineering Using π−π Stacking Interactions

Abstract

Approximately 42 new arene-perfluoroarene compounds were synthesised by the reaction of pentafluorophenyl derivatives (C₆F₅R; R= CN, Br, Cl, I, CHO, CF₃, H) with imidazole, benzimidazole, parazole, indazole and their derivatives such as 2-methylimidazole, 4-methylimidazole, 2-phenylimidazole and 2-methylbenz-imidazole. Attempts to synthesize 1-(2,3,5,6-tetrafluoropyridyl)pyrazole and 1-(2,3,5,6-tetrafluoropyridyl)indazole were unsuccessful. However, these reactions were achieved using different solvents, varying amounts of solvents and varying temperatures. Various chemical analytical techniques, such as NMR spectroscopy, mass spectrometry, infrared spectroscopy, single-crystal X-diffraction and micro-elemental analysis, were used to characterise the compounds. The crystallization of these compounds was performed by the slow evaporation of their solutions in different solvents at ambient temperature. Single crystal structures were obtained for 1-(2,3,5,6- tetrafluoropyridyl)-2-methylbenzimidazole, 1-(4-bromo-2,3,5,6-tetrafluorobenzyl)-3-benzyl-4-methylimidazolium bromide and 1-(2,3,5,6-tetrafluoropyridyl)-3-benzyl-4-methylimidazolium bromide and this result has shown that π-π stacking interactions have an essential role in the packing of these compounds.