The crystal structures of 1-(4-halo-2,3,5,6-tetrafluorophenyl)-3-benzylimidazolium bromides: The relative importance of anion–p, lone pair–p, pp stacking and halogen bonding interactions

The crystal structures of analogous 1-(4-halo-2,3,5,6-tetrafluorophenyl)-3-benzylimidazolium bromide salts have been determined by single crystal X-ray diffraction. All three structures contain similar charge-assisted hydrogen bonding between the acidic hydrogen atoms of the imidazolium ring and bromide anions, but different structures arise because of the relative importance of other interactions, in particular the halogen bonding between bromide and the covalently bonded halogen atoms. 1-(4-Chloro-2,3,5,6-tetrafluorophenyl)-3-benzylimidazolium bromide (1) comprises columns of π-π stacked phenyl and chlorotetrafluorophenyl rings in three almost orthogonal directions, 1-(4-bromo-2,3,5,6-tetrafluorophenyl)-3-benzylimidazolium bromide (2) contains columns of alternating bromotetrafluorophenyl rings and bromide anions displaying anion-π interactions, and 1-(4-iodo-2,3,5,6-tetrafluorophenyl)-3-benzylimidazolium bromide (3) contains columns of alternating iodotetrafluorophenyl rings and iodine atoms displaying lone pair-π interactions.