On the solid state inclusion of tetrabutylammonium cation in the imidazolium/trifluoromethanesulfonate H-bonds network observed in ionic co-crystals

Three co-crystals of tetrabutylammonium and 1-alkyl-3-methylimidazolium bistrifluoromethanesulfonate, where alkyl are: ethyl (co-crystal I), butyl (co-crystal II) or (±)-2-methylbutyl (co-crystal III) have been crystallized by slow evaporation of a chloroform solution. The X-rays diffraction studies on single co-crystals revealed that the three crystalline materials obtained are respectively triclinic ( P 1 ¯ ) for I, monoclinic (P21/c) for II and triclinic ( P 1 ¯ ) for III . In each structure, the tetrabutylammonium cations are included in the H-bonds network that link all the imidazolium cations and trifluoromethanesulfonate anions. The H-bonds occur between the acidic protons of the imidazolium ring and the oxygen atoms of the counter ion. No supramolecular interaction (except obviously electrostatic) is observed between the tetrabutylammonium cations and the trifluoromethanesulfonate anions.