Self-assembly of cinchonine quaternary salts: Effect of substituents and halogen anions on supramolecular architecture

Four cinchonine quaternary salts organic salts of formulations [C25H34N3O2]+X− (X=Cl (1), Br (2), I (3)), and [C21H26N3O2]+I− (4), have been synthesized and characterized by single crystal X-ray diffraction, elemental analysis, FT-IR, 1H NMR. Single crystal X-ray diffraction analysis shows that compound 1 is isostructural with 2. 1D supramolecular helix assembled from O–H⋯X− and C–H⋯X− ((X=Cl (1), Br (2)) hydrogen bonds are observed in 1 and 2; however, a two-dimensional (2D) hydrogen bonds grids in 3 due to effect of halogen anions. Compound 4 possesses novel hydrogen-bonded three-dimensional (3D) network, in which unusual 1D hydrogen-bonded organic double-stranded helical chains assembled from wrapping of two single-stranded helical chains around each other via aromatic π–π stacking interactions. The role of the weak C–H⋯X−, C–H⋯O hydrogen bonding and the effects of substituents of quinuclidine and halogen anions on supramolecular architecture have also been discussed.