Bis(mefloquinium) butane-dioate ethanol monosolvate: crystal structure and Hirshfeld surface analysis

The asymmetric unit of the centrosymmetric title salt solvate, 2C₁₇H₁₇F₆N₂O⁺· C₄H₄O₄ ^2-·CH₃CH₂OH, (systematic name: 2-{[2,8-bis-(tri-fluoro-meth-yl)quinolin-4-yl](hy-droxy)meth-yl}piperidin-1-ium butane-dioate ethanol monosolvate) comprises two independent cations, with almost superimposable conformations and each approximating the shape of the letter L, a butane-dioate dianion with an all-trans conformation and an ethanol solvent mol-ecule. In the crystal, supra-molecular chains along the a-axis direction are sustained by charge-assisted hy-droxy-O-H⋯O(carboxyl-ate) and ammonium-N-H⋯O(carboxyl-ate) hydrogen bonds. These are connected into a layer via C-F⋯π(pyrid-yl) contacts and π-π stacking inter-actions between quinolinyl-C₆ and -NC₅ rings of the independent cations of the asymmetric unit [inter-centroid separations = 3.6784 (17) and 3.6866 (17) Å]. Layers stack along the c-axis direction with no directional inter-actions between them. The analysis of the calculated Hirshfeld surface reveals the significance of the fluorine atoms in surface contacts. Thus, by far the greatest contribution to the surface contacts, i.e. 41.2%, are of the type F⋯H/H⋯F and many of these occur in the inter-layer region. However, these contacts occur at separations beyond the sum of the van der Waals radii for these atoms. It is noted that H⋯H contacts contribute 29.8% to the overall surface, with smaller contributions from O⋯H/H⋯O (14.0%) and F⋯F (5.7%) contacts.