2-{[2,8-Bis(tri­fluoro­meth­yl)quinolin-4-yl](hy­droxy)meth­yl}piperidin-1-ium tri­chloro­acetate: crystal structure and Hirshfeld surface analysis

The asymmetric unit of the centrosymmetric title salt, C(17)H(17)F(6)N(2)O(+)·C(2)Cl(3)O(2) (−), comprises a single ion-pair. The hy­droxy-O and ammonium-N atoms lie to the same side of the cation, a disposition maintained by a charge-assisted ammonium-N—H⋯O(hy­droxy) hydrogen bond [the O(h)—C(m)—C(m)–N(a) (h = hy­droxy, m = methine, a = ammonium) torsion angle is 58.90 (19)°]. The piperidin-1-ium group is approximately perpendicular to the quinolinyl residue [C(q)—C(m)—C(m)–N(a) (q = quinolin­yl) is −178.90 (15)°] so that the cation, to a first approximation, has the shape of the letter L. The most prominent feature of the supra­molecular association in the crystal is the formation of chains along the a-axis direction, being stabilized by charge-assisted hydrogen-bonds. Thus, ammonium-N(+)—H⋯O(−)(carboxyl­ate) hydrogen bonds are formed whereby two ammonium cations bridge a pair of carboxyl­ate-O atoms, leading to eight-membered {⋯O⋯HNH}(2) synthons. The resulting four-ion aggregates are linked into the supra­molecular chain via charge-assisted hydroxyl-O—H⋯O(−)(carboxyl­ate) hydrogen bonds. The connections between the chains, leading to a three-dimensional architecture, are of the type C—X⋯π, for X = Cl and F. The analysis of the calculated Hirshfeld surface points to the importance of X⋯H contacts to the surface (X = F, 25.4% and X = Cl, 19.7%) along with a significant contribution from O⋯H hydrogen-bonds (10.2%). Conversely, H⋯H contacts, at 12.4%, make a relatively small contribution to the surface.