Abstract
In the racemic title mol-ecular salt, C17H17F6N2O+·C2ClF2O3- (systematic name: 2-{[2,8-bis-(tri-fluoro-meth-yl)quinolin-4-yl](hy-droxy)meth-yl}piperidin-1-ium chloro-difluoro-acetate), the cation, which is protonated at the piperidine N atom, has the shape of the letter, L, with the piperidin-1-ium group being approximately orthogonal to the quinolinyl residue [the Cq-Cm-Cm-Na (q = quinolinyl; m = methine; a = ammonium) torsion angle is 177.79 (18)°]. An intra-molecular, charge-assisted ammonium-N-H⋯O(hydrox-yl) hydrogen bond ensures the hy-droxy-O and ammonium-N atoms lie to the same side of the mol-ecule [Oh-Cm-Cm-Na (h = hydrox-yl) = -59.7 (2)°]. In the crystal, charge-assisted hydroxyl-O-H⋯O-(carboxyl-ate) and ammonium-N+-H⋯O-(carboxyl-ate) hydrogen bonds generate a supra-molecular chain along [010]; the chain is consolidated by C-H⋯O inter-actions. Links between chains to form supra-molecular layers are of the type C-Cl⋯π(quinolinyl-C6) and the layers thus formed stack along the a-axis direction without directional inter-actions between them. The analysis of the calculated Hirshfeld surface points to the dominance of F⋯H contacts to the surface (40.8%) with significant contributions from F⋯F (10.5%) and C⋯F (7.0%) contacts.
Highlights
Practical interest in compounds related to the title salt relates to the biological activity of Mefloquine ([2,8-bis(trifluoromethyl)quinolin-4-yl]-piperidin-2-ylmethanol)
This arises when the racemic compound is reacted with HCl: the resulting salt, [(R*,S*)-(2-{[2,8-bis(trifluoromethyl)quinolin-4-yl](hydroxymethyl)piperidin-1-ium chloride is an anti-malarial drug, being effective against the causative agent, Plasmodium falciparum (Maguire et al, 2006)
This aspect of the structure notwithstanding, the hydroxyl-O and ammonium-N atoms lie to opposite sides of the plane through the quinolinyl residue. This is seen in the value of the C2—C3— C12—O1 torsion angle of À20.3 (3) cf. with that of 177.79 (18) for C3—C12—C13—N2. The latter angle indicates the piperidin-1-ium residue is almost perpendicular to the quinolinyl residue with the methylene-C17 group orientated towards the fused-ring system as seen in the gauche C3— C12—C13—C17 torsion angle of À60.7 (3)
Summary
Practical interest in compounds related to the title salt relates to the biological activity of Mefloquine ([2,8-bis(trifluoromethyl)quinolin-4-yl]-piperidin-2-ylmethanol). This arises when the racemic compound is reacted with HCl: the resulting salt, [(R*,S*)-(2-{[2,8-bis(trifluoromethyl)quinolin-4-yl](hydroxymethyl)piperidin-1-ium chloride is an anti-malarial drug, being effective against the causative agent, Plasmodium falciparum (Maguire et al, 2006). Of particular crystallographic interest has been the characterization of a pair of kryptoracemates of mefloquinium salts in recent years (Jotani et al, 2016; Wardell, Wardell et al, 2016). In a continuation of structural studies of Mefloquine derivatives (Wardell et al, 2011; Wardell, Jotani et al, 2016), the crystal and molecular structures of the title salt, (I), isolated from the 1:1 crystallization of racemic Mefloquine and chlorodifluoroacetic acid are described along with an analysis of its calculated Hirshfeld surface. Symmetry codes: (i) x; y À 1; z; (ii) Àx þ 1; Ày þ 1; Àz þ 1; (iii) x; y þ 1; z; (iv) Àx þ 1; y þ 12; Àz þ 12
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