2-[(E)-2-(4-Ethoxyphenyl)ethenyl]-1-methylquinolinium 4-fluorobenzenesulfonate

In the structure of the title salt, C20H20NO+·C6H4FO3S−, the 4-(ethoxyphenyl)ethenyl unit is disordered over two positions with a refined site-occupancy ratio of 0.610 (6):0.390 (6). The cation is nearly planar, the dihedral angle between the quinolinium and benzene rings being 6.7 (4) and 1.7 (7)° for the major and minor components, respectively. The ethoxy group is essentially coplanar with the benzene ring [C—O—C—Cmethy = 177.1 (8) and 177.8 (12)° for the major and minor components, respectively]. In the crystal, cations and anions are linked into chains along the b-axis direction by C—H⋯Osulfonyl weak interactions. These chains are further connected into sheets parallel to (001) by C—H⋯Osulfonyl weak interactions. The chains are also stacked along the a axis through π–π interactions involving the quinolinium and benzene rings [centroid–centroid distances = 3.636 (5) Å for the major component and 3.800 (9) Å for the minor component]. C—H⋯π interactions are also present.

Cg4 and Cg5 are the centroids of the C12B-C17B and C21-C26 rings, respectively. Quinolinium derivatives were reported to possess interesting bioactivities and pharmacological activities (Chanawanno et al., 2010;Hopkins et al., 2005;Musiol et al., 2006;O′Donnell et al., 2010), including non-linear optic properties (Ruanwas et al., 2010). During the course of our research on the antibacterial activity of pyridinium and quinolinium salts, the title quinolinium salt (I) was synthesized in order to study the effect of the anion counter-part on its antibacterial activity because its starting quinolinium iodide salt (Chanawanno et al., 2010) was found to be very active against the methicillin-resistant Staphylococcus aureus with a MIC value of 2.34 µg/ml. Herein the synthesis and crystal structure of (I) are reported.
In the title salt ( Fig. 1), C 20 H 20 NO + .C 6 H 4 FSO 3 -, the 4-(ethoxyphenyl)ethenyl unit is disordered over two positions with a planar with dihedral angles between the N1/C1-C9 quinolinium and C12-C17 benzene rings of 6.7 (4) and 1.7 (7)° for the major A and minor B components, respectively. The ethoxy unit is disordered over two positions in such a way that the major A and minor B components are related by a 180° rotation. Moreover the ethoxy unit is co-planar with the attached benzene ring as indicated by the torsion angles C16-C15-O1-C18 = 2.5 (15)° and C15-O1-C18-C19 = 177.1 (8)° for the major A component. The corresponding values are 180.0 (14) and 177.8 (12)° for the minor B component. Bond distances in both cation and anion have normal values (Allen et al., 1987) and are comparable to those observed in related structures (Chantrapromma et al., 2011;Fun et al., 2010;Ruanwas et al., 2010).

Experimental
The title compound was synthesized by dissolving silver ( (Fun et al., 2010) (0.29 g, 0.71 mmol) in hot methanol (30 ml). The mixture turned yellow and cloudy immediately. After stirring for 0.5 h, the precipitate of silver iodide which formed was filtered and the filtrate was evaporated to give a yellow solid. Yellow plate-shaped single crystals of the title compound suitable for X-ray structure determination were recrystallized from methanol by slow evaporation of the solvent at room temperature after a few weeks.

Refinement
All H atoms were positioned geometrically and allowed to ride on their parent atoms, with d(C-H) = 0.93 Å for aromatic and CH, 0.97 Å for CH 2 and 0.96 Å for CH 3 atoms. The U iso values were constrained to be 1.5U eq of the carrier atom for methyl H atoms and 1.2U eq for the remaining H atoms. A rotating group model was used for the methyl groups. The 4-(ethoxyphenyl)-ethenyl unit is disordered over two sites with refined site occupancies ratio 0.610 (6):0.390 (6).
Similarity and simulation restraints were applied.

Figure 1
The structure of the title compound showing 50% probability displacement ellipsoids and the atom-numbering scheme.
Open bonds show the minor component.     where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.39 e Å −3 Δρ min = −0.49 e Å −3 Special details Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K. Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.