2-[(E)-2-(4-Ethoxyphenyl)ethenyl]-1-methylpyridinium 4-chlorobenzenesulfonate monohydrate

In the title compound, C16H18NO+·C6H4ClO3S−·H2O, the cation exists in an E configuration with respect to the ethenyl bond and is slightly twisted with a dihedral angle of 9.85 (5)° between the pyridinium and the benzene rings. The anion is inclined to the cation with the dihedral angles between the benzene ring of the anion and the pyridinium and benzene rings of the cation of 78.33 (6) and 68.73 (6)°, respectively. In the crystal, the cations and anions are arranged alternately into head-to-head ribbons along the c axis, with the cationic ribbons stacked along the b axis. The crystal is consolidated by O—H⋯O hydrogen bonds, weak C—H⋯O and C—H⋯π interactions. π–π interactions with centroid–centroid distances of 3.6111 (7) and 3.6466 (7) Å are also observed.

In the title compound, C 16 H 18 NO + ÁC 6 H 4 ClO 3 S À ÁH 2 O, the cation exists in an E configuration with respect to the ethenyl bond and is slightly twisted with a dihedral angle of 9.85 (5) between the pyridinium and the benzene rings. The anion is inclined to the cation with the dihedral angles between the benzene ring of the anion and the pyridinium and benzene rings of the cation of 78.33 (6) and 68.73 (6) , respectively. In the crystal, the cations and anions are arranged alternately into head-to-head ribbons along the c axis, with the cationic ribbons stacked along the b axis. The crystal is consolidated by O-HÁ Á ÁO hydrogen bonds, weak C-HÁ Á ÁO and C-HÁ Á Á interactions.interactions with centroid-centroid distances of 3.6111 (7) and 3.6466 (7) Å are also observed.
In continuing our on-going research on biologically-active quaternary ammonium compounds Chantrapromma et al., 2010), the title pyridinium derivative (I) was synthesized. Our results show that (I) is moderately active against the MRSA with the MIC value = 75 µg/ml, whereas it is inactive against susceptible Staphylococcus aureus.
Herein we report the crystal structure of (I).
In the title compound ( Fig. 1), the cation exists in an E configuration with respect to the ethenyl bond [torsion angle C5-C6-C7-C8 = 179.53 (11)°]. The cation is slightly twisted with a dihedral angle between the N1/C1-C5 pyridinium and C8-C13 benzene rings of 9.85 (5)°. The ethoxy group is slightly twisted from the mean plane of the attached benzene ring with the torsion angle C11-O1-C14-C15 = -174.84 (10)°. The 4-chlorobenzenesulfonate anion is inclined to the cation as indicated by the dihedral angles between the benzene ring of the anion and the pyridinium and benzene rings of the cation of 78.33 (6) and 68.73 (6)°, respectively. The water molecule forms an O-H···O hydrogen bond with the anion (Table 1).
Bond distances in (I) have normal values (Allen et al., 1987) and are comparable to those observed in a related structure .

Experimental
The title compound was prepared according to our reported procedure . Yellow block-shaped single crystal 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. M. p. 458-459 K.

Refinement
All H atoms were positioned geometrically and allowed to ride on their parent atoms, with d(O-H) = 0.82 and 0.91 Å, d(C-H) = 0.93 Å for aromatic and CH 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 supplementary materials sup-2 groups. The highest residual electron density peak is located at 0.60 Å from atom C4 and the deepest hole is located at 0.53 Å from atom S1. Fig. 1. The molecular structure of the title compound, with 50% probability displacement ellipsoids and the atom-numbering scheme. Hydrogen bond was shown as dashed line.

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.