(E)-2-[4-(Diethylamino)styryl]-1-methylpyridinium 4-methoxybenzenesulfonate monohydrate

In the cation of the title compound, C18H23N2 +·C7H7O4S−·H2O, one ethyl group of the diethylamino unit is disordered over two sets of sites in a 0.665 (6):0.335 (6) ratio. The styrylpyridinium unit is nearly planar, with a dihedral angle between the pyridinium and benzene rings of 4.27 (8)°. In the crystal, the anion ring is almost perpendicular to the aromatic rings of the cation; the sulfonate-substituted benzene ring forms dihedral angles of 89.60 (8) and 89.37 (8)°, respectively, with the pyridinium and benzene rings of the cation. In the crystal, the three components are linked into a three-dimensional network by O—H⋯O and C—H⋯O hydrogen bonds. π–π interactions with centroid–centroid distances of 3.6999 (9) and 3.7106 (9) Å are also present.

In the cation of the title compound, C 18 H 23 N 2 + ÁC 7 H 7 O 4 S À Á-H 2 O, one ethyl group of the diethylamino unit is disordered over two sets of sites in a 0.665 (6):0.335 (6) ratio. The styrylpyridinium unit is nearly planar, with a dihedral angle between the pyridinium and benzene rings of 4.27 (8) . In the crystal, the anion ring is almost perpendicular to the aromatic rings of the cation; the sulfonate-substituted benzene ring forms dihedral angles of 89.60 (8) and 89.37 (8) , respectively, with the pyridinium and benzene rings of the cation. In the crystal, the three components are linked into a threedimensional network by O-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds.interactions with centroid-centroid distances of 3.6999 (9) and 3.7106 (9) Å are also present.

Experimental
Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 For a long time, quaternary ammonium compounds (QACs) have been used as disinfectants in both medical and domestic purposes due to their low toxicity and wide-ranging antimicrobial properties (Domagk, 1935). We have during the course of our research reported on the synthesis and antibacterial activity of pyridinium derivatives .
The title compound (I) was synthesized and tested for antibacterial activity. Our antibacterial assay showed that (I) exhibits moderate activity against Pseudomonas aeruginosa with the MIC value of 37.5 µg/ml. Herein its crystal structure is reported.

Experimental
A solution of 2-[(E)-4-(diethylamino)styryl]-1-methylpyridinium iodide (0.13 g, 0.33 mmol) (Kaewmanee et al., 2010) in hot methanol (20 ml) was mixed with a solution of silver(I) 4-methoxybenzenesulfonate (0.10 g, 0.33 mmol) in hot methanol (20 ml). The mixture immediately yielded a grey precipitate of silver iodide. After stirring the mixture for 30 min, the precipitate of silver iodide was removed and the resulting solution was evaporated yielding a deep orange solid.

supplementary materials
Orange 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 (m.p. 421-423 K).

Refinement
All H atoms were positioned geometrically and allowed to ride on their parent atoms, with O-H = 0.89 and 0.99 Å, C-H = 0.93 Å for aromatic and CH and 0.96 Å for CH 3 atoms. The U iso (H) 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. One ethyl unit of the diethylamino is disordered over two sites with refined site occupancies of 0.665 (6) and 0.335 (6).

Figure 1
The asymmetric unit of the title compound, showing 30% probability displacement ellipsoids and the atom-numbering scheme. Open bonds show the minor component.  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 > σ(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.