(E)-1-Methyl-4-[2-(1-naphthyl)vinyl]pyridinium 4-chlorobenzenesulfonate

In the title compound, C18H16N+·C6H4ClO3S−, the cation exists in an E configuration with respect to the central C=C bond. The naphthalene ring system is slightly bent, the dihedral angle between the two aromatic rings being 3.71 (14)°. The whole cation is twisted, the dihedral angles between the pyridinium and the two aromatic rings of the naphthalene ring system being 47.44 (14) and 50.81 (14)°. The pyridinium ring and the benzene ring of the anion are inclined to each other at a dihedral angle of 68.21 (13)°. In the crystal structure, the cations and anions are arranged alternately with the cations stacked in an anti-parallel manner along the c axis and the anions linked into chains along the same direction. The cations are linked to the anions by weak C—H⋯O interactions, forming a three-dimensional network. The crystal structure is further stabilized by C—H⋯π interactions and π–π contacts with centroid–centroid distances of 3.6374 (16) and 3.6733 (17) Å. A short Cl⋯O contact [3.108 (2) Å] is also present.

In the title compound, C 18 H 16 N + ÁC 6 H 4 ClO 3 S À , the cation exists in an E configuration with respect to the central C C bond. The naphthalene ring system is slightly bent, the dihedral angle between the two aromatic rings being 3.71 (14) . The whole cation is twisted, the dihedral angles between the pyridinium and the two aromatic rings of the naphthalene ring system being 47.44 (14) and 50.81 (14) . The pyridinium ring and the benzene ring of the anion are inclined to each other at a dihedral angle of 68.21 (13) . In the crystal structure, the cations and anions are arranged alternately with the cations stacked in an anti-parallel manner along the c axis and the anions linked into chains along the same direction. The cations are linked to the anions by weak C-HÁ Á ÁO interactions, forming a three-dimensional network. The crystal structure is further stabilized by C-HÁ Á Á interactions andcontacts with centroid-centroid distances of 3.6374 (16) and 3.6733 (17) Å . A short ClÁ Á ÁO contact [3.108 (2) Å ] is also present.
In the crystal packing (Fig. 2), all O atoms of the sulfonate group are involved in weak C-H···O interactions ( Table   1). The cations and anions are alternately arranged with the cations stacked in an antiparallel manner along the c axis and the anions linked together into chains along the same direction. The cations are linked to the anions by weak C-H···O interactions (Table 1) forming a 3D network. The crystal structure is further stabilized by C-H···π interactions (Table 1).
supplementary materials sup-2 Experimental (E)-1-Methyl-4-(2-(naphthalen-1-yl)vinyl)pyridinium iodide (compound A)(0.22 g, 0.58 mmol) which was prepared according to the previous method  was mixed with silver 4-chlorobenzenesulfonate (Chantrapromma et al., 2007) (0.20 g, 0.58 mmol) in methanol (100 ml) and stirred for 0.5 h. The precipitate of silver iodide which formed was filtered and the filtrate was evaporated to give the title compound as a yellow solid. Yellow needle-shaped single crystals of the title compound suitable for x-ray structure determination were recrystallized from methanol by slow evaporation at room temperature over a few weeks (m.p. 476-477 K).

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 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. The highest residual electron density peak is located at 0.80 Å from S1 and the deepest hole is located at 0.66 Å from C11.
Figures Fig. 1. The molecular structure of the title compound, with 50% probability displacement ellipsoids and the atom-numbering scheme.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq