(E)-4-[2-(4-Ethoxyphenyl)ethenyl]-1-methylpyridinium naphthalene-2-sulfonate

In the title salt, C16H18NO+·C10H7O3S−, the substituents attached to the central C=C bond adopt a trans conformation and the benzene and pyridinium rings are nearly coplanar, making a dihedral angle of 6.01 (9)°. The crystal structure features weak C—H⋯O hydrogen bonds and C—H⋯π interactions .

In the title salt, C 16 H 18 NO + ÁC 10 H 7 O 3 S À , the substituents attached to the central C C bond adopt a trans conformation and the benzene and pyridinium rings are nearly coplanar, making a dihedral angle of 6.01 (9) . The crystal structure features weak C-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á interactions .

Related literature
The title compound was synthesized as part of a search for materials with non-linear optical properties, see: Okada et al. (1990); Yang et al. (2007). For the synthesis of the pyridinium precursor, see: Okada et al. (1990). For related compounds, see: Ruiz et al. (2006);Murugavel et al. (2009 Table 1 Hydrogen-bond geometry (Å , ).

D-HÁ
Data collection: APEX2 (Bruker, 2004); cell refinement: APEX2 and SAINT (Bruker, 2004); data reduction: SAINT and XPREP The title compound was synthesized in the search for materials with non-linear optical properties (Okada et al., 1990;Ruiz et al., 2006;Yang et al., 2007). In the title compound, C 16 H 18 NO + .C 10 H 7 O 2 S -, the pyridinium and benzene rings in the cation make a dihedral angle of 6.01 (9)°. This cation possess trans configuration, which can be confirmed from the torsion angle C6-C7-C8-C9, -177.8 (2)°. The C7═C8 group links the benzene and pyridinium rings, with a characteristic bond length of 1.329 (3) Å. These features are similar to those found in related compounds (Ruiz et al., 2006;Murugavel et al., 2009). All deviations from expected values for bond lengths are within ca. 0.05 Å. The ethoxy group has C1 and O1 atoms slightly deviated from the mean plane of the benzene ring, by 0.130 (2) and 0.015 (2) Å, respectively. The anion and cation are placed almost perpendicular each to other, the mean planes making an angle of 81.72 (6) Å.
Regarding the crystal packing, weak C-H···O hydrogen bonds and C-H···π interactions are stabilizing the crystal structure. The inter and intramolecular C-H···O interactions are formed mainly in cation-anion and anion-anion pairs.

4-[2-
(4-Ethoxy-phenyl)-vinyl-pyridinium iodide was obtained by condensation reaction between 1,4-dimethyl pyridinium iodide, which was prepared from 4-methylpyridine and methyl iodide, and 4-ethoxybenzaldehyde (all were taken in an equimolar ratio) in the presence of piperidine added as a catalyst. The solution was refluxed for 5 h, yielding the expected pyridinium salt after filtration (Okada et al., 1990). Then the iodide salt was dissolved in water (20 ml) and aqueous sodium 2-naphthalenesulfonate was added. A yellow precipitate was formed, which was filtered off and dried in an oven at 413 K for 1 h (Ruiz et al., 2006). Single crystals suitable for X-ray diffraction were obtained by successive recrystallization (three times) from a methanol/water (8:2 v/v) mixture.

Refinement
H atoms were placed in calculated positions and allowed to ride on their parent atoms, with C-H distances in the range 0.93-0.97 Å and with U iso (H) = 1.2U eq (parent C) for CH and CH 2 groups, and U iso (H) = 1.5U eq (parent C) for methyl groups.