4-(3-Ethoxy-4-hydroxystyryl)-1-methylpyridinium tosylate monohydrate

In the title compound, C16H18NO2 +·C7H7O3S−·H2O, the dihedral angle between the pyridyl and benzene rings of the pyridinium cation is 0.2 (1)°. The benzene ring of the tosylate anion makes a dihedral angle of 4.8 (2)° with the best mean plane of the pyridinium cation. The pyridinium cation and the tosylate anion are hydrogen bonded to the water molecule, and the crystal packing is further stabilized by intermolecular C—H⋯O and π–π interactions [centroid–centroid separations of 3.648 (3) and 3.594 (2) Å.

In the title compound, C 16 H 18 NO 2 + ÁC 7 H 7 O 3 S À ÁH 2 O, the dihedral angle between the pyridyl and benzene rings of the pyridinium cation is 0.2 (1) . The benzene ring of the tosylate anion makes a dihedral angle of 4.8 (2) with the best mean plane of the pyridinium cation. The pyridinium cation and the tosylate anion are hydrogen bonded to the water molecule, and the crystal packing is further stabilized by intermolecular C-HÁ Á ÁO andinteractions [centroid-centroid separations of 3.648 (3) and 3.594 (2) Å .

Comment
The synthesis and study of molecular compounds with non linear optical (NLO) properties has attracted much attention, because such materials hold promise for applications in optoelectronic and photonic devices (Bosshard et al., 1995;Nalwa & Miyata, 1997). In order to create efficient quadratic (second-order) NLO materials, both the molecular and bulk properties must be optimized. Within the diverse range of existing NLO compounds, styrylpyridinium salts are particularly attractive for device applications (Lee & Kim, 1999). Against this background, and in order to obtain detailed information on molecular conformations in the solid state, X-ray studies of the title compounds (I) have been carried out.
X-Ray analysis confirms the molecular structure and atom connectivity for (I), as illustrated in Fig. 1. The dihedral angle between the pyridyl and phenyl rings of the pyridinium cation is 0.2 (1)°. The benzene ring of the tosylate anion makes a dihedral angle of 4.8 (2)° with the best mean plane of the pyridinium cation. The bond lengths N1-C7, C13-O25 and C14-O26 are normal and comparable with the corresponding values observed in the related structure. (Zhang et al., 1997) The presence of water molecules in the crystal structure of (I) leads to a three dimensional network of hydrogen bonds invoving water, the tosylate anion and the pyridinium cation (Table 1). In addition, the crystal packing is further stabilized by intermolecular C-H···O (Table.1) and π-π interactions with a Cg1···Cg1 i and a Cg1-Cg2 ii separation of 3.648 (3) Å and 3.594 Å, respectively ( Fig. 2; Cg1 and Cg2 are the centroids of the N/C1-C5 pyridine ring and C17-C22 benzene ring, respectively, symmetry code as in Fig. 2).

Experimental
HEST (4-[2-(4-hydroxy-3-ethoxyphenyl) ethenyl]-1-methylpyridinium 4-tolylsulfonate hydrate ) was synthesized by the condensation of 4-methyl N-methyl pyridinum Tosylate, which is prepared from 4-Picoline (Merck, 99%) , methyl toluene sulphonate (Merck, 98%) and 4-hydroxy-3-ethoxy-Benzaldehyde (High Media, 98%) in the presence of piperidine as catalyst. The step by step synthesis procedure of HEST is as follows: Picoline (10.31 ml, 0.105 mol %) and methyl toluene sulphonate (15.88 ml, 0.105 mol %) is added into toluene (200ml) (Merck, 98%) is taken in a round bottom flask (500 ml) of Dean-stark apparatus. This mixture is heated until formation of white salt, which is insoluble in toluene. While boiling Di-methyl formamide (DMF) (Merck, 98%) is added until the white salt are dissolved. Now 4-hydroxy-3-ethoxy-Benzaldehyde (0.105 mol %) is added. Few drops of Piperidine also added as catalyst. The mixture is then refluxed with Dean-stark trap to remove water. After more than equivalent amount of water is collected, the reactants are cooled to room temperature and synthesized orange color HEST is collected. To prevent the absorption of water from the atmosphere, the synthesized material is placed in the oven at 100°C for 1 hour. Purified single crystals suitable for X-ray diffraction was obtained by successive recrystallization process of a methonal solution.
supplementary materials sup-2 Refinement H atoms of the water were located in a difference fourier map, and were refined with distance restraints of O-H = 0.85(0.01) Å and H···H = 1.25(0.01) Å and all other H atoms were fixed geometrically and allowed to ride on their parent atoms, with C-H = 0.93-0.98 Å with U iso (H)= 1.5U eq (methyl H) and 1.2U eq (for other H atoms). Fig. 1. The molecular structure of title compound showing 30% probability displacement ellipsoids.

Special details
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.