Crystal structures of two stilbazole derivatives: bis{(E)-4-[4-(diethylamino)styryl]-1-methylpyridin-1-ium} tetraiodidocadmium(II) and (E)-4-[4-(diethylamino)styryl]-1-methylpyridin-1-ium 4-methoxybenzenesulfonate monohydrate

The title molecular salts are stilbazole, or 4-styrylpyridine, derivatives in which the cation has a methyl group attached to the pyridine ring N atom and a diethyl amine group attached to the benzene ring. In salt (I), the cadmium atom of the [CdI4]2− dianion is located on a twofold rotation axis and the compound crystallizes with one cation in the asymmetric unit. In salt(II), the anion consists of a 4-methoxybenzenesulfonate ion, and it crystallizes as a monohydrate.


Chemical context
Stilbene-based compounds have been reported to possess a wide range of biological applications including antibacterial (Chanawanno et al., 2010) and antioxidant (Frombaum et al., 2012) activities. The antibacterial activities of a series of pyridine stilbene benzenesulfonates have been studied against both gram-positive and gram-negative bacteria (Chanawanno et al., 2010). Pyridine and its derivatives play an important role in drugs including antiviral, antifungal, antibacterial, antiinflammatory, antimicrobial, anticancer, antioxidant and antidiabetic agents (Ghattas et al., 2017). They have a variety of biological activities and a number of such compounds are in clinical use (Altaf et al., 2015). The antibacterial activity of pyridinium derivatives have also been studied (Chanawanno et al., 2010). The title salts, bis[(E)-4-[4-(diethylamino)styryl]-1-methylpyridin-1-ium] tetraiodidocadmate (I) and (E)-4-[4-(diethylamino)styryl]-1-methylpyridin-1-ium 4-methoxybenzenesulfonate monohydrate (II) were tested for the level of cytotoxicity and anticancer analysis on normal VERO and MCF-7 cells. From an MTT assay it was found that the ISSN 2056-9890 reported compounds have IC50 values of 31.2 mg mL À1 and 125 mg mL À1 , respectively, against MCF-7 cell lines, whereas the IC50 value of crystals against normal VERO cells was found to be 1000 mg mL À1 . This shows that both compounds exhibit very good anticancer activity, which implies that they may be suitable for biomedical applications.
cations by a number of C-HÁ Á ÁO hydrogen bonds, forming slabs lying parallel to the ab plane (  Wang et al., 2000) it is ca 8.77 . The corresponding dihedral angle in salt (I) is 10.7 (4) . In the crystals of these compounds,stacking interactions dominate, as in the crystal of (I).
There is only one salt reported with the title cation and a sulfonate anion, namely the p-toluenesulfonate monohydrate salt (IBOWIG; Zhou et al., 2004). Here the dihedral angle between the pyridinium and benzene rings in the cation is ca 6.88 , compared to 4.6 (2) in salt (II). The crystal packing is very similar to that of salt (II): a pair of water molecules bridge a pair of p-toluenesulfonate anions via O-HÁ Á ÁO hydrogen bonds, forming an R 2 4 (8) ring motif; these four-membered units are linked to the cations by C-HÁ Á ÁO hydrogen bonds, forming a network structure.

Synthesis and crystallization
Compound (I) (E)-4-[4-(diethylamino)styryl]-1-methyl-pyridinium-iodide (0.788 g, 2 mmol) and cadmium iodide (0.732 g, 2 mmol) were dissolved in a composite solvent, 2:1 ratio of acetonitrile and double-distilled water. The mixture was stirred well at 343 K and then allowed to cool naturally to room temperature. The solution was filtered and the filtrate left for the solvent to slowly evaporate at room temperature. After 3-4 weeks, darkbrown block-like crystals of compound (I) were obtained.
Compound (II) (E)-4-[4-(diethylamino)styryl]-1-methylpyridinium iodide (0.7885 g, 2 mmol) was mixed with sodium 4-methoxybenzenesulfonate (0.418 g, 2 mmol) in distilled water and heated at 373 K for 30 min. The mixture immediately yielded a grey precipitate of sodium iodide. After stirring the mixture for 30 min, the sodium iodide precipitate was removed. The filtrate was left to slowly evaporate and gave a deep-red solid. Red block-like crystals of compound (II), suitable for X-ray diffraction analysis, were obtained by slow evaporation of a solution in methanol after 2-3 weeks.

Refinement
Crystal data, data collection and structure refinement details for salts (I), and (II) are summarized in Table 2. The hydrogen atoms were located in difference electron-density maps. During refinement they were placed in idealized positions and allowed to ride on the parent atoms: C-H = 0.93-0.97Å with U iso (H) = 1.5U eq (C-methyl) and 1.2U eq (C,N) for other H atoms. The rotation angles for the methyl groups were optimized by least-squares. In compound (II), the hydrogen atoms of the water molecule were treated as riding with d(O-H) = 0.85 Å and U iso (H) = 1.5U eq (O).

Bis{(E)-4-[4-(diethylamino)styryl]-1-methylpyridin-1-ium} tetraiodidocadmium(II) (I)
Crystal data (C 18  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.

4-{2-[4-(Diethylamino)phenyl]ethenyl}-1-methylpyridin-1-ium 4-methoxybenzene-1-sulfonate monohydrate (II)
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.30 e Å −3 Δρ min = −0.22 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0075 (14) 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.