Crystal structure of (2Z,5Z)-3-(4-methoxyphenyl)-2-[(4-methoxyphenyl)imino]-5-[(E)-3-(2-nitrophenyl)allylidene]-1,3-thiazolidin-4-one

The thiazole ring of the title compound is twisted with respect to the three benzene rings, making dihedral angles of 25.52 (12), 85.77 (12) and 81.85 (13)°.

In the title compound, C 26 H 21 N 3 O 5 S, the thiazole ring is nearly planar with a maximum deviation of 0.017 (2) Å , and is twisted with respect to the three benzene rings, making dihedral angles of 25.52 (12), 85.77 (12) and 81.85 (13) . In the crystal, weak C-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á interactions link the molecules into a three-dimensional supramolecular architecture. Aromatic stacking is also observed between the parallel nitrobenzene rings of neighbouring molecules, the centroid-to-centroid distance being 3.5872 (15) Å .

Chemical context
Heterocycles containing a thiazole ring are found to exhibit a wide spectrum of biological activities (Gautam et al., 2015;Asif, 2015;Abhinit et al., 2009). The thiazolidinones that are used widely in medication are derived from thiazolidines containing sulfur and nitrogen in a five-membered ring (Meera et al., 2014;Nowaczyk et al., 2014;Toubal et al., 2012). Knowledge of the crystal structures of these compounds is crucial for understanding the related biological phenomena (Singh et al., 1981;Ameta et al., 2014;Gouda et al., 2011). As part of our studies in this area, we herein report the synthesis and crystal structure of the title compound. ISSN 2056-9890

Structural commentary
The molecular structure with atomic numbering scheme for the title compound is given in Fig. 1 (Bhagavan, 2002), indicating that the thiazole moiety is an effective electron-conjugated substructure. The C-S bond lengths in the thiazol rings [S1-C10 = 1.753 (3) and S1-C12 = 1.777 (2) Å ] are consistant with the normal Csp 2 -S single bond length of 1.76 Å (Sarkar et al., 1984). The C16-O4 bond length [1.365 (3) Å ] and C22-O5 bond length [1.375 (3) Å ] are notably shorter than the normal O-C single bond (1.427 Å ) (Rong Wan et al., 2008), indicating that the p orbital occupied lone pair electrons of the oxygen atom in CH 3 O and the orbital in the benzene ring has p-conjugation. The shorter bond length of C26-O5 [1.385 (5) Å ] might be also caused by the delocalized electron density of the conjugated benzene ring. The C25-O4 [1.431 (3) Å ] bond length is normal for a C-O single bond.

Supramolecular features
In the crystal, weak C-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á interactions (Table 1, Fig. 2) link the molecules into a threedimensional supramolecular architecture.stacking is also observed between the nearly parallel benzene rings of neighbouring molecules, the centroid-to-centroid distance being 3.5872 (15) Å .

Synthesis and crystallization
The synthesis of the title compound was performed according to the scheme in Fig. 3. To a solution of 3 (0.01 mol) in 10 mL of acetic acid and three equivalents of anhydrous sodium acetate was added 2-nitrophenylcinamaldehyde (0.01 mol). The mixture was heated at reflux with stirring, using CH 2 Cl 2 (20 mL) for 4 h. The reaction was monitored by TLC using CH 2 Cl 2 /CH 3 CO 2 C 2 H 5 (9/1) as solvent system. The separated solid was filtered, washed with cold water and dried to give a yellow solid with a moderate yield 75% and melting point 484 K. Single crystals of the title compound suitable for X-ray diffraction were obtained from an ethanol solution.  57, 114.85, 122.34, 125.22, 126.37, 127.35, 127.99, 128.50, 129.20, 129  The molecular structure of the title compound showing the atomnumbering scheme. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
The crystal packing diagram showingstacking between the nitrobenzene rings of the neighbouring molecules. Table 1 Hydrogen-bond geometry (Å , ).
Cg3 is the centroid of the C13-C18 ring.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms in the title compound were placed in calculated positions (C-H = 0.96-1.08 Å ) and allowed to ride on their parent atoms with U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) for other H atoms.