(E)-5-[(2-Hydroxy-5-methoxybenzylidene)amino]-1,3,4-thiadiazole-2(3H)-thione

In the title thione–Schiff base compound, C10H9N3O2S2, the dihedral angle between the benzene ring and the five-membered ring is 6.69 (8)°. An intramolecular O—H⋯N hydrogen bond forms an S 2 2(6) ring. In the crystal, inversion dimers linked by pairs of N—H⋯S interactions occur, generating R 2 2(8) ring motifs. The crystal structure features a S⋯S contact [3.3776 (7) Å], which is significantly shorter than the sum of the van der Waals radii (3.7 Å). The crystal structure also features C—H⋯O and π–π interactions [centroid–centroid distances = 3.4636 (9)–3.808 (1) Å].


Comment
Compounds incorporating a thiadiazole ring have attracted much attention due to their biological activity (Kumar et al., 1988;Yadav et al., 1989). Here we report the crystal structure of a new Schiff base compound containing a thiadiazol ring system.
The asymmetric unit of the title compound, Fig. 1, comprises a thione-Schiff base ligand. The bond lengths (Allen et al., 1987) and angles are within the normal ranges and are comparable to the related structure (Zhang, 2003).

Experimental
The title compound was synthesized by adding 5-methoxy-salicylaldehyde (1 mmol) to a solution of 5-aminothiophene-2thiol (1 mmol) in ethanol (30 ml). The mixture was refluxed with stirring for half an hour. The resultant solution was filtered.
Yellow single crystals of the title compound suitable for X-ray structure determination were recrystallized from ethanol by slow evaporation of the solvents at room temperature over several days.

Refinement
All hydrogen atoms were positioned geometrically with C-H = 0.93-0.96 Å and included in a riding model approximation with U iso (H) = 1.2 or 1.5 U eq (C). A rotating group model was applied to the methyl group.

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.