(E)-1-(2-Hydroxy-5-methoxybenzylidene)thiosemicarbazide

In the title molecule, C9H11N3O2S, an intramolecular O—H⋯N hydrogen bond generates an S(6) ring motif. In the crystal, molecules are linked via pairs of N—H⋯S interactions, forming inversion dimers with R 2 2(8) ring motifs. These dimers are further linked via N—H⋯S and N—H⋯O hydrogen bonds, forming a two-dimensional network lying parallel to (100). The crystal structure is further stabilized by intermolecular π–π interactions [centroid–centroid distance = 3.7972 (9) Å].


Comment
Thiosemicarbazones constitute an important class of N,S donor ligands due to their propensity to react with a wide range of metals (Casas et al., 2000). Thiosemicarbazones exhibit various biological activities and have therefore attracted considerable pharmaceutical interest (Maccioni et al., 2003;Ferrari et al., 2000). We report herein on the synthesis and crystal structure of the title a hydrazone Schiff base compound.
The asymmetric unit of the title compound, Fig. 1, comprises a hydrazone Schiff base ligand. The bond lengths and angles are within the normal ranges and are comparable to those reported for related structures (Kargar et al., 2010a,b;Adabi et al., 2012). An intramolecular O-H···N hydrogen bond (Table 1) generates an S(6) ring motif (Bernstein et al., 1995).

Experimental
A mixture of 5-methoxysalicylalehyde (0.01 mol) and hydrazinecarbothioamide (0.01 mol) in 20 ml of ethanol was refluxed for about 2 h. On cooling, the solid separated was filtered and recrystallized from ethanol. Colourless plate-like crystals of the title compound, suitable for X-ray diffraction, were obtained by slow evaporation of a solution in ethanol.

Refinement
O-and N-bound H atoms were located in a difference Fourier map and were constrained to ride on their parent atoms: O-H = 0.82 Å, N-H = 0.86 Å, with U iso (H) = 1.5U eq (O) and 1.2U eq (N). The C-bound H-atoms were included in calculated positions and treated as riding atoms: C-H = 0.93 and 0.96 Å for CH and CH 3 H-atoms, respectively, with U iso (H) = k × U eq (C), where k = 1.5 for CH 3 H-atoms, and k = 1.2 for all other H-atoms.

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.