(E)-1-(3-Ethoxy-2-hydroxybenzylidene)thiosemicarbazide

The title compound, C10H13N3O2S, crystallizes with two independent molecules (A and B) in the asymmetric unit. In the crystal, the A and B molecules are linked via pairs of N—H⋯O and O—H⋯S hydrogen bonds, forming dimers with R 2 2(14) and R 2 2(6) ring motifs. These dimers are linked via a pair of N—H⋯S hydrogen bonds with an R 2 2(8) ring motif, forming chains propagating along the c-axis direction. The crystal was refined as an inversion twin with a final BASF ratio of 0.54 (11):0.46 (11).

The title compound, C 10 H 13 N 3 O 2 S, crystallizes with two independent molecules (A and B) in the asymmetric unit. In the crystal, the A and B molecules are linked via pairs of N-HÁ Á ÁO and O-HÁ Á ÁS hydrogen bonds, forming dimers with R 2 2 (14) and R 2 2 (6) ring motifs. These dimers are linked via a pair of N-HÁ Á ÁS hydrogen bonds with an R 2 2 (8) ring motif, forming chains propagating along the c-axis direction. The crystal was refined as an inversion twin with a final BASF ratio of 0.54 (11):0.46 (11).

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). Herein, we report on the crystal structure of the new title thiosemicarbazone compound.
The title compound crystallized with two independent molecules (A and B) in the asymmetric unit, Fig. 1. The bond lengths (Allen et al., 1987) and angles are within the normal ranges and are comparable to those observed for related structures (Kargar et al., 2010a,b).
In the crystal, the A and B molecules are linked via pairs of N-H···O and O-H···S hydrogen bonds (Table 1 and Fig. 2) to form dimers, with R 2 2 (14) and R 2 2 (6) ring motifs (Bernstein et al., 1995). These dimers are further linked via a pair of N-H···S hydrogen bonds, with an R 2 2 (8) ring motif, to form chains that extend in direction [0 0 1] (Table 1 and Fig. 2).
The crystal was refined as an inversion twin with a final refined BASF ratio of 0.54 (11)/0.46 (11) for 2232 Friedel pairs.

Experimental
A mixture of 3-ethoxysalicylalehyde (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 initially refined with the O-H and N-H distances restrained to 0.82 (2) and 0.86 (2) Å, respectively. In the final cycles of refinement they were constrained to ride on their parent atoms with U iso (H) = 1.5U eq (O) and 1.2U eq (N), respectively. The C-bound H-atoms were included in calculated positions and treated as riding atoms: C-H = 0.93, 0.96 and 0.97 Å for CH, CH 3 and CH 2 H-atoms, respectively, with U iso (H) = k x U eq (C), where k = 1.5 for CH 3 H-atoms, and k = 1.2 for all other H-atoms. The crystal was refined as an inversion twin with a final refined BASF ratio of 0.54 (11)/0.46 (11) for 2232 Friedel pairs. Fig. 1. The molecular structure of the two independent molecules of the title compound, showing 40% probability displacement ellipsoids and the atomic numbering.

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.