2-Hydroxy-4-methoxybenzaldehyde thiosemicarbazone

The title Schiff base compound, C9H11N3O2S, was prepared by the reaction of equimolar quantities of 2-hydroxy-4-methoxybenzaldehyde with thiosemicarbazide in methanol. The molecule adopts a trans configuration with respect to the azomethine group and an intramolecular O—H⋯N hydrogen bond generates an S(6) ring. In the crystal structure, molecules are linked through intermolecular N—H⋯O and N—H⋯S hydrogen bonds, forming a three-dimensional network.

The title Schiff base compound, C 9 H 11 N 3 O 2 S, was prepared by the reaction of equimolar quantities of 2-hydroxy-4-methoxybenzaldehyde with thiosemicarbazide in methanol. The molecule adopts a trans configuration with respect to the azomethine group and an intramolecular O-HÁ Á ÁN hydrogen bond generates an S(6) ring. In the crystal structure, molecules are linked through intermolecular N-HÁ Á ÁO and N-HÁ Á ÁS hydrogen bonds, forming a three-dimensional network.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: HB5575).

Comment
As a continuation of our structural studies of Schiff bases (Hao, 2010), in this paper, the title new Schiff base compound, (I), Fig. 1, is reported.
The molecule of the title compound adopts a trans configuration with respect to the azomethine group. All the bond lengths are within normal values (Allen et al., 1987). There is an intramolecular O-H···N hydrogen bond (Table 1) in the molecule. In the crystal structure, molecules are linked through intermolecular N-H···O and N-H···S hydrogen bonds (Table 1), forming a 3D network (Fig. 2).
Experimental 2-Hydroxy-4-methoxybenzaldehyde (0.1 mmol, 15.2 mg) and thiosemicarbazide (0.1 mmol, 9.1 mg) were refluxed in a 30 ml methanol solution for 30 min to give a clear colorless solution. Colorless blocks of (I) were formed by slow evaporation of the solvent over several days at room temperature.

Refinement
H2, H3A and H3B were located from a difference Fourier map and refined isotropically, with the N-H and H···H distances restrained to 0.90 (1) Å and 1.53 (2) Å, respectively, and with U iso restrained to 0.08Å 2 . Other H atoms were constrained to ideal geometries, with d(C-H) = 0.93-0.96Å, d(O-H) = 0.82Å, and with U iso (H) = 1.2U eq (C) and 1.5U eq (O1 and C7). Fig. 1. The molecular structure of the title compound with 30% probability ellipsoids. Intramolecular hydrogen bond is drawn as a dashed line.

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 supplementary materials sup-3 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.
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )