4-Hydroxy-3-methoxybenzaldehyde thiosemicarbazone

In the title compound, C9H11N3S, there is an intramolecular O—H⋯O hydrogen bond involving the OH group and the adjacent methoxy O atom. The molecule is essentially planar, with the maximum deviation from the mean plane of the non-H atoms being 0.1127 (14) Å for the methyl C atom. In the crystal, molecules are connected via centrosymmetric pairs of N—H⋯S and O—H⋯O hydrogen bonds into a two-dimensional network parallel to (10-3).

In the title compound, C 9 H 11 N 3 S, there is an intramolecular O-HÁ Á ÁO hydrogen bond involving the OH group and the adjacent methoxy O atom. The molecule is essentially planar, with the maximum deviation from the mean plane of the non-H atoms being 0.1127 (14) Å for the methyl C atom. In the crystal, molecules are connected via centrosymmetric pairs of N-HÁ Á ÁS and O-HÁ Á ÁO hydrogen bonds into a twodimensional network parallel to (103).

Comment
Thiosemicarbazone derivatives have a wide range of pharmacological properties. For example, benzaldehyde-thiosemicarbazone derivatives show in vitro antimalarial and antitubercular activity (Khanye et al., 2011). As part of our study on the synthesis of thiosemicarbazone derivatives, we report herein the crystal structure of 4-hydroxy-3-methoxybenzaldehyde thiosemicarbazone. In the title compound ( Fig. 1), in which the molecular structure matches the asymmetric unit, the maximal deviation from the least squares plane through all non-hydrogen atoms amount to 0.1127 (14) Å for C7. The molecule shows a trans conformation for the atoms about the C8-N1/N1-N2/N2-C9/ bonds. This conformation is also observed in the literature for an isomer of the title compound (Hao, 2010). The mean deviations from the least squares planes for the C1-C8/O1-O2 and C9/N1-N3/S1 fragments amount to 0.0733 (12) Å for C7 and 0.0188 (10) Å for N2, respectively, and the dihedral angle between the two planes is 5.08 (6)°.

Experimental
The starting materials were commercially available and were used without further purification. The 4-hydroxy-3-methoxybenzaldehyde thiosemicarbazone synthesis was adapted from a procedure reported previously (Freund & Schander, 1902). The hydrochloric acid catalyzed reaction of vanillin (8.83 mmol) and thiosemicarbazide (8.83 mmol) in ethanol (50 ml) was refluxed for 6 h. After cooling and filtering, the title compound was obtained. Crystals suitable for X-ray diffraction were obtained from the reaction mixture by the slow evaporation of solvent.

Refinement
All H atoms were were positioned with idealized geometry (methyl and O-H H atoms allowed to rotate but not to tip) and were refined as isotropic with U iso (H) = 1. SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).  Molecular structure of the title compound with labeling and displacement ellipsoids drawn at the 70% probability level.

Figure 2
Crystal structure of the title compound with hydrogen bonds shown as dashed lines.

4-Hydroxy-3-methoxybenzaldehyde thiosemicarbazone
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.32 e Å −3 Δρ min = −0.27 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.055 (15) Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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.