4-Amino-3-(4-hydroxybenzyl)-1H-1,2,4-triazole-5(4H)-thione

In the title compound, C9H10N4OS, the dihedral angle between the benzene and 1H-1,2,4-triazole-5(4H)-thione rings is 67.51 (16)°. In the crystal, molecules are liked via N—H⋯O hydrogen bonds, forming chains along the c-axis direction. The chains are linked via O—H⋯S hydrogen bonds, forming corrugated layers lying parallel to the bc plane. The layers are linked via N—H⋯N and N—H⋯S hydrogen bonds, forming a three-dimensional network.

In the title compound, C 9 H 10 N 4 OS, the dihedral angle between the benzene and 1H-1,2,4-triazole-5(4H)-thione rings is 67.51 (16) . In the crystal, molecules are liked via N-HÁ Á ÁO hydrogen bonds, forming chains along the c-axis direction. The chains are linked via O-HÁ Á ÁS hydrogen bonds, forming corrugated layers lying parallel to the bc plane. The layers are linked via N-HÁ Á ÁN and N-HÁ Á ÁS hydrogen bonds, forming a three-dimensional network.

Comment
The chemistry of triazoles has received considerable attention in recent years because of their versatility in the synthesis of many other heterocyclic compounds. 1,2,4-Triazole derivatives are well known for their different biological activities, therefore various 1,2,4-triazole derivatives and their N-bridged heterocyclic analogs have been extensively studied (Holla et al., 2001(Holla et al., ,2006. The derivatives of 1,2,4-triazole are known to exhibit anti-inflammatory (Mullican et al., 1993), antiviral (Jones et al., 1965), antimicrobial (Shams El-Dine et al., 1974Misato et al., 1977) and antidepressant activity (Kane et al., 1988). Hence synthesis of the corresponding heterocyclic compounds could be of interest from the viewpoint of chemical reactivity and biological activity.

Experimental
The synthesis of the title compound is described in Fig. 3. A well triturated mixture of 4-hydroxyphenylacetic acid (0.755 g, 0.005 mol) and thiocarbohydrazide (0.53 g, 0.005 mol) was fused in a round bottom flask for one hour on an oil bath at 413 K. It was cooled to room temperature and washed with sodium bicarbonate (5%) solution to remove unreacted acid and again washed with water. The dried compound was recrystallized from methanol yielding colourless block-like crystals (M.p. 475-477 K).

Refinement
The OH and NH 2 H atoms (H1, and H4A/H4B, respectively) were located in a difference Fourier map and freely refined.

Figure 1
A view of the molecular structure of the title molecule, with atom labelling. The displacement ellipsoids are drawn at the 50% probability level.

Figure 2
A view along the a axis of the crystal packing of the title compound. The hydrogen bonds are shown as dashed lines; see  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.29 e Å −3 Δρ min = −0.27 e Å −3 Absolute structure: Flack (1983), 265 Friedel pairs (15% coverage) Absolute structure parameter: −0.02 (9) 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.