3-Hydroxy-4-methoxybenzaldehyde thiosemicarbazone hemihydrate

The asymmetric unit of the title compound, C9H11N3O2S·0.5H2O, comprises two crystallograpically independent thiosemicarbazone molecules (A and B) and a water molecule of crystallization. In each of the thiosemicarbazone molecules, intramolecular O—H⋯O and N—H⋯N hydrogen bonds form five-membered rings, producing S(5) ring motifs. Intermolecular O—H⋯S and N—H⋯O interactions between molecule B and the water molecule form a six-membered ring, producing an R 2 2(6) ring motif. Intermolecular N—H⋯S hydrogen bonds form dimers involving pairs of both A and B molecules, which form R 2 2(8) ring motifs. The angles between the aromatic ring and thiourea unit in the two molecules are 0.80 (6) and 3.28 (5)°, which proves that each molecule is fairly planar. The crystal structure is stabilized by intermolecular O—H⋯S (×2), O—H⋯O, N—H⋯S (×2) and N—H⋯O (×2) hydrogen bonds and C—H⋯O (×2) contacts to form a three-dimensional network.

The asymmetric unit of the title compound, C 9 H 11 N 3 O 2 SÁ-0.5H 2 O, comprises two crystallograpically independent thiosemicarbazone molecules (A and B) and a water molecule of crystallization. In each of the thiosemicarbazone molecules, intramolecular O-HÁ Á ÁO and N-HÁ Á ÁN hydrogen bonds form five-membered rings, producing S(5) ring motifs. Intermolecular O-HÁ Á ÁS and N-HÁ Á ÁO interactions between molecule B and the water molecule form a six-membered ring, producing an R 2 2 (6) ring motif. Intermolecular N-HÁ Á ÁS hydrogen bonds form dimers involving pairs of both A and B molecules, which form R 2 2 (8) ring motifs. The angles between the aromatic ring and thiourea unit in the two molecules are 0.80 (6) and 3.28 (5) , which proves that each molecule is fairly planar. The crystal structure is stabilized by intermolecular O-HÁ Á ÁS (Â2), O-HÁ Á ÁO, N-HÁ Á ÁS (Â2) and N-HÁ Á ÁO (Â2) hydrogen bonds and C-HÁ Á ÁO (Â2) contacts to form a three-dimensional network.
We report herein the crystal structure of the title compound, (I).
The bond lengths and angles in (I), Fig. 1, agree with those in a related structure (Ferrari et al. 2001). Intramolecular O-H···O and N-H···N hydrogen bonds, in each molecule of A and B, form five-membered rings, producing S(5) ring motifs (Bernstein et al. 1995). The angle between the aromatic ring and the thiourea unit in each of molecule A and B is 0.80 (6) and 3.28 (5)°, respectively, which indicates each molecule is almost planar. Intermolecular O-H···S and N-H···O interactions between molecule B and the water molecule form a six-membered ring, producing a R 2 2 (6) ring motif. Intermolecular N-H···S interactions for pairs of molecule A and similarly for pairs of molecules B lead to the formation of dimers with R 2 2 (8) ring motifs (Bernstein et al. 1995). The crystal structure is stabilized by intermolecular O-H···S, O-H···O, N-H···S (x 2) and N-H···O (x 2) hydrogen bonds and C-H···O (x 2) contacts, see Table 1. In the 3-D crystal structure the water molecules link neghbouring molecules to form 1-D chains along the b-axis of the unit cell (Fig. 2).
Experimental 3-Hydroxy-4-methoxy benzaldehyde (0.075 mol) and thiosemicarbazone (0.05 mol) were dissolved in a sufficient volume of methanol and the mixture was refluxed for 4 h until the whole volume of the mixture attains a pale-yellow colour. The mixture was then allowed to cool, poured into a beaker and kept aside for evaporation. The resulting crude sample was recrystallized twice from methanol. Pure light-yellow crystals of (I) were then obtained.

Refinement
The H atoms of the water molecule were located from the difference Fourier map and constrained to refine on the parent atom with O-H = 0.85 -0.86 Å, and with U(H) set to 1.5 times U eq (O). The H atoms bound to the remaining O and N atoms were located from a difference Fourier map and refined freely, see Table 1 for distances. The C-bound H atoms were positioned geometrically and refined in the riding model approximation with C-H = 0.93 -0.96 Å, and with U(H) set to 1.2 -1.5 times U eq (C). The rotating group model was applied to the methyl groups.   as those based on F, and R-factors based on ALL data will be even larger.