5-Bromo-2-hydroxybenzaldehyde thiosemicarbazone

The molecule of the title compound, C8H8BrN3OS, is close to being planar, with maximum deviations of −0.127 (3) and 0.135 (5) Å for the N atoms of the –NH– and NH2– groups, respectively. Intramolecular N—H⋯N and O—H⋯N hydrogen bonds to the same acceptor N atom generate S(5) and S(6) ring motifs. In the crystal structure, molecules are connected into [010] chains by pairs of N—H⋯S hydrogen bonds with R 2 2(8) graph-set motifs. The crystal used for data collection was found to be an inversion twin.

The molecule of the title compound, C 8 H 8 BrN 3 OS, is close to being planar, with maximum deviations of À0.127 (3) and 0.135 (5) Å for the N atoms of the -NH-and NH 2 -groups, respectively. Intramolecular N-HÁ Á ÁN and O-HÁ Á ÁN hydrogen bonds to the same acceptor N atom generate S(5) and S(6) ring motifs. In the crystal structure, molecules are connected into [010] chains by pairs of N-HÁ Á ÁS hydrogen bonds with R 2 2 (8) graph-set motifs. The crystal used for data collection was found to be an inversion twin.

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). We here report the crystal structure of the title compound (I).

Experimental
A mixture of 5-bromosalicylalehyde (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 to yield colourless prisms of (I).
Their isotropic displacement parameters were refined with U iso (H) = 1.2U eq (N) for the NH and NH 2 groups and U iso (H) = 1.5U eq (O) for hydroxyl group. The remaining H atoms were placed in idealized positions and allowed to ride on their parent atoms, with C-H = 0.93 Å, and U iso (H) = 1.2U eq (C). Fig. 1

Special details
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and tor-

sion angles
Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted Rfactors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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.