Crystal structure and Hirshfeld surface analysis of (E)-2-(5-bromo-2-hydroxybenzylidene)hydrazinecarbothioamide dimethyl sulfoxide monosolvate

The molecule of the title Schiff base, has an E conformation with respect to the C=N bond, and a dihedral angle of 14.54 (11)° between the benzene ring and the mean plane of the N—N—C(N)=S hydrazinecarbothioamide unit.

The molecule of the title Schiff base, C 8 H 8 BrN 3 OSÁC 2 H 6 OS, which crystallizes as a dimethyl sulfoxide (DMSO) monosolvate, displays an E configuration with respect to the C N bond, with a dihedral angle of 14.54 (11) between the benzene ring and the mean plane of the N-N-C(N) S unit. In the crystal, molecules are linked by N-HÁ Á ÁO hydrogen bonds, forming chains propagating along the b-axis direction. Within the chains there are R 2 3 (11) ring motifs, which are reinforced by C-HÁ Á ÁO DMSO hydrogen bonds enclosing secondary R 1 2 (6) and R 2 3 (9) loops. The chains are linked by O-H hydroxyl Á Á ÁS hydrogen bonds, forming layers parallel to (011). Inversion-related layers are linked by short BrÁ Á ÁBr interactions [3.5585 (5) Å ], forming slabs parallel to (011). The intermolecular interactions have been investigated using Hirshfeld surface studies and two-dimensional fingerprint plots. The crystal structure of the unsolvated form of the title compound has been reported previously [Kargar et al. (2010). Acta Cryst. E66, o2999], and its solid-state structure is compared with that of the title solvated form.

Chemical context
Schiff bases are nitrogen-containing active organic compounds that play a vital role in enzymatic reactions involving interaction of an enzyme with a carbonyl group of a substrate (Tidwell, 2008). Thiosemicarbazones exhibit interesting pharmacological properties and biological activities. Thiosemicarbazone derivatives have gained special importance because of their role in drug development; for example they are used as antiviral, antitubercular, anti-bacterial infection, analgesic and antiallergic agents and in the treatment of central nervous system disorders and as sodium channel blockers and show antitumorous activity. The pharmacological versatility of semicarbazones, thiosemicarbazones and their metal complexes have been reviewed by Beraldo & Gambino (2004).
Thiosemicarbazones are formed by the condensation of thiosemicarbazides with aldehydes or ketones (Sriram et al., 2006;Scovill et al., 1982). They are also used in most branches of chemistry, for example, as dyes, photographic films, plastics and in the textile industry. These types of compounds also act as ligands for a variety of transition metals, often as high propensity multi-dentate chelating agents (Al-Karawi et al., 2009). Herein, we report on the crystal structure of the title thiosemicarbazone that crystallizes as a dimethyl sulfoxide monosolvate. The crystal structure of the unsolvated form of the title Schiff base has been reported previously (Kargar et
In the molecular structure of the unsolvated form of the title compound (Kargar et al., 2010a), an intramolecular O-HÁ Á ÁN hydrogen bond is present enclosing an S(6) ring motif. Comparing the two molecules, as shown in the structural overlay of Fig. 2, it can be seen that the benzene ring of the title solvated compound is rotated by ca. 180 with respect to that in the unsolvated form of the molecule. The bond lengths and bond angles of the two molecules are similar. In the title compound, the dihedral angle between the benzene ring and the mean plane of the N-N-C(N) S hydrazinecarbothioamide unit is 14.54 (11) compared to ca 7.05 in the unsolvated phase. Kargar et al. (2010b) have also reported the crystal structure of the unsolvated chloro-substituted analogue. This molecule has the same conformation as the unsolvated bromo-substituted analogue (Kargar et al., 2010a), but in contrast it crystallizes in the monoclinic space group P2 1 /c, while the unsolvated bromo compound crystallizes in the chiral orthorhombic space group P2 1 2 1 2 1 .   Table 1 Hydrogen-bond geometry (Å , ). Symmetry codes: (i) x À 1; y þ 1; z; (ii) x þ 1; y; z; (iii) x; y À 1; z; (iv) x þ 1; y À 1; z.

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

Hirshfeld surface analysis
The three-dimensional d norm surface is a useful tool to analyse and visualize the inter-molecular interactions. d norm takes negative or positive values depending on whether the intermolecular contact is shorter or longer than the van der Waals radii (Spackman & Jayatilaka, 2009;McKinnon et al., 2007). The three-dimensional d norm surface of the title compound is shown in Fig. 6 A partial view, almost normal to the (011) plane, of the hydrogen-bonded chain (dashed lines; see Table 1) propagating along the [010] direction. In this and subsequent figures, only the H atoms involved in hydrogen bonding have been included.

Figure 4
A view, almost normal to (011), of the hydrogen-bonded sheets parallel to (011). The hydrogen bonds are shown as dashed lines and details are given in Table 1.

Figure 5
A view along the b axis of the crystal packing of the title compound. The hydrogen bonds (see Table 1) and the short BrÁ Á ÁBr interactions are shown as dashed lines.

Figure 6
Hirshfeld surfaces mapped over d norm for the title compound.

Synthesis and crystallization
The title compound was synthesized by refluxing for 8 h a 1:1 molar ratio of a hot ethanolic solution (20 ml) of thiosemicarbazide (0.091 mg, Aldrich) and a hot ethanolic solution of 5-bromosalicylaldehyde (0.196 mg, Aldrich). The solution was then cooled and kept at room temperature. The precipitate that formed was filtered off and recrystallized from dimethyl sulfoxide. Colourless block-like crystals, suitable for the X-ray analysis, were obtained in a few days on slow evaporation of the solvent.

(E)-2-(5-Bromo-2-hydroxybenzylidene)hydrazinecarbothioamide dimethyl sulfoxide monosolvate
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.27 e Å −3 Δρ min = −0.34 e Å −3 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 esds are taken into account in the estimation of distances, angles and torsion angles 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.