1-[4-(Dimethylamino)benzylidene]-4-o-tolylthiosemicarbazide

The asymmetric unit of the title compound, C17H20N4S, contains two independent molecules, the main difference between them being the dihedral angles between the benzene rings [19.99 (17) and 9.72 (17)°]. The molecules both have a trans conformation about the C=N double bond and intramolecular C—H⋯S and N—H⋯N hydrogen bonds are observed in both molecules. In the crystal, molecules are linked by weak N—H⋯S hydrogen bonds with graph-set motif R 2 2(8). In each molecule, all but one of the N atoms and both the S atoms are involved in hydrogen bonding.

The asymmetric unit of the title compound, C 17 H 20 N 4 S, contains two independent molecules, the main difference between them being the dihedral angles between the benzene rings [19.99 (17) and 9.72 (17) ]. The molecules both have a trans conformation about the C N double bond and intramolecular C-HÁ Á ÁS and N-HÁ Á ÁN hydrogen bonds are observed in both molecules. In the crystal, molecules are linked by weak N-HÁ Á ÁS hydrogen bonds with graph-set motif R 2 2 (8). In each molecule, all but one of the N atoms and both the S atoms are involved in hydrogen bonding.   Table 1 Hydrogen-bond geometry (Å , ).

Comment
Recently, anions recognition and sensing has attracted growing attentions due to their important roles in the fields of environmental science, biology, catalysis and medicine (Sessler et al. 2006). Substantial progress has been made in the development of anion receptors (Amendola et al. 2006, Gale et al. 2006, Perez & Riera 2008, Amendola et al. 2009, Kowol et al. 2010, Haridas et al. 2012. Thiosemicarbazide has been widely used in catalysis, drug, bacterialcide, flotation agent, (Pouralimardan et al. 2007). Some thiosemicarbazide derivatives show interesting biological effects, such as anticancer and anti-HIV properties (Pandeya et al. 1999;Fahlbusch et al. 2006). There are also a few reports of thiosemicarbazide acting as anion acceptors (Chikate et al. 2005). The introduction of a strong electron-donating group such as the N,N-dimethylanilino group through a double bond imparts new properties that are not commonly observed for the parent thiourea. As part of our work in this area, we report here the synthesis and structure of the title compound.The asymmetric unit of the title compound, C 17 H 20 N 4 S, consists of two crystallographically independent molecules. The main differences of both molecules are the dihedral angles between the benzene rings, 19.99 (17)° and 9.72 (17)°. In the crystal, molecules are linked by weak intermolecular N-H···S hydrogen bonds with set graph-motif R 2 2 (8) (Bernstein et al., 1995). Intramolecular C-H···S and N-H···N hydrogen bonds are observe. In both molecules, all of the N atoms and two of the S atoms are involved in hydrogen bonding, with an average H···S distance of 2.61Å and N-H···S angles in the range 170-171°. The molecules have a trans configuration about the C=N double bond.

Experimental
The title compound was synthesized by refluxing an ethanol solution (20 ml) of 4-(dimethylamino) benzaldehyde (10 mmol) and 4-(4-methylphenyl)-3-thiosemicarbazide (10 mmol) for 3 h. The resulting yellow and clear solution was then cooled to room temperature. Light-yellow crystals were obtained, filtered and washed with cold ethanol. Crystals suitable for X-ray diffraction analysis were obtained by slow evaporation of an acetonitrile and dichromethane mixed solution.

Figure 1
ORTEP plot of the title compound. The thermal ellipsoids are drawn at 30% probability level.

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.