(E)-1-(2,4-Dinitrophenyl)-2-[1-(thiophen-2-yl)ethylidene]hydrazine

The molecule of the title compound, C12H10N4O4S, is slightly twisted, with a dihedral angle of 8.23 (9)° between the benzene and thiophene rings. One nitro group is co-planar [O—N—C—C torsion angles = −0.5 (3) and −1.9 (3)°] whereas the other is slightly twisted with respect to the benzene ring [O—N—C—C torsion angles = −5.1 (3) and −5.7 (3)°]. In the crystal, the molecules are linked by weak C—H⋯O interactions into screw chains along the b axis. The molecular conformation is consolidated by an intramolecular N—H⋯O hydrogen bond.


Comment
Hydrazones are an important class of compounds which are used in numerous biological and pharmacological applications as insecticidal, antitumor, antioxidant, antifungal, antibacterial, antiviral and antituberculosis compounds (Bedia et al., 2006;El-Tabl et al., 2008;Ramamohan et al., 1995;Rollas & Küçükgüzel, 2007). Several of them also exhibit good nonlinear optical properties (Baughman et al., 2004). In our previous studies we reported the syntheses and crystal structures of some hydrazone derivatives Fun et al., 2010;Jansrisewangwong et al., 2010). The title compound (I) was synthesized as part of our on going research on biological activities of hydrazones.
In the crystal structure ( Fig. 2), the molecules are linked by C-H···O weak interactions (Table 1) into screw chains along the b axis. The molecular conformation is consolidated by an intramolecular N-H···O hydrogen bonding interaction (Table   1)

Experimental
The title compound was synthesized by dissolving 2,4-dinitrophenylhydrazine (0.40 g, 2 mmol) in ethanol (10 ml) and H 2 SO 4 (conc.) (98%, 0.5 ml) was slowly added with stirring. Then 2-acetylthiophene (0.20 ml, 2 mmol) was added to the solution with continuous stirring. The solution was refluxed for 30 min yielding an orange-red solid, which was filtered off and washed with methanol. Orange block-shaped single crystals of the title compound suitable for X-ray structure determination were recrystalized from ethanol by slow evaporation of the solvent at room temperature over several days. Mp. 516-518 K.

Refinement
The H atom attached to N2 was located in a difference Fourier map and refined isotropically. The remaining H atoms were positioned geometrically and allowed to ride on their parent atoms, with d(C-H) = 0.93 Å for aromatic and 0.96 Å for CH 3 atoms. The U iso values were constrained to be 1.5U eq of the carrier atom for methyl H atoms and 1.2U eq for the remaining supplementary materials sup-2 H atoms. A rotating group model was used for the methyl groups. The highest residual electron density peak is located at 0.97 Å from S1 and the deepest hole is located at 0.67 Å from S1. Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids. The intramolecular hydrogen bond is drawn as dash line.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 120.0 (1) K. 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 Rfactors(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.