(E)-1-(2,4-Dinitrobenzylidene)-2,2-diphenylhydrazine

In the crystal of the title compound, C19H14N4O4, the asymmetric unit consists of two discrete molecules. The C=N bonds in both molecules show an E conformation. The dihedral angles between the C atoms of the 2,4-dinitrobenzene rings and the C=N—N planes are 13.52 (9) and 13.82 (9)° for the two molecules. In the crystal, C—H⋯O hydrogen bonds, mainly between the phenyl ring and the nitro group along the b axis.

In the crystal of the title compound, C 19 H 14 N 4 O 4 , the asymmetric unit consists of two discrete molecules. The C N bonds in both molecules show an E conformation. The dihedral angles between the C atoms of the 2,4-dinitrobenzene rings and the C N-N planes are 13.52 (9) and 13.82 (9) for the two molecules. In the crystal, C-HÁ Á ÁO hydrogen bonds, mainly between the phenyl ring and the nitro group along the b axis. 487 parameters H-atom parameters constrained Á max = 0.14 e Å À3 Á min = À0.20 e Å À3 Table 1 Hydrogen-bond geometry (Å , ). Both A and B molecules show an E configuration on each of the C=N groups with diphenylhydrazine group opposite to 2,4-dinitrophenyl ring, similar to the observed in (E)-1-(4-nitrobenzylidene)-2,2-diphenylhydrazine (Mendoza et al., 2012). The molecule A shows a non planar structure for a phenyl ring next to N-N group, with dihedral angles N1A-N2A-C8A-C9A and N1A-N2A-C14A-C19A of 21.3 (2) and 68.4 (2)° respectively (Table 1) analogously the non planarity structure for a phenyl ring next to N-N group in molecule B is observed by the N1B-N2B-C8B-C9B and N1B-N2B-C14B-C19B dihedral angles of 15.2 (2) and 96.7 (2)° respectively. The N-N average distance [1.3527 Å] is shorter than found in free diphenylhydrazine [1.418 Å] (Clulow et al., 2008) and similar to related structure with 2,4 dinitrophenyl hydrazone group [1.383 (4) Å] (Motherwell & Ramsay, 2007). The dihedral angle for 2,4-dinitrophenyl rings and C=N-N planes are 12.6 (2) and 12.5 (2) ° for molecule A and B respectively. The imine bond distances C7A-N1A 1.2888 (19) Å in molecule A and C7B-N1B 1.293 (2) Å in molecule B are typical for a C=N bond.

Related literature
The crystal packing (Table 1) is stabilized by intermolecular C-H···O contacts.
Experimental 280 mg (1.53 mmol) N,N-diphenylhydrazine was dissolved in ethanol and acetic acid (0.5 ml) was added slowly into this solution while stirring. 300 mg (1.53 mmol) of 2,4-Dinitrobenzaldehyde was added drop by drop into the above solution with strong stirring and the resulting mixture was kept at atmospheric temperature until the solution became dark red transparent. After one hour and a quarter a precipitate appeared. The mixture was separated with filtration in vacuo and the precipitate was washed three times with cold methanol. Recrystallization was performed three times with acetonitrile, to obtain dark red crystals for X-ray analysis. Dark red crystals; yield 78%; m.p.=174-177 °C; UV λ max = 443.36 nm. FT IR (film): (cm -1 ): 3119 n(C-H), 1683, 1600 n(C=N), 1513 n

Refinement
All H atoms were found in a difference map. H atoms were placed in geometrical idealized positions and were refined as riding on their parent atoms, with C-H = 0.93 Å and with U iso (H) = 1.2 U eq (C).

Figure 1
The molecular structure of the title compound. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as circles of arbitrary size.

(E)-1-(2,4-Dinitrobenzylidene)-2,2-diphenylhydrazine
Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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.