(E)-1-(2,4-Dinitrophenyl)-2-[1-(3-fluorophenyl)ethylidene]hydrazine

The molecule of the title hydrazone derivative, C14H11FN4O4, is nearly planar, with a dihedral angle between the benzene rings of 3.71 (7)°. The central ethylidenehydrazine N—N=C—C plane makes dihedral angles of 5.32 (10) and 9.02 (10)° with the 2,4-dinitro- and 3-fluoro-substituted benzene rings, respectively. An intramolecular N—H⋯O bond generates an S(6) ring motif. In the crystal, molecules are linked by weak C—H⋯O interactions into a sheet parallel to (10-1). The molecules are further stacked along the a axis by π–π interactions with centroid–centroid distances of 3.6314 (9) and 3.7567 (10) Å. A C⋯F short contact [2.842 (3) Å] is observed. The 3-fluorophenyl group is disordered over two orientations with a site-occupancy ratio of 0.636 (3):0.364 (3).

However the title compound (I) which was synthesized for the evaluation of its antioxidant activity by DPPH scavenging (Molyneux, 2004) was found to be inactive. Herein we report the synthesis and crystal structure of (I).
In the molecular structure of (I), C 14 H 11 FN 4 O 4 , the F atoms of the 3-fluorophenyl group is disordered over two positions with the major component A and the minor B component rotated by 180° about the C7-C8 bond and having a refined site-occupancy ratio of 0.636 (3):0.364 (3) (Fig. 1). The molecule is nearly planar with a dihedral angle between the two benzene rings being 3.71 (7)°. The middle ethylidenehydrazine bridge is planar with the torsion angle N2-N1-C7-C14 = 0.8 (2)°. The mean plane through this middle bridge makes dihedral angles of 5.32 (10) and 9.02 (10)° with the 2,4-di-  Table 1) generates an S(6) ring motif (Bernstein et al., 1995). The bond distances are in normal ranges (Allen et al., 1987) and are comparable with the closely related structures Fun et al., 2011Fun et al., , 2012Nilwanna et al., 2011).

Experimental
The title compound (I) was synthesized by dissolving 2,4-dinitrophenylhydrazine (0.40 g, 2 mmol) in ethanol (10.00 ml) and H 2 SO 4 (conc.) (98 %, 0.50 ml) was slowly added with stirring. 3-Fluoroacetophenone (0.25 ml, 2 mmol) was then added to the solution with continuous stirring. The solution was stirred for 1 hr yielding an yellow solid, which was filtered off and washed with methanol. Yellow block-shaped single crystals of the title compound suitable for x-ray structure determination were recrystallized from ethanol by slow evaporation of the solvent at room temperature over several days. M.p. 503-504 K.

Refinement
Amide H atom was located in a Fourier difference 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 H atoms. A rotating group model was used for the methyl groups. The F atom was found to be disordered over two sites in a 0.636 (3): 0.364 (3) occupancy ratio. In the final refinement, distance restraints were used for the disordered C-F bonds.

Figure 1
The molecular structure of the title compound, with 45% probability displacement ellipsoids and the atom-numbering   (Cosier & Glazer, 1986) operating at 100.0 (1) K. Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (