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

The title compound, C14H11FN4O4, crystallizes with two essentially planar molecules in the asymmetric unit; the dihedral angles between the benzene rings are 1.57 (15) and 6.17 (15)°. In each molecule, an intramolecular N—H⋯O hydrogen bond generates an S(6) ring. In the crystal, molecules are linked by weak C—H⋯O and C—H⋯F interactions into sheets lying parallel to (120). O⋯C [2.980 (4) Å] and O⋯N [2.892 (3) Å] short contacts also occur.


Comment
Hydrazones are well-known biological compounds with antibacterial, antifungal, antitumor, anti-inflammatory as well as antioxidant properties (e.g. Cui et al., 2010). During the course of our search for antioxidant and antityrosinase compounds, the title compound (I) was synthesized in order to study and compare its biological activity with those of related compounds (Chantrapromma et al., 2011;Fun et al., 2011;Nilwanna et al., 2011). Herein we report the synthesis and crystal structure of (I).
In Fig. 1, there are two crystallographic independent molecules A and B in the asymmetric unit of (I) with differences in bond angles. The molecular structure of (I), C 14 H 11 FN 4 O 4 is essentially planar with the the dihedral angle between the 2,4-dinitrophenyl and the 2-fluorophenyl rings being 1.57 (15)° in molecule A and 6.17 (15)° in molecule B. The central ethylidenehydrazine bridge (N2/N1/C7/C14) is statistically planar with the torsion angles N2-N1-C7-C14 = 0.6 (4) and   Table 1) generates S(6) ring motifs (Bernstein et al., 1995) which help to establish the planarity of the molecules. The bond distances are comparable with the related structures (Chantrapromma et al., 2011;Fun et al., 2011 andNilwanna 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. 4-Fluoroacetophenone (0.25 ml, 2 mmol) was then added to the solution with continuous stirring. The solution was stirred for 1 hr yielding an orange solid, which was filtered off and washed with methanol. Orange plates were recrystalized from ethanol by slow evaporation of the solvent at room temperature over several days, Mp. 507-508 K.

Refinement
Amide H atom was located in a Fourier difference map and refined isotrpically. The remainning H atoms were positioned geometrically and allowed to ride on their parent atoms, with d(C-H) = 0.95 Å for aromatic and 0.98 Å for CH 3 atoms. The supplementary materials sup-2 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. Fig. 1. The molecular structure of (I), showing 65% probability displacement ellipsoids. The hydrogen bonds are shown as dashed lines.   Glazer, 1986) operating at 100.0 (1) K.

Figures
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.