2-Hydroxy-5-nitrobenzaldehyde 2,4-dinitrophenylhydrazone

In the title compound, C13H9N5O7, one of the nitro groups is twisted away from the attached benzene ring by 16.21 (8)°. The dihedral angle between the two benzene rings is 4.63 (1)°. The molecular structure is stabilized by intramolecular N—H⋯O and O—H⋯N hydrogen bonds which generate an S(6) ring motif. The molecules pack as layers parallel to the ab plane; molecules of adjacent layers are linked into chains along the [101] direction through N—H⋯O hydrogen bonds.

In the title compound, C 13 H 9 N 5 O 7 , one of the nitro groups is twisted away from the attached benzene ring by 16.21 (8) . The dihedral angle between the two benzene rings is 4.63 (1) . The molecular structure is stabilized by intramolecular N-HÁ Á ÁO and O-HÁ Á ÁN hydrogen bonds which generate an S(6) ring motif. The molecules pack as layers parallel to the ab plane; molecules of adjacent layers are linked into chains along the [101] direction through N-HÁ Á ÁO hydrogen bonds.

Comment
Phenylhydrazone derivatives have been synthesized in order to investigate their structures and analytical applications.
2,4-Dinitrophenylhydrazones play an important role as stabilizers for the detection, characterization and protection of the carbonyl group of compounds than phenylhydrazones (Niknam et al., 2005). 2,4-Dinitrophenylhydrazone derivatives are widely used in various forms of analytical chemistry (Lamberton et al., 1974;Zegota, 1999;Cordis et al., 1998;Zlotorzynska & Lai, 1999) and are also used as dyes (Guillaumont & Nakamura, 2000). They are also found to have versatile coordinating abilities towards different metal ions (Raj et al., 2006). In addition, they are used to determine airborne aldehydes and ketones (Vogel et al., 2000) and as detectors of formaldehyde (Hanoune et al., 2006). These compounds can exist as E and Z stereoisomers (Uchiyama et al., 2003). Their existence as a keto tautomer in the solid state with an E configuration across the C-N bond have been reported (Fun et al., 1996). The title compound, whose structure is reported here, is one of the series of phenylhydrazone derivatives that we have prepared; the crystal structures of some of these compounds have been studied previously (Tameem et al., 2007;Salhin et al., 2007).
The bond lengths and angles in the title compound ( Fig.1) have normal values. The molecule is nealy planar, with a maximum deviation from the mean plane of 0.487 (1) Å for atom O1. The dihedral angle between the two benzene rings is 4.63 (1)°. The C-N bond lengths in the hydrazone moiety agree well with those reported earlier Shan, Yu et al., 2003). The asymmetry of the exocyclic angles at C7 [C7-C8-C13 = 118.2 (2)° and C7-C8-C9 = 123.3 (2)°] is more pronounced than that at C6 [N1-C6-C1 = 122.7 (1)° and N1-C6-C5 = 120.5 (1)°]. One of the hydrazone N atoms is involved in an O-H···N intramolecular hydrogen bond with the hydroxy group, while the other is involved in an N-H···O intramolecular hydrogen bond with the nitro group. Each of these hydrogen bonds generate an S(6) ring motif (Bernstein et al.,1995).
The molecules are linked into a chain along the [1 0 1] direction through N-H-O hydrogen bonds. The molecules pack as layers parallel to the ab plane. Within the layer, weak π-π interactions are observed between the C1-C6 and C8-C13 benzene rings, with a centroid-centroid distance of 3.7457 (8) Å.
Experimental 2,4-Dinitrophenylhydrazine (400 mg, 2 mmol) in concentrated sulfuric acid (5 ml) was slowly added to a solution of 2-hydroxy-5-nitrobenzaldehyde (337 mg, 2 mmol) in ethanol (95%, 20 ml). The mixture was stirred for 15 min, and was left to stand at room temperature for 30 min. The resulting product was filtered and washed with 95% ethanol (20 ml) and the orange powder product was collected. Crystals suitable for X-ray diffraction analysis were grown by slow evaporation of a saturated solution of the resulted compound in ethanol.
supplementary materials sup-2 Refinement O-and N-bound H atoms were located in a difference map and refined isotropically. The remaining H atoms were placed in calculated positions (C-H = 0.93 Å) and refined using a riding model, with U iso (H) = 1.2U eq (C). Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atomic numbering scheme. Hydrogen bonds are shown as dashed lines.   (17)