N′-[(E)-4-(Diethylamino)benzylidene]-4-nitrobenzohydrazide monohydrate

In the title compound, C18H20N4O3·H2O, the two aromatic rings are linked through a methylidenehydrazide fragment, which is fully extended with C—C—N—N, C—N—N=C and N—N=C—C torsion angles of 179.4 (2), 174.7 (2) and 178.3 (2)°, respectively. The dihedral angle between the two aromatic rings is 7.01 (8)°. In the crystal structure, the water of hydration is involved in extensive hydrogen bonding. Intermolecular O—H⋯O, N—H⋯O and O—H⋯N hydrogen bonds link the components of the structure into a two-dimensional network and additional stabilization is provided by weak intermolecular C—H⋯O hydrogen bonds.


Comment
The chemistry of hydrazones is being investigated continuously due to their excellent coordinating capability (Rodríguez-Argüelles et al., 2004) and biological activities (Zia-ur-Rehman et al., 2009;Galal et al., 2009;Bordoloi et al., 2009). In continuation of our studies on the synthesis of various heterocyclic compounds (Ahmad et al., 2010), the title compound, (I), has been synthesized and its crystal structure determined by X-ray crystallographic method which is presented in this article.
In the the title compound ( Fig. 1) the bond distances and angles agree with the corresponding bond distances and angles reported in closely related compounds (Fun et al., 2008;Bessy et al., 2006). The benzene rings in (I) are linked through a methylidenehydrazide fragment, C6/C7/N2/N3/C8, which is fully extended with torsion angles C6-C7-N2-N3, C7-N2-N3\ C8 and N2-N3═C8-C9 179.4 (2), 174.7 (2) and 178.3 (2)°, respectively. The dihedral angle between the two benzene rings is 7.01 (8)°. In the crystal structure, the water of hydration is extensively involved in hydrogen bonding. Thus, intermolecular O-H···O, N-H···O and O-H···N hydrogen bonds link the components of the structure into a two-dimensional network and additional stabilization is provided by weak intermolecular C-H···O hydrogen bonds; details have been provided in Table. 1. and Fig. 2.

Experimental
A mixture of para nitrobenzohydrazide (0.5 g, 2.76 mmoles), p-(diethylamino)benzaldehyde (0.49 g, 2.76 mmoles), orthophosphoric acid (0.2 ml) and methanol (50.0 ml) was refluxed for a period of 5.5 hours followed by removal of the solvent under vacuum. The contents were cooled and washed with cold methanol followed by crystallization from the same solvent at room temperature by slow evaporation. Yield: 91%. M.p. 491 K.

Refinement
Though all the H atoms could be distinguished in the difference Fourier map the H-atoms bonded to C-atoms were included at geometrically idealized positions and refined in riding-model approximation with C-H = 0.95, 0.98 and 0.99 Å, for aryl, methyl and methylene H-atoms, respectively; the coordinates of the H-atoms bonded to N2 and O4 were allowed to refine.
The U iso (H) were allowed at 1.5U eq (methyl-C and water-O) and 1.2U eq (the rest of the parent atoms). The final difference map was essentially featurless. Fig. 1. The title compound with the displacement ellipsoids plotted at 50% probability level (Farrugia, 1997). Symmetry code * = x, 1-y, z+1/2.

Special details
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 > 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.