(E)-4-Hydroxy-N′-(4-nitrobenzylidene)benzohydrazide

The molecule of the title compound, C14H11N3O4, is approximately planar, the dihedral angle between the planes of the two substituted benzene rings being 2.54 (7)°. The molecule exists in a trans configuration with respect to the central methylidene unit. In the crystal structure, molecules are linked through intermolecular O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds, forming layers parallel to (101). The O/N—H⋯O and C—H⋯O interactions form a pair of bifurcated acceptor bonds involving the cabonyl/nitro O atom, generating an R 2 1(6) motif.

The molecule of the title compound, C 14 H 11 N 3 O 4 , is approximately planar, the dihedral angle between the planes of the two substituted benzene rings being 2.54 (7) . The molecule exists in a trans configuration with respect to the central methylidene unit. In the crystal structure, molecules are linked through intermolecular O-HÁ Á ÁO, N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds, forming layers parallel to (101). The O/N-HÁ Á ÁO and C-HÁ Á ÁO interactions form a pair of bifurcated acceptor bonds involving the cabonyl/nitro O atom, generating an R 2 1 (6) motif.

Structure Reports Online
The title Schiff base molecule ( Fig. 1) is nearly planar, with the dihedral angle between the two benzene rings being 2.54 (7)°. The molecule exists in a trans configuration with respect to the central methylidene (C7═N1) unit. The N2-N1-C7-C1 torsion angle is 179.12 (14)°.
In the crystal structure, the molecules are linked through intermolecular O-H···O and N-H···O hydrogen bonds (Table   1), forming layers parallel to the (101) (Fig. 2). Within the layer, C-H···O hydrogen bonds are also observed.

Experimental
The title compound was prepared by refluxing 4-nitrobenzaldehyde (1.0 mol) with 4-hydroxybenzohydrazide (1.0 mol) in methanol (100 ml). Excess methanol was removed from the mixture by distillation. A colourless solid product was filtered, and washed three times with methanol. Colourless block-shaped crystals of the title compound were obtained from a methanol solution by slow evaporation in air.

Refinement
Atom H2B was located in a difference Fourier map and refined isotropically, with the N-H distance restrained to 0.90 (1)Å and U iso fixed at 0.08 Å 2 . The remaining H atoms were placed in calculated positions (C-H = 0.93 Å and O-H = 0.82 Å) and refined as riding with U iso (H) = 1.2U eq (C) and 1.5U eq (O).

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 > 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.