(E)-4-Chloro-N′-(5-hydroxy-2-nitrobenzylidene)benzohydrazide

The title compound, C14H10ClN3O4, was synthesized by the reaction of 5-hydroxy-2-nitrobenzaldehyde with an equimolar quantity of 4-chlorobenzohydrazide in methanol. The molecule displays an E configuration about the C=N bond. The dihedral angle between the two benzene rings is 3.9 (2)°. In the crystal structure, molecules are linked through intermolecular N—H⋯O and O—H⋯O hydrogen bonds, forming chains running along the b axis.

In the last few years, the crystal structures of a large number of hydrazone compounds have been reported (Mohd Lair et al., 2009;Fun et al., 2008;Li & Ban, 2009;Zhu et al., 2009;Yang, 2007;You et al., 2008). As a continuation of our work in this area (Qu et al., 2008;Yang et al., 2008;Cao & Lu, 2009a,b), the title new hydrazone compound, derived from the reaction of 5-hydroxy-2-nitrobenzaldehyde with an equimolar quantity of 4-chlorobenzohydrazide, is reported.
In the title compound, Fig. 1, the dihedral angle between the two benzene rings is 3.9 (2)°. The molecule displays an E configuration about the C═N bond. In the crystal structure, molecules are linked through intermolecular N-H···O and O-H···O hydrogen bonds, Table 1, to form chains running along the b axis, Fig. 2.

Experimental
The compound was prepared by refluxing equimolar quantities of 5-hydroxy-2-nitrobenzaldehyde with 4-chlorobenzohydrazide in methanol. Colorless block-like crystals were formed by slow evaporation of the solution in air.

Refinement
H2 was located in a difference Fourier map and refined isotropically, with the N-H distance restrained to 0.90 (1) Å. The other H atoms were placed in idealized positions and constrained to ride on their parent atoms, with C-H distances of 0.93 Å, O-H distance of 0.82 Å, and with U iso (H) set at 1.2U eq (C) and 1.5U eq (O). Fig. 1. The molecular structure of the title compound with ellipsoids drawn at the 30% probability level.

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.