N′-(3-Bromo-5-chloro-2-hydroxybenzylidene)-4-hydroxybenzohydrazide

The molecule of the title compound, C14H10BrClN2O3, is planar [dihedral angle between the aromatic rings = 3.0 (2)°] and shows a trans configuration with respect to the C=N double bond. The crystal structure is stabilized by intermolecular N—H⋯O hydrogen bonds and an intramolecular O—H⋯N interaction also occurs.

The molecule of the title compound, C 14 H 10 BrClN 2 O 3 , is planar [dihedral angle between the aromatic rings = 3.0 (2) ] and shows a trans configuration with respect to the C N double bond. The crystal structure is stabilized by intermolecular N-HÁ Á ÁO hydrogen bonds and an intramolecular O-HÁ Á ÁN interaction also occurs.

Experimental
All the bond lengths are comparable to the values in the similar Schiff bases (Jing et al., 2005;Lu et al., 2008;Salhin et al., 2007). There is a intramolecular O-H···N hydrogen bond ( Fig. 1). In the crystal structure, molecules are linked through intermolecular N-H···O hydrogen bonds , to form a 3-D network (Table 1) (Fig. 2).
Experimental 3-Bromo-5-chlorosalicylaldehyde and 4-hydroxybenzohydrazide of AR grade were purchased from Aldrich and were used as was obtained. 3-Bromo-5-chlorosalicylaldehyde (235.3 mg, 1.0 mmol) and 4-hydroxybenzohydrazide (152.2 mg, 1.0 mmol) were dissolved in a methanol solution (80 ml). The mixture was stirred for two hours at room temperature. The resulting solution was left in air for a few days, yielding colourless block-like crystals.

Refinement
H2 was located in a difference Fourier map and refined isotropically, with N-H distance restrained to 0.90 (3)Å, and with U iso (H) fixed at 0.08Å 2 . Other H atoms were placed in idealized positions and constrained to ride on their parent atoms with C-H distances of 0.93Å, O-H distance of 0.82Å, and with U iso (H) set at 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.