N′-(2-Chlorobenzylidene)-4-hydroxybenzohydrazide

In the molecule of the title compound, C14H11ClN2O2, the dihedral angle between the benzene rings is 30.53 (4)°. In the crystal structure, intermolecular O—H⋯O and N—H⋯O hydrogen bonds link the molecules into a two-dimensional network. π–π contacts between benzene rings [centroid–centroid distance = 3.619 (1) Å] may further stabilize the structure. The crystal studied was found to be an inversion twin.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: HK2750).

Comment
Schiff base compounds are a class of important materials used in pharmaceutical and medicinal fields (Dao et al., 2000;Sriram et al., 2006;Karthikeyan et al., 2006). Schiff bases have also been used as versatile ligands in coordination chemistry (Ali et al., 2008;Kargar et al., 2009;Yeap et al., 2009). Recently, the crystal structures of a large number of Schiff base compounds have been reported Nadeem et al., 2009;Eltayeb et al., 2008). As a part of our ongoing investigation (Hao, 2009), we report herein the crystal structure of the title new Schiff base compound.
In the molecule of the title compound ( Fig. 1), the bond lengths (Allen et al., 1987) and angles are within normal ranges.

Experimental
For the preparation of the title compound, 2-chlorobenzaldehyde (0.1 mmol, 14.1 mg) and 4-hydroxybenzohydrazide (0.1 mmol, 15.2 mg) were refluxed in a methanol solution (30 ml) for 30 min to give a clear orange solution. Yellow block-shaped single crystals of the compound were formed by slow evaporation of the solvent over several days at room temperature.

Refinement
Atom H2A (for NH) was located in a difference Fourier map and refined as riding in as-found relative position, U iso (H) = 1.82U eq (N). The remaining H atoms were positioned geometrically with O-H = 0.82 Å (for OH) and C-H = 0.93 for aromatic H atoms, respectively, and constrained to ride on their parent atoms, with U iso (H) = xU eq (C,O), where x = 1.5 for OH H and x = 1.2 for aromatic H atoms. Fig. 1

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.