(E)-4-Chloro-2-[(2-hydroxyphenyl)iminomethyl]phenol

The title compound, C13H10ClNO2, exists in a trans configuration about the central C=N bond. The two benzene rings are almost coplanar, making a dihedral angle of 2.48 (10)°. An intramolecular O—H⋯N hydrogen bond generates an S(6) ring motif. In the crystal structure, O—H⋯O hydrogen bonds link the molecules into chains along [101]. Short C⋯Cl contacts [3.584 (2)–3.646 (2) Å] are observed. A short intramolecular C—H⋯O contact occurs.


Comment
We have been interested in synthesis of Schiff base ligands and their complexes (Eltayeb et al., 2007a,b) due to their applications such as analytical reagents for the determination of trace elements (Eltayeb & Ahmed, 2005a,b), pharmacological activities, anticancer (Dao et al., 2000), anti-HIV (Sriram et al., 2006), antibacterial and antifungal (Karthikeyan et al., 2006) activities. The title compound was used to synthesis the chelated borate catalyst (Wei & Atwood, 1998). Herein we report the crystal structure of the title Schiff base ligand (I).

Experimental
The title compound was synthesized by adding 5-chloro-2-hydroxybenzaldehyde (0.312 g, 2 mmol) to the solution of 2aminophenol (0.218 g, 2 mmol) in ethanol (30 ml). The mixture was refluxed with stirring for half an hour. The resultant yellow-orange solution was filtered and the filtrate was evaporated to give a yellow solid product. Yellow needle-shaped single crystals of the title compound suitable for x-ray structure determination were obtained from ethanol by slow evaporation at room temperature after a few days.

Refinement
All H atoms were positioned geometrically and allowed to ride on their parent atoms, with d(O-H) = 0.82 Å and d(C-H) = 0.93 Å. The U iso (H) values were constrained to be 1.2U eq of the carrier atoms. The highest residual electron density peak is located at 0.70 Å from C5 and the deepest hole is located at 0.05 Å from H1O2. Fig. 1. The molecular structure of the title compound, with 50% probability displacement ellipsoids and the atom-numbering scheme. The hydrogen bond is shown as a dashed line.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
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.