2-Bromo-4-chloro-6-[(E)-p-tolyliminomethyl]phenol

The molecule of the title compound, C14H11BrClNO, displays an E configuration with respect to the imine C=N double bond. The two aromatic rings are essentially coplanar, forming a dihedral angle of 7.9 (2)°. An intramolecular O—H⋯N hydrogen bond stabilizes the crystal structure.


S1. Comment
Recently, there has been a growing interest in Schiff base ligands because of their applications, such as catalysts and nonlinear optical materials. In recent years, they were found to play an important role in the catalysis and electron transfer of the living organisms (Ueno et al., 2006). This stimulated our interest in this field. As an extension of the work on the structural characterization of Schiff base compounds, the crystal structure of the title compound is reported here.
The molecular structure and crystal packing of the title compound are illustrated in Figure 1 and 2, respectively. Bond lengths and angles are not unusual, with the C1═N1 bond distance (1.263 (5) Å) slightly shorter than a normal C═N. The molecule is essentially planar, the maximum deviation from the planarity being 0.167 (6) Å for atom C10. The dihedral angle between the two aromatic rings is 7.9 (2) °. An intramolecular O-H···N hydrogen bond (Table 1) stabilizes the crystal structure.

S2. Experimental
3-Bromo-5-chlorosalicylaldehyde (0.1 mmol, 23.6 mg) and p-toluidine (0.1 mmol, 10.7 mg) were dissolved in methanol (10 ml). The mixture was stirred at room temperature for 10 min and then filtered. After allowing the filtrate to stand in air for 3 d, yellow block-shaped crystals of the title compound suitable for X-ray analysis were formed by slow evaporation of the solvent. The crystals were collected, washed with methanol and dried in a vacuum desiccator using anhydrous CaCl 2 (yield 54%).

S3. Refinement
All H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C-H = 0.93-0.96 Å, O-H = 0.82 Å, and with U iso (H) = 1.2 U eq (C) or 1.5 U eq (C, O) for methyl and hydroxy H atoms.  The molecular structure of the title compound with 30% probability ellipsoids. H atoms are shown as spheres of arbitrary radii. The dashed line represents a hydrogen bond.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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.