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

The title compound, C13H9Cl2NO, was crystallized from a methanol solution of 5-chlorosalicylaldehyde and o-chloroaniline. The molecule displays a trans configuration with respect to the imine C=N double bond. The N atom is involved in an intramolecular O—H⋯N hydrogen bond. The two aromatic rings are essentially coplanar, the dihedral angle between them being 7.1 (1)°. A C—H⋯π interaction is present in the crystal.

The title compound, C 13 H 9 Cl 2 NO, was crystallized from a methanol solution of 5-chlorosalicylaldehyde and o-chloroaniline. The molecule displays a trans configuration with respect to the imine C N double bond. The N atom is involved in an intramolecular O-HÁ Á ÁN hydrogen bond. The two aromatic rings are essentially coplanar, the dihedral angle between them being 7.1 (1) . A C-HÁ Á Á interaction is present in the crystal.
This work was supported financially by research project No. 08JZ09 of the Phytochemistry Key Laboratory of Shaanxi Province.

Comment
The Schiff base containing some O and N atoms is a new important biological ligand and it shows some interesting biological properties, such as antibacterial, antiphlogistic, anticancer and high catalytic activities (Antony et al., 1999;Lumme & Elo et al., 1984;Yao et al., 1999), so the chemical behavior of the Schiff base has drawn our attention (Ueno et al., 2006). Our research emphasis is focused on the synthesis of the Schiff base. Then, a new crystal structure of the title compound, (I), is reported here.
The molecular structure of (I) are illustrated in Fig. 1. In the structure of (I), the whole molecule is essentially planar with a 7.1 (2)° dihedral angle between the two phenyl rings. The C1═N1 bond distance [1.277 (3)Å] is shorter than the standart 1.28Å value of C═N double bond, indicating a delocalization of π-electron density across the phenyl ring. In addition to the intramolecular O-H..N hydrogen bond, there is also an intermolecular C-H..π interaction (Table 1.)

Experimental
A solution of 5-chlorosalicylaldehyde (0.1 mmol, 15.7 mg) in methanol (10 ml) was added dropwise to the methanol (10 ml) solution of o-chloroaniline (0.1 mmol, 12.8 mg) with stirring. The mixture was stirred at room temperature for one hour and then filtered. After allowing the filtrate to stand in air for 3 d, yellow block-shaped crystals of the title compound were formed in slow evaporation of the solvent. The crystals were collected, washed with methanol and dried in a vacuum desiccator using anhydrous CaCl 2 (yield 60%).

Refinement
All H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C-H distances 0.93Å and U iso (H) = 1.2 U eq (C) and O-H distances 0.82Å and U iso (H) = 1.5 U eq (O). Fig. 1. The structure of the title compound with 30% probability ellipsoids. The dashed line represents hydrogen bond.