N-[(E)-4-Chlorobenzylidene]-2,4-dimethylaniline

The title molecule, C15H14ClN, exists in a trans configuration with respect to the C=N bond [1.2813 (16) Å]. The dihedral angle between the benzene rings is 52.91 (6)°. The crystal structure is stabilized by weak intermolecular C—H⋯π interactions.


Experimental
Cg1 and Cg2 are the centroids of the C1-C6 and C8-C13 benzene rings, respectively.

Comment
The chemistry of the carbon-nitrogen double bond plays a vital role in the progress of science. Schiff-base compounds have been used as fine chemicals and medical substrates. Recently, multi-dentate complexes of iron and nickel showed high activities of ethylene oligomerization and polymerization (Ittel et al., 2000). Schiff bases have a wide variety of applications in many fields, e.g., biological, inorganic and analytical chemistry (Cimerman et al., 2000). They are known to exhibit potent antibacterial, anticonvulsant, anti-inflammatory activities (Shah et al., 1992). In addition, some Schiff bases show pharmacologically useful activities like anticancer (Pandeya et al., 1999), anti-hypertensive and hypnotic (More et al., 2001) properties. Unfortunately, most Schiff bases are chemically unstable and show a tendency to be involved in various equilibria, like tautomeric interconversions, hydrolysis or formation of ionized species (Cimerman & Stefanac, 2001;Galic et al., 1997). Therefore, successful application of Schiff bases requires a careful study of their characteristics.
The molecular structure of the title compound is shown in Fig. 1. The bond lengths (Allen et al., 1987) and angles are within normal ranges. The title compound exists in trans configuration with respect to the C7═N1 bond [C7═N1 = 1.2813 (16) Å]. The benzene rings (C1-C6 and C8-C13) form a dihedral angle of 52.91 (6)°.

Experimental
Equimolar amounts of of 4-chloro benzaldehyde and 2,4 dimethyl aniline were dissolved in a minimum amount of ethanol, followed by addition of 2 ml glacial acetic acid. The solution was refluxed for 8 h then cooled to room temperature and poured into ice cold water. The solid product was collected through filtration and then dried at 353 K. The product was dissolved in ethanol, recrystallized and then dried to give colourless crystals. Yield: 75%, m.p. 432-435 K.

Refinement
All H atoms were positioned geometrically and refined using a riding model with C-H = 0.95 or 0.98 Å and U iso (H) = 1.2 or 1.5 U eq (C). A rotating-group model was applied for the methyl group. The highest residual electron density peak is located at 0.69 Å from C12 and the deepest hole is located at 0.15 Å from H15B. Fig. 1

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq