(1E,2E)-1,2-Bis[1-(3-chlorophenyl)ethylidene]hydrazine

The title molecule, C16H14Cl2N2, lies on an inversion center. The dihedral angle between the symmetry-related benzene rings is 0.02 (11)°. The mean plane of the central C(methyl)—C=N—N=C—C(methyl) unit forms a dihedral angle of 5.57 (12)° with the symmetry-unique benzene ring.

The title molecule, C 16 H 14 Cl 2 N 2 , lies on an inversion center. The dihedral angle between the symmetry-related benzene rings is 0.02 (11) . The mean plane of the central C(methyl)-C N-N C-C(methyl) unit forms a dihedral angle of 5.57 (12) with the symmetry-unique benzene ring.

Comment
Due to the interesting applications of hydrazones with respect to their antibacterial, antiviral and antioxidant (Li et al., 2009) as well as fluorescent properties (Qin et al., 2009), we have synthesized a series of hydrazones in order to study these activities and have reported some of these crystal structures Fun et al., 2010Fun et al., ,2011Jansrisewangwong et al., 2010;Nilwanna et al., 2011). As part of our on-going research on the medicinal chemistry of hydrazones, the title compound (I) was synthesized and its biological activities will be reported elsewhere. However, it does not possess fluorescent property.
The molecular structure of (I) is shown in Fig (Allen et al., 1987) and are comparable with the related structures Fun et al., 2010;Jansrisewangwong et al., 2010;Nilwanna et al., 2011).
Although no clasical hydrogen bonds or weak interactions were observed in the crystal structure, the crystal packing is shown in Fig. 2.

Experimental
The title compound (I) was synthesized by mixing a solution (1:2 molar ratio) of hydrazine hydrate (0.10 ml, 2 mmol) and 3-chloroacetophenone (0.50 ml, 4 mmol) in ethanol (20 ml). The resulting solution was refluxed for 7 h, yielding the yellow crystalline solid. The resultant solid was filtered off and washed with methanol. Yellow block-shaped single crystals of the title compound suitable for x-ray structure determination were recrystalized from acetone by slow evaporation of the solvent at room temperature over several days, Mp. 356-358 K.

Refinement
All H atoms were positioned geometrically and allowed to ride on their parent atoms, with d(C-H) = 0.93 Å for aromatic and 0.96 Å for CH 3 atoms. The U iso values were constrained to be 1.5U eq of the carrier atom for methyl H atoms and 1.2U eq for the remaining H atoms. A rotating group model was used for the methyl groups. The highest residual electron density peak is located at 1.92 Å from H8B and the deepest hole is located at 0.70 Å from Cl1. Fig. 1. The molecular structure of (I), showing 50% probability displacement ellipsoids. Atoms with suffix A were generated by symmetry code -x, 1-y, 2-z.

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.