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

In the title compound, C16H14Br2N2, the complete molecule is generated by a crystallographic twofold axis. The dihedral angle between the two benzene rings is 35.28 (8)° and that between the best planes of two ethylidinehydrazine N—N=C—Me units is 87.67 (11)°. Each of these N/N/C/C planes makes a dihedral angle of 63.81 (10)° with the adjacent benzene ring. In the crystal, the molecules are arranged into a layer parallel to the ac plane through C—H⋯π interactions. C⋯Br short contacts [3.4032 (18)–3.5969 (19) Å] are also observed.

In the title compound, C 16 H 14 Br 2 N 2 , the complete molecule is generated by a crystallographic twofold axis. The dihedral angle between the two benzene rings is 35.28 (8) and that between the best planes of two ethylidinehydrazine N-N C-Me units is 87.67 (11) . Each of these N/N/C/C planes makes a dihedral angle of 63.81 (10) with the adjacent benzene ring. In the crystal, the molecules are arranged into a layer parallel to the ac plane through C-HÁ Á Á interactions. CÁ Á ÁBr short contacts [3.4032 (18)-3.5969 (19) Å ] are also observed.

Comment
Hydrazones are a special group of compounds in the Schiff base family and characterized by the presence of >C═N-N═C< (Avaji et al., 2009). They have been studied for their chemical and biological activities for a long time. They and their complexes show various biological activities such as insecticidal, antitumor, antioxidant, antifungal, antibacterial and antiviral properties (El-Tabl et al., 2008;Rollas & Küçükgüzel, 2007). These interesting properties prompt us to synthesise the title hydrazone derivative (I) in order to study its antibacterial activity. Herein the crystal structure of (I) was reported.
The asymmetric unit of (I) (Fig. 1), C 16 H 14 Br 2 N 2 , contains one half-molecule and the complete molecule is generated by a crystallographic symmetry centre 1 -x, y, 1/2 -z. The molecule of (I) exists in an E configuration with respect to the The bond distances are of normal values (Allen et al., 1987) and are comparable with a related structure (Zhao et al., 2006).
In the crystal structure (Fig. 2), the molecules are arranged into zigzag chains along the a axis and these chains stacked along the c direction. The molecules are consolidated by C···Br [3.4032 (18)-3.5969 (19) Å] short contacts. C-H···π interactions were also observed (Table 1); Cg 1 is the centroid of C1-C6 ring.

Experimental
The title compound was synthesized by mixing a solution (1:2 molar ratio) of hydrazine hydrate (0.10 ml, 2 mmol) and 2-bromoacetophenone (0.54 ml, 4 mmol) in ethanol (20 ml). The resulting solution was refluxed for 5 h, yielding the white crystalline solid. The resultant solid was filtered off and washed with methanol. Colorless hexagonal-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 (m.p. 387-389 K).

Refinement
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. Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atom-numbering scheme. Atoms with suffix A were generated by symmetry code 1 -x, y, 1/2 -z.

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 120.0 (1) K. 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 Rfactors(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.