(E,E)-N′-{4-[(2-Benzoylhydrazin-1-ylidene)methyl]benzylidene}benzohydrazide

In the title compound, C22H18N4O2, the molecules lie across an inversion centre. The dihedral angle between the mean planes of the central and terminal benzene rings is 66.03 (2)°. The molecule displays trans and anti conformations about the C=N and N—N bonds, respectively. In the crystal, N—H⋯O hydrogen bonds, with the O atoms of C=O groups acting as acceptors, link the molecules into a chain along [101].

In the title compound, C 22 H 18 N 4 O 2 , the molecules lie across an inversion centre. The dihedral angle between the mean planes of the central and terminal benzene rings is 66.03 (2) . The molecule displays trans and anti conformations about the C N and N-N bonds, respectively. In the crystal, N-HÁ Á ÁO hydrogen bonds, with the O atoms of C O groups acting as acceptors, link the molecules into a chain along [101].
The molecules of C 22 H 18 N 4 O 2 , lie across inversion centres and the asymmetric unit contains a half molecule (Fig. 1). The terminal benzene rings are parallel to each other and the distance of two planes which embrace these rings is 3.168 Å apart. The dihedral angle between the mean planes of the central and two terminal benzene rings is 66.03 (2)°. The molecule displays a trans configuration with respect to the C=N and N-N bonds. The packing diagram of the title compound is shown in Fig. 2. There are two strong intermolecular N-H···O hydrogen bonds in which the O atoms of the carbonyl groups (-C=O) act as hydrogen acceptors for the hydrogen of N-H and a one-dimensional chain is formed by these hydrogen bonds (Fig. 3).

Experimental
For preparing the title compound a methanol (10 ml) solution of benzhydrazide (3 mmol) was added drop-wise to a methanol solution (10 ml) of terephthalaldehyde (1.5 mmol), and the mixture was refluxed for 4 h. The solution was then evaporated on a steam bath to 5 cm 3 and cooled to room temperature. The white precipitates of the title compound were separated and filtered off, washed with 3 ml of cooled methanol and then dried in air. Colorless crystals were obtained SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999) and PLATON (Spek, 2009).

Figure 1
The molecular structure of the title compound. Displacement ellipsoids are drawn at the 30% probability level.

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.