N,N′-Bis[1-(pyridin-2-yl)ethylidene]benzene-1,4-diamine

In the title compound, C20H18N4, the benzene ring lies about an inversion center. The central benzene-1,4-diamine unit is connected to two pyridine rings by the C=N imine bonds. The dihedral angle between the benzene and pyridine rings is 82.9 (1)°.

In the title compound, C 20 H 18 N 4 , the benzene ring lies about an inversion center. The central benzene-1,4-diamine unit is connected to two pyridine rings by the C N imine bonds. The dihedral angle between the benzene and pyridine rings is 82.9 (1) .

Related literature
For background information on Schiff bases derived from pyridinecarbaldehydes, see: Marjani et al. (2009). For pyridinederived Schiff bases as bidentate chelating ligands towards metal centers, see: Wu et al. (2006). For a related structure, see: Marjani et al. (2011). For the synthesis of the title compound, see: Yoshida et al. (2000).
The title compound ( Fig. 1) lies on an inversion center. The dihedral angle between 1,4-diamine-substituted benzene ring and the pyridine ring is 82.9 (1)°. The bond lengths and bond angles in the title molecule agree very well with the corresponding bond distances and bond angles reported in a closely related compound (Marjani et al., 2011).

Experimental
The title compound was synthesized by usual Schiff-base condensation of benzene-1,4-diamine and 2-acetyl pyridine. 2-Acetylpyridine (4.50 ml, 0.04 mol) was added in an ethanol (100 mL) solution of benzene-1,4-diamine (2.16 g, 0.02 mol) at room temperature. After the addition was completed, the reaction mixture was heated to 343-353 K and refluxed for 6 h (Yoshida et al., 2000). Then the resultant precipitate was filtered off, washed with ethanol, dried in air and 5.06 g (Yield: 80.6%) brown product was obtained. The crystals of the title compound suitable for X-ray analysis ewere obtained by recrystallization from a mixture of hexane and dichloromethane (3:1).

Refinement
The C-bound H atoms were positioned geometrically with C-H = 0.93 and 0.96 Å, for aryl and methyl H-atoms, respectively, and allowed to ride on their parent atoms with U iso (H) = 1.5 U eq (C-methyl) or 1.2 U eq (C-aryl).

Figure 2
A view of the unit cell packing of the title compound along the a-axis. 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq N1 0.1873 (