N,N′-(Pyridine-2,6-diyl)dibenzamide

The molecule of the title compound, C19H15N3O2, is completed by the application of crystallographic twofold symmetry, with the pyridine N atom lying on the rotation axis. The molecular structure is approximately planar, the dihedral angle between the mean planes of the pyridine and benzene rings being 7.53 (11)°. In the crystal, N—H⋯O hydrogen bonds link the molecules into a two-dimensional array perpendicular to the c axis.

The molecule of the title compound, C 19 H 15 N 3 O 2 , is completed by the application of crystallographic twofold symmetry, with the pyridine N atom lying on the rotation axis. The molecular structure is approximately planar, the dihedral angle between the mean planes of the pyridine and benzene rings being 7.53 (11) . In the crystal, N-HÁ Á ÁO hydrogen bonds link the molecules into a two-dimensional array perpendicular to the c axis.

Comment
Carboxamides are compounds which are prepared by the reaction of amines and acylhalides. They are important N,Odonor ligands and have widespread applications in fields such as in coordination chemistry (Adolph et al. 2012& Amiri et al. 2009). As biologically active compounds, carboxamides find application in the treatment of diseases such as cancer, rheumatic disorders and inhibitors of calpain (calcium dependant cysteine proteases).
The molecular structure of the title compound is shown in Fig. 1. The molecule is approximately planar with the dihedral angle between the mean planes of the pyridine and benzene rings being 7.53 (11)°. Intermolecular N-H···O hydrogen bonds, with the carbonyl-O atoms acting as acceptors, link molecules into a two-dimensional array perpendicular to the c axis as illustrated in Fig. 2.

Experimental
All reagents were commercially available and used as received. To a magnetically stirred solution of 2,6-diaminopyridine (0.109 g, 1 mmol) and triethylamine (0.277 ml, 2 mmol) in dichloromethane (5 ml) was added drop-wise a mixture of benzoyl chloride (0.232 ml, 2 mmol) in dichloromethane (2 ml) at -10 °C over 15 min. The mixture was allowed to warm to room temperature and stirred for 48 h at room temperature. The solvent was removed under reduced pressure and the residue was purified by flash column chromatography (silica gel; petroleum ether-ethyl acetate) to give the title compound as a yellow powder. Crystals of the title compound were obtained from its methanol solution by slow solvent evaporation. Yield: 85%. Melting point: 407-408 K. Selected IR (KBr, cm -1 ): 3245 (N-H), 3061 (C-H), 1653 (C═O amide ), 1584 (C═N), 1461 (C═C).

Refinement
The hydrogen atom of the N-H group was positioned geometrically and refined as a riding atoms with N-H = 0.86 Å, and with U iso (H) = 1.2U eq (N). The C-H hydrogen atoms were positioned geometrically and refined as riding atoms with C-H = 0.93 Å, and with U iso (H) = 1.2U eq (C).

Computing details
Data collection: CrysAlis CCD (Oxford Diffraction, 2010); cell refinement: CrysAlis CCD (Oxford Diffraction, 2010); data reduction: CrysAlis RED (Oxford Diffraction, 2010); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: WinGX (Farrugia, 2012) and DIAMOND (Brandenburg & Putz, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).    where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.18 e Å −3 Δρ min = −0.16 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0091 (16) 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq O1