N,N′-(Ethane-1,2-diyldi-o-phenylene)bis(pyridine-2-carboxamide)

The title molecule, C26H22N4O2, is centrosymmetric and adopts an anti conformation. Two intramolecular hydrogen bonds, viz. amide–pyridine N—H⋯N and phenyl–amide C—H⋯O, stabilize the trans conformation of the (pyridine-2-carboxamido)phenyl group about the amide plane. In the crystal, the presence of weak intermolecular C—H⋯O hydrogen bonds results in the formation of a three-dimensional network.

The molecule contains two N-phenylene(pyridine-2-carboxiamide) moieties linked by an ethylene bridge. The crystal of (I) adopts an anti conformation (Fig. 1). Only a half of the molecule constitutes the asymmetric unit and the other half is centrosymmetrically related. The bond distances observed in (I) do not deviate significantly from the mean values of those in N,N'-(methylenedi-p-phenylene)bis(pyridine-2-carboxamide) (Meghdadi et al., 2006). The angle between the phenylenyl and pyridyl rings is about 10°. Two intramolecular hydrogen bonds of N amide -H···N py and C ph -H···O amide stabilise trans conformation of the N-phenylene(pyridine-2-carboxiamide) moiety about the amide plane (Table 1 and Fig. 1). Two relatively weak intermolecular hydrogen bonds of C12-H12···O amide and C9-H9b···O amide present to form overall three-dimensional netowork in the crystal (Table 1 and Fig. 2).

Experimental
A solution of 2,2'-ethylenedianiline (1.09 g, 5 mmol) in pyridine (5 mL) was added to a solution of pyridine-2-carboxylic acid (1.25 g, 10 mmol) in pyridine (10 mL). After the resulting solution was stirred at 313 K for 10 min, triphenyl phosphate (3.21 g,10 mmol) was added dropwise and the reaction mixture was stirred at 373 K for 4 h. The reaction mixture was cooled to room temperature and stirred for 10 h. The volume of the solution was reduced to 10 mL and kept over night in a hood.
The remaining solution was filtered, thoroughly washed four times with 100 mL solvent of water and acetone (1:1), and dried in vacuum. X-ray quality crystals were obtained by slow diffusion of diethyl ether into a dichloromethane solution at room temperature (yield 90%; m.p. about 473 K).
Refinement H-atom of N-H was refined isotropically. All H-atoms at C atoms were placed in geometrically ideallized positions and constrained to ride their parent atoms with the bond lengths of 0.95 Å and 0.99 Å for aryl and methylene H atoms, repectively, and with the isotropic displacement paprameteres of U iso (H) = 1.2U eq (C).
supplementary materials sup-2 Figures Fig. 1. ORTEP drawing of the title compound showing 30% probability displacement ellipsoids and the atomic numbering scheme. Dotted lines represent the intramolecular hydrogen bonds. Atomic-numberings for H atoms are omitted for clarity. Symmetry code to generate the molecule: (i) -x + 1, -y + 2, -z + 1.