A 2:1 co-crystal of p-nitro­benzoic acid and N,N′-bis­­(pyridin-3-ylmeth­yl)ethanedi­amide: crystal structure and Hirshfeld surface analysis

The title 2:1 co-crystal, 2C7H5NO4C14H14N4O2, in which the complete diamide molecule is generated by crystallographic inversion symmetry, features a threemolecule aggregate sustained by hydroxyl-O—HN(pyridyl) hydrogen bonds. The p-nitrobenzoic acid molecule is non-planar, exhibiting twists of both the carboxylic acid and nitro groups, which form dihedral angles of 10.16 (9) and 4.24 (4), respectively, with the benzene ring. The diamide molecule has a conformation approximating to a Z shape, with the pyridyl rings lying to either side of the central, almost planar diamide residue (r.m.s. deviation of the eight atoms being 0.025 A˚ ), and forming dihedral angles of 77.22 (6) with it. In the crystal, three-molecule aggregates are linked into a linear supramolecular ladder sustained by amide-N—HO(nitro) hydrogen bonds and orientated along [104]. The ladders are connected into a double layer via pyridyl- and benzeneC—HO(amide) interactions, which, in turn, are connected into a threedimensional architecture via – stacking interactions between pyridyl and benzene rings [inter-centroid distance = 3.6947 (8) A˚ ]. An evaluation of the Hirshfeld surfaces confirm the importance of intermolecular interactions involving oxygen atoms as well as the – interactions.