Crystal structure, Hirshfeld surface analysis and computational study of the 1:2 co-crystal formed between N,N′-bis­­[(pyridin-4-yl)meth­yl]ethanedi­amide and 3-chloro­benzoic acid

The asymmetric unit of the title 1:2 co-crystal, C14H14N4O2·2C7H5ClO2, comprises a half-mol­ecule of oxalamide (4LH2), being located about a centre of inversion, and a mol­ecule of3-chloro­benzoic acid (3-ClBA) in a general position. From symmetry, the 4LH2 mol­ecule has a (+)anti­periplanar conformation with the 4-pyridyl residues lying to either side of the central, planar C2N2O2 chromophore with the dihedral angle between the core and pyridyl ring being 74.69 (11)°; intra­molecular amide-N—H⋯O(amide) hydrogen bonds are noted. The 3-ClBA mol­ecule exhibits a small twist as seen in the C6/CO2 dihedral angle of 8.731 (12)°. In the mol­ecular packing, three-mol­ecule aggregates are formed via carb­oxy­lic acid-O—H⋯N(pyrid­yl) hydrogen bonding. These are connected into a supra­molecular tape along [111] through amide-N—H⋯O(carbon­yl) hydrogen bonding. Additional points of contact between mol­ecules include pyridyl and benzoic acid-C—H⋯O(amide), methyl­ene-C—H⋯O(carbon­yl) and C—Cl⋯π(pyrid­yl) inter­actions so a three-dimensional architecture results. The contributions to the calculated Hirshfeld surface are dominated by H⋯H (28.5%), H⋯O/O⋯H (23.2%), H⋯C/C⋯H (23.3%), H⋯Cl/Cl⋯H (10.0%) and C⋯Cl/C⋯Cl (6.2%) contacts. Computational chemistry confirms the C—Cl⋯π inter­action is weak, and the importance of both electrostatic and dispersion terms in sustaining the mol­ecular packing despite the strong electrostatic term provided by the carb­oxy­lic acid-O—H⋯N(pyrid­yl) hydrogen bonds.