Crystal structure, Hirshfeld surface analysis and computational study of the 1:2 co-crystal formed between N,N'-bis-[(pyridin-4-yl)meth-yl]ethanedi-amide and 3-chloro-benzoic acid.

The asymmetric unit of the title 1:2 co-crystal, C(14)H(14)N(4)O(2)·2C(7)H(5)ClO(2), comprises a half-mol-ecule of oxalamide ((4) LH(2)), being located about a centre of inversion, and a mol-ecule of3-chloro-benzoic acid (3-ClBA) in a general position. From symmetry, the (4) LH(2) mol-ecule has a (+)anti-periplanar conformation with the 4-pyridyl residues lying to either side of the central, planar C(2)N(2)O(2) chromophore with the dihedral angle between the core and pyridyl ring being 74.69†(11)°; intra-molecular amide-N-H⋯O(amide) hydrogen bonds are noted. The 3-ClBA mol-ecule exhibits a small twist as seen in the C(6)/CO(2) dihedral angle of 8.731†(12)°. In the mol-ecular packing, three-mol-ecule aggregates are formed via carb-oxy-lic acid-O-H⋯N(pyrid-yl) hydrogen bonding. These are connected into a supra-molecular tape along [111] through amide-N-H⋯O(carbon-yl) hydrogen bonding. Additional points of contact between mol-ecules include pyridyl and benzoic acid-C-H⋯O(amide), methyl-ene-C-H⋯O(carbon-yl) and C-Cl⋯π(pyrid-yl) inter-actions 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 inter-action is weak, and the importance of both electrostatic and dispersion terms in sustaining the mol-ecular packing despite the strong electrostatic term provided by the carb-oxy-lic acid-O-H⋯N(pyrid-yl) hydrogen bonds.