Crystal structure, Hirshfeld surface analysis and computational study of the 1:2 co-crystal formed between N,N′-bis(pyridin-4-ylmethyl)ethane-diamide and 4-chlorobenzoic acid

The asymmetric unit of the title 1:2 co-crystal, C14H14N4O2 center dot 2C(7)H(5)ClO(2), comprises two half molecules of oxalamide ((LH2)-L-4), as each is disposed about a centre of inversion, and two molecules of 4-chlorobenzoic acid (CBA), each in general positions. Each (LH2)-L-4 molecule has a (+)antiperiplanar conformation with the pyridin-4-yl residues lying to either side of the central, planar C2N2O2 chromophore with the dihedral angles between the respective central core and the pyridyl rings being 68.65 (3) and 86.25 (3)degrees, respectively, representing the major difference between the independent (LH2)-L-4 molecules. The anti conformation of the carbonyl groups enables the formation of intramolecular amide-NH center dot center dot center dot O(amide) hydrogen bonds, each completing an S(5) loop. The two independent CBA molecules are similar and exhibit C-6/CO2 dihedral angles of 8.06 (10) and 17.24 (8)degrees, indicating twisted conformations. In the crystal, two independent, three-molecule aggregates are formed via carboxylic acid-OH center dot center dot center dot N(pyridyl) hydrogen bonding. These are connected into a supramolecular tape propagating parallel to [100] through amide-N-H center dot center dot center dot O(amide) hydrogen bonding between the independent aggregates and ten-membered {center dot center dot center dot HNC2O}(2) synthons. The tapes assemble into a three-dimensional architecture through pyridyl- and methylene-C-H center dot center dot center dot O(carbonyl) and CBA-C-H center dot center dot center dot O(amide) interactions. As revealed by a more detailed analysis of the molecular packing by calculating the Hirshfeld surfaces and computational chemistry, are the presence of attractive and dispersive Cl center dot center dot center dot C-O interactions which provide interaction energies approximately one-quarter of those provided by the amide-N-H center dot center dot center dot O(amide) hydrogen bonding sustaining the supramolecular tape.