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

Abstract

The asymmetric unit of the title 1:2 co-crystal, C14H14N4O2·2C7H5ClO2, comprises two half molecules of oxalamide (4LH2), as each is disposed about a centre of inversion, and two molecules of 4-chlorobenzoic acid (CBA), each in general positions. Each 4LH2 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)°, respectively, representing the major difference between the independent 4LH2 molecules. The anti conformation of the carbonyl groups enables the formation of intramolecular amide-N—H...O(amide) hydrogen bonds, each completing an S(5) loop. The two independent CBA molecules are similar and exhibit C6/CO2 dihedral angles of 8.06 (10) and 17.24 (8)°, indicating twisted conformations. In the crystal, two independent, three-molecule aggregates are formed via carboxylic acid-O—H...N(pyridyl) hydrogen bonding. These are connected into a supramolecular tape propagating parallel to [100] through amide-N—H...O(amide) hydrogen bonding between the independent aggregates and ten-membered {...HNC2O}2 synthons. The tapes assemble into a three-dimensional architecture through pyridyl- and methylene-C—H...O(carbonyl) and CBA-C—H...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...C=O interactions which provide interaction energies approximately one-quarter of those provided by the amide-N—H...O(amide) hydrogen bonding sustaining the supramolecular tape.

Keywords

• crystal structure
• oxalamide
• hydrogen bonding
• hirshfeld surface analysis
• computational chemistry