Crystal and Molecular Structures of the 2:1 Cocrystal of 4-Nitrophenylacetic acid and N,N′-bis(pyridin-3-ylmethyl)oxalamide, and with the Thioxalamide Analogue

The common feature of each of the title 2:1 cocrystals is the formation of the O-H center dot center dot center dot N(pyridyl) hydrogen bonds leading to three-molecule aggregates. The persistent formation of the O-H center dot center dot center dot N(pyridyl) hydrogen bonds where other functionalities are present, e.g. amide, indicates the robustness of this supramolecular synthon. In the structure of the 2:1 4-nitrophenylacetic acid N,N'-bis(pyridin-3-ylmethyl)oxalamide cocrystal, (1), the amide-H forms a hydrogen bond with the hydroxyl group so that rows of N,N'-bis(pyridin-3-ylmethyl)oxalamide molecules are linked into a supramolecular tape via 4-nitrophenylacetic acid molecules. In the N,N'-bis(pyridin-3-ylmethyl)thioxalamide derivative, (2), the thioamide-H atom only forms an intramolecular N-H center dot center dot center dot S contact. Nevertheless, a supramolecular tape is formed but mediated by C-H center dot center dot center dot O(nitro) interactions. Compound (1) crystallizes in the triclinic space group PA-1 with a = 8.195(2) , b = 9.502(3) , c = 9.999(3) , alpha = 90.631(3)A(0), beta A = 102.796(5)A(0), gamma A = 108.075(5)A(0), and Z = 1 (three molecule aggregate). Compound (2) also crystallizes in the triclinic space group PA-1 with a = 8.0772(12) , b = 10.2111(12) , c = 10.2563(17) , alpha = 71.319(10)A(0), beta A = 77.777(11)A(0), gamma A = 67.660(9)A(0), and Z = 1 (three molecule aggregate). In each cocrystal the carboxylic acid-OH interacts with the pyridyl-N atom via a hydrogen bond to result in a three-molecule aggregate. In the N,N'-bis(pyridin-3-ylmethyl)oxalamide cocrystal, these are linked into a chain via amine-H center dot center dot center dot O(carboxylic acid) interactions.