Comparative study of (Z)-4-oxo-4-ureido-but-2-enoic acid and p-toluenesulfonic acid 3-nitrophenyl ester by crystal engineering and DFT calculation

In this work, we reported on the synthesis and characterization of (Z)-4-oxo-4-ureido-but-2-enoic acid and p-toluenesulfonic acid 3-nitrophenyl ester and their detailed crystal structure information were studied. The crystallization of (Z)-4-oxo-4-ureido-but-2-enoic acid results in reduced π -conjugation in the molecule and weaker intra-molecular hydrogen bonding. The main driving force for the molecular self-assembly of (Z)-4-oxo-4-ureido-but-2-enoic acid was found to be the strong intermolecular hydrogen bonds . Compared with (Z)-4-oxo-4-ureido-but-2-enoic acid with six type of strong H-bonds, p-toluenesulfonic acid 3-nitrophenyl ester possesses much lower melting point (110–111°C), average packing energy (−3.7   kcal   mol −1 ), molecular deformation energy (−0.6   kcal   mol −1 ) and highest torsional angle change (9.3°). This can be ascribed to the week intermolecular interaction between center molecule and adjacent molecules.