Study of Conformational and Supramolecular Structural Stability of Propylene-Bridged 2-Pyridone Dimers

In quest of the role of noncovalent interaction for the preference of inter and intramolecular stacking phenomenon, we synthesized O/O (1), N/O (2) and N/N (3) isomeric dimers of 3-cyano-4,6-dimethyl-2-pyridone linked through propylene chain. The direct evidence of noncovalent interactions and conformation of all the three isomers were obtained by single crystal X-ray diffraction analysis and conformational stability was evaluated through density functional theory. Isomers 1 and 2 were crystallized in stable conformation while isomer 3 was crystallized in constraint geometry which was further confirmed by differential scanning calorimetry analysis. The supramolecular structure in isomer 1 showed the helical geometry, isomer 2 showed the parallel stacking and pleated structure, while isomer 3 showed only pleated structure.