Structural Features on Polymorphism of Diclofenac Acid

A structural study of diclofenac acid was carried out by density functional theory (DFT) calculations. Five different structures were found to corresponding its minimum energy conformations. Among several interconvertible rotations, the five most stable structures were studied and the intramolecular interactions governing the corresponding conformational preferences were considered and energy values were related to each other. Some theoretical structures are in agreement with the conformations experimentally detected in polymorphic structure of diclofenac acid. Evidence for intermolecular hydrogen bonds formation, as among amine, carboxylic groups and adjacent chloro moiety leading to most stable structures in single molecule.