Study of intermolecular interactions of piroxicam polymorphs / 药学学报

ABSTRACT

Piroxicam has polymorphism. Different crystalline forms can exhibit different physicochemical properties and biological activities. Analysis of the intermolecular interactions is essential to reveal the formation mechanism and differences of polymorphs. In this paper, Hirshfeld surface analysis and semi-empirical methods were used to calculate and analyze the intermolecular interactions in seven polymorphic forms of piroxicam. The results show that the Hirshfeld surface analysis method can clearly and intuitively reveal the intermolecular interactions, among which H…H, O…H/H…O and N…H/H…N interactions account for 95% of the total energy. There are differences in the proportion and distribution of the forces of different crystal forms. The energy calculation shows that the lattice energy of the hydrate is significantly lower than that of the anhydrous forms, and in the specific energy distribution, the contribution of the dispersion force is the most prominent. Further interaction energy analysis was found that within the distance of 3.8 Å from the center of the piroxicam molecule, different crystalline forms of piroxicam molecule have different interaction energies with surrounding molecules.