DFT study and Hirshfeld surface analysis of third polymorph of sulfamerazine

Abstract

The third polymorph of sulfamerazine crystallized as two molecules per asymmetric unit having orthorhombic system with space group Pna21. The ab-initio and density functional theory (DFT) are used to optimize the molecular structure and to calculate frontier molecular orbitals and Mullikan charge distributions. The optimized geometry reveals that the predicted geometry can well reproduce structural parameters. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. The Hirshfeld surfaces and consequently the fingerprint analysis have been performed to study the nature of interactions and their quantitative contributions towards the crystal packing. Finally, Hirshfeld surfaces, fingerprint plots and structural overlay are employed for a comparison of the two independent molecules in the asymmetric unit of sulfamerazine and also, for a comparison of reported sulfamerazine polymorph which is in the monoclinic crystal system.