Synthesis, crystal structure characterization, DFT calculations, Hirshfeld surface analysis and 3D energy frameworks of triazole pyridazine derivatives: Theoretical and experimental studies

Abstract Recently, pyridazine derivatives have shown considerable biological properties such as anti-tumor and anti-inflammatory activity. The studied compounds 6-chloro-3-[(4-methylphenoxy)methyl][1,2,4] triazolo[4,3-b]pyridazine (8a) and 6-chloro-3-[(4-fluorophenoxy)methyl][1,2,4] triazolo[4,3-b]pyridazine (8b) have been synthesized and characterized by NMR, IR and mass spectral studies, and finally, the structures were confirmed by single crystal X-ray diffraction technique. The compounds 8a and 8b have crystallized in the same crystal system with different space groups. Density functional theory calculations were performed to compare the theoretical and experimental results obtained from XRD. Further, DFT calculations were employed to determine HOMO-LUMO energy levels, energy gap, softness, hardness, and other quantum chemical parameters of the compounds 8a and 8b. Hirshfeld surface analysis was carried out to distinguish the different intermolecular hydrogen bonds. Energy frameworks for the compounds were constructed through different intermolecular interaction energies to know the dominant interaction energy involved in the molecular packing strength.