Molecular structures, hirshfeld surface analysis, and spectroscopic properties of 6,8-dimethyl-3-(4-chlorophenyl)-7-oxo-7,8-dihydropyrimido[4,5-c]pyridazin-5(6H)-one and 6,8-dimethyl-3-(4-chlorophenyl)-7-thioxo-7,8-dihydropyrimido[4,5-c]pyridazin-5(6H)-one

Abstract

X-ray crystallography images are used to perform DFT studies of the structural, electronic, intermolecular energies and IR frequencies of 6,8-dimethyl-3-(4-chlorophenyl)-7-oxo-7,8-dihydropyrimido[4,5-c]pyridazin-5(6H)-one (A) and 6,8-dimethyl-3-(4-chlorophenyl)-7-thioxo-7,8-dihydropyrimido[4,5-c]pyridazin-5(6H)-one (B) using Gaussian 98 and Crystal Explorer program packages. The optimization of A and B in vacuum and solvent (ethanol) phases represent negligible changes in the bond distances, bond angles, and torsion angles. Moreover, the optimization in ethanol is closer to the X-ray crystallography data as compared to the gas phase. Moreover, the Hirshfеld surface analysis reveals that the highest amount of close contact contributions relates to H—H contacts while the lowest amount goes to Cl—Cl/Cl—Cl and C—O/O—C close contacts for A and B, respectively. The corresponding calculated IR intensity values highly match the experimental data.