Crystal structure, Hirshfeld surface analysis, and DFT calculation of 2-pyrazoline-4-ols

Abstract

DFT computational study at B3LYP/6−31++G** level of theory and single crystal structure analysis of three crystallized 2-pyrazoline-4-ols (DHPZ-OH) were carried out to compare the differences in the structural orientation, electronic and bonding characteristics in both investigations. X-ray crystallography showed that compounds 1, 2, and 3 are crystallized in monoclinic, monoclinic, and triclinic systems, with the space group P21/c, P21/n, and P-1, respectively. Owing to the presence of two neighboring stereocenters, these crystal structures represent the enantiomeric pairs in the crystal packing. Hirshfeld surface analysis (HS) showed that both conventional donor (D)/acceptor (A)-interactions, such as D-H‧‧‧‧‧A, H‧‧‧‧‧N2 and D‧‧‧‧‧O interactions between the appropriate positions in the molecules. Also, the donor/acceptor interaction between the aromatic rings (π-π stacking) ensured the stabilization and orientation of the molecules in the crystal packing. The computational results concerning the geometrical parameters such as the bond lengths, bond torsion, and bond angles were compared with the crystal data. The energies of the HOMO and the LUMO orbitals, and the molecular electrostatic potential (MEP) were generated using the density functional theory (DFT). The MEP map showed the areas of the negative potential region around the electronegative atoms O24 and N2, while the maximum positive sites were around the hydrogen atom attached to O24.