Synthesis, spectroscopic characterization, physicochemical properties, biological activity and docking study of Cu (II) and La (III) metal complexes with a Schiff base ligand

Abstract

The current study reports the synthesis of Schiff base ligand, N'-(2,4-dihydroxyphenyl)(phenyl)methylene)-4-methylbenzohydrazide (HL) by reversible condensation reaction of primary amine with carbonyl compound. Further, Schiff base ligand was utilized to prepare the Cu(II) and La(III) metal complexes M1L and M2L, respectively. 1H NMR, powder X-ray diffraction, FTIR, elemental analysis and thermogravimetric studies were used to characterize the Schiff base ligand and its metal complexes. The data of 1H NMR and FTIR studies disclose that ligand exhibits isobidentate behavior and metal complexes formation through the significant peaks. The qualitative pattern of the distributed intensity and crystalline structure of the Cu and La complexes were observed by the powder XRD data. ESR spectra of the Cu(II) complex exhibits an axial type symmetry g|| > g⊥ > 2.0023. In addition, the zones of inhibition (mm) of the Schiff base ligand and its metal complexes against gram-positive and gram-negative bacteria such Enterococcus faecalis, Escherichia coli, and Bacillus subtilis were measured at least three times under identical conditions. Molecular docking method was used to establish the position of the links, energy account, and molecular distance that contribute to the interaction between the complexes. An interaction results show that the synthesized HL and its M1L, M2L complexes effectively interact with the protein receptor molecule, which has a positive impact on the free binding energy. From the data of interaction energy measurements M1L complex has significantly more stable interaction and lower binding energy than compare to M2L complex.