A novel Schiff base ligand and its metal complexes: Synthesis, characterization, theoretical calculations, catalase-like and catecholase-like enzymatic activities

Abstract

In this study, a new Schiff base (H2L), which has not been recorded in the literature, and its metal complexes with general formula [ML].(H2O) [M: Cu(II) and Mn(II)] were synthesized and their structures were elucidated. Techniques such as 1H- and 13C-NMR, FT-IR, UV–vis, TG-DTG, molar conductivity, magnetic susceptibility, ICP-OES, and elemental analysis were used to characterize the structures of the Schiff base and metal complexes. According to the analysis's findings, the complexes' metal:ligand ratio was 1:1. Additionally, the 6-311G(d,p) and LANL2DZ basis sets of the DFT/B3LYP method were used to calculate the optimized molecular geometries of the H2L and its metal complexes, respectively. Additionally, the synthesized compounds' molecular electrostatic potential (MEP) diagrams, frontier molecular orbitals (HOMO-LUMO), chemical shift values for the 1H- and 13C-NMR, vibrational frequencies, and wavelengths of electronic transitions were all determined. Experimentally obtained results were verified with theoretical data that matched well. [CuL].(H2O) and [MnL].(H2O) were examined for their catalase-like and catecholase-like enzymatic activities using volumetric and spectrophotometric techniques, respectively. For this objective, the catalytic activities of the synthesized molecules in the disproporsion reaction of H2O2 in the presence of 1-methylimidazole and the oxidation reaction of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone in aerobic medium were investigated. According to the enzyme-like studies, [MnL].(H2O) was more catalytically active than [CuL].(H2O) in both of the mentioned reactions.