Synthesis and Characterization of Fe III/Co III/Cu II Complexes with Schiff Base Liangd and Their Hybrid Proteins, Superoxide Dismutase (SOD) Activity and Asymmetric Catalytic Oxidation of Sulfides

Three transition metal complexes (M = Fe III , Co III , Cu II ) were synthesized by hydrothermal method from bis(2-hydroxy-1-naphthalene-formaldehyde) 3,4-diaminobenzoic acid (H 3 L). They were characterized by infrared spectroscopy, elemental analysis, mass spectrometry. Artificial enzymes were constructed by hybridizing bovine serum albumin (BSA) with the metal complexes and characterized by UV-Vis and MALDI-TOF-MS. The binding of metal complexes with BSA was studied by UV-Vis spectroscopy, Raman spectroscopy, fluorescence spectroscopy, and circular dichroism spectroscopy. The secondary structure changes of BSA caused by the binding of metal complexes were investigated. All the three metal complexes can cause the intrinsic fluorescence quenching of BSA, which is mainly static quenching. The addition of metal complexes changed the conformation of BSA and decreased the content of α–helix structure. The activity of SOD was measured by xanthine oxidase-NBT method. Antioxidant activity tests showed that all metal complexes exhibited certain SOD activity, which increased after the formation of hybrid proteins. Asymmetric oxidation of thioether catalyzed by artificial enzymes was studied. The optimum reaction conditions were obtained by optimizing the reaction conditions. Substrate universality experiments were carried out under the optimum reaction conditions, showing good activity and enantioselectivity, with enantioselectivity up to 81%.