Mixed Ligand Cu^IIN₂O₂ Complexes: Biomimetic Synthesis, Activities in Vitro and Biological Models, Theoretical Calculations

Abstract

Three new mixed ligand Cu^IIN₂O₂ complexes, namely, [Cu^II(2-A-6-MBT)₂­(<i>m</i>-NB)₂] (<b>1</b>), [Cu^II(2-ABT)₂­(<i>m</i>-NB)₂] (<b>2</b>), and [Cu^II(2-ABT)₂­(<i>o</i>-NB)₂] (<b>3</b>), (2-A-6-MBT = 2-amino-6-methoxybenzothiazole, <i>m</i>-NB = <i>m</i>-nitrobenzoate, 2-ABT = 2-aminobenzothiazole, and <i>o</i>-NB = <i>o</i>-nitrobenzoate), have been prepared by the biomimetic synthesis strategy, and their structures were determined by X-ray crystallography studies and spectral methods. These complexes exhibited the effective superoxide dismutase (SOD) activity and catecholase activity. On the basis of the experimental data and computational studies, the structure–activity relationship for these complexes was investigated. The results reveal that electron-accepting abilities of these complexes and coordination geometries have significant effects on the SOD activity and catecholase activity. Then, we found that <b>1</b> and <b>2</b> exerted potent intracellular antioxidant capacity in the model of H₂O₂-induced oxidative stress based on HeLa cervical cancer cells, which were screened out by the cytotoxicity assays of different kinds of cells. Furthermore, <b>1</b>–<b>3</b> showed the favorable biocompatibility in two different biological models: <i>Saccharomyces cerevisiae</i> and human vascular endothelial cells. These biological experimental data are indicative of the promising application potential of these complexes in biology and pharmacology