Mixed ligand Cu(II)N2O2 complexes: biomimetic synthesis, activities in vitro and biological models, theoretical calculations.

Three new mixed ligand Cu(II)N2O2 complexes, namely, [Cu(II)(2-A-6-MBT)2(m-NB)2] (1), [Cu(II)(2-ABT)2(m-NB)2] (2), and [Cu(II)(2-ABT)2(o-NB)2] (3), (2-A-6-MBT = 2-amino-6-methoxybenzothiazole, m-NB = m-nitrobenzoate, 2-ABT = 2-aminobenzothiazole, and o-NB = o-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 1 and 2 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, 1-3 showed the favorable biocompatibility in two different biological models: Saccharomyces cerevisiae and human vascular endothelial cells. These biological experimental data are indicative of the promising application potential of these complexes in biology and pharmacology.