Increased Efficiency of a Functional SOD Mimic Achieved with Pyridine Modification on a Pyclen-Based Copper(II) Complex.

A series of Cu(II) complexes with the formula [CuRPyN3]2+ varying in substitution on the pyridine ring were investigated as superoxide dismutase (SOD) mimics to identify the most efficient reaction rates produced by a synthetic, water-soluble copper-based SOD mimic reported to date. The resulting Cu(II) complexes were characterized by X-ray diffraction analysis, UV-visible spectroscopy, cyclic voltammetry, and metal-binding (log β) affinities. Unique to this approach, the modifications to the pyridine ring of the PyN3 parent system tune the redox potential while exhibiting high binding stabilities without changing the coordination environment of the metal complex within the PyN3 family of ligands. We were able to adjust in parallel the binding stability and the SOD activity without compromising on either through simple modification of the pyridine ring on the ligand system. This goldilocks effect of high metal stabilities and high SOD activity reveals the potential of this system to be explored in therapeutics. These results serve as a guide for factors that can be modified in metal complexes using pyridine substitutions for PyN3, which can be incorporated into a range of applications moving forward.