Tetra-, penta- and hexacoordinate copper(II) complexes with N3 donor isoindoline-based ligands: Characterization and SOD-like activity

► Comparison of 4-, 5- and 6-coordinate Cu(II) bis(N-arylimino)isoindolinate complexes. ► Coordination number dependent on counterion and synthetic method. ► Coordinated ligand loses proton in solution upon addition of base. ► Superoxide scavenging activities are highest with outer-sphere counterions. ► Activity increases with the metal-based Epa.