Synthesis, spectral, magnetic properties, electrochemical evaluation and SOD mimetic activity of four mixed-ligand Cu(II) complexes

Four new methylsalicylato copper(II) complexes are reported. Despite common coordination environment {CuO2N2O′2} various supramolecular structures were found. The exceptionally low SOD-like activity of one of complexes was found, which appears to be related to the distortion of its coordination environment. [Display omitted] •Four new methylsalicylato copper(II) complexes were synthesized and characterized.•SOD activity and the electrochemical behavior of complexes are in good agreement.•Best scavenging ability appears to be related with the structural distortion. Four new methylsalicylato copper(II) complexes with formula [Cu(4-Mesal)2(2-Meim)2] (1), [Cu(4-Mesal)2(im)2] (2), [Cu(3-Mesal)2(bzim)2]·2H2O (3), [Cu(5-Mesal)2(im)2]n (4) (where 3-Mesal−=3-methylsalicylato, 4-Mesal−=4-methylsalicylato, 5-Mesal−=5-methylsalicylato anion, im=imidazole, 2-Meim=2-methylimidazole and bzim=benzimidazole) are reported. The solid state complexes were characterized by IR, UV–Vis, EPR, X-ray and magnetic measurements. Despite common coordination environment {CuO2N2O′2} different supramolecular structures were found for the compounds: 1 is a 1-D supramolecular chain, 2 and 3 form 2-D supramolecular networks and 4 is a 1D coordination polymer. The superoxide dismutase-like (SOD-like) activity of complexes 1–4 was studied in solution by NBT assay, compared with the activity of the parent ligand, copper acetate and native SOD enzyme and correlated to the redox stability determined by cyclic voltammetry. The exceptionally low SOD-like activity of 3, its lower redox reversibility and higher electron-withdrawing ability could be related to the lowest axial distortion of its coordination environment.