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

Abstract

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.