Catalase and catecholase-like activities of manganese and copper complexes supported by pentadentate polypyridyl ligands in aqueous solution
Dóra Lakk-Bogáth, Patrik Török, Michel Giorgi, József Kaizer
Abstract
Novel manganese(II) complex, [MnII(2PyN2Q*)(OTf)]OTf (1) with racemic pentadentate polypyridyl ligand (2PyN2Q* = N,N-bis(2-quinolylmethyl)-1,2-di(2-pyridyl)ethylamine; OTf = CF3SO3) was synthesized and characterized by IR, UV-Vis, ESI-MS and X-ray measurements. The formation of its high-valent species, [MnIV(2PyN2Q*)(O)](OTf)2 was confirmed by UV-Vis measurements. Catalytic activities of compound 1 for the disproportionation of H2O2 as catalase mimics, and for the oxidation of catechol derivatives as catecholase mimics were investigated in buffered aqueous solution compared to our previously published [CuII(N4Py*)(CH3CN)](OTf)2 (2) (N4Py* = N,N-bis(2-pyridylmethyl)-1,2-di(2-pyridyl)ethylamine), [MnII(N4Py*)(OTf)]OTf (3) and [FeII(N4Py*)(CH3CN)](CO4)2 (4) complexes. Based on preliminary reaction kinetic measurements, an opposite order (trend) of reactivity was observed for the two systems: 4 (KM = 1.39 M) > 3 (1.26 M) > 1 (0.91 M) > 2 (0.31 M) for the catalase-like, and 1 ≈ 2 > 3 > 4 for the catecholase-like activity of the complexes.