Novel peroxidase mimics: μ-Aqua manganese–Schiff base dimers

Abstract

The interaction of manganese(II) carboxylate salts [Mn(O 2CR) 2, where R = ethane, pentane] with H 2L 1 [ N, N′-bis(3-methoxy-2-hydroxybenzaldehyde)-1,2-phenylenediamine] and H 2L 2 [ N, N′-bis(3-ethoxy-2-hydroxybenzaldehyde)-1,2-phenylenediamine] was studied. MnL 1(O 2CEt)(H 2O) ( 1), MnL 1(O 2CPe n )(H 2O) ( 2), MnL 2(O 2CEt)(H 2O) 2 ( 3) and MnL 2(O 2CPe n )(H 2O) 2 ( 4) were isolated and thoroughly characterised by elemental analysis, FAB mass spectrometry, infrared and 1H NMR spectroscopy, magnetic susceptibility measurements, molar conductivities, and cyclic and normal pulse voltammetry. Compounds 1 and 2 were crystallographically characterised revealing a tetragonally elongated octahedral geometry for the manganese coordination sphere and also a dimeric nature through μ-aqua bridges. Complexes 1– 4 behave as efficient peroxidase mimics in the presence of the water-soluble trap ABTS, probably due to their ease to coordinate the substrate molecule. A correlation between rhombicity of the complexes and peroxidase activity has also been established.