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

The interaction of manganese(II) carboxylate salts 2 [Mn(O2CR)(2), where R = ethane, pentane] with H2L1 [N,N'-bis(3-methoxy-2-hydroxybenzaldehyde)-1,2-phenylenediamine] and H2L2 [N,N'-bis(3-ethoxy-2-hydroxybenzaldehyde)-1,2-phenylenediamine] was studied. MnL1(O2CEt)(H2O) (1), MnL1(O(2)CPe(n))(H2O) (2), MnL2(O2CEt)(H2O)(2) (3) and MnL2(O(2)CPe(n))(H2O)(2) (4) were isolated and thoroughly characterised by elemental analysis, FAB mass spectrometry, infrared and H-1 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 mu-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. (c) 2006 Elsevier Inc. All rights reserved.