Tuning the catalase activity of dinuclear manganese complexes by utilizing different substituted tripodal ligands

A series of five new dinuclear manganese (II/II) compounds with derivatives of 2-{[bis(pyridin-2-ylmethyl)amino]methyl}phenol (HL1) were synthesized and structurally characterized. All complexes crystallize in monoclinic space groups and exhibit (MnMn)-Mn-... separations in the range of 3.392(8)-3.493(2) Angstrom caused by bis(mu-phenoxo) bridging modes. The derivatives of HL1 contain either electron-donating or -withdrawing substituents. A correlation between the electronic character of the different ring substituents, the redox potentials of the dinuclear transition metal complexes and the catalase activity has been revealed. In analogy to manganese catalase, all complexes show saturation kinetics at high substrate concentration. The investigated catalase activity places the compounds in the upper range of functional catalase mimics. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.