Properties and antioxidant activity of water-soluble iron catalysts with Schiff base ligands. Comparison with their manganese counterparts

Three new iron complexes Na-2[Fe(5-SO3-salpn)(H2O)(2)]OH center dot 4H(2)O (1 center dot 4H(2)O), Na-2[Fe(5-SO3-salpnOH)(H2O)(2)]Cl center dot 7H(2)O (2 center dot 7H(2)O) and Na-2[Fe-2(5-SO3-salpentO)(mu-OAc)(mu-(OH)(H2O)(2)]OH center dot 3H(2)O (3 center dot 3H(2)O), where 5-SO3-salpn = 1,3-bis(5-SO3-salicylidenamino)propane, 5-SO3-salpnOH = 1,3-bis(5-SO3-salicylidenamino)propan-2-ol and 5-SO3-sapentOH = 1,5-bis(5-SO3-salicylidenamino)pentan-3-ol, have been obtained and characterized. The ligands tune the redox potential of 1 and 2 within the range required for superoxide dismutase activity, with 2 being less reactive as a result of the formation of an inactive dimer. Complex 3 looses acetate and converts into a mu-oxo-Fe-2 species responsible for its catalase activity. The more negative reduction potentials of 1 - 3 and their lower stability result in rates of superoxide and peroxide disproportionation 10- to 100-times slower than those of the Mn counterparts.