Reaction of iron-EDTA chelates with the superoxide radical

Fe3+-EDTA chelates react with the superoxide radical at physiological pH values (k = 1.3 × 106M−1 s−1 at pH 7 but is lower at more alkaline pH values) but do not appear to catalyze O2 ⨪ dismutation at a significant rate. Complexes of Fe3+ with desferrioxamine, bathophenanthroline, or diethylenetriaminepentaacetic acid react much more slowly, if at all. Fe2+ complexes of EDTA, ATP, and diethylenetriaminepentaacetic acid also react with O2 ⨪ at alkaline pH values. The significance of these reactions in the mechanism of the “iron-catalyzed Haber-Weiss reaction” is discussed.