ELECTROCHEMICAL AND SPECTRAL STUDIES OF DIMERIC IRON(3) COMPLEXES

The electrochemical behavior of the monomeric (EDTA-FemOH2-) and dimeric ((EDTA-FeIII)2O4-) complexes present at equilibrium in the FeIII-EDTA system at pH 9 has been characterized. Fast-sweep cyclic voltammetry in pH 9 buffered media reveals two reduction waves and a single anodic wave. Both the monomer and dimer, by a two-electron reduction, are reduced to ferrous monomer. In buffered media, slow-sweep linear voltammetry with thin-layer electrodes produces single cathodic and anodic waves because the dimer dissociates as the monomer is reduced. The rate constant for dissociation of dimer is estimated at 0.5 sec-1 from chronocoulometric measurements. A pathway involving solvent assistance is suggested as the mechanism of dimer breakup. © 1969, American Chemical Society. All rights reserved.