Solution Redox Couples for Electrochemical Energy Storage: I . Iron (III)‐Iron (II) Complexes with O‐Phenanthroline and Related Ligands

Iron (III)‐Iron (II) complexes with o‐phenanthroline and related ligands have been examined by electrochemical techniques in aqueous media with respect to their suitability as redox couples for electrochemical energy storage. The iron (II) complexes undergo a rapid 1 electron oxidation at graphite and platinum electrodes to yield iron (III) complexes; these complexes showed varying stabilities depending on the nature of the substituents on the complexes. The iron (II) complexes examined in this study were formed with ( i ) monodentate, ( ii ) bidentate, or ( iii ) tridentate ligands. The redox couples have a higher value which has been a positive consideration in the storage. Although the aquo iron (II)‐ iron (III) couple has an less than the complexes, it certainly has shown greater promise in terms of storage stability. The kinetics of iron (II) complexation has been followed by cyclic voltammetry.