Catalytic Interconversion of the Quinone/Hydroquinone Couple by a Surface-Bound Os(III/II) Polypyridyl Couple

Abstract

Surface catalytic interconversion of hydroquinone (H2Q) and 1,4-benzoquinone (Q) occur at a fluorine-doped tin oxide electrode (FTO) modified by the addition of the surface-bound couple, [Os(bpy)2((4,4′-PO3H2)2bpy)]3+/2+ (OsP2+, bpy = bipyridine and 4,4′-(PO3H2)2 = 4,4′-phosphonato-2,2′-bipyridine). Significant rate enhancements are observed with the added solution buffers—phosphate, acetate, and citrate—and a surface-bound, pyridine base. Analysis of cyclic voltammograms for the 2e–/2H+ couple, by use of the Butler–Volmer equation, point to the importance of acid–base effects and H-bonding in enhancing the reaction rate at the electrode.