ELECTROCHEMISTRY OF CHROMIUM(II) HEXACYANOCHROMATE(III) AND ELECTROCHEMICALLY INDUCED ISOMERIZATION OF SOLID IRON(II) HEXACYANOCHROMATE(III) MECHANICALLY IMMOBILIZED ON THE SURFACE OF A GRAPHITE ELECTRODE

Immobilized on the surface of a graphite electrode, solid chromium(II) hexacyanochromate exhibits the reversible reduction-oxidation response of the hexacyanochromate system. The reduction is accompanied by intercalation of alkali metal ions. At room temperature, iron(II) hexacyanochromate(III) undergoes an electrochemically induced isomerization to chromium(III) hexacyanoferrate(II), when the compound is immobilized on the surface of a graphite electrode. This isomerization is a pseudo zero-order reaction within an initial period. The rate constant is 4 x 10(-9) mol/s at 22 degrees C. The isomerization results from ligand labilization, caused by the reduction of chromium(III) to chromium(II), and involves fast exchange between water molecules and cyanide ions.