Electrochemical Properties of

[Ru(edta)(H2O)]- is strongly adsorbed on a zirconium(IV) oxide-coated silica gel surface. The immobilized complex showed an electrochemical response due to the Ru(II)/Ru(III) redox couple. By substituting the coordinated water molecule in the adsorbed complex, the midpoint potentials shifted in the order (in mV) water, -290; thiocyanate, -200; pyridine, -180; 4-cyanopyridine, -80; and pyrazine, -50 vs SCE.