Cyclic voltammetry data measured for the catalysts and the mixtures revealed a coincidence in the potentials of the Ru(II)/Ru(III) redox process of mediators 3 and 4 and the predicted [Ru(IV)=O](2+)/[Ru(V)=O](3+) potential of catalyst 2. In contrast, the [Ru(IV)=O](2+)/[Ru(V)=O](3+) process for catalyst 1 was found to occur at a higher potential than the Ru(II)/Ru(III) redox process for 4. 
Cyclic voltammetry