We used here a three-electrode cell configuration consisting of MA/FTO/glass as the working electrode (= anode) and Pt and Ag/Ag + wires as the counter (= cathode) and quasi-reference electrodes, respectively. An aqueous solution of LiClO4 (0.1 M) was used as an electrolyte with pH 6.9. Cyclic voltammetry (CV) measurements, recorded with a scan rate of 0.1 V/s, showed reversible redox processes at 0.69 V and 0.44 V with half wave redox potentials, E½, of 0.56 V (versus Ag/Ag + ; 0.1 M LiClO4/H2O) (Figure ). These observations are indicative of a Fe 2+/3+ redox couple. These redox processes occur under lower potentials, compared with the use of organic media. CV was measured at different scan rates (0.1-0.9 V/s). Clear exponential and linear correlations (R 2 > 0.99 for all fits) were observed between the peak currents and scan rates and their square root (Figure ). These correlations indicate that the redox processes are diffusion controlled. The diffusion coefficient, Df, for MA1 is ∼3.7 × 10 -8 cm 2 •s -1 for both the oxidation and reduction processes; it is calculated using the Randles-Sevcik equation. Spectroelectrochemical (SEC) measurements, recorded in the transmission mode, show the characteristic, broad Metal-to-Ligand Charge-Transfer (MLCT) band of the iron(II) complex at λmax ≈ 575 nm (Figure ). The MLCT band disappears upon the one-electron oxidation of the Fe 2+ centers. This redox process is fully reversible and is accompanied by color-colorless-color transitions, which are clearly observable by the naked eye (Figure ). The high transparency of the MA, upon applying an oxidative current, indicates that all metal centers are electrochemically addressable at the applied scan rate.