Cyclic voltammograms (CVs) of all samples were measured under inert (N2) conditions at room temperature on solid samples that were immobilised on a 3 mm glassy carbon electrode as a working electrode. A concentrated suspension of the compounds in spectroscopic dichloromethane was dropped onto the electrode and allowed to evaporate completely. The resulting film was then coated in 4% nafion solution, which was allowed to evaporate.