For the reversible processes the mid-point values (Em) were determined from the average of the peak anodic potential (Epa) and peak cathodic potential (Epc). In addition, the peak-to-peak separation (ΔEp) was determined from the difference between the Epa and the Epc. For the irreversible processes, the peak potential (Ep) is reported (Table ). with Epa ranging from 0.3-0.5 V at a scan rate of 250 mV s -1 . In the absence of the protective nafion coating, the sample desorbs from the electrode, due to solubility and likely decomposition of the oxidised product. However, in the presence of the protective nafion coating, a degree of chemical reversibility is observed for this process, with ΔEp varying from 110 (1-Lu) to 570 mV (1-Gd). Scanning in the negative direction affords two irreversible reduction processes (II and III) at ca. -1.5 V and -1.9 V respectively at a scan rate of 250 mV s -1 . Process I is assigned to an oxidation of the Br4catH -ligands to tetrabromosemiquinonate (Br4SQ •-). Process II and III are assigned to reduction of tpa, consistent with other tpa-containing complexes. It is informative to compare the oxidative behaviour of 1-RE with that measured in the solid state via similar means for the family of [RE III (18-c-6)(Br4cat)(NO3)] (18-c-6 = 18-crown-6) complexes with doubly deprotonated Br4cat 2-ligands. The literature complexes exhibit two oxidations in the potential range 0.2 to 0.5 V vs Fc + /Fc, assigned as sequential one-electron oxidations to the semiquinonate and quinonate ligands. The first of these processes is quasireversible, while the second is irreversible and associated with desorption of the sample from the electrode. In contrast, only process I is observed for 1-RE in the solvent window up to 2.0 V (Figure ). The potential is similar to the first oxidation process measured for [RE III (18-c-6)(Br4Cat)(NO3)], supporting the assignment as oxidation to Br4SQ •-. The lack of a second oxidation process is consistent with process I involving a concerted three-electron oxidation of all three Br4catH -ligands, although it is not possible to directly confirm the number of electrons transferred with solid state voltammograms measured in this way. All attempts at synthetic oxidation of 1-RE to isolate a putative oxidised analogue resulted in decomposition during work-up, consistent with instability of the semiquinonate-containing oxidised product.