The electronic spectra of 1-RE•0.5 MeCN were measured as diffuse reflectance (Figure ) and the spectra transformed using the Kubelka-Munk equation (k/s = (1 -R) the sample). All compounds exhibit two intense and sharp bands in the UV region at 254 nm and 304 nm, which correspond to ligand-based charge transfer process (- * transitions). The 254 nm peak is assigned to the combined Br4catH -and tpa ligand-based absorption, and the 304 nm peak assigned as an additional feature from the Br4catH -ligand, as observed previously. An additional broad band centred at 386 nm is present only for 1-Eu•0.5 MeCN and assigned as a ligand to metal charge transfer (LMCT) transition from the Br4catH -ligand to the Eu 3+ metal centre. A similar band has been observed for a number of complexes of Eu with doubly deprotonated Br4cat 2-ligands. The electron withdrawing nature of the bromo-substituted analogue decrease the highest occupied molecular orbital compared to other substituted catecholate ligands (e.g. 3,5-dtbcat 2-) which allow LMCT in the visible range. To the best of our knowledge, this is the first observation of an equivalent LMCT involving the monoprotonated Br4catH -. The potential for redox-activity and the atypical coordination mode of the Br4catH -ligands prompted an investigation of the electrochemical properties. The lack of solubility prevented conventional solution measurements, so voltammetry was performed in the solid state (Figure and Figure ). Powdered samples were immobilised as a film on a working glassy carbon electrode then sealed with nafion. Tetrabutylammonium hexafluorophosphate (0.25 M) was used as an electrolyte in MeCN. Three redox processes are evident for all compounds, an oxidation (I) with varying degrees of reversibility and two irreversible reductions (II and III).