After demonstrating this trade-off for the F-substituted AQ and BQ series, we posed the question if it is possible to overcome this trade-off using other functional groups. i.e. can we favour the EE step without disfavouring the C step significantly, thereby falling below the linear fit (blue solid lines in Figures , and the plot is again colour-coded according to how the thermodynamics of cathodic activation and nucleophilic addition are changed from that of unsubstituted AQ. The unfavourable relationship still remains: substitution of EWGs favours the EE step but disfavours the C step while substitution of EDGs favours the C steps but disfavours the EE steps. For most substituents, substitution closer to the carbonyl group at position 1-leads to a higher ∆G • C due to steric hindrance between the captured CO 2 and the substituents. The tuning window of these single substitutions is approximately 0.5 V for E • EE and 40 kJ mol -1 for ∆G • C . Although these mono-substituted derivatives do not all fall on the same linear fit for the F-substituted AQ series, the deviation from the trend is small. It is useful to tie these results back to the role of the electron density in the oxyanion Q 2-. Delocalisation of the electron density around the ring would stabilise the quinone in its dianion Q 2-form, meaning the quinone is less likely to be re-oxidised by O 2 after being electrochemically reduced, but also less likely to have good nucleophilicity to react with CO 2 .