*2.3. Electrochemical Studies*

Cyclic voltammetry (CV) experiments were employed to assess the electrochemical properties and reversibility of the quinone/hydroquinone couples. The compounds were dissolved in a 0.1 M TBAPF6/CH3CN solution and the potential was swept at a rate of 100 mVs−<sup>1</sup> between a range of 800 to −1000 mV. Ferrocene was also added to the solution and used to reference the reduction potentials acquired for each couple, which are displayed in Table 2.


**Table 2.** Reduction potentials for the quinone species **4**–**8** obtained using cyclic voltammetry.

a Reduction potentials obtained at 100 mVs−<sup>1</sup> over the range 560 to −1000 mV. Potentials were referenced vs a Fc/Fc<sup>+</sup> couple.

The results indicate a direct correlation between the electron-withdrawing power of the functional group and how readily the quinone motif is reduced. The e ffect of an intramolecular amide hydrogen bond on the quinone reduction potential has been previously reported [34,42], and the trend observed for quinones **5**–**8** suggests that a similar interaction is in e ffect. The internal hydrogen bond pulls electron density away from the quinone group, allowing electrons to be accepted more easily by the system. A stronger hydrogen bond will withdraw a greater amount of electron density as evidenced by the reduction potentials of quinones **5** and **8**. The presence of strongly withdrawing bis-CF3 groups in Compound **8** results in an almost 100 mV di fference in reduction potential.

The reversibility of the quinone/hydroquinone couple was evaluated by conducting a series of cyclic voltammetry experiments with varying scan rates. The compounds were dissolved in the same solvent mixture used in the previous experiments, and voltammograms were collected between a range of 800 to −1000 mV for a range of scan rates from 20–300 mVs−1, of which an example can be viewed in Figure 4. The Randles–Sevcik equation states that for an electrochemically reversible process, a plot of Ip (peak current) against *v*1/<sup>2</sup> (root of scan rate) should return a linear relationship which passes through the origin [43]. Data were plotted for each of the quinone systems (see Supporting Information) and a linear correlation was observed for quinones **5**–**7**. Compound **8** however did not follow a linear trend and Δ Ep (the separation of the cathodic and anodic peaks) grew larger with increasing scan rate. This indicates that this redox couple is quasireversible, and that the stability of the hydrogen bond may be a ffecting the kinetics of the electron transfer process.

**Figure 4.** Overlay of cyclic voltammograms of Compound **7** recorded with increasing scan rate from 20 mVs−<sup>1</sup> to 300 mVs−1. The current response increases with scan rate.
