**3. Conclusions**

We have demonstrated that the hydroquinone/quinone redox couple can be employed in the creation of a redox-switchable chloride receptor. It was discovered that the intramolecular bond initially expected to only be present in the quinone form of the molecule was also present in the hydroquinone receptor, and it is likely this competing interaction led to a reduction in binding capability. Converging trends in binding a ffinity due to e ffects dictated by the amide carbonyl resulted in the receptor couples for Compounds **1** and **2** having the greatest di fference in binding ability between the two forms of the switch. CV studies highlighted the e ffect on reduction potential of increasing electron-withdrawing groups, and the results for Compound **8** suggested a loss in reversibility. This can be taken as further evidence of the inhibitory e ffect of benzamide-appended electron-withdrawing groups on the e ffectiveness of this class of receptor. Overall, this work has verified the ability of hydroquinone oxidation as a method of reducing anion binding a ffinity. We are currently exploring the properties of other receptors containing quinoid systems.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2624-8549/1/1/7/s1.

**Author Contributions:** Conceptualization P.A.G. and D.A.M.; synthesis, anion binding studies and electrochemical studies D.A.M.; electrochemical studies, X.F. and D.M.D.; crystallography, W.L.; writing—original draft preparation, D.A.M. and P.A.G.; supervision, P.A.G.

**Funding:** This research was supported by the Australian Research Council (DP180100612) and the University of Sydney.

**Conflicts of Interest:** The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
