Description:
<jats:p>Due to their high Brønsted basicity and redox properties, guanidino‐functionalized aromatics (GFAs) are privileged proton‐coupled electron‐transfer (PCET) reagents. Herein we show that the GFA 1,2,4,5‐tetrakis(tetramethylguanidino)‐benzene (<jats:bold>1</jats:bold>), after being oxidized to the green dicationic state (<jats:bold>1</jats:bold><jats:sup>2+</jats:sup>), can bind one or two protons, resulting in the blue monoprotonated trication (<jats:bold>1</jats:bold>+H)<jats:sup>3+</jats:sup> and the orange diprotonated tetracation (<jats:bold>1</jats:bold>+2H)<jats:sup>4+</jats:sup>, realizing the first purely organic PCET reagent that can be diprotonated in its oxidized state. With trifluoroacetate counterions, low‐barrier hydrogen‐bonding is observed, allowing to shift protons reversibly in dependence of the temperature and solvent polarity between <jats:bold>1</jats:bold><jats:sup>2+</jats:sup> and trifluoroacetate. The protonation of <jats:bold>1</jats:bold><jats:sup>2+</jats:sup> has dramatic effects on its oxidation capabilities.</jats:p>