Combining proton and electron transfer to modulate the stability of cucurbit[7]uril complexes

(Ferrocenylmethyl)methylammonium (1H⁺) is an excellent cationic guest for inclusion complexation by the cucurbit[7]uril host. However, deprotonation of the guest leads to a decrease of 14.8 kJ mol^-1 in the overall stability of its inclusion complex, and one-electron oxidation of the guest's ferrocene residue further diminishes the complex stability by another 12.3 kJ mol^-1. Overall, guest deprotonation followed by its oxidation constitutes an accessible method to lower the equilibrium association constant for the CB7·1H⁺ complex by more than 4 orders of magnitude.