Electrochemically driven formation of a molecular capsule around the ferrocenium ion

Electrochemical experiments were used to show that the oxidation of ferrocene triggers the self-assembly of six molecules of the resocin4]arene 2 to form a molecular capsule around the oxidized, ferrocenium (+1) form. The nature of the supporting electrolyte anion is crucial for this process of electrochemically driven self-assembly. 1H NMR spectroscopic data obtained with cobaltocenium, a diamagnetic analogue of the paramagnetic ferrocenium ion, verify its encapsulation by six molecules of 2. The encapsulation of cobaltocenium was also observed in voltammetric experiments. Encapsulation of ferrocenium (or cobaltocenium) inside the large 26 capsule led to a dramatic slowing of its usually fast, one-electron electrochemical reduction to ferrocene (or cobaltocene).