Tuning the Redox Properties of Fullerene Clusters within a Metal–Organic Capsule

A porphyrin-edged metal–organic tetrahedron forms host–guest complexes containing 1–4 equiv of fullerene C₆₀, depending on the solvent employed. The molecules of C₆₀ were bound anticooperatively within well-defined pockets; an X-ray crystal structure of three fullerenes inside the tetrahedron was obtained. Electrochemical measurements revealed that the electron-accepting properties of the fullerenes inside the capsules were altered depending on the mode of encapsulation. The binding of multiple fullerenes was observed to increase the electron affinity of the overall cluster, providing a noncovalent method of tuning fullerene electronics.