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Abstract

Systematic electrochemical studies have been carried out on a series of covalent fullerene C₆₀ derivatives ranging from mono- through hexakis-adducts. The aim was to correlate the changes in redox properties with the degree, pattern and nature of the functionalization. In the studied series the reduction potentials became increasingly more negative, and the redox steps more irreversible with increasing number of addends. This behavior indicates a rise of the energies of the LUMO orbitals with functionalization that has been confirmed by theoretical ab initio calculations. Rather good correlation was observed between the first reduction potentials and the energy level of the LUMO orbitals. The reductions are also dependent on the spatial location of the addends on the surface of the fullerene sphere. Further, with increasing number of addends, the oxidation of the derivatives are facilitated from the mono to the tris-adduct, while for higher adducts the potential remains nearly the same. This indicates that the oxidation occurs on a common substructural element present in the remaining chromophore.