Heterogeneous electron transfer at endohedral fullerenes

Abstract

Endohedral fullerenes exist in a variety of redox states in dependence on the type and the number of metals incorporated. This redox state can be changed by heterogeneous electron transfer reactions. We studied the electron transfer at electrodes by cyclic voltammetry and spectroelectrochemistry. It is demonstrated in this paper for La@C82 and Eu@C74 that the two or three valency of the metal ion in endohedral fullerenes is caused by the type of the element and not by the shape and redox properties of the carbon cage. For La@C82 it is shown that the charge at the carbon cage is varied by heterogeneous electron transfer and in the higher cathodic region a new redox state of La inside of La@C82¯ was found. At the Eu@C74 which was also studied by Raman spectroscopy and which has the metal in the 2+ state it is shown by ESR spectroscopy that the electron transfer does not result in a paramagnetic anion.