Fullerenes as Ligands in Metal Complexes

It follows that C6o should be able to receive up to 12 electrons. 

It must, however, be noted that under common experimental conditions one can easily detect the fourth reduction step.11 

As compiled in Table 2, the sequence C60 —1 [C60] — [C60]2- displays variations in the typical C/C bond lengths which agree with the theoretical assumption that the tlu orbitals are antibonding with respect to the 6 6 carbon/carbon double bonds and bonding with respect to the 5 6 carbon/carbon single bonds. 

It is interesting to note that the difference between the potentials of the first oxidation and the first reduction constitutes an experimental measurement of the energy separation of the HOMO/LUMO frontier orbitals. This follows that (as mentioned in the Introduction as well as in Chapter 1, Section 2.4) one assumes that in the oxidation process the electron is removed from the occupied orbital of highest energy (HOMO), whereas in the reduction process the electron is added to the unoccupied orbital of lowest energy (LUMO). In the present case, this separation is equal to AEo = +1.28 - (-1.04) = 2.32V (and hence 2.32 eV). This value is in accord with the value of 2.6 eV theoretically determined for the separation of the HOMO hu and the LUMO tiu. The relatively stable cation [C60]+ has been characterized in solution.16 

C70 also displays a one-electron oxidation with features of chemical reversibility at a potential similar to that of C60. This implies that the HOMO/LUMO separation is roughly similar in the two cases.15 

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