Buckminsterfullerenes as electron acceptors

Since the preparation of Buckminsterflillerene (Ceo) on a large-scale in 1990 [66], a big effort has been devoted to the exploration of the chemical and physical properties of this new allotrope of carbon [67]. 

The electron-accepting ability of the Ceo molecule in solution has been measured by charge-transfer absorption energy and also by the redox potentials, and it has been concluded that Ceo is a weak electron acceptor comparable to p-benzoquinone, 5-tetracyanobenzene or 2,3-dichloro-1,4-naphthoquinone, the adiabatic electron affinity of the Ceo molecule being estimated as 2.10-2.21 0.1 eV [70]. 

Considering that the conductivity and superconductivity of doped fullerenes is widely revised in a different chapter of this book, we will centre our attention on the use of Cso as an acceptor in the preparation of charge-transfer complexes and the redox properties of organofullerenes. 

Determination of the superconducting properties of salts prepared from Ceo and alkali and alkaline-earth metals with relatively high transition temperatures (Tc 33 K) led to the observation that the temperature Tc for the superconductivity of these fullerides was related to the size of the metallic atoms and the lattice constant [71]. Consequently, the preparation of complexes with bigger organic donor molecules was thought to increase the Tc values and a number of charge-transfer complexes with a variety of donor molecules have been prepared [70]. 

Complexation with strong electron donors such as cobaltocene [72] or tetrakis(dimethylamino)ethylene 

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