Fullerenes metal inclusion compounds

Endohedral metal fullerenes can be detected in relatively small amounts in the mass spectra in the laser vaporization cluster beams (vide supra). However, macroscopic quantities of these compounds may be produced rather readily either by vaporization in a laser furnace apparatus or by arc-burning of a composite rod of graphite and the corresponding metal oxide. In Fig. 4.50, a mass spectrum which illustrates the formation of a series of fullerene endohedral yttrium complexes obtained by laser vaporization of a composite graphite/ Y2O3 rod at 1200 ""C is reproduced. Among these species there is also one, Y2 Cs2, which corresponds to the inclusion of a metal cluster in the fullerene ball. 

As can be appreciated in the examples illustrated in Table 4.14, a number of superconductors based on the inclusion of alkali metals and thalium have been prepared. Superconducting transition temperatures in these compounds are significantly higher than those observed for the correponding graphite intercalates. Apparently, in the case of the fullerenes there is a near linear relationship between the superconducting transition temperature, Tp, and the alkali metal size. Such a relationship, deduced from the correlation between Tp and the... 

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