~(13)C and ~(139)La NMR Studies of La_2@C_(80): First Evidence for Circular Motion of Metal Atoms in Endohedral Dimetallofullerenes

摘要

Endohedral metallofullerenes have attracted special interest as spherical molecules with novel properties that are not expected from empty fullerenes. The higher fullerenes can even encapsulate two metal atoms inside the carbon cages to form soluble and relatively air-stable endohe'dral dimetallofullerenes. Because of the difficulty in producing pure samples in large quantities, experimental characterization of these species has been hindered. Important progress was marked by the successful isolationand purification of endohedral dimetallofullerenes such as Sc_2 @ C_(84) and La_2 @ C_(80) in macroscopic quantities. This has made it possible to investigate redox properties and reactivity. STM and TEM studies were also carried out in an attempt to confirm that two metal atoms are inside the fullerene cages.