ABSTRACT
Endohedral metallofullerenes (EMFs) are novel hybrid molecules enclosing a variety of metal ions or metal-containing clusters in various fullerene cages.1 They have unique core-shell structures and fascinating properties that are never expected for their parent fullerenes. An intrinsic character of EMFs is the existence of charge transfer from the incarcerated metals to the outer carbon frameworks. The negatively charged cages exhibit stabilities that are mostly different from those of the neutral ones, and many labile fullerenes that violate the isolated pentagon rule (IPR)2 are therefore successfully achieved in their endohedral forms. To date, the encaged metals mainly originate from Group III (Sc, Y, and lanthanides) on the periodic table, with minority from Groups I, II, and IV.
