Generation of Endohedral Fullerenes

To facilitate discussion of these somewhat more complicated fullerenes with one or more atoms inside the cage, a special symbolism and nomenclature was introduced [66]. Thereby the symbol is used to indicate the atoms in the interior of the fullerene. All atoms listed to the left of the symbol are located inside the cage and all atoms to the right are a part of the cage structure, which includes heterofullerenes, e.g. C59B. A Cgg-caged metal species is then written as M Cgg, expanded as metal at Cgg . The corresponding lUPAC nomenclature is different from the conventional M C representation. lUPAC recommend that M C be called [rt]fuUerene-incar-lanthanum and should be written iMC [4]. 

The removal of the radical electron corresponds to the first oxidation process. The resulting cation should be diamagnetic. The first reduction is relatively easy, because filling of the HOMO leads to the closed shell species La Cg2T Theoretical calculations predicted that the location of the lanthanum within the cage is off-center, which allows a stronger interaction with carbon atoms of the fullerene sphere [81- 3]. 

Dynamic circular motion of the metal atoms within La2 CgQ the cage has been investigated by NMR spectroscopy [77, 84, 85]. Synchrotron X-ray diffraction, 

NMR and ultra-high vacuum scanning tunneling microscopy (UHV-STM) studies also demonstrate the encapsulation of the metal atoms by the carbon cage [75, 76]. 

Another striking development with endohedral fullerenes was the synthesis of N C5q, the first example of encapsulation of a reactive nonmetal atom [128-132]. 

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