Mass Spectrometry of Metallofullerenes

Abstract

Fullerenes with a metal atom inside of the cage, metallofulierenes, were produced by either laser vaporization or a graphite arc and characterized using a variety of mass spectrometric methods. First, yttrium-fullerene adducts were formed by direct laser vaporization of samples consisting of graphite, yttrium oxide and fullerenes. Fragmentation and oxidation ion/molecule reactions showed that the laser-generated adducts are endohedral complexes (Y,@Cj), in contrast to externally-bound Y(C,)+ species formed by gas-phase reactions. In addition, evidence was obtained for laserinduced bulk coalescence reactions yielding the metallofullerenes. Second, negative ion/desorption chemical ionization mass spectrometry was used to characterize metallofullerenes in arc-generated soot, pyridine extracts and the extract residue. The pyridine extracts of La 2 0 3 /graphite soot contain mostly La@Cs 2 and La 2 @Cs 0 , in addition to (empty) fullerenes. However, the raw soot and the extract residue contain a broader range of metallofullerenes with relative abundances different than those observed from the extract (e.g. abundant La@C6 0 , La@C 7 ) 0 and La@C 7 4 ). The thermal desorption behavior of the doped and undoped fullerenes indicate an interaction between the C. and LaQ@C, species. Analysis of aqueous solutions of dried pyridine extracts of LaO 3 /graphite soot show C. and La•@C,, which is consistent with the possible presence of metallofullerene/ fullerene ionic complexes, (La,@C)+C,-.