Scandium Clusters in Fullerene Cages

Abstract

The production and spectroscopic characterization of fullerene-encapsulated metal-atom clusters is reported. In particular, both solution and solid-state electron paramagnetic resonance (EPR) spectra of Sc₃C₈₂ have been obtained. ScC₈₂ also gives an EPR spectrum, but Sc₂C_n species—the most abundant metallofullerenes in the mass spectrum—are EPR-silent even though Sc₂ is EPR-active in a rare-gas matrix at 4.2 K. The results suggest that the three scandium atoms in Sc₃C₈₂ form an equilateral triangle—as was previously suggested for Sc₃ molecules isolated in a cryogenic rare-gas matrix. The spectrum of ScC₈₂ has features similar to those found earlier for LaC₈₂ and YC₈₂, suggesting that it can also be described as a +3 metal cation within a -3 fullerene radical anion. An implication of this work is that production of macroscopic quantities of clustercontaining fullerenes may make possible the fabrication of exotic new structures with regular arrays of metal-atom clusters isolated in fullerene molecules, resulting in a new type of host/guest nanostructured material.