ABSTRACT
From the point of view of a chemist, carbon is surely the most intriguing element among the elements that have been discovered to date. As the core element of thousands of organic compounds, carbon is associated closely with the origin of life.1 The discovery of fullerenes, a collection of spherical molecules consisting of pure carbon atoms, has not only added a new form of elemental carbon but also opened an avenue for research into molecular architecture.2 Soon after the proposal of the soccer-ball-like molecular structure of C60, the most abundant fullerene isomer, the pioneering work by Smalley and coworkers predicted the possibility of fullerenes for encapsulating metal atoms (or other molecules) inside hollow-cage cavities based on the observation of the molecular ion peak of LaC60 in mass spectrum.3 This new class of metal-carbon hybrid molecules is referred to as endohedral metallofullerenes (EMFs).4 In a later report on the solvent extraction of La-containing EMFs, the authors suggested that the symbol @ can be used to indicate the endohedral
1.1 Classification of EMFs......................................................................................3 1.1.1 Mono-EMFs ..........................................................................................3 1.1.2 Di-EMFs ...............................................................................................4 1.1.3 Tri-EMFs ..............................................................................................5 1.1.4 Cluster EMFs ........................................................................................5
