Metal dimer and trimer within spherical carbon cage

C80 fulleren cage can be used to realize confinement with the highest possible icosahedral (Ih) symmetry. As examples, La2@C80 and Sc3C2@C80 are molecules in which metal dimer and trimer are encapsulated within the C80 cage. They are recently purified in the substantial amount by using a high performance liquid chromatograph (HPLC), and studied by spectroscopy and X-ray diffraction. The confinement of the metal cluster with the high symmetry (Ih) cage is reflected in their specific potential of the intra-molecular rotation for the cluster. The result of electron spin resonance (ESR) measurements indicates that the intra-molecular potential is modified by the chemical modification of the C80 cage as well as by the injection of an excess electron.