Endofullerenes : Nanolaboratories for single molecules

Orateur : Malcolm Harris LEVITT (Department of Chemistry, University of Southampton, UK)

Molecular endofullerenes are stable chemical substances composed of closed carbon cages, with single molecules encapsulated in the cages. These materials are produced in macroscopic quantities, high uniformity and purity by multistep organic synthesis. In Southampton we have produced the endofullerenes H2@C60, HD@C60, D2@C60, H2O@C60, H2(17O)@C60 and HF@C60. The single molecules rotate and translate freely inside the cage, even at cryogenic temperatures. A rich structure of quantum energy levels is observed, due to the translation modes of the molecule inside the cavity, coupled to the molecular vibration and rotation. These levels have been probed by inelastic neutron scattering, infrared spectroscopy, and NMR spectroscopy. Of particular interest is the existence of nuclear spin isomers, whose interconversion may be tracked by neutron scattering and electromagnetic spectroscopies, as well as by dielectric constant measurements.Transitions between nuclear spin isomers are forbidden in electromagnetic spectroscopies, but allowed in neutron scattering. I will review the science of molecular endofullerenes and the particular role of neutron scattering in understanding the quantum mechanics of these systems.

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