Nonmetallic Endofullerenes and the Endohedral Environment: Structure, Dynamics, and Spin Chemistry

Abstract

Over the past two decades, nonmetallic endohedral fullerenes containing most of the noble gases and several small molecules have been prepared from C60 and a few other closed- and open-cage fullerenes and isolated in sufficient quantities and purity to be characterized by a variety of spectroscopic and other physical methods. Of particular interest has been determining the effects of encapsulation on the properties both of the cage and of the trapped atom or molecule. Nuclear magnetic resonance, which is independent of the optical properties of the fullerene or the medium, and often insensitive to impurities, has revealed many details of the structure and dynamics of the intracage environment. Low-temperature infrared spectroscopy at both long and short wavelengths, inelastic neutron scattering (INS), and low-temperature solid-state NMR have been used to study the coupled translation–rotation of H2 and H2O molecules trapped in C60. Special attention has been paid to detecting, enriching, and monitoring the stability of the para and ortho nuclear spin–rotational isomers of H2 and H2O in the endohedral environment with a view toward using the fullerene cage as a “bottle” for storing or releasing the isomers in condensed media under controlled conditions.