Molecular dynamics, phase diagrams and electronic properties of fullerenes and alkali fullerides: insights from solid-state nuclear magnetic resonance spectroscopy

Solid-state nuclear magnetic resonance (NMR) measurements have made important contributions to the current understanding of the structural, dynamical, and electronic properties of fullerenes (C₆₀ and C₇₀) and the alkali fullerides A_xC₆₀ (A = alkali metal). These measurements and their interpretation are reviewed. One- and two-dimensional ¹³C NMR lineshapes and spin-lattice relaxation rates provide evidence for rapid molecular rotations and orientational order-disorder transitions in the fullerenes and alkali fullerides. The kinetics of molecular reorientations are determined from the NMR data. ¹³C and alkali metal NMR spectra indicate that the alkali fullerides are stoichiometric compounds. Each stable, stoichiometric phase has distinctive NMR signatures. ¹³C and alkali metal NMR spectra and relaxation measurements provide valuable and unique information about the electronic properties of the metallic, superconducting, and non-metallic phases of the alkali fullerides.