H and Li dynamics in Li12C60 and Li12C60Hy

Lithium and hydrogen dynamics in Li12C60 and Li12C60Hy are investigated by means of 7Li and 1H solid state Nuclear Magnetic Resonance (NMR) in the temperature range 80-550 K. Differential scanning calorimetry characterization on the hydrogen sorption and X-rays structural analysis are also reported. In the pure phase, the 7Li results show a thermally activated dynamics that can be associated to Li motions within the crystal interstices. Upon hydrogenation, Li ionic motion is considerably hindered by the presence of hydrofullerene molecules. The 1H measurements show that C-H bonds are stable on the local scale up to 400-450 K. The NMR results at higher temperatures are compatible with a H diffusion mechanism which anticipates the H desorption process.