Solid-state NMR experiments have been performed to determine the nature of
the molecular motion of C-60 in cocrystals of C-60/p-bromocalixarene pro
pyl ether. Throughout the temperature range of this work (room temperature
to 130 K), C-60 undergoes fast isotropic reorientation. The C-60 molecular
dynamics in the cocrystal are similar to that found in the fee crystal stru
cture of pure C-60 The activation energy of C-60 reorientation in the cocry
stal is 5.6 +/- 0.2 kJ/mol, and the rotational diffusion constant of C-60 i
s 11 x 10(9) s(-1) at room temperature.