Anomalous Relaxation and Molecular Dynamics of Buckminsterfullerene in Carbon Disulfide

We have employed the Hubbard relation to acquire semiquantitative information on the¹³C spin−lattice relaxation rate of buckminsterfullerene in CS<INF>2</INF>. We found the spin rotation mechanism to be operative and its contribution to be significant at all temperatures studied here. With the exception of values at 303 K, we found very different chemical shift and spin rotation contributions in this solvent than in 1,2-dichlorobenzene-d<INF>4</INF>. In fact, the respective contributions were reversed at 313 K. This observation indicates that solvent effects play a critical role in determining how effective these mechanisms will be in a given solvent. Three hydrodynamic-based models were applied in an attempt at theoretically describing the rotational motion of the title molecule in CS<INF>2</INF>. The Stokes−Einstein−Debye (SED) model proved superior in duplicating our experimental findings. The agreement between the SED predictions and our experimental reorientational times suggests that C<INF>60</INF> reorients in the “stick” limit where solute−solvent velocities are predicted to be similar. We, however, believe that the velocity coherence is not due to their separate matched velocities but rather originates from the presence of intermolecular interactions.