Study of the reorientational motion of C[sub 60]H[sub 2] in toluene-d[sub 8] by proton NMR

The proton spin-lattice relaxation time (T[sub 1]) of C[sub 60]H[sub 2] in toluene-d[sub 8] was measured between 281 and 338 K. Correlation times calculated from these T[sub 1] measurements are compared with those calculated from viscosity-temperature data via the Stokes-Einstein-Debye and Gierer-Wirtz microviscosity equations and with values reported for C[sub 60] by C-13 NMR. At room temperature, C[sub 60]H[sub 2] in toluene rotates at about the same rate as solid-state C[sub 60]. The Stokes-Einstein-Debye theory predicts reorientational correlation times (r[sub c]) that are a factor of 6-8 higher than observed, while the Gierer-Wirtz modification gives r[sub c] values that are 1.3-1.7 times those observed. In addition, a re-evaluation of previously published results shows that the C-13 spin-lattice relaxation of C[sub 60] in toluene-d[sub 8] has significant contributions from both the chemical shift anisotropy and spin-rotation mechanisms. 21 refs., 2 figs., 1 tab.