STUDY OF THE REORIENTATIONAL MOTION OF C60H2 IN TOLUENE-D(8) BY PROTON NMR

The proton spin-lattice relaxation time (T-1) of C60H2 in toluene-d(8) was measured between 281 and 338 K. Correlation times calculated from these T-1 measurements an compared with those calculated from viscosi ty-temperature data via the Stokes-Einstein-Debye and Gierer-Wirtz mic roviscosity equations and with values reported for C-60 by C-13 NMR. A t room temperature, C60H2 in toluene rotates at about the same rate as solid-state C-60. The Stokes-Einstein-Debye theory predicts reorienta tional correlation times (tau(c)) that are a factor of 6-8 higher than observed, while the Gierer-Wirtz modification gives tau(c) values tha t are 1.3-1.7 times those observed. in addition, a re-evaluation of pr eviously published results shows that the C-13 spin-lattice relaxation of C-60 in toluene-d(8) has significant contributions from bath the c hemical shift anisotropy and spin-rotation mechanisms.