C ₆₀ Rotation in the Solid State: Dynamics of a Faceted Spherical Top

Abstract

The rotational dynamics of C(60) in the solid state have been investigated with carbon-13 nuclear magnetic resonance ((13)C NMR). The relaxation rate due to chemical shift anisotropy (1/9T1(CSA)(1)) was precisely measured from the magnetic field dependence of T(1), allowing the molecular reorientational correlation time, tau, to be determined. At 283 kelvin, tau = 9.1 picoseconds; with the assumption of diffusional reorientation this implies a rotational diffusion constant D = 1.8 x 10(10) per second. This reorientation time is only three times as long as the calculated tau for free rotation and is shorter than the value measured for C(60) in solution (15.5 picoseconds). Below 260 kelvin a second phase with a much longer reorientation time was observed, consistent with recent reports of an orientational phase transition in solid C(60). In both phases tau showed Arrhenius behavior, with apparent activation energies of 1.4 and 4.2 kilocalories per mole for the high-temperature (rotator) and low-temperature (ratchet) phases, respectively. The results parallel those found for adamantane.

Solid-state structures of peapod bearings composed of finite single-wall carbon nanotube and fullerene molecules

“…As demonstrated previously with naked C 60 , the solid-state NMR spectra provide the evidence for dynamic motion in the solid state. Due to the random orientations of the molecules fixed in the solid state against the external magnetic field, ordinary molecules affords a broad powder pattern of resonances under static NMR conditions without MAS (20), whereas C 60 affords a narrow single resonance even under the static NMR conditions by cancelling out the chemical shift anisotropy through the dynamic rolling motion in the solid state (21)(22)(23) Fig. S2), we observed a narrow single resonance of C 60 at 140 ppm along with the broad powder-pattern resonances of the encapsulating [4]CC host.…”

Nuclear Magnetic Resonance of Laser-Polarized Noble Gases in Molecules, Materials, and Organisms

“…l?dlerenes are attractive systems to study with such methods because their spin relaxation behavior is well-characterized [180,181,182,183], and the 13C longitudinal relaxation times can be relatively long at low temperatures (e.g., 13C771N 80s for CGCI [181]). However, because the average diameter of the crysta]lites was large (w4 pm for the CGOsample and W2 pm C70), the respective surface areas of these samples were estimated to be only W1 and -2 m2/g.…”

Fullerenes

“…Evidence for a second phase transition at 165 K is provided by ultrasonic attenuation studies, 62 specific heat measurements, 99 dielectric relaxation studies, 100 electron microscopy observations, 101 neutron scattering measurements, 35 dynamic NMR processes, 102 and Raman scattering studies. 97 In contrast to the structural phase transition near 255 K which is sensitively studied by static diffraction techniques, the phase transition occurring near 165 K is most sensitive to dynamic processes.…”