STUDY OF THE ANOMALOUS SOLUBILITY BEHAVIOUR OF SOLUTIONS SATURATED WITH FULLERENES BY ~(13)C-NMR

摘要

~(13)C NMR of saturated solutions of C_(60) allows one to determine the solubility C_(60) and to characterize the various phases. If aromatic solvents are used, the effect of the chemical shift anisotropy of the solvent induces enough variations on the C_(60) chemical shift that the various phases are well resolved. This way the C_(60) in solution (143.04 ppm), C_(60) in a solid-solvate (143.59 ppm) and C_(60) in a solid but less sdlvated state (143.87 ppm) could be distinguished. The solubility curve as a function of temperature passes through a maximum. At low temperatures (up to ca. 341 K) the dissolved C_(60) is in equilibrium with the C_(60) solid-tetralin solvate. This solvate decomposes at the maximum temperature and could be transformed to pure C_(60) solid. However, the latter was not observed, because the equilibrium conditions have not been reached in our experiments. Note finally, that the solubility curve is not reproduced during decreasing temperature, suggesting once again that the equilibrium conditions have not be reached.