PERFLUOROFULLERENES - CHARACTERIZATION AND STRUCTURAL ASPECTS

Characterization of highly fluorinated fullerenes (perfluorofullerenes ) has revealed a wide range of x values. High reaction temperatures ar e limited by volatilization of the compounds. A good compromise is obt ained for a reaction at 300 degrees C for several hours leading to a w hite C60F54 compound with a narrow range of x values (+/-2). X-ray pow der diffraction reveals a f.c.c. lattice. Sublimation of C60Fx compoun ds is carried out under static vacuum and separate fractions are conde nsed successively. As sublimation temperature is increased, fractions move from the liquid state to solids. F-19 NMR spectroscopy reveals a single narrow peak for liquid fractions, with a chemical shift of -72 ppm/ CF3COOH thus suggesting a highly symmetrical species. The presenc e of oxygen is also detected when the starting material is exposed to air. The first fraction of air exposed compounds gives rise to a NMR s ignal at -55ppm. A relatively large quantity of liquid phase is obtain ed by direct condensation during C-60 fluorination. The NMR spectra is similar to that of the first sublimation fraction, exhibiting a peak at -72 ppm.