Dodecylated Large Fullerenes: An Unusual Class of Solids

The large fullerenes that are formed during the synthesis of C 60 by the arc discharge technique can be solubilized by reductive alkylation. The mass range of dodecylated large fullerenes determined by laser desorption ionization, time-of-flight mass spectrometry was found to be 650−3500 amu. The solubility of the dodecylated large fullerenes in chloroform is 15.7 g/L as measured by near-infrared spectroscopy. High-resolution transmission electron microscopy images show the expected nontubular, ring-shaped contrast resembling large fullerenes attached to dodecyl groups. The dodecylated large fullerenes have distinctly different behavior than regular organic molecules in dipolar dephasing, magic angle spinning nuclear magnetic resonance ( 13 C MAS NMR) experiments. Thermal gravimetric analysis and 13 C MAS NMR experiments indicate that there is 1 dodecyl group for every 23 sp 2 fullerene carbon atoms, that the quaternary aliphatic carbons generated upon dodecylation give signals considerably more shielded than those in alkylated C 60 and C 70 but similar to the quaternary aliphatic signals in dodecylated single-walled carbon nanotubes, and that the dodecyl groups in the dodecylated large fullerenes exhibit widely varying degrees of motional freedom. The last characteristic was unexpected and apparently results from a combination of dodecyl groups in void spaces of varying size and dodecyl groups on molecules that tumble at various rates.