Synthesis and properties of ionic hydrocarbons containing an alkylated fullerene anion

Synthesis of ionic hydrocarbons by the combination of the tert-butyl-C-60 anion (t-BuC60-) and a tropylium or cyclopropenylium ion is described. The reactions of t-BuC60- and carbocations (R+) with pK(R+) values ranging from 3.88 to 10.0 resulted in regioselective carbon-carbon bond formation to form 1,4-adducts, t-BuC60-R. These covalent hydrocarbons underwent reversible heterolysis into t-BuC60- and R+ in polar solvents. Thermodynamic studies indicated that the heterolysis is promoted by the specific solvation of the produced ions. In contrast, t-BuC60- and tris(guaiazulenyl)cyclopropenylium ion gave a hydrocarbon salt. The ionic nature of this material was demonstrated by the vis/NIR and IR absorption spectra in the solid state. Electrical conductivity measurements indicated that this salt behaves as a strong electrolyte in DMSO. Single-electron reduction of C-60 with the crystal violet radical also gave a carbocation-carbanion salt, composed of the crystal violet cation and C-60(is approximately equal to).