OXYGENATED SPECIES IN THE PRODUCTS OF FLUORINATION OF [60]-FULLERENE AND [70]-FULLERENE BY FLUORINE-GAS

Fluorination of pure [60]fullerene and [70]fullerene by fluorine gas s hows batch variation, and is accompanied by colour changes as fluorine slowly penetrates the fullerene lattice. Attempted partial fluorinati on produces a mixture of highly and unfluorinated material due to this slow penetration. [60]Fullerene undergoes fluorination more slowly th an [70]fullerene, due to better packing of the crystal lattice in the former, and this explains why [60]fullerene contaminated with [70]full erene is fluorinated faster than pure [60]fullerene. The NMR spectrum of fluorinated [70]fullerene shows a number of singlets between delta -151.2 and -153.65, indicating the formation of a mixture of derivativ es each possessing high symmetry. The IR of fluorinated [70]fullerene shows a broad band at 1112 cm(-1). The mass spectra of fluorinated [60 ]- and [70]-fullerenes reveals species containing up to eleven and six teen oxygen atoms, respectively (DCI probe, deposition from dichlorome thane), or up to eighteen oxygen atoms in each case (deposition;from m ethanol): The maximum site occupancies of species detected (assuming t hat oxygen is present as the epoxide) are 68 and 70, respectively. Met hylene- and(after reaction with methanol) trifluoromethyl-containing s pecies are also evident in the mass spectrum of fluorinated [60]fuller ene; corresponding species are not found in fluorinated [70]fullerene. The high level of epoxide formation with the fluorofullerenes indicat es that the tendency for fullerenes generally to form epoxides derives from the strong electron withdrawal by the cages.