Electron-phonon interaction in C70

The matrix elements of the deformation potential of C$_{70}$ are calculated by means of a simple, yet accurate solution of the electron-phonon coupling problem in fullerenes, based on a parametrization of the ground state electronic density of the system in terms of $sp^{2+x}$ hybridized orbitals. The value of the calculated dimensionless total electron-phonon coupling constant is $\lambda\approx0.1$, an order of magnitude smaller than in C$_{60}$, consistent with the lack of a superconducting phase transition in C$_{70}$A$_3$ fullerite, and in overall agreement with measurements of the broadening of Raman peaks in C$_{70}$K$_4$. We also calculate the photoemission cross section of C$_{70}^-$, which is found to display less structure than that associated with C$_{60}^-$, in overall agreement with the experimental findings.Comment: To be published in Phys. Rev.

Isolation and characterisation of both the first fluoroxyfluorofullerene C60F17OF and oxahomofluorofullerenol C60F17O.OH

The first fluoroxyfluorofullerene C60F17OF (A) has been isolated from the fluorination of [60]fullerene with a mixture of MnF3 and K2NiF6 at 480ºC. This compound has a shorter HPLC retention time than the isomeric fluorofullerene ethers (oxahomofullerenes) and is less stable towards El mass spectrometry. It fragments by losing OF as a single entity and shows no formation of C60O as a fragment ion. By contrast, the ethers fragment by first losing a number of F atoms and then CO, and ultimately show also the presence of C60O, whilst epoxides lose CO as a main fragmentation step and do not give C60O. The first oxahomofluorofullerenol C60F17O.OH (B) has been isolated from the UV-irradiation of a toluene solution of C60F18 in air during 65 It and readily eliminates HF due to adjacent F and OH groups during El mass spectrometry. The structures of both the compounds have been deduced from I D and 2D 19F NMR spectroscopy. Just as oxygen inserts into FC-CF bonds of C60F18 to give ethers, so insertion into a C-F bond gives A. The oxahomofluorofullerenol B is produced by SN2' substitution of F by OH, followed by oxygen insertion into a 6:5-bond (αβ to the OH group) giving a motif not seen previously in fluorofullerenes

Novel addition in trifluoromethylation of 70 fullerene

Pyrolytic trifluoromethylation of [70]fullerene with CF3CO2Ag at 300 degreesC results in the addition of up to 12 CF3 groups to the fullerene cage. Forty-six C-70(CF3)(n) derivatives (numbers in parentheses) were separated by two-stage high pressure liquid chromatography (HPLC) as follows: n = 2(2), 4(16), 6(9), 8(14) 10(5), some being characterised by F-19 NMR. The range of derivatives is much greater than for other [70]fullerene reactions, and as with [60] fullerene trifluoromethylation, no single derivative is dominant, indicating that kinetic stability mainly controls product formation. F-19 NMR spectra show most derivatives to be unsymmetrical, with combinations of quartets and septets (overlapping quartets) due to contiguous ('linear') addend arrays, having significantly different coupling constants of the 'terminal' quartets of between 9.1 and 17.7 Hz. These differences, together with those observed previously in trifluoromethylation of [60]fullerene are consistent with addition across both 6:6- and 5:6-ring junctions. Of the two C-70(CF3)(2) isomers, one has either C-s or C-2 symmetry, the other has C-1 symmetry, whilst the C-70(CF3)(4) derivatives fall into four categories: (i) symmetrical compounds (one gives only two singlets in the F-19 NMR); (ii) unsymmetrical compounds that show a 'linear' coupling sequence; (iii) unsymmetrical compounds having a remote pairs of adjacent groups; (iv) compounds having a coupled array of three CF3 groups, together with a remote group suggesting sterically-driven migration. The first evaluation of differential NMR couplings across 6:6- and 5:6-bonds in a fullerene has been made using C60F6 as a model