Five cyclic adducts C60C4H6, C60C5H6, C60NHCO2, C60NCO2Et, and C60CHCO2Et have been synthesized and their absorption and fluorescence spectral properties investigated and compared with those of the parent. Breaking the structural symmetry of C60 apparently resulted in enhancing the quantum yield two to three-folds in some adducts and thus made fluorescence much easier to be measured at room temperature. New absorption bands and altered fluorescence spectra were observed in the adducts. The Stokes' shifts of the adducts were small, about 4-5 nrm, compared to 68 nm for the parent compound. All the adducts exhibited a single fluorescence lifetime about the same as C60 (ca. 1.3 ns). Aliphatic solvents had little influence on the absorption or fluorescence spectral profile except on the molar absorptivity whereas aromatic and polar solvents strongly interacted with the adducts causing a peak broadening effect.

We report neutron diffraction measurements of orientational ordering, and inelastic neutron scattering measurements of the inter- and intra-molecular excitations, for the 6:5 annulene isomer (C3 symmetry) of C61H2. We confirm previous x-ray measurements[1] which have shown that above 290K this isomer has an fcc structure, with the molecules orientationally disordered such that the methylene groups preferentially occupy “octahedral” sites. Below 290K, the diffraction pattern can be indexed on a simple cubic lattice, in direct analogy with the orientational ordering transition of C60. The observed low energy dynamics reflect this behavior. A peak corresponding to molecular librations is observed below the transition, at ∼2.5meV, while above the transition the peak collapses into a quasielastic line characteristic of rotational diffusion. The intramolecular spectra show several pronounced peaks. The assignments of these modes are discussed.

In recent characterization of fullerenes by small angle neutron scattering use was made of the Guinier scattering regime to determine the radius of gyration of the fullerene molecules. In the present work the HB-1A spectrometer at the High Flux Isotope Reactor at Oak Ridge National Laboratory was used to measure the scattering from C60 in CS2 solvent. The scattering covers a range which includes scattering intensity oscillations associated with the C60 shell structure. These oscillations are used to measure the C60 molecule size. Assumption of a carbon shell radius of 3.57Å fits the scattering minima. This radius and the assumption of a solvent cavity radius of 5.93 Å gives a good fit to the whole scattering range. However, modeling to remove a remaining scattering intensity discrepancy at low angles requires the addition of a small solvent density excess near the C60 molecule.

We have measured the thermal conductivity λ of highly pure polycrystalline C60 in the range 50 to 300 K under pressures up to 1 GPa. The results are discussed in terms of the lattice structure and dynamics. In particular, we discuss the phase diagram as delineated by anomalies observed in λ and cp at the f c.c.-to-s.c. transition at 260 K and the glass transition at Tg = 90 K, and also the effect on λ of the orientational motion in the s.c. phase. The results are found to be compatible with p-T phase diagram recently suggested by us.

We have measured the thermal conductivity λ and the compressibility of highly pure C70 in the range 90 to 450 K under pressures up to 1.2 GPa. Our results for the thermal conductivity indicate molecular rotation in C70 above 280 K at zero pressure. The phase boundary for the rotationally disordered phase has an approximate slope dT/dp = 75 K GPa−1. The bulk modulus B increases linearly with increasing p above 0.1 GPa, with an extrapolated zero pressure value at 296 K of B(0) = 8.3 GPa. Unexpected anomalies are found in both B and λ near 100 MPa, and we tentatively suggest that orientational ordering is responsible.

Molten naphthalene has considerable solubility for C60 (∼5 10−3 in mole fraction) making it a potential solvent for fullerenes; the phase diagram is therefore important. It was also of interest to study whether C60 displays the same anomalous solubility behavior in naphthalene as in hexane, CS2, and toluene, where the solubility increases with temperature up to a maximum near room temperature and decreases subsequently.

The naphthalene-C60 eutectic temperature was determined by DSC; the solubility of C60 in the liquid solution up to ∼180 °C was derived by UV spectrophotometry and found to decrease monotonically with increasing temperature from a mole fraction of 5 · 10−3 at the eutectic (∼79.5 °C) to 1.5 · 10−3 at 165 °C; thus, it shows a higher-temperature C60 solubility decrease (with increasing temperature) analogous to the other solutions, while a potential lowertemperature solubility increase (with increasing temperature) is masked by the eutectic. A binary phase diagram based on these data is proposed.

The diffusion of fullerenes in solution is studied taking into account the recently established fact of the formation of clusters containing some number of aggregated fullerene molecules. Based on a droplet model of a cluster, the distribution function of fullerene clusters by size is obtained for various concentrations of solution. It is shown that dissolved fullerene is present mainly in the form of clusters at saturation conditions, but the contribution of clusters decreases as concentration drops down. Since the diffusion mobility of clusters is much less than that of molecules, it leads to the dependence of an effective diffusion coefficient on concentration, which is computed for the case of fullerene C60. The feasibility of the use of this dependence as a basis for a diffusion method of the separation and enrichment of the fullerene extract with a small addition of higher fullerenes is analyzed. Possible schemes for enrichment are discussed.

A thermodynamic model describing the co-existence of phases at orientational phase transition in solid fullerenes is developed. It is shown that for such a transition in fullerene C60 characterized by the comparatively low enthalpy, heterophase fluctuations can lead to the wide temperature region of the phase co-existence within about 30 K below the 260 K transition point, and mainly determine the anomalies of thermodynamic characteristics observed within that region. By comparison of the theoretical dependence obtained on this basis with the experimental data on the x-ray diffraction and heat capacity measurements for C60, the energetical characteristics of the heterophase cluster formation are evaluated. The relative contribution of homophase and heterophase fluctuations to breaking the orientational order is discussed.