While its electrochemical oxidation is difficult, Cgg is readily oxidized in protic superacidic media. In order to exploit the reactive nature of the radical cations thus formed for the purpose of generating novel fullerene derivatives, a method involving nucleophilic trapping of oxidized Cgg has been developed. Thus, trapping oxidized Cgg with alcohols and aromatics results in the formation of alkoxylated and arylated C60, respectively, while trapping oxidized CgQ with x, y-diols results in the formation of x, y-difulleroxyalkanes (earmuff ethers).

We have explored several cycloaddition reactions as a general approach for preparing fullerene derivatives. In view of their electron-deficient nature, they are expected to participate as dienophiles rather than dienes in cycloadditions. This behavior is exemplified in their reactions with sulfur trioxide, diphenylisobenzofuran, and the nitrone from cyclohexanone and N-methyl-hydroxylamine. Fullerenes also formed adducts with maleic anhydride, although in this case the nature of the adduct is not clear. While changes in physical properties such as solubility or IR spectra clearly indicated formation of adducts, mass spectral analysis of diese and many other fullerene derivatives often showed ions due to fullerenes; thus confirmatory evidence for the derivatives was not available from mass spectrometry.

CrII(OEP) (OEP: Dianion of octaethylporphyrin) quantitatively reacts with C60 in a THF-toluene (THF: tetrahydrofurane) mixture to give purple-black crystals of formula Cr(OEP)(C60)(THF)x. ESR and SQUID measurements show this compound to be a salt better described as [Cr(OEP)(THF)2 +][(C60)−].THF(x-2). ESR spectra in frozen 2-Me-THF show an anisotropie signal centered at g = 1.998.

The surprisingly high Tc for the superconductivity of alkali doped C60 has spurred wide interest in understanding its mechanism [1–7]. We first report the superconductive properties of CsxRbyC60 which has a Tc as high as 33 K when x=2 and y=1 in the feed [4, 5]. SQUID measurements show that in this material the coherence length is 45 A and the penetration depth about 1, 800 A [5]. It has now been proven that the observed increase in the Tc with the size of the alkali dopant is due to the increase in the lattice constant [6]. This is most likely due to the changes in the density of states at the Fermi level. The other important parameter according to BSC theory is the phonon which mediates the electron-electron coupling. In the second part of this paper we present recent results which show that the Tc is indeed strongly influenced by this parameter [7]. The isotope effect is unexpectedly strong on the Tc.

We present results of magnetization and pressure measurements on recently discovered superconductors K3C60 and Rb3C60. as well as ferromagnetic C60TDAE, and discuss the nature of the ground state suggested by these studies.

The C60/C70 thin film crystals have been fabricated on the (001) surface of alkali halide substrates, KC1, KBr, and NaCl, and their structures have been studied. The crystal structure analyses by TEM show that the hexagonal closed packing (hep) with lattice parameters of a=10.0 Å and c=16.3 Å and the face-centered cubic (fee) with a=14.2 Å coexist in the C60 thin film crystals. The C70 thin film crystals show an expanded lattice constant of a=10.5 Å from the view perpendicular to the stacking plane. The ratio of hep to fee is dependent on the kind of the substrates and on the substrate temperatures during the crystal growth. The observed reversible change in the Raman spectrum of the C60 thin films implies a rotational molecular motion in the thin film crystals.

Alternative isomerie structures of C60 spheroids have been investigated using semiempirical and ab initio quantum chemical techniques. Unlike the icosahedral ground state, these isomers are characterized by the presence of pentagonal rings adjacent to each other. The lowest energy alternative isomer of C60 has two such pairs of edge-sharing pentagons and lies = 2 eV higher in energy than the ground state. Isomers containing three and four pairs of adjacent pentagons have also been studied in detail. Overall, the energy contributions of these adjacent pentagonal defects are additive, with each defect making the structure less stable by = 1 eV.

The electronic structures of some possible carbon fibers nucleated from the hemisphere of a bucky ball are presented. A one-dimensional electronic energy band structure model of such carbon fibers, having not only a principal rotational axis but also fibers with screw axes, can be derived by folding the two-dimensional energy bands of graphite. By considering the variation of the fiber diameter and helicity within a simple tight binding model calculation, we show that 1/3 of the fibers are metallic and 2/3 are semiconducting. The effect of adding multiple tubule layers is considered.

Recent reports suggest that graphitic tubules with diameters on the order of fullerene diameters have been synthesized. Such small-diameter tubules should have electronic properties related to those of two-dimensional graphite. We demonstrate by comparison with results from a first-principles, self-consistent, all-electron Gaussian-orbital based local-density functional approach that an all-valence tight-binding model can be expected to give a reasonable description of the electronic states of these tubules. In analyzing both high-symmetry tubules and lower-symmetry chiral tubules, we see that a relatively high carrier density could be expected for many of these structures.

The results of ESR studies on several anion radicals of the fullerene C60, C60 n-(n = 1, 2, and 3), in the solvents benzonitrile, dichloromethane, pyridine and tetrahydrofuran containing 0.1 M TBAClO4 are reported and discussed. The samples are prepared by electrochemical reduction techniques which allow the preparation of samples which contain, quantitatively, the desired anionie species. The results of ESR spectral studies on the anions in frozen solutions as a function of temperature are presented. The ESR lineshapes and linewidths are dependent upon the solvent and the temperature. The g-values are weakly dependent upon temperature. The results obtained from this study are presented and discussed in terms of the unique physical structure and properties of C60.

We have calculated the electronic structure of icosahedrai C60H60 and tetrahedral C60H60 via an all-electron Gaussian-orbital based local-density functional approach. The one-electron wavefunctions and eigenvalues have been used in a first-order time-dependent perturbation theoretic calculation of the spherically averaged X-ray and ultraviolet pho-toemission cross-sections for these molecules.

The preparation and purification of macroscopic quantities of buckminsterfullerenes [1] or buckyballs has ignited an explosion of research into their physical and chemical properties, and a variety of strategies for preparing new fullerene-based materials. Free radical synthesis is an appealing approach for forming polymeric fullerene materials. We report a polymeric fullerene material prepared by reacting pure C60 with xylylene from the thermolysis of paracyclophane. Addition of xylylene to a purple solution of C60 in toluene solution at -78 °C resulted in an olive-green solution from which an insoluble brown powder precipitated upon warming to room temperature. Analyses of the powder by solid state 13C MAS NMR, IR, and thermal gravimetric analysis are consistent with C60-xylylene copolymer.

Results on the nonlinear properties of solutions of Buckminsterfullerene in toluene are reported. Optical limiting thresholds are as low as 15 mJ/cm2 with multiple pulse stability. Evidence for a different mechanism than that applicable in graphitic carbon black suspensions is presented. The calculated second hyperpolarizability agrees with experimentally reported values.

We report the optical properties of C60 determined from the variable angle ellipsometry and near normal incidence reflection / transmission (R.T) experiments, and of M6C60 from the R, T experiments. The measurements were performed on thin films (d∼1000 Å) of C60 and M6C60 deposited on both Si(100) and suprasil substrates. The onset for strong absorption across the HOMO-LUMO gap in CgQ is measured to be -2.3 eV, slightly larger than the gap values obtained from the x-ray photoelectron spectroscopy (XPS) and electron-energy-loss spectroscopy (EELS) experiments. The observed peak positions in ε2(ω) for M6C60 and C60 compares well with the recent band structure calculations and suggests that the M6C60 compounds exhibit only a weak hybridization between the C60 and M states.

The Raman-active modes of solid films of MxC60 (x-0, 6; M=K, Rb, Cs) and K3C60 have been studied experimentally. The mode-activity is dominated by intraball interactions, and the effect of the M + ions on the C60 spectrum is observed to be almost insensitive to the radius or mass of the alkali metal. Tangential modes of solid C60 are observed to soften in M660 by -60 cm−1, which can be attributed to a charge-transfer-induced elongation of the intraball bond lengths, similar to that observed in graphite intercalation compounds. Conversely, the radial modes are found to upshift slightly, indicating that a competing mechanism counteracts the effect of the bond elongation. For K3C60, six Raman lines have been observed in which the lowest frequency mode exhibits a Breit-Wigner-Fano lineshape, indicating a coupling between the lowest frequency Hq-derived intramolecular modes of C60 and a broad Raman-active continuum with the same symmetry lying lower in frequency.

Buckmisterfullerene, C60, has attracted great interest because of its carbon-cage structure and potential applications in the field of superconductivity when doped with alkali metals. The icosahedral framework of C60 has been confirmed by X-ray analysis of an osmylated C60, called ‘Bunnyball’. Little theoretical work has been done to understand the electronic mechanism of C60 and substituted C60. This work has focused on electronic properties of C60 and the bunnyball with hypothetical analogs metal substitutions to understand the electronic effects of adducts on the bunnyball. In this analysis, the osmylated C60and hypothetical analogs were studied by extended Hückel methods. Molecular orbital(MO) interaction diagrams constructed from Density of States (DOS) analysis of the bunnyballs are presented. The results suggest electronic effects induced by substitution /adduct strongly affect electronic population in the C60 unit.

Recently it has been shown that buckminsterfullerene can be made to crystallize in a fee lattice when doped with various alkali metals eg. K, Rb, etc. Preliminary studies have shown the high propensity of C60 to be reduced without loss of stability. This may lead to interesting conductive pathways if a suitable dopant can be found which would act as an electronic “bridge” between adjacent “buckyballs” Out theoretical analyses have been geared towards a greater understanding of the reductive tendencies of C60, to discover how hypothetical metal-ion/C60, complexes differ from their corresponding simple, well characterized organometallic analogs. We demonstrate that the “metallocenium” link perturbs the electronic states of the C6 moiety including the frontier molecular Orbitals. Consequently, the metal ion plays an important role in establishing the electronic characteristics of metal-ion linked C60, chains and can be used to achieve desired properties.

Time-resolved degenerate four-wave mixing experiments were conducted on films of pure Qo using a 35 ps Nd:YAG laser. The measurements wavelength 1.064 μm was far off resonance with any one-photon absorption bands. A small linear absorption coefficient α=6 cm−1 was measured at this wavelength. The third-order optical susceptibility χxxxx (3) of C60, derived from its phase conjugate signal, is 7 × 10−12 esu. The nonlinear optical temporal response was largely laser-pulse limited. Evidence for a fifth-order contribution to the nonlinear optical response was observed at high laser intensities.

The in situ measurement of lateral photoconductivity has been carried out on vacuum vapor deposited C60 and phthalocyanine thin films. From the photo-current increase curve during the deposition and the SEM observation of copper phthalocyanine (CuPc) thin films, it has been revealed that, at an early stage of deposition, they consist of small clusters scattered on substrate. As the thickness Increases, the clusters coalesce to eventually form continuous film. We also show that C60 thin film has considerable photoconductivity. The photo-current spectrum agrees well with the absorption one with the exception that a peak at 600 nm appears only in the former. This wavelength region corresponds to a theoretically predicted forbidden transition. An onset of photocurrent at 760 nm is assigned to the absorption edge of solid C60. The photoconductivity of C60 thin films shows a rather unusual temperature dependence In that a small drop of temperature (e.g. from 25° C to 15° C) causes a dramatic increase In photocurrent by more than two orders of magnitude.

Pseudo-two dimensional branched polycarbenes 1, 3, 5-[H(m-C6H4C:)n/3]3C6H3 (2)(n = 6, 9) were prepared. The measurement of their magnetization on a Faraday balance equipped with a light guide has revealed that 2(n = 6) has a tridecet ground state (S = 6.0). The m-phenylene skeleton as a dependable ferromagnetic coupling unit has also been applied with success to the synthesis of persistent systems, i.e., 5, by replacing each carbene center in linear polycarbenes 1 with a nitroxide. A necessary degree of steric protection of the radical centers was disclosed. Extension to real polymers 4 gave an only partly successful result.