Parent Fullerene Research Articles

Electron Affinity of Some Endohedral Lanthanide Fullerenes

We report the first electron affinity measurements for some endohedral gadolinium metallofullerenes. Knudsen cell mass spectrometry has been used for the study of the gas-phase composition over the KF−Gd@Cn system. Both neutral and negatively charged species C60, C70+2n (n = 0, 1, ..., 10), Gd@C74, Gd@C76, Gd@C78, Gd@C80, and Gd@C82 were detected at 931−960 K, which permitted determination of equilibrium constants of electron exchange reactions. The electron affinities of gadolinium metallofullerenes were found to be greater than those of the parent fullerenes. In contrast to the empty fullerenes, endohedral metallofullerenes revealed no strong dependence of their electron-accepting ability on the size of the fullerene cage.

Novel Copolyamides Containing [60]Fullerene in the Main Chain

Abstract Novel copolymers, poly(1,4-oxybisphenylene fullerenobisacetamide-co-1,4-oxybisphenylene isophthalamide)s, which contained [60]fullerene in the main chain, were synthesized by the direct copolycondensation of a mixture of [60]fullerenobisacetic acid and isophthalic acid with 4,4′-diaminodiphenyl ether in the presence of triphenylphosphite and pyridine. Light scattering measurements for the copolymers showed a weight-average molecular weight Mw of about 5-6 × 104. The UV-visible spectra of the copolymers exhibited the characteristics of the parent fullerene derivative. The absorption edge red-shifted from 370 nm for poly(1,4-oxybisphenylene isophthalamide) to about 700 nm for the copolymers.

Enhanced coalescence reactions of fullerenes by laser desorption of C 60 derivatives

We observed enhanced coalescence reactions of fullerenes by laser desorption of chemical adducts of (C 6H 5CH 2) n C 60, (C 9H 7) m H n C 60, (CCl 2) x C 60 and the newly available poly- N-vinylcarbazole (PVK)-C 60/70. The mass spectra of the laser-produced species reveal a characteristic bi-modal profile, with one maximum abundance distribution of parent fullerene ions located at C 60 and the other at nearly twice C 60. The mass spectra of both pristine C 60 and the non-reactive PS/C 60 mixture show monotonically descending intensity of daughter fullerenes with successive C 2 captures, whereas slightly enhanced coalescence products are observed for the reactive PVK/C 60/70 mixture which is known as a charge transfer complex. The mechanism of efficient coalescence is believed to be cluster collisional nucleation of pairs of reactive fullerene fragments (nascent C 60, C 58, etc.) induced by photofragmentation of the reactive R n -C 60 adduct or R n ⋯C 60 charge transfer system, which is indicated by the laser power dependence features and the correlation between enhanced fullerene fragments and coalescence products.

Hydrogenation of [76]-, [78]- and [84]-fullerenes: cage degradation

The title fullerenes have been reduced under conditions (Zn, conc. HCl, toluene solution, 1h, N2, dark, room temp.) that give C60H36 from [60]fullerene and C70H36–40 from [70]fullerene. Reduction of [76]fullerene gives C76H46–50, [78]fullerene gives a broader spectrum of reduction products (consistent with the diverse isomeric composition of the parent fullerene), the most abundant species being C78H36 and C78H48(main component), and [84]fullerene yields mainly C84H48–52. In each case, reduction of the higher fullerenes is accompanied by cage breakdown to C60H36 and C70H36–40 the relative proportions of which vary with the starting fullerene. Thus reduction of [76]fullerene gave only a trace of C70H30–40, whereas [78]fullerene gave considerably more. Reduction of [84]fullerene over an extended period (5h) resulted in complete degradation to C60H36. HPLC separation of the hydrogenated fullerenes on a Cosmosil column (toluene eluent), showed them to elute more rapidly the larger the cage, as found previously for C60H36 and C70H36–40. By contrast, on the same column and under the same conditions, the parent fullerenes elute more slowly the higher the molecular weight.

Free-Radical Copolymerization of Fullerenes with Styrene

Various methods to chemically modify the fullerenes have been reported in the last few years since the production of large-scale amounts of fullerene soot that contains primarily C{sub 60}, a lesser amount of C{sub 70}, and traces of higher fullerenes. Fortunately, these components can be separated from each other by standard chromatographic methods, permitting convenient experimentation on relatively pure components. The authors have found that C{sub 60} and C{sub 70} copolymerize with styrene in a standard free-radical polymerization, either in the bulk or codissolved in an aromatic solvent. The resulting polymers are soluble in common solvents that dissolve polystyrene and possess a dark brown color. The absorption spectrum of the copolymer is strongly modified from that of the parent fullerene, and the fluorescence is blue-shifted and much stronger. The present paper describes a very simple method for direct incorporation of C{sub 60} or C{sub 70} into polystyrene by direct free-radical copolymerization under routine conditions. While a great deal remains to be done to characterize fullerenes as comonomers in free-radical polymerization, this method is so direct and simple that it may be of interest to a wide range of researchers working in the area of fullerene chemistry. The authors note amore » report by Gong et al. in which a polymerization of styrene and {alpha}-methylstyrene was carried out in the presence of C{sub 60} using benzoyl peroxide as an initiator. These authors explicitly state that the C{sub 60} retains its normal absorption spectrum and is dispersed within the resulting solid polymer matrix. No other characterization is presented to demonstrate if chemical attachment of the C{sub 60} to the polymer occurred.« less

Structures, Stabilities and Strain in C60and C70Derivatives

ABSTRACT The stabilities of a number of small adducts as well as larger hydrides of C60 and C70 are reported using semiempirical MO methods. The data are shown to be consistent with the nature of bond alternation in the parent fullerenes and strain effects in the cage systems.

Polyhydrogenation of [60]- and [70]-fullerenes

Reduction with Zn–conc. HCl in either benzene or toluene solution, results in rapid and quantitative conversion of [60]- and [70]-fullerenes into mainly C60H36 and C70H36/38. Significant amounts of more highly hydrogenated derivatives are also formed. Mass spectra under EI conditions can be obtained free of peaks due to either less-hydrogenated species or the parent fullerenes, provided they are obtained immediately, since both compounds undergo rapid light-catalysed degradation in the presence of oxygen, to give the parent fullerenes, oxygen-containing derivatives (fullerenols) and lower hydrides; C60H18 is the main product from C60H36. Formation of reduced fullerenes up to C60D44 and C70D48 on reaction of [60]- and [70]-fullerenes with Zn–conc. DCI, is attributed to the higher stability of C–D compared with C–H bonds, which provides greater compensation for the loss of resonance energy and the greater steric compression that accompanies reduction beyond the 36 H level. Laser-desorption time-of-flight mass spectrometry indicates that the absence of the corresponding higher hydrides (as opposed to deuterides) is not due to decomposition during EI mass spectrometry. The hydrides do not undergo hydrogen exchange with D2O either alone or in the presence of either sodium hydrogen carbonate or sodium hydroxide. C60H36 has considerable thermal stability but that for C70H36/38 is lower. HPLC chromatograms, as well as IR, UV–VIS, 1H NMR, and mass spectra have been obtained for both compounds. Each appears to be highly resistant to further reduction by hydrogen–catalyst, but shows a surprising tendency to form trimethylene adducts, by an unknown mechanism.

Reaction of p-nitro Benzyl With C 6 0

Since the achievement of the preparative-scale isolation of buckminsterfullerene,efforts to prepare derivatives of C_(60) have led to the synthesis and X-ray characterization of osmylated and platinum complexes.And subsequently, synthesis and X-ray characterization of several other derivatives, such as buckminsterfullerene undergoing Diels-Alder reactions with anthracene, furan, and cyclopentadiene,have also been reported.Smith described the generation and structure elucidation of 1,2-methanobuckminsterfullerene,the parent fullerene cyclopropane,and treated C_(60) in toluene

Production of Perfluoroalkylated Nanospheres from Buckminsterfullerene

Perfluoroalkylated nanospheres have been prepared by reaction of fullerenes with a variety of fluoroalkyl radicals. The latter are generated by thermal or photochemical decomposition of fluoroalkyl iodides or fluorodiacyl peroxides. Up to 16 radicals add to C(60) to afford easily isolable fluoroalkylated derivatives. The monosubstituted radical adducts were detected by electron spin resonance in the early stages of the fluoroalkylation reactions. These spheroidal molecules are thermally quite stable, soluble in fluoroorganic solvents, chemically resistant to corrosive aqueous solutions, and more volatile than the parent fullerenes. Films of the sublimed material display properties typical for a perfluoroalkylated material.

Electrochemistry of the C60H2 fullerene

In this paper we report the electrochemical behavior of the simplest hydrocarbon derivative, C[sub 60]H[sub 2]. Samples of C[sub 60]H[sub 2] were prepared by zinc/acid reduction and purified by gel permeation chromatography in toluene. The identity of each sample was confirmed by negative ion FABS mass spectrometry, and the purity was determined to be 90% by C[sub 18] reversed-phase HPLC. In many respects, the electrochemical behavior of C[sub 60]H[sub 2] is very similar to that of the parent fullerene, with C[sub 60]H[sub 2] being only slightly more difficult to reduce than C[sub 60] itself. For example, in benzonitrile 0.1 M tetrabutylammonium hexafluorophosphate, three reversible reductions are observed (at sweep rates 1000 mV/s), and the half-wave potential for each of these processes is 120-170 mV more negative than that for the corresponding C[sub 60] reduction. Similar results were obtained in CH[sub 2]Cl[sub 2] and in toluene CH[sub 3]CN (80/20). An additional fourth reversible reduction, at -2.36 V vs Fc[sup +]Fc, was noted in the case of toluene CH[sub 3]CN; this couple is tentatively assigned to C[sub 60]H[sub 2][sup 3[minus] 4[minus]]. 18 refs., 3 figs., 1 tab.

1,2-Methanobuckminsterfullerene (C61H2), the parent fullerene cyclopropane: synthesis and structure

Recently we reported the synthesis, isolation, and characterization of 1, the first fullerene epoxide (C[sub 60]O). We describe herein the generation and structure elucidation of 1,2-methanobuckminsterfullerene (2, C[sub 61]H[sub 2]), the parent fullerene cyclo propane. This is the methano analog of buckminsterfullerene epoxide 1. NMR coupling constants were employed to differentiate closed (fullerene) and open (fulleroid) isomers. We are currently exploring the chemical and physical properties of the [6,6] fullerene cyclopropanes. 15 refs., 1 fig.

The pattern of additions to fullerenes

Conjugation in C 60 is not as extensive as was originally anticipated because, for various reasons, the pentagon rings avoid containing double bonds. As a consequence, there is extensive bond localization and the molecule, which is quite reactive, and displays superalkene rather than superaromatic properties. C 70 behaves in a similar fashion; other fullerenes may follow suit. Additions predominate and C 60 is particularly susceptible to nucleophilic attack. Added groups may also be readily replaced by nucleophiles, although the reaction mechanism is uncertain at present: The functionalized molecule tends to revert to the parent fullerene at moderate temperatures, and characterization of reaction products by mass spectrometry is thus particularly difficult. This fact, coupled with the complexity of the addition products, makes work with fullerenes exacting. A selection of reactions studied to date and the progress made towards identifying various patterns of addition are described.