ISOLATION AND CHARACTERISATION OF C60(CF3)2

From the products of reactions of [60]fullerene with either K₂PtF₆ at 470 °C or AgF at 520 °C, we have isolated C₆₀(CF₃)₂, the simplest trifluoromethylfullerene, which gives a single ¹⁹F NMR line at -69.5 ppm. The HPLC retention time is less than that of C₆₀F₂ confirming the trend observed for other fluoro- vs. trifluoromethylfullerenes namely that the latter elute more rapidly. Other trifluoromethyl- containing species, C₆₀(CF₃)₄O, C₆₀F₅CF₃, C₆₀(CF₃)₄H₂, C₆₀(CF₃)₆H₂, and C₆₀(CF₃H)₃ were detected in the product mixture.     

Trifluoromethylation of [60]- and [70]Fullerene in the Ionization Chamber of a Mass Spectrometer

Both [60]- and [70]fullerene react with either the Scherer radical (perfluorodiisopropylethylmethyl, C₉F₁₉), a mixture of branched perfluorononenes (C₉F₁₈, the product of hexafluoropropene trimerization), or β-fluorosulphatotetrafluoroethyldiheptafluoroisopropylmethyl radical (C₉F₁₈OSO₂F) in the ionization chamber of a mass spectrometer to give the positive parent ions of trifluoromethylation products, the reaction being accompanied by hydrogen addition. The reaction occurs at least partly on the walls of the ionization chamber, by a radical mechanism employing CF₃ radicals formed from the radical reactants both thermally and under electron impact; only the latter route occurs with the perfluorononenes.     

Evidence for η6 Coordination to a Fullerene

Evidence for the first η⁶ derivative of a fullerene, [MoC₆₀F₁₈(CO)₃] has been obtained from reaction between [Mo(CH₃CN)₃(CO)₃] and C₆₀F₁₈.     

Arylation of [60]Fullerene with Br2/FeCl3/PhH: Formation of C58 Derivatives via CO Loss

Heating a mixture of [60]fullerene, bromine, ferric chloride and benzene under reflux for 24 h products a range of phenylated [60]fullerene derivatives. The main product is C₆₀Ph₅H but other components identified by mass spectrometry (and in some cases separated by HPLC) are: C_6oPh_n(n = 4, 6, 8, 10, 12), C₆₀Ph_nO₂(n = 4, 6, 8, 10, 12), C₆₀Ph_nOH (n = 7, 9, 11), C₆₀Ph_nH₂ (n = 4, 10), C₆₀Ph₄H₄, C₆₀Ph₅H₃, C₆₀Ph_n0₂H (n = 5, 9), C₆₀Ph₄C₆H₄O₂, C₆₀Ph₉OH₃, and C₆₀Ph₁₁ O₃H₂. In the corresponding reaction with toluene, the crude reaction mixture contained C₆₀(MeC₆H₄)₄ as a main product; C₆₀(ClC₆H₄)₅H was obtained from the reaction with chlorobenzene. Formation of these derivatives is believed to involve radical bromination of the fullerene, followed by electrophilic substitution of the hatogenofullerene into the aromatic, accompanied in some case by hydrolysis, elimination and epoxide formation; oxidation may also introduce ketone/dioxetane functionality. The EI mass spectra of C₆₀Ph₄O₂ and C₆₀Ph₈O₂show degradation to C₅₈Ph_n (n = 0-8), having structures believed to be related to the pseudofollerenes C₆₈Ph_n (n = 0-8) reported recently. These results suggest that some derivatisations of fullerenes confer stability, due to the relief of strain.     

Spectroscopic Evidence for Anionic Coordination Complexes of the Transition Metals with C70 and the Higher Fullerenes C76, C78, C82, C84, C86, C90, and C92

The carbonylate anions [M(CO)₅]^- (M = Mn, Re), [Co(CO)₄]^-, [CpFe(CO)₂]^-, and [CpM(CO)₃]^- (M = Mo, W) react with C₇₀ via single electron transfer processes to give, respectively, the corresponding 17-electron, metal-centered radicals Co(CO)₄, M(CO)₅ (M = Mn, Re), CpFe(CO)₂, and CpM(CO)₃ (M = Mo, W) in addition to the radical anion C₇₀^-. In secondary thermal or photochemical processes, the metal-centered radicals Co(CO)₄ and M(CO)₅ (M = Mn, Re) combine with the C₇₀^- to form the new η²-C₇₀ complexes [Co(CO)₃(η²-C₇₀)]^- and [M(CO)₄(η²-C₇₀)]^-. However, the metal-centered radicals CpM(CO)₃ (M = Mo, W) require photolysis to react with C₇₀^- to form [CpM(CO)₂(η²-C₇₀)]^-, whereas neither thermolysis nor photolysis induces reaction between CpFe(CO)₂ and C₇₀^-. The photochemical reaction of [Mn(CO)₅]^- with a mixture of higher fullerenes known to contain at least C₇₆, C₇₈, C₈₄, C₈₆, and C₉₀ resulted similarly in the formation of the higher fullerene complexes [Mn(CO)₄(η²-C_n)]^- (n = 76, 78, 80, 82, 84, 86, 88, 90, 92, 96, and 98), all identified using electrospray mass spectrometry.     

Synthesis of Calix[4, 5, 6] Resorcinarenes Using Fullerene C60 as Template

We present a new use of fullerene C₆₀ as a template for the synthesis of cyclic resorcinarenes, The cyclocondensation of 2-methyl-resorcinol with benzaldehyde and hexanal in THF, catalyzed by AlCl₃, in the presence of 1%, 5%, and 10% fullerene C₆₀, produces calix[4], [5], and [6] resorcinarenes, with the pentamer and hexamer as the major products. The resorcinarenes were characterized by ¹H, ¹³C NMR, FTIR, FAB⁺ mass spectrometry, and elemental analysis.     

Synthesis and Spectral Characterization of Difunctional Fullerenes

The oxidation of C₆₀ with m-chloroperbenzoic acid gave C₆₀O₂ with a high positional selectivity, as the ¹³C NMR analysis suggested. Diadducts C₆₀CCI₂O, C₆₀CCl₂(anthracene), C₆₀CCl₂[(CH₂CH₂)₂N₂], and C₆₀CCI₂[Pt-(PPh₃)₂] were synthesized, isolated, and characterized by negative ion FAB mass spectroscopy.     

Halogen and Interhalogen Reactions with [60]Fullerene: Preparation and Characterization of C60C24 and C60C18F14

U.V. irradiation of a solution of [60]fullerene in carbon tetrachloride saturated with chlorine gave a yellow solid, the negative ion FAB mass spectrum of which is consistent with the presence of C₆₀Cl₂₄ When a solution of [60]fullerene in CCl₄was mixed with IF₅, a yellow solid was deposited in the denser IF₅ layer. The negative ion FAB mass spectrum of this material indicated it to be C₆₀C₁₈F₁₄ This result provides the first confirmation that halogenation of Merenes is a radical process. Fluorination of C₆₀Br₈ gave a range of fluorinated products, having a maximum fluorine content of ca. 36 fluorines per cage, and with either C₆₀F₁₈ or its mono-oxide as major species. EI mass spectrometry of the products at various temperatures indicates that the more highly fluorinated fiiilerenes are either less stable to heat, or are more volatile.     

Stone-Wales Rearrangement Pathways from the Hinge-Opened [2+2] C60 Dimer to Ipr C120 Fullerenes. Vibrational Analysis of Intermediates

Possibility of the previously proposed hinge-opened product 2 of [2+2] C₆₀, dimer 1 transforming itself into IPR C₁₂₀ fullerenes by a series of generalized Stone-Wales (GSW) rearrangements has been tested by seeking all topologically acceptable pathways with the help of a graphical search program. the first IPR isomer 4 appeared after 20 GSW steps from the wide-bridged dumb-bell shaped precursor 3. More than 1,000 C₁₂₀ fullerene structures were generated during subsequent ten GSW steps, but the outstanding T_dC₁₂₀ global minimum 5 was not reached. Semiempirical vibrational calculations predict characteristic transition in the vibrational spectra in the course of rearrangement pathway.     

CO-DEPOSITION OF FULLERENES AND SULFUR FROM DILUTED SOLUTION

A new method to synthesize fullerene and sulfur compounds has been developed. Using this method, C₆₀S₁₆ and C₇₀S₁₆ compounds were grown from dilute fullerene and sulfur toluene solution. Their atomic structures were analyzed by x-ray diffraction with the single crystal. The C₆₀S₁₆ crystal is C-centered monoclinic structure of a=2.0874 nm, b=2.1139 nm, c=1.05690 nm and β=111.93°, and the C₇₀S₁₆ has a primitive monoclinic, P2₁/c, with lattice parameters of a=1.5271 nm, b=1.49971 nm, c=2.18024 nm and β=109.791°. In this compound, the structure of fullerenes is maintained and sulfur atoms form S₈ rings placed around the fullerenes.     

An Invariant of Carbon Arc Synthesis of Fullerenes

The yields of fullerenes C₆₀ and C₇₀ were determined in a wide range of controlled parameters. The total yield of fullerenes varied from 3 to 24%. The molar relative contents C₆₀/C₇₀ appeared to be constant for all samples of toluene extracts of the soot and equal to 5.06 ± 0.1. The accuracy of this constancy (± 2%) was determined by application of a special mathematical processing to the spectra of toluene extracts.     

STRUCTURE OF HEXA-SULFOBUTYL FULLERENES: A COMPUTATIONAL STUDY

Quantum-chemical computations are reported for hexa-sulfobutyl fullerenes C₆₀((CH₂)₄SO₃H)₆ (FC4S). FC4S represent novel water-soluble fullerene derivatives with an enhanced radical scavenging activity and also possible potential for materials science. The computations have been carried out with the standard version of the PM3 semiempirical quantum-chemical method. It is found out that the lowest among the computed eight FC4S species has the structural pattern already observed for C₆₀Cl₆. However, a larger-scale search is at present prevented by the demands on computational resources.     

C1 C60F16O: A Fluorofullerene Ether Having Exceptionally Long Chromatographic Retention

From the product of fluorination of [60]fullerene with K₂PtF₆ at 470 °C, we have isolated a small quantity (ca. 0.5 mg) of C₆₀F₁₆O, an oxahomofluorofullerene (ether) of exceptionally long HPLC retention time (50% greater than any other known fluorofullerene). The ¹⁹F NMR spectrum consists of 16 main lines and 8 minor ones, due to C₆₀F₁₆O (a single isomer of C₁ symmetry) and C₆₀F₁₆, respectively. The presence of the latter (absent on initial isolation) indicates this ether to be relatively unstable, confirmed by the failure to obtain an EI mass spectrum. The empirical formula was therefore determined by MALDI-TOF mass spectrometry in the negative-ion mode, the laser fluence being carefully adjusted at the threshold of ion formation, whence the only observable signal corresponded to the molecular ion of C₆₀F₁₆O. At slightly higher laser fluence, the base peak of C₆₀F₁₆O^·- is accompanied by C₆₀F₁₆^·- and C₆₀F₁₅O^·-. Two closely similar structures (of similar calculated stabilities) are fully consistent with the NMR data. Calculated dipole moments and the exceptionally long retention HPLC retention times suggest that both C₆₀F₁₆ and C₆₀F₁₆O may be dimers.     

EPR of Graphite and Fullerenes

Analysis of the EPR results for graphite and fullerenes has led to the development of a model for the g-factor in follerene based on the analogy between graphite and fullerene. Pressure dependence of g-factor in C₆₀ powder confirms the validity of this model. ¹³C hyperfine splitting of_a0.36 mT in pristine fullerene is also reported. The g-factors of C₆₀^-1 and C₆₀^-3 in a solution and in a different K°C₆₀ fullerides are presented. C₆₀⁺ⁿ states should be described by the spectroscopic splitting factor larger than that of a free spin.     

Raman Spectra of Chlorinated C60 and C70 Fullerenes

Raman spectra of chlorinated C₆₀ and C₇₀ fullerenes prepared by photochlorination have been reported and discussed. The Raman lines suggest structural analogies with already fully characterized brominated fullerenes. Intense laser light irradiation cause a decomposition of fullerene chloro-derivatives leading to the formation of C₆₀ polymer.     

Some New Aspects of Chlorination of Fullerenes

The effect of the reagent ratio, reaction time and power of the reagent on the product composition in chlorination of [60]fullerene was studied. Chlorofullerenes C₆₀Cl₆, C₆₀Cl₈, C₆₀Cl₁₀, C₆₀Cl₁₂, C₆₀Cl₁₄, and C₆₀Cl₂₆ were synthesized and characterized by chemical analysis, FTIR, ¹³C NMR, and MALDI TOF mass spectrometry. The experimental data supported the coexistence of several isomers of C₆₀Cl_n (n = 8, 10, 12, 14, 26); the mixtures were not separated so far. Semiempirical calculations (AM1, PM3) were used to analyze the addition patterns and resulted in the most favorable structures of C₆₀Cl_8-26. Chlorination of C₇₀ under various conditions invariably yielded C₇₀Cl₁₀.     

Fullerene Research in Poland

Main results of the investigations of fullerene and its derivatives are briefly reviewed. Such topics as plasma spectroscopy, fullerenes and nanotubes formation, C₆₀ carbyne knots, fullerene reduction and doping, charge transfer states and electroabsorption of C₆₀, electrical conductivity, superconductivity, ESR properties, fullerene clathrates, C₆₀/C₇₀ complexes with organic donors, fullerene adducts, hydrogenated fullerenes, metallofullerenes and carbon nanotubes are discussed.     

A STUDY ON THE THERMAL STABILITY TO 1000°C OF VARIOUS CARBON ALLOTROPES AND CARBONACEOUS MATTER BOTH UNDER NITROGEN AND IN AIR

The thermal behavior of graphite, C₆₀ fullerene, fullerene black (carbon soot containing fullerenes), extracted fullerene black and diamond has been analyzed to 1000°C by TGA-DTA (thermogravimetric analysis and differential thermal analysis) under a nitrogen flow at a heating rate of 20°C/min. Very small weight losses have been recorded in the case of graphite and diamond. Furthermore no diamond graphitization has been observed. The sublimation of pure C₆₀ and the fullerene fraction of fullerene black (both pristine and extracted) has been observed and discussed.

The combustion reaction in air flow of graphite, C₆₀ and C₇₀ fullerenes, fullerene black (both unextracted and extracted), carbon nanotubes and diamond has been studied by TGA-DTA at a heating rate of 20°C/min. C₇₀ fullerene and fullerene black have been found to be the most reactive carbon materials with O₂. The role played by C₇₀ in the degradation of fullerites has been discussed. Among the carbon materials examined, the best resistance to O₂ attack has been shown by diamond and carbon nanotubes. The behavior of graphite is intermediate between diamond and fullerene blacks. The behavior of C₆₀ fullerene appears closer to that of graphite although it appears to be more reactive with O₂. Samples of graphite and carbon blacks N375 and N234 have been studied by TGA-DTA in air flow before and after a radiation treatment with neutrons or γ radiation. The effect of the radiation damage in the combustion reaction of these carbon materials has been discussed.     

Fullerenes in the Fossil of Dinosaur Egg

By means of laser desorption post-ionization time-of flight mass specrometry (TOF) and high-pressure liquid chromatography (HPLC), fullerene C₆₀ have been found in a fossil of dinosaur egg shell from Xixia (N_33.3 E_111.4), China. These techniques verified also mat fullerene C₇₀ is virtually absent from identical egg fossil of dinosaur at XiXia. Preliminary results suggest that C₆₀ occurrence and C₇₀ absence may be the outcome of environment (ambient temperature, and SO₂ pollution of Earth's atmosphere, etc.) effects during the synthesis of fullerenes at 70 million years ago.     

Gas Storage in Fullerenes

Fullerenes and in particular C₆₀ have been shown to store effectively a wide range of gases from simple monatomic rare gases to diatomics and polyatomics. A review of the research in this area conducted at ANSTO is given. The trapping of Ar, Kr, Xe, and CO₂ are discussed in detail whilst preliminary results pertaining to N₂O, CH₄, CF₄, C₂H₆ and SF₆ are also reported. A range of techniques have been used to elucidate both the structure of the new fullerene intercalated solid and the trapped gas itself. The preponderant techniques used, include infra-red absorption spectroscopy (IR), X-ray powder diffraction a (XRD), neutron powder diffraction (NRD), transmission electron microscopy (TEM), and thermal gravimetric analysis (TGA).