Synthesis of Radiolabeled Fullerenes C60 and C70

The synthesis of radiolabeled C₆₀/C₇₀ for potential biochemical tracer studies was carried out. Vaporization under plasma are conditions (~3000C) of graphite rods impregnated with the ¹⁴C labeled steroid progesterone generates the expected C₆₀/C₇₀ mixture. Isolation and characterization of the ¹⁴C-C₆₀ is reported. Interestingly, the C₇₀ had more radioactivity than the C₆₀.     

HPLC Diode-Array Analysis of C60 and C70 Polymeric Fullerene Oxides (Fullerene Polymeric Ozonides)

It is shown by HPLC diode-array analysis that the C₆₀ and C₇₀ polymeric fullerene oxides ([C₆₀]-PFOs and [C₇₀]-PFOs) which are polymeric ozonides, are composed by nine different components. The ozonide derivatives of C₆₀ and C₇₀ have been proved to be practically analogous in chemical structure and composition. The most important component of both [C₆₀]-PFOs and [C₇₀]-PFOs accounts for about 3/4 of each sample. The overozonation of [C₆₀]-PFOs in methanol has been studied and shown to not produce any significant changes.     

Determination of C60 and/or C70 Concentrations

Two methods of quantitative analyses of the fullerenes C₆₀ and C₇₀ are described. Quantitative Infrared Spectroscopy permits the determination of the concentrations of pure and mixed compositions of C₆₀ and C₇₀ in carbondisulfide solutions. Alternatively, the ratio of C₆₀/C₇₀ is analyzed by evaluating the lattice parameters of a solid solution of the fullerene species and cyclohexane according to Vegard's Law. Both methods show high accuracy and are suited for calibration of mass spectrometric analyses of fullerene samples.     

Transport Property of C60 and C70 Single Crystals

Since a few years ago, many studies have been carried out for C₆₀ single crystals in the interest of superconductivity¹⁾ and other physical and chemical properties as a new device material. Recently, such related properties have been also interested for C₇₀ single crystals. In order to clarify the mechanism of superconductivity of C₆₀ or to discover the superconductivity of C₇₀, it is necessary to investigate the fundamental transport properties of the non-doped single crystal. In this work, to compare those transport properties of non-doped C₆₀ and C₇₀ single crystals, temperature dependence of the resistance was measured for the both single crystals prepared by a sublimation method. Each activation energy for C₆₀ or C₇₀ at high temperature was determined and phase transition temperatures for the both were discussed.     

SIMULTANEOUS DETERMINATION OF C60 AND C70 FULLERENES BY A SPECTROPHOTOMETRIC METHOD

In all fullerene-producing systems, reaction products were black soot extracts reported to contain a 5-25% fullerene mixture. Toluene extraction of the soot results in a solution of C₆₀, C₇₀, and higherc fullerenes. Without separation, absolute determination of the contents is not possible, leaving the researcher to comment only on the C₆₀/C₇₀ ratio of the solution. High-performance liquid chromatography, nuclear magnetic resonance, and scanning tunneling microscopy imaging techniques were reported in the literature for determining the C₆₀/C₇₀ ratio of the mixtures. These methods require tedious experiments and produce slightly differing results as well. In this communication, a new and relatively quick method is proposed for the simultaneous determination of the yields of C₆₀ and C₇₀ (not the ratio) in fullerene-containing solutions by ultraviolet-visible spectrophotometric analysis.     

Quantitative Determination of C60 and C70 in Soot Extracts by High Performance Liquid Chromatography and Mass Spectrometric Characterization

A quantitative HPLC method was applied to determine the amounts of C₆₀ and C₇₀ present in extracts of soot produced in the electric arc reactor and in flames. The combustion method was found to yield a higher C₇₀/C₆₀ ratio (0.67) compared with the evaporation experiment where the C₇₀/C₆₀ ratio amounts to 0.27.     

Effect of Solvents and Supporting Electrolytes on the Electrochemical Properties of C70 and its Comparison with C60

Surrounding medium effect on the electrochemical properties of C₇₀ was studied in 9 single, 2 mixture solvents and 7 supporting electrolytes by cyclic. voltammetry in the temperature range between 260 and 288K. The obtained results were analyzed and compared with those of C₆₀. It was shown that, due to the different structure between C₇₀ and C₆₀, the degree of these medium effect on their reduction potential was different. The solvent effect on the reduction of C₇₀ was more significant than that of C₆₀; on the other hand, the solvophobic interaction between the larger cations of supporting electrolyte and C₇₀ anions was weaker than that between the same cations and C₆₀ anions. In addition, C₇₀ redox couple showed better reversibility when the supporting electrolyte contains larger cations. C₇₀ redox potentials were also measured as a function of temperature, and the entropy changes of C₇₀reduction were calculated.     

Laser Photolysis Study on Mechanism and Efficiency of Electron Transfer Between Fullerenes (C60 and C70) and Tetraselenafulvalenes

Efficient electron-transfer reactions from three kind of tetraselenafulvalenes (TSeF's) to photoexcited triplet state of C₆₀ or C₇₀ in polar solvents have been confirmed by transient absorption spectroscopy observing the decay of ³C₆₀*/³C₇₀* and rise of C₆₀^-•/C₇₀^-•. Growth of single crystal seems to be stimulated by laser irradiation of the solution containing C₆₀ and bis(ethylenedithio)tetraselena-fulvalene (BEDT-TSeF), in which C₆₀^-• was effectively formed.     

Combustion Calorimetric Studies on C60 and C70

Combustion calorimetric studies on C₆₀ and C₇₀ were made using a new micro-bomb combustion calorimeter. Standard enthalpies of formation at 298.15 K were determined to be (2273±15) kJ·mol^-1 and (2375±18) kJ·mol^-1 for C₆₀ and C₇₀, respectively.     

Preparation, Separation and Characterisation of Fullerene - C60 and C70

This paper reports a simple apparatus for the synthesis of fullerenes and an efficient method for the separation of C₆₀ and C₇₀ in large amounts. The positive and negative ion mass spectra of C₆₀ and C₇₀ were measured using electron ionization and in-beam methods. Vibrational Raman spectra showed that the C₆₀ molecule adsorbed on the substrate surface may be distorted and its symmetry may be reduced under the action of the substrate surface.     

On the Action of Ultraviolet Light on C70 Fullerene

C₇₀ was photopolymerized in solution of CCl₄ under nitrogen flow by an high pressure mercury lamp. The resulting photoproduct was still soluble in common solvents and has been studied by electronic and FT-IR spectroscopy. FT-IR spectroscopy reveals a very peculiar band pattern never reported to date for C₇₀ photoproduct. Since this band pattern is very similar to that of C₆₀ photopolymer, it suggests that C₇₀ photoproduct should have a chemical structure very close to that assigned to C₆₀ photopolymer and piezopolymer.

The role played by CCl₄ in C₇₀ photopolymerization seems to be comparable to that already reported for C₆₀, i.e. it acts as a polymerization promoter.     

New Developments on the Photochlorination of C60 and C70 Fullerene and Preparation of Fullerene Derivatives: Polyfluorofullerenes and Polyfullerols.

Improved methods for photochlorination of C₆₀ and C₇₀ are described. The photoproducts fit respectively the average formulae C₆₀ Cl₄₀ and C₇₀ Cl₄₇. It is also shown that these photoproducts can be easily fluorinated by means of KF to give fluorofullerenes.

Polyhydroxyfullerene (fullerol) can be easily produced by the action of a methanolic solution of alkali over C₆₀ Cl₄₀.     

Solubility of Fullerene C60 and C70 in Toluene, o-Xylene and Carbon Disulfide at Various Temperatures

The solubilities of fullerene C₆₀ and C₇₀ in toluene, o-xylene and carbon disulfide between the melting point and boiling point of the solvents, respectively, have been measured. The temperature dependent solubility of C₆₀ displays anomalous behaviors. A solubility maximum of C₆₀ around 0 °C for toluene and carbon sulfide and around 30 °C for o-xylene was observed. The temperature-dependent solubility of C₇₀ behaves normally for all the three solvents studied.     

Direct and Catalytic Hydrogenation of Buckminsterfullerene C60

C₆₀H₁₈ was obtained by direct hydrogenation of C₆₀ at 400 C and 80 atm C₆₀ was hydrogenated to C₆₀H₃₆ as a main product in the presence of Pd/C catalyst at 180C and 30-70 atm. C₆₀H₃₆ is unstable in dichloromethane and some other organic solvents.     

Ferrocene Derivatives in Diels-Alder [4+2] Cycloaddition Reactions to Fullerenes C60 and C70

The synthesis and characterization of adducts of C₆₀ and C₇₀ with diene 5 is described. When 5 was reacted with fullerene C₆₀, a mixture of mono 7 and bisadduct 8 was found, while with C₇₀ a novel monoadduct 9 was formed.     

Growth and Characterization of C60 Crystals from Pure C60 and Fullerite

Good quality C₆₀ crystals have been grown from high purity C₆₀ powder and fullerene mixture (C₆₀/C₇₀) by vacuum sublimation method. The grown crystals were characterized with Optical microscopy, SEM, powder XRD, High Performance Liquid Chromatography and Raman spectroscopic analyses.     

Preparation of Two Novel C60 and C70 Fullerene Pyrrolidine Derivatives

C₆₀ reacted with paraformaldehyde and DL-valine in dry toluene under nitrogen to give a monoadduct. Under the similar conditions,C₇₀ gave a bisadduct. Both products were characterized by FT-IR,UV-Vis,EI-MS and NMR.The studies of the cyclic voltammetry showed that the abilities of donating electron of the products were increased compared to C₆₀ and C₇₀ respectively.     

Loss of Chlorine from C60 and C70 Chlorides

Fullerene contents of chlorinated C₆₀ and C₇₀ were determined with HPLC. n-Values of C₆₀Cl_n and C₇₀Cl_n were determined from mass increase during synthesis, MALDI-TOF mass spectrometry, PIXE, Nuclear Microprobe (¹²C[d,p]¹³C), and Electron Microprobe analysis. n-Values obtained immediately after synthesis were in the range 31-45. Best values obtained later were in the range 10-20. It is suggested that (i) the samples lost CS₂ or CS₂/CCl₄, or Cl of “crystallization” after synthesis, (ii) after synthesis the samples lost Cl bound to C₆₀ (iii) Cl was lost during the analysis, or (iv) some of all three.     

TERNARY SYSTEM OF C60 AND C70 WITH 1,2-DIMETHYLBENZENE

Differential scanning calorimetry, X-ray, and solubility measurements were used to study phase equilibria in the ternary system C₆₀-C₇₀-1,2-dimethylbenzene up to the boiling point of the solvent. Formation of the two ternary phases was confirmed. Partial solubilities of C₆₀ and C₇₀ were measured and calculated.     

Solubility of Fullerenes C60 and C70 in Seven Normal Alcohols and Their Deduced Solubility in Water

The solubilities of C₆₀ and C₇₀ at 25°C in seven normal alcohols obey the relationship InY = a + bX + cX², where Y is solubility and X is the Hildebrand solubility parameter of the solvent. Extrapolation to the solubility parameter of water yields solubilities in water of 1.3'10^-11 (C₆₀) and 1.3'10^-10(C₇₀) ng/ml with an uncertainty of one order of magnitude.