Determination of C60 and/or C70 Concentrations

Abstract

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.     

Synthesis of Radiolabeled Fullerenes C60 and C70

Abstract

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.     

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

Abstract

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.     

Direct and Catalytic Hydrogenation of Buckminsterfullerene C60

Abstract

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.     

Preparation of Two Novel C60 and C70 Fullerene Pyrrolidine Derivatives

Abstract

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.     

Effect of Molecular Rotation on Vapor Phase Nucleation: Fullerenes C60 and C70

Abstract

The effect of rotational free energy of fullerenes C₆₀ and C₇₀ on homogeneous nucleation of crystals from vapor phase have been studied. Classical nucleation parameters have been estimated for the case of nucleation and crystal growth of C₆₀ and C₇₀ by Physical Vapor Transport (PVT) method under different supercooling in the range of 20–150 K, keeping the source temperatures constant. The result shows that the growth of large size single crystals is more feasible in the lower supercooling range. The effect of change in interfacial tension on the critical free energy of formation of the nuclei is also studied.     

Early effects of C60 Administration in Swiss Mice: A Preliminary Account for In Vivo C60 Toxicity.

Abstract

High amounts of micronized C₆₀ have been injected intraperitoneally into Swiss mice. Until the fourteenth day, they were still alive without any behaviour trouble. C₆₀ was well absorbed, and found localized in spleen and liver. Inside the liver, C₆₀ was     

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

Abstract

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.     

Raman Spectra of Chlorinated C60 and C70 Fullerenes

Abstract

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.     

On the Action of Ultraviolet Light on C70 Fullerene

Abstract

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.     

Nonlinear Stern-Volmer Fluorescence Quenching of Pyrene by C60/70

Abstract

The Stern-Volmer plot of fluorescence quenching of pyrene by C₆₀ (or C₇₀) is upward, and non linearly proportional to the fullerene concentration. Electronic absorption measurements show that pyrene and C₆₀ do not form static complexes under the experimental condition. a novel “inner filter effect” model is proposed to rationalize the observed non linear upward Stern Volmer behavior. At a given C₆₀ concentration, increasing either solvent polarity or temperature (T > 280 K) causes diminishment in the I₀/I ratio. the data strongly suggest that even at concentrations far below saturation, fullerenes form aggregates in organic solvents.     

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

Abstract

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.     

Enhancement of the quantum efficiency of radiative recombination of the fullerene C70 in a toluene solution

An investigation of the spectra and quantum efficiency of photoluminescence provided direct evidence of the presence of C₇₀ aggregates in a toluene solution. Toluene solutions of C₆₀ and C₇₀ in the proportion 1 g/l and artificial mixtures of these were studied. The hypothesis is put forward that mixed aggregates of C₆₀ and C₇₀ exist. Pis’ma Zh. Tekh. Fiz. 24, 70–75 (November 26, 1998)     

Penultimate Intermediates to C60 and C70

Abstract

Penultimate intermediates leading to C₆₀ and C₇₀ fullerenes contain one or two pairs of pentalene units and 32 to 55 kcal/mol less stable than the final products. Energy barriers of pyracylene rearrangements from these intermediates to the final products are computed to be 118 to 125 kcal/mol in height by MOPAC/AM1, which are comparable to those of preceding steps in the Stone-Wales rearrangement cascade.     

Neutron bombardment of C60 and C70 fullerenes: A spectroscopic and calorimetric study

C₆₀ and C₇₀ fullerenes were neutron-bombarded to an integral dose of 3.28×10¹⁶ n cm^?2. After the neutron treatment the trichloromethane soluble fraction was determined spectrophotometrically and C₆₀ insoluble fraction was found at 3.8% while the insoluble fraction of C₇₀ 17.9%. The formation of the CHCl₃ insoluble fraction is due to polymerization and incipient amorphization of the neutron-bombarded fullerenes where C₇₀ appears more sensitive to radiation damage than C₆₀. Raman spectroscopy was used for the characterization of the irradiated fullerenes as well as electron spin resonance (ESR) and electronic absorption spectroscopy on solid samples. Differential scanning calorimetry (DSC) to 630°C was employed for the determination of the Wigner energy of the neutron-damaged fullerenes. The results are consistent with a higher level of radiation damage reached by C₇₀ in comparison to C₆₀ at the same neutron dose.     

Possible Reaction Mechanism for the Formation of C60 From Naphthalene: A Semi-Empirical and Ab Initio Molecular Orbital Study

Abstract

Mechanism of C₆₀ formation from naphthalenes was studied by quantum chemical calculations. a patch up process of T-shape dimerization of naphthalenes followed by the intramolecular ring fusion, all through radical reactions, was proposed for a possible mechanism for the C₆₀ formation from naphthalenes. the reaction barrier was found to be less than 60-70 kcal/mol for each reaction step in this mechanism.     

A Remark on Intramolecular Transfer of an Injected Electron in C60 and C70

Abstract

A simple analysis on the intramolecular transfer of an injected electron into C₆₀ and C₇₀ has been performed based on the concept of orbital interaction. This analysis contains the partitioning of each fullerene into three parts and the examination of the frontier molecular orbital interaction for propagation of an injected electron into the whole Cgo or C70 molecule. This electron transfer process is shown to be “one-way” from energetical point of view.     

Synthesis of C60-NBN and C70-NBN(N=L, 2) by DC arc Burning Method

Abstract

Macroscopic quantities of boron-doped fullerenes, such as C_60-nB_n and C_70-nB_n(n = 1, 2), were successfully synthesized by DC arc burning method, extracted by CS₂, and characterized by field desorption mass spectra. Among them C₅₈B₂ and C₆₈B₂ were extracted for the first time. The boron-doped fullerenes were found to be less stable than their pristine fullerene analogs. When the electric current becomes too high, no boron doped fullerene, but more higher fullerenes, were formed.     

Thermal Reactions of C60 with Siliranes: Carbosilylation and Silylene Addition of Fullerenes

Thermal reactions of C₆₀ with siliranes (1a, b) afforded carbosilylated C₆₀ derivatives. When a bicyclic fused silirane (1c) was employed instead of 1a and 1b, a silylene adduct and its hydrolyzed compound were obtained through thermal extrusion of silylenes from 1c. These products were determined to be 1,2-adducts at 6,6-junctions of C₆₀ by MS, UV, and NMR analyses. These results provide a complementary method to the photochemical addition of reactive silicon compounds, which have been long employed for silylation of C₆₀. Electrochemical analyses revealed the redox properties of the silylated products, indicating the perturbation caused by silyl groups introduced on the C₆₀ cage. Theoretical calculations were also conducted for understanding of the electronic property of the silylated product.     

Ethyl oleate ozonide as an epoxidation tool of C60 and C70 fullerenes

When dissolved in ethyl oleate secondary ozonide, both C₆₀ and C₇₀ fullerenes undergo a series of epoxidation reactions. The pseudofirst-order kinetic rate constants of this process were determined spectrophotometrically at various temperatures and the activation energy for C₆₀ epoxidation through ethyl oleate ozonide was found at 25.9 kcal/mol. Furthermore, C₆₀ was found more reactive than C₇₀ with the ozonide. The kinetics rate constants of C₆₀ epoxidation with ethyl oleate ozonide were compared with the C₆₀ photo-oxidation and auto-oxidation determined in pure ethyl oleate. The epoxidation of fullerenes starts from the homolysis of the peroxide group of the 1,2,4-trioxolane ring of ethyl oleate secondary ozonide. Thus, it is suggested that fullerenes have a potential as decomposition agents of secondary ozonides in some technological applications.