In the Chase of Mixed Halofullerenes: Remarkable Transformation of C60Cl n (n = 6, 8, 12, 14) to C60Br24

Abstract

Chlorofullerenes C₆₀Cl _n (n = 6, 8, 12, 14) were found to react with bromine yielding C₆₀Br₂₄ as a single product. No intermediates containing both bromine and chlorine atoms attached to the cage were detected in the course of transformation.     

The Solid-State Mechanochemical Reaction of Fullerene C60

Abstract

The solid-state mechanochemical reaction of fullerene C₆₀ by the use of a high-speed vibration milling technique has been applied to the nucleophilic addition of an organozinc reagent to C₆₀, [4+2] cycloaddition of C₆₀ with condensed aromatic hydrocarbons, 1,3-dipolar addition of C₆₀ with organic azides, and dimerization of C₆₀.     

Bromination of [60]Fullerene. I. High‐Yield Synthesis of C60Br x (x=6, 8, 24)

Abstract

The systematic study of the bromination of C₆₀ was performed under various experimental conditions. Application of some chloroarenes as reaction media resulted in the high‐yield (70–96%) selective synthesis of C₆₀Br₆ and C₆₀Br₈. Direct bromination of fullerene yielded either C₆₀Br₈, C₆₀Br₁₄, or C₆₀Br₂₄ depending on the reaction time. Possible pathways of bromination of C₆₀Br₈ were analyzed using semiempirical (AM1) calculations, two most probable molecular structures are conjectured for the first isolated C₆₀Br₁₄.     

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.     

Effects of Intense Ultrasound Treatment of C60 Solutions

Abstract

C₆₀ was treated at room temperature, in air with intense ultrasound in the following solvents; decalin, tetralin. cyclohexane and CCl₄. It is shown by UV-VIS and FT-IR spectroscopy that in decalin and in tetralin the dominant reaction seems to be a sono-oxidation, although more complex reactions involving the solvent take place. In CC1₄ sono-oxidation is accompanied by an extensive sono-polymerization. Products in CCl₄ are C₆₀O, C₆₀O₂ and others; the sonopolymer collected from sonicated CCl₄ was easily identified by FT-IR spectroscopy. Sonopolymerization occurs also in decalin and tetralin and is promoted by free radicals as in the case of CCl₄. No reactions are observed in cyclohexane due to the very low solubility of C₆₀ in this solvent and the poor cavitation ability of cyclohexane under the action of ultrasound.     

Spontaneous Decay of Highly-Charged Fullerene Ions C60Z+ and C58z+

Abstract

Using isotope-resolved, two sector field mass spectrometric techniques we have identified and investigated quantitatively the energetics and kinetics (in particular the kinetic energy release, KER) of the spontaneous decay reactions C_60–2m ^z+ → C_60-2m-p(z-1)+ ₊ C_p ⁺ with m = 0 or 1, z ranging from 3 to 6 and p = 2 and 4. The obtained KER results are not compatible with the properties expected for a single-step fissioning reaction as described by the liquid drop model. Therefore the present data had to be interpreted by a different fragmentation mechanism. This novel reaction sequence, termed auto charge transfer (ACT) reaction, is initiated by the statistically driven neutral C₂ (or C₄₎ evaporation followed by an electron transfer process from the receding C₂ (or C₄) fragment to the remaining highly-charged fullerene ion thereby leading finally to the two charged reaction products observed in the exit channel of the decay reaction. Moreover, in the case that a C₂ ⁺ loss from C₆₀z+ is occurring in the first field-free region we have been able to demonstrate that it is possible to observe in the second field-free region a subsequent C₂ evaporation from the C₅₈(z-1)⁺ fragment ion.     

Catalytic activity of hybrid platinum nanoparticle-[C60]fullerene nanowhisker composites for 4-nitrophenol reduction

Abstract

Composites comprising platinum nanoparticles loaded on [C₆₀]fullerene nanowhiskers were prepared by a liquid-liquid interfacial precipitation method. The synthesized platinum nanoparticle-[C₆₀]fullerene nanowhisker composites were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. The catalytic activity of the platinum nanoparticle-[C₆₀]fullerene nanowhisker composites was confirmed for the reduction of 4-nitrophenol by UV–vis spectroscopy. The reduction of 4-nitrophenol catalyzed by the platinum nanoparticle-[C₆₀]fullerene nanowhisker composites followed the pseudo-first-order reaction rate law.     

Synthesis of Various Water-Soluble C60 Derivatives and Their Superoxide-Quenching Activity

Abstract

In order to examine the utility of fullerene as a medicinal application, we evaluated the reaction between fullerene derivatives and active oxygen species in vitro. This paper describes the synthesis of various water-soluble C₆₀ derivatives (cationic and anionic) and evaluation of their superoxide (O₂ ^?) quenching activity. Cationic C₆₀ derivatives showed fairly high efficiency.     

Synthesis of Various Water-Soluble G60 Derivatives and Their Superoxide-Quenching Activity

Abstract

In order to examine the utility of fullerene as a medicinal application, we evaluated the reaction between fullerene derivatives and active oxygen species in vitro. This paper describes the synthesis of various water-soluble C₆₀ derivatives (cationic and anionic) and evaluation of their superoxide (O₂ ^?) quenching activity. Cationic C₆₀ derivatives showed fairly high efficiency.     

Photo-Induced Cytotoxicity of Water-Soluble Fullerene

Abstract

The reaction of C₆₀ with poly(ethylene glycol) having a terminal primary amino group or a mixture of ethylene diamine and poly(ethylene glycol) having terminal carboxyl groups resulted in formation of water-soluble C₆₀ conjugates. These conjugates showed strong cytotoxicity to L929 cells upon visible light irradiation as a result of superoxide production.     

Nature of the anomalous dispersion of particles in fullerite-alkali-metal-halide composites

The occurrence of a solid-phase reaction between powders of the fullerite C₆₀ and potassium halides under the conditions of mechanical grinding is established. The electrostatic potential and surface-active properties of C₆₀ molecules are considered as causes of the anomalously high degree of dispersion of the particles within a composite. Pis’ma Zh. Tekh. Fiz. 25, 45–49 (April 26, 1999)     

Some New Aspects of Chlorination of Fullerenes

Abstract

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.     

Intermolecular Interaction of [60]Fullerene with Tröger's Base Analogues

Tröger's base (TB, 1) and its analogues were synthesized and were subject to the titration experiments to evaluate their ability of supramolecular complexation with C₆₀. Results demonstrate clearly that the fluorene-based TB analogue (2) and the bioctylfluorene-based TB analogue (3) show 1:1 binding with C₆₀ to form the corresponding complexes while TB 1 does not. Titration experiments exhibited that the association constant (K_ass) of 3/C₆₀ (48.1 ± 7.9 M ^?1) was larger than that of 2/C₆₀ (13.7 ± 1.4 M ^?1)_. The formation of the 1:1 binding complexes 2/C₆₀ and 3/C₆₀ was also confirmed by MALDI-TOF mass spectrometry. Theoretical calculations suggest that 2 and 3 have appropriate cavities to embrace C₆₀. These findings indicate that not only the π/π interaction between the fluorene moieties and the C₆₀ surface but also the CH/π interaction between the octyl groups and the C₆₀ surface serve efficiently in the supramolecular complexation with C₆₀.     

Esr Study of C60 N- Anion Radicals in DMSO Solution

Abstract

With the aim to stabilize reduced C₆₀ molecules of solid fulleride as free anion radicals in solution, Na_xC₆₀ (x=l, 10) was dissolved in DMSO. The Na_xC₆₀ was chosen among the other alkali-metal fullerides due to the possibility to increase a number of intercalated Na atoms in a fee. lattice of C₆₀ A sufficiently high concentration of C₆₀ anion radicals of an order of magnitude larger than that usually achieved in solution by an electrochemical reduction was obtained. The sharp resonances with the linewidths of order of 0.1 G and with g=2.0004(6) ?2.0012(8) of the room temperature ESR spectra of fluid solution were assigned from mono- to pentaanions of C₆₀. An appearance of additional sharp peaks at g=2.0016–2.0019 in the spectra of solution of nominal Na₁₀C₆₀, but Na₁C₆₀, tentatively related to C₆₀ ^n- with n>6. The results of this study showed a simple approach in an accomplishment of highly concentrated solutions of free anion radicals C₆₀ ^n-, as well as in stabilization of the anion radicals with increased n. In this way a homogeneity of alkali metal intercalation and characteristics of the solvent will be important.     

Raman Spectra of Some Fullerene Polymers

Abstract

A brief comparison between the Raman spectra of C₆₀ photopolymer with the C₆₀ sonopolymer is presented. The spectrum of C₇₀ photoproduct is also discussed.     

On Some Complexes of Allyl Derivatives of C60 Fullerene: Simulation of Molecular and Electron Structure by DFT

Abstract

The problem of existence of η³–π‐complexes of transition metal atoms with the allyl type derivatives C₆₀X₃ of C₆₀ fullerene is discussed. It is shown that complexes C₆₀X₃Co(CO)₃ (X = H, F, Cl, Br), C₆₀H₃NiC₅H₅, C₆₀H₃Fe(CO)C₅H₅, where three atoms X are bound to the C atoms of fullerene in the α‐positions relative to the same five‐membered ring in the C₆₀ fullerene, must be sufficiently stable. In these complexes the metal atoms are η³–π‐bound to the fullerene cage. In contrast to this, the metal atoms with the same allyl type C₆₀H₃ derivative of C₆₀ fullerene in the C₆₀H₃Li and C₆₀H₃FeC₅H₅ complexes are η⁵–π‐coordinated to the carbon cage. Calculations were carried out by the DFT with the exchange‐correlation potential by Perdew–Burke–Ernzerhow.     

Trifluoromethylated [60]Fullerenes: Synthesis and Characterization

Abstract

The high temperature reaction of C₆₀ with silver(I) trifluoroacetate followed by 500°C sublimation and HPLC purification has led to the characterization of the trifluoromethyl‐[60]fullerenes 1,4‐C₆₀(CF₃)₂, C _s‐C₆₀(CF₃)₄, C ₁‐C₆₀(CF₃)₄, and C ₁‐C₆₀(CF₃)₆ by EI‐MS and ¹⁹F NMR. The compounds C ₁‐C₆₀(CF₃)₄ and C ₁‐C₆₀(CF₃)₆ were obtained with 90+% compositional purity. A sample of C₆₀(CF₃)₂ also contained ca. 15–20% of a C _s‐symmetry isomer of C₆₀(CF₃)₄. The structural assignments are based on calculations at the AM1 and DFT levels of theory.     

Singlet‐Triplet Transition in the C60 2− Dianion

Abstract

The C₆₀ complexes with decamethylcobaltocene: (Cp*₂Co)₂C₆₀(C₆H₄Cl₂, C₆H₅CN)₂ (1) and [K · (18‐crown‐6)]₂ · C₆₀ · (DMF)₄ (2) have been obtained as single crystals by the diffusion method. The IR‐ and UV‐VIS‐NIR‐spectra justify the formation of the C₆₀ ^2? dianions in these salts. EPR measurements show that the low temperature signals of 1 in the 4–140 K range and 2 in the 4–60 K range have intensity corresponding only to 0.4% and 3.5% from total C₆₀. Because of this, most of the complexes are EPR silent, and, consequently, C₆₀ ^2? has a diamagnetic singlet (S = 0) state in these temperature ranges. The appearance of a broad EPR signal in the spectum of 1 above 140 K and 2 above ～60 K is assigned to a thermal population of a close lying excited triplet (S = 1) state. The singlet–triplet energy gap for C₆₀ ^2? in solid 1 and 2 was estimated to be 730 ± 10 and 300 ± 10 cm^?1.     

A Model Compound Study About Carbon Black and Diene Rubber Interaction: The Reactivity of C60 Fullerene with Squalene

Abstract

The reaction between squalene and C₆₀ fullerene was studied by electronic and FT-IR spectroscopy as well as by thermal analysis (TGA and DTA). This study was conducted to simulate in vitro, with model compounds, the interaction occuring during mixing between dienic rubber and carbon black. Squalene was used as model compound for dienic rubber and C₆₀ fullerene as model compound for carbon black since fullerene-like sites have been recently identified on carbon black surface.

The experimental results show that 2,5 molecules of C₆₀ become chemically bound to each squalene molecule under thermo-oxidative conditions simulating part of the mixing cycle between rubber and carbon black.

The implications of this result involve the explanation of the phenomenon known as “bound rubber”, which is the amount of chemisorbed polymer on filler surface after mixing, as well as the reinforcement effects observed by filling rubber with carbon black and the mechanical hysteresis of a rubber compound.     

ESR Studies on C60.OX and C60.HMTTEF

Abstract

The electron spin resonance (esr) of C₆₀.O_x and C₆₀.HMTTEF (hexamethylentetratellurafulvalene) has been investigated at 9.36 GHz as a function of temperature. T (298 T 4 K). C₆₀.O_x shows an esr absorption of equal ‘g’ value to that of C₆₀ exposed to O₂ and light but is more intense. The C₆₀ in its pure form is in a singlet state. The impurity sites introduced by O₂ produce the esr absorption. The Curie - Weiss plots of inverse esr absorption intensity versus temperature indicate an antiferromagnetic TH = 50 for air exposed C₆₀ and 90K for C₆₀O_x. From the esr intensity at room temperature, the calculated number of free spins (S = 1/2) is =1/3 per mole of C_60-O_x. In case of C₆₀.HMTTEF, there is a very weak esr absorption at room temperature suggesting that the room temperature form is diamagnetic with very small charge transfer between C₆₀ and HMTTEF. This conclusion is consistent with the structure and magnetic susceptibility of this cocrystal. As the temperature is lowered, the equilibrium: AD <=> A?^? + D?⁺ is displaced towards the formation of free radical species, A?^? and D?⁺.