C60 In Benzene Research Articles

Еffect of fullerene C60 on the diffusion of organic solvents' molecules

The results of studying the dynamics of molecules of solutions of fullerene C60 in benzene and toluene are presented. The studies were carried out by the method of quasi-elastic scattering of slow neutrons. The following were determined: the total self-diffusion coefficient D, its collective Dcoll and single-particle Ds-p contributions, and molecule relaxation time τ0 before and after the dissolution of fullerene. It is necessary to pay attention to the fact that in our case a kind of neutron contrast experiment takes place. The significant difference (more than ten times) in the cross-sections for an incoherent scattering of neutrons by hydrogen and carbon nuclei made it possible to obtain diffusion parameters that characterize the dynamics of solvent molecules exclusively. It turned out that the intensity of diffusion movements of solvent molecules is almost ten times higher than the mobility of fullerene molecules.

Behavior of fullerene C70 in binary organic solvent mixtures as studied using UV-Vis spectra and dynamic light scattering

In this paper, the formation of colloidal species of fullerene C70 in organic solvents was studied. The examining of the UV-visible spectra was accompanied by particle size analysis using dynamic light scattering, DLS. Stock solutions of C70 in non-polar toluene and n-hexane were diluted with polar solvents acetonitrile and methanol. The appearance of colloidal species with a size within the range of ≈50–500 nm is accompanied by alterations of the absorption spectra. In the toluene–acetonitrile and toluene–methanol binary mixed solvents at 25 oC, the absorption spectra of C70 (5×10–6 M) tend to retain the features of the spectrum in neat aromatic solvent even if the C70 molecules are gathered into colloidal aggregates. Earlier such phenomenon was observed for C60 in benzene–acetonitrile and toluene–methanol solvent systems. This gives support to the idea of rather stable primary solvate shells formed by aromatic molecules around the fullerene molecules. The behavior of C70 in toluene mixtures with methanol was compared with the earlier reported results from this laboratory for the C60 fullerene in the same solvent system. The study of n-hexane–methanol mixtures was performed at elevated temperature because of limited miscibility of these solvents at 25 oC. Accordingly, the C70–toluene–methanol system was also examined at 40 oC. A small but distinctly noticeable difference was revealed. Whereas in the case of the last-named system, the absorption spectrum typical for molecular form of C70 is still observable when colloidal species are already present in the solution, the turning-point between molecules and colloids as determined by both UV-visible spectra and DLS coincides for the n-hexane–methanol binary mixed solvent. Hence, the solvation shells formed by the aliphatic solvent around C70 are less stable as compared with those formed by toluene. Finally, the absorption spectra of C70 in the mixed solvents toluene–n-hexane were analyzed. These data give some support to the assumption of preferable solvation of the C70 molecules by the aromatic co-solvent.

A mechanistic study of manganese(iii) acetate-mediated phosphonyl group additions to [60]- and [70]-fullerenes: the oxidative-ion-transfer mechanism vs. free radical addition.

The phosphonylation of C60 with HP(O)(OAlk)2 and Mn(OAc)3·2H2O has been considered to occur via a free radical (FR) path involving intermediate radicals ˙P(O)(OAlk)2. The present study provides evidence in support of another mechanism for the reactions, oxidative-ion-transfer (OIT). The mechanism involves the change of an acetate group in Mn(OAc)3 for the phosphonate group and oxidation of C60 by the Mn(OAc)2P(O)(OAlk)2 formed to a pair: (C60˙+, Mn(OAc)2P(O)(OAlk)2˙-) followed by the transfer of the phosphonate anion to give the monophposphonylfullerenyl radical. It undergoes reversible dimerization. The polyaddition occurs analogously. Moreover, the compounds Mn(OAc)2P(O)(OAlk)2 (Alk = Et and i-Pr) obtained make novel reagents for phosphonylation of fullerenes working by the OIT mechanism. The reactions of C60 in benzene with equimolar amounts of Mn(OAc)2P(O)(OPr-i)2 or Hg[P(O)(OPr-i)2]2 which is known as working by the FR mechanism since it produces radical ˙P(O)(OPr-i)2 under UV-irradiation, furnished the same radical ˙C60P(O)(OPr-i)2. However, at a 20-fold molar excess of the reagent toward C60, a single derivative C60[P(O)(OPr-i)2]4 and a mixture of derivatives bearing between two and eight phosphonyls were obtained in the former and latter cases, respectively. With C70, the change of the mechanism produced a change in the regioselectivity: 5 and 3 isomers of ˙C70P(O)(OPr-i)2 were obtained, respectively. DFT-calculations provided the hyperfine coupling (hfc) constants of the isomers and explained the regioselectivity change.

Synthesis and explosive decomposition of polynitro[60]fullerene

Prolonged treatment of C60 in benzene with very high concentrations of N2O4 leads to a new polynitro[60]fullerene whose composition was determined as C60(NO2)14 by thermogravimetric analysis. The compound is unstable and deflagrates above 170°C when heated under nitrogen or in air with the release of a considerable amount of heat as observed by the differential thermal analysis and as measured by differential scanning calorimetry. The decomposition steps of C60(NO2)14 were followed by the thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy analytical technique. At the deflagration point C60(NO2)14 releases a mixture of nitrogen oxides: NO2 and NO with minor amounts of N2O. The deflagration leaves a residue of oxidized carbon which by heating releases CO2 and CO and at 700°C is reduced to a carbonaceous matter free from residual oxygenated groups showing also the presence of small amounts (⩽10%) of C60 fullerene.

Surfactant-Assisted Assembly of Fullerene (C60) Nanorods and Nanotubes Formed at a Liquid–Liquid Interface

Herein we report the surfactant-triggered assembly of fullerene (C60) into 3D flowerlike microcrystals at the liquid-liquid interface. C60 crystals were grown using a liquid-liquid interfacial precipitation (LLIP) method by layering surfactant solution in butanol with a saturated solution of C60 in benzene. In the LLIP method, it is suggested that the crystal formation mechanism is driven by supersaturation related to the low C60 solubility in alcohol. We found that the dimensions of the synthesized C60 flowers depend on the concentration and surfactant type. In the absence of surfactant (i.e., in the butanol/benzene system), 1D C60 nanowhiskers (nanorods) and C60 nanotubes (diameter 400 nm-2 μm and length 5-20 μm) are obtained. However, when surfactants are incorporated into the system flowerlike microcrystals consisting of C60 nanotubes are observed. For instance, crystals grown at the interface of a 0.01% diglycerol monolaurate (C12G2) nonionic surfactant in butanol with benzene lead to the formation of flower-shaped microcrystals of average sizes in the range of 10-35 μm. To the best of our knowledge, this is the first example of the surfactant-assisted assembly of C60 crystals. X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements have shown that fullerene flowers have a hexagonal structure with cell dimensions of a = 2.539 nm and c = 1.021 nm, which differ from that of pristine C60. Mixtures of flower-shaped C60 crystals and free-standing C60 nanotubes are found in the 0.1% C12G2/butanol system. However, clusters or giant aggregates of nanowhiskers lacking any specific shape are observed in the 1% C12G2/butanol system although these crystals exhibit hexagonal close-packed structures. Flower-shaped C60 microcrystals are also observed with anionic surfactants cetyltrimethylammonium bromide (CTAB) and cetyltrimethylammonium chloride (CTAC). C60 flowers obtained from 0.01% CTAB and 0.01% CTAC also exhibit hexagonal structures with cell dimensions of a = 2.329 nm and c = 1.273 nm, a = 2.459 nm and c = 0.938 nm, respectively. Our C60 flowers exhibit intense photoluminescence (PL) and a blue-shifted PL intensity maximum compared to the same parameters for pristine C60, demonstrating the potential to control the optoelectronic properties of fullerene-based nanostructures.

ChemInform Abstract: Thermodynamic Study of the Complexes of Calix[4]naphthalenes with [60]Fullerene in Different Solvents.

Calix[4]naphthalenes are a class of molecules which possess deeper cavities than those of the analogous calix[4]arenes. Preliminary data obtained for the complexation of [60]fullerene (“C60”) with the C4-symmetrical endo-calix[4]naphthalene 3 and its tert-butyl-substituted derivative 4 show that they form supramolecular 1∶1 complexes with C60 in benzene, toluene or CS2 solution with relatively high association equilibrium constants (Kassoc). Reported herein are thermodynamic parameters and additional Kassoc determined for the complexation of C60 and calix[4]naphthalenes 3 and 4 which show that both a solvophobic effect and π–π interactions are major driving forces for the complexation process.

Interaction of polystyrene and fullerene C60 in benzene: Composition and molecular properties of the product

The molecular properties and composition of fullerene-containing polystyrenes prepared through evaporation of solvent from the combined solution of a polymer and C60 in benzene have been studied by viscometry, translational isothermal diffusion, GPC, UV spectroscopy, and electrooptical Kerr effect measurements. With this procedure of C60 introduction into the polymer, a partial depolymerization of the parent polystyrene takes place. It has been shown that the composites contain fullerene in two forms: a smaller part of C60 is bound to macromolecules, while a larger part of C60 is incorporated into the composition of low-molecularmass adducts—the products arising from the interaction of fullerene with fullerene-induced depolymerized polystyrene.

C60 Degradation Effect on Polystyrene under the Fullerene‐Polymer Interaction

Study of the content of composite polystyrene‐fullerene samples prepared from solution by the solvent evaporation method have been performed with the size exclusion chromatography, translation diffusion, viscometry and electro‐optical Kerr effect techniques. It was established that polystyrene interacts with fullerene C60 in benzene without any special treatment at room temperature just after the mixing of polymer and fullerene solutions. The product of this interaction contains initial polystyrene and low molecular fullerene adducts that appear as a result of depolymerization of a significant part (up to 40 wt.%) of polymer chains.

PHOTOSYNTHESIS OF (DIHAPTO-BUCKMINSTERFULLERENE) PENTACARBONYL TUNGSTEN (O)

(η2 ‒ C60)W(CO)5 was synthesized via the photoreaction of W(CO)6 with C60 in n-hexane using a mercury vapor lamp. The complex was characterized by elemental analysis, infrared spectroscopy in the stretching carbonyl region, and 13C-NMR spectroscopy. Three bands observed in the stretching carbonyl region at 2085 cm−1, 1996 cm−1 and 1976 cm−1 are consistent with three bands expected for the W(CO)5 fragment of the complex having C4, symmetry. A previous report that the sunlight photo-induced reaction of W(CO)6 with C60 in benzene produced (η6 ‒ C60)W(CO)3 prompted a reinvestigation of the sunlight photo-induced reaction.

Photoexcited State Properties of C60 Encapsulated in a Water-Soluble Calixarene

Abstract Properties of the excited states of C60 incorporated into a cationic homooxacalix[3]arene (C60/calixarene) in water have been investigated and compared with bare C60 in benzene. A new transient absorption band which appeared at about 545 nm was attributed to triplet-triplet (T-T) absorption band of C60/calixarene. The λmax of the T-T transition shifts to the shorter wavelength compared with that of bare C60 in benzene and the decay rate increases very much.

Thermodynamic study of the complexes of calix[4]naphthalenes with [60]fullerene in different solvents

Calix[4]naphthalenes are a class of molecules which possess deeper cavities than those of the analogous calix[4]arenes. Preliminary data obtained for the complexation of [60]fullerene (“C60”) with the C4-symmetrical endo-calix[4]naphthalene 3 and its tert-butyl-substituted derivative 4 show that they form supramolecular 1∶1 complexes with C60 in benzene, toluene or CS2 solution with relatively high association equilibrium constants (Kassoc). Reported herein are thermodynamic parameters and additional Kassoc determined for the complexation of C60 and calix[4]naphthalenes 3 and 4 which show that both a solvophobic effect and π–π interactions are major driving forces for the complexation process.

Photocycloaddition of Cyclic 1,3-Diones to C60

Irradiation of cyclic 1,3-diones (1a and 2a) with C60 in benzene leads to formation of two fused furanylfullerenes, one achiral (3) and the other chiral (4), as opposed to the expected De Mayo cyclooctane-1,3-dione addition product. The same products are obtained when 1,3-diones are replaced with trimethylsilyl-protected diones (1b and 2b). The adduct structures were characterized by MS (ESI and MALDI), IR, UV, 1H NMR, 13C NMR, and 3He NMR spectroscopy. These fullerene adducts presumably are formed after initial [2 + 2] photocycloaddition, followed by either intermolecular oxidation of the cyclobutyl intermediates (5−8) by 1O2 to form 3 or intramolecular oxidation of the appended group by the triplet fullerene moiety of 5−8 to form 4.

Solution behavior of buckminsterfullerene (C60) in benzene

Solution characterization of buckminsterfullerene C60 in benzene was carried out by laser light scattering. Static and dynamic light scattering (SLS and DLS) experiments were accomplished by using an incident laser beam of 790 nm wavelength, and a fiber optic probe which was coupled to a RCA C31034 photomultiplier tube sensitive to the near ir wavelength. The effective hydrodynamic radius of C60 in benzene solution determined by using DLS was 6.4±0.1 Å, in close agreement with the distance measured from the center of the solvated benzene to the center of the benzene-solvated C60 (C60⋅4C6H6):6.7∼6.8 Å as evaluated from the single crystal structure by x-ray diffraction. C60 was found to aggregate slowly even in fairly dilute solution concentrations ranging from 0.78 to 1.39 mg/mL at temperatures 23∼27 °C. Based on the high specific refractive index increment of C60 in benzene, the molar mass of the C60 aggregates could be estimated. Together with the radius of gyration, the hydrodynamic radius, and its size distribution, the kinetics of the aggregation process was investigated. The aggregation of C60 in benzene solution was reversible, i.e., the C60 aggregates could be dispersed simply by hand shaking the solution. The light-scattering intensity results indicated that the structure of C60 aggregates could be described as a fractal with a dimension of 2.10 and the aggregation kinetics exhibited essentially an exponential behavior.

Rise profile of the thermal lens signal: Contribution of the temperature lens and the population lens

Time profiles of the rise parts of variations of a probe beam light densities under the thermal lens (TL) experimental condition are measured with nanosecond pulsed laser excitation. The rise profile in benzene can be explained well by the probe beam expansion only by a refractive index lens due to the density fluctuation, which is induced by heat from the radiationless transition. In water, the signal is fitted well by the sum of two contributions of the refractive index change; i.e., due to the density (the thermal lens) and temperature (the temperature lens) variations. The coefficient of the temperature variation (∂n/∂T)ρ is evaluated from the relative signal intensity. The contribution of the population lens is clearly observed in the rise curve of the ‘‘TL signal’’ after the photoexcitation of C60 in benzene.

Synthesis, Characterization and Properties of Ionic Metal—Fullerene Adducts

ABSTRACTIonic metal-fullerene adducts C60M ( M = Li+, Mg2+, Ca2+, Sr2+, Ba2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, A13+ Ag+, Ce3+ ) are synthesized by reaction of watersoluble C60Lin with metal salt. 13C NMR of C60Li in D20 gives a sharp peak at 171.44 ppm which is much higher than the chemical shift of C60 in benzene ( 142.98 ppm ). Elemental analysis suggests the state of C60 in the adducts is C605-. ESR spectra of the adducts show a strong narrow peak at 9=2.001. UV-Vis and IR spectra of those adducts are completely different from those of C60. Magnetic measurement indicates that C60Li, C60Ce are antiferromagnetism and C60Fe adducts is ferromagnetism in the range of 150–300 K. But C60Fe adduct becomes paramagnetism when temperature is lower than 150 K. Mossbauer spectroscopy indicates Fe3+ in C60Fe adduct is Fe3+ (I.S.=0.30 mm/s, Q.S.=0.67 mm/s). The experimental results strongly suggest that C605- is a stable single free radical polyanion of fullerene which is a weak acid radical and possesses the similar properties with general inorganic anion. This is the first report on the synthesis and properties of air-stable and water-soluble polyanion of fullerene( C605-). A method for preparing metal-fullerene adducts has been developed, and many unusual properties of the adducts are found.

Some recent contributions to our knowledge of metallic reducing agents

Prolonged treatment of C60 in benzene with very high concentrations of N2O4 leads to a new polynitro[60]fullerene whose composition was determined as C60(NO2)14 by thermogravimetric analysis. The compound is unstable and deflagrates above 170 °C when heated under nitrogen or in air with the release of a considerable amount of heat as observed by the differential thermal analysis and as measured by differential scanning calorimetry. The decomposition steps of C60(NO2)14 were followed by the thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy analytical technique. At the deflagration point C60(NO2)14 releases a mixture of nitrogen oxides: NO2 and NO with minor amounts of N2O. The deflagration leaves a residue of oxidized carbon which by heating releases CO2 and CO and at 700 °C is reduced to a carbonaceous matter free from residual oxygenated groups showing also the presence of small amounts (⩽10%) of C60 fullerene.