Selective reduction of fullerene C60 by metals in neutral and alkaline media. Interaction of C60 with KOH

The reduction of fullerene C₆₀ by Zn and Mg in DMF was studied both in the presence and absence of KOH. Fullerene C₆₀ was reduced in these systems to form the C₆₀ ^n– (n = 1, 2, and 3) anions. The anions were detected by optical and ESR spectroscopies. It was found that Mg reduced C₆₀ to the monoanion, Mg/KOH and Zn reduced C₆₀ to the dianion, and Zn/KOH reduced C₆₀ to the trianion. Like KCN, potassium hydroxide adds to fullerene upon interaction with C₆₀ in DMF. The reaction of C₆₀ with KOH in benzonitrile was accompanied by the generation of the fullerene monoanion. A possible mechanism of the formation of fullerene monoanions in the presence of KOH is discussed. The degradation of the C₆₀ ^n– anions in air was studied.     

C60的加成反应

富勒烯化学是以全碳分子球烯为母体的新兴有机化学领域, 在材料、医学及立体化学合成方法等方面具有广泛的应用和发展前景。本文综述了C₆₀的加成反应, 较全面地展示了富勒烯的化学性质。     

Preparation and study of hydrides of fullerenes C60 and C70

Fullerene hydrides were prepared by hydrogenation of fullerences C₆₀ and C₇₀ using proton transfer from 9,10-dihydroanthracene to fullerene and were studied by mass spectrometry (electron impact, field desorption), IR, UV, and¹H and¹³C NMR spectroscopy. The main product of the hydrogenation of C₆₀ is C₆₀H₃₆, which is sufficiently stable. Hydrogenation of fullerene C₇₀ gives a series of polyhydrides C₇₀H _n (n=36–46), and the main product is C₇₀H₃₆. The dehydrogenation of C₆₀H₃₆ by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone is not quantitative and results in the formation of fullerene derivatives along with C₆₀. The comparison of the IR and¹H and¹³C NMR spectral data for solid C₆₀H₃₆ with the theoretical calculations suggests that the fullerene hydride has aT-symmetric structure and contains four isolated benzenoid rings located at tetrahedral positions on the surface of the closed skeleton of the molecule. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 4, pp. 671–678, April, 1997.     

Influence of the electrolyte composition of the subphase on the structure of 2D films of fullerene C60

The morphology of 2D films of fullerene C₆₀ on interfaces has been studied by Brewster angle microscopy and atomic force microscopy. Fullerene C₆₀ tends to aggregate, forming supramolecular structures with a surface area per C₆₀ molecule from 21.6 to 2900 Ų. As the area per C₆₀ molecule decreases, monomolecular clusters gradually transform into multiplayer structures. The introduction of an electrolyte into the system prevents the formation of fullerene globules and favors the formation of more homogeneous films.     

Synthesis of fullerene-silica hybrid materials

Fullerene/silica hybrid materials were obtained by radiation grafting on silica surface of toluene or decalin solutions of C₆₀. As determined by thermogravimetric analysis, the amount of C₆₀ grafted on silica surface was dependent from the radiation dose administered and independent from the C₆₀ concentration and the nature of the organic solvent. In absence of air, a dose of 48 kGy was sufficient to ensure a grafting level of 30% by weight of C₆₀ in the hybrid material. The fullerene/silica hybrid material shows a remarkable thermal stability, since the early decomposition starts above 300 °C as measured by DTG and DTA. The chemical structure of the fullerene/silica hybrid material was determined by FT-IR spectroscopy and with solid state ¹³C CP-MAS NMR. The potential application of such materials has been outlined.     

Effective dispersion of fullerene with methacrylate copolymer in organic solvent and poly(methyl methacrylate)

Dispersion of fullerene, C₆₀, by addition of polymethacrylate dispersant in methyl methacrylate (MMA) and incorporation of C₆₀ into poly(methyl methacrylate) (PMMA) were investigated. Copolymers synthesized by radical copolymerization of MMA and 2-naphthyl methacrylate (NMA), poly(MMA-co-NMA), effectively dispersed C₆₀ in MMA to form clusters of 20?nm. In these cases, addition of minimal 110 naphthyl groups per unit C₆₀ molecule afforded to give clusters with minimum of 20?nm sizes. Furthermore, block copolymers, poly(MMA-b-NMA) with MMA/NMA mole ratio from 12:1 to 20:1, also efficiently dispersed C₆₀ to give formation of clusters of 20?nm size by addition of minimal 40 naphthyl groups per unit C₆₀ molecule, which was corresponding to approximate nine layers of naphthyl group in block copolymer adsorbed on the surface of the cluster. Hybrid films of C₆₀/PMMA, prepared by casting of C₆₀-dispersed solution containing PMMA, exhibited absorbance at 400?nm linearly increased with C₆₀ content.     

Electrochemical formation and properties of two-component films of transition metal complexes and C60 or C70

The electrochemically active polymers have been formed during electro-reduction carried out in solution containing fullerenes, C₆₀ or C₇₀, and transition metal complexes of Pd(II), Pt(II), Rh(III), and Ir(I). In these films, fullerene moieties are covalently bounded to transition metal atoms (Pd and Pt) or their complexes (Rh and Ir) to form a polymeric network. All films exhibit electrochemical activity at negative potentials due to the fullerene cages reduction process. For all studied metal complexes, yields of formation of films containing C₇₀ are higher than yields of electrodeposition of their C₆₀ analogs. C₇₀ /M films also exhibit higher porosity in comparison to C₆₀/M layers. The differences in film morphology and efficiency of polymer formation are responsible for differences in electrochemical responses of these films in acetonitrile containing supporting electrolyte only. C₇₀/M films shows more reversible voltammeric behavior in negative potential range. They also show higher potential range of electrochemical stability. Processes of film formation and electrochemical properties of polymers depend on the transition metal ions or atoms bonding fullerene cages into polymeric network. The highest efficiency of polymerization was observed for fullerene/Pd and fullerene/Rh films. In the case of fullerene/Pd films, the charge transfer processes related to the fullerene moieties reduction in negative potential range exhibit the best reversibility among all of the studied systems. Capacitance performances of C₆₀/Pd and C₇₀/Pd films deposited on the porous Au/quartz electrode were also compared. Capacitance properties of both films are significantly affected by the conditions of electropolymerization. Only a fraction of the film having a direct contact with solution contributes to pseudocapacitance. Capacitance properties of these films also depend on the size of cations of supporting electrolyte. The C₇₀/Pd film exhibits much better capacitance performance comparison to C₆₀/Pd polymer.     

Ionic fullerene compounds containing negatively charged dimers and coordinatively bound anions

The review summarizes the results of investigations of ionic fullerene compounds containing negatively charged dimers and fullerene anions coordinated to metalloporphyrins. Fullerene radical anions were found to form diamagnetic singly bonded (C₆₀ ⁻)₂ and (C₇₀ ⁻)₂ dimers. Dimerization is reversible and leads to paramagnetic—diamagnetic phase transitions or a decrease in the magnetic moment of the complexes. The temperature, at which dissociation of the (C₆₀ ⁻)₂ dimers begins, varies from 140 to 320 K; the corresponding temperature for the (C₇₀ ⁻)₂ dimers varies from 260 to 360 K and higher. We prepared the first doubly bonded (C₆₀ ⁻)₂ dimer. At 300 K, this dimer exists as a biradical. The fullerene radical anions form Co—C coordination bonds with cobalt(II) porphyrinates. The resulting anions are diamagnetic. In some cases, Co—C coordination bonds undergo reversible dissociation, resulting in magnetic transitions from the diamagnetic to the paramagnetic state. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 361–381, March, 2007.     

Water-soluble polyketones and esters as the main stable products of ozonolysis of fullerene C60 solutions

Stable ozonolysis products of C₆₀ solutions in CCl₄, toluene, and hexane were studied by elemental analysis, HPLC, and UV and IR spectroscopy. Polyketones and esters were established for the first time to be the main stable products, whose content increased during the whole ozonolysis time (1 h). Epoxides C₆₀O _n (n = 1—6) are accumulated within 1—3 min, and after 5 min of ozonolysis their concentration decreases to zero. Fullerene C₆₀ disappears from the reaction solution due to its conversion to oxides and mechanical capturing of C₆₀ by these oxides to form a precipitate. The oxidation of C₆₀ is completed in the solid phase by the formation of the C₆₀O₁₆ oxide in which 9.68 O atoms fall on fullerene polyketones, 6 O atoms are attributed to esters, and 0.32 O atoms fall per epoxides. The optimum medium for preparation of the C₆₀ oxides is CCl₄ rather than traditional toluene, which reacts with ozone in the side reaction to form products containing active oxygen. The C₆₀ cage is raptured during ozonolysis because of the C=C bond cleavage to form two C=O groups at the ends of the open hexagon. Ozonolysis of C₆₀ solutions in CCl₄ is efficient for synthesis of water-soluble fullerene oxides due to the high yield and solubility of polyketones and esters in water.     

Polymerization of [60]fullerene activated with butyllithium

Fullerene polymerization caused by addition of an alkylating agent was discovered. Alkylation of fullerene with primary or secondary butyllithium gave both mono- and polynuclear products (polyfullerenes). The polymerization rate of the intermediates Bu _n C₆₀Li _n (n < 6) is nearly the same as the rate of the addition of BuLi to fullerene. Molecules C₆₀ can polymerize as well; however, the rate of this reaction is much lower than the polymerization rate of the reactive intermediate species.     

Redox Active Two‐Component Films of Palladium and Covalently Linked Zinc Porphyrin–Fullerene Dyad

Redox active films have been generated electrochemically by the reduction of dyads consisting of fullerene C₆₀ covalently linked to zinc meso‐tetraphenyloporphyrin, ZnP? C₆₀, and palladium acetate. The films are believed to consist of a polymeric network formed via covalent bonds between the palladium atoms and the fullerene moieties. In these films, the zinc porphyrin moiety is covalently linked to the polymeric chains through the pyrrolidine ring of the fullerene. The ZnP? C₆₀/Pt films are electrochemically active in both positive and negative potential excursions. At positive potentials, two oxidation steps for the zinc porphyrin are observed. In the negative potential range, electron transfer processes involving the zinc porphyrin and the fullerene entities are observed. Film formation is also accompanied by palladium deposition on the electrode surface. The presence of a metallic phase in the film influences its morphology, structure and electrochemical properties.     

Comparison of electrochemical properties of two-component C60-Pd polymers formed under electrochemical conditions and by chemical synthesis

The electrochemical behavior of C₆₀-Pd polymer formed under electrochemical conditions and by the chemical synthesis was examined. In these polymers, fullerene moieties are covalently bonded to palladium atoms to form a polymeric network. Both materials deposited at the electrode surface show electrochemical activity at negative potentials due to the reduction of fullerene cage. Electrochemically formed thin polymeric films exhibit much more reversible voltammetric response in comparison to chemically synthesized polymers. The morphology and electrochemical behavior of chemically synthesized C₆₀-Pd polymer depend on the composition of grown solution. Chemical polymerization results in formation of large, ca. 50 μm, crystallic superficial structures that are composed of regular spherical particles with a diameter of 150 nm. The capacitance properties of C₆₀-Pd films were investigated by cyclic voltammetry and faradaic impedance spectroscopy. Specific capacitance of chemically formed films depends on the conditions of film formation. The best capacitance properties was obtained for films containing 1:3 fullerene to Pd molar ratio. For these films, specific capacitance of 35 Fg^?1 was obtained in acetonitrile containing (n-C₄H₉)₄NClO₄. This value is much lower in comparison to the specific capacitance of electrochemically formed C₆₀-Pd film.     

Lupane type triterpenes as structuring elements in the monolayers and films of lecithin and fullerene derivatives

Using compression and wetting isotherm analysis, it was shown that lupane triterpenes (betulinol, betulinol diacetate, betulinic acid) change crucially the state of monolayers and films of C₆₀ fullerene, nitroxide malonate C₆₀ methanofullerene, and lecithin and also the films of their mixtures at the water—air interface. The structuring action of triterpenes in the presence of lecithin and C₆₀ fullerene at high triterpene contents in the film gives rise to uniaxially oriented films similar to thin films of triterpenes (atomic force microscopy data). The formation of mixed bis-nitroxide malonate methanofullerene—triterpene films with excess of the latter affords structures shaped like crater-like bowls. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1369–1378, July, 2008.     

The di-t-butylsilylene protecting group as a bridging unit in linear and macrocyclic bis-malonates for the regioselective multifunctionalization of C60

Fullerene equatorial bis-adducts have been prepared with high regioselectivity by a double Bingel reaction between [60]fullerene and di-t-butylsilylene-tethered bis-malonates. Macrocyclic bis-malonates incorporating di-t-butylsilylene moieties have also been prepared and used to functionalize C₆₀ in multiple Bingel cyclopropanations. Fullerene bis-adducts with a cis-2 addition pattern and tris-adducts with an e,e,e addition pattern have been thus obtained. Finally, the bridging di-t-butylsilylene is not only a directing group for the cyclization step, it is also a protecting group that can be readily cleaved to afford the corresponding acyclic fullerene polyols.     

Effect of fullerene C<Subscript>60</Subscript> on the structure and mechanical characteristics of polyethylene: Technological aspect

On the basis of the literature data, a retrospective analysis of the thermodynamic characteristics of dissolution of fullerene C₆₀ in a series of single-ring aromatic solvents is presented. The effect of the molecular structure of a solvent on its dissolving capacity with respect to fullerene is studied. The parameter of the boiling temperature of the solvent normalized to its molecular mass is introduced. The correlation of this parameter with the dissolving capacity of the solvent is discussed. Special emphasis is placed on the effect of halogen-containing solvents on the dissolution of fullerene and indirectly on the development of the mechanical characteristics of films prepared from common solutions of fullerene and low-density polyethylene. For comparison, the films prepared from PE melts modified with low concentrations of fullerene are considered. The film structure is studied via X-ray analysis, optical microscopy, AFM, small-angle scattering of linearly polarized light, and DSC. The films with the maximum strength are prepared from solutions in halogen-containing solvents at a concentration of fullerene below 1 wt %. In this case, spherulites are 5–10 times smaller than those in the films cast from solutions in other solvents. In the films cast from common solutions of PE and fullerene in bromobenzene, crystal solvates C₆₀ · 2C₆H₅Br are formed. It seems that the formation of the crystal solvates binds the residual solvent and thus affects the mechanical behavior of the films, thereby eliminating the plasticizing effect of residual bromobenzene. Localization of fullerene in various regions of the supramolecular structure of the films is discussed, and the morphology of the separating regions of the crystal solvate fullerene phase is analyzed.     

Electrochemically formed fullerene-based polymeric films

The recent results of investigations involving the electrochemical formation of polymers containing fullerenes and studies of their properties and applications are critically reviewed. From a structural point of view, these polymers can be divided into four main categories including (1) polymers with fullerenes physically incorporated into the foreign polymeric network without forming covalent bonds, (2) fullerene homopolymers formed via [2+2] cycloaddition, (3) “pearl necklace” polymers with fullerenes mutually linked covalently to form polymer chains, and (4) “charm bracelet” polymers containing pendant fullerene substituents. The methods of electrochemical polymerization of these systems are described and assessed. The structural features and properties of the electrochemically prepared polymers and their chemically synthesized analogs are compared. Polymer films containing fullerenes are electroactive in the negative potential range due to electroreduction of the fullerene moieties. Related films made with fullerenes derivatized with electron-donating moieties as building blocks are electroactive in both the negative and positive potential range. These can be regarded as “double cables” as they exhibit both p- and n-doping properties. Fullerene-based polymers may find numerous applications. For instance, they can be used as charge-storage and energy-converting materials for batteries and photoactive units of photovoltaic cell devices, respectively. They can be also used as substrates for electrochemical sensors and biosensors. Films of the C₆₀/Pt and C₆₀/Pd polymers containing metallic nano-particles of platinum and palladium, respectively, effectively catalyze the hydrogenation of olefins and acetylenes. Laser ablation of electrochemically formed C₆₀/M and C₇₀/M polymer films (M=Pt or Ir) results in fragmentation of the fullerenes leading to the formation of hetero-fullerenes, such as [C₅₉M]⁺ and [C₆₉M]⁺.Dedicated to Professor Dr. Alan M. Bond on the occasion of his 60th birthday.     

Base-promoted reaction of C60Cl6 with thioamides: an access to [60]fullereno[1,9-d] thiazoles

Regioselective reaction of C₆₀Cl₆ with thioamides via a radical annulation to form fullereno thiazole derivatives is reported. The reaction is promoted by K₂CO₃, which might deprotonate thioamide to initiate a single electron transfer from thioamide anion to C₆₀Cl₆. The experiments with various thioamides establish the proposed base-promoted reaction as a facile route for synthesis of fullereno fused thiazole derivatives starting from C₆₀Cl₆, a prevalent synthon in fullerene chemistry. In addition, the tunable electrochemical properties of the fullereno thiazole products have been investigated for their potential photovoltaic application.     

Rapid Separation of Hydrophobic Compounds by UPLC: in Case of Bisindolylmaleimides, Indolocarbazoles or Fullerene C60 Derivatives

Rapid separation of hydrophobic compounds such as bisindolylmaleimides, indolocarbazoles or fullerene C₆₀ derivatives by ultra performance liquid chromatography was developed. Bisindolylmaleimides and indolocarbazoles were separated within 7 and 5 min, respectively. The linear ranges for the determination of bisindolylmaleimides and indolocarbazoles were 1.25?500 pmol and 0.5?50 pmol per injection (r > 0.99), respectively. Fullerene C₆₀ derivatives were separated within 9 min, and the linear range for the determination of fullerene C₆₀ derivatives was 0.1?10 pmol per injection (r > 0.99).     

Effect of the medium on the reactivity of fullerene N60 with respect to the peroxide radicals RO2 ·. Chemiluminescence in the C60—AIBN—O2—C2H5Ph—PhH system

Chemiluminescence (CL), HLPC, and volumetry were used to demonstrate that fullerene N₆₀ exerts no inhibiting effect on the liquid-phase chain oxidation of hydrocarbons. Peroxide radicals RO₂ · do not add to N₆₀ in hydrocarbons with active C—H bond, because the reaction is suppressed by the competing addition of RO₂ · to the hydrocarbon. The addition of RO₂ · radicals to N₆₀ does occur in benzene (a solvent with strong C—H bonds) in the presence of low concentrations of the hydrocarbon oxidized. Fullerene N₆₀ is found to exhibit a new type of liquid_phase CL, which is presumably generated upon thermal decomposition of fullerene peroxides formed by adding peroxy radicals to fullerene in the C₆₀—AIBN—O₂—C₂H₅Ph—PhH system. The CL spectrum exhibits long-wavelength maxima at 645 and 685 nm. The supposed CL emitters are keto derivatives of fullerene N₆₀.