Reactivity of fullerene C<Subscript>60</Subscript>

The results of a quantum-chemical study of the reactivity of fullerene C₆₀ in such reactions as polymerization (dimerization), cycloaddition, addition of valence-saturated molecules are presented. The mechanisms of these reactions are also discussed.     

Aqueous dispersions of C<Subscript>60</Subscript> fullerene

Stable aqueous colloidal dispersions of C₆₀ fullerene are prepared. A solvatochromic effect is revealed upon the addition of C₆₀ solution in chlorobenzene to a water-acetone mixture.     

Synthesis of fullerene C<Subscript>60</Subscript> monoadducts. Cyclopropanation of C<Subscript>60</Subscript> with sulfonium ylides

3′H-Cyclopropa[1,9](C₆₀-I_h)[5,6]fullerene-3′-carboxylic acid can be synthesized in a good yield by cyclopropanation of fullerene C₆₀ with 2-(dimethyl-λ⁴-sulfanylidene)acetates provided that the ester residue is readily hydrolyzable in acid medium.     

Synthesis and structures of C<Subscript>60</Subscript> fullerene chlorides

Systematic study of chlorination of fullerene C₆₀ with inorganic chlorides SbCl₅, VCl₄, MoCl₅, and KICl₄ was carried out. Higher chlorofullerenes, viz., T _h -C₆₀Cl₂₄, C₆₀Cl₂₈, C ₂-C₆₀Cl₃₀, and D _3d -C₆₀Cl₃₀, can be prepared depending on the temperature and time of chlorination. The molecular and crystal structures of C₆₀Cl₂₄⋅VOCl₃, C₆₀Cl₃₀⋅2CS₂, and C₆₀Cl₃₀O_1.22 were determined by single-crystal X-ray diffraction. Fullerenes C₆₀Cl₂₈ and C ₂-C₆₀Cl₃₀ were shown to be only kinetically stable, whereas D _3d -C₆₀Cl₃₀ is a thermodynamically stable product. Transformations of less chlorinated fullerenes into more chlorinated products are accompanied by substantial changes in the addition patterns. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1608–1618, July, 2005.     

Catalytic hydroamination of fullerene C<Subscript>60</Subscript> with primary and secondary amines

Catalytic 1,2-hydroamination of fullerene C₆₀ with primary and secondary amines in the presence of Ti, Zr, and Hf complexes gave the corresponding alkyl-, aryl-, and hetarylaminodihydrofullerenes.     

Catalytic cycloaddition of diazoalkanes with heterocyclic substituents to fullerene C<Subscript>60</Subscript>

Methanofullerenes were directly synthesized under mild conditions by cycloaddition to fullerene C₆₀ of diazoalkanes generated in situ by oxidation of ketone hydrazones containing a heterocyclic fragment with manganese(IV) oxide in the presence of the catalytic system Pd(acac)₂-2 PPh₃-4 Et₃Al.     

The structural-phase state of C<Subscript>60</Subscript>-C<Subscript>70</Subscript> fullerene mixtures

The structural and phase state of the C₆₀-C₇₀ system at various C₆₀/C₇₀ ratios in mixtures obtained by the vaporization of solutions in toluene at ∼98°C was studied by X-ray structure analysis, differential scanning calorimetry, and infrared spectroscopy. Solid solutions based on the face-centered cubic packing of C₆₀ are not formed in the C₆₀-C₇₀ system at C₇₀ contents from 0.5 to 50 wt %. The hexagonal close packing of a solid solution of C₆₀ in C₇₀ can be formed as a result of the thermally activated decomposition of the ternary crystal solvate in the C₆₀-C₇₀-C₆H₅CH₃ system. The structural state of multiphase mixtures formed under conditions far from equilibrium is characterized by a high degree of structure imperfection and greater ability to undergo oxidation compared with C₆₀ and C₇₀.     

Bis(Allyloxycarbonyl)methano derivatives of fullerene C<Subscript>60</Subscript>

Mono-, bis-, tris-, tetrakis-, and hexakis-substituted cyclopropanation products of fullerene C₆₀ with diallyl malonate were synthesized according to Bingel-Hirsch. Except for the monocyclopropanation product, all other adducts were isolated as mixtures of regioisomers.     

Covalent binding of fullerene C<Subscript>60</Subscript> to pharmacologically important compounds

The cycloaddition of diazo compounds derived from α-tocopherol, betulinic acid, ursolic acid, and Trolox methyl esters to fullerene C₆₀ in the presence of a Pd(acac)₂-PPh₃-Et₃Al catalytic system was performed. The reactions of the diazo compounds derived from the above-mentioned pharmacologically important compounds with fullerene C₆₀ in the presence of the Pd(acac)₂-PPh₃-Et₃Al system (1: 2: 4) afford predominantly the previously inaccessible pyrazolinofullerenes. A change in the component ratio of the Pd(acac)₂-PPh₃-Et₃Al catalyst from 1: 2: 4 to 1: 4: 4 favors the formation of methanofullerenes exclusively.     

Nafion-based composite solid electrolytes containing water-soluble fullerene C<Subscript>60</Subscript> derivatives

Nafion-based composite solid polyelectrolytes containing fullerene C₆₀ and its water-soluble derivatives fullerenol-C₆₀ and tris-malonate-C60 were studied by the impedance spectroscopy method. It was found that introduction of these dopants in Nafion leads to a substantial increase in proton conductivity of the composites in the region of low relative humidity. The reasons for the influence of dopants on proton conductivity of composites were discussed.     

The standard enthalpy of formation of fullerene chloride C<Subscript>60</Subscript>Cl<Subscript>30</Subscript>

A rotating-bomb calorimeter was used to measure the energy of combustion of crystalline fullerene chloride C₆₀Cl₃₀ · 0.09Cl₂, Δ_c U° = (?24474 ± 135 kJ/mol). The result was used to calculate the standard enthalpy of formation, Δ_f H° (C₆₀Cl₃₀, cr) = 135 ± 135 kJ/mol, and the C-Cl bond energy, 195 ± 5 kJ/mol. The C-X (X = F, F, Cl, and Br) bond energies in fullerene C₆₀ derivatives and other organic compounds are compared.     

Self-assembling of fullerene C<Subscript>60</Subscript> into (C<Subscript>60</Subscript>)<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> clasters in aromatic solvents

Self-assembling of fullerene C₆₀ into (C₆₀) _n clusters in aromatic solvents was studied. The role of the π-π interactions and dispersion forces in the (C₆₀) _n cluster formation in these media is demonstrated using the data on the solubility of fullerene C₆₀ in these solvents and their ionization potentials and also spectral characteristics of fullerene C₆₀ in the range of 326–340 nm in different solvents.     

Quantitative analysis of compression isotherms of fullerene C<Subscript>60</Subscript> Langmuir layers

The structure of fullerence C₆₀ Langmuir layers formed from a solution in cyclohexane has been determined from their compression isotherms. The layer structure, in particular, the size of formed aggregates, has been shown to depend on the initial surface concentration of fullerene. A quantitative model of the Langmuir layer has been proposed. Degrees of water surface coverage with fullerene (the initial one and that corresponding to the onset of one-phase state formation), intermolecular distances of fullerene in aquaaggregates, aggregation numbers, and distances between aquaaggregates have been found to play the role of the model parameters. Constants characterizing the structure of a stable monolayer have been determined on the basis of the formulated model.     

Cycloaddition of diazoacetates to C<Subscript>60</Subscript> fullerene catalysed by Pd complexes

An efficient catalytic method of the cycloaddition to C₆₀ fullerene of the diazoacetates, containing substituents of diverse structures in ester groups, in the presence of a Pd-based three-component catalyst was developed. An influence of nature and the structure of substituent in the ester group on the activity of diazoacetates in the reaction with C₆₀ was studied. Yields of respective cycloadducts were determined.     

Electrochemical oxidation and reduction of osmium and iridium complexes with fullerene C<Subscript>60</Subscript>

The electrochemical oxidation and reduction of a series of complexes of platinum-group metals (Os, Ir, and Rh) with fullerene C₆₀ with common formula C₆₀[ML _n ] (ML _n is the metal and the metal-bonded ligands) in the tetrahydrofuran solution are studied using the method of cyclic voltammetry. The effect of metal and ligands on the variations in the redox properties of complexes and stability of anions, which are formed in the reduction, is considered. It is shown that all complexes studied are reduced more difficultly than free fullerene, and the reduced forms of metallofullerenes are less stable as compared with free fullerene anions.     

Kinetics and products derived from C<Subscript>60</Subscript> fullerene radiolysis in toluene

C₆₀ fullerene was radiolyzed in toluene solution both in presence of air and in vacuum at four different radiation doses 12, 24, 36, 48 and 96 kGy. Clear evidences of the addition of benzyl radicals to the fullerene cage derive from FT-IR and C¹³-NMR spectra of the reaction product. In presence of air the interference of oxygen is evident in the FT-IR spectra and from the elemental analysis. A detailed analysis of the kinetics of the multiple addition of benzyl radicals to the fullerene cage was made spectrophotometrically with the determination of the addition rate constants at the each addition step and the average number of benzyl groups added to the fullerene cage as function of the radiation dose.     

Inertness of C<Subscript>60</Subscript> fullerene toward RO<Subscript>2</Subscript><Superscript>·</Superscript> peroxy radicals

The reactivity of fullerene C₆₀ toward peroxy radicals RO₂ ^· was tested by the chemiluminescence method. A comparison of the influence of C₆₀ and known inhibitors on the kinetics of liquid-phase chemiluminescence (CL) during oxidation of a series of hydrocarbons (ethyl-benzene, cyclohexane, n-dodecane, and oleic acid) shows that the fullerene does not react with the RO₂ ^· radicals. A sharp decrease in the CL intensity observed upon C₆₀ addition is caused by the quenching of CL emitters with fullerene but not by inhibition of hydrocarbon oxidation. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1808–1811, August, 2005.     

Synthesis and structures of new C<Subscript>60</Subscript> fullerene derivatives containing carbonyl groups

The reactions of fullerene C₆₀ with substituted haloketones, including organophosphorus haloketones, in the presence of bases afforded new methanofullerenes containing carbonyl or carbonyl and acetal groups. The structures of the resulting compounds were established by spectroscopic methods. Their electrochemical reduction and oxidation were studied by cyclic voltammetry and ESR spectroscopy. The three-dimensional structures were calculated by the PM3 and DFT/PBE/TZ2P methods. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1424–1429, June, 2005.