Synthesis of endohedral di-and monometallofullerenes Y<Subscript>2</Subscript>@C<Subscript>84</Subscript>, Ce<Subscript>2</Subscript>@C<Subscript>78</Subscript>, and M@C<Subscript>82</Subscript> (M = Y,Ce)

Endohedral metallofullerenes Y₂@C₈₄, Ce₂@C₇₈, and M@C₈₂ (M = Y, Ce) were synthesized by the electric arc method and isolated from the soot using extraction with o-dichlorobenzene. Pure (98%) endohedral dimetallofullerenes Y₂@C₈₄ and Ce₂@C₇₈ were isolated for the first time from o-dichlorobenzene extracts using HPLC and characterized by mass spectrometry and spectrophotometry. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2067–2071, November, 2007.     

Determination of molar extinction coefficients for endohedral metallofullerene Dy@C<Subscript>82</Subscript>(C<Subscript>2v</Subscript>)

Isomerically pure endohedral metallofullerene Dy@C₈₂(C _2v) was synthesized by the electric arc method, extracted from the soot with o-dichlorobenzene, isolated from the extract by HPLC, and characterized by mass spectrometry and spectrophotometry. The spectrophotometric titration of a solution of endohedral metallofullerene Dy@C₈₂(C _2v) was conducted with potassium perchlorotriphenylmethide. The concentration of Dy@C82(C _2v) in o-dichlorobenzene was determined, and the molar absorption coefficients for its neutral and anionic forms were calculated (3.0?10³ (at 927 nm) and 4.0?10³ mol^–1 L cm^–1 (at 884 nm), respectively.     

Endohedral Complex of Fullerene C<Subscript>60</Subscript> with Tetrahedral N<Subscript>4</Subscript>, N<Subscript>4</Subscript>@C<Subscript>60</Subscript>

B3LYP/6-31G(d) hybrid HF/DFT and BLYP/6-31G(d, p) DFT calculations were carried out to determine the structural and electronic properties of the endohedral complex of C₆₀ with Tetrahedral N₄ (T_d N₄), N₄@C₆₀. It was demonstrated that N₄ was seated in the center of the fullerene cage and the tetrahedral structure of N₄ is remained in the cage. The formation of this complex is endothermic with inclusion energy of 37.92 kcal/mol. N₄ endohedral doping perturbs the molecular orbitals of C₆₀ not so much, the calculated HOMO–LUMO gaps, the electron affinity (EA) and the ionizational potential (IP) of N₄@C₆₀ are similar to that of C₆₀.     

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.     

Theoretical study of the structure of the C<Subscript>60</Subscript>@C<Subscript>450</Subscript> nanoparticle and relative motion of the encapsulated C<Subscript>60</Subscript> molecule

The equilibrium state of the C₆₀@C₄₅₀ nanoparticle was studied. The compound was found to be stable during the encapsulation of C₆₀ tubelene. The motions of tubelene in the confinement potential field of a closed C₄₅₀ nanotube, namely, the translational motion along the tubule axis and the rotational motion were investigated in detail. It is predicted that there is a nanogyroscope inside C₄₅₀, rotating in the field of the C₆₀ capsule. Its quantized rotational states were calculated. The nanoparticle structure and energy were investigated by the tight binding method using modified parameters.     

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.     

Relative Raman Intensities in C<Subscript>6</Subscript>H<Subscript>6</Subscript>, C<Subscript>6</Subscript>D<Subscript>6</Subscript>, and C<Subscript>6</Subscript>F<Subscript>6</Subscript>: A Comparison of Different Computational Methods

The accuracy of various computational methods (Hartree–Fock, MP2, CCSD, CAS-SCF, and several types of DFT) for predicting relative intensities in Raman spectra for C₆H₆, C₆D₆, and C₆F₆ was compared. The predicted relative intensities for ν₁ and ν₂ were compared with relative intensities measured by an FT-Raman spectrometer. While none of these methods excelled at this prediction, Hartree–Fock with a large basis set was most successful for C₆H₆ and C₆D₆, while PW91PW91 was the most successful for C₆F₆.     

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.     

Electronic energy structure of As<Subscript>2</Subscript>S<Subscript>3</Subscript>, AsSI,AgAsS<Subscript>2</Subscript>, and TiS<Subscript>2</Subscript> semiconductors

Quantum-mechanical calculations with the FEFF8 code were used to study the electronic energy structure of 200-atomic clusters of As₂S₃, AsSI, AgAsS₂, and TiS₂ semiconductor compounds. The calculated local partial densities of electronic states are compared with the sulfur K and L X-ray emission spectra and sulfur K absorption spectra for fine powders of these compounds. Good agreement between theory and experiment has been obtained.     

Study on chemisorption of H<Subscript>2</Subscript>, O<Subscript>2</Subscript>, CO and C<Subscript>2</Subscript>H<Subscript>4</Subscript>on Pt-Ag/SiO<Subscript>2</Subscript>catalysts by microcalorimetry and FTIR

Adsorption microcalorimetry has been employed to study the interaction of ethylene with the reduced and oxidized Pt-Ag/SiO₂catalysts with different Ag contents to elucidate the modified effect of Ag towards the hydrocarbon processing on platinum catalysts. In addition, microcalorimetric adsorption of H₂, O₂, CO and FTIR of CO adsorption were conducted to investigate the influence of Ag on the surface structure of Pt catalyst. It is found from the microcalorimetric results of H₂and O₂adsorption that the addition of Ag to Pt/SiO₂leads to the enrichment of Ag on the catalyst surface which decreases the size of Pt surface ensembles of Pt-Ag/SiO₂catalysts. The microcalorimetry and FTIR of CO adsorption indicates that there still exist sites for linear and bridged CO adsorption on the surface of platinum catalysts simultaneously although Ag was incorporated into Pt/SiO₂. The ethylene microcalorimetric results show that the decrease of ensemble size of Pt surface sites suppresses the formation of dissociative species (ethylidyne) upon the chemisorption of C₂H₄on Pt-Ag/SiO₂. The differential heat vs. uptake plots for C₂H₄adsorption on the oxygen-preadsorbed Pt/SiO₂and Pt-Ag/SiO₂catalysts suggest that the incorporation of Ag to Pt/SiO₂could decrease the ability for the oxidation of C₂H₄.     

Quantum-chemical modeling of endohedral derivatives of buckminsterfullerenes Gd@C<Subscript>60</Subscript>(CHR)<Subscript>2</Subscript> and Gd@C<Subscript>80</Subscript>(CHR)<Subscript>2</Subscript>

The structural energies of the endohedral derivatives of buckminsterfullerenes Gd@C₆₀(CHR)₂ and Gd@C₈₀(CHR)₂ were calculated by quantum-chemical methods – semiempirical PM3 and nonempirical RHF SCF MO LCAO with the S. Huzinaga MINI minimum basis set and GAMESS software.     

Direct phosphorylation of fullerene C<Subscript>60</Subscript> with phosphine

Fullerene C₆₀ reacts with phosphine (PH3) under free radical initiation conditions (azobis(isobutyronitrile), xylene, 65°C, 6–11 h) to give in the presence of air oxygen functional oligofullerenes (yield up to 32%) containing functional groups of phosphinic and phosphonic acids.     

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.     

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.     

Quantum-chemical study of adsorption of Ag<Subscript>2</Subscript>, Ag<Subscript>4</Subscript>, and Ag<Subscript>8</Subscript> on different parts of the TiO<Subscript>2</Subscript> surface

Quantum-chemical study of the adsorption of two-, four- and eight-atomic silver clusters on stoichiometric and partially reduced rutile (110) surface, and of silver tetramer on the surface of anatase (101) was carried out in the framework of periodic DFT model. The most energetically favorable positions of clusters on the surface of TiO₂ and the mechanism of binding the clusters with the substrate were revealed. According to the calculations, the adsorption of silver clusters on the surface of stoichiometric rutile (110) is more preferable than on the partially reduced one. The mechanism of binding the clusters with the surface of anatase and rutile is shown to be similar.     

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.     

Quantum-chemical DFT calculations of the molecular structure of N<Subscript>2</Subscript>O<Subscript>5</Subscript> in the gas and solid phases

By functional density quantum-chemical method (DFT/B3LYP using the 6-311++G(3df)) it has been shown that the molecular structures of N₂O₅ with C_s and C₂ symmetries are energetically equivalent. It follows from calculations of the vibrational frequencies that both structures are characterized by potential energy minima and correspond to stationary states of the N₂O₅ molecule. It is proposed, on the basis of a comparison of the calculated and experimental vibrational spectra of N₂O₅, that dinitrogen pentaoxide exists in the gas phase as an equimolecular mixture of N₂O₅ molecules with Cs and C₂ symmetry, while in the solid phase it is characterized by the C₂ molecular structure. __________ Translated from Teoreticheskaya I éksperimental’naya Khimiya, Vol. 43, No. 1, pp. 58–63, January–February, 2007.     

Quantum-chemical modelling of nanotubes of titanium silicocarbides Ti<Subscript>2</Subscript>SiC,Ti<Subscript>3</Subscript>SiC<Subscript>2</Subscript>, and Ti<Subscript>4</Subscript>SiC<Subscript>3</Subscript>

Atomic models are proposed for nanotubes of the titanium silicocarbides Ti₂SiC, Ti₃SiC₂, and Ti₄SiC₃, and their electronic structure and interatomic interactions are investigated by the density functional tight-binding method (DFTB) in comparison with the corresponding crystalline phases. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 2, pp. 88-92, March-April, 2009.