Sorption of Light Fullerenes (C<Subscript>60</Subscript> and C<Subscript>70</Subscript>) on Materials Prepared by Sublimation of Graphite Rods

Sorption of fullerenes C₆₀ and C₇₀ from o-xylene, toluene, and o-dichlorobenzene solutions under static conditions on a sorbent prepared by sublimation of graphite rods was studied. The sorption isotherms of both fullerenes at 25°C were measured.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 2, 2005, pp. 345–346.Original Russian Text Copyright © 2005 by Semenov, Arapov, Charykov, Nekrasov, Alekhin, Gerasimov, Seregin.     

Sorption of light fullerenes C<Subscript>60</Subscript> and C<Subscript>70</Subscript> on NORIT-AZO carbon

Sorption of fullerenes C₆₀ and C₇₀ from o-xylene, toluene, and dichlorobenzene solutions on NORIT-AZO carbons was studied.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 10, 2004, pp. 1638–1642.Original Russian Text Copyright © 2004 by Semenov, Seregin, Arapov, Charykov.     

Synthesis and structure of allylated derivatives of fullerenes C<Subscript>60</Subscript> and C<Subscript>70</Subscript>

New chromatographically pure monoand hexamethanofullerenes C₆₀ and C₇₀ containing active allylic groups were synthesized by Bingel—Hirsch reaction. These compounds are promising for the studies of biological activity, as well as for obtaining on their basis new fullerenecontaining materials. The purity and composition of the synthesized compounds were confirmed by MALDI-TOF mass spectrometry and HPLC, their structure was established by ¹H and ¹³C NMR spectroscopy and X-ray diffraction.     

Synthesis and EPR investigation of nitroxyl derivatives of fullerenes C<Subscript>60</Subscript> and C<Subscript>70</Subscript>

Nitroxide derivatives of C₆₀ and C₇₀ were obtained by [3+2] cycloaddition of 4-(4-azidophenyl)-2,2,5,5-tetramethyl-3-oxy-2,5-dihydroimidazol-1-oxyl to fullerenes. The products were isolated by TLC and studied by EPR and optical spectroscopy. Molecular rotation of the adducts was shown to slow down on successive addition of the nitroxides, rotational correlation times depending nearly linearly on the number of the nitroxides added. Investigation of photochemical stability of nitroxide derivatives of C₆₀ and C₇₀ in benzene-ethanol medium reveal that the dissolved oxygen quenches efficiently the excitation of nitroxide (λ = 250–400 nm). In the absence of oxygen photoexcitation converts nitroxides to diamagnetic products, presumably, hydroxylamines formed through the interaction with the solvent.     

Circular dichroism of optically active organometallic derivatives of fullerenes C<Subscript>60</Subscript> and C<Subscript>70</Subscript>

Palladium and platinum complexes of fulleienes C₆₀ and C₇₀ containing the axially chiral ligand (—)-BITIANP (BITIANP is 2,2’-bis(diphenylphosphino)-3,3’-bi(benzo[b]thiophene)) and pynolidino[60]fullerene bearing a planar chiral organometallic π-complex substituent in the heteiocyclic ring were studied by circular dichroism (CD) spectroscopy.     

Benzene Adsorption on C<Subscript>24</Subscript>, Si@C<Subscript>24</Subscript>, Si-Doped C<Subscript>24</Subscript>, and C<Subscript>20</Subscript> Fullerenes

The absorption feasibility of benzene molecule in the C₂₄, Si@C₂₄, Si-doped C₂₄, and C₂₀ fullerenes has been studied based on calculated electronic properties of these fullerenes using Density functional Theory (DFT). It is found that energy of benzene adsorption on C₂₄, Si@C₂₄, and Si-doped C₂₄ fullerenes were in range of –2.93 and –51.19 kJ/mol with little changes in their electronic structure. The results demonstrated that the C₂₄, Si@C₂₄, and Si-doped C₂₄ fullerenes cannot be employed as a chemical adsorbent or sensor for benzene. Silicon doping cannot significantly modify both the electronic properties and benzene adsorption energy of C₂₄ fullerene. On the other hand, C₂₀ fullerene exhibits a high sensitivity, so that the energy gap of the fullerene is changed almost 89.19% after the adsorption process. We concluded that the C₂₀ fullerene can be employed as a reliable material for benzene detection.     

Features of the oxidation of C<Subscript>60</Subscript> and C<Subscript>70</Subscript> fullerites as studied by IR spectroscopy

Features of the oxidation of C₆₀ and C₇₀ fullerites were studied by infrared spectroscopy. It was shown that for C₆₀ fullerite, the presence of toluene residue reduces the temperature at which oxidation starts. The form of the toluene (solvate or nonsolvate) is not important. A low-frequency shift in the valence C-O-C vibrations of C₇₀ fullerene due to local steric strains was discovered.     

Electrooptical and Molecular Properties of Fullerene-Containing Poly(Methyl Methacrylates) Prepared by Introducing Fullerenes C<Subscript>60</Subscript> and C<Subscript>70</Subscript> into the Polymer Structure by Different Methods

Poly(methyl methacrylate) samples and their analogs containing covalently bound fullerenes C₆₀ and C₇₀ were prepared under varied synthesis conditions. The molecular weights and the electrooptical characteristics of the polymers in solutions were determined. The influence of the fullerenes on the molecular properties of poly(methyl methacrylate) was elucidated, and the most efficient method of its modification with fullerenes was proposed.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 1, 2005, pp. 139–145.Original Russian Text Copyright © 2005 by Evlampieva, Lopatin, Yakimanskii, Nazarova, Melenevskaya, Dmitrieva, Belyaev, Litvinova, Lavrenko.     

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.     

Solution ozonolysis of C<Subscript>70</Subscript>: stable products and chemiluminescence

For the first time the total and relative contents of the stable ozonolysis products of fullerene C₇₀ solutions were identified by IR spectroscopy and elemental and chemical analyses. At the 100% conversion of C₇₀ a mixture of products corresponding to the empirical formula C₇₀O_14.3H_0.21 (epoxides: polyketones: polyesters: secondary fullerene ozonides (SFOZ): acids = 1.07: 6: 6: 0.21: 1.02) is formed. The content of polyketones, polyesters, acids, and SFOZ increases during the whole ozonolysis time (1 h). The number of oxygen atoms in epoxides C₇₀O _n (n = 1–4) is lower than that in epoxides C₆₀O _n (n = 1–6) formed by the ozonolysis of fullerene C₆₀. The kinetic curve of accumulation of epoxides C₇₀O _n (n = 1–4) passes through a maximum, which is observed 0.5 min after the beginning of ozonolysis. No epoxides were identified among the products 3.5 min after the ozonolysis. The photoluminescence (PL) (λ_max = 645 and 685 nm) of fullerene polyketones in glassy EtO₂/EtOH solutions frozen at 77 K was observed. This PL is much brighter, than that of polyketones formed upon the ozonolysis of fullerenes C₆₀. For the first time the chemiluminescence (CL) was detected and studied upon the ozonolysis of C₇₀ solutions at 300 K. The CL emitters are excited states of fullerene polyketones. The CL spectrum is partially overlapped with the known CL spectrum appeared upon the ozonolysis of C₆₀ (λ_max = 685 nm) but contains the greater number of maxima (λ_max = 645 and 685 nm), which is related to a lower symmetry of the C₇₀ oxidation products.     

Electrochemical properties of transition metal complexes with C<Subscript>60</Subscript> and C<Subscript>70</Subscript> fullerne ligands (review)

t-The electrochemical properties of exohedral complexes of transition metals with metallofragments coordinated to C₆₀ and C₇₀ fullerene ligands in different coordination modes are surveyed. The effect of the nature, composition, and structure of metal-containing fragments on the electrochemical properties of these complexes and stability of products formed in the oxidation and reduction of complexes is discussed.     

The Enthalpy of Solution of the Alanine-Based Ionic Liquid [C<Subscript>4</Subscript>mim][Ala]

The molar enthalpies of solution of an alanine-based ionic liquid (IL) [C₄mim][Ala], 1-butyl-3-methylimidazolium alanine, containing various amount of water and various molalities Δ_sol H _m(wc), were measured with a solution-reaction isoperibol calorimeter at (298.15±0.01) K, where wc denotes water content. According to Archer’s method, the standard molar enthalpies of solution of [C₄mim][Ala] containing known amounts of water, D_solH_m^o(wc)\Delta_{\mathrm{sol}}H_{\mathrm{m}}^{\mathrm{o}}(\mathrm{wc}) , were obtained. In order to eliminate the effect of the small amount of residual water in the source [C₄mim][Ala], a linear fitting of D_solH_m^o(wc)\Delta_{\mathrm{sol}}H_{\mathrm{m}}^{\mathrm{o}}(\mathrm{wc}) against water content was carried out, yielding a good straight line where the intercept is the standard molar enthalpy of solution of anhydrous [C₄mim][Ala], D_solH_m^o(pure IL)=-(61.42±0.08)\Delta_{\mathrm{sol}}H_{\mathrm{m}}^{\mathrm{o}}(\mathrm{pure}\ \mathrm{IL})=-(61.42\pm 0.08) kJ⋅mol⁻¹. The hydration enthalpy of the alanine anion [Ala]⁻ was estimated using Glasser’s lattice energy theory.     

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.     

A Rational Approach Towards Determination of Optical Ionicity and Non-covalent Interactions in Fullerene-Calix[4]arene Host-Guest Complexes

The present article reports the host-guest complexation of a calix[4]arene derivative, namely 4-iso-propyl-calix[4]arene (1), with fullerenes (both C₆₀ and C₇₀) in toluene and benzonitrile solutions. It is observed that the charge-transfer (CT) absorption bands are located in the ground state for the C₆₀ and C₇₀ complexes of 1. By utilizing the CT absorption bands, various important physicochemical parameters like the oscillator strength, resonance energy, transition dipole moment, electronic coupling element and solvent reorganization energies have been estimated for the C₆₀-1 and C₇₀-1 complexes. The CT transition energy is very helpful for determining the vertical ionization potential of 1 in solution. Jobs method of continuous variation was used to establish 1:1 stoichiometry for the fullerene complexes of 1. The most fascinating feature of the present study is that 1 binds C₇₀ preferentially compared to C₆₀ as obtained from binding constant (K) data. The effect of solvent on the complexation of fullerenes (C₆₀ and C₇₀) with 1 is clearly observed from the trend in the K values: in toluene and whereas in benzonitrile, and . Molecular mechanics force field (MMMF) calculations reveal fascinating features regarding the binding pattern of fullerenes towards 1 in vacuo in terms of enthalpy of formation. MMMF calculations establish that during C₇₀-1 complexation, C₇₀ is directed in an end-on manner rather than the traditional side-on pattern.     

Molecular Structure of Tetrahydroxycalix[4]arene [-(C<Subscript>6</Subscript>H<Subscript>3</Subscript>OH)-CH<Subscript>2</Subscript>-]<Subscript>4</Subscript> in the Gas Phase

Gas-phase electron diffraction and HF/6-31G*, HF/6-31G**, and B3LYP/6-31G* ab initio calculations were used to find that in the gas phase at 242°C the calix[4]arene [-(C₆H₃OH)-CH₂-]₄ molecule possesses a C₄ conformation. Geometric parameters of the molecule were determined, and the energies of C-H?O hydrogen bonds (7.3 kcal mol^?1) were estimated by the AM1 method.     

A Quantum Chemical Study of C<Subscript>60</Subscript>Cl<Subscript>30</Subscript>, C<Subscript>60</Subscript>(OH)<Subscript>30</Subscript> Molecules and Fe@C<Subscript>60</Subscript>(OH)<Subscript>30</Subscript> Endocomplex

(U)PBE0/cc-pVDZ method is used to study the structure of C₆₀Cl₃₀, C₆₀(OH)₃₀ molecules and Fe@C₆₀(OH)₃₀ endocomplex. The triplet state of the endocomplex is shown to be the lowest in energy among its four states corresponding to different spin multiplicities and positions of Fe nucleus within the fullerene cavity. This state is characterized by bonding between the iron atom and one of two benzenoid cycles of the carbon cage, six internuclear Fe–C distances (208 pm), and 1s²2s²2p⁶3s²3p⁶3d^7.24s^0.14p^0.3 electron configuration of iron with spin population of 2.36.     

A Dft Investigation of the Interaction of B- And Al-Doped C<Subscript>60</Subscript> Fullerenes with Cyclopropylpipezarine

Interactions and natural bond orbital analysis of cyclopropylpiperazine(cppp) and B- or Al-doped C₆₀ fullerenes are investigated by quantum mechanical calculations. The structural and electronic properties, such as NH stretching vibrations, nuclear magnetic shielding tensors of ²⁷Al and ¹¹B nuclei or the energy gap are also investigated. All calculations are carried out in the gas phase and water media. Results of the bond order and the binding energy suggest that chemisorption occurs between the cppp nitrogen atom and boron or aluminum atoms of fullerenes. The Alcomplex in water is foundto have the highest binding energy. Further, AlC₅₉…cppp complexes have a slightly higher kinetic stability and a low chemical reactivity. However, BC₅₉…cppp works as a function-type sensor for cppp.     

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.