STRUCTURE OF HEXA-SULFOBUTYL FULLERENES: A COMPUTATIONAL STUDY

ABSTRACT

Quantum-chemical computations are reported for hexa-sulfobutyl fullerenes C₆₀((CH₂)₄SO₃H)₆ (FC4S). FC4S represent novel water-soluble fullerene derivatives with an enhanced radical scavenging activity and also possible potential for materials science. The computations have been carried out with the standard version of the PM3 semiempirical quantum-chemical method. It is found out that the lowest among the computed eight FC4S species has the structural pattern already observed for C₆₀Cl₆. However, a larger-scale search is at present prevented by the demands on computational resources.     

Energy Transfer from Photoexcited State of Water Soluble Hexa(Sulfobutyl)fullerene (C60((CH2)4SO3Na)6)

Abstract

Photophysical properties and reactivities of water‐soluble micelle‐like C₆₀ derivative, C₆₀((CH₂)₄SO₃Na)₆ (abbreviated as FC₄S), at the excited triplet state were investigated using laser flash photolysis. A new transient absorption band appearing at ca. 700 nm was attributed to the triplet–triplet (T‐T) absorption band of FC₄S. This absorption was quenched by O₂ via energy transfer forming singlet oxygen, which was confirmed by its luminescence emission band; the quantum yield was evaluated to be 0.36.     

Intermolecular Interaction of [60]Fullerene with Tröger's Base Analogues

Tröger's base (TB, 1) and its analogues were synthesized and were subject to the titration experiments to evaluate their ability of supramolecular complexation with C₆₀. Results demonstrate clearly that the fluorene-based TB analogue (2) and the bioctylfluorene-based TB analogue (3) show 1:1 binding with C₆₀ to form the corresponding complexes while TB 1 does not. Titration experiments exhibited that the association constant (K_ass) of 3/C₆₀ (48.1 ± 7.9 M ^?1) was larger than that of 2/C₆₀ (13.7 ± 1.4 M ^?1)_. The formation of the 1:1 binding complexes 2/C₆₀ and 3/C₆₀ was also confirmed by MALDI-TOF mass spectrometry. Theoretical calculations suggest that 2 and 3 have appropriate cavities to embrace C₆₀. These findings indicate that not only the π/π interaction between the fluorene moieties and the C₆₀ surface but also the CH/π interaction between the octyl groups and the C₆₀ surface serve efficiently in the supramolecular complexation with C₆₀.     

Metal-Coated Fullerenes C60Mn: Calculations for M = Be,Mg, Al AND n = 12, 20, 32

Abstract

Semiempirical quantum-chemical PM3 calculations are reported for a relatively new class of exohedral metallo-fullerenes - metal-coated or metal-covered fullerenes: C₆₀M_n. The exohedral species were recently observed, however, their geometrical and electronic structure is not known yet. In this paper, relatively-even metal-atom distributions over the fullerene rings are considered - such regular forms are computed for M= Be, Mg, Al. Three selected stoichiometrics are treated: C₆₀M₁₂, C₆₀M₂₀, and C₆₀M₃₂. The stoichiometrics correspond to the location of the metal atoms above the twelve pentagons, above the twenty hexagons, and above each of the thirty two rings of C₆₀ This interesting arrangement over the rings is possible only for some types of atoms, while other elements are localized above bonds or atoms, or inside the cage, or even react and destroy the cage. Other limitation comes from the parametrization of the computational methods - the computations are performed with the PM3 semiempirical method and metal-layer atomization heats are used as a stability measure. Structural characteristics are presented, too. Considerable reductions of the cage symmetry are reported and their relationships to Jahn-Teller effect are discussed, too (no case of the icosahedral symmetry is found).     

Platinum Fulleride Reduction by Molecular Deuterium or 9, 10-dihydroanthracene

Abstract

C₆₀Pt reacts with D₂ (1-2 MPa D₂ pressure and 373-723 K) to form C₆₀D_x (x = 2-26) and Pt clusters. C₆₀ in platinum fulleride is also reduced by dihydroanthracene to hydrofullerenes. The value of E_bPt4f_7/2 (72.4 eV) obtained for platinum in the starting C₆₀Pt suggests partial charge transfer from the Pt atom to C₆₀ in C₆₀Pt.     

Bromination of [60]Fullerene. I. High‐Yield Synthesis of C60Br x (x=6, 8, 24)

Abstract

The systematic study of the bromination of C₆₀ was performed under various experimental conditions. Application of some chloroarenes as reaction media resulted in the high‐yield (70–96%) selective synthesis of C₆₀Br₆ and C₆₀Br₈. Direct bromination of fullerene yielded either C₆₀Br₈, C₆₀Br₁₄, or C₆₀Br₂₄ depending on the reaction time. Possible pathways of bromination of C₆₀Br₈ were analyzed using semiempirical (AM1) calculations, two most probable molecular structures are conjectured for the first isolated C₆₀Br₁₄.     

Laser Photolysis Study on Mechanism and Efficiency of Electron Transfer Between Fullerenes (C60 and C70) and Tetraselenafulvalenes

Abstract

Efficient electron-transfer reactions from three kind of tetraselenafulvalenes (TSeF's) to photoexcited triplet state of C₆₀ or C₇₀ in polar solvents have been confirmed by transient absorption spectroscopy observing the decay of ³C₆₀*/³C₇₀* and rise of C₆₀ ^??/C₇₀ ^??. Growth of single crystal seems to be stimulated by laser irradiation of the solution containing C₆₀ and bis(ethylenedithio)tetraselena-fulvalene (BEDT-TSeF), in which C₆₀ ^?? was effectively formed.     

Negative Ions of Trifluoromethyl Fullerene Derivatives: First Thermodynamic Data

Abstract

The mixtures of trifluoromethyl derivatives of C₆₀ were studied by Knudsen cell mass‐spectrometry. Ion–ion and electron exchange equilibria between charged and neutral species in the gas phase were investigated and the electron affinity (EA) values for C₆₀(CF₃)₆, C₆₀(CF₃)₈, and C₆₀(CF₃)₁₀ were estimated.     

Quantum Chemical ab initio Investigations of Non-Covalent Bonding Derivatives of Fullerene C60 and Li Atom or Cs2, C6H6 Molecules

Abstract

Quantum chemical ab initio investigations of the stability of the non-covalent fullerene complexes: C₆₀ molecule + Li atom, two C₆₀, two C₆₀ + CS₂, C₆₀ + CS₂, C₆₀ + C₆H₆ were performed using Hartree-Fock (HF) and Density Functional Theory (DFT) methods in various basis sets. The inclusion of electron correlation effect calculated by using DFT B3PW91 model during the optimization of Li atom position above hexagonal of C₆₀ gives the smaller distance from the centre of C₆₀ equal to 7.75 Å and large positive energy of formation equal to 4.452 kcal/mol in comparison with HF calculated distance 8.39 Å and energy of formation 1.810 kcal/mol. The positive energy of formation equal to 0.483 kcal/mol for optimized complex two C₆₀ + one CS₂ was found by HF. The presence of CS₂ molecule stabilises this complex with the energy equal to 0.281 kcal/mol. Complexes: C₆₀ + CS₂, C₆₀ + C₆H₆ do not possess the positive energy of formation.     

Synthesis,Spectral Investigations,and Thermal Stability of [60]Fullerene Complexes with TMTSF: 2(C60) · 2(TMTSF) · (C6H6), C60 · TMTSF · 2(CS2), and 2(C60) · 2(TMTSF) · (C6H5Cl)

Abstract

Molecular complexes of [60]fullerene with tetramethyltetraselenafulvalene (TMTSF): C₆₀ · (TMTSF) · 2(CS₂) (1), 2(C₆₀) · (2(TMTSF) · (C₆H₆) (2), and 2(C₆₀) · (2(TMTSF) · (C₆H₅Cl) (3) have been synthesized and their thermal stability and IR spectra vs. light polarization and temperature have been performed.     

Trifluoromethylated [60]Fullerenes: Synthesis and Characterization

Abstract

The high temperature reaction of C₆₀ with silver(I) trifluoroacetate followed by 500°C sublimation and HPLC purification has led to the characterization of the trifluoromethyl‐[60]fullerenes 1,4‐C₆₀(CF₃)₂, C _s‐C₆₀(CF₃)₄, C ₁‐C₆₀(CF₃)₄, and C ₁‐C₆₀(CF₃)₆ by EI‐MS and ¹⁹F NMR. The compounds C ₁‐C₆₀(CF₃)₄ and C ₁‐C₆₀(CF₃)₆ were obtained with 90+% compositional purity. A sample of C₆₀(CF₃)₂ also contained ca. 15–20% of a C _s‐symmetry isomer of C₆₀(CF₃)₄. The structural assignments are based on calculations at the AM1 and DFT levels of theory.     

Magnetic Properties of Some Fullerene Compounds

Abstract

Magnetic properties of some fullerene intercalation compounds are detailed. A few examples are presented including properties of 1) Acceptors: MoF₆ From magnetic measurements the existence of positively charged C₆₀ (C₆₀ ⁺) can be inferred 2) Donnors: Yb_xC₆₀ and Eu₃C₆₀ compounds. Magnetic properties of (Yb_xC₆₀) are dominated by crystal field effects. A high field magnetic transition (17 T at 4 K) occurs in Eu₃C₆₀ associated with a large hysteresis of the magnetization and relaxation effects. This complex magnetic behaviour is attribued to Eu²⁺.     

ISOLATION AND CHARACTERISATION OF C60(CF3)2

ABSTRACT

From the products of reactions of [60]fullerene with either K₂PtF₆ at 470?°C or AgF at 520?°C, we have isolated C₆₀(CF₃)₂, the simplest trifluoromethylfullerene, which gives a single ¹⁹F NMR line at ?69.5?ppm. The HPLC retention time is less than that of C₆₀F₂ confirming the trend observed for other fluoro- vs. trifluoromethylfullerenes namely that the latter elute more rapidly. Other trifluoromethyl- containing species, C₆₀(CF₃)₄O, C₆₀F₅CF₃, C₆₀(CF₃)₄H₂, C₆₀(CF₃)₆H₂, and C₆₀(CF₃H)₃ were detected in the product mixture.     

HPLC Diode‐Array Analysis of C60 and C70 Polymeric Fullerene Oxides (Fullerene Polymeric Ozonides)

Abstract

It is shown by HPLC diode‐array analysis that the C₆₀ and C₇₀ polymeric fullerene oxides ([C₆₀]‐PFOs and [C₇₀]‐PFOs) which are polymeric ozonides, are composed by nine different components. The ozonide derivatives of C₆₀ and C₇₀ have been proved to be practically analogous in chemical structure and composition. The most important component of both [C₆₀]‐PFOs and [C₇₀]‐PFOs accounts for about 3/4 of each sample. The overozonation of [C₆₀]‐PFOs in methanol has been studied and shown to not produce any significant changes.     

Interaction of methanesulfonic acid with actinide ions. The new complexes HImid[Np(C2O4)(CH3SO3)3(H2O)2], [NpO2(Terpy)(CH3SO3)(H2O)]·2H2O, and [UO2(CH3SO3)2(H2O)]

Complexation of methanesulfonic acid with Np(IV), Np(V), and U(VI) ions in aqueous solutions was studied. New crystalline compounds HImid[Np(C₂O₄)(CH₃SO₃)₃(H₂O)₂] (I), [NpO₂(Terpy)(CH₃SO₃)·(H₂O)]·2H₂O (II), and [UO₂(CH₃SO₃)₂(H₂O)] (III) were isolated. The absorption spectra of all the compounds in the IR, visible, and UV ranges were examined. The relationship between the composition, crystal structure, and IR and electronic absorption spectra of the complexes is discussed. Original Russian Text ? G.B. Andreev, N.A. Budantseva, I.G. Tananaev, B.F. Myasoedov, 2009, published in Radiokhimiya, 2009, vol. 51, no. 3, pp. 197–201.     

Bromination of [60]Fullerene. II. Crystal and Molecular Structure of [60]Fullerene Bromides,C60Br6, C60Br8, and C60Br24

Abstract

The crystal and molecular structures of the bromofullerene solvates C₆₀Br₆·0.5C₆H₅Cl·0.5Br₂, C₆₀Br₈·1.5(o‐C₆H₄Cl₂), C₆₀Br₈·Br₂, C₆₀Br₈·0.5C₆H₅Br·0.5Br₂, and C₆₀Br₂₄·2Br₂ have been determined by single crystal X‐ray diffraction. The molecular species C₆₀Br₆, C₆₀Br₈, and C₆₀Br₂₄ which have idealized C _s , C _2v  , and T _h symmetries, respectively, have several different types of C?Br and C?C bonds. A comparison between different solvates of the same bromofullerenes revealed a larger stability of the packing modes for the C₆₀Br₆ and C₆₀Br₂₄ solvates, whereas the C₆₀Br₈ solvates showed different packing motifs dependent on the nature and amount of the solvent molecules.     

Fullerane,the Hydrogenated C60 Fullerene: Properties and Astrochemical Considerations

Abstract

Hydrogenated C₆₀ fullerene, C₆₀H₃₆ was prepared in different solvents using Zn/HCl as reducing agents. The structure of C₆₀H₃₆ was confirmed both by electronic and FT‐IR spectroscopy and the purity of the reaction product was checked by HPLC analysis. It has been confirmed that C₆₀H₃₆ is not stable in air, especially in presence of light which enhances the oxidation. The oxidation of C₆₀H₃₆ was studied by FT‐IR spectroscopy and by differential scanning calorimetry (DSC) in air; the formation of hydroxyl groups on the fullerene cage and ketonic groups (involving cage breakdown) have been detected. Furthermore, the action of O₃ on C₆₀H₃₆ was investigated and it has been found that O₃ exerts practically the same effect of air but causing an enhanced cage breakdown. The thermal stability of C₆₀H₃₆ was checked by a thermogravimetric analysis (TGA) coupled with a differential thermal analysis (DTA) under N₂ flow. The vaporization of C₆₀H₃₆ occurs at very high temperature: the DTA trace has shown an endothermic peak at 540°C (at a heating rate of 20°C/min). C₆₀H₃₆ shows an electronic absorption spectrum with a maximum at about 217 nm and it is able to match both in position and in half width the peak at 217.5 nm observed in the spectrum of the interstellar extinction of light which was attributed to hydrogenated, radiation processed and thermally annealed carbon dust. Similarly, the absorption spectrum of C₆₀H₃₆ is able to match several infrared emission bands (called UIBs) detected from certain astrophysical objects like the protoplanetary nebulae (PPNe). It is proposed that hydrogenated fullerenes can be used as model compounds in the laboratory simulation studies of interstellar carbon dust.     

On Some Complexes of Allyl Derivatives of C60 Fullerene: Simulation of Molecular and Electron Structure by DFT

Abstract

The problem of existence of η³–π‐complexes of transition metal atoms with the allyl type derivatives C₆₀X₃ of C₆₀ fullerene is discussed. It is shown that complexes C₆₀X₃Co(CO)₃ (X = H, F, Cl, Br), C₆₀H₃NiC₅H₅, C₆₀H₃Fe(CO)C₅H₅, where three atoms X are bound to the C atoms of fullerene in the α‐positions relative to the same five‐membered ring in the C₆₀ fullerene, must be sufficiently stable. In these complexes the metal atoms are η³–π‐bound to the fullerene cage. In contrast to this, the metal atoms with the same allyl type C₆₀H₃ derivative of C₆₀ fullerene in the C₆₀H₃Li and C₆₀H₃FeC₅H₅ complexes are η⁵–π‐coordinated to the carbon cage. Calculations were carried out by the DFT with the exchange‐correlation potential by Perdew–Burke–Ernzerhow.     

Ab Initio Quantum Chemical Methods for Investigations of Fullerene C60, CS2 and Tetrathiafulvalene Molecules and Their Complexes

Abstract

Geometry and energy of formation of single molecules: fullerene C₆₀, CS₂ and tetrathiofulvalene (TTF) and their complexes: C₆₀ +CS₂ and C₆₀ +TTF were obtained using Hartree-Fock (HF) and Density Functional Theory methods in various basis sets. Weak chemical interactions were estimated enough well using HF/6-31G for a comparison of various geometrical conformations of these complexes. Energy of formation evaluation in charge-transfer complex C₆₀ +TTF is performing additionally calculating complex with far-separated molecules.     

Coadsorption of Oxygen and C60 Molecules on (100)Mo Surface

Abstract

Auger-electron spectroscopy was used to study oxygen adsorption on C₆₀ molecules film on (100)Mo. It appeares that one monolayer of C₆₀ molecules does not completely protect metal substrate from oxidation, and one needs thin C₆₀ film with thickness of 2-3 ML for complete reduction of oxygen penetration to the substrate from gas phase.