Pyrolytic Trifluoromethylation of [76]-, [78]-, [84]-, and Aza[60]Fullerenes with Silver Trifluoroacetate; Evidence for Coordination of Fullerenes to Silver

Pyrolytic trifluoromethylation of [76], [78], [84], and aza[60]fullerenes with silver trifluoroacetate at 300°C results in extensive polyaddition of up to 18, 18, 20 and 20 CF₃ groups, respectively. In contrast to trifluoromethylation of [60]- and [70]fullerenes that give a full range of derivatives ranging upwards from C_n(CF₃)₂, [76]-, [78]-, and [84]-fullerenes only give C_n(CF₃)_6-18 derivatives, largely in the 10-12 CF₃ range; reaction with [76]fullerene is accompanied by formation of C₆₀(CF₃)₆ attributed to cage fragmentation. For aza[60]fullerene the hexa-addition level dominates, in contrast to its other reactions which give predominantly penta-addition products. All the compounds showed peaks at 1256±2 and 1180-1190 cm^-1, due to the CF₃ group, and peaks in this region are shown also by the soluble extract obtained on trifluoromethylation of nanotubes. As in trifluoromethylation of [60]- and [70]-fullerenes, the products obtained initially are involatile, attributed to formation os silver complexes; these are decomposed on subsequent solution in toluene. Mixed isomeric trifluoromethylated C₆₀F₈ derivatives viz. C₆₀F₇CF₃, C₆₀F₆(FG₃)₂, C₆₀F₅(CF₃)₃ and C₆₀F₄(CF₃)₄, and C₆₀F₄CF₃CF₂CF₃ (a C₆₀F₆ derivative) have been isolated from fluorination of [60]fullerene with MnF₃/K₂NilF₆ at 510°C.     

C60H18, C60H36 and C70H36 Fullerene Hydrides: Study by Methods of IR, NMR, XPS, EELS and Magnetochemistry

Fullerene hydrides of C₆₀H₁₈, C₆₀H₃₆ and C₇₀H₃₆ are studied by using IR, ¹H and ¹³C NMR, X-ray photoelectron and electron energy loss spectroscopies, and magnetochemistry. The comparison of IR and solid state ¹H and ¹³C NMR data for C₆₀H₃₆ with the theoretical ones allows the suggestion that fullerene hydride has a T symmetric structure and contains 4 isolated benzenoid rings located at tetrahedral positions on the surface of a closed skeleton of the molecule. The EELS revealed that the transition from fullerene to the hydride is accompanied by the decrease of the density of valence electrons. Magnetization measurements showed C₆₀H₃₆ to be a ferromagnet. The hydrogenated fullerenes were prepared by transfer hydrogenation procedures involving 9,10-dihydroanthracene. The compositions of the hydrides are determined by field desorption mass-spectral analysis.     

A Study of Fullerene Preparation Technique

A new homemade are fullerene generator used in this experiment is reported. The comparation of yields of fullerenes (C₆₀/C₇₀ mixture) was studied by different power supplies (AC and DC), different gaps of two graphite rods and different He pressure between 0.4×10⁴- 2.8×10⁴ Pa. In our experiment, the highest yield up to 13% was achieved, when DC discharge was used and the optimum He pressure was near 0.8×10⁴ - 1.6×10⁴ Pa.

The mixed fullerene was analyzed by electron impact masa spectnun (EIMS). The relative amount af C₆₀ to C₇₀ was 4.2 to 1. After column chromatography aeperation with hexane on alumina, 99.9% Cso was obtained. FTIR and ^1aC-NMR epectrum were ueed to characterize the pure C₆₀ samples.     

Characterization and Properties of γ-Cyclodextrin-C60 Complex In Aqueous Solution

Water soluble fullerene was prepared by complexing C₆₀ with γ-cyclodextrin. The stoichiometry of the complex [2:1, γ-CD: C₆₀] was determined by thermo gravimetric analysis. The complex was characterized by ¹H NMR, FTIR, SEM, circular dichroism and fluorescenc techniques.     

THE ELUSIVE C60S: THREE ATTEMPTED SYNTHESES

Results of semiempirical energy calculations suggested that a [6,6]-closed C₆₀S fullerene sulfide might be stable. Attempts were therefore undertaken to synthesize the compound by UV photolysis of C₆₀ in CS₂ and by the heating of mixtures of C₆₀ and S₈ to 325 and 400°C. Any sulfide, if formed, was present in undetectably small quantities. However, [¹²C₆₀³⁴S]^- ions were observed when a mixture of solid C₆₀ and elemental sulfur was analyzed by Laser Desorption Ionization Time-of-Flight mass spectrometry.     

Synthesis of Calix[4, 5, 6] Resorcinarenes Using Fullerene C60 as Template

Abstract

We present a new use of fullerene C₆₀ as a template for the synthesis of cyclic resorcinarenes, The cyclocondensation of 2‐methyl‐resorcinol with benzaldehyde and hexanal in THF, catalyzed by AlCl₃, in the presence of 1%, 5%, and 10% fullerene C₆₀, produces calix[4], [5], and [6] resorcinarenes, with the pentamer and hexamer as the major products. The resorcinarenes were characterized by ¹H, ¹³C NMR, FTIR, FAB⁺ mass spectrometry, and elemental analysis.     

Synthesis and Spectral Characterization of Difunctional Fullerenes

The oxidation of C₆₀ with m-chloroperbenzoic acid gave C₆₀O₂ with a high positional selectivity, as the ¹³C NMR analysis suggested. Diadducts C₆₀CCI₂O, C₆₀CCl₂(anthracene), C₆₀CCl₂[(CH₂CH₂)₂N₂], and C₆₀CCI₂[Pt-(PPh₃)₂] were synthesized, isolated, and characterized by negative ion FAB mass spectroscopy.     

UNSTABLE PRODUCTS FROM THE OZONATION OF C60 IN SOLVENTS

The ozonation of a solution of C₆₀ in toluene results in the formation of several unstable compounds C₆₀X and C₆₀Y[1-5] which decay completely at room temperature within about 1 h. The products are oxides C₆₀O[6,6], C₆₀O₂[I], C₆₀O₂[II], and possibly an isomer of C₆₀O₃. The transformations are not due to oxidation by atmospheric oxygen but are spontaneous. The ozonation of a solution of C₆₀O[6,6] in toluene results in the formation of two unstable compounds C₆₀Z[1-2] which also decay completely to C₆₀O₂[I] and C₆₀O₂[II]. It is suggested that all unstable “parents” are ozonides.     

EPR of Graphite and Fullerenes

Analysis of the EPR results for graphite and fullerenes has led to the development of a model for the g-factor in follerene based on the analogy between graphite and fullerene. Pressure dependence of g-factor in C₆₀ powder confirms the validity of this model. ¹³C hyperfine splitting of_a0.36 mT in pristine fullerene is also reported. The g-factors of C₆₀^-1 and C₆₀^-3 in a solution and in a different K°C₆₀ fullerides are presented. C₆₀⁺ⁿ states should be described by the spectroscopic splitting factor larger than that of a free spin.     

ISOLATION AND CHARACTERISATION OF C60(CF3)2

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.     

Some New Aspects of Chlorination of Fullerenes

The effect of the reagent ratio, reaction time and power of the reagent on the product composition in chlorination of [60]fullerene was studied. Chlorofullerenes C₆₀Cl₆, C₆₀Cl₈, C₆₀Cl₁₀, C₆₀Cl₁₂, C₆₀Cl₁₄, and C₆₀Cl₂₆ were synthesized and characterized by chemical analysis, FTIR, ¹³C NMR, and MALDI TOF mass spectrometry. The experimental data supported the coexistence of several isomers of C₆₀Cl_n (n = 8, 10, 12, 14, 26); the mixtures were not separated so far. Semiempirical calculations (AM1, PM3) were used to analyze the addition patterns and resulted in the most favorable structures of C₆₀Cl_8-26. Chlorination of C₇₀ under various conditions invariably yielded C₇₀Cl₁₀.     

Synthesis and Characterization of Dialkyl-C61

Three-step synthesis from dialkyl ketone (R₂C=O) with C₆₀ gave C₆₀(CR₂)_n [R = Me, Et, Pr, Bu, (CH₂)₅.; n = 1, 2]. The adducts were isolated by means of gel permeation chromatography, and the monoadducts were characterized by ¹H and/or ¹³C NMR spectroscopies as a mixture of major [5, 6] and minor [6, 6] isomers. Their solubility and electrochemical properties were reported.     

Evidence for η6 Coordination to a Fullerene

Evidence for the first η⁶ derivative of a fullerene, [MoC₆₀F₁₈(CO)₃] has been obtained from reaction between [Mo(CH₃CN)₃(CO)₃] and C₆₀F₁₈.     

Spectroscopic Evidence for Anionic Coordination Complexes of the Transition Metals with C70 and the Higher Fullerenes C76, C78, C82, C84, C86, C90, and C92

The carbonylate anions [M(CO)₅]^- (M = Mn, Re), [Co(CO)₄]^-, [CpFe(CO)₂]^-, and [CpM(CO)₃]^- (M = Mo, W) react with C₇₀ via single electron transfer processes to give, respectively, the corresponding 17-electron, metal-centered radicals Co(CO)₄, M(CO)₅ (M = Mn, Re), CpFe(CO)₂, and CpM(CO)₃ (M = Mo, W) in addition to the radical anion C₇₀^-. In secondary thermal or photochemical processes, the metal-centered radicals Co(CO)₄ and M(CO)₅ (M = Mn, Re) combine with the C₇₀^- to form the new η²-C₇₀ complexes [Co(CO)₃(η²-C₇₀)]^- and [M(CO)₄(η²-C₇₀)]^-. However, the metal-centered radicals CpM(CO)₃ (M = Mo, W) require photolysis to react with C₇₀^- to form [CpM(CO)₂(η²-C₇₀)]^-, whereas neither thermolysis nor photolysis induces reaction between CpFe(CO)₂ and C₇₀^-. The photochemical reaction of [Mn(CO)₅]^- with a mixture of higher fullerenes known to contain at least C₇₆, C₇₈, C₈₄, C₈₆, and C₉₀ resulted similarly in the formation of the higher fullerene complexes [Mn(CO)₄(η²-C_n)]^- (n = 76, 78, 80, 82, 84, 86, 88, 90, 92, 96, and 98), all identified using electrospray mass spectrometry.     

Arylation of [60]Fullerene with Br2/FeCl3/PhH: Formation of C58 Derivatives via CO Loss

Heating a mixture of [60]fullerene, bromine, ferric chloride and benzene under reflux for 24 h products a range of phenylated [60]fullerene derivatives. The main product is C₆₀Ph₅H but other components identified by mass spectrometry (and in some cases separated by HPLC) are: C_6oPh_n(n = 4, 6, 8, 10, 12), C₆₀Ph_nO₂(n = 4, 6, 8, 10, 12), C₆₀Ph_nOH (n = 7, 9, 11), C₆₀Ph_nH₂ (n = 4, 10), C₆₀Ph₄H₄, C₆₀Ph₅H₃, C₆₀Ph_n0₂H (n = 5, 9), C₆₀Ph₄C₆H₄O₂, C₆₀Ph₉OH₃, and C₆₀Ph₁₁ O₃H₂. In the corresponding reaction with toluene, the crude reaction mixture contained C₆₀(MeC₆H₄)₄ as a main product; C₆₀(ClC₆H₄)₅H was obtained from the reaction with chlorobenzene. Formation of these derivatives is believed to involve radical bromination of the fullerene, followed by electrophilic substitution of the hatogenofullerene into the aromatic, accompanied in some case by hydrolysis, elimination and epoxide formation; oxidation may also introduce ketone/dioxetane functionality. The EI mass spectra of C₆₀Ph₄O₂ and C₆₀Ph₈O₂show degradation to C₅₈Ph_n (n = 0-8), having structures believed to be related to the pseudofollerenes C₆₈Ph_n (n = 0-8) reported recently. These results suggest that some derivatisations of fullerenes confer stability, due to the relief of strain.     

INHIBITORY EFFECTS OF FULLERENE C60 DERIVATIVES ON ENDOTHELIUM-DERIVED RELAXATION IN RABBIT THORACIC AORTA

Inhibitory effects of newly synthesized fullerene C₆₀ derivatives 1 (C₆₀-bis(N,N-dimethylpyrrolidinium iodide)), 2 (C₆₀-proline-N-acetic acid) and 3 (C₆₀-ethylenediamine-N, N'-diacetic acid) on acetylcholine-induced relaxation in endothelium-intact rabbit thoracic aorta precontracted by phenylephrine (10^-6 M) were studied. Fullerene C₆₀ derivative 1 (3 × 10^-6 M), 2 (10^-5 M) and 3 (10^-5 M) reduced the maximum amplitude of the acetylcholine-induced relaxation without significantly changing the pD₂ values obtained from the concentration - response curves. In the presence of fullerene C₆₀ derivative 1 (10^-5 M) the acetylcholine-induced relaxation was eliminated and an acetylcholine-induced contraction was observed. These results suggest that fullerene C₆₀ derivative 1 strongly inhibits endothelium (nitric oxide)-dependent acetylcholine-induced relaxation in thoracic aorta of rabbit.     

Halogen and Interhalogen Reactions with [60]Fullerene: Preparation and Characterization of C60C24 and C60C18F14

U.V. irradiation of a solution of [60]fullerene in carbon tetrachloride saturated with chlorine gave a yellow solid, the negative ion FAB mass spectrum of which is consistent with the presence of C₆₀Cl₂₄ When a solution of [60]fullerene in CCl₄was mixed with IF₅, a yellow solid was deposited in the denser IF₅ layer. The negative ion FAB mass spectrum of this material indicated it to be C₆₀C₁₈F₁₄ This result provides the first confirmation that halogenation of Merenes is a radical process. Fluorination of C₆₀Br₈ gave a range of fluorinated products, having a maximum fluorine content of ca. 36 fluorines per cage, and with either C₆₀F₁₈ or its mono-oxide as major species. EI mass spectrometry of the products at various temperatures indicates that the more highly fluorinated fiiilerenes are either less stable to heat, or are more volatile.     

Bromination of [60]Fullerene. I. High-Yield Synthesis of C60Brx (x=6, 8, 24)

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.     

[60]Fullerene as a Novel Photoinduced Antibiotic

The antibacterial activity of [60]fullerene (C₆₀), dissolved with poly(vinylpyrrolidone) K30 (PVP), was studied. Under photo-irradiation, C₆₀/PVP aqueous solutions showed antibacterial activity, whereas PVP solution alone or fullerene solutions in the absence of light showed no activity. These results reveal that C₆₀ is a potentially good device as a photoinduced antibacterial agent.     

Ab initio calculation on fullerene C32 and Its Derivative

In this paper, we studied the equilibrium geometries, the electronic structures and the binding energies of fullerene C₃₂ as well as its hydrogenates and fluorides interactions by the SCF Hartree-Fock calculations using the latest version of GAMESS of ab initio programs. The fullerene C₃₂ is found to have a ¹A₂' closed-shell ground state in D_3d symmetry or a ¹E_U singlet state in D_3h symmetry. It is predicted to be easy to add some hydrogen or fluorine atoms to the C₃₂ cage and to produce a series of derivatives C₃₂H_2n,C₃₂F_2n (n=l, 3, 6), in which C₃₂H₂,C₃₂F₂ (D_3d), C₃₂H₆^a,C₃₂F₆^c(D_3h) are more stable. We suggest that this implies that the vertex of triplet pentagons of the C₃₂ cage is an activation site for addition.