GROUP TRANSFER AND DIMERIZATION PROCESSES OF C60(CN)2 UNDER ATMOSPHERIC PRESSURE IONIZATION CONDITIONS

Neutral and anionic C₆₀(CN)₂ were investigated with electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) mass spectrometry. It was observed that its anions underwent cyano- group and oxygen transfer, and dimerization processes in ESI conditions to form C₆₀(CN)₃H^-, C₆₀(CN)₂(OH₂)^-, [C₆₀(CN)₃H]^-₂, [C₆₀(CN)₂(OH₂)]^-₂ and [(C₆₀)₂(CN)₂(OH)]^-. Meanwhile, neutral C₆₀(CN)₂, for which no signal was observed in ESIMS, showed a base peak corresponding to C₆₀(CN)₂Cl^- in APCIMS spectra with CHCl₃ used as solvent, while only a molecular ion peak corresponding to C₆₀(CN)^-₂ was observed for the toluene solution of neutral C₆₀(CN)₂ in the same conditions. Possible mechanisms for group transfer and dimerization were proposed based on these observations.     

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.     

FORCED EXPRESSION OF BCL-2 AND BCL-xL BY NOVEL WATER-SOLUBLE FULLERENE, C60(GLUCOSAMINE)6, REDUCES RENAL ISCHEMIA/REPERFUSION-INDUCED OXIDATIVE STRESS

Apoptosis induced by oxidative stress, especially reactive oxygen species, resulting from ischemia/reperfusion would lead to organ dysfunction. C₆₀(glucosamine)₆, a water-soluble fullerene with strong free radical scavenging activity, was applied to evaluate its effect on renal ischemia/reperfusion-induced apoptosis formation and superoxide generation. C₆₀(glucosamine)₆ pretreatment, but not posttreatment, significantly reduced renal ischemia/reperfusion-induced apoptosis and superoxide generation and, consequently, ameliorated renal hemodynamic effects. Up-regulation in bcl-2 and bcl-x_L of the rat kidney was evident in C₆₀(glucosamine)₆ pretreated, posttreated, and nontreated groups. However, exaggerated forced expression of bcl-2 and bcl-x_L was found in the C₆₀(glucosamine)₆ pretreated group. Our results conclude that forced expression of bcl-2 and bcl-x_L by the novel water-soluble fullerene, C₆₀(glucosamine)₆, can reduce renal ischemia/ reperfusion-induced oxidative stress.     

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.     

Spectral Properties of Single Crystals of the 2:1 Product of C60 and Tetrathiotetracene

Reaction of C₆₀ with tetrathiotetracene (TTT) gives an adduct of formula (C₆₀)₂ · TTT · 0.5CS₂. The single crystals and powdered samples of the TTT and (C₆₀)₂ · TTT · 0.5CS₂ have been spectroscopically characterized. It was shown that the transmission spectra of the adduct contain not only the IR active modes of the components but also numerous features arising from isotopic or solid-state effects due to the symmetry breaking of the C₆₀ molecules.     

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.     

Renal Effects of Water-Soluble Polyarylsulfonated C60 in Rats with An Acute Toxicity Study

Acute toxicity study of water soluble C₆₀ was conducted in young female rats with one dose intraperitoneal injection of C₆₀ ((CH₂)₄S0₃Na)_4-6. The preliminary results indicated its LD₅₀ value as approximately 600 mg/kg. The compound induced a unique phagolysosome-overload nephropathy that may serve as a biological marker in toxicity screening test for a series of synthesized water-soluble fullerenes.     

Spectroscopic Investigations of M(CO)5-C60 (M = W, MO) Complexes: Precursors for Metal Fullerides

Photochemical reactions of M(CO)₆ (M = W, Mo) with C₆₀ in solution yield η:²-complexes of M(CO)₅ with C₆₀. The complexes have been characterised by IR, UV/VIS, NMR and DSC. They do not show any orientational ordering down to 12 K and all the infrared bandwidths remain the same down to this temperature. The complexes can be decomposed thermally or photochemically yielding metal fullerides, which show characteristic reduction in peak width in the variable temperature IR spectra due to orientational ordering. Transitions are manifested in calorimetric studies also. Metal → C₆₀ charge-transfer is observed in IR and XPS. A high temperature IR study of the C₆₀-W(CO)₅ complex reveals sequential elimination of the carbonyls yielding MC₆₀. The study shows that carbonyl complexes can be used as precursors to make transition metal fullerides.     

INCORPORATED C70 IN SOL AND GEL

C₇₀ is incorporated in gel by a sol-gel process with using 3-amino-propyltriethoxysilane (NH₂(CH₂)₃Si(OC₂H₅)₃, APTS) and 3-glycidoxypropltrimethoxysilane (CH₂OCHCH₂O(CH₂)₃Si(OCH₃)₃, GPTMS) as precursors. C₇₀ is firstly mixed with APTS to form C₇₀-NH₂(CH₂)₃Si(OC₂H₅)₃ compound by the reaction between C₇₀ and amino-group of APTS, and then the compound is hybridized with GPTMS to form solid gel. The linkage of C₇₀ and APTS is estimated and confirmed with FT-IR spectra, and the UV/Visible spectra of the sol and gel are measured.     

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.     

Optical Spectra of C60 Complexes At High Pressures

A new absorption band assigned to C₆₀^- was observed around 1000 nm in the electronic spectra of (BEDT-TTF)₂C₆₀ and (ferrocene)₂C₆₀ at high pressures. The result suggests an increase in the ionicity of the complexes with increasing pressure.     

Excitons in self-organized layered perovskite films prepared by the two-step growth process

Thin films of microcrystalline (C₈H₁₇NH₃)₂PbBr₄ were prepared by a two-step growth process as follows: (1) deposition of PbBr₂ films on substrates and (2) self-organized growth of layered perovskite compounds by exposing the PbBr₂ film to C₈H₁₇NH₃Br vapor in a vacuum chamber. As-synthesized (C₈H₁₇NH₃)₂PbBr₄ films were characterized by using X-ray diffraction, temperature dependence in optical absorption and photoluminescence spectra. (C₈H₁₇NH₃)₂PbBr₄ films created by this synthesis approach were found to microcrystalline form, single phase and highly oriented with a c-axis perpendicular to the substrate surface. (C₈H₁₇NH₃)₂PbBr₄ films showed clear exciton absorption and photoluminescence even at room temperature in the near-ultraviolet region. Exciton binding energy of (C₈H₁₇NH₃)₂PbBr₄ was estimated about 200 meV.     

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

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.     

Electron Microscopic Investigations of Transformations from C60 to Diamond, Filament and Microcapillary

We report the transformation of C₆₀ into diamond by electron beam pulse annealing of flash evaporated films (at 10^-6 torr) of C,₆₀, or by direct evaporation of C₆₀ in helium (100 torr) atmosphere. The formation of filament and microcapillaries (tubulene-like structures) by electron beam annealing of the C₆₀ deposit is also 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.     

Thermolysis and Photolysis of C60 Diozonides

Ozonation of C₆₀ in o-xylene produced three C₆₀(O₃)₂ diozonides that were separated from one another and from two C₆₀(O₃)₃ triozonides by High Performance Liquid Chromatography (HPLC). Upon thermolysis at 10, 15, and 16.6°C, each of the diozonides dissociated sequentially, first to a C₆₀O(O₃) oxyozonide, then to a C₆₀O₂ diepoxide. The three diepoxides were stable in solution for at least 3 weeks. The mean lifetimes of the three diozonides were 52 ± 5, 62 ± 6, and 17.3 ± 1.8 min, respectively (all at 15°C). The mean lifetimes of the three oxyozonides were 69.7 ± 0.7 and 58 ± 6 min at 16.6°C, respectively and about 240 min at 10°C. Photolysis of the diozonides yielded two dioxidoannulenes with UV-Vis adsorption maxima at 333 and 332 nm, and what appeared to be an epoxide-oxidoannulene with UV-Vis adsorption maximum at 327 nm. These annulenes were observed to form dimers. We have synthesized and characterized six C₆₀O₂ dioxides, at least three and possibly four of which were hitherto unknown. We report the discovery of oxyozonides that form during the dissociation of diozonides.     

STRUCTURE OF HEXA-SULFOBUTYL FULLERENES: A COMPUTATIONAL STUDY

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.     

A STUDY ON THE THERMAL STABILITY OF THE PHOTOPOLYMER, THE OZOPOLYMER, AND THE PHOTOCHLORINATED DERIVATIVE OF C60 FULLERENE

The thermal stability of the C₆₀ photopolymer, the C₆₀ ozo-polymer, and photochlorinated C₆₀ was studied by thermogravimetric analysis (TGA) ultraviolet-visible (UV-vis) and TGA-differential thermal analysis techniques up to 950°C in comparison to graphite and pure C₆₀. The ozopolymer was found to be the least stable material followed by C₆₀Cl_x. The resulting residual carbonaceous matter formed by the decomposition of the photopolymer and the ozopolymer has been studied by Fourier transform-infrared (FTIR) spectroscopy and has been found to be completely comparable to carbon black. The thermal decomposition of the C₆₀ photopolymer prepared in solution yields negligible amounts of C₆₀. The main product is carbon black.     

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.     

Glycine C60 Adduct and its Rare Earth Complexes

Glycine sodium salt reacts with C₆₀ to give a water soluble derivative 1, acidification of which produces a less soluble product 2. When compound 2 is treated with Ln(CIO₄)₃ (Ln=La, Y) in several different molar ratios, insoluble rare earth complexes: C₆₀ (Gly)_xLn_x/3(OH)_y(H₂O)_z (x=7-8, y=4-6, z=2-6) were obtained. These new compounds have been characterized by IR.TG-DTA and XPS spectra.