Distribution of C60 and C70 fullerenes in the extraction system (C60 + C70)-α-pinene-ethanol-H2O

The distribution of C₆₀ and C₇₀ fullerenes in the extraction system (C₆₀ + C₇₀)-α-pinene-ethanol-H₂O was studied at constant C₆₀ to C₇₀ ratio and variable total fullerene concentration at 25°C. The relationship between the C₆₀ and C₇₀ content in ethanol (I) and α-pinene (II) phases is nonlinear over the entire fullerene concentration range.     

Investigation of fullerene C60 effect on properties of polymethylmethacrylate exposed to ionizing radiation

Effect of fullerene C₆₀ was investigated on thermal, mechanical and optical properties of polymethylmethacrylate (PMMA) under ionizing radiation. It was stated that fullerene C₆₀ behaves as an effective antirad with respect to PMMA. Fullerene C₆₀ addition raises temperature of destruction for polymer subjected to electron radiation by 20-25 °C, lowers the rate from 4 to 4.5 times and increases the activation barrier for radiated PMMA destruction reaction. Fullerene C₆₀ addition promotes improvement of strength properties of PMMA: for films containing C₆₀ addition and else subjected to electron radiation treatment a decrease in rupture strength is 10-15%, for samples containing no fullerene it equals ∼25%. Interaction of free radicals with fullerene at radiation treatment influences optical characteristics of PMMA films.     

Enhanced radical scavenging activity of polyhydroxylated C<Subscript>60</Subscript> functionalized cellulose nanocrystals

A first demonstration of conjugated polyhydroxylated fullerene (C₆₀(OH)₃₀) on the surface of cellulose nanocrystals (CNC)s is reported. These nanohybrids display favourable antioxidant performance and are an attractive alternative to derivatized fullerene nanocages reported previously. UV–Vis measurements indicated that the C₆₀(OH)₃₀-CNC system scavenged 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals to a greater degree than C₆₀(OH)₃₀ alone, due to the nucleation of C₆₀(OH)₃₀ on the surface of CNC and high colloidal stability of the engineered nanohybrid. A mechanism for the 2-stage process of the radical reaction with C₆₀(OH)₃₀-CNC is proposed, and modelled by pseudo-first order kinetics. Successful grafting of C₆₀(OH)₃₀ on CNC was confirmed by FTIR, while TEM revealed the morphology of the system with a grafting degree of 20.8 % C₆₀(OH)₃₀. Zeta potential measurements of C₆₀(OH)₃₀-CNC in aqueous solution showed a high stability in the pH range 4.0-8.0, indicating functionality of the CNC based antioxidant system as a biocompatible and sustainable protocol with potential for use in personal care applications.     

[60]Fullerene diol issued from pentaerythritol derivatives

A new [60]fullerene diol is synthesized in good yield, in two steps starting from reaction of C₆₀²⁻ anion with the benzylideneacetal derived from 2,2-bis(iodomethyl)-1,3-propanediol. The corresponding [60]fullerene bis-mesylate is also formed in a similar way starting from bis-iodo bis-mesylate compound in the same series. The scope of this fullerene diol in synthesis is exemplified by its easy esterification with 4-formyl benzoyl chloride.     

Regioselective synthesis of tetra(aryl)-mono(silylmethyl)[60]fullerenes and derivatization to methanofullerene compound

A method for the facile synthesis of tetraaryl-trimethylsilylmethyl-hydro[60]fullerenes, C₆₀Ar₄(CH₂SiMeR)H, has been developed in which readily prepared anionic mono(silylmethyl) fullerene is subjected to reaction conditions for organocopper-mediated multiple addition. Penta(organo)fullerene derivatives bearing different substituents and diverse functionality were synthesized in moderate to good yield under simple and mild reaction conditions. Further organic and organometallic transformations of these fullerenes allowed us to synthesize transition-metal complexes and a new methanofullerene derivative, 1,9-methano-6,12,15,18-tetraphenyl[60]fullerene, C₆₀Ph₄(CH₂).     

Exohedral Addition Chemistry of the Fullerenide Anions C602− and C60⋅−

A systematic screening study of the exohedral reactivity of the reduced fullerenes (fullerenides) C₆₀²⁻ and C₆₀^⋅− is reported. These doubly and singly negatively charged carbon cages were prepared by two-fold reduction of C₆₀ with potassium, leading to K₂C₆₀, or by in situ monoreduction with the radical anion of benzonitrile PhCN^⋅−, respectively. Several series of electrophiles, including geminal and distant dihalides, benzyl bromides, and diazonium compounds, were employed as addition partners. In general, the investigated bromides proved to be the most suitable reaction partners. A series of fullerene adducts and cycloadducts involving either 1,2- or 1,4-addition patterns, depending on the precise architecture and the steric demand of the addends, were synthesized and fully characterized. Some of the reaction products are unprecedented and inaccessible forms of neutral C₆₀. The fullerenide chemistry presented here closely resembles related reactions of graphenides and carbon nanotubides, which are the most powerful methods for the functionalization of these macromolecular forms of synthetic carbon allotropes (SCAs). Activation of C₆₀ by negative charging represents a little explored concept of fullerene chemistry, providing both new insights of fullerene reactivity itself and new types of exohedral derivatives.     

Methanofullerene Molecular Scaffolding: Towards C60-substituted poly(triacetylenes) and expanded radialenes,preparation of a C60–C70 hybrid derivative,and a novel macrocyclization reaction

The synthesis of (E)-hex-3-ene-l, 5-diynes and 3-methylidenepenta-1, 4-diynes with pendant methano[60]-fullerene moieties as precursors to C₆₀-substituted poly(triacetylenes) (PTAs, Fig. 1) and expanded radialenes (Fig. 2) is described. The Bingel reaction of diethyl (E)-2, 3-dialkynylbut-2-ene-1, 4-diyl bis(2-bromopropane-dioates) 5 and 6 with two C₆₀ molecules (Scheme 2) afforded the monomeric, silyl-protected PTA precursors 9 and 10 which, however, could not be effectively desilylated (Scheme 4). Also formed during the synthesis of 9 and 10 , as well as during the reaction of C₆₀ with thedesilylated analogue 16 (Scheme 5 ), were the macrocyclic products 11, 12 , and 17 , respectively, resulting from double Bingel addition to one C-sphere. Rigorous analysis revealed that this novel macrocyclization reaction proceeds with complete regio- and diastereoselectivity. The second approach to a suitable PTA monomer attempted N, N′-dicyclohexylcarbodiimide(DCC)-mediated esterification of (E)-2, 3-diethynylbut-2-ene-l, 4-diol ( 18 , Scheme 6) with mono-esterified methanofullerene-dicarboxylic acid 23 ; however, this synthesis yielded only the corresponding decarboxylated methanofullerene-carboxylic ester 27 (Scheme 7). To prevent decarboxylation, a spacer was inserted between the reacting carboxylic-acid moiety and the methane C-atom in carboxymethyl ethyl 1, 2-methano[60]fullerene-61, 61-dicarboxylate ( 28 , Scheme 8), and DCC-mediated esterification with diol 18 afforded PTA monomer 32 in good yield. The formation of a suitable monomeric precursor 38 to C₆₀-substituted expanded radialenes was achieved in 5 steps starting from dihydroxyacetone (Schemes 9 and 10), with the final step consisting of the DCC-mediated esterification of 28 with 2-[1-ethynyl(prop-2-ynylidene)]propane-1, 3-diol ( 33 ). The first mixed C₆₀-C₇₀ fullerene derivative 49 , consisting of two methano[60]fullerenes attached to a methano[70]fullerene, was also prepared and fully characterized (Scheme 13). The C_s-symmetrical hybrid compound was obtained by DCC-mediated esterification of bis[2-(2-hydroxy-ethoxy)ethyl] 1, 2-methano[70]fullerene-71, 71-dicarboxylate ( 46 ) with an excess of the C₆₀-carboxylic acid 28 . The presence of two different fullerenes in the same molecule was reflected by its UV/VIS spectrum, which displayed the characteristic absorption bands of both the C₇₀ and C₆₀ mono-adducts, but at the same time indicated no electronic interaction between the different fullerene moieties. Cyclic voltammetry showed two reversible reduction steps for 49 , and comparison with the corresponding C₇₀ and C₆₀ mono-adducts 46 and 30 indicated that the three fullerenes in the composite fullerene compound behave as independent redox centers.     

Selective reduction of fullerene C60 by metals in neutral and alkaline media. Interaction of C60 with KOH

The reduction of fullerene C₆₀ by Zn and Mg in DMF was studied both in the presence and absence of KOH. Fullerene C₆₀ was reduced in these systems to form the C₆₀ ^n– (n = 1, 2, and 3) anions. The anions were detected by optical and ESR spectroscopies. It was found that Mg reduced C₆₀ to the monoanion, Mg/KOH and Zn reduced C₆₀ to the dianion, and Zn/KOH reduced C₆₀ to the trianion. Like KCN, potassium hydroxide adds to fullerene upon interaction with C₆₀ in DMF. The reaction of C₆₀ with KOH in benzonitrile was accompanied by the generation of the fullerene monoanion. A possible mechanism of the formation of fullerene monoanions in the presence of KOH is discussed. The degradation of the C₆₀ ^n– anions in air was studied.     

Regulation of Glucose Oxidase Activity through Interaction with Fullerene Derivatives

The 2‐(hydroxymethyl)pyridine modified C₆₀ (PY‐C₆₀) and methoxydiglycol modified C₆₀ (MDG‐C₆₀) are synthesized using Bingel‐Hirsch reaction and characterized by nuclear magnetic resonance (NMR) and mass spectra. PY‐C₆₀ and MDG‐C₆₀ can bind to glucose oxidase (GOx) and quench the fluorescence of tryptophan (Trp) residue in GOx through static mechanism. The conformation of GOx is disturbed after formation of complex with these fullerene derivatives. Kinetic analysis indicates that PY‐C₆₀ and MDG‐C₆₀ may affect the catalytic activity of GOx with a partial mixed‐type inhibition mechanism. In the plasma glucose concentration range (3.6–5.2 mmol·L^?1), PY‐C₆₀ may significantly accelerate the catalytic velocity of GOx, however, MDG‐C₆₀ exerts almost no obvious change to the initial velocity of GOx, suggesting that elaborate design of molecular structure of fullerene derivative is very important for regulating the biological activity of fullerene‐enzyme complex.     

Quantum chemical calculations of the molecular structures of hybrid amino acid derivatives of fullerene C60

The stereoselectivity of the formation of hybrid amino acid derivatives of fullerene (AADF) C₆₀ was studied. The energies of the model addition reactions C₆₀ + n C₂H₆ ? Me _n -C₆₀-Me _n (1) and C₆₀ + n EtNC₄H₇Me ? Et _n -C₆₀-(NC₄H₇Me) _n (2) (n = 1–3) were calculated by the DFT method B3LYP/6-31G*. The most stable products of reaction (1) are hexamethylated fullerene derivatives in which five Me groups are arranged in the form of a regular pentagon. Among the AADF obtained by reaction (2), 1,4-disubstituted fullerene isomers are most stable. The molecular structures of such isomers were calculated for six biologically active hybrid AADF; the solvent contact areas of these molecules were evaluated.     

Effect and Mechanism of a New Photodynamic Therapy with Glycoconjugated Fullerene

When irradiated, fullerene efficiently generates reactive oxygen species (ROS) and is an attractive photosensitizer for photodynamic therapy (PDT). Ideally, photosensitizers for PDT should be water-soluble and tumor-specific. Because cancer cells endocytose glucose more effectively than normal cells, the characteristics of fullerene as a photosensitizer were improved by combining it with glucose. The cytotoxicity of PDT was studied in several cancer cell lines cultured with C₆₀-(Glc)1 (d -glucose residue pendant fullerene) and C₆₀-(6Glc)1 (a maltohexaose residue pendant fullerene) subsequently irradiated with UVA₁. PDT alone induced significant cytotoxicity. In contrast, PDT with the glycoconjugated fullerene exhibited no significant cytotoxicity against normal fibroblasts, indicating that PDT with these compounds targeted cancer cells. To investigate whether the effects of PDT with glycoconjugated fullerene were because of the generation of singlet oxygen (¹O₂), NaN₃ was added to cancer cells during irradiation. NaN₃ extensively blocked PDT-induced apoptosis, suggesting that PDT-induced cell death was a result of the generation of ¹O₂. Finally, to investigate the effect of PDT in vivo, melanoma-bearing mice were injected intratumorally with C₆₀-(Glc)1 and irradiated with UVA₁. PDT with C₆₀-(Glc)1 suppressed tumor growth. These findings indicate that PDT with glycoconjugated fullerene exhibits tumor-specific cytotoxicity both in vivo and in vitro via the induction of ¹O₂.     

Synthesis of [60]fullerene-functionalized rotaxanes

Synthesis of [60]fullerene (C₆₀)-functionalized rotaxanes via Diels-Alder reactions with C₆₀ is described. Diels-Alder reaction of C₆₀ and sulfolene moiety as masked diene attached on the wheels of rotaxanes results in high yields of C₆₀ incorporation. Rotaxanes are prepared by tin-catalyzed urethane-forming end-capping reaction with isocyanate of pseudorotaxane having the wheel carrying C₆₀ functionality as introduced by the Diels-Alder reaction. The Diels-Alder reaction was accomplished as end-capping reaction between C₆₀ and pseudorotaxane bearing sultine moiety as masked diene on the axle terminal. A variety of C₆₀-containing [2]rotaxanes was prepared in moderate to good yields by these Diels-Alder protocols.     

Electronic, Energetic, and Geometric Properties of Methylene-Functionalized C60

Chemical functionalization of C₆₀ fullerene with one to six carbene (CH₂) molecule(s) has been investigated using density functional theory. We have found that the reaction is regioselective so that a CH₂ molecule prefers to be adsorbed atop a C–C bond which is shared between two hexagonal rings of the C₆₀, releasing energy of ?3.95 eV. Singly occupied molecular orbital (SOMO) of the CH₂ interacts with LUMO of the C₆₀ via a [2 + 1] cycloaddition reaction. Energy of the reaction and work function of the system are decreased by increasing the number of adsorbed CH₂ molecules. The HOMO/LUMO energy gap of C₆₀ is slightly changed and the electron emission from its surface is facilitated upon the functionalization.     

单加成环丙烷富勒烯膦酸酯衍生物的合成与电化学性能

在Mn(OAc)₃•2H₂O催化下, C₆₀分别和亚甲基二膦酸四乙酯、氰基亚甲基膦酸二乙酯或乙氧羰基亚甲基膦酸二乙酯在氯苯中回流, 生成3个单加成环丙烷富勒烯膦酸衍生物C₆₀C(R)PO(OEt)₂ [1, R＝PO(OEt)₂; 2, R＝COOEt; 3, R＝CN]. 与以前报道的Bingel反应法相比, 该方法副产物少并且缩短了反应时间. 采用循环伏安法发现1, 2的还原电位相对于C₆₀发生负移, 而3的还原电位相对于C₆₀却正移40 mV, 表明引入象氰基一样具有很强吸电子能力的取代基团, 可以改善富勒烯球的电化学性能, 合成电子接受能力较强的富勒烯衍生物.     

Interaction of fullerene C60 with allylbenzene and allyl chloride

The reaction between allyl compounds and fullerene C₆₀ has been investigated via dilatometry under the conditions of free-radical polymerization. It has been shown that the rate of a variation in the volume of the reaction mixture plotted versus the concentration of fullerene C₆₀ is described by a curve with a minimum. It has been established that, in the presence of fullerene and the allyl monomer, the polymerization of methyl methacrylate proceeds without any induction period. It has been concluded that allyl radicals interact with fullerene C₆₀.     

Revisit to the reaction of [60]fullerene with nitrile ylides generated from imidoyl chlorides and triethylamine

The reaction of [60]fullerene (C₆₀) with nitrile ylides generated from N-benzyl-4-nitrobenzimidoyl chloride/N-(4-chlorobenzyl)-4-nitrobenzimidoyl chloride and triethylamine gave only isomeric monoadducts of C₆₀ with [6,6]-closed structure. No [5,6]-open adduct of C₆₀ could be identified from these reactions. The previously reported [5,6]-open product of C₆₀ should be reassigned as a [6,6]-closed product.     

Self‐Assembly of Fullerene‐Based Janus Particles in Solution: Effects of Molecular Architecture and Solvent

Two molecular Janus particles based on amphiphilic [60]fullerene (C₆₀) derivatives were designed and synthesized by using the regioselective Bingel–Hirsh reaction and the click reaction. These particles contain carboxylic acid functional groups, a hydrophilic fullerene (AC₆₀), and a hydrophobic C₆₀ in different ratios and have distinct molecular architectures: 1:1 (AC₆₀–C₆₀) and 1:2 (AC₆₀–2C₆₀). These molecular Janus particles can self‐assemble in solution to form aggregates with various types of micellar morphology. Whereas vesicular morphology was observed for both AC₆₀–C₆₀ and AC₆₀–2C₆₀ in tetrahydrofuran, in a mixture of N,N‐dimethylformamide (DMF)/water, spherical micelles and cylindrical micelles were observed for AC₆₀–C₆₀ and AC₆₀–2C₆₀, respectively. A mechanism of formation was tentatively proposed based on the effects of molecular architecture and solvent polarity on self‐assembly.     

Effect of the medium on the reactivity of fullerene N60 with respect to the peroxide radicals RO2 ·. Chemiluminescence in the C60—AIBN—O2—C2H5Ph—PhH system

Chemiluminescence (CL), HLPC, and volumetry were used to demonstrate that fullerene N₆₀ exerts no inhibiting effect on the liquid-phase chain oxidation of hydrocarbons. Peroxide radicals RO₂ · do not add to N₆₀ in hydrocarbons with active C—H bond, because the reaction is suppressed by the competing addition of RO₂ · to the hydrocarbon. The addition of RO₂ · radicals to N₆₀ does occur in benzene (a solvent with strong C—H bonds) in the presence of low concentrations of the hydrocarbon oxidized. Fullerene N₆₀ is found to exhibit a new type of liquid_phase CL, which is presumably generated upon thermal decomposition of fullerene peroxides formed by adding peroxy radicals to fullerene in the C₆₀—AIBN—O₂—C₂H₅Ph—PhH system. The CL spectrum exhibits long-wavelength maxima at 645 and 685 nm. The supposed CL emitters are keto derivatives of fullerene N₆₀.     

Synthesis of a Fullerene Derivative of Benzo[18]crown-6 by Diels-Alder Reaction: Complexation Ability,Amphiphilic Properties,and X-Ray Crystal Structure of a Dimethoxy-1,9-(methano[1,2]benzenomethano)fullerene[60] Benzene Clathrate

A fullerene derivative 1 of benzo[18]crown-6 was obtained by Diels-Alder addition of fullerene[60](C₆₀) to the ortho-quinodimethane prepared in situ from 4,5-bis(bromomethyl)benzo[18]crown-6 ( 3 ) with Bu₄NI in toluene. Extraction experiments show that the complexation of K⁺ ions strongly increases the solubility of 1 in protic solvents like MeOH. Using Langmuir-Blodgett techniques, monolayers of the highly amphiphilic fullerene-derived crown ether 1 and its K⁺ ion complex were prepared. An X-ray crystal structure was obtained from a benzene clathrate of comparison compound 2 , synthesized by Diels-Alder reaction of C₆₀ with the ortho-quinodimethane derived from 1,2-bis(bromomethyl)-4,5-dimethoxybenzene ( 4 ). Both the fullerene molecule 2 and the benzene molecule are fully ordered in a crystal packing which is stabilized by intermolecular van-der-Waals contacts between the benzene ring and the C-spheres, intermolecular C…?C contacts between the C₆₀ moieties, and intermolecular O…?C contacts between the O-atoms of the veratrole moieties and fullerene C-atoms.     

Reaction of fullerene C60 with 2-azido-4,6-diphenylpyrimidine

The first representative of the pyrimidine-substituted [60]fullereno[1,2-b]aziridines was synthesized by the reaction of fullerene C₆₀ with 2-azido-4,6-diphenylpyrimidine. 2-(Azahomo[60]fullereno)-4,6-diphenylpyrimidine was found to be formed as a by-product. The electrochemical properties of the adducts were studied.