Efficient synthesis of C2v-symmetrical pentakisadducts of C60 as versatile building blocks for fullerene architectures that involve a mixed octahedral addition pattern

We report here on the selective synthesis of fullerene pentakisadducts 3 with an incomplete octahedral addition pattern by means of mixed [5:1]hexakisadducts 1 that involve an isoxazoline moiety as a protection group. The isoxazoline addend can be cleanly cleaved by irradiation with light. By using this protection-deprotection strategy, a variety of fullerene pentakisadducts 3 were synthesized in 29-44% overall yield without the need of HPLC purification. This novel photolytic deprotection of 1 can be explained by an initial electron transfer that leads to a biradical, which can easily eliminate the isoxazoline added. The very efficient and straightforward syntheses of the bisfullerene 4 and the globular hexakisadduct 7, each of which involves mixed octahedral addition patterns, clearly demonstrate the advantage of fullerene pentakisadducts 3 as suitable precursors for the construction of highly functional and complex [5:1]hexakisadduct architectures. Complete structural characterization of all new compounds was carried out by MALDI mass spectrometry, UV/Vis, FTIR, (1)H NMR and (13)C NMR spectroscopy, as well as X-ray diffraction.     

Efficient Synthesis of C2v‐Symmetrical Pentakisadducts of C60 as Versatile Building Blocks for Fullerene Architectures that Involve a Mixed Octahedral Addition Pattern

We report here on the selective synthesis of fullerene pentakisadducts 3 with an incomplete octahedral addition pattern by means of mixed [5:1]hexakisadducts 1 that involve an isoxazoline moiety as a protection group. The isoxazoline addend can be cleanly cleaved by irradiation with light. By using this protection–deprotection strategy, a variety of fullerene pentakisadducts 3 were synthesized in 29–44 % overall yield without the need of HPLC purification. This novel photolytic deprotection of 1 can be explained by an initial electron transfer that leads to a biradical, which can easily eliminate the isoxazoline added. The very efficient and straightforward syntheses of the bisfullerene 4 and the globular hexakisadduct 7 , each of which involves mixed octahedral addition patterns, clearly demonstrate the advantage of fullerene pentakisadducts 3 as suitable precursors for the construction of highly functional and complex [5:1]hexakisadduct architectures. Complete structural characterization of all new compounds was carried out by MALDI mass spectrometry, UV/Vis, FTIR, ¹H NMR and ¹³C NMR spectroscopy, as well as X‐ray diffraction.     

Effect of nature of organic solvent on the absorption spectrum of C60 fullerene

Absorption spectrums of C₆₀ fullerene in 10 various organic solvents in the range of 300–620 nm was studied. In all the solvents the C₆₀ fullerene has four absorption maxima in the range under study. When an aromatic solvent has an ionization potential of 8.1 eV or lower a new additional absorption band appears in the absorption spectrum of C₆₀ fullerene, caused by the formation of a charge-transfer complex (CTC) of the solvent and C₆₀ fullerene.     

Reorganization of hydrogen-bonded block copolymer complexes

Poly(styrene)-block-poly(4-vinylpyridine) (PS-b-P4VP) copolymers and poly(acrylic acid) (PAA) have been mixed in organic solvents. Complexation via hydrogen bonding occurs between the P4VP and PAA blocks. Those insoluble complexes aggregate to form the core of micelles surrounded by a corona of PS chains. Reorganization of these structures occurs upon addition of acidic or basic water, which results in the breaking of the hydrogen bonds between the P4VP and PAA blocks. After transfer of the initial complexes in acidic water, micelles consisting of a PS core and a protonated P4VP corona are observed. In basic water, well-defined nanoparticles formed by the PS-b-P4VP copolymers are obtained. It is demonstrated that these nanoparticles are stabilized by the negatively charged PAA chains. Finally, thermally induced disintegration of the micelles is investigated in organic solvents.     

Preparation of fullerene С<Subscript>60</Subscript> dispersions in water

Stable colloidal dispersions of fullerene С₆₀ in water free of organic solvents have been obtained. The addition of a С₆₀ solution to a water–acetone mixture has been shown to cause a solvatochromic effect.     

Stable colloidal dispersions of fullerenes in polar organic solvents.

Colloidal dispersions of C60 and C70 were prepared by simply mixing a fullerene solution in a good solvent with a poor polar organic solvent for fullerenes. The process was very easy and fast and the formation of particles with average diameter in the colloidal range was detected immediately after the components were mixed. The formation and the properties of the fullerene particles were studied mainly with dynamic light scattering and high-resolution transmission electron microscopy. The most interesting findings are the long-term colloid stability of the samples in the absence of any stabilizers, the relatively narrow size distribution, and the different average sizes of the particles formed by C60, C70, and their mixtures. The influence of various factors such as fullerene concentration, mixing procedure, solvent properties, and C60/C70 ratio was investigated. It is shown that the smaller particles are formed when the total fullerene concentration in the good solvent is decreased and that the fullerene particles have crystalline structure. The measured negative values for the electrophoretic mobility of the particles suggest that fullerene dispersions in polar organic solvents are stabilized by repulsive electrostatic interactions.     

Preparation of Aqueous Colloidal Dispersion of C<Subscript>60</Subscript> Fullerene

A method for preparing aqueous colloidal dispersions of C₆₀ fullerene free of organic solvents is proposed. The size of dispersed particles is determined using the turbidity spectra. A solvatochromic effect is observed upon the addition of a C₆₀ solution in toluene to a water-acetone mixture.__________Translated from Kolloidnyi Zhurnal, Vol. 67, No. 4, 2005, pp. 575–576.Original Russian Text Copyright © 2005 by Tseluikin, Tolstova, Gun’kin, Pankst’yanov.     

Hydroxyfullerene as a novel coating for solid-phase microextraction fiber with sol-gel technology

Hydroxyfullerene (fullerol) as a novel coating for solid-phase microextraction (SPME) fiber was first prepared by a sol-gel technology. The coating procedure involving sol solution composition and conditioning process was presented. A fullerene polysiloxane surface-bonded porous coating on the fused-silica fiber surface was obtained and confirmed by IR spectra and scanning electron microscopy. The coating has stable performance at high temperature (even to 360 degrees C) and solvents (organic and inorganic) because of the properties of fullerene and the chemical binding between the coating and the fiber surface. The extraction properties of the new coatings to less volatile organic compounds, such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons and polar aromatic amines were investigated using headspace SPME coupled with GC-electron-capture detection and GC-flame ionization detection. In addition, compared with commercial SPME stationary phases, the new coatings showed higher sensitivity, faster velocities of mass transfer for aromatic compound, and possessed planarity molecular recognition for PCBs. Moreover, this fiber was firm, inexpensive, durable and can be prepared simply. The fiber-to-fiber reproducibility was very good.     

新型富勒烯α-氨基酸的合成及其纳米颗粒水悬液的制备

通过1,3-偶极环加成反应合成中间体N-取代的3,4-富勒烯吡咯烷, 利用α-氨基与α-羧基均被保护的天冬氨酸或谷氨酸的非α-羧基与中间体N-取代的3,4-富勒烯吡咯烷衍生物的活化羟基进行缩合反应, 产物脱保护后得到了2种新的α-富勒烯氨基酸: 富勒烯天冬氨酸和富勒烯谷氨酸. 采用MALDI-TOF质谱、红外光谱、紫外-可见光谱和1H NMR 等方法对它们进行了结构表征. 采用有机溶剂交换法, 制备富勒烯氨基酸纳米颗粒水悬液, 并进行了电镜和表面zeta-电位分析, 结果表明, 此水悬液体系稳定, 颗粒形态大小均一, 在生物医学领域中具有潜在的应用前景.     

Chemically modified fullerene derivatives as photosensitizers in photodynamic therapy: A first‐principles study

The first‐principles density functional theory (DFT) and its time‐dependent approach (TD‐DFT) are used to characterize the electronic structures and optical spectra properties of five chemically modified fullerenes. It is revealed that the metal fullerene derivatives possess not only stronger absorption bands in visible light regions than organically modified fullerene but also the large energy gaps (ΔE_S–T > 0.98 eV) between the singlet ground state and the triplet state, which imply their significant aspect of potential candidates as a photosensitizer. We have found that a new metal‐containing bisfullerene complexes (Pt(C₆₀)₂), with the extended conjugated π‐electrons, much degenerate orbitals and a uniform electrostatic potential surface, behave more pre‐eminent photosensitizing properties than other examined fullerene derivatives. © 2012 Wiley Periodicals, Inc.     

Electrochemical charging of a fullerene-functionalized self-assembled monolayer on au(111)

A fullerene derivative 10 with a terminal thiol group dissolves easily in common organic solvents and forms a densely packed self-assembled monolayer on gold surfaces. The functionalization of C(60) is based on the 1,3-dipolar cycloaddition of the azomethine ylide generated in situ from the corresponding aldehyde and N-methylglycine. The monolayers were characterized by grazing angle reflectance FTIR spectroscopy, scan tunneling microscopy, and cyclic voltammetry. The cyclic voltammogram of a SAM of 10 showed two well-resolved reversible cathodic waves corresponding to the first two one-electron reductions of the fullerene fragment.     

Preparing Aqueous Dispersions of C60 Fullerene

Russian Journal of Physical Chemistry A - Stable dispersions of C60 fullerene in water are prepared that contain no organic solvents. A solvatochromic effect is observed upon adding a solution of...     

Polymer Donors for High‐Performance Non‐Fullerene Organic Solar Cells

Over the past few years, non‐fullerene organic solar cells have been a focus of research and their power conversion efficiencies have been improved dramatically from about 6 % to over 14 %. In addition to innovations in non‐fullerene acceptors, the ongoing development of polymer donors has contributed significantly to the rapid progress of non‐fullerene organic solar cell performance. This Minireview highlights the polymer donors that enable high‐performance non‐fullerene organic solar cells. We show the impressive photovoltaic devices results achieved by some of important classes of conjugated polymer systems in non‐fullerene organic solar cells. We discuss the molecular design strategies as far as developing matching polymer donors for non‐fullerene acceptors. We conclude with a brief summary and outlook for advances in donor polymers required for commercialization.     

Ring-opening metathesis polymerization (ROMP) of fullerene-containing monomers in the presence of a first-generation Grubbs catalyst

New norbornene-type monomers containing covalently bound C60 fullerene have been obtained. In the presence of the 1st generation Grubbs catalyst [(PCy₃)₂Cl₂RuCHPh] (Cy is cyclohexyl), these monomers smoothly undergo homopolymerization and copolymerization with parent fullerene-free monomers. The homopolymers are insoluble in common organic solvents, while the copolymers obtained at different molar ratios to their fullerene-free analogues are very soluble in organic solvents and can be suitable for the preparation of thin films.     

叠氮烷烃环加成反应合成C60衍生物及其聚合物太阳电池的特性

通过烷基叠氮化合物与C₆₀的环加成反应合成了一系列以长链烷烃取代C₆₀的亚氨基衍生物,研究了其紫外-可见光吸收特性及电化学性质,并考察了由这些材料和聚[2-甲氧基-5-(2-乙基己氧基)-1,4-对苯乙炔](MEH-PPV)制成的聚合物光电池的性能.这类器件的能量转换效率介于0.13～0.37之间,随着所接烷基链的增长和支链数目的增加,衍生物的溶解度逐步提高,器件的短路电流随着衍生物溶解度的提高而增加,最高可达到1.77mA/cm²,这类器件具有较极大的光暗比,有可能首先在传感器方面得到应用.     

Demonstration of a chemical transformation inside a fullerene. The reversible conversion of the allotropes of H2@C60

The interconversion of the two allotropes of the hydrogen molecule (para-H2 and ortho-H2) incarcerated inside the fullerene C60 is reported (oH2@C60 and pH2@C60, respectively). For conversion, oH2@C60 was adsorbed at the external surface of the zeolite NaY and immersed into liquid oxygen at 77 K. Equilibrium was reached in less than 0.5 h. Rapid removal of oxygen provides a sample of enriched pH2@C60 that is stable for many days in the absence of paramagnetic catalysts (half-life approximately 15 days). Enriched pH2@C60 is nonvolatile and soluble in organic solvents. At room temperature in the presence of a paramagnetic catalyst (dissolved O2 or the nitroxide Tempo) a slow back conversion into oH2@C60 was observed by 1H NMR. A bimolecular rate constant for conversion of pH2@C60 to oH2@C60 using Tempo of kTempo approximately 4 x 10-5 M-1 s-1 was observed, which is approximately 3 orders of magnitudes slower than that for dissolved pH2 in organic solvents which is not protected by the C60 shell.     

An efficient route to the synthesis of symmetric and asymmetric diastereomerically pure fullerene triads

A new synthetic route based on the stepwise functionalisation of fullerene cages allows the facile formation of linear, diastereomerically pure triads incorporating two different fullerene cages linked by an organic spacer group. The critical coupling step of two fullerene cages via activation by N,N′-dicyclohexylcarbodiimide was systematically investigated to reveal that the yield of the coupling is maximised in o-dichlorobenzene at high concentrations of the reactant fullerene nucleophile, while in more polar solvents or at lower concentrations of reactants the formation of unwanted side-products (such as guanidine-, N-acylurea- and anhydride-functionalised fullerenes) is favoured. The resultant triads possess an atypically good solubility for this class of compound, which enabled full detailed characterisation by ¹H and ¹³C NMR, IR and UV–vis spectroscopies and by MALDI-TOF mass spectrometry.     

Optical Properties and Photo‐Oxidation of Tetraphenylethene‐Based Fluorophores

We report the optical properties of tetraphenylethene (TPE) and other TPE derivatives functionalised with an octyl group (TPE‐OCT) and polyethyleneglycol group (TPE‐PEG) in the side chain. We compared TPE‐OCT and TPE‐PEG with TPE in both organic solvents and under aqueous conditions. All materials exhibit aggregation‐induced emission, however, uncommonly, TPE‐PEG seems to aggregate in aqueous solution with enhanced photoluminescence quantum efficiency (PLQE) relative to that in organic solvents. All three materials can be photo‐oxidised in solution to their diphenylphenanthrene derivative by irradiation with UV light (at both ≈1 and ≈5 mW cm^?2), with a subsequent enhancement in PL efficiency. The electron‐donating ether group increases the rate of oxidation relative to bare TPE and also photo‐oxidation was shown to be solvent and concentration dependent. Finally, photo‐oxidation was also demonstrated in the aggregate state.     

Low-Cost Synthesis of Fullerene Derivatives

Refined mixed fullerenes were used as a reagent in known organic reactions instead of the pure fullerene C₆₀ with aim to find an alternative, low-cost method for the synthesis of fullerene derivatives potentially exhibiting photoconductive properties. The isolation of C₆₀ or C₇₀ in clean form without admixtures requires the use of large quantities of toluene or other nonpolar solvents, polluting the environment and multiplying the production cost. 1,3-Dipolar cycloaddition of azomethine ylide to fullerite was chosen because this reaction is one of the most widely used for fullerene functionalization, producing material possibly presenting photoinducing behavior. The data showed that the use of the cheaper mixed fullerenes instead of pure C₆₀ leads to the isolation of the same expected products with similar yields. The photoelectric properties of mixed fullerenes and their organic derivatives were also examined. A slightly semiconductive behavior was confirmed as well as a noticeable photoresponse.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Self‐Assembled Aggregates and Molecular Bilayer Films of a Double‐Chain Fullerene Lipid: Structure and Electrochemistry

The self‐aggregation behavior of C₆₀ fullerenes that bear two octadecyl chains (lipid 1 ) as well as the structures and electrochemical properties of cast films of 1 are described. We also examined the self‐aggregation behavior in organic solvents of three previously reported compounds: C₆₀ with three each of hexadecyl (lipid 2 ), tetradecyl (lipid 3 ), or dodecyl (lipid 4 ) chains. The fullerene lipids in alcohols spontaneously formed spherical aggregates, whose diameters are related to the alkyl‐chain lengths, concentrations of the fullerene lipids, and the solvent polarity. The morphologies of the aggregates showed temperature dependence. Cast films of 1 formed multimolecular bilayer structures that undergo a phase transition typical of lipid bilayer membranes. The electrochemistry of cast films of 1 on an electrode in aqueous medium exhibits temperature dependence.