Compound based on star-shaped oligophenylene and fullerene C60

Compound based on star-shaped oligophenylene and modified with l-valine fullerene C₆₀ has been synthesized and characterized. For characterization, X-ray photoelectron spectroscopy was used.     

Production of monoclonal antibodies against fullerene C60 and development of a fullerene enzyme immunoassay

The aim of the present study was to produce monoclonal anti-fullerene C(60) antibodies and to develop the enzyme immunoassay for the detection in the first use of free fullerene C(60) both in solutions and in multicomponent biological probes. The immunization of mice with the conjugate of fullerene C(60) carboxylic derivative with thyroglobulin synthesized by carbodiimide activation led to the production of eight clones of anti-fullerene antibodies. The specificity of the antibody-fullerene binding was confirmed. Indirect competitive enzyme-linked immunosorbent assay (ELISA) was developed for the determination of water-soluble protein-conjugated fullerene, the fullerene aminocaproic acid, fullerenol and for pristine fullerene in solution. To solubilize extremely hydrophobic free fullerene C(60) a specially selected water-organic mixture compatible with immunoassay was proposed. The detection limit of free fullerene C(60) in solution was 2 μg L(-1). Fullerene C(60) was also detected by ELISA in organ homogenates of rats intraperitoneally or intragastrically administered with fullerene. To reduce the influence of biomatrices on the assay results a technique was developed for the biological sample pretreatment by the extraction of C(60) from bioprobe by toluene followed by the evaporation of toluene and dissolution of the fullerene-containing extract in the selected water-organic media. The ELISA procedure in the first use allowed the detection of fullerene C(60) in different tissues.     

Potential energy surface and orientational disorder in solid fullerene C60

The polymorphism and molecular disorder in crystalline C₆₀ have been studied by modelling the optimum packing of fullerene molecules by the atom-atomic potential method. The study includes the calculation of minima and saddle points of the potential energy surface with sorting out of the most common space symmetry groups. Two models of intermolecular potential for C₆₀ have been checked, one of which assumes effective charges at the centers of C-C bonds. It has been found that the calculated barrier of reorientations is much lower in the case where the concerted character of rotations of different molecules is taken into account. The model of orientational disorder in the face-centered cubic phase is suggested, which is based on consideration of symmetrically arranged equivalent minima separated by low potential barriers.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1466–1469, August, 1995.The work was financially supported by the Russian Foundation for Basic Research (Project No. 94-03-08895).     

Acid-base isomerization of hybrid molecules based on fullerene C60 and spiropyrans

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Theoretical studies of C60/C70 fullerene derivatives: C60O and C70O

A semiempirical (AM1) calculation on the structures and stabilities of isomers of the fullerene derivatives C₆₀O and C₇₀O is carried out. The ozonolysis reaction mechanism and the thermodynamics of the compounds are studied. The two isomers of C₆₀O (56 bond and 66 bond) formed by an oxygen atom bridging across a C-C bond have an epoxide-like or an annulene-like structure. According to the ozonolysis reaction mechanism and kinetic factor analysis, the possible products of this ozonolysis reaction are C₆₀O with oxygen bridging over the 66 bond (C_2v) as an epoxide-like isomer and that with oxygen bridging over the 56 bond (C_s) as an annulene-like isomer. Further, the sixteen isomers of C₇₀O (both epoxide-like and annulene-like structures) have been studied with respect to the same reaction mechanism. The most possible product in this ozonolysis reaction contains oxygen bridging across in the upper part (66 bond in C₇₀O-2 or C₇₀O-4) as an epoxide-like structure. The other possible product is C₇₀O-8 (annulene-like structure), in which oxygen bridges across an broken equatorial CC bond in C₇₀ (D_5h). The vibrational frequency analysis and the electronic structure of the selected C₆₀O and C₇₀O isomers are generated for experimental characterisation. The experimental results indicate that C₆₀O and C₇₀O may decompose into the odd number fullerenes C₅₉ and C₆₉. We therefore studied the structures of C₅₉ and C₆₉ also.     

Electrochemical behavior of fullerene C60 and substituted fullerenes immobilized on an electrode surface

The effect of substituents with different donor capabilities, which are inserted into a molecule of fullerene C₆₀, on the kinetics and thermodynamics of redox conversions of fullerenes that are immobilized on an electrode, is studied for the first time. To this end, redox conversions that occur with rubbed-on films of fullerene and fulleropyrrolidines are studied using cyclic voltammetry in 0.5 M KCl/H₂O and a 0.1 M (C₄H₉)₄NBF₄/AN solution in acetonitrile. A hypothesis that the kinetics of redox conversions occurring with films of individual fullerenes is defined largely by changes in the structure of initial films in the process of their cathodic doping is used. The effect of the substituents is explained in the framework of this hypothesis by a transition from a dense crystalline structure of nonsubstituted fullerene C₆₀ to an amorphous structure of substituted fullerenes. It is demonstrated that the formal potentials corresponding to redox conversions of fullerenes in a solid cationic lipid matrix are defined by the energy of interaction of anions, which are products of reduction of fullerenes, with cations of the matrix. As a result of this interaction, the formal potentials of the process of cathodic doping shift to less negative values. It is established that the insertion of a donor substituent and increase in its donor capability amplify the energy of interaction of the fullerene anions with the lipid cations.     

Thermochemistry of C60 and C70 fullerene solvates

In an effort to improve understanding of dissolution behaviour of fullerenes and their simple chemical derivatives the binary systems of C₆₀, C₇₀ and the piperazine monoadduct of [60] fullerene C₆₀ N₂C₄H₈ with a series of aromatic solvents have been studied by means of DSC. In certain systems solid solvates have been found to be the thermodynamically stable phases relative to saturated solution at room temperature. Identified solid solvates were characterized by their compositions, temperatures and enthalpies of incongruent melting transitions. The regularities in thermodynamic stability of the solvated crystals have been discussed along with dissolution properties of fullerenes and the derivative. Certain correlations have been observed.     

Optically controlled field effect transistors based on photochromic spiropyran and fullerene C60 films

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A new surface-enhanced Raman scattering system for C60 fullerene: Silver nano-particles/C60/silver film

Surface-enhanced Raman scattering (SERS) spectrum of very good quality of “silver nano-particles/C60/silver film” system was reported for the first time by using the pyridine as a intermediate to connect and nest the C60 molecules to the gap of silver nano-particles and silver film. Experiment results show that the ternary system of “silver nano-particles/C60/silver film” is very effective and active. Not only was the number of vibrational modes greatly increased, especially some modes that were forbidden in Raman spectrum, but also were the significant Raman bands splitted as well as frequencies up and down shifted, respectively, arising from symmetry lowering and selection rule relaxing of C60 induced by the silver surface. Furthermore, the splitting of the Raman modes is consistent with the calculation based on group theory. The adsorption of C60 molecules is oriented on pentagons of C60 on the silver surface. It is difficult to separate the contributions of the electromagnetic and chemical mechanisms to the great enhancement of the Raman signal. On the one hand, the silver nanoparticles modified on the silver film play an important role in magnifying the surface local electric field near the silver surface through resonant surface plasmon excitation. On the other hand, charge transfer factor may not be neglected.     

Adsorption of ascorbic acid on the C60 fullerene

Adsorption of ascorbic acid (AsA) on C60 is investigated using classical molecular mechanics and density functional theory (DFT). Classical annealing was performed to explore the space of molecular configurations of ascorbic acid adsorbed on C60, searching for optimal geometries. From the structure with the smallest total energy, 10 initial configurations were prepared by applying rotations of 90 degrees about three orthogonal axes. Each one of these configurations was optimized using DFT (for both LDA and GGA exchange-correlation functionals), and an estimate of their total and adsorption energies was found. Different configurations have minimal adsorption energies (defined here as the total energy of the adsorbate minus the total energy of the separate molecules) from -0.54 to -0.10 eV, with distinct optimal distances between the AsA and C60 centers of mass. According to a Hirshfeld population analysis, AsA is, in general, an acceptor of electrons from C60. Our results demonstrate the feasibility of noncovalent functionalization of C60 with AsA and provide minimal energy values for the several different configurations investigated. These results should be considered in reactions as a possible way to prevent against the oxidative damage and toxicity of C60. The beneficial effects of using AsA-C60 includes its action when administered together with levodopa, against the neurotoxicity generated by levodopa isolated, which opens new strategies for the Parkinson's disease treatment.     

Non-covalent versus covalent donor-acceptor systems based on near-infrared absorbing azulenocyanines and C60 fullerene derivatives

A novel supramolecular electron donor-acceptor hybrid (2·1) and an electron donor-acceptor conjugate (3), both exhibiting a remarkably shifted Q band in the NIR region of the solar spectrum, were prepared. Irradiation of the supramolecular ensemble 2·1 within the visible range leads to a nanosecond lived radical-ion pair state Zn-azulenocyanine˙(+)-C(60)˙(-).     

Preparation and properties of sorbents based on silica gel containing covalently linked fullerene C60

Sorbents containing 10–12 % fullerene C₆₀ were prepared by the reaction of C₆₀ with -aminopropylsilica gel. C₆₀-Silica gel possesses good chromatographic properties for the separation of aromatic, nitro, and heterocyclic compounds in the regimes of normal and reversed-phase HPLC.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 814–816, April, 1996.     

Solvent Effects on the Solubility of C60 fullerene

The solubility of C₆₀ fullerene in organic liquids is not directly related to any of their physicohemical characteristics, but can be quantitatively described by linear multiparameter equations. The solubility increases with increasing solvent polarizability and decreases with increasing solvent polarity and cohesive energy density. Various types of multiparameter equations proposed in the literature were compared to show that they all are suitable but Koppel-Palm's equation is preferred.     

Electrochemical biosensors based on enzymes immobilized in electropolymerized films

A review based on 135 references concerns the design and properties of electrochemical biosensors for 13 different substrates of enzymatic reactions. In the sensors discussed the enzymes are immobilized within or on the top of electropolymerized films, mostly of conducting polymers. Amperometric detection is most often used for internal electrochemical sensing.Dedicated to our late colleague Wojciech Matuszewski     

Continuous symmetry of C60 fullerene and its derivatives

Conventionally, the I(h) symmetry of fullerene C(60) is accepted, which is supported by numerous calculations. However, this conclusion results from the consideration of the molecule electron system, of its odd electrons in particular, in a closed-shell approximation without taking the electron spin into account. Passing to the open-shell approximation has led to both the energy and the symmetry lowering up to C(i). Seemingly contradicting to a high-symmetry pattern of experimental recording, particularly concerning the molecule electronic spectra, the finding is considered in this Article from the continuous symmetry viewpoint. Exploiting continuous symmetry measure and continuous symmetry level approaches, it was shown that formal C(i) symmetry of the molecule is by 99.99% I(h). A similar continuous symmetry analysis of the fullerene monoderivatives gives a reasonable explanation of a large variety of their optical spectra patterns within the framework of the same C(1) formal symmetry exhibiting a strong stability of the C(60) skeleton. TOC color pictures present chemical portrait of C(60) in terms of atomic chemical susceptibility (Sheka, E. Fullerenes: Nanochemistry, Nanomagnetism, Nanomedicine, Nanophotonics; CRC Press: Taylor and Francis Group, Boca Raton, 2011).     

Single crystal X-ray structure of tetrahedral C60F36: the most aromatic and distorted fullerene

Tetrahedral C60F36 is shown by its single-crystal X-ray structure to be the most aromatic (and distorted) fullerene derivative, having four planar hexagons with almost equal bond lengths, the average of which (1.373 A) is the same as in C60F18; one exceptionally long FC-CF bond (1.665 A) corresponds to the similarly long bond in C60F18 (a motif of T C60F36) and is likely to be the site of oxygen insertion in C60F36O.     

Microwave-assisted extraction of C60 and C70 from fullerene soot

Microwave-assisted extraction (MAE) was examined as an alternative to the traditional Soxhlet method of extracting C₆₀ and C₇₀ from fullerene soot. MAE of 0.20 g of fullerene soot with 95:5 toluene–acetonitrile yielded greater than 7.8 mg of C₆₀ and greater than 0.54 mg of C₇₀ in 4 min with no further increase in yield after 30 min of irradiation. By comparison, exhaustive Soxhlet extraction of the same size sample with the same solvent yielded 7.1 mg of C₆₀ and 0.58 mg of C₇₀ in 340 min. Reextraction by MAE of soot initially extracted by Soxhlet increased the yield of Soxhlet alone. Although MAE was limited to less than 0.5-g sample per extraction vessel, multiple samples were extracted with minimal increased extraction time and no reduction in the amount of material recovered.     

DFT studies on endohedral fullerene C@C60: C centers the C60 cage

Structural and electronic properties of C@C₆₀ were studied via Hartree–Fock self-consistent field (SCF) and density functional B3LYP levels of theory with the STO-3G, 6-31G(d) and 6-31G(d, p) basis sets. Both singlet and triplet were considered. The triplet structure with C on the center of the C₆₀ cage was proved to be global minimum on the C@C₆₀ molecular potential energy surface. The calculated HOMO-LUMO gaps as well as the electron affinity (EA) and the ionization potential (IP) were also presented as an indicator of the kinetic stability.     

Microcantilever biosensors based on conformational change of proteins

Microcantilevers (MCLs) hold a position as a cost-effective and highly sensitive sensor platform for medical diagnostics, environmental analysis and fast throughput analysis. MCLs are unique in that adsorption of analytes on the microcantilever (MCL) surface changes the surface characteristics of the MCL and results in bending of the MCL. Surface stress due to conformation change of proteins and other polymers has been a recent focus of MCL research. Since conformational changes in proteins can be produced through binding of anylates at specific receptor sites, MCLs that respond to conformational change induced surface stress are promising as transducers of chemical information and are ideal for developing microcantilever-based biosensors. The MCL can also potentially be used to investigate conformational change of proteins induced by non-binding events such as post-translational modification and changes in temperature or pH. This review will provide an overview of MCL biosensors based on conformational change of proteins bound to the MCL surface. The models include conformational change of proteins, proteins on membranes, enzymes, DNA and other polymers.