Complex Of C60 Fullerene Research Articles

Evaluation of the efficiency of intersystem crossing to a triplet state of fullerene in complexes with amino acids

The important photophysical process that determines the efficiency of photosensitizers is saturation of a triplet state by intersystem crossing during light absorption. In the present work, C60 fullerene complexes with amino acids glycine, lysine, methionine and threonine were studied as promising photosensitizers. All these complexes, for which the calculations were done, demonstrate high values of rate constants of transition to triplet states and a high probability of the ability to generate reactive oxygen species through excitation in the visible spectrum. The carboxyl groups of amino acids that are not involved in electronic excitation can be used as the component of specific DNA aptamers for conjugation to photoactive complexes for a tumor-targeting drug delivery system.

Mechanochemically-generated solid state complex of C60-fullerene with tetra-(5,7-diphenyl)calix[4]azulene, NMR, XRD and DFT studies

The synthesis of tetra-(5,7-diphenyl)calix[4]azulene via the reaction of 5,7-diphenylazulene with formaldehyde is described. Its solid-state supramolecular complexation with C60 produced by a grinding of the two components was evaluated by solid-state 13C-NMR spectroscopy and X-ray powder diffraction. Gas-phase DFT studies of possible structures are reported.

Complex of C60 Fullerene with Doxorubicin as a Promising Agent in Antitumor Therapy

The main aim of this work was to evaluate the effect of doxorubicin in complex with C60 fullerene (C60 + Dox) on the growth and metastasis of Lewis lung carcinoma in mice and to perform a primary screening of the potential mechanisms of C60 + Dox complex action. We found that volume of tumor from mice treated with the C60 + Dox complex was 1.4 times less than that in control untreated animals. The number of metastatic foci in lungs of animals treated with C60 + Dox complex was two times less than that in control untreated animals. Western blot analysis of tumor lysates revealed a significant decrease in the level of heat-shock protein 70 in animals treated with C60 + Dox complex. Moreover, the treatment of tumor-bearing mice was accompanied by the increase of cytotoxic activity of immune cells. Thus, the potential mechanisms of antitumor effect of C60 + Dox complex include both its direct action on tumor cells by inducing cell death and increasing of stress sensitivity and an immunomodulating effect. The obtained results provide a scientific basis for further application of C60 + Dox nanocomplexes as treatment agents in cancer chemotherapy.

Application of C60 Fullerene-Doxorubicin Complex for Tumor Cell Treatment In Vitro and In Vivo.

Development of nanocarriers for effective drug delivery to molecular targets in tumor cells is a real problem in modern pharmaceutical chemistry. In the present work we used pristine C60 fullerene as a platform for delivery of anticancer drug doxorubicin (Dox) to its biological targets. The formation of a complex of C60 fullerene with Dox (C60 + Dox) is described and physico-chemical characteristics of such complex are presented. It was found that Dox conjugation with C60 fullerene leads to 1.5-2-fold increase in Dox toxicity towards various human tumor cell lines, compared with such effect when the drug is used alone. Cytotoxic activity of C60 + Dox complex is accompanied by an increased level of cell produced hydrogen peroxide at early time point (3 h) after its addition to cultured cells. At the same time, cellular production of superoxide radicals does not change in comparison with the effect of Dox alone. Cytomorphological studies have demonstrated that C60 + Dox complexes kill tumor cells by apoptosis induction. The results of in vivo experiments using Lewis lung carcinoma in mice confirmed the enhancement of the Dox toxicity towards tumor cells after drug complexation with C60 fullerene. The effect of such complex towards tumor-bearing mice was even more pronounced than that in the in vitro experiment with targeting human tumor cells. The tumor volume decreased by 2.5 times compared with the control, and an average life span of treated animals increased by 63% compared with control. The obtained results suggest a great perspective of application of C60 + Dox complexes for chemotherapy of malignant tumors.

Дія комплексу C60 фулерену і доксорубіцину на пухлинні клітини in vitro та in vivo

Дія комплексу C₆₀ фулерену і доксорубіцину на пухлинні клітини <i>in vitro</i> та <i>in vivo</i>

Molecular properties of C60 fullerene complexes with cycle-containing polymers in solutions

The donor-acceptor complexes of the C60 fullerene with cycle-containing polymers, namely, poly(2,6-dimethyl-1,4-phenylene oxide) (PPhO) and poly(N-vinylpyrrolidone) (PVP), are studied. A comparative analysis of the hydrodynamic and electrooptical properties of the initial polymers and their complexes with C60 in solutions demonstrates that the C60 fullerene has a restructuring effect on the polymer macromolecule, thus decreasing the degree of asymmetry of the macromolecular structure.

Simulation of the molecular and electronic structure of C60 fullerene π-complex with twelve half-sandwich species FeC5H5

The problem of existence of η5-π-complexes of fullerenes and their derivatives is discussed. The stability of the η5-π-complex C60(FeCp)12 (viz., icosahedral C60 fullerene “coated” with twelve FeCp groups, each coordinated to its “own” pentagonal face of the fullerene cage) was first estimated in the framework of density functional approach (PBE approximation). The molecular and electronic structure of a biradical complex of C60 fullerene with ten FeCp groups, C60(FeCp)10 (D 5d symmetry), and a 2η5-π-complex of substituted fullerene H10C60, H10C60(FeCp)2 (D 5d symmetry) in which hydrogen atoms are attached to the C atoms in the α-positions relative to the atoms of the polar five-membered cycles, was simulated. According to calculations, the “coated” complex, I h-C60(FeCp)12, should be much more stable than the complex of “naked” fullerene with one or two polarly located FeCp groups and only slightly less stable than the ferrocene molecule FeCp2. The existence of C60(FeCp)12 and H10C60(FeCp)2 complexes was suggested.

Electronic and atomic structures of the isomers of endohedral and exohedral fullerene complexes with two lithium atoms

The electronic structures of all the possible isomers of endohedral and exohedral C60 fullerene complexes with two lithium atoms are theoretically investigated. It is found that the electronic structures of these compounds are characterized by an impurity filled-level state determining the band gap. The location of the impurity state and, correspondingly, the band gap of the exohedral fullerene complexes depend on the coordination mode and the distance between the alkali metal ions. A similar dependence is observed for the total energy of the exohedral fullerene complex under investigation.

Low-temperature dynamics and spectroscopy in exohedral rare-gas C60 fullerene complexes

The adatom dynamics in exohedral C60 fullerene complexes of rare-gas atoms are studied with a three degrees of freedom model. The eigenvalue problem of the corresponding quantum Hamiltonian is solved and the electric-dipole spectra for ArC60, NeC60, and HeC60 in the low-temperature range from 5 to 40 K are simulated. The most important spectral features are related to the degree of angular anisotropy in the adatom–C60 interaction. The ArC60 and NeC60 complexes present very simple spectra which can be assigned in terms of three-mode oscillators; the corresponding motion takes place in the deep hexagon wells (also in the pentagon wells for NeC60) of the interaction potential. On the contrary, the HeC60 complex shows more complicated spectra with important tunneling effects due to the smaller angular anisotropy of the interaction. The onset of almost free internal rotation takes place in this complex at rather low energies, and this gives rise to a low-frequency rotational band in the spectra at temperatures above T∼15 K.

Molecular complex of C60 fullerene with an organic π-donor, bis(methylenedithiotetrathiafulvalene): synthesis, crystal structures, and properties

A new molecular complex based on [60]fullerene, namely, (BMDT-TTF)·C60·2CS2 (1) (where BMDT-TTF is bis(methylenedithiotetrathiafulvalene)) was synthesized. The molecular and crystal structures of 1 were established by X-ray diffraction analysis. Complex 1 has a layered structure, layers of C60 molecules alternating with those formed by BMDT-TTF molecules and CS2 molecules located between them. In complex 1, there are short contacts between C60 and the donor molecules, which results in a changed BMDT-TTF geometry. The donor molecules in 1 form in addition short S...S contacts. The data of IR spectroscopy indicate that the charge transfer to the fullerene molecule is insignificant if at all present. The conductivity of a single crystal of 1 measured at ∼20 °C using a four-contact method is 2·10–5 (Ω cm)–1.

Ab initio calculations of endo-and exohedral C60 fullerene complexes with Li+ ion and the endohedral C60 fullerene complex with Li2 dimer

The results of ab initio Hartree-Fock calculations of endo-and exohedral C60 fullerene complexes with the Li+ ion and Li2 dimer are presented. The coordination of the Li+ ion and the Li2 dimer in the endohedral complexes and the coordination of Li+ ion in the exohedral complex of C60 fullerene are determined by the geometry optimization using the 3–21G basis set. In the endohedral Li+C60 complex, the Li+ ion is displaced from the center of the C60 cage to the centers of carbon hexa-and pentagons by 0.12 nm. In the Li2 dimer encapsulated inside the C60 cage, the distance between the lithium atoms is 0.02 nm longer than that in the free molecule. The calculated total and partial one-electron densities of states of C60 fullerene are in good agreement with the experimental photoelectron and X-ray emission spectra. Analysis of one-electron density of states of the endohedral Li+@C60 complex indicates an ionic bonding between the Li atoms and the C60 fullerene. In the Li+C60 and Li+@C60 complexes, there is a strong electrostatic interaction between the Li+ ion and the fullerene.

The first complex of C60 fullerene with bis(ethylenedithio)tetrathiafulvalene radical cation: C60·(BEDT-TTF·I3)

The complex of C60 fullerene containing the radical cation of the organic donor,viz., C60·(BEDT-TTF·I3), where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene, was synthesized for the first time. Single crystals of the complex were grown in benzonitrile. The crystals of this compound belong to the monoclinic system with a base-centered lattice. The unit cell parameters are as follows:a=17.419(6),b=9.997(4),c=13.499(1) A, β=99.00 (1)o. The IR and electronic spectra of single crystals of the complex have absorption bands characteristic of the BEDT-TTF.+ radical cation and neutral C60. The ESR spectrum has a signal withg=2.0074 and δH pp=23 G belonging to BEDT-TTF.+. The position of the 13d5/2 peak in the X-ray photoelectron spectrum confirms the formation of the I3 − anion.

Polarization effects in C60 fullerene complexes of alkali ions

We introduce a secular semiempirical model of the Pariser–Parr–Pople type to reproduce the electronic structure and polarizability of the C60 fullerene. The model is then used to simulate the response of this molecule to an electric charge and estimate its polarization energy. By expressing the charge potential at the C60-cage surface as a multipole expansion, an analytical form is obtained for the polarization energy. Application of these results to endo- and exohedral complexes of alkali ions gives data in rather good agreement with recent ab initio calculations [Hira and Ray, Phys. Rev. A 52, 141 (1995)].

Free and hindered rotations in endohedral C60 fullerene complexes

We propose a two-parameter model Hamiltonian to analyze the low-energy dynamics of endohedral C60 fullerene complexes such as Li+@C60, Na+@C60, CO@C60, LiF@C60, and LiH@C60. The simplicity of the model is a direct consequence of very strong constraints imposed by both high symmetry and close confinement conditions, on the spherical anisotropy of the guest–cage interaction. In the parameter space region expanded by the selected systems, the guest low-energy dynamics undergo transitions from almost free rotations to more or less hindered rotations. These dynamics produce very particular features in the low-temperature rotational spectra, which can be taken, therefore, as fingerprints of a particular guest–cage interaction. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 65: 655–663, 1997

Free and hindered rotations in endohedral C60 fullerene complexes

We propose a two-parameter model Hamiltonian to analyze the low-energy dynamics of endohedral C60 fullerene complexes such as Li+@C60, Na+@C60, CO@C60, LiF@C60, and LiH@C60. The simplicity of the model is a direct consequence of very strong constraints imposed by both high symmetry and close confinement conditions, on the spherical anisotropy of the guest–cage interaction. In the parameter space region expanded by the selected systems, the guest low-energy dynamics undergo transitions from almost free rotations to more or less hindered rotations. These dynamics produce very particular features in the low-temperature rotational spectra, which can be taken, therefore, as fingerprints of a particular guest–cage interaction. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 65: 655–663, 1997

Synthesis and Complex Crystal Structure of C60 with Symmetrical Donor of 2,3,6,7,10,11-Hexamethoxytriphenylene (HMT)

Abstract We have successfully synthesized the complex of C60 fullerene with a three-fold symmetrical donor of 2,3,6,7,10,11-hexamethoxytriphenylene (HMT). All spectroscopic data and analyses support the chemical composition of this complex as C60(HMT)2. Individually, each C60 fullerene sphere was found to be surrounded by four HMT molecules in distinctive tetrahedral arrangement. The closest distance from one C60 centroid to the next C60 centroid in the adjacent chain is 13.099 Å.