Free C60 Research Articles

Nanographene Metallaprisms: Structure, Stimulated Transformation, and Emission Enhancement.

Nanographenes are inclined to assemble into stacked columnar structures that are stabilized by π-π interactions, whereas other supramolecular structures of nanographenes, such as prisms and cages, are rarely investigated. Herein, a diazananographene was synthesized, and then assembled with a coordination unit, thereby producing a triangular metallaprism. After adding C60 or C70 , the triangular metallaprism was transformed into a square tetramer, which encapsulated a pair of C60 or C70 molecules. The formed host-guest complex demonstrated efficient energy transfer from the diazananographene shell to the C60 cores. The emission intensity of the capsulated C60 was enhanced remarkably, compared with free C60 , due to an increased quantum yield and optical absorption coefficient. This work demonstrates the versatility of nanographene-based supramolecular architectures beyond columnar stacking and their ability to enhance the emission of otherwise non-emissive fullerene.

Nanographene Metallaprisms: Structure, Stimulated Transformation, and Emission Enhancement

Abstract Nanographenes are inclined to assemble into stacked columnar structures that are stabilized by π‐π interactions, whereas other supramolecular structures of nanographenes, such as prisms and cages, are rarely investigated. Herein, a diazananographene was synthesized, and then assembled with a coordination unit, thereby producing a triangular metallaprism. After adding C60 or C70, the triangular metallaprism was transformed into a square tetramer, which encapsulated a pair of C60 or C70 molecules. The formed host‐guest complex demonstrated efficient energy transfer from the diazananographene shell to the C60 cores. The emission intensity of the capsulated C60 was enhanced remarkably, compared with free C60, due to an increased quantum yield and optical absorption coefficient. This work demonstrates the versatility of nanographene‐based supramolecular architectures beyond columnar stacking and their ability to enhance the emission of otherwise non‐emissive fullerene.

Successive Diels-Alder Cycloadditions of Cyclopentadiene to [10]CPP⊃C60: A Computational Study.

Fullerenes have potential applications in many fields. To reach their full potential, fullerenes have to be functionalized. One of the most common reactions used to functionalize fullerenes is the Diels–Alder cycloaddition. In this case, it is important to control the regioselectivity of the cycloaddition during the formation of higher adducts. In C60, successive Diels–Alder cycloadditions lead to the Th-symmetric hexakisadduct. In this work, we explore computationally using density functional theory (DFT) how the presence of a [10]cycloparaphenylene ring encapsulating C60 ([10]CPP⊃C60) affects the regioselectivity of multiple additions to C60. Our results show that the presence of the [10]CPP ring changes the preferred sites of cycloaddition compared to free C60 and leads to the formation of the tetrakisadduct. Somewhat surprisingly, our calculations predict formation of this particular tetrakisadduct to be more favored in [10]CPP⊃C60 than in free C60.

The Impact of Fullerenes as Doxorubicin Nano-Transporters on Metallothionein and Superoxide Dismutase Status in MCF-10A Cells

This study aimed to synthesise C60–DOX complexes followed by the analysis of their effect on the concentration of metallothionein (MT) as a non-enzymatic antioxidant and on the concentration and activity of superoxide dismutase (SOD) as an antioxidant enzyme in healthy human mammary MCF-10A cells. Dynamic light scattering and electrophoretic light scattering were used to establish the size and zeta potential of the complexes. The MT and SOD concentrations were determined using the ELISA method; SOD activity was determined by tetrazolium salt reduction inhibition. Lower MT concentration following exposure of cells to both DOX and C60 fullerene compared to the control sample was found. However, the concentration of this protein increased as a consequence of the C60–DOX complexes action on MCF-10A cells compared to the control. C60 used alone did not affect the concentration and activity of SOD in MCF-10A cells. Application of free DOX did not activate cellular antioxidant defence in the form of an increase in SOD concentration or its activity. In contrast treatment of cells with the C60–DOX complex resulted in a decrease in SOD1 concentration and a significant increase in SOD activity compared to cells treated with free DOX, C60 and control. Thus, it was found that C60–DOX complexes showed potential for protective effects against DOX-induced toxicity to MCF-10A cells.

Long-Lived C60 Radical Anion Stabilized Inside an Electron-Deficient Coordination Cage.

Fullerene C60 and its derivatives are widely used in molecular electronics, photovoltaics, and battery materials, because of their exceptional suitability as electron acceptors. In this context, single-electron transfer on C60 generates the C60• - radical anion. However, the short lifetime of free C60• - hampers its investigation and application. In this work, we dramatically stabilize the usually short-lived C60• - species within a self-assembled M2L4 coordination cage consisting of a triptycene-based ligand and Pd(II) cations. The electron-deficient cage strongly binds C60 by providing a curved inner π-surface complementary to the fullerene's globular shape. Cyclic voltammetry revealed a positive potential shift for the first reduction of encapsulated C60, which is indicative of a strong interaction between confined C60• - and the cationic cage. Photochemical one-electron reduction with 1-benzyl-1,4-dihydronicotinamide allows selective and quantitative conversion of the confined C60 molecule in millimolar acetonitrile solution at room temperature. Radical generation was confirmed by nuclear magnetic resonance, electron paramagnetic resonance, ultraviolet-visible-near-infrared spectroscopy and electrospray ionization mass spectrometry. The lifetime of C60• - within the cage was determined to be so large that it could still be detected after one month under an inert atmosphere.

Effect of N,N,N′-trimethylpiperazinium (TMP+) cations on magnetic properties and dimerization of fullerenes in the (TMP+)(CoIIporphyrin)(C60−) salts

Effect of N,N,N′-trimethylpiperazinium (TMP+) cations on magnetic properties and dimerization of fullerenes in the (TMP+)(CoIIporphyrin)(C60−) salts

Density functional calculation of the molecular properties of the [Au20-C60-Au20]n− (n = 0, 1, 2, 3) model complexes

Density functional calculation of the molecular properties of the [Au20-C60-Au20]n− (n = 0, 1, 2, 3) model complexes

Carbon Nanotubes Conjugated with Triazole-Based Tetrathiafulvalene-Type Receptors for C60 Recognition.

Fullerene receptors prepared by a twofold CuI -catalyzed azide-alkyne cycloaddition reaction with π-extended tetrathiafulvalene (exTTF) have been covalently linked to single-walled carbon nanotubes and multi-walled carbon nanotubes. The nanoconjugates obtained were characterized by several analytical, spectroscopic and microscopic techniques (TEM, FTIR, Raman, TGA and XPS), and evaluated as C60 receptors by using UV-Vis spectroscopy. The complexation between the exTTF-triazole receptor in the free state and C60 was also studied by UV-Vis and 1 H NMR titrations, and compared with analogous triazole-based tweezer-type receptors containing the electron-acceptor 11,11,12,12-tetracyano-9,10-anthraquinodimethane and benzene rings instead of exTTF motifs, providing in all cases very similar values for the association constant (log Ka ≈3.0-3.1). Theoretical density functional theory calculations demonstrated that the enhanced interaction between the host and the guest upon increasing the size of the π-conjugated arms of the tweezer is compensated by an increase in the energy penalty needed to distort the geometry of the host to wrap C60 .

Synthesis of a Rod-rod Diblock Copolymer, Poly(3-hexylthiophene)-block-poly(furfuryl isocyanate), through the Anionic Polymerization with an Oxyanionic Macroinitiator

A rod-rod diblock copolymer (diBCP), poly(3-hexylthiophene)-block-poly(furfuryl isocyanate) (P3HT-b-PFIC), was synthesized through the anionic polymerization with an oxyanionic macroinitiator of P3HT. The properties of the diBCP (molecular weight, dispersity, composition, thermal stability, UV-visible absorption, and thin film morphology) were determined by various analytical methods. P3HT-b-PFIC was blended with C60 in a toluene solution to prepare a thin film of binary electron donor/acceptor system. Such blending enabled partial conjugation of the two components by the Diels-Alder reaction between furan and C60 at 60 °C for 3 h; the mixture was then spin-cast as a thin film, and annealed at 250 °C for 24 h. Tapping-mode atomic force microscopy (AFM) revealed that P3HT and C60 domains had nanoscale interfaces without a large phase segregation. This result indicated that the microphase separation of C60-functionalized P3HT-b-PFIC preserved even at high temperature provided free C60 molecules with channels to diffuse on the sides of P3HT domain, thus preventing the macroscopic crystallization of free C60 through the interfacial stabilization.

Diels-Alder addition to H2O@C60 an electronic and structural study

Diels-Alder addition to H2O@C60 an electronic and structural study

About the iron carbonyl complex with C60 and C70 fullerene: [Fe(CO)4(η2C60)] and [Fe(CO)4(η2C70)

ABSTRACTThe iron carbonyl complexes with C60 and C70 fullerenes were synthesized in high yield by photochemical irradiation of solutions of C60 and C70 in presence of Fe(CO)5. The resulting complexes were studied by FT-IR, Raman and electronic absorption spectroscopy. All the data are consistent with the structures [Fe(CO)4(η2C60)] and [Fe(CO)4(η2C70)]. The thermal stability and decomposition reaction of the two complexes were studied by TGA-FTIR and Differential Scanning Calorimetry (DSC). Both complexes decompose at moderate temperatures releasing CO and Fe(CO)5 in the vapor phase leaving a residue of metallic iron and free C60 or C70 fullerenes that can be recovered by solvent extraction of the decomposition residue.

Comparison of Bonds Existing Between C60 Fullerene and Polyamide Molecules in Various Nanocomposite Materials

Fullerene–polymer composites may find applications in different areas, particularly, in membrane technology. The formation of bonds between molecules of C60 fullerene and poly(phenylene isophtalamide) (PA) in PA-C60 composites was investigated. Powder-like PA-C60 mixtures, ultrafiltration membranes and nonporous thin films were studied by extracting C60 from the samples with various solvents. It was found that two types of fullerene coexist in the studied composites: the free (easily extractable) fullerene and the bound molecules. The percentage of extractable C60 in a given sample depends on sample composition and the method used for obtaining this nanocomposite material. An important factor in increasing the C60-PA bond strength is the duration of the material formation procedure. The quantitative processing of digital photographs of membranes, scanning electron microscopy (SEM), and electron spectroscopy for chemical analysis (ESCA) data showed that the free C60 is mainly located close to the active membrane surface. The bound C60 molecules are distributed throughout the membranes and films.

Zipping up fullerenes into polymers using rhodium(II) acetate dimer and N(CH2CH2)2NC60 as building blocks.

The reaction of Rh2(O2CCH3)4 with the functionalized fullerene N(CH2CH2)2NC60 can produce a linear, crystalline polymer or can trap free C60 or C70 molecules between similar chains.

Electrochemical Generation of Porphyrin-Porphyrin and Porphyrin-C60 Polymeric Photoactive Organic Heterojunctions

Electrochemical Generation of Porphyrin-Porphyrin and Porphyrin-C60 Polymeric Photoactive Organic Heterojunctions

Ab Initio Study of the Endohedral Fullerene PbH4@C60

The structure, electronic property and vibrational spectroscopy of the endohedral fullerene PbH4@C60 have been systematically studied by the Hartree Fock theory using 6-31 G as the basis set. In the first step, geometrical optimization of the PbH4, C60 and C60-PbH4 have been carried out. In the next step, these optimized geometries are used to calculate the inclusion energy and HOMO-LUMO gap (band gap). It is found that the PbH4 molecule is more compact when the PbH4 is seated in the center of the C60 cage, and the C60 cage may stabilize the PbH4 molecule. The formation of PbH4@C60 from the free C60 and Td PbH4 is endothermic with inclusion energy of 203.6616 kcal/mol. In addition, the IR active modes and harmonic vibrational frequencies of PbH4@C60 are also discussed.

Ordered phases of ethylene adsorbed on charged fullerenes and their aggregates

Ordered phases of ethylene adsorbed on charged fullerenes and their aggregates

Study of resonances in the photoionization of Ar@C60 and C60

The static-exchange method is applied to investigate photoionization of a confined system, Ar@C60. The realistic confinement potential employed in the present work explicitly includes the position of each carbon atom in the C60, which is a considerable improvement over methods to address the structure and photo dynamics of a confined system where the carbon shell is modelled by a spherically symmetric model potential. In the present study, photoionization from the deepest of the valence shells of C60 and Ar with ag symmetry is considered. There is a one-to-one correspondence between resonances that appear in the Ar@C60 system when the hole is in the 3s of the Ar, when the hole is in the C60 shell, or when the hole is in a free C60 system. Encapsulation of the Ar atom leads to some differences in the shapes and shifts in the energies of the resonant features in the cross-sections. However the qualitative features of the resonant state wave functions are very similar in the corresponding resonances of Ar@C60 and C60.

Conjugation of Dexamethasone to C60 for the Design of an Anti-Inflammatory Nanomedicine with Reduced Cellular Apoptosis

Dexamethasone (DEX) is a well-known anti-inflammatory drug, whose widespread clinical use is nevertheless restricted by its serious side effects. By conjugation of DEX with C60, we found that this nanomedicine retained the anti-inflammatory activity of DEX while reducing side effects in the animal model. In mouse thymocytes, the CCK-8 assay showed that the cytotoxicity of DEX-C60 was significantly lower than that of free DEX. Flow cytometric studies revealed that incubation with DEX-C60 induced much less apoptotic thymocytes. Interestingly, such reduced cytotoxicity and apoptosis were not observed when equal moles of free C60 and free DEX were coincubated with thymocytes, suggesting that the conjugation alters the signal pathway of DEX. Indeed, we found that the binding of DEX-C60 and a glucocorticoid receptor (GR) was partially blocked in the thymocytes, which resulted in down-regulation of several apoptosis-related genes. These findings help understand the mechanism of beneficial effects of this new nanomedicine, DEX-C60, and promote its clinical applications.

Raman scattering in non-polymerized and photo-polymerized C60 films at 5 K

The Raman spectra of non-polymerized and photo-polymerized fullerene films of various polymerization degrees were studied at 5 K in the 250–1590 cm−1 range. It was found that the Raman spectra of non-polymerized film display splitting of the lines corresponding to Ag and Hg vibrational modes of free C60 molecule which is induced by the crystal field of the low-temperature phase. The Raman spectra of photo-polymerized films at low temperatures exhibit pronounced lines corresponding to Ag(2) vibrations of monomers, dimers and linear chains. Based on the analysis of the spectra of photo-polymerized films of various polymerization degrees (∼45, ∼85, and ∼95%), the spectrum evolution in the region of molecular modes of fullerene was studied vs. polymerization degree. It was found that in the films with high polymerization degree (∼85 and ∼95%), the linear polymer chains dominate while in the film with lower polymerization degree (∼45%) the dimers are dominant. An increase of polymerization degree entails a significant frequency increase (∼2.8 cm−1) of Ag(2) mode of the fullerene monomer induced by changes in its environment upon the transition from non-polymerized to photo-polymerized films. Such a shift was not observed for the lines corresponding to the fullerene photopolymer.

Photoabsorption spectrum of the Xe@C60 endohedral fullerene

Photoabsorption spectrum of the Xe@C60 endohedral fullerene has been studied using the time-dependent-density-functional-theory (TDDFT), which represents the dynamical polarizability of an interacting electron system by an off-diagonal matrix element of the resolvent of the Liouvillian superoperator and solves the problem with the Lanczos algorithm. The method has been tested with the photoabsorption spectra for the free Xe atom and C60 fullerene. The result of the Xe atom encapsulated inside C60 confirms the three main peaks observed in the recent measurement in the energy region of the Xe 4d giant resonance and indicates the possibility that the Auger decay of the Xe+ has been greatly suppressed if the ion is encapsulated inside C60. It is suggested to use the current theoretical result around 22 eV to check this possibility.