Metal Fullerene Research Articles

Beryllium doping graphene, graphene-nanoribbons, C60-fullerene, and carbon nanotubes

Beryllium substitutional doping within graphene, graphene nanoribbons, and carbon nanotubes are investigated using first-principles density functional theory calculations. Nanoribbons with armchair and zigzag edges, semiconducting (10,0) and metallic (6,6) carbon nanotubes, and C60 fullerene structures are analyzed. Binding energy, doping energy, band structure, electronic density of states (DOS), and magnetic ordering are calculated. Our results demonstrate that conversely to perfect graphene, Be-doped graphene reveals a semiconducting behavior with an indirect band gap of 0.298eV. Formation energy analysis reveals that Be into graphene and ribbons is more energetically favorable, but the energies involved are larger than those obtained for B- and N-doped nanocarbons. For nanoribbons, two different ways of incorporating the Be atom are explored (dopant placed in the center or edge), demonstrating that armchair nanoribbons preserve the semiconducting behavior with a reduced band-gap whereas that zigzag nanoribbons exhibit a half-metallic behavior with magnetic order along the edges. Results on Be-doping zigzag (10,0) semiconducting and armchair (6,6) metallic nanotubes and C60 fullerene reveal the appearance of additional electronic states around the Fermi level. We envisage that the present investigation could motivate the realization of future experiments to introduce Be into sp2 graphite-like lattice using high temperature chemical vapor deposition method.

Bonding in exohedral metal–fullerene cationic complexes

We present a systematic theoretical study of the exohedral interaction between singly positively charged metal (M) atoms and the C60 fullerene in [M–C60]+ complexes. Calculations have been carried out by means of the density functional theory. We have considered alkali (Li, Na and K), alkaline-earth (Be, Mg and Ca) and first period transition metals (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) interacting with C60 in different positions: on top of a ring (pentagon or hexagon), a bond (hexagon–hexagon or hexagon–pentagon) and a C atom. A detailed topological analysis of the electronic density reveals metal–C60 exohedral interaction of the ion-induced dipole type, with the positive charge localized on the metal atom and with increasing covalent character for the heavier transition metals. An energy decomposition analysis allows us to quantify the different contributions to the bonding in each complex, being dominant the polarization one. A simple ion-induced dipole model explains the main features of the interaction.

Dielectric properties of C60 and Sc3N@C80 fullerenol containing polyurethane nanocomposites

ABSTRACTPolymer–fullerene nanocomposites consisting of linear polyurethane (PU) chains crosslinked via increasing loadings of polyhydroxylated fullerenes (C60 and Sc3N@C80, a metallic nitride fullerene) were prepared and characterized for their mechanical and dielectric properties using dynamic mechanical analysis (DMA) and broadband dielectric spectroscopy (BDS). Fullerene–polymer networks [C60‐PU and Sc3N@C80‐PU] having high gel fractions, good mechanical properties and thermal stabilities were produced. Polyhydroxylated fullerenes C60(OH)29 and Sc3N@C80(OH)18 were synthesized in high yield through a high‐speed vibration milling method and characterized using FTIR, matrix‐assisted laser desorption/ionization mass spectroscopy, and thermal gravimetric analysis. DMA of fullerene–PU networks indicates Tg ∼ −50°C, with a sub‐Tg relaxation due to local chain motions. BDS analyses of the fullerenes, before and after hydroxylation and before incorporation into the networks, revealed one relaxation and large real permittivity (ε′) values for C60(OH)29 relative to C60. Analogous samples for Sc3N@C80 exhibit two relaxations, where the extra relaxation is attributed to motions of the cage‐encapsulated Sc3N clusters. ε′ values for Sc3N@C80‐PU at a given frequency are higher than corresponding values for C60‐PU, likely because of the rotationally mobile Sc3N encapsulates. Surface and bulk resistivities of fullerene–PU networks were found to have a modest dependence on relative humidity. Capacitance versus voltage characteristics of the fullerene–PUs were also studied in the range of the applied dc bias voltage of −30 to +30 v. It is generally concluded, based on all the evidence that this class of materials can be rendered quite polarizable and could be used as high dielectric permittivity materials in capacitance applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40577.

Effect of Water and Solvent Selection on the SAFA Purification Times for Metallic Nitride Fullerenes

This paper addresses two key parameters in the SAFA purification method for isolating endohedral metallofullerenes. The percent water content in the reactive aminosilica significantly affects the time needed to isolate Sc3N@Ih -C80 metallic nitride fullerene (MNF). The role of solvent selection in the SAFA process is also discussed. The SAFA purification time needed for isolating Sc3N@Ih -C80 metallofullerene is influenced by the identity of the electron donating/accepting group on the aromatic solvent.

Structures and Properties of Metal Sulfide Fullerene Sc2S@C90

Metallic sulfide fullerene Sc2S@C90 has been detected by mass spectra but not been isolated and structurally characterized. It is impossible to perform extensive tests on Sc2S@C90 due to its low yield, quantum chemical calculations thus become an important method to predict or identify its structure and properties. Here a systematic density functional the- ory study are first performed on 15756 isomers of fullerene C90 and their anions with 0~3 pairs of fused-pentagons, then 30 isomers of metallic sulfide fullerenes Sc2S@C90 are constructed by putting Sc2S into the selected candidate cages with dif- ferent orientations and geometrical optimizations are performed on these isomers with the density functional theory method. The calculated results demonstrate that the two lowest-energy isomers are Sc2S@C90:99913 and Sc2S@C90:99915, respec- tively. Both isomers satisfy the isolated-pentagon rule. To clarify the relative stabilities of the five lowest-energy isomers of Sc2S@C90 at high temperatures, enthalpy-entropy interplay has been taken into consideration with respect to the temperature range of up to 4000 K; the calculations demonstrate that the two lowest-energy isomers of Sc2S@C90 may coexist in the soot at high temperatures. Structural analysis demonstrated that the two isomers can transfer into each other by two Stone-Wales rotations, further suggesting the possibility of interconversion between them. Molecular orbital analysis indicates that Sc2S cluster transfers four electrons to the cage; however nature charge analysis demonstrates the charges transferred from the encaged cluster to the parent cage is much smaller than that with the simple molecular orbital analysis. The quantum theory of atoms in molecules is used to investigate the connectivity and interaction nature between the encaged cluster and parent cage. The results show that there are strong interactions between the encaged cluster and parent cage. The simulated infrared spectra of the two lowest-energy isomers are provided to assist future experimental identification and characterization of the structure of Sc2S@C90. Keywords endohedral fullerene; Sc2S@C90; density functional theory; relative concentrations; QTAIM

Intercalation of Metallic Potassium and Fullerene C60 into Natural Graphite

Graphite was intercalated with potassium to produce C8K intercalate which was subsequently exposed to suspension of fullerene C60 in toluene. The resulting product stabilized potassium against effects of the atmosphere. The prepared product was exposed to tests of thermal stability and other analyses, such as FT-IR, SEM and Energy-dispersive X-ray Spectroscopy (EDAX) with the objective to describe arrangement of potassium in the carbon matrix. The product with stabilized potassium in a carbon skeleton (graphite – fullerite) is partly able to resist the atmosphere, it is relatively thermally stable (up to 150 oC) and the energy effects of its decomposition are low up to 600 oC. The product may be used in numerous applications – catalysis, hydrogen storage and as an admixture component in aerosol fire suppression systems.

Structural and Bonding Analyses on a Homologous Metal–Metal Bond Guest–Host Series M2@C50X10(M = Zn, Cd, Hg; X = CH, N, B)

AbstractA systematic density functional study was performed on the structures and bonding features in a homologous metal–metal (M–M) host–guest series M2@C50X10(M = Zn, Cd, Hg; X = CH, N, B). Calculations indicated thatD5dconformers are energy minima for Zn2@C50X10(X = CH, N) and Cd2@C50X10(X = CH, N, B), whereas Zn2@C50B10has no imaginary frequency with the loweredC2hsymmetry. Among these hybrid fullerene–metal complexes, those with dizinc and dicadmium guests adopt η5/η5coordination, except for an η2/η2case inC2h‐Zn2@C50B10, to meet appropriate interactions between the metal atom and cage; and the η1/η1coordination mode can only be satisfied in just one (Hg2@C50N10) of the complexes with Hg–Hg guests, regardless of the enforced coordination surroundings. The nature of metal–cage interactions between M22+and C50X102–moieties and M–M bonds have been analyzed by means of the topological properties of electron densities and energy‐partitioning methods, and results suggest that the two types of interactions are almost similar to those in their M2(C5H5)2counterparts.

Is the Isolated Pentagon Rule Always Satisfied for Metallic Carbide Endohedral Fullerenes?

Quantum-chemical calculations reveal that metallic carbide endohedral fullerene Y(2)C(2)@C(84) possesses a novel fullerene cage, C(1)(51383)-C(84), with one pair of pentagon adjacencies. One of the encapsulated yttrium atoms is located on the adjacent pentagons, while the other stays on a hexagonal ring in the fullerene cage. As one of numerous metallic carbide endohedral fullerenes, Y(2)C(2)@C(1)(51383)-C(84) is the first example that violates the well-known isolated pentagon rule (IPR). More interestingly, compared with the fact that Sc(2)C(2)@C(84) has a conventional IPR-satisfying cage, D(2d)(51591)-C(84), Y(2)C(2)@C(84) utilizes the novel fullerene cage C(1)(51383)-C(84) with one pair of pentagon adjacencies.

ChemInform Abstract: Synthesis, Properties, and Examples of the Use of Carbon Nanomaterials

AbstractReview: 62 refs.

Evolution of Late Transition‐Metal‐Catalyzed Intermolecular Reductive Coupling Reaction of [60]Fullerene and N‐Sulfonylaldimines: Competing Formation of Hydrobenzylated [60]Fullerenes and 1,2‐Dihydrofullerene

AbstractA system based on late transition‐metal halides, phosphanes, water, and reducing agents in 1,2‐dichlorobenzene can efficiently catalyze the intermolecular reductive coupling of [60]fullerene with N‐sulfonylaldimines to afford novel 1,2‐hydrobenzylated [60]fullerene derivatives. We found that both group VII B metals (cobalt, rhodium, iridium) and group VIII B metals (nickel, palladium, platinum) perform this coupling reaction. A control experiment in the absence of aldimines produced C60H2, which showed that the reaction might proceed via a [60]fullerene metal complex [M(η2‐C60)(ligand)]. An isotope labeling experiment with D2O as deuterium source resulted in deuterioaryzilation with deuterium bonded to the sp3‐carbon of C60, providing evidence of a five‐membered azametallacycle intermediate. Evaluation of the scope of reductive coupling reaction with versatile aldimines gave access to the hydroaryzilation products. All the reductive coupling products were completely characterized by IR and NMR spectroscopy and ESI mass spectrometry. A possible reaction mechanism based on these results is proposed. This discovery of the formation of reductive coupling compounds and metal‐catalyzed formation of C60H2 are both new to metal catalysis and fullerene chemistry.

Structural Consequences of Duplicitous Chemical Relation of Cobalt and Fullerene in Mixture

The factors driving the structure organization in the Co-C60 films fabricated by simultaneous deposition were analyzed. It is shown that phase separation is the major factor yielding the nanocomposite (NC) structure in the co-deposited film (fcc-Co nanocrystals immersed into C60-based matrix). The phase separation is accompanied by accumulation of compressive stress in the film mixture. The metal–fullerene chemical bonding is the next important factor responsible for creation of the –Co-C60- polymer in the NC matrix. Thermal treatment can significantly influence the structure organization through enhancement of the main factors (phase separation or chemical bonding) that yields the remarkable structural effects. In particular, annealing at the elevated temperatures (Ta = 300–500°C) induces the regular carbon structure transformations in the NC matrix followed by creation of carbon nanotubes or graphitic-like shells (depending on Ta ). The C-structure transformation is controlled by catalytic effect of Co atoms retaining in the NC matrix.

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(C(60) )(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.

Optically active rhodium and iridium C 60 complexes containing the enantiomeric ligand (+)DIOP: (η 2-C 60)MH(CO)[(+)DIOP] (M=Rh, Ir)

The fullerene–metal complexes (η2-C60)MH(CO)[(+)DIOP] (M=Ir, Rh) have been prepared by the exchange reaction of PPh3 in corresponding (η2-C60)MH(CO)(PPh3)2 for the chelate optically active ligand (+)DIOP [(+)-2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)ethane] and their structures assigned.

Assembly of the First Fullerene‐Type Metal–Organic Frameworks Using a Planar Five‐Fold Coordination Node

Pump up the volume: Slow crystallization of Na[C5(CN)5], the unsolvated sodium salt of pentacyanocyclopentadienide, gives the first example of an anionic coordination network based on metal–fullerene units. The structure of this network is closely related to a type I gas clathrate (see picture) in which around 66 % of the unit cell volume is occupied by solvent molecules.

Synthesis, properties, and examples of the use of carbon nanomaterials

The results of a series of works on the synthesis and investigation of various carbon nanostructures and elaboration of functional materials of their basis are generalized and reviewed. Fullerenes and single-, double-, and multi-walled carbon nanotubes were prepared by the electric arc evaporation of graphite and metal—graphite rods. Diverse types of carbon nanofibers and nanotubes were grown by the catalytic pyrolysis of ethylene and methane. Graphene structures were synthesized by the chemical reduction of graphite oxide. Methods for isolation, purification, and functionalization of carbon nanostructures were elaborated. Chemical transformations in the fullerene—metal phase—hydrogen system were studied. Methods for metal cluster application on carbon nanostuctures and formation of metal hydride—carbon composites were developed. The possibilities were elucidated of using carbon nanostructures for the development of hydrogen accumulating and hydrogen generating composites, for forming carbon—polymer and carbon—ceramic composites, for preparing hardening additives to polymers and glue compositions, and for producing high-performance catalysts for hydrogenation and redox processes in fuel cells.

Metallic nitride azafullerenes: A novel class of fullerenes with interesting electronic properties

Following a recent report of the successful facile synthesis of one metallic nitride azafullerene (MNAF), a quantum chemical investigation was reported here on a series of MNAFs: LanSc3−nN@C79N, (n=0, 1, 2, 3), in which La and Sc represent the largest and smallest transition metals that can form stable endohedral metallofullerenes. Their steric effects have similar trends compared to the corresponding metallic nitride fullerenes (MNFs) as LanSc3−nN@C80. However, molecular orbital studies suggest for the first time that MNAFs have excellent electronic properties compared to MNFs and other azafullerenes including C59N, which was recently used in building n-type electronic devices.

Poly(perfluoroalkylation) of Metallic Nitride Fullerenes Reveals Addition-Pattern Guidelines: Synthesis and Characterization of a Family of Sc3N@C80(CF3)n(n= 2−16) and Their Radical Anions

A family of highly stable (poly)perfluoroalkylated metallic nitride cluster fullerenes was prepared in high-temperature reactions and characterized by spectroscopic (MS, (19)F NMR, UV-vis/NIR, ESR), structural and electrochemical methods. For two new compounds, Sc(3)N@C(80)(CF(3))(10) and Sc(3)N@C(80)(CF(3))(12,) single crystal X-ray structures are determined. Addition pattern guidelines for endohedral fullerene derivatives with bulky functional groups are formulated as a result of experimental ((19)F NMR spectroscopy and single crystal X-ray diffraction) studies and exhaustive quantum chemical calculations of the structures of Sc(3)N@C(80)(CF(3))(n) (n = 2-16). Electrochemical studies revealed that Sc(3)N@C(80)(CF(3))(n) derivatives are easier to reduce than Sc(3)N@C(80), the shift of E(1/2) potentials ranging from +0.11 V (n = 2) to +0.42 V (n = 10). Stable radical anions of Sc(3)N@C(80)(CF(3))(n) were generated in solution and characterized by ESR spectroscopy, revealing their (45)Sc hyperfine structure. Facile further functionalizations via cycloadditions or radical additions were achieved for trifluoromethylated Sc(3)N@C(80) making them attractive versatile platforms for the design of molecular and supramolecular materials of fundamental and practical importance.

TDDFT study on the second-order nonlinear optical properties of a series of mono- and di-nuclear [60]fullerene complexes

Time-dependent density functional theory (TDDFT) was employed to study second-order nonlinear optical (NLO) properties of transition metal fullerene complexes with a face to face model. The results show that the ruthenium species possesses the larger second-order NLO response than that of the iron species. Chemical modifications of the fullerene by carbon–carbon bond scission can tune charge transfer character in these complexes, and increase the static first hyperpolarizability. The electronic structure analysis and TDDFT calculations show that the open-cage complex in the ruthenium species possesses low-lying and strong charge transfer transitions, and thus give the largest second-order NLO response.

Highly Soluble Penta[(alkyl)dimethylsilylmethyl][60]fullerenes and Their Ruthenium and Palladium Complexes

Abstract Copper-mediated fivefold addition of RMe2SiCH2MgCl to [60]fullerene produces C60(CH2SiMe2R)5H (R = H, Et, n-Bu, and n-hexyl), which can be further converted into ruthenium and palladium complexes. These organofullerenes and metal–fullerene complexes, particularly when R = n-Hex, are highly soluble in various organic solvents, e.g., 107 mg mL−1 solubility in EtOAc and >1000 mg mL−1 in hexane, where C60Me5H is essentially insoluble.

Metallic Nitride Fullerenes in Films and Coatings

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