Reactivity Of Fullerenes Research Articles

A new approach to the estimation of the fullerene reactivity in 1,3-dipolar addition based on polarizability indices

A new approach to the estimation of the fullerene reactivity in 1,3-dipolar addition based on polarizability indices

C80Cl12: A Chlorine Derivative of the Chiral D2‐C80 Isomer—Empirical Rationale of Halogen‐Atom Addition Pattern

Welcome to the family! The constitution of the chiral D(2)-C(80) fullerene has been confirmed through single-crystal X-ray analysis of the chlorinated C(80)Cl(12). The addition pattern of the chlorine atoms in the structure of C(80)Cl(12) together with other structures of halogenated higher fullerenes is discussed. A stepwise principle of higher fullerene reactivity is proposed. Unusual short intermolecular chlorine-chlorine contacts are reported.

ChemInform Abstract: C1‐(C84—C2(11)) (CF3)12: Trifluoromethylation Yields Structural Proof of a Minor C84 Cage and Reveals a Principle of Higher Fullerene Reactivity.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

70]Fullerene Reactivity as Studied by Dynamic HPLC

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Kinetic Substituent and Solvent Effects in 1,3-Dipolar Cycloaddition of Diphenyldiazomethanes with Fullerenes C60and C70: A Comparison with the Addition to TCNE, DDQ, and Chloranil

Kinetics of 1,3-dipolar cycloaddition of a series of meta- and para-substituted diphenyldiazomethanes (DDMs) with fullerenes C60 and C70 as dipolarophiles have been investigated in toluene at 30 degrees C. Fullerene C60 was ca. 1.5 times more reactive than C70. The rate constants (k) for the primary [3 + 2] additions increased with the increase of the electron-releasing ability of the meta and para substituent. The log k/k0 values were well correlated by the Yukawa-Tsuno (Y-T) equations with the smaller negative rho values (-1.6 and -1.7 for C60 and C70) and the reduced resonance reaction constants r (0.22 and 0.17) compared to similar reactions of common acceptors, TCNE, DDQ, and chloranil (CA). The plots of log k (acceptor) versus log k (C60) as reference gave good regression equations and the slopes became larger in the order of TCNE > DDQ > CA > C70 > or = C60. The rates were also found to decrease with the increase of solvent polarity due to the ground-state solvation of fullerenes. However, the relative reactivity of these acceptors toward the unsubstituted DDM increased in the order of DDQ > C60 > or = C70 > TCNE > CA. The unexpected higher reactivity of fullerenes was interpreted in terms of the inherent steric strain by the pyramidalization of the sp2 C-atoms as well as the shorter [6,6] bonds with larger pi-electron densities.

3He NMR as a Sensitive Probe of Fullerene Reactivity: [2 + 2] Photocycloaddition of 3-Methyl-2-cyclohexenone to C70

The [2 + 2] photoadditions of 3-methyl-2-cyclohexenone to C70 and 3He@C70 have been studied by a combination of HPLC chromatography and FAB-MS, as well as IR and 1H and 3He NMR spectroscopies. The total yield of the mixture of monoadducts was 55% (67% on the basis of the recovered C70). The use of 3He NMR was especially powerful in determining the regioselectivity of the photoaddition reaction of enone to C70. Results of the 3He NMR experiments conducted on the product mixture implicate the two [6,6] bonds closest to the poles of the fullerene (C1-C2 and C5-C6) in the photoaddition process. This reaction mode is analogous to that of most thermal addition reactions to C70. Separation and characterization of the product mixture shows that eight distinct monoadducts are formed in the photoaddition, namely, the four diastereomeric adducts to the C1-C2 and C5-C6 bonds of the C70 cage, each consisting of cis- and trans-fused isomers in a ratio of 2:3. The major mode of photoaddition, accounting for 65% of the product mixture, involves addition to the C1-C2 bond of the ovoid fullerene. Mechanistic implications of these findings are discussed.

Local reactivity of fullerenes and nano-deviceapplications

A conceptual framework to understand the chemical reactivity offullerenes is developed as a design tool for nano-scale deviceapplications. The internal and external chemical reactivity offullerenes is found to depend strongly on the curvature andlocal atomic structure. As examples, we study C36,C60 and graphite, and use a hydrogen atom to probechemical reactivity as a function of local atomic structure.The analysis shows that the balance of strain energy andchemical binding energy determines the local reactivity. Thisunderstanding provides an insight into the use of chemicallydoped endo-fullerenes as suitable target material for a recentlyproposed design of a solid-state quantum computer.

Reactivity, spectroscopy, and structure of reduced fullerenes

Reduced fullerenes, the simplest covalent derivatives of the fullerene family of carbon allotropes, provide an excellent context for the study of the fundamental chemical reactivity of fullerenes. We have developed a general method for the formation of a number of these compounds. Using Zn(Cu) reduction, we have access to pure samples of several isomerically pure C 60H n and C 70H n species. We have completely assigned the 13C NMR spectrum of C 60H 6 and have assigned the majority of the resonances in C 60H 2.

Syntheses and properties of macromolecular fullerenes, a review

The recent progress and prospects of macromolecular fullerenes with respect to their syntheses and properties are compiled and discussed. The variety of macrofullerenes with emphasis on C60 and C70 is presented and synthetic concepts of polymer derivatives of fullerenes are outlined. After a concise consideration of the fundamentals of fullerene reactivity, both major types of fullerene-containing polymers, main-chain and side-chain polymers, together with special types, such as telechelic, macrocyclic, dendrimeric and star-shaped fullerene materials, are covered. Also, the synthesis of fullerene-containing copolymers via radical polyreactions and preparative aspects of surface-attached fullerenes are described. The properties of the macromolecular fullerene derivatives are discussed in view of their structure and application. Finally, the role of macrofullerenes for new materials or their precursors is elucidated. © 1999 Society of Chemical Industry

Syntheses and properties of macromolecular fullerenes, a review

The recent progress and prospects of macromolecular fullerenes with respect to their syntheses and properties are compiled and discussed. The variety of macrofullerenes with emphasis on C60 and C70 is presented and synthetic concepts of polymer derivatives of fullerenes are outlined. After a concise consideration of the fundamentals of fullerene reactivity, both major types of fullerene-containing polymers, main-chain and side-chain polymers, together with special types, such as telechelic, macrocyclic, dendrimeric and star-shaped fullerene materials, are covered. Also, the synthesis of fullerene-containing copolymers via radical polyreactions and preparative aspects of surface-attached fullerenes are described. The properties of the macromolecular fullerene derivatives are discussed in view of their structure and application. Finally, the role of macrofullerenes for new materials or their precursors is elucidated. © 1999 Society of Chemical Industry

Chemistry of fullerenes, novel allotropic modifications of carbon

The currently available data on the structure and reactivity of fullerenes, including the formation of metal complexes (including optically active ones) with fullerenes as ligands, are briefly surveyed. The properties and reactions of fullerenyl radicals and endohedral complexes are considered.

The chemical reactivity of fullerene C 60 towards fac-Mo(CO) 3 (MeCN)(dppe) and Mo(CO) 4(dppe). Synthesis, characterization and reactions of the novel fullerene molybdenum derivative fac-Mo(CO) 3(dppe)( η2-C 60)

The acetonitrile ligand of fac-Mo(CO) 3(MeCN)(dppe)[dppe = bis-(1,2-diphenylphosphino)ethane] can be easily replaced by fullerence C 60 in chlorobenzene at about 80°C to give exclusively fac-Mo(CO) 3(dppe)( η 2-C 60), whereas fullerene C 60 reacted with Mo(CO) 4(dppe) in refluxing chlorobenzene to afford an isomeric mixture of fac- and mer-Mo(CO) 3(dppe)( η 2-C 60). These organomolybdenum C 60 derivatives were characterized by elemental analysis and spectroscopic techniques. In addition, the η 2-C 60 ligand in fac-Mo(CO) 3(dppe)( η 2-C 60) was also found to be easily displaced by MeCN, PPh 3 or pyridine to give corresponding fac-organomolybdenum complexes.

Bowl-shaped PAH has C60-like reactivity

A bowl-shaped polycyclic aromatic hydrocarbon (PAH), C 26 H 12 , exhibits reactivity that is similar to that of soccer-ball-shaped buckminsterfullerene, C 60 , according to chemists at Boston College. The result suggests that the reactivity of fullerenes—which is driven largely by the strain associated with curving an aromatic network—can be extended to curved but not closed molecules. Hindy E. Bronstein, a Boston College graduate student, described the research on the bowl-shaped fullerene fragment to a symposium in Cancun. Bronstein carried out the work with Boston College chemistry professor Lawrence T. Scott. Bronstein and Scott find that the C 26 H 12 PAH they synthesize by flash pyrolysis of a suitable precursor undergoes reactions at interior carbon atoms—that is, trigonal carbon atoms shared by three rings. By contrast, the chemistry of PAHs, most of which are flat molecules, overwhelmingly occurs at carbons located around the edges of the molecules, Scott points out. This bridges the chasm bet...

Fullerene Reactivity in an Oxygen Plasma

Fullerene reactivity in an oxygen plasma was measured and compared with those determined under the same conditions for a comprehensive set of 50 carbon materials. The possible reasons for the high plasma reactivity of the fullerene sample in an oxygen plasma are discussed.

Reaction of “living” poly(ethylene oxide) chains with C 60

To determine the reactivity of fullerene toward oxanions, we have studied the grafting of “living” poly(ethylene oxide) (PEO-K +) and ethylene oxide “capped” polystyrene chains (PSCH 2CH 2O-K +) onto C 60 in THF. We demonstrate that, in this polar solvent, electron transfer from the oxanion to the highly electron accepting fullerene takes place. This transfer is limited to two electron per fullerene, and is accompanied by addition of polymer chains onto the C 60 probably through grafting of the generated radicals. SEC characterization of (PEO) XC 60 indicates the presence of products with molar masses corresponding to X≥6. That may result from aggregation occurring in this case as, using the same active species, practically only mono- and di-adducts are obtained if the chain is PS.

Thermal behavior of fullerenes in different gas atmospheres

The reactivity of a C 60 + 15% C 70 fullerene mixture in various gases was studied using thermal analysis (TG/DTA) and infrared spectroscopic techniques. The thermal behavior of fullerenes was found to be complex and strongly dependent on the heating rate, overlapping of different phenomena taking place. Comparison with the behavior of a number of carbon materials showed that the reactivity of fullerenes in air is similar to that of the least ordered forms of carbon. An interesting feature is the appearance of various exothermal O 2 gasification peaks as the heating rate is increased. C 60 undergoes concurrent sublimation and partial decomposition during heat treatment, leaving carbonaceous residues which are partially or totally gasified depending on the reactivity of the surrounding atmosphere. Condensed solids from the sublimation process could be recovered on the cool parts of the thermobalance; mixtures richer in C 60 than the starting one were obtained in Ar whereas heating in CO 2 led to recovery of oxygenated fullerene derivatives. Carbonaceous residues from pyrolysis in Ar and CO 2 were strong infrared absorbers and contained oxygenated (epoxy and carbonyl) functional groups.

Molecular Size and Pyramidalization: Two Keys for Understanding the Reactivity of Fullerenes

The large electron affinity of fullerenes such as C~O or C~O has been rationalized by taking into account the effects of molecular size, the number of five-membered rings, and pyramidalization on their LUMO energy. The study of conjugated cyclopolyenes having different size and pyramidalization has shown an enhancement of their electron affinity upon an increase in these two factors and with the presence of pentagonal instead of hexagonal rings. It has also been found that pyramidalization has an effect which is almost constant for all the systems studied, namely, a reduction of the LUMO energy by a similar extent. The stabilization of the LUMO orbital due to an increase in the molecular size is normally more determining than the effect of pyramidalization. The results obtained indicate that fullerenes exhibit enhanced electron-withdrawing character upon increase of their molecular size and pyramidalization. After the discovery' and synthesis in macroscopic quantities2 of c60 and (270, it was initially assumed that fullerenes exhibited extremely stable aromatic character. This initial hypothesis was soon rejected in the light of the numerous chemical reactions undergone by C60 and C703-8 (see ref 3 for recent reviews on chemical reactivity of fullerenes).

Reactivity of fullerenes with chemically generated singlet oxygen

Non-reactivity of fullerene C60 in its ground state with electronically excited molecular oxygen, O2(1Δg), chemically generated externally, has been observed, which could contribute to a better understanding of the fullerene photooxidation mechanisms.