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1.
Photolysis of (C 59N) 2 solutions in the presence of neutral π-donors, such as arenes and electron-rich alkenes leads to a series of novel aza[60]fullerene monoadducts. The key step of the reaction involves a photoinduced electron transfer from the donor molecule to the iminium cation of aza[60]fullerene, followed by radical coupling of the resulting aza[60]fullerenyl radical with an intermediate stabilized radical derived from the substrate. This type of reactivity has been proven efficient with arenes having oxidation potential higher than about 1.5 V. Simple olefins, such as tri- and tetra-methylethylene, as well as cyclohexene, can also participate in this kind of photoinduced electron transfer-initiated reaction with C 59N +, affording the corresponding aza[60]fullerene derivatives. In the case of 2-methoxyprop-1-ene, 2,4-hexadiene, and β,β-dimethylstyrene, [2+2] cycloaddition reactions with the aza[60]fullerene carbon shell dominate, leading to a mixture of unidentified multiadducts. 相似文献
2.
A systematic screening study of the exohedral reactivity of the reduced fullerenes (fullerenides) C 602− and C 60⋅− is reported. These doubly and singly negatively charged carbon cages were prepared by two-fold reduction of C 60 with potassium, leading to K 2C 60, or by in situ monoreduction with the radical anion of benzonitrile PhCN ⋅−, respectively. Several series of electrophiles, including geminal and distant dihalides, benzyl bromides, and diazonium compounds, were employed as addition partners. In general, the investigated bromides proved to be the most suitable reaction partners. A series of fullerene adducts and cycloadducts involving either 1,2- or 1,4-addition patterns, depending on the precise architecture and the steric demand of the addends, were synthesized and fully characterized. Some of the reaction products are unprecedented and inaccessible forms of neutral C 60. The fullerenide chemistry presented here closely resembles related reactions of graphenides and carbon nanotubides, which are the most powerful methods for the functionalization of these macromolecular forms of synthetic carbon allotropes (SCAs). Activation of C 60 by negative charging represents a little explored concept of fullerene chemistry, providing both new insights of fullerene reactivity itself and new types of exohedral derivatives. 相似文献
3.
The origin of the experimentally known preference for [6,6] bonds in cycloaddition reactions involving C60 has been computationally explored. To this end, we examined the reactions of 1,3-dienes with fullerene (C60) in the context of an approach to open a large orifice on the fullerene framework by using the activation model of reactivity in combination with the energy analysis method. In this study, the effect of the alkali metal of Li+, Na+, and K+ as an encapsulated element was investigated on the kinetic and thermodynamic behaviors of the Diels–Alder (DA) process. Our calculations indicated that encapsulated Na+ and K+ cations are located close to the center of the C60 molecule; however, encapsulated Li+ is displaced from the center, which leads to a higher reactivity for Li+@C60 in DA cycloaddition reaction in the gas phase. Also, benzene as a non-polar solvent affects the DA reactions greater than water as a polar solvent. Different analyses show that solvent changes the catalysis reaction performance, in which a greater efficiency was obtained for K+ in the solvent in comparison with other alkali ions because of a facilitated mechanism of electron transfer. 相似文献
4.
Active sites in carbon‐catalyzed phosgene synthesis from gaseous CO and Cl 2 have been identified using C 60 fullerene as a model catalyst. The carbon atoms distorted from sp 2 coordination in non‐planar carbon units are concluded to generate active Cl 2. Experiments and density functional theory calculations indicate the formation of a surface‐bound [C 60???Cl 2] chlorine species with radical character as key intermediate during phosgene formation. It reacts rapidly with physisorbed CO in a two‐step Eley–Rideal‐type mechanism. 相似文献
5.
Multiwall carbon nanotubes (MWNTs) based on the template carbonization technique were fluorinated in a temperature range 323-473 K by elemental fluorine. The fluorination of the carbon nanotubes results in functionalization and modification of pristine nanotubes with respect to adsorption and electrochemical properties. Selective fluorination of the inner surface of the carbon nanotubes, brings about a decrease in the surface free energy of the inner surface of the tubes and an increase in colombic efficiency of Li/nanotubes rechargeable cells in an aprotic medium. Electrochemical fluoride-ion doping of fullerene C 60 thin films (250-450 nm) was carried out in a fluoride-ion conductive solution, MeCN solution of 1 M Et 4NF·4HF. Galvanostatic oxidation yielded C 60F ca.1-3 where fluorine exists as a semi-ionic species in the cavity surrounded by C 60 molecules without forming covalent CF bonds 相似文献
6.
Poly(trifluoromethyl)fullerene S6‐C 60(CF 3) 12 was reduced by sodium fluorenone ketyl in the presence of (PPN)Cl (PPN=bis(triphenylphosphine)iminium) to afford the salt (PPN)[C 60(CF 3) 12] ( 1 ), which contains C 60(CF 3) 12.? radical anions. In the crystal structure of 1 , C 60(CF 3) 12.? layers alternate with the PPN + cations. There are short F ??? F contacts between C 60(CF 3) 12.? radical anions within the layers but no C ??? C contacts. DFT calculations revealed that the negative charge on C 60(CF 3) 12.? is distributed mainly between sp 2 carbon and fluorine atoms, whereas spin density is localized mainly on the fullerene‐cage sp 2 carbon atoms. IR and UV/Vis/NIR spectra in the solid state and solution showed characteristic changes relative to those of neutral S6‐C 60(CF 3) 12 due to the formation of radical anions. The solid‐state electronic spectrum of 1 exhibits a single broad band at 738 nm attributed to C 60(CF 3) 12.?. Crystals of 1 show a narrow EPR signal with g=2.0025 (Δ H=0.45 mT) at 300 K. The temperature dependence of the integral intensity follows the Curie–Weiss law with a negative Weiss temperature of ?11.8 K (30–300 K) indicating antiferromagnetic interaction of spins. This dependence was approximated by the Heisenberg model for one‐dimensional chains of antiferromagnetically interacting spins with exchange interaction J/ kB=?9.1 K. It was assumed that magnetic interaction between the C 60(CF 3) 12.? spins in the layers is mediated by short F ??? F contacts. 相似文献
7.
High oxidation potential perfluorinated zinc phthalocyanines (ZnF nPcs) are synthesised and their spectroscopic, redox, and light‐induced electron‐transfer properties investigated systematically by forming donor–acceptor dyads through metal–ligand axial coordination of fullerene (C 60) derivatives. Absorption and fluorescence spectral studies reveal efficient binding of the pyridine‐ (Py) and phenylimidazole‐functionalised fullerene (C 60Im) derivatives to the zinc centre of the F nPcs. The determined binding constants, K, in o‐dichlorobenzene for the 1:1 complexes are in the order of 10 4 to 10 5 M ?1; nearly an order of magnitude higher than that observed for the dyad formed from zinc phthalocyanine (ZnPc) lacking fluorine substituents. The geometry and electronic structure of the dyads are determined by using the B3LYP/6‐31G* method. The HOMO and LUMO levels are located on the Pc and C 60 entities, respectively; this suggests the formation of ZnF nPc .+–C 60Im .? and ZnF nPc .+–C 60Py .? ( n=0, 8 or 16) intra‐supramolecular charge‐separated states during electron transfer. Electrochemical studies on the ZnPc–C 60 dyads enable accurate determination of their oxidation and reduction potentials and the energy of the charge‐separated states. The energy of the charge‐separated state for dyads composed of ZnF nPc is higher than that of normal ZnPc–C 60 dyads and reveals their significance in harvesting higher amounts of light energy. Evidence for charge separation in the dyads is secured from femtosecond transient absorption studies in nonpolar toluene. Kinetic evaluation of the cation and anion radical ion peaks reveals ultrafast charge separation and charge recombination in dyads composed of perfluorinated phthalocyanine and fullerene; this implies their significance in solar‐energy harvesting and optoelectronic device building applications. 相似文献
8.
Conjugate halogenation of methyl tricyclo[4.1.0.0 2,7]heptane-1-carboxylate by the action of N-iodoand N-bromosuccinimides in the presence of halide ions occurs exclusively at the central bicyclobutane C 1–C 7 bond via electrophilic attack on the C 1 atom, leading to endo,syn-adducts of the norpinane series. Reactions of the title compound with iodine, dibromotetrachloroethane, and (dichloro-λ 3-iodanyl)benzene give not only the corresponding 6,7- endo,syn-dihalonorpinane but also its epimer at C 6, indicating radical mechanism of the halogenation. The regio-and stereoselectivity observed in these ionic and radical reactions are discussed in terms of the results of nonempirical MP2/STO-3G calculations of appropriate cationic and radical intermediates. 相似文献
9.
The involvement of fullerene in the radical copolymerization of diallyl isophthalate with methyl methacrylate or styrene results in a change in the relative activity of monomers owing to the interaction of C 60 with the allyl radical yielding a “quo;new,”quo; more active radical. This corresponds to the transition from degradative chain transfer to effective transfer to the allyl compound. It is of great importance that, at an amount of diallyl isophthalate in the monomer mixture of up to 10 mol %, C 60 fullerene is almost completely incorporated into macromolecules. 相似文献
10.
The atom transfer radical addition polymerization (ATRAP) of fullerene to give poly(fullerene)s (PFs) for organic electronics is explored. Quantum chemistry maps the expected electronic behavior of PFs with respect to common electron acceptors, namely fullerene, phenyl‐C 61‐butyric acid methyl ester and its bis‐adduct, and mono‐ and bis‐indine‐fullerene derivatives. Surprisingly, it is found that PFs should demonstrate electron affinities and LUMO energy levels closer to the bis‐derivatives than the mono‐adducts, even though only one C 60 double‐bond is used in PF chain formation. A self‐consistent library of PFs is synthesized and a correlation between structural characteristics and molecular weights is found. While comonomers with –OC 16H 33 linear side‐chains lead to the highest known ATRAP molecular weights of 21000 g mol ? 1, like‐for‐like, branched side‐chains permit syntheses of higher molecular weights and more soluble polymers. Of the series, however, PFs with ‐OC 12 side‐chains are expected to be of the greatest interest for opto‐electronic applications due to their ease of handling and highest regioregularity. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1345–1355 相似文献
11.
The quantum-chemical simulation of possible reactions occurring at the initial stage of the free-radical polymerizations of styrene and methyl methacrylate in the presence of fullerene C 60 is performed. The reactions of interaction between initiating and model short-chain growing radicals containing from one to three monomer units with fullerene are considered. It is shown that, at the initial stage of styrene polymerization, the addition of short-chain growing radicals to fullerene predominates (with respect to the reaction of chain propagation). In the case of methyl methacrylate polymerization in the presence of fullerene C 60, the induction period is absent because of a higher probability of the initiation and chain propagation reactions (compared with the chain-termination reaction of short growing poly(methyl methacrylate) chains on fullerene C 60). The formation of bis- and trisadducts of fullerene C 60 with short-chain styrene and methyl methacrylate growing radicals is analyzed. The quantum-chemical simulation results are confirmed by electron spectroscopy and ESR studies. 相似文献
12.
The novel C 60–styrene copolymers with different C 60 contents were prepared in sodium naphthalene-initiated anionic polymerization reactions. Like the pure polystyrene, these copolymers exhibited the high solvency in many common organic solvents, even for the copolymer with high C 60 content. In the polymerization process of C 60 with styrene an important side reaction, i.e., reaction of C 60 with sodium naphthalene, would occur simultaneously, whereas crosslinking reaction may be negligible. 13C-NMR results provided an evidence that C 60 was incorporated covalently into the polystyrene backbone. In contrast to pure polystyrene, the TGA spectrum of copolymer containing ∼ 13% of C 60 shows two plateaus. The polystyrene chain segment in copolymer decomposed first at 300–400°C. Then the fullerene units reptured from the corresponding polystyrene fragments attached directly to the C 60 cores at 500–638°C. XRD evidence indicates that the degree of order of polymers increases with the fullerene content increased in terms of crystallography. Incorporation of C 60 into polystyrene results in the formation of new crystal gratings or crystallization phases. In addition, it was also found that [60]fullerene and its polyanion salts [C 60n−( M+) n, M = Li, Na] cannot be used to initiate the anionic polymerization of some monomers such as acrylonitrile and styrene, etc.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2653–2663, 1998 相似文献
13.
A ruthenium complex, porphyrin sensitizer, fullerene acceptor molecular pentad has been synthesized and a long‐lived hole–electron pair was achieved in aqueous solution by photoinduced multistep electron transfer: Upon irradiation by visible light, the excited‐state of a zinc porphyrin ( 1ZnP*) was quenched by fullerene (C 60) to afford a radical ion pair, 1,3(ZnP .+‐C 60.−). This was followed by the subsequent electron transfer from a water oxidation catalyst unit (Ru II) to ZnP .+ to give the long‐lived charge‐separated state, Ru III‐ZnP‐C 60.−, with a lifetime of 14 μs. The ZnP worked as a visible‐light‐harvesting antenna, while the C 60 acted as an excellent electron acceptor. As a consequence, visible‐light‐driven water oxidation by this integrated photosynthetic model compound was achieved in the presence of sacrificial oxidant and redox mediator. 相似文献
14.
Copolymerization of fullerene (C 60) with methyl methacrylate (MMA) was carried out using triphenylbismuthonium ylide (abbreviated as Ylide) as a novel initiator in dioxan at 60°C for 4 h in a dilatometer under a nitrogen atmosphere. The reaction follows ideal kinetics: R p∝ [Ylide] 0.5[C 60] ?1.0[MMA] 1.0. The rate of polymerization increases with an increase in concentration of initiator and MMA. However, it decreases with increasing concentration of fullerene due to the radical scavenging effect of fullerene. The overall activation energy of copolymerization was estimated to be 57 KJ mol ?1. The fullerene-MMA copolymers (C 60-MMA) were characterized by FTIR, UV–Vis, NMR and GPC analyses. 相似文献
15.
The effect of fullerene (C 60) on the radical polymerization of methyl methacrylate (MMA) in benzene was studied kinetically and by means of ESR, where dimethyl 2,2′-azobis(isobutyrate) (MAIB) was used as initiator. The polymerization rate ( Rp) and the molecular weight of resulting poly(MMA) decreased with increasing C 60 concentration ((0–2.11) × 10 −4 mol/L). The molecular weight of polymer tended to increase with time at higher C 60 concentrations. Rp at 50°C in the presence of C 60 (7.0 × 10 −5 mol/L) was expressed by Rp = k[MAIB] 0.5[MMA] 1.25. The overall activation energy of polymerization at 7.0 × 10 −5 mol/L of C 60 concentration was calculated to be 23.2 kcal/mol. Persistent fullerene radicals were observed by ESR in the polymerization system. The concentration of fullerene radicals was found to increase linearly with time and then be saturated. The rate of fullerene radical formation increased with MAIB concentration. Thermal polymerization of styrene (St) in the presence of resulting poly(MMA) seemed to yield a starlike copolymer carrying poly(MMA) and poly(St) arms. The results ( r1 = 0.53, r2 = 0.56) of copolymerization of MMA and St with MAIB at 60°C in the presence of C 60 (7.15 × 10 −5 mol/L) were similar to those ( r1 = 0.46, r2 = 0.52) in the absence of C 60. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2905–2912, 1998 相似文献
16.
Closely positioned donor–acceptor pairs facilitate electron‐ and energy‐transfer events, relevant to light energy conversion. Here, a triad system TPACor‐C 60 , possessing a free‐base corrole as central unit that linked the energy donor triphenylamine ( TPA ) at the meso position and an electron acceptor fullerene (C 60) at the β‐pyrrole position was newly synthesized, as were the component dyads TPA‐Cor and Cor‐C 60 . Spectroscopic, electrochemical, and DFT studies confirmed the molecular integrity and existence of a moderate level of intramolecular interactions between the components. Steady‐state fluorescence studies showed efficient energy transfer from 1 TPA* to the corrole and subsequent electron transfer from 1corrole* to fullerene. Further studies involving femtosecond and nanosecond laser flash photolysis confirmed electron transfer to be the quenching mechanism of corrole emission, in which the electron‐transfer products, the corrole radical cation ( Cor ?+ in Cor‐C 60 and TPA‐Cor ?+ in TPACor‐C 60 ) and fullerene radical anion (C 60??), could be spectrally characterized. Owing to the close proximity of the donor and acceptor entities in the dyad and triad, the rate of charge separation, kCS, was found to be about 10 11 s ?1, suggesting the occurrence of an ultrafast charge‐separation process. Interestingly, although an order of magnitude slower than kCS, the rate of charge recombination, kCR, was also found to be rapid ( kCR≈10 10 s ?1), and both processes followed the solvent polarity trend DMF>benzonitrile>THF>toluene. The charge‐separated species relaxed directly to the ground state in polar solvents while in toluene, formation of 3corrole* was observed, thus implying that the energy of the charge‐separated state in a nonpolar solvent is higher than the energy of 3corrole* being about 1.52 eV. That is, ultrafast formation of a high‐energy charge‐separated state in toluene has been achieved in these closely spaced corrole–fullerene donor–acceptor conjugates. 相似文献
17.
Modeling of the addition of various radicals to C 60 fullerene is currently an active research area. However, the radicals considered are not able to adequately model polymeric radicals. In this work, we have performed a theoretical study of the possible reactions of C 60 fullerene with 1‐n‐phenylpropyl radicals, which are used to model polystyrene radicals. Several possible ways of subsequent addition of up to four 1‐phenylpropyl radicals to C 60 have been analyzed, the structures of the intermediates have been defined and thermal properties, such as the activation enthalpies of the corresponding reactions, have been calculated using density functional theory with the approximation of PBE/3z. It is shown that the topology of the spin density distribution on the fullerenyl radical causes regioselectivity for further radical addition. According to the energetic characteristics of the reactions, we assume the possibility of formation of products of one‐, two‐, three‐, and four‐ addition of the growth radical to the fullerene core in radical polymerization of styrene in the presence of C 60 fullerene. © 2016 Wiley Periodicals, Inc. 相似文献
18.
A new mode for hydrogen adsorption and storage in single-wall carbon nanotubes is used, on the basis of laser excitation. Remember that this method has been useful to obtain, in the case of the fullerene C 60, many complex C 60-atoms or C 60-molecules, where atoms or molecular particles are trapped inside the C 60-molecules. We think this method might be important to store many hydrogen molecules inside carbon nanotubes. 相似文献
19.
The first systematic study of heterogeneous fullerene trifluoromethylation using an innovative gradient-temperature gas-solid reactor revealed a significant effect of CF 3I pressure on the conversion of C 60 and C 70 into trifluoromethylated products and on the range of fullerene(CF 3) n compositions that were obtained. The design of the reactor allowed us to lower the residence times of fullerene(CF 3) n species in the hot zone which resulted in the significant differences in relative isomeric distributions as compared to the earlier methods. For the first time, gram quantities of trifluoromethylated fullerenes were prepared using the new reactor, and the selective synthesis of a single-isomer C 60(CF 3) 2 was developed. The relative reactivity of C 70 as a CF 3 radical scavenger was found to be much lower than that of C 60, especially at an early radical addition stage, which led to the cost-efficient synthesis of C 60(CF 3) 2 from a fullerene extract. 相似文献
20.
We computationally study the transition process of a chiral difluorobenzo[c]phenanthrene (DFBcPh) molecule within non‐polar fullerene C 260 to explore the confinement effect. We find blue‐shifts in the infrared and Raman spectra of the molecule inside the fullerene relative to those of isolated systems. Six types of spectrum features of the molecule appear in the 0–60 cm ?1 band. Interestingly, the energy barrier of the chiral transformation of the molecule is elevated by 15.88 kcal mol ?1 upon the confinement by the fullerene, indicating improvement in the stability of the enantiomers. The protection by C 260 lowers the highest occupied molecular orbital energy level and lifts the lowest unoccupied molecular orbital energy level of the chiral molecule such that the chiral molecule is further chemically stabilized. We concluded that the confinement environment has an impact at the nanoscale on the enantiomer transformation process of the chiral molecule. 相似文献
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