Reactions of fullerenes with reactive methylene organophosphorus reagents: efficient synthesis of organophosphorus group substituted C60 and C70 derivatives

Treatment of C70 with cycloalkylaminomethylenebisphosphonates in the presence of NaH gave corresponding C70 dimers 1 in good yield, while the methanofullerenes, C70>CH(PO3Et2) (3) and C70>C(PO3Et2)2 (4) or C60>CH(PO3Et2) (5) and C60>C(PO3Et2)2 (6), were obtained, respectively, by the reaction of C70 or C60 with tetraethyl methylenediphosphonate in the presence of NaH. Diethyl cyanomethylphosphonate reacted with C60 or C70 under similar conditions to afford C60>C(PO3Et2)CN (7) and C70>C(PO3Et2)CN (8). Furthermore, the presence of weak electronic interactions between two fullerene cages of fullerene dimers was demonstrated by cyclic voltammetry. A radical mechanism was proposed for the formation of the fullerene derivatives on the basis of the ESR studies.     

Controlling the confinement and alignment of fullerene C(70) in para-substituted calix[5]arenes

In toluene fullerene C(70) forms 2:1 complexes with p-benzylcalix[5]arene (1) and p-phenylcalix[5]arene (2), [C(70) subset1(2)].6(C(7)H(8)) and [C(70) subset2(2)].7(C(7)H(8)). The fullerene molecules are completely shrouded by two calix[5]arenes in addition to terminal benzyl groups from other supermolecules, [C(70) subset1(2)], and solvent. Within the capsule-like supermolecules the calixarenes have distinctly different arrangements relative to the principal axis of the fullerene; for [C(70) subset1(2)].6(C(7)H(8)) the oxygen planes of the two calixarenes are skewed by 37.0 and 47.5 degrees , whereas in [C(70) subset2(2)].7(C(7)H(8)) the principal axes of the fullerene and the two encapsulating calixarenes are more closely aligned with the corresponding angles at 9.7 and 8.6 degrees , and features a pentaphenyl inter-calixarene embrace. The Hirshfeld surfaces of these two complexes have been investigated for a detailed understanding of the orientation and nature of interactions of C(70) with the cavitand-type molecules and toluene.     

Monoalkylation of C60 and C70 with Zn and active alkyl bromides

We report a convenient and simple solution-phase electron-transfer reaction of C(60) with zinc and alpha-bromoacetonitrile, alpha-bromo acetate esters, allyl bromide, benzyl bromide and alpha-bromo ketones in DMF, with which different types of monoalkylated C(60) derivatives can be prepared. When this method is employed with C(70), 2-carbomethoxymethyl-1,2-dihydro[70]fullerene (isomer 5a) is produced as one of the two 1,2-monoalkylated C(70) isomers, together with the first 5,6-monoalkylated C(70) derivative.     

The electrochemical reduction of fullerenes, C60 and C70

The hexaanion of fullerene, C(60)(6-), was obtained in 1:5 (v/v) acetonitrile-toluene mixture with a mercury hemispherical ultramicroelectrode as a working electrode at a temperature of up to 30 degrees C. The C(70)(6-) ion also can be observed under the same conditions. The differences between the redox potentials of C(60) relative to C(70) indicate that it is easier to add electrons to C(70) and its anions compared to the counterparts of C(60). The results show that the mercury electrode is very suitable for investigation of the properties of the electrochemical reduction for the fullerenes, particularly C(60), at room temperature.     

A highly C70 selective shape-persistent rectangular prism constructed through one-step alkyne metathesis

Dynamic covalent chemistry (DCC) provides an intriguing and highly efficient approach for building molecules that are usually thermodynamically favored. However, the DCC methods that are efficient enough to construct large, complex molecules, particularly those with three-dimensional (3-D) architectures, are still very limited. Here, for the first time, we have successfully utilized alkyne metathesis, a highly efficient DCC approach, to construct the novel 3-D rectangular prismatic molecular cage COP-5 in one step from a readily accessible porphyrin-based precursor. COP-5 consists of rigid, aromatic porphyrin and carbazole moieties as well as linear ethynylene linkers, rendering its shape-persistent nature. Interestingly, COP-5 serves as an excellent receptor for fullerenes. It forms 1:1 complexes with C(60) and C(70) with association constants of 1.4 × 10(5) M(-1) (C(60)) and 1.5 × 10(8) M(-1) (C(70)) in toluene. This represents one of the highest binding affinities reported so far for purely organic fullerene receptors. COP-5 shows an unprecedented high selectivity in binding C(70) over C(60) (K(C70)/K(C60) > 1000). Moreover, the binding between the cage and fullerene is fully reversible under the acid-base stimuli, thus allowing successful separation of C(70) from a C(60)-enriched fullerene mixture (C(60)/C(70), 10/1 mol/mol) through the "selective complexation-decomplexation" strategy.     

Distribution of C60 and C70 fullerenes in the extraction system (C60 + C70)-α-pinene-ethanol-H2O

The distribution of C₆₀ and C₇₀ fullerenes in the extraction system (C₆₀ + C₇₀)-α-pinene-ethanol-H₂O was studied at constant C₆₀ to C₇₀ ratio and variable total fullerene concentration at 25°C. The relationship between the C₆₀ and C₇₀ content in ethanol (I) and α-pinene (II) phases is nonlinear over the entire fullerene concentration range.     

Preparation, crystallographic characterization and theoretical study of C70(CF3)16 and C70(CF3)18

C70(CF3)16 and C70(CF3)18, the first trifluoromethylated fullerene derivatives to comprise a pair of adjacent CF3 groups, have been isolated from a mixture obtained via reaction of C70 with CF3I, characterized in a single crystal XRD study and theoretically investigated at the DFT level of theory.     

Association and orientation of C70 on complexation with calix[5]arene

Calix[5]arene and C70 in p-xylene form a ball-and-socket supramolecular complex with the C5 axis of the fullerene tilted 40 degrees relative to the symmetry axis of the calixarene, the extended structure is comprised of well-separated zigzag sheets of C70 molecules.     

Novel synthesis and characterization of five isomers of (C(70))(2) fullerene dimers.

The synthesis and characterization of dimers and polymers, wherein two or more cages are linked, represent an important frontier in the chemistry of fullerene derivatives. A simple and novel method that requires no special apparatus has been developed for the dimerization of [70]fullerene to (C70)2. Upon grinding [70]fullerene in a mortar and pestle in the presence of K2CO3, five structural isomers of (C70)2 have been produced. These isomers are separated from one another via high performance liquid chromatography and are characterized by 13C NMR, UV-vis-NIR absorption and mass spectroscopy.     

Synthesis and photoinduced energy- and electron-transfer processes of C60-oligothienylenevinylene-C70 dumbbell compounds

Unsymmetric dumbbell molecules based on N-methylpyrrolidine[60]fullerene, oligothienylenevinylenes (nTV; n=2, 4), and N-methylpyrrolidine[70]fullerene, namely, C(60) -nTV-C(70) were synthesized and their photophysical properties were studied. In nonpolar solvents, photoinduced energy-transfer process predominantly takes place from the singlet excited state of nTV to C(60) and C(70) , as was confirmed by time-resolved emission and transient absorption spectroscopy. In polar solvent, charge-separation processes take place instead of energy transfer. The generated charge-separated radical-ion pairs decay to the neutral molecules by a fast charge-recombination process; for n=4, a rate constant of 2×10(7) s(-1) and lifetime of 50 ns were evaluated.     

Relative partial cross sections for single, double, and triple photoionization of C60 and C70

Partial cross sections for the photoion formation from C(60) and C(70) were determined from the yields of singly, doubly, and triply charged ions which were measured by mass spectrometry combined with tunable synchrotron radiation at hnu = 25-120 eV. The dependence of the detection efficiencies on the mass-to-charge ratio was evaluated by using the formula proposed by Twerenbold et al. Corrections of the detection efficiency were found to be critical for obtaining accurate partial cross sections for photoionization of fullerenes. Revisions were made of the partial cross-section curves for single and double photoionization of C(60) and C(70). The curve for triple photoionization of C(70) was newly proposed. The ratios between the cross sections for double and single photoionization increase with hnu and reach saturated values of 0.78 at 85 eV for C(60) and approximately 1.3 at 100 eV for C(70). In contrast, the ratios at 120 eV between the cross sections for triple and single photoionization of C(60) and C(70) amount to 0.14 and approximately 0.38, respectively. The formation mechanism of multiply charged fullerene ions was discussed in terms of valence-electron excitation to antibonding unoccupied orbitals and/or spherical standing waves inside the cavity of a fullerene. This excitation could be followed by Spectator Auger processes and transmission of the excess electronic energy among numerous vibrational degrees of freedom.     

Determination of binding strength for the supramolecular complexation of a designed bisporphyrin with C60, C70 and their derivatives employing absorption spectrophotometric, fluorescence and quantum chemical calculations

The present paper reports the synthesis of a designed bisporphyrin (1), and its supramolecular complexes with C60, C70 and their derivatives, namely, tert-butyl-(1,2-methanofullerene)-61-carboxylate (2) and [6,6]-phenyl C70 butyric acid methyl ester (3) in toluene medium. C60, C70 and their derivatives undergo ground state non-covalent interaction with 1 is evidenced from absorption spectrophotometric study in which it is observed that the intensity of the Soret absorption band of 1 decreases considerably in presence of C60, C70 and their derivatives. Steady state fluorescence studies reveal efficient quenching of fluorescence of 1 in presence of fullerenes. The binding constant (K) values of the fullerene/1 complexes follows the trend: 2/1相似文献   

Gate-controlled rectifying behavior in C70@SWNT networks

We report the gate-controlled rectification behavior in C(70)@SWNT networks at room temperature in air. The electrical transport characteristics can be fitted well with the conventional Schottky diode model. The origin of the rectifying behavior in fullerene peapod networks device is qualitatively discussed. This paper demonstrates a strategy for diode fabrication based on peapod networks.     

C2 C70F38 is aromatic, contains three planar hexagons, and has equatorial addends

Single crystal X-ray analysis shows the main (C(2)) isomer of C(70)F(38) to contain three planar delocalised aromatic hexagons (two equivalent and one centred on the C(2) axis), together with seven C[double bond, length as m-dash]C bonds (three pairs and one straddling the C(2) axis); C(70)F(38) is the first high addition level [70]fullerene derivative to be fully characterised, is the first to have equatorial addends, and is calculated to have high stability.     

C70(OsO4Py2)3配合物的合成和表征

自从1985年Kroto等[1,2]发现富勒烯(球烯)以来,在化学、物理和材料等领域逐渐地形成了富勒烯的研究热潮,现在人们正将较多注意力投向富勒烯的各类衍生物结构与性能之间内在联系规律的研究,以期望在开发应用方面取得更大的进展,为此也更加重视对具有特殊组成与结构的富勒烯衍生物的研究.本文首次合成并表征了C70(OsO4PY2)3配合物,推测了其可能的结构.     

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.     

Preparation and study of hydrides of fullerenes C60 and C70

Fullerene hydrides were prepared by hydrogenation of fullerences C₆₀ and C₇₀ using proton transfer from 9,10-dihydroanthracene to fullerene and were studied by mass spectrometry (electron impact, field desorption), IR, UV, and¹H and¹³C NMR spectroscopy. The main product of the hydrogenation of C₆₀ is C₆₀H₃₆, which is sufficiently stable. Hydrogenation of fullerene C₇₀ gives a series of polyhydrides C₇₀H _n (n=36–46), and the main product is C₇₀H₃₆. The dehydrogenation of C₆₀H₃₆ by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone is not quantitative and results in the formation of fullerene derivatives along with C₆₀. The comparison of the IR and¹H and¹³C NMR spectral data for solid C₆₀H₃₆ with the theoretical calculations suggests that the fullerene hydride has aT-symmetric structure and contains four isolated benzenoid rings located at tetrahedral positions on the surface of the closed skeleton of the molecule. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 4, pp. 671–678, April, 1997.     

Synthesis and reaction of fullerene C70 encapsulating two molecules of H2

New endohedral fullerene C(70) encapsulating one and two H(2) molecule(s) has been synthesized by organic reactions, the so-called "molecular surgery" method, and the first organic derivatization of H(2)@C(70) and (H(2))(2)@C(70) has been conducted. Although the interaction between inner H(2) and outer C(70) is rather weak, (H(2))(2)@C(70) exhibits smaller equilibrium constants in the Diels-Alder reaction with 9,10-dimethylanthracene than those of H(2)@C(70).     

Microwave-assisted extraction of C60 and C70 from fullerene soot

Microwave-assisted extraction (MAE) was examined as an alternative to the traditional Soxhlet method of extracting C₆₀ and C₇₀ from fullerene soot. MAE of 0.20 g of fullerene soot with 95:5 toluene–acetonitrile yielded greater than 7.8 mg of C₆₀ and greater than 0.54 mg of C₇₀ in 4 min with no further increase in yield after 30 min of irradiation. By comparison, exhaustive Soxhlet extraction of the same size sample with the same solvent yielded 7.1 mg of C₆₀ and 0.58 mg of C₇₀ in 340 min. Reextraction by MAE of soot initially extracted by Soxhlet increased the yield of Soxhlet alone. Although MAE was limited to less than 0.5-g sample per extraction vessel, multiple samples were extracted with minimal increased extraction time and no reduction in the amount of material recovered.     

Facile synthesis of a flexible tethered porphyrin dimer that preferentially complexes fullerene C70

A simple, high yield, two-step synthesis yields a porphyrin dimer linked by a flexible dithiol tether that preferentially binds fullerene C(70) over C(60) in toluene solution. The complex forms stable aggregates when cast on glass.