- Anion-π Catalysis on Fullerenes
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Anion-π interactions on fullerenes are about as poorly explored as the use of fullerenes in catalysis. However, strong exchange-correlation contributions and the localized π holes on their surface promise unique selectivities. To elaborate on this promise, tertiary amines are attached nearby. Dependent on their positioning, the resulting stabilization of anionic transition states on fullerenes is shown to accelerate disfavored enolate addition and exo Diels-Alder reactions enantioselectively. The found selectivities are consistent with computational simulations, particularly concerning the discrimination of differently planarized and charge-delocalized enolate tautomers by anion-π interactions. Enolate-π interactions on fullerenes are much shorter than standard π- π interactions and anion-π interactions on planar surfaces, and alternative cation-π interactions are not observed. These findings open new perspectives with regard to anion-π interactions in general and the use of carbon allotropes in catalysis.
- López-Andarias, Javier,Frontera, Antonio,Matile, Stefan
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- Photophysical and nonlinear optical properties of [60]fullerene derivatives
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A systematic spectroscopic study of a series of C60 derivatives with different cage functionalizations is reported. The absorption spectra and absorptivities of the derivatives in solution were measured and compared. By recording the fluorescence spectra using a near-infrared-sensitive emission spectrometer (extending to 1200 nm), fluorescence quantum yields of the derivatives were determined quantitatively. Fluorescence lifetimes of the derivatives were obtained using the time-correlated single photon counting technique. The results show that both fluorescence quantum yields and lifetimes are rather similar for the different classes of C60 derivatives. The nonlinear absorptive properties of the derivatives were evaluated by optical limiting measurements in solution and in polymer film using the second harmonic of a Q-switched Nd:Yag laser at 532 nm. Effects of different fullerene cage functionalizations on the photophysical properties and optical limiting responses of the C60 derivatives are discussed.
- Sun, Ya-Ping,Lawson, Glenn E.,Riggs, Jason E.,Ma, Bin,Wang, Naixing,Moton, Dwella K.
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- The use of solid phase synthesis for the preparation of monoadducts of fullerene C60
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The method of solid phase synthesis was proposed for the preparation of monoadducts of fullerene C60 using 3′H-cyclopropa[1,9](C 60-I h )[5,6]fullerene-3′-carboxylic acid as an example.
- Nikolaev,Klimenicheva, Yu. S.,Davidovich,Piotrovskii
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- Synthesis of fullerene C60monoadducts. Cyclopropanation of C60with sulfonium ylides
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3′H-Cyclopropa[1,9](C60-Ih)[5,6]fullerene-3′-carboxylic acid can be synthesized in a good yield by cyclopropanation of fullerene C60with 2-(dimethyl-λ4-sulfanylidene)acetates provided that the ester residue is readily hydrolyzable in acid medium.
- Nikolaev,Davidovich,Piotrovskii
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p. 1050 - 1053
(2016/09/04)
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- Toward controlled spacing in one-dimensional molecular chains: Alkyl-chain-functionalized fullerenes in carbon nanotubes
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A range of fullerenes (C60) functionalized with long alkyl chains have been synthesized and inserted into single-walled carbon nanotubes. The impact of the alkyl chain length and of the type of linker between the addend and the fullerene cage on the geometry of molecular arrays in nanotube has been studied by high-resolution transmission electron microscopy. In the presence of functional groups the mean interfullerene separations are significantly increased by 2-8 nm depending on the length of the alkyl chain, but the periodicity of the fullerene arrays is disrupted due to the conformational flexibility of the alkyl groups.
- Chamberlain, Thomas W.,Camenisch, Andrew,Champness, Neil R.,Briggs, G. Andrew D.,Benjamin, Simon C.,Ardavan, Arzhang,Khlobystov, Andrei N.
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p. 8609 - 8614
(2008/02/09)
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- Synthesis and reactions of 2,2-[60]fullerenoalkanoyl chlorides
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2,2-[60]Fullerenoalkanoyl chlorides (1a-d) were easily and securely prepared from the corresponding 2,2-[60]fullerenoalkanoic acids (2a-d) by the reaction with thionyl chloride in an unusual mixed solvent, CH 2Cl2/dioxane. The characterization of 1a-d by 1H and 13C NMR, FT-IR, and MALDI-TOF-MASS was conducted for the first time. The 2,2-[60]fullerenoalkanoyl chlorides thus obtained were readily converted to the corresponding amides and esters in moderate to excellent yields by the condensation with amines and alcohols, respectively. Upon applying the condensation, [60]fullerene-biomolecule hybrids were easily prepared.
- Tada, Tomoyuki,Ishida, Yasuhiro,Saigo, Kazuhiko
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p. 1633 - 1639
(2007/10/03)
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- [60]Fullerenoacetyl chloride as a versatile precursor for fullerene derivatives: Efficient ester formation with various alcohols
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(Matrix presented) [60]Fullerenoacetyl chloride, one of the reactive derivatives of [60]fullerenoacetic acid, was isolated and identified for the first time. This acid chloride was easily synthesized in good yield from tert-butyl [60]fullerenoacetate through two steps. In the presence of 4-(dimethylamino)-pyridine as a base, the acid chloride smoothly reacted with various alcohols under mild conditions to give the corresponding esters including [60]fullerene-biomolecule hybrids in moderate to high yields.
- Ito, Hiroshi,Tada, Tomoyuki,Sudo, Masafumi,Ishida, Yasuhiro,Hino, Tetsuo,Saigo, Kazuhiko
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p. 2643 - 2645
(2007/10/03)
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- 176. Structures and Chemistry of Methanofullerenes: A Versatile Route into N--Substituted Amino Acids
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The reaction of C60 with oxadiazole 13 afforded the dimethoxymethanofullerene 7 in 32 percent yields as a 6-6-ring-bridged isomer with a closed transannular bond.A literature survey showed that all 6-6-ring-bridged methanofullerenes are ?-homoaromatic with a closed transannular bond (6-6-closed) and all 6-5-ring-bridged are ?-homoaromatic with an open transannular bond (6-5-open).The preference for 6-6-closed and 6-5-open structures is not due to substituent effects but is best explained with the conservation in these isomers of the favorable bonding seen in C60 with higher double- bond character at 6-6-bonds and higher single-bond character at 6-5-bonds.Reaction of C60 with diazo diester 15 gave the fullerene diester 14 which was hydrolyzed with BBr3 in benzene to the methanofullerenecarboxylic acid 10, a versatile synthon for the preparation of amphiphilic fullerene derivatives.Treatment of 10 with alcohols and amino acid esters under DCC coupling conditions afforded the esters 5 and 17 and the amino-acid derivatives 11 and 12, respectively.
- Isaacs, Lyle,Diederich, Francois
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p. 2454 - 2464
(2007/10/02)
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