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Fullerene
About: Fullerene is a research topic. Over the lifetime, 12723 publications have been published within this topic receiving 359173 citations.
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TL;DR: Differences between the NICSs calculated at the center of the fullerene carbon cages and the experimental chemical shifts of encapsulated NMR-active nuclei as well as experimental shieldings observed for different encapsulated nuclei were able to be understood readily for the first time.
Abstract: Endohedral and external through-space NMR shieldings (TSNMRS) and the magnetic susceptibilities of the fullerene carbon cages of C50, C60, C60-6, C70, and C70-6 were assessed by ab initio molecular orbital calculations. Employing the nucleus-independent chemical shift (NICS) concept, these TSNMRS were visualized as isochemical shielding surfaces (ICSS) and were applied to quantitatively estimate either the aromaticity or the anti-aromaticity on the fullerene surface pertaining to the five- or six-membered ring moieties and the shielding of any nuclei enclosed within the carbon cages. Differences between the NICSs calculated at the center of the fullerene carbon cages and the experimental chemical shifts of encapsulated NMR-active nuclei as well as experimental shieldings observed for different encapsulated nuclei were able to be understood readily for the first time.
77 citations
TL;DR: In this article, first principles calculations of Si-doped heterofullerenes C59Si and C58Si2, obtained from C60 by replacing one and two C atoms with Si atoms, were performed.
Abstract: Si-doped heterofullerenes C59Si and C58Si2, obtained from C60 by replacing one and two C atoms with Si atoms, are investigated via first principles calculations. Static geometry optimizations show that structural deformations occur in the vicinity of the dopant atoms and give rise to Si–C bonds significantly larger than the ordinary C–C bonds of the fullerene cage. In the case of C58Si2, the lowest energy isomer has two Si atoms located at distances corresponding to third nearest neighbors. The electronic structure of these heterofullerenes, although globally close to that of C60, is characterized by a strong localization of both the HOMO’s and the LUMO’s on the Si sites. Charge transfer occurs from the dopant atoms to the nearest neighbor C atoms, contributing to the formation of polar Si–C bonds. A detailed analysis of the charge localization, based on the electron localization function and maximally localized Wannier function approaches, reveals that the bonding of Si in the fullerene cage consists of ...
77 citations
TL;DR: Noncovalent interactions between purified HiPCO single-wall carbon nanotubes (SWNT) and a [60]fullerene-pyrene dyad, synthesized through a regioselective double-cyclopropanation process, produce stable suspensions in which the tubes are very well dispersed, as evidenced by microscopy characterization.
Abstract: Noncovalent interactions between purified HiPCO single-wall carbon nanotubes (SWNT) and a [60]fullerene-pyrene dyad, synthesized through a regio-selective double-cyclopropanation process, produce stable suspensions in which the tubes are very well dispersed, as evidenced by microscopy characterization. Cyclic voltammetry experiments and photophysical characterization of the suspensions in organic solvents are all indicative of sizeable interactions of the pyrene moiety with the SWNT and, therefore, of the prevalence in solution of [60]fuller-ene-pyrene-SWNT hybrids.
77 citations
TL;DR: In this paper, the authors present a discussion of recent concepts for the construction of a spin quantum computer using endohedral fullerenes, and discuss the probable properties of such registers and different strategies to use them in a quantum computer design, including gating and readout methods.
Abstract: We present a discussion of recent concepts for the construction of a spin quantum computer using endohedral fullerenes. The fullerene molecule is a static, room-temperature trap for atoms with slowly relaxing electron andnuclear spins. The fullerene "containers" can be used to arrange the spins in complex structures such as a linear chain, to form a spin quantum register. We discuss the probable properties of such registers and different strategies to use them in a quantum computer design, including gating and read-out methods.
77 citations
TL;DR: Achiba et al. as discussed by the authors used F NMR spectroscopy to determine that an enriched sample of C90 contained five isomers: one with C 2v symmetry, three with C2 symmetry, and one with 1 symmetry.
Abstract: Since the macroscopic synthesis of C60 and C70 in 1990, [1] the fullerene family has drawn attention with potential applications in a wide range of scientific and industrial areas. C60, C70, C76, C78, and C84 have become well-known; however, the carbon soot from arc generators contains small amounts (generally less than 1%) of higher fullerenes. The isolation of these higher fullerenes in isomerically pure form is challenging, especially since the number of isomers that follow the isolated-pentagon rule (IPR) increases as the size of the fullerene cage expands. The isolated-pentagon rule requires that each pentagon be surrounded by five hexagons to avoid strain-inducing pentagon–pentagon contact. There are 46 isomers of C90 that obey the IPR, but none of these has been obtained in pure form. In regard to unfunctionalized C90, Achiba et al. utilized C NMR spectroscopy to determine that an enriched sample of C90 contained five isomers: one with C2v symmetry, three with C2 symmetry, and one with C1 symmetry. [3] Shi and co-workers reported the separation andUV/Vis spectra of two isomers of C90 from arcgenerated carbon soot obtained from ytterbium-doped graphite rods. Several computational studies have been performed to better understand which specific isomers are expected to be stable. Slanina et al. concluded from semiempirical quantum-chemical calculations that the C2(45), C2v(46), Cs(35), C2(18), and C1(9) isomers are likely to be the most stable at the temperatures used for C90 production. [6] Computations at the B3LYP/6-31G level by Sun indicated that the C2(45) isomer was the most stable, and C2(28), C1(30), C1(32), Cs(35), C2(40), and C2v(46) were other stable isomers. [7] Watanabe et al. performed PM3 computations and concluded that there are 11 isomers (D5h(1), C1(27), C2(28), C1(29), C1(30), C1(31), C1(32), Cs(34), Cs(35),C2(45), andC2v(46)) that are kinetically as well as thermodynamically stable. Some adducts of C90 have also been structurally identified. Recently, a trifluoromethyl adduct of C90, C90(CF3)12, which was synthesized by the free-radical addition of CF3I to a mixture of higher fullerenes, was shown through F NMR spectroscopy to utilize the C1(32)-C90 cage. [9] The chlorination of a mixture of higher fullerenes through treatment with SbCl5 yielded a crystalline material containing C90Cl32. [10] Crystallographic analysis revealed that a single crystal contained a mixture of two isomers that utilized the C2v(46)-C90 and Cs(34)-C90 cages. Carbon soot was obtained by vaporizing a graphite rod filled with Sm2O3 and graphite powder in an electric arc as outlined previously. The carbon soot was extracted with o-dichlorobenzene, and the soluble extract was subjected to a multistage high pressure liquid chromatographic (HPLC) isolation process involving three complementary chromatographic columns (Buckyprep-M, Buckyprep, and 5PBB) with either chlorobenzene or toluene as the eluent. Three individual isomers of C90 were identified and purified. These isomers are labeled C90(I), C90(II), and C90(III) in the order of their chromatographic elution times. Figure 1 shows the HPLC chromatogram and laser desorption ionization time-of-flight (LDI-TOF) mass spectrum of the purified sample of the firsteluted isomer, C90(I). We obtained isomer-free C90(II) and C90(III) in a similar fashion (see the Supporting Information). C90(I) differs distinctly from C90(II) and C90(III) in terms of its retention time (Table 1). The unusually short retention time observed for C90(I) on the polar stationary phases of both the phenothiazine-derivatized Buckyprep-M and pentabromobenzyl (5PBB) columns suggested that it is less polar than C90(II) or C90(III), whereas the relatively long retention time on the nonpolar pyrenylethyl silica of the Buckyprep column suggested that C90(I) has a more elongated structure that enables better p–p interaction with the stationary phase. The three isomers of C90 display quite different UV/Vis/ near-infrared (NIR) absorption behavior (Figure 2). C90(I) produces two characteristic absorptions at 484 and 589 nm, whereas C90(II) exhibits a strong band with strong but poorly resolved peaks around 413 and 453 nm, and C90(III) shows an almost featureless spectrum with broad bands at 602 and [*] H. Yang, Z.-M. Wang, A. Jiang, Prof. Dr. Z.-Y. Liu Department of Chemistry, Zhejiang University Hangzhou 310027 (China) Fax: (+86)571-8795-1895 E-mail: zyliu@zju.edu.cn
76 citations