共查询到20条相似文献,搜索用时 55 毫秒
1.
Deza M Fowler PW Rassat A Rogers KM 《Journal of chemical information and computer sciences》2000,40(3):550-558
If a fullerene is defined as a finite trivalent graph made up solely of pentagons and hexagons, embedding in only four surfaces is possible: the sphere, torus, Klein bottle, and projective (elliptic) plane. The usual spherical fullerenes have 12 pentagons; elliptic fullerenes, 6; and toroidal and Klein-bottle fullerenes, none. Klein-bottle and elliptic fullerenes are the antipodal quotients of centrosymmetric toroidal and spherical fullerenes, respectively. Extensions to infinite systems (plane fullerenes, cylindrical fullerenes, and space fullerenes) are indicated. Eigenvalue spectra of all four classes of finite fullerenes, are reviewed. Leapfrog fullerenes have equal numbers of positive and negative eigenvalues, with 0, 0, 2, or 4 eigenvalues zero for spherical, elliptic, Klein-bottle, and toroidal cases, respectively. 相似文献
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This paper is a tutorial review of the host-guest chemistry of fullerenes and metalloporphyrin. Among various host molecules for fullerenes, cyclic hosts composed of metalloporphyrin moieties possess one of the highest affinities toward fullerenes, which can be widely tuned simply by changing the central metal ions of the porphyrin moieties. Inclusion of fullerenes occurs not only by van der Waals interactions but also, in some cases, via pi-electronic charge-transfer from the host metalloporphyrin moieties to the guest fullerenes. Fullerenes such as C(120), upon inclusion with cyclic metalloporphyrin dimers, show an oscillatory motion within the host cavity, whose frequency reflects the solvation/desolvation dynamics of the fullerenes. A molecularly engineered metalloporphyrin host with a self-assembling capability allows a guest-directed formation of a supramolecular peapod, where included fullerenes, as peas, are aligned along the self-assembled metalloporphyrin nanotube, as a pod. Furthermore, certain metalloporphyrin hosts are applicable to the selective extraction of low-abundance higher fullerenes from an industrial production source and also allow spectroscopic discrimination of chiral fullerenes. 相似文献
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The aggregation behavior of C60 fullerenes and C60 fullerenes with six symmetrically tethered poly(ethylene oxide) oligomers [(PEO)-6-C60] in aqueous solutions has been studied using implicit solvent molecular dynamics simulations. Our simulations reveal that while the attraction between two (PEO)-6-C60 fullerenes in aqueous solution is stronger and longer range than that between two bare C60 fullerenes, the (PEO)-6-C60 fullerenes do not phase-separate in water but rather aggregate in chain-like clusters at concentrations where unmodified fullerenes completely phase-separate. 相似文献
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N. I. Alekseev N. A. Charykov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(2):268-276
A joint analysis of fullerene assembly kinetics and gas flow dynamics in an arc chamber for the production of fullerenes showed
that the effective annealing of fullerenes and the evident dominance of “magic” fullerenes C60 and C70 were mainly explained by the difference between the thermal dissociation rates of these and less stable C62 and C68 fullerenes. The percent of “nonmagic” fullerenes was also shown to depend on the structure of the gas flows formed in the
arc discharge chamber. The majority of newly formed fullerenes were not immediately removed from the chamber, bur were trapped
by closed gas flows. Back in the hot region of the chamber, fullerenes were simultaneously annealed and dissociated under
the action of high temperature and, partially, UV radiation. The “nonmagic” fullerenes were most actively suppressed in a
non-pumpable discharge chamber. 相似文献
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V. I. Sokolov 《Russian Journal of Coordination Chemistry》2007,33(10):711-724
Fullerenes are considered as ligands in transition metal π-complexes. The following aspects are discussed: metals able to form complexes with fullerenes; haptic numbers; homo-and heteroligand complexes; ligand compatibility with fullerenes for different metals, including fullerenes with a disturbed structure of conjugation. 相似文献
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We calculated the partitioning of pi-electrons within individual pentagonal and hexagonal rings of fullerenes for a collection of fullerenes from C20 to C72 by constructing their Kekulé valence structures and averaging the pi-electron content of individual rings over all Kekulé valence structures. The resulting information is collected in Table 2, which when combined with the Schlegel diagram of fullerenes (illustrated in Figure 7) uniquely characterizes each of the 19 fullerenes considered. The results are interpreted as the basic information on the distributions (variation) of the local (ring) pi-electron density. 相似文献
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An integrated technology for manufacture of fullerenes was developed. It includes the following stages: synthesis of a fullerene black, extraction of a mixture of fullerenes from the black, preliminary separation of the mixture into concentrates enriched in C60 and C70 fullerenes, and production of C60 and C70 fullerenes of purity exceeding 99.5 and 98.0 wt %, respectively, from the concentrates. 相似文献
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采用二硫化碳重结晶富勒烯混合物或二硫化碳二次抽提烟灰以提取高富勒烯(higherfulerenes,Cn,n>70)。产物经高效液相色谱分析,高富勒烯的含量从1%分别提高到4%和6%;经激光飞行时间质谱证明,产物中除含主要成分C60和C70以外,还含有C76、C78、C82、C84以及更高碳原子的富勒烯。 相似文献
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Molecular-dynamics simulations of a single C(60) fullerene and pairs of C(60) fullerenes in aqueous solution have been performed for the purpose of obtaining improved understanding of the nature of solvent-induced interactions between C(60) fullerenes in water. Our simulations reveal repulsive solvent-induced interactions between two C(60) fullerenes in aqueous solution in contrast to the associative effects observed for conventional nonpolar solutes. A decomposition of the solvent-induced potential of mean force between fullerenes into entropy and energy (enthalpy) contributions reveals that the water-induced repulsion between fullerenes is energetic in origin, contrasting strongly to entropy-driven association observed for conventional nonpolar solutes. The dominance of energy in the solvent-induced interactions between C(60) fullerenes arises primarily from the high atomic density of the C(60) molecule, resulting in strong C(60)-water van der Waals attraction that is reduced upon association of the fullerenes. The water-induced repulsion is found to decrease with increasing temperature due largely to an increasing contribution from a relatively weak entropy-driven association. 相似文献
14.
富勒烯合成化学研究进展 总被引:2,自引:0,他引:2
富勒烯是一类由12个五元环和若干六元环组成的笼状分子, 自20世纪80年代中期被发现以来就以其独特的结构和新奇的性质而成为科学界研究的热点, 25年来, 无论在基础研究还是在实际应用领域都有了长足的进步, 人们在发展富勒烯合成新方法和寻找富勒烯新结构方面做了大量的工作。本文对富勒烯的各种宏量合成方法进行了回顾, 并概述了迄今已发表的60余种富勒烯新结构,包括各种富勒烯空笼、内嵌富勒烯、富勒烯笼外修饰衍生物及氮杂富勒烯等结构。 相似文献
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Yamaguchi T Ishii N Tashiro K Aida T 《Journal of the American Chemical Society》2003,125(46):13934-13935
An acyclic dimer of a dendritic zinc porphyrin bearing six carboxylic acid functionalities (1acid) interacts with fullerenes, such as C60 and C70, to form "supramolecular peapods", composed of a hydrogen-bonded zinc porphyrin nanotube and fullerenes (3). According to TEM, the peapods are very long (>1 mum) and have a uniform diameter of 15 nm. Without fullerenes, the zinc porphyrin dimer forms only a heavily entangled, irregular assembly. In contrast with 1acid, an ester version of the acyclic dimer without hydrogen-bonding capability (1ester) hardly interacts with fullerenes. 相似文献
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A new supramolecular host with good affinity toward fullerenes has been developed. This host having a tweezer-like shape is built on a [3]rotaxane scaffold and contains two free-base porphyrin moieties as recognition units for fullerenes. The ability of this tweezer to bind fullerenes strongly depends on the solvent system used and the size of fullerene. 相似文献
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Nino Bašić Gunnar Brinkmann Patrick W. Fowler Tomaž Pisanski Nico Van Cleemput 《Journal of mathematical chemistry》2017,55(8):1669-1682
Stability and chemistry, both exohedral and endohedral, of fullerenes are critically dependent on the distribution of their obligatory 12 pentagonal faces. It is well known that there are infinitely many IPR-fullerenes and that the pentagons in these fullerenes can be at an arbitrarily large distance from each other. IPR-fullerenes can be described as fullerenes in which each connected cluster of pentagons has size 1. In this paper we study the combinations of cluster sizes that can occur in fullerenes and whether the clusters can be at an arbitrarily large distance from each other. For each possible partition of the number 12, we are able to decide whether the partition describes the sizes of pentagon clusters in a possible fullerene, and state whether the different clusters can be at an arbitrarily large distance from each other. We will prove that all partitions with largest cluster of size 5 or less can occur in an infinite number of fullerenes with the clusters at an arbitrarily large distance of each other, that 9 partitions occur in only a finite number of fullerene isomers and that 15 partitions do not occur at all in fullerenes. 相似文献
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In the field of open-cage fullerenes, there was a lack of a universal standard that could correlate and quantify the orifice size of open-cage fullerenes. One cannot compare the relative orifice size by simple comparison of the number of atoms that composes the orifice. We present a general term for easy estimation of relative orifice size by defining an index for open-cage fullerenes. We estimated the corresponding effective areas A(area) for orifices of open-cage fullerenes by matching calculated activation energies Ea(calcd) for hydrogen release from open-cage fullerenes (B3LYP/6-31G**//B3LYP/3-21G) to the computed energies required for a hydrogen molecule passing through a cyclo[n]carbon ring. Then we define an index K(orifice) based on experimental hydrogen release rate, where K(orifice) = ln k/k degrees (k is rate constant of hydrogen-release rate of any open-cage fullerenes taken for comparison at 160 degrees C; k degrees is the hydrogen release rate from H2@4a taken as the standard compound). We synthesized several open-cage fullerenes and studied kinetics of a set of H2-encapsulated open-cage fullerenes to evaluate their K values. A correlation of the index K(orifice) with the effective areas A(area) showed a good linear fit (r2 = 0.972) that demonstrated a good interplay between experiment and theory. This allows one to estimate K(orifice) index and/or relative rate k of hydrogen release through computing activation energy Ea(calcd) for a designed open-cage fullerene. 相似文献
20.
Giorgio De Luca Marlon Basantes Valverde Matilde Morrone Lorenzo S. Caputi 《International journal of quantum chemistry》2019,119(10):e25890
Multi-shell fullerenes are widely studied for their interesting properties although comparative studies on single- and multi-shell structures remain scarce. In this work, important electronic features of single- and double-shell icosahedral fullerenes as a function of their sizes were calculated in the framework of the density functional theory. Fully optimized structures were used to get the gap between the highest occupied molecular and the lowest unoccupied molecular orbital (H-L gap), electronegativity, softness and density of the electronic states. This work shows that the H-L gap of the single-shell fullerenes decreases nonlinearly as the nanoparticles size increases, whereas for the double-shell fullerenes an opposite trend is obtained. A decrease of the H-L gap is found going from single- to double-shell fullerenes with similar external sizes, up to a diameter of 3.13 nm. The electron density of states revealed that isolated peaks give way to more dense electronic states for nanoparticles with diameters above 2 nm. 相似文献