Radiochemical challenges in the study of endohedral fullerenes and MD simulation

The formation of atom-doped fullerenes has been investigated by using several types of radionuclides produced by nuclear reactions. From the trace of the radioactivities after high performance liquid chromatography (HPLC), it was found that formation of endohedral fullerenes (or heterofullerene) with small atoms (Be, Li), noble-gas atoms (Kr, Xe) and 4B–6B elements (Ge, As, Se, Sb, Te etc.) is possible by a recoil process following the nuclear reaction. In order to show the possibility of creating endohedral fullerenes by inserting a foreign atom with a suitably high kinetic energy into C₆₀, we have carried out large-scale ab initio molecular dynamics simulations on the basis of the all-electron mixed-basis approach with atomic orbitals and plane waves for Li, Be, N, O, Na, S, Cl, K, V, Cu, As, Se, Sb, Te, Kr, Xe. This revised version was published online in July 2006 with corrections to the Cover Date.     

Direct synthesis of radioactive carbon labeled fullerences using nuclear reactions

The¹¹C and¹⁴C labeled fullerenes were produced by charged-particle and neutron irradiation, of C₆₀, C₇₀ and their mixture. It was found that a carbon atom of fullerence can be easily exchanged with a radioactive carbon atom produced by a nuclear reaction. The HPLC method was effective for identification and purification of various labeled fullerene families as chemically stable compounds. The radiochemically interesting aspect of the results is not only the production of¹¹C and¹⁴C labeled fullerenes but also the formation of radioactive higher fullerenes which can be simultaneously produced with high yield and in carrier-free form.     

Construction and utilisation of planar graphs of two series of IPR fullerenes through the use of threefold rotational symmetry

Threefold rotational symmetry has been used to develop an algorithm for the construction of planar graphs of IPR fullerenes and to factorize their characteristic polynomials. Two series of fullerenes of the formula C_60+12n and C_60+18n have thus been obtained. The algorithm has been shown to be useful for predicting the nature of variation of the point groups of the fullerenes with increased n, for counting the number of ¹³C nuclear magnetic resonance (NMR) signals (along with their relative intensities), and also for obtaining a large part of their eigenspectra. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Quantum transition theory and dynamics of ionic molecule formation in cluster collisions

We apply the quantum transition theory of chemical reactions to ionic molecule formation in collisions between alkali-metal clusters and two types of reactive species: halogens and fullerenes. We show that the probability of a sticking collision is strongly dependent upon the nuclear dynamics. It turns out that although both halogens and fullerenes have a high electron affinity and appear promising for a harpooning reaction, this process is inhibited in the fullerene case by unfavorable Franck-Condon factors. This conclusion is in agreement with experimental observations. We predict that a strong reactive channel should reappear if the bare fullerene is replaced by a fullerene-rare gas complex. The product translational and vibrational energy distribution for such a collision is evaluated.     

Fullerenes as tilings of surfaces

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.     

A Dft Investigation of the Interaction of B- And Al-Doped C<Subscript>60</Subscript> Fullerenes with Cyclopropylpipezarine

Interactions and natural bond orbital analysis of cyclopropylpiperazine(cppp) and B- or Al-doped C₆₀ fullerenes are investigated by quantum mechanical calculations. The structural and electronic properties, such as NH stretching vibrations, nuclear magnetic shielding tensors of ²⁷Al and ¹¹B nuclei or the energy gap are also investigated. All calculations are carried out in the gas phase and water media. Results of the bond order and the binding energy suggest that chemisorption occurs between the cppp nitrogen atom and boron or aluminum atoms of fullerenes. The Alcomplex in water is foundto have the highest binding energy. Further, AlC₅₉…cppp complexes have a slightly higher kinetic stability and a low chemical reactivity. However, BC₅₉…cppp works as a function-type sensor for cppp.     

Metalloporphyrin hosts for supramolecular chemistry of fullerenes

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.     

Molecular dynamics simulation study of the role of evenly spaced poly(ethylene oxide) tethers on the aggregation of C60 fullerenes in water

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.     

富勒烯的化学研究进展

本文评述了富勒烯化学研究的新进展, 从[ 60 ]、[ 70 ]富勒烯的化学修饰、富勒烯金属包合物、掺杂富勒烯、碳纳米管以及富勒烯的化学合成等几个方面着重介绍了国际上富勒烯研究的热点, 对进一步研究的方向进行了讨论。     

煤基富勒烯烟灰萃取产物的质谱分析

用甲苯等有机溶剂对由煤制得烟灰(soot)进行索氏萃取，用时间飞行质谱及气相色谱-质谱联用（GCMS）技术对所得的萃取产物进行了分析，结果发现，煤基粗富勒烯中除含有大量的C60和C70外，高碳富勒烯（如C74、C78，C82、C84、C100及C106等）的丰度也较高。在煤基粗富勒烯的伴生副产物中存在一些含有苯环结构的芳香性碳氢化合物和少量的长烷烃化合物，由此推测煤基富勒烯的形成过程可能遵循着一条与以石墨为原料时的机制完全不同的途径。     

Gas dynamics in an arc discharge chamber as a factor governing the isolation of C60 and other “magic” fullerenes

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.     

C60大量、快速分离和电喷雾电离质谱检测

本文用配合沉淀和活性炭吸附相结合的方法，从高级富勒烯含量较高的混合物中，大量、快速分离Ｃ６０，并用电喷雾电离质谱对分离产物进行检测     

Direct computation of second-order SCF properties of large molecules on workstation computers with an application to large carbon clusters

Summary The ab initio SCF computation of second-order properties of large molecules (with 50 atoms or more) on workstation computers is demonstrated for static dipole polarizabilities and nuclear magneting shieldings. The magnetic shieldings are calculated on the basis of gauge including atomic orbitals (GIAO). Algorithmic advances (semi-direct algorithms with efficient integral pre-screening, and use of a quadratically convergent functional for the polarizabilities) are presented together with an illustrative application to the fullerenes C₆₀ and C₇₀.     

内嵌富勒烯的研究进展

内嵌富勒烯由于其结构新颖以及独特而优异的性质在国际上引起持续而广泛的关注,成为近年来的研究热点之一.目前已经研究发现的内嵌富勒烯多达近百种,从惰性气体到碱土金属再到稀土元素都已被成功地嵌入到不同尺寸的碳笼中.其中金属离子或含金属的离子簇内嵌入富勒烯碳笼形成的内嵌金属富勒烯,以其种类丰富、结构多样成为内嵌富勒烯的主要研究对象.本文就近年来研究报道的种类繁多的内嵌富勒烯按其内嵌物类型进行归纳阐述,为今后开发更多新型的内嵌富勒烯提供一定的参考.     

Numerical Kekulé structures of fullerenes and partitioning of pi-electrons to pentagonal and hexagonal rings

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.     

A molecular-dynamics simulation study of solvent-induced repulsion between C60 fullerenes in water

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.     

Fullerenes as a new type of ligands for transition metals

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.     

卤化富勒烯研究进展

自从C60被发现并能被大量制备以来,富勒烯化学已成为有机化学学科发展最快的领域之一。富勒烯通过多加成反应形成具有独特结构和性能的富勒烯卤化物和全氟烷基化物,为设计合成新型富勒烯基功能材料开辟了新方向。本文综述了近几年来在卤化富勒烯和全氟烷基化富勒烯的合成方法、结构及性能方面取得的最新进展,重点介绍了氟化富勒烯及其衍生化反应,并展望了该领域今后的发展趋势。     

Technology for manufacture of pure fullerenes C60, C70 and a concentrate of higher fullerenes

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.     

富勒烯合成化学研究进展

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。