Cyclic 7-edge-cuts in fullerene graphs

A fullerene graph is a planar cubic graph whose all faces are pentagonal and hexagonal. The structure of cyclic edge-cuts of fullerene graphs of sizes at most 6 is known. In the paper we study cyclic 7-edge connectivity of fullerene graphs, distinguishing between degenerate and non-degenerate cyclic edge-cuts, regarding the arrangement of the 12 pentagons. We prove that if there exists a non-degenerate cyclic 7-edge-cut in a fullerene graph, then the graph is a nanotube unless it is one of the two exceptions presented. We determined that there are 57 configurations of degenerate cyclic 7-edge-cuts, and we listed all of them.     

Fullerene graphs have exponentially many perfect matchings

A fullerene graph is a planar cubic 3-connected graph with only pentagonal and hexagonal faces. We show that fullerene graphs have exponentially many perfect matchings.     

New isomerization operations for fullerene graphs

The problem of topological isomerization operations for fullerenes is considered. Two basic classes of isomerization transformations admissible for fullerene graphs are proposed: rotation and mirror reflection of a chosen part of fullerene graph. Pyracylene and generalized Stone-Wales rearrangements are only the specific cases of extended isomerization operations for the fullerene graphs.     

Long cycles in fullerene graphs

It is conjectured that every fullerene graph is hamiltonian. Jendrol’ and Owens proved [J. Math. Chem. 18 (1995), pp. 83–90] that every fullerene graph on n vertices has a cycle of length at least 4n/5. In this paper we, improve this bound to 5n/6 − 2/3.     

富勒烯/环糊精复合物及其在生物医药领域的应用

富勒烯有着独特的球形结构,这一结构赋予了其优异的光电及生物性能,在生物医药领域备受关注。环糊精具有良好的水溶性和生物相容性,锥筒状结构赋予了其特异性包合作用,在主客体化学中有着非常重要的地位。富勒烯/环糊精的复合物,结合了富勒烯和环糊精的优势,在DNA切割,光动力学疗法,药物载体等领域发挥了重要作用。本文从富勒烯与环糊精体系的构筑出发,综述了富勒烯/环糊精非共价包合物及共价偶联物在生物医药领域应用的研究进展,且对富勒烯/环糊精复合物的应用进行了展望,为构建新型富勒烯/环糊精复合物提供参考。     

Synthesis of two pentaarylated [60]fullerene derivatives Ar_5C_(60)-H (Ar = p-MeC_6H_4, m-MeC_6H_4) and their novel electrochemical properties

Through one pot reaction of C60 with organocopper/magne-sium reagent ( p - MeQ H4 )2 CuMgBr or ( m - MeC6 H )2 -CuMgBr prepared from CuBr-Me2S and p-MeC6H4MgBr or m-MeC6H4MgBr and subsequent quenching with aqueous NH4Cl, two pentaarylated [60] fullerene derivatives (p-MeC6H4)5C60H (1) and (m-MeC6H4)5C60H (2) have been synthesized in 94% and 96% yields, respectively. While known compound 1 prepared via this improved method is unambiguously identified, new compound 2 is fully characterized by elemental analysis, IR, UV-vis, 1H NMR and 13C NMR spectroscopies. Additionally, electrochemical study shows that the two [60] fullerene derivatives 1 and 2 in dichloromethane solution display two sequential one-electron reductions which are shifted by about 0.4V towards more negative potential values with respect to free C60. Such remarkable cathodic shift is attributed to the multiple breakage of the double-bond conjugation within the fullerene core.     

Cyclical Edge-Connectivity of Fullerene Graphs and (k, 6)-Cages

It is shown that every fullerene graph G is cyclically 5-edge-connected, i.e., that G cannot be separated into two components, each containing a cycle, by deletion of fewer than five edges. The result is then generalized to the case of (k,6)-cages, i.e., polyhedral cubic graphs whose faces are only k-gons and hexagons. Certain linear and exponential lower bounds on the number of perfect matchings in such graphs are also established.     

On Some Structural Properties of Fullerene Graphs

We show how some important structural properties of general fullerene graphs follow from the recently proved fact that all fullerene graphs are cyclically 4-edge connected. These properties, in turn, give us upper and lower bounds for various graph invariants. In particular, we establish the best currently known lower bound for the number of perfect matchings in fullerene graphs.     

Synthesis of fullerene building blocks bearing alkyne or azide groups and their subsequent functionalization by the copper mediated Huisgen 1,3-dipolar cycloaddition

C₆₀ derivatives bearing either terminal alkyne or azide functional groups have been prepared and used as building blocks under the copper mediated Huisgen 1,3-dipolar cycloaddition conditions. In general, the reactivity of C₆₀ toward azides does not significantly compete with the cycloaddition leading to the desired 1,2,3-triazole derivatives and good yields can be obtained when fullerene derivatives with reasonable solubility are used as starting materials. The electrochemical properties of the new fullerene derivatives have also been investigated by cyclic voltammetry (CV) and Osteryoung Square Wave Voltammetry (OSWV).     

Synthesis and characterization of ferrocene-perylenetetracarboxylic diimide-fullerene triad

Novel ferrocene-perylenetetracarboxylic diimide-fullerene hybrid has been synthesized and characterized. UV/vis spectroscopic and cyclic voltammetric results indicate that ferrocene-contained hybrid show weak intramolecular charge transfer interaction in their ground states. The preliminary studies have shown that electron transfer from the ferrocene unit to the perylenetetracarboxylic diimide in dyad FcP takes place, while electron transfer from the ferrocene to the perylenetetracarboxylic diimide and electron transfer from the perylenetetracarboxylic diimide unit to the fullerene are proposal process in the case of FcPF.     

Synthesis and characterization of a new ethynyl-bridged C60 derivative bearing a diketopyrrolopyrrole moiety

A new soluble C₆₀ derivative bearing a diketopyrrolopyrrole (DPP) moiety has been synthesized by ethynylation reaction. Characterization by UV-visible spectrophotometry and cyclic voltammetry has been performed in order to study the influence of the DPP moiety on electronic and optical properties of the fullerene. Moreover, DFT calculations have been conducted on the derivative and its precursor in order to correlate the orbital geometry with experimental data.     

Semiempirical molecular dynamics studies of C60/C70 fullerene oxides: C60O, C60O2 and C70O

The spectral analysis indicates that all isomers of C₆₀O, C₇₀O and C₆₀O₂ have an epoxide-like structure (an oxygen atom bridging across a C–C bond). According to the geometrical structure analysis, there are two isomers of fullerene monoxide C₆₀O (the 5,6 bond and the 6,6 bond), eight isomers of fullerene monoxide C₇₀O and eight isomers of fullerene dioxide C₆₀O₂. In order to simulate the real reaction conditions at 300 K, the calculation of the different isomers of C₆₀O, C₆₀O₂ and C₇₀O fullerene oxides was carried out using the semiempirical molecular dynamics method with two different approaches: (a) consideration of the geometries and thermodynamic stabilities, and (b) consideration of the ozonolysis mechanism. According to the semiempirical molecular dynamic calculation analysis, the probable product of this ozonolysis reaction is C₆₀O with oxygen bridging over the 6–6 bond (C_2v). The most probable product in this reaction contains oxygen bridging across in the upper part of C₇₀ (6–6 bond in C₇₀O-2 or C₇₀O-4) an epoxide-like structure. C₆₀O₂-1, C₆₀O₂-3 and C₆₀O₂-5 are the most probable products for the fullerene dioxides. All of these reaction products are consistent with the experimental results. It is confirmed that the calculation results with the semiempirical molecular dynamics method are close to the experimental work. The semiempirical molecular dynamics method can offer both the reaction temperature effect by molecular dynamics and electronic structure, dipole moment by quantum chemistry calculation.     

新奇二茂铁甲基氮C60衍生物的合成、结构

尽管目前人们对富勒烯[C₆₀]的过渡金属有机物研究较多^[1],但通过氮卡宾方式连接的C₆₀二茂铁衍生物尚未见报道。鉴于对C₆₀反应的浓厚兴趣及二茂铁的广泛应用价值^[2]我们 利用C₆₀的缺电子性^[3]将其与二茂铁甲基氮卡宾进行[1+2]环加成反应,分离并表征了一种具有齿轮式结构的新奇C₆₀二茂铁衍生物(CpFeC₅H₄CH₂N)5C₆₀(l)。     

Self-assembly of C(60) pi-extended tetrathiafulvalene (exTTF) dyads on gold surfaces

The first self-assembly of a C60 pi-extended tetrathiafulvalene (exTTF) dyad on a gold surface is reported. Four fullerene derivatives, two of them containing p-quinonoid pi-extended tetrathiafulvalenes (exTTFs), have been synthesized, and their solution electrochemistry has been investigated by means of cyclic voltammetry. Fullerene-containing SAMs of thioctic acid derivatives 3 and 6 have also been investigated by cyclic voltammetry. The cyclic voltammograms of both compounds exhibit three reversible reduction waves, and for compound 6, one irreversible oxidation process corresponding to the oxidation of the exTTF subunit is observed. Stable self-assembled monolayers (SAMs) of fullerene derivative 3 were formed on gold surfaces, whereas dyad 6 does not present a very clear electrochemical response, most probably as a result of structural rearrangements on the monolayer or charge transfer between the C60 and exTTF moieties.     

Steric conditions for donor–acceptor interactions in C60 complexes with planar organic donors

Charge transfer complexes of fullerene C₆₀ with planar donors of tetrathiafulvalene, dithiadiazafulvalene and pyranylidene family were investigated by IR- and UV-VIS-NIR spectroscopy. The analysis of IR and X-ray data shows that the charge transfer complexes of fullerene with the planar donors are involved in polarization interactions of van der Waals type. Charge transfer is very weak in these compounds and is hindered by unfavourable steric factors. As a result, the CT rate does not correlate with the ionization potential of the donor; the charge transfer absorption bands are very weak too.     

Novel addition in trifluoromethylation of [70]fullerene

Pyrolytic trifluoromethylation of [70]fullerene with CF₃CO₂Ag at 300 °C results in the addition of up to 12 CF₃ groups to the fullerene cage. Forty-six C₇₀(CF₃)_n derivatives (numbers in parentheses) were separated by two-stage high pressure liquid chromatography (HPLC) as follows: n = 2(2), 4(16), 6(9), 8(14) 10(5), some being characterised by NMR. The range of derivatives is much greater than for other [70]fullerene reactions, and as with [60]fullerene trifluoromethylation, no single derivative is dominant, indicating that kinetic stability mainly controls product formation. NMR spectra show most derivatives to be unsymmetrical, with combinations of quartets and septets (overlapping quartets) due to contiguous (‘linear’) addend arrays, having significantly different coupling constants of the ‘terminal’ quartets of between 9.1 and 17.7 Hz. These differences, together with those observed previously in trifluoromethylation of [60]fullerene are consistent with addition across both 6:6- and 5:6-ring junctions. Of the two C₇₀(CF₃)₂ isomers, one has either C_s or C₂ symmetry, the other has C₁ symmetry, whilst the C₇₀(CF₃)₄ derivatives fall into four categories: (i) symmetrical compounds (one gives only two singlets in the NMR); (ii) unsymmetrical compounds that show a ‘linear’ coupling sequence; (iii) unsymmetrical compounds having a remote pairs of adjacent groups; (iv) compounds having a coupled array of three CF₃ groups, together with a remote group suggesting sterically-driven migration. The first evaluation of differential NMR couplings across 6:6- and 5:6-bonds in a fullerene has been made using C₆₀F₆ as a model.     

Complex formation between water-soluble sulfonated calixarenes and C60 fullerene

The inclusion complexes of sulfonated thiacalix[4]arene 1 and calix[6]arene 2 sodium salts with C₆₀ fullerene were investigated by photoluminescence (PL) and quantum-chemical methods. The stoichiometries of calixarene/C₆₀ complexes were found to be 2:1 for 1 and 1:1 for 2. Related quantum-chemical investigations show that C₆₀ fullerene is included in a cavity composed of two half-bowl molecules of 1. The C₆₀ fullerene ball is located deep within the cavity of 2 and the negatively charged sulfonate arms probably inhibit the formation of the bowl-shaped capsule that was observed in the case of 1.     

On decompositions of leapfrog fullerenes

It is shown that given a fullerene F with the number of vertices n divisible by 4, and such that no two pentagons in F share an edge, the corresponding leapfrog fullerene Le(F) contains a long cycle of length 3n − 6 missing out only one hexagon.     

Stereodivergent‐at‐Metal Synthesis of [60]Fullerene Hybrids

Chiral fullerene–metal hybrids with complete control over the four stereogenic centers, including the absolute configuration of the metal atom, have been synthesized for the first time. The stereochemistry of the four chiral centers formed during [60]fullerene functionalization is the result of both the chiral catalysts employed and the diastereoselective addition of the metal complexes used (iridium, rhodium, or ruthenium). DFT calculations underpin the observed configurational stability at the metal center, which does not undergo an epimerization process.     

Design,Synthesis, and Optical/Electronic Properties of a Series of Sphere-Rod Shape Amphiphiles Based on the C60-oligofluorene Conjugates

A series of sphere-rod shape amphiphiles were designed and synthesized by connecting the rod-like oligofluorenes with different lengths(OF_n) to the different positions of the spherical [60]fullerene(C_(60)) through a rigid linkage. The conjugates were characterized by ~1H-NMR, ~(13)C-NMR, FTIR, EA and MALDI-TOF mass spectrometry. The optical and electronic properties of the conjugates were studied by UV-Vis absorption spectroscopy, fluorescence spectrometry, and cyclic voltammetry. The results from UV-Vis absorption spectroscopy and cyclic voltammetry indicated that the energy profiles of C_(60) and OF_n remained unchanged when different lengths of OF_n were attached to C_(60). The electron affinities of the OF_n-C_(60) conjugates were close to that of C_(60), while slight electronic interaction was found between the two individual chromophores(C_(60) and OF_n) in their ground states. The fluorescence spectra exhibited a complete fluorescence quenching in the toluene solution, suggesting an effective energy transfer from OF_n to C_(60). It presents a systematic study on the selfassembly, structure-property relationship, and potential technical applications of the conjugates.