Voltammetric Behavior of Water‐Soluble Endohedral Metallofullerene Derivatives

Voltammetric behavior of water‐soluble endohedral metallofullerene derivatives Gd@C₈₂(OH)₅(NHCH₂COOH)₉ (GN) and Gd@C₈₂(OH)₆(NHCH₂CH₂SO₃H)₈ (GS) was characterized in 0.1 M KCl solution by CV and DPV. They showed similar redox behavior, that is, a reversible electroreduction process on HMDE was found; in the mean time, an irreversible oxidation process and an irreversible reduction process on GC electrodes were also observed. The results reveal that these two water‐soluble endohedral metallofullerene derivatives have good electron donating ability and poor electron accepting ability due to hydroxy groups, aminoacetic acid and aminoethyl sulfonic acid connected to the C₈₂ cage in comparison with Gd@C₈₂.     

内含式化合物X@B12P12的结构与稳定性研究

采用B3LYP/6-31G*方法，对内含式化合物X@B₁₂P₁₂(X=Li^0/+、Na^0/+、K^0/+、Be^0/2+、Mg^0/2+、Ca^0/2+、H和He)的不同对称性构型进行了计算，讨论其最稳定构型的几何参数、布居分析、偶极矩、电离势、包含能、振动频率、能隙和自旋密度． 发现在X@B₁₂P₁₂化合物中，客体X=Li、Na^0/+、K^0/+、Mg^0/2+、Ca^0/2+和He处在偏离笼的中心0.006 nm的半径内． Be²⁺沿着C₃轴偏离中心点0.279 nm． 在Be@B₁₂P₁₂和H@B₁₂P₁₂的基态结构中，Be和H与笼上的B原子成键． 除Li@B₁₂P₁₂、 Be²⁺@B₁₂P₁₂和He@ B₁₂P₁₂外， 其余结构为C_s对称稳定构型．     

The structure and electronic property of the smallest C20‐glycine and Gd‐encapsulated C20‐glycine derivatives with potentially biological activity

Theoretical calculations on interaction of the C₂₀ fullerene (consists solely by pentagons) with the smallest amino acid (glycine) were carried out using density‐functional theory method. The glycine molecule energetically prefers to interact with the Top‐site on the C₂₀ cage via its amino nitrogen (N) active site. The stable ordering of three active sites on glycine molecule is NH₂‐site > O‐site > OH‐site. Moreover, when the Gd atom is encapsulated to the center of C₂₀‐glycine, the cage volume obviously increase ～24.8%; and the endohedral atom induces the generation of two strong bands in the partial density of states spectra, which could cause the effect on optical properties. Additionally, it is also found that the modified C₂₀‐glycine derivative by Gd atom can reduce the thermodynamic and kinetic stabilities. It could be expected that the study may provide a theoretical reference in exploring their intrinsic feature structurally to antitumor activity. © 2012 Wiley Periodicals, Inc.     

内嵌镧金属富勒烯的高产率合成及异构体比例调控

采用电弧放电法制备内嵌镧金属富勒烯的原灰,通过改变氦气压力及电流强度来提高内嵌镧金属富勒烯产率。原灰由1,2,4-三氯苯提取并回溶入甲苯后,利用分析型高相液相色谱（HPLC）对提取液中各富勒烯组分进行分析。通过分别衡量3种常见含镧金属富勒烯La@C_2v-C₈₂、La@C_s-C₈₂和La₂@C₈₀与C₈₄的相对峰面积比,探讨了氦气压力和电流强度等对3种金属富勒烯产率的影响。实验结果表明,氦气压力与电流强度共同决定了金属富勒烯的产率,在（1）低电流高氦气压、（2）中等电流中等氦气压、（3）高电流低氦气压的条件下都可以高产率地获得含镧金属富勒烯。此外,调整电流强度和氦气压力可以改变La@C_2v-C₈₂和La@C_s-C₈₂的相对比例。例如,在电流为100、120 A或氦气压为20、35 kPa时,此前认为的"minor"异构体La@C_s-C₈₂的含量甚至高于"major"异构体La@C_2v-C₈₂。我们还发现,降低电流强度或减小氦气压力可促进La₂@C₈₀的生成,这表明La₂@C₈₀与La@C₈₂的形成过程可能是不同的。     

Synthesis and characterization of a biphenyl-linked hemicryptophane and an endohedral cobalt(II) complex

Hemicryptophanes are covalent molecular cages, constructed from a cyclotriveratrylene-based host unit and a functional unit linked by covalent spacers, which have been designed to accommodate endohedral functionalities in the cavity. In this study, the synthesis and characterization of the rigid, biphenyl-linked hemicryptophane 1 were investigated by NMR, ESI-MS, and X-ray crystallography. The structure of the inclusion complex, in which a dichloromethane molecule was constructed encapsulated within 1, was characterized by X-ray crystallography. An endohedral, cobalt(II) hemicryptophane complex 2 was also synthesized and characterized ESI-MS and X-ray crystallography. The X-ray crystal structure of 2 showed that the biphenyl-linked hemicryptophane had three components—a molecule each of chloroform and acetonitrile, and a cobalt(II) ion—within its cavity.     

Theoretical study on the smallest endohedral metallofullerenes: TM@C20 (TM = Ce and Gd)

The structure, electronic property, and infrared spectroscopy of endohedral metallofullerenes TM@C₂₀ (TM = Ce and Gd) have been systematically investigated with the aid of the hybrid DFT‐B3LYP functional. It is found that in the endohedral metallofullerenes the average C? C bond lengths are obvious longer than those of empty cage. The frontier orbital analyses show that the endohedral metallofullerene Gd@C₂₀ has the high‐thermodynamic stability. Natural population analysis also tells us that only in the Ce@C₂₀, the Ce atom acts as an electron acceptor with the negative charges, and the 4f orbitals of Ce and Gd atoms have a significant contribution in the formation of chemical bonding. Additionally, the analyses of harmonic vibrational frequencies reveal that when the TM atoms are encapsulated into the C₂₀ cage, the strongest absorption peaks are characterized by a mixture of TM?C bending and C? C stretching vibrations. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Dearomative Ring-Fused Azafulleroids and Carbazole-Derived Metallofullerenes: Reactivity Dictated by Encapsulation in a Fullerene Cage

Herein, we report divergent additions of 2,2′-diazidobiphenyls to C₆₀ and Sc₃N@I_h-C₈₀. In stark contrast to that of the previously reported bis-azide additions, the unexpected cascade reaction leads to the dearomative formation of azafulleroids 2 fused with a 7-6-5-membered ring system in the case of C₆₀. In contrast, the corresponding reaction with Sc₃N@I_h-C₈₀ switches to the C−H insertion pathway, thereby resulting in multiple isomers, including a carbazole-derived [6,6]-azametallofulleroid 3 and a [5,6]-azametallofulleroid 4 and an unusual 1,2,3,6-tetrahydropyrrolo[3,2-c]carbazole-derived metallofullerene 5 , whose molecular structures have been unambiguously determined by single-crystal X-ray diffraction analyses. Among them, the addition type of 5 is observed for the first time in all reported additions of azides to fullerenes. Furthermore, unexpected isomerizations from 3 to 5 and from 4 to 5 have been discovered, providing the first examples of the isomerization of an azafulleroid to a carbazole-derived fullerene rather than an aziridinofullerene. In particular, the isomerism of the [5,6]-isomer 4 to the [5,6]-isomer 5 is unprecedented in fullerene chemistry, contradicting the present understanding that isomerization generally occurs between [5,6]- and [6,6]-isomers. Control experiments have been carried out to rationalize the reaction mechanism. Furthermore, representative azafulleroids have been applied in organic solar cells, thereby resulting in improved power conversion efficiencies.     

Cyclic voltammetry modeling, geometries, and electronic properties for metallofullerene complexes with mu3-eta2:eta2:eta2-C60 bonding mode

Reduction potential (E(red)) values have been calculated and compared with available cyclic voltammetry (CV) data for 10 metallofullerene complexes with the mu(3)-eta(2):eta(2):eta(2)-C(60) (M(3)-C(6)[C(60)]) bonding mode. Consideration of bulk solvent effects is essential for the calculation of the E(red) values. Scaling factors for the electrostatic terms of the solvation energies have been introduced to fully describe the experimental cyclic voltammograms with a small mean deviation of 0.07 V. Multiple electron reductions induce movement of the metal cluster moieties on the C(60) surface, which is accompanied with the changes in some M-C[C(60)] bonds from pi-type to sigma-type mode. However, the changes in M(3)-C(60) distances, as well as the geometric changes of M(3) and C(60), are small for the reductions, which is in harmony with the high chemical and electrochemical stability of the metallofullerenes. Our population analyses reveal that the added electrons are not localized at the C(60) moieties, and electron population in the metal clusters is significant, more than 20% (av. 37%), for all the reductions. Furthermore, we demonstrated that the two close one-electron redox waves in CV diagrams are strongly correlated with significant electron delocalization, about 40-80%, to the metal-cluster moieties in these metallofullerene complexes.     

Darstellung,Isolierung und Charakterisierung von Ba@C74

Preparation, Isolation, and Characterization of Ba@C₇₄ For the first time Ba@C₇₄ has been isolated in pure form. The title compound has been isolated from a raw material, produced in a radio‐frequency‐furnace, consisting of a mixture of fullerenes and endohedral Bariumfullerenes. Ba@C₇₄ was separated by two stage sublimation and subsequent high‐performance liquid chromatography (HPLC) using a Buckyprep column. The capacity factor for Ba@C₇₄ is 6.0. Its endohedral character has been deduced from the fragmentation pattern obtained by time‐of‐flight mass spectroscopy while the composition has been confirmed by comparison of calculated and measured isotopic pattern of the parent peak. Further characterization was performed by VIS/NIR‐spectroscopy and electron‐paramagnetic‐resonance spectroscopy (EPR).     

Encapsulation of glycine inside C60 fullerene: Impact of confinement

Confinement of glycine inside C₆₀ fullerene (gly@C₆₀) is analyzed via geometrical, energetic and deformation density of intermolecular interaction. Results show that both fragments are significantly deformed due to the compression imposed by the confinement. Also kinetic energy pressure and relaxation deformation density analyses are used to describe the nature of interaction between components, and topological analysis of the steric deformation density in gly@C₆₀ was carried out to find the critical points of the charge deformation due to steric effects. The relevance between different types of energies and charge displacement show almost identical sensitivity of energies to the repulsive interaction.