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.     

Theoretical study of endohedral metallofullerenes: Sc3−nLanN@C80 (n=0–3)

To provide theoretical insight into the structures and properties of Sc₃N@C₈₀, which has been isolated in high yield and purity as a new stable endohedral metallofullerene, density functional calculations are carried out for the Sc_3?nLa_nN@C₈₀ (n=0–3) series. Because of electron transfer from Sc₃N to C₈₀, the electronic structure of Sc₃N@C₈₀ is formally described as (Sc₃N)⁶⁺C$_{80}^{6-}$. The encapsulated Sc₃N cluster takes a planar structure with long Sc–Sc distances and is highly stabilized inside the I_h cage of C₈₀, which rotates rapidly. As the number of La atoms increases, the Sc_3?nLa_nN cluster is forced to maintain a pyramidal structure in Sc_3?nLa_nN@C₈₀. In addition, the C₈₀ cage takes an open‐shell electronic structure due to an increase in the number of electrons transferring from Sc_3?nLa_nN. These make the endohedral structure less stable and more reactive. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1353–1358, 2001     

Electrochemistry of metallofullerene films: the major isomer of Dy@C82

Solution-cast films of the major isomer of Dy@C(82) (Dy@C(82)(I)) have been studied by cyclic voltammetry (CV) in acetonitrile. The films are found to display pronounced and stable redox responses in solution. The reduction/reoxidation processes exhibit large splittings between the first two reduction and reoxidation waves. However, a pair of reversible oxidation and rereduction waves is observed after the reoxidation of a reduced film. The characteristics and the inter-relationship of these waves are uncovered by the CV technique, scanning electron microscopy (SEM), and UV/Vis-NIR spectra. A possible mechanism is proposed for the film electrode processes, which emphasizes the redox-induced structural reorganization of the metallofullerene film by the incorporation and expulsion of electrolyte ions into and out of the film. The influence of the counter ion diffusivity and the ion-pair stability on the electrochemical activity of the metallofullerene film has also been indicated.     

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．     

内嵌金属富勒烯的笼外化学修饰

内嵌金属富勒烯以其独特的结构和新奇的性质吸引了众多科学家的目光,对它们进行笼外化学修饰是最近十年来新兴的研究热点,这对于考察内嵌金属富勒烯的结构及化学物理性质并拓宽其应用范围具有重要意义。本文将内嵌金属富勒烯与各种底物的不同作用分类,以反应类型为线索,详细概括了已发表的内嵌金属富勒烯的各种笼外化学反应,包括各种环化反应、内嵌金属富勒烯与杯芳烃及冠醚的自组装、单键相连的衍生物、水溶性衍生物以及用内嵌金属富勒烯填充碳纳米管等。在对各种化学反应阐述的同时,对内嵌金属富勒烯的可能应用也进行了总结,并提出了自己的看法。     

Theoretical Studies on Structures and Properties of Endohedral Fullerenes Complexes： XHn@C32（X=F,O, N,C; n=l-4）

Theoretical studies on structures and properties of endohedral fullerene complexes formed by encapsulating small molecules of HF, H20, NH3, and CH4 in a C32 fullerene cage, were carried out by ab initio method. Current calculations reveal that these processes to encase them in fullerene are energetically unfavorable because of the small cavity size of C32. The red shift in the F-H stretching frequency indicates the potential existence of hydrogen bonding between the HF molecule and the carbon cage.     

Controllable Growth of Fullerene Nanostructures

One‐dimensional fullerene nanostructures with well‐defined morphology have been prepared by a controllable method. Fullerene molecules, such as C₆₀ derivatives and endohedral metallofullerenes, are introduced into the pores of anodic aluminum oxide (AAO) templates under a direct current (DC) electric field. Then several nanostructures such as porous‐wall and solid‐wall fullerene nanowires and nanotubes were fabricated in the pores. The morphology of the fullerene nanostructures is well controllable, and the fullerene nanotubes can be further fabricated through filling nickel atoms inside to form fullerene‐metal composite structures. The results provide, in principle, a step toward broader applications of fullerene‐related materials in nanoscience and nanotechnology.     

Redox Modulation of the Reactivity and Regioselectivity in Diels–Alder Reaction of Metallofullerene La@C82 with Cyclopentadiene

Modulation of the reactivity of metallofullerenes is critical for production of metallofullerene derivatives with desired properties and functionalities. In this study, we investigate the effects of reduction and oxidation on the reactivity and regioselectivity in Diels–Alder reaction of metallofullerene La@C₈₂ by means of density functional theory calculations. Because of the enhanced electron-deficiency characteristic upon oxidation, the oxidized metallofullerene exhibits higher thermodynamic and kinetic reactivity as compared with neutral La@C₈₂. The regioselectivity in the reaction of La@C₈₂ with cylcopentadiene is remarkably changed after oxidation of the metallofullerene, which is explained in terms of the changes in the geometrical structure and the electronic structure of the metallofullerene. Quantitative analysis based on the activation-strain model demonstrates that the low activation energy barrier for the reaction of the cation La@C₈₂⁺ with cyclopentadiene originates from small strain energy and large interaction energy between the reactants. Energy decomposition analysis on the transition states of the reactions reveals that the exchange-repulsion interaction energy is one of the critical factors that determine the kinetic reactivity of the metallofullerene. This study not only provides new theoretical insights on how to modulate the reactivity of metallofullerenes, but also offers guideline for future experimental synthesis of new metallofullerene derivatives.