金属富勒烯[Dy@C_(82)(I)]膜的电化学研究

研究并对比了金属富勒烯Dy @C82 的主要异构体Dy @C82 (I)固体膜在有机溶剂乙腈及水溶液中的电化学性质 .在乙腈溶液中 ,Dy @C82 (I)膜的电化学行为不同于其溶于有机溶剂中的电化学行为 ,前两个还原峰与其对应的再氧化峰之间存在大的分裂 .但是 ,经过还原及再氧化后的Dy @C82 (I)膜却存在一对对称性很好的氧化及再还原峰 .解释为经过还原后的Dy @C82 (I)膜的结构有利于进一步氧化 ,而不需要结构重排 ;在水溶液中 ,Dy @C82 (I)膜的电化学行为不同于其在乙腈溶液中 ,却类似于其有机溶液在Pt电极上的电化学行为 ,出现了对称性很好的三对还原峰及一对氧化峰 .在水溶液中 ,Dy @ C82 (I)的前三价负离子及一价正离子是稳定的 .利用紫外 -可见 -近红外 (UV Vis NIR)光谱及扫描电镜 (SEM)等技术对膜的性质及表面形貌等进行了表征     

Studies on metallofullerene (Dy@C82) embedded in a DDAB film in aqueous solution

The electrochemical behavior of metallofullerene (Dy@C82) in didodecyldimethylammonium bromide (DDAB) films deposited on glassy carbon, quartz crystal microbalance (QCM) gold crystals, and indium tin oxide (ITO) electrodes in aqueous solution was investigated in detail. Four pairs of reversible redox peaks were observed, and for the first time, these peaks were characterized by vis/NIR spectroscopy. Different from previous fullerene/cationic lipid modified electrodes, one oxidation and three reduction processes were observed. The stability of Dy@C82 and its ions in the film toward air was detected by measuring its cyclic voltammogram after holding the potentials for 10 s, followed by introducing 10 microL of air to the solution. Dy@C82 and its first three anions are stable toward air and water, while some chemical reactions take place when the third anion is further reduced in the film. Dy@C82+ is less stable than Dy@C82- toward water and air. The electrochemical processes were measured in different electrolytes, which showed pronounced anionic dependence on either its cation or anions. The electrochemical processes were also monitored using electrochemical quartz crystal microbalance (EQCM), and from the result a possible electron-transfer mechanism of a Dy@C82/DDAB electrode in aqueous solution was presented. It showed that the anions of Dy@C82 were bound to the DDA+ cation in the film, while the anions of electrolyte diffused into the film to compensate the positive charges when a cation of Dy@C82 was generated.     

Coverage-dependent Orientations of Dy@C82 Molecules on Au(111) Surface

The adsorption and molecular orientation of Dy@C82 isomer I on Au(111) has been investi-gated using ultrahigh-vacuum scanning tunneling microscopy at 80 K. At low coverages, the Dy@C82 molecules tend to grow along the step edges of Au(111), forming small clusters and molecular chains. Adsorption of Dy@C82 on the edges is dominated by the fullerene-substrate interaction and presents various molecular orientations. At higher coverages, the Dy@C82 is found to form ordered islands consisting of small domains of equally oriented molecules. The Dy@C82 molecules in the islands prefer the adsorption configurations with the major C2 axis being approximately parallel to the surface of the substrate. Three preferable orientations of the Dy@C82 molecules are found in a two-dimensional hexagonal close packed overlayer. These observations are attributed to the interplay of the fullerene-substrate interaction and dipole-dipole interaction between the metallofullerenes.     

Electrochemistry of surface-grafted stimulus-responsive monolayers of poly(ferrocenyldimethylsilane) on gold

Poly(ferrocenyldimethylsilane)s with various degrees of polymerization and featuring a thiol end group were chemically end-grafted onto gold substrates by self-assembly, forming redox-active monolayers. The monolayers were characterized by contact angle measurements, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Layer thickness values were determined by surface plasmon resonance spectroscopy and ellipsometry. The electrochemical properties of these films in aqueous NaClO(4) were studied using cyclic voltammetry (CV), differential pulse voltammetry, chronoamperometry, and chronocoulometry. Cyclic voltammograms showed two reversible redox peaks, indicating a stepwise oxidation of the electroactive sites. The first oxidation step showed reversible behavior at low scan rates and quasi-reversible behavior at higher scan rates. Peak currents (i(p)) plotted against the square root of scan rates (v(1/2)) for the first oxidation peak and for the corresponding reduction peak exhibited a linear dependence, indicating that the oxidation process in the first step is controlled by the diffusion of counterions into the polymer film. For the second oxidation peak and the corresponding reduction peak, i(p) varied linearly with v. This redox behavior is characteristic of surface-immobilized electroactive layers. The higher reversibility of the second oxidation and reduction waves in the CV experiments was explained from the solvation of the surface-grafted poly(ferrocenylsilane) (PFS) chains, which depends on the degree of oxidation. Oxidized PFS films are swollen in the aqueous electrolyte solutions, leading to a higher segmental mobility of the polymer chains and a much increased counterion mobility within the film. Kinetic parameters for the redox processes were obtained from chronocoulometry experiments.     

Determination of molar extinction coefficients for endohedral metallofullerene Dy@C<Subscript>82</Subscript>(C<Subscript>2v</Subscript>)

Isomerically pure endohedral metallofullerene Dy@C₈₂(C _2v) was synthesized by the electric arc method, extracted from the soot with o-dichlorobenzene, isolated from the extract by HPLC, and characterized by mass spectrometry and spectrophotometry. The spectrophotometric titration of a solution of endohedral metallofullerene Dy@C₈₂(C _2v) was conducted with potassium perchlorotriphenylmethide. The concentration of Dy@C82(C _2v) in o-dichlorobenzene was determined, and the molar absorption coefficients for its neutral and anionic forms were calculated (3.0?10³ (at 927 nm) and 4.0?10³ mol^–1 L cm^–1 (at 884 nm), respectively.     

金属富勒烯的质谱研究

利用电弧放电法合成笼内金属富勒烯Gd@C₈₂,Gd₂@C₈₀,Gd@C₈₀实验结果表明,两步高温高压法(1,2,4-三甲基苯,吡啶)可有效地提取金属富勒烯Gd@C₈₂.本文分别利用ESI-MS,REC-MS,MALDI-TOF-MS质谱技术研究了Gd@C₈₂,Gd₂@C₈₀,Gd@C₈₀和富勒烯Cn(n=60,70,82,84…)的气相负离子特性.结果表明,包入Gd³⁺后非极性的C₈₂转变为极性的Gd@C₈₂分子;金属离子Gd³⁺处于C₈₂^3-笼中非中心的位置.     

The Combination of Phthalocyanines and Polymers for Electrochemically or Photoelectrochemically Induced Processes

Phthalocyanines 1-3 were used in combinations with polymers in order to investigate reduction/reoxidation of thin film electrodes, photoinduced reduction of dioxygen at the junction of thin film electrodes to an electrolyte, and dioxygen reduction in the dark (fuel cell reaction) at dispersions of phthalocyanines on carbon supports. Electrochromic reduction/reoxidation of phthalocyanines also occurs readily inside a polymer matrix if intermolecular particle contact exists. A significant photoreduction of dioxygen is observed if O₂ can form trapped states inside of the bulk of the film, with the result of enhanced photoconductivity. The kind of polymer is of striking influence. Phthalocyanines with central metals forming localized ionized states with dioxygen are active electrocatalysts for dioxygen reduction in the dark if they are finely dispersed on a carrier. The influence of both phthalocyanine and polymer component in each of the three-mentioned processes is discussed.     

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.     

一氯乙酸和三氯乙酸在富勒烯/DDAB膜修饰电极上的电催化

研究了由阳离子表面活性剂双十二烷基二甲基溴化铵分别和C60或C70在玻碳电极表面形成的膜在0．5mol／L KCl溶液中的电化学,发现在0～-1．0V范围内,有两对峰形较好的还原再氧化峰。实验结果表明,该修饰电极有较好的稳定性和重现性,对三氯乙酸和一氯乙酸的还原,表现出良好的电催化去卤化作用,说明修饰电极上的富勒烯是良好的电子传递媒介体。     

Spectroelectrochemical characterization of thin fullerene films in room temperature ionic liquids

Room-temperature ionic liquids were used as electrolytes for in situ studies of the transitions of solution cast fullerene films. 1-Butyl-3-methyl-imidazolium tetrafluoroborate (BMIMBF₄), 1-butyl-3-methyl-imidazolium hexafluorophosphate (BMIMPF₆) and 1-butyl-2,3-dimethylimidazolium tetrafluoroborate (BDiMIMBF₄) were used in this study and the techniques used are cyclic voltammetry and in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Infrared spectra were recorded during the reversible redox processes of the C₆₀ films showing a three-step one electron reduction and reoxidation reaction. After reoxidation some part of the C₆₀ film remained in its form. The IR bands obtained during electrochemical reduction of C₆₀ in ionic liquids were compared with the spectra reported for C₆₀ films upon reduction in the presence of different cations in organic solutions.     

Effect of the counterion on the rate of electron transfer in dendrimer films

The electrochemical behavior of a film composed of a redox-active dendrimer was studied as a function of the type of counterion available during its reduction and reoxidation. The rate of permeation/migration of counterions into the film appeared to be the bottleneck to electron transfer through the film. Because the dendrimer is rather hydrophobic, increasing the hydrophobicity of the counterion increased the rate and extent of electron hopping within the films.     

The electrochemical behavior of (C70)2-p-tert-butylcalix[8]arene complex film

Electrochemical behavior of (C₇₀)₂-p-tert-butylcalix [8] arene film on a glassy carbon electrode has been studied by cyclic voltammetry. Two pairs of reduction/reoxidation waves were detected in a mixed solvent of acetonitrile and water containing tetra-n-butylammonium perchlorate as the supporting electrolyte. Received: 12 January 1998 / Accepted: 22 February 1998     

PANI-SnP复合膜电极在镍镉废水中电控离子交换性能

采用滴涂法在铂基底制备了电活性聚苯胺-磷酸锡(PANI-SnP)复合膜电极,考察了该电极在Ni²⁺、Cd²⁺溶液的电控离子交换性能. 用傅立叶变换红外光谱和扫描电镜分析观察复合膜的组成及表面形貌;在0.1 mol·L^-1 Ni(NO₃)₂、Cd(NO₃)₂溶液,通过循环伏安法比较了PANI膜、SnP膜及PANI-SnP复合膜电极的电化学性能,并结合电化学石英晶体微天平技术重点考察了PANI-SnP复合膜的离子交换机制;同时,通过循环伏安法调控复合膜电极的氧化还原电位,结合X射线能谱和X射线光电子能谱分别测定了其氧化和还原状态的元素组成. 结果表明,PANI-SnP复合膜电极在Ni²⁺、Cd²⁺溶液均有良好的氧化还原电活性和可逆离子交换性能,其Cd²⁺离子选择性优于Ni²⁺离子,通过电控离子交换可使Cd²⁺离子从镍镉废水高效分离.     

血红素修饰电极及其催化氧还原性质

金属大环络合物（卟啉、酞箐、维生素Ｂ_(１２)等）修饰电极对氧、一氧化氮和其它生物物质的催化作用［１－３］引起了化学工作者的极大兴趣,血红素是一种重要的铁卟啉化合物,是血液中血红蛋白的重要组成部分,承担携氧的任务,由于其特殊的生理功能,研究血红素修饰电极的性质和作用对进一步研究开发燃料电池具有很重大的意义．卟啉在电极上的修饰有多种方法,当卟啉或金属卟啉环侧链上具有苯氨基、苯酚基、乙烯基或吡咯等取代基时［３］,可采用电氧化聚合法制备聚卟啉膜．本文采用循环伏安法在水溶液中制备了聚血红素膜电极,研究了聚…     

Electrochemical survey: the effect of the cage size and structure on the electronic structures of a series of ytterbium metallofullerenes

The electrochemical properties of a series of metallofullerenes with different cages, namely, Yb@C74(II), Yb@C76(I, II), Yb@C78, Yb@C80, Yb@C82(I, II, III), and Yb@C84(II, III, IV), have been systematically investigated by cyclic and differential pulse voltammetry experiments for the first time. This article discusses the electronic structures of these metallofullerenes based on the results from these experiments. From previous electrochemical work and the above discussion, it is concluded that the nondegenerate LUMO is a common characteristic of the electronic structures of the higher fullerenes and monometallofullerenes. In addition, the effect of the cage on the electronic structure and properties of the metallofullerene is estimated from the plot of the reduction potential versus the carbon number of the metallofullerene. This estimation shows that usually the electronic structure and properties of the metallofullerene vary with cage size and structure. The cage structure is of particular importance for determining the electronic structure and properties. Moreover, an explanation concerning the abundance and stability of C82-based trivalent monometallofullerenes is given from an electronic structural standpoint.     

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.     

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.     

Electrochemically deposited organic luminescent films: the effects of deposition parameters on morphologies and luminescent efficiency of films

The electropolymerization behaviors of an electroactive and luminescent compound TCPC as precursor are studied. The resultant electrochemical deposition (ED) films are characterized by cyclic voltammetry (CV), UV-vis, fluorescence spectra, scanning electron microscopy (SEM), and atomic force microscopy (AFM). Under the CV mode with potential range of -0.5 to 0.85 V vs Ag/Ag(+), the coupling reactions between the carbazole units of TCPC are very efficient, while the fluorescent trifluorene segment in TCPC is chemically inert in this potential range, which results in a highly fluorescent film formation on indium tin oxide (ITO) electrode. The deposition parameters for preparing the TCPC-based ED films are optimized, and the best ED film gives the fluorescence efficiency of 45.5% with surface roughness of 2.8 nm and morphologic stability as heating to 180 degrees C. The light-emitting devices (LEDs) using this ED film as light emitting layer with structure ITO/ED film (approximately 100 nm)/Ba/Al achieve maximum luminescence and external quantum efficiency of 4224 cd/m(2) at 17 V and 0.72% at 11.5 V, respectively, which are better than the device using TCPC spin-coating films as emitting layer. The technique provides a facile route toward a patternable luminescent film and device because such luminescent ED films can be manipulatively deposited on the electrified electrode.     

A density functional theory study of shake-up satellites in photoemission of carbon fullerenes and nanotubes

Carbon 1s shake-up spectra of fullerenes C(60), C(70), and C(82) and single-walled carbon nanotubes (SWCNTs) of (5,5), (6,5), and (7,6) have been investigated by using equivalent core hole Kohn-Sham density functional theory approach, in which only one-electron transition between molecular orbitals within core-hole potential is considered. The calculated spectra are generally in good agreement with results of equivalent core-hole time-dependent density functional theory calculations and available experiments, and reliable assignments for the complicated shake-up spectra of such large systems are provided. Calculations have also been performed for endohedral metallofullerene Gd@C(82) to demonstrate the possible use of shake-up processes to identify the charge transfer between the metal ion and the carbon cage. It is found that the exciton binding energy of all systems under investigation is around 0.5 eV.     

水溶性金属富勒烯衍生物的合成和表征

Three water-soluble metallofullerene derivatives have been synthesized.IRand XPSanalysis indicate that they have average compositions of Gd@C₈₂(OH)₂₂, Gd@C₈₂(OH)₆(NHCH₂CH₂SO₃H)₈and Gd@C₈₂(OH)₅(NHCH₂COOH)₉, respectively.They are particularly interesting in medical application.