Synthesis, characterization and crystal structure of a charge transfer salt based on 1.3-cyclopentadiene tetrabutylammoniumdodecamolybdosilicoate

A charge transfer salt, (Bu4N)(4) (C5H6)[(HSiMo11MoO40)-Mo-VI-O-V] has been photochemically synthesized from (Bu4N)(4)SiMo12O40 and 1.3-cyclopentadiene and Characterized, by elemental analysis, IR spectra, solid diffusion reflectance electronic spectra, CV and ESR. The X-ray crystal structure revealed that the title complex crystal data are as follows: triclinic, space group P (1) over bar, a = 14.347(3), b = 14.423(3), c = 27.158(5) Angstrom, alpha = 96.90(3), beta = 104.18(3), gamma = 98.20(3)degrees, V = 5322(2) Angstrom (3), Z = 2, M-r = 2855. 30, D-c = 1.782g.cm(-3), F(000) = 2860, R = 0.0719, wR = 0.198. The title compound is composed of 1.3-cyclopentadiene, four tetrabutylammonium and [(SiMo11MoO40)-Mo-VI-O-V](4-) anion.

Oriented polyoxometalate-polycation multilayers on a carbon substrate

In this paper, a new method of fabricating multilayers on a carbon substrate is presented. First, a uniformly charged carbon surface was prepared through molecular design. Then an ultrathin film consisting of layer-pairs of oppositely charged polymeric cationic poly(diallyldimethylammonium chloride) (PDDA) and silicotungstate, SiW12O404- (SiW12), was grown layer-by-layer onto the grafted carbon substrate using a molecular self-assembly technique and an electrochemical method. The technique allows one to prepare highly adherent, dense and smooth films of polyoxometalates with special properties. By combining cyclic voltammetry (CV) and X-ray (XR) reflectometry, it was determined that the average surface density of SiW12 was 2.10 x 10(-10) mol cm(-2), and the thickness increase per adsorption of PDDA-SiW12 was 1.7 +/- 0.2 nm, indicating that the amount of SiW12 anion per one layer adsorption corresponded to a monolayer coverage. Atomic force microscopy (AFM) was also used to examine the surface morphology and determine the grain size distribution and roughness for multilayer films. An increase in root-mean-square (RMS) surface roughness from 7 to 9 Angstrom was observed as the number of layer-pairs in the film increased from 2 to 6. FTIR results showed that the good stability of the multilayer films was due to Coulomb interactions between the SiW12 anion and the polymeric cations PDDA. Moreover, the multilayer films, in acidic aqueous solution, showed good electrocatalytic activity toward the reduction of NO2-, and the catalytic currents increased with increasing the layer numbers of SiW12 adsorption. These characteristics of the multilayer films might find potential applications in the field of sensors and microelectronics devices.

Layer-by-layer assembly of multilayer films consisting of silicotungstate and a cationic redox polymer on 4-aminobenzoic acid modified glassy carbon electrode and their electrocatalytic effects

A novel 4-aminobenzoic acid (4-ABA) monolayer film is formed on glassy carbon electrode (GCE) by amino cation radical method. Silicotungstic heteropolyanion (SiW12O404-, denoted as SiW12)-containing multilayer films have been fabricated on the 4-ABA modified GCE surface by alternate deposition with a quaternized poly(4-vinylpyridine) partially complexed with [Os(bpy)(2)Cl](2+/+) (denoted as QPVP-Os). Cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS) and X-ray reflectivity (XR) have been used to characterise the as-prepared multilayer films. It is proved that the multilayer films are uniform and stable. The average thickness for a bilayer of QPVP-Os/SiW12 in the multilayer film is 30.2 Angstrom. The electrocatalytic activities of the multilayer films have been investigated on the reduction of three substrates of important analytical interests, HNO2, BrO3- and H2O2. Especially, the influence of layer number of the multilayer films on the electrocatalytic reduction of HNO2 has been investigated in detail. (C) 2000 Elsevier Science B.V. All rights reserved.

Digital simulation in a thin layer spectroelectrochemical cell with minigrid platinum electrode by microregion approximation explicit finite difference method

The microregion approximation explicit finite difference method is used to simulate cyclic voltammetry of an electrochemical reversible system in a three-dimensional thin layer cell with minigrid platinum electrode. The simulated CV curve and potential scan-absorbance curve were in very good accordance with the experimental results, which differed from those at a plate electrode. The influences of sweep rate, thickness of the thin layer, and mesh size on the peak current and peak separation were also studied by numerical analysis, which give some instruction for choosing experimental conditions or designing a thin layer cell. The critical ratio (1.33) of the diffusion path inside the mesh hole and across the thin layer was also obtained. If the ratio is greater than 1.33 by means of reducing the thickness of a thin layer, the electrochemical property will be far away from the thin layer property.

Recent progress in the studies of endohedral metallofullerenes

This overview presents the recent progress in the area of endohedral metallofullerenes in the past several years. The important results have been summarized as follows: (1) Many metals including Group 3 metals, most of the lanthanide series elements, and Group 2 metals have been encapsulated into a fullerene cage to form mono-, di-, and trimetallofullerenes by using the arc-evaporation technique. (2) Some endohedral metallofullerenes such as Group 3 metals, most of the lanthanide series elements, Group 2 metals, and some of their isomers have been successfully isolated and purified by a two-step or several-step HPLC technique. By using high-temperature and high-pressure extraction with pyridine, Ln@C-80, Ln@C-82, and Ln2@C-80 for most rare-earth metals have been selectively extracted in high yield (about 1% of the saw soot) from fullerenes and other size metallofullerenes. (3) The endohedral nature of metallofullerenes such as Y@C-82, Sc2@C-84, and Sc@C-82 has been finally confirmed by synchrotron X-ray powder diffraction. The symmetries and the structures of metallofullerenes such as Ca@C-82(III), La-2@C-80(I-h), Sc-2@C-84(D-2d), and Sc-2@C-84(C-s) have been confirmed by NMR measurements. (Lb) The information on the electronic structures and properties of endohedral metallofullerenes has been obtained by various spectrometric means Such as EPR, W-vis-MR, XPS, CV. It is generally accepted that three-electron transfer is favorable when M = Y, La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Lu but Sc, Eu, Sm, Yb, Tm, Ca, Sr, Ba prefer to donate two electrons to the fullerene cages. (5) Several chemical reactions of endohedral metallofullerenes have been reported in which reagents are disilacyclopropane, digermacyclopropane, diphenyldiazomethane, and trifluoroacetic acid. (6) Mass spectrometry provided the crucial evidence that led to the discovery of metallofullerenes in 1985 and has always played a key role in their identification and characterization, Ion-mobility measurements of gas-phase ions have obtained the information of structures and the formation mechanism of endohedral metallofullerenes. till Theoretical calculations on the endohedral metallofullerenes have made an important contribution to the studies on the symmetry of the cage, the position of metal atom(s) inside the cage, the number of electronic transfer between metal atom(s) and fullerene cage, etc. (C) 2000 Elsevier Science S.A. All rights reserved.

肌苷在玻碳电极上的伏安法研究

应用线性扫描伏安法（LSV），微分脉冲伏安法（DPV）和循环伏安法（CV）对肌苷在玻碳电极（GCE）上的阳级伏安行为进行了研究，发现在0．1mol/L磷酸氢二纳溶液中，于1．42V（vs.Ag／AgCl）左右产生一个阳极氧化峰，峰电流与肌苷浓度在5×10-4～8×10-2g/L范围内呈线性关系，峰电位随溶液pH值增加而降低。肌苷在与次黄嘌呤、黄嘌呤、尿酸共存时，可得4个分辨良好的阳极氧化峰，它们的峰电位分别为1．42V、1．07V、0．72V和0．26V。用本法不需分离直接测定了药物针剂和加标尿样。实验结果表明肌苷的电极反应为扩散控制不可逆过程。

聚苯胺对2,5-二巯基-1,3,4-噻二唑氧化还原反应的电化学催化作用的循环伏安研究

研究了聚苯胺 ( PAn)膜电极在 2 ,5-二巯基 -1 ,3 ,4 -噻二唑 ( DMc T)溶液中电化学处理或浸泡后的循环伏安 ( CV)曲线的变化规律 .实验结果表明 ,PAn膜电极在 DMc T溶液中进行电化学处理或浸泡过程可使DMc T进入 PAn膜内部与 PAn形成复合物 .PAn对 DMc T的电化学催化作用可能和二者之间形成的电子给体 -受体复合物有关 .该复合物的电化学氧化还原特性不同于 PAn和 DMc T,其氧化还原反应速率和可逆性均优于 DMc T

环戊二烯—12-钼硅杂多四丁基铵电荷转移盐的合成、表征与晶体结构

以环戊二烯与 1 2 钼硅杂多四丁基铵为原料 ,采用光化学法合成了一种新型电荷转移盐 (Bu4N) 4(C5 H6 ) [HSiMoVI11MoVO40 ]。用元素分析、IR、CV、固体漫反射电子光谱、ESR进行了表征。X 射线晶体结构测定其晶体属三斜晶系 ,空间群P1 ,晶胞参数a =1 4.347(3) ,b =1 4.42 3(3) ,c =2 7.1 5 8(5 ) ,α =96 .90 (3) ,β =1 0 4.1 8(3) ,γ =98.2 0 (3)° ,V =5 32 2 (2 ) 3,Z =2 ,Mr=2 85 5 .30 ,Dc=1 .782 g·cm-3,F(0 0 0 ) =2 86 0 ,R =0 .0 71 9,wR =0 .1 983。标题化合物由 1个环戊二烯、4个Bu4N+阳离子和 1个 [SiMoVI11MoVO40 ]4 -阴离子构成。

Electrochemistry and spectroscopy study on the interaction of microperoxidase-11 with lipid membrane

The interaction of microperoxidase-11 (MP11) with cationic lipid vesicles of didodecyldimethylammonium bromide (DDAB) induces an alpha -helical conformation from random coil conformations in solution and this change then makes heme macrocycle more distorted. DDAB-induced MP11 conformations were investigated by cyclic votammetry (CV), circular dichroism (CD) and UV-vis spectrometry. All results indicate that the binding of MP11 in solution to DDAB vesicles and the ordered structure formation are driven by mostly electrostatic interaction between negatively charged residues in the undecapeptide and positively charged lipid headgroups on the membrane surface. Upon binding to DDAB, its half-peak potential was also changed. The mechanism of the interaction between MP11 and DDAB was also discussed. (C) 2001 Elsevier Science B.V. All rights reserved.

Synthesis, structure characterization and biological activity of a novel amino acid salt (HAla)(8)(H3O)(10)[PMo12O40](6) center dot 22H(2)O

A novel compound was synthesized and characterized by means of elemental analysis, IR and UV spectra, TG, CV and single crystal X-ray diffraction. The compound crystallized in an orthorhombic space group C222 with a=1. 622 4(3) nm, b=3. 498 4(7) nm, c=1. 301 5(3) nm, V=7. 387 (3) nm(3), Z=6, R-1= 0. 037 3, wR(2)=0. 114 0. The Ala (Ala = alanine) molecules were protonated at the amino nitrogen N (1) and the C (2) of Ala group with the terminal oxygen atom O(15), O(14), O(26) and O(27) of the polyoxometalates participating in the hydrogen bond network. The anti-tumor activity of the title compound was estimated against Hela and Pc-3m cancer cells.

双嘧达莫在玻碳电极上的阳极伏安法研究

用直流伏安法 (DCV) ,微分脉冲伏安法 (DPV)和循环伏安法 (CV)在玻碳电极 (GCE)上研究了双嘧达莫 (DPM)在不同介质中的阳极伏安行为 ,发现在 0 .0 1mol/LHCl溶液中于 0 6 2V(vs .Ag/AgCl)右左产生一个阳极氧化峰 ,其峰高与浓度的线性方程分别为y =0 0 0 0 4+0 17C(0 .0 5 ～ 1.0mg/L)和y =0 0 5 2 +0 2 2C(0 5～ 10mg/L) ,在此体系中大多数金属离子和 2 0多种有机生化物质不干扰测定。采用该方法可不经分离 ,直接测定药物制剂和尿样中DPM的含量。同时对DPM的电极反应机理进行了探讨

Fabrication and characterization of heteropolyanion Langmuir-Blodgett films

The possibility of the formation of Langmuir-Blodgett (LB) films with dimethyldioctadecylammonium (DODA) after the addition of cobalt(II)-substituted Dawson-type tungstodiphosphate anion (briefed as (H2O)(CoP2W17O618-)-P-11) in the subphase has been explored. Marked modifications of the compression isotherms are observed when this anion is dissolved in the subphase, which demonstrates that the polyanions interact with the monolayers. LB films have been readily obtained from this system. The adsorption Fourier transform IR (FT IR) spectroscopy, atomic force microscopy (AFM), X-ray diffraction (XRD) and cyclic voltammetry (CV) have been used to investigate the morphological and molecular structure of the deposited film. The FT IR results showed the presence of the polyanion within the LB films, and the shift for its characteristic bands may be related to the presence of positively charged DODA. AFM measurement reveals that the LB films of DODA/(H2O)(CoP2W17O618)-P-II are regularly and uniformly deposited on the substrate. XRD experiments prove that the lamellar structure of the LB films of DODA/(H2O)(CoP2W17O618-)-P-II is well-defined. The LB films of DODA/(H2O)(CoP2W17O618-)-P-II immobilized onto an indium-oxide (ITO) glass, in aqueous solutions of pH 2.0-5.0, show quite facile redox reactions even for multilayers. All the experiments carried out in the present study suggest that the new materials of heteropolyanions can be formed by LB techniques and beneficial physicochemical properties of heteropolyanions can be maintained/enhanced through molecular-level design. (C) 1999 Elsevier Science S.A. All rights reserved.

六氰亚铁酸镍修饰玻碳电极的现场红外光谱电化学研究

报道了一种制备六氰亚铁酸镍玻碳修饰电极(NiHCF/GC)的电化学方法,并用循环伏安(CV)和现场红外光谱电化学(FTIRs)方法对该修饰电极进行了研究.结果表明该电极上的NiHCF修饰膜有两种结构:Ni_2Fe(Ⅱ)(CN)_6和M_2NiFe(Ⅱ)(CN)_6,M为碱金属离子.M_2NiFe(CN)_6结构具有阳离子选择性,而阳离子对Ni_2Fe(Ⅱ)(CN)_6电化学反应的影响是间接的.FTLRs研究还表明在膜制备过程中Fe(CN)_6~(4-)发生了共沉积,其存在形式与支持电解质中阳离子的性质有关:在Na~+和Li~+溶液中,主要以桥式结构存在;而在K~-和H~-溶液中,主要为离子对形式.

循环伏安和现场红外光谱电化学研究镉(Ⅱ)在普鲁士蓝/铂修饰电极上的反应

报道了普鲁士蓝(PB)膜修饰Pt电极在CdCl_2溶液中进行循环伏安(CV)扫描,衍生为含有部分六氰亚铁酸镉(CdHCF)混合修饰膜的电化学反应,并对其反应机理进行了电化学和现场红外光谱电化学(FTIRs)的研究.实验结果表明,这一混合膜中PB和CdHCF两种成分之间的相互影响并不大,两种物质基本上保持了各自为纯物质时的电化学特性.

玻碳电极上六氰亚铁酸钯膜的现场FTIR光谱电化学研究

本文报道六氰亚铁酸钯膜修饰电极在HCL，KCL和NaCl溶液中的现场反射FTIR光谱电化学研究，结果表明该修饰膜具有内外两层结构，分别为Pd2Fe(CN)6和M2PdFe(CN)6，其中M为支持电解质一价阳离子．在1mol/L NaCl中，内层的氧化电位Em＝0.87V(vs．Ag/AgCl)，外层为0.77V．在1mol/L HCl或KCl中两层的氧化还原波重叠为一个大CV波峰而难以分辨，然而现场FTIR光谱电化学清晰地分辨出这两种结构在所有3种溶液中CN的不同振动频率，发现H+离子是最佳的支持电解质，能使这两种结构同时发生氧化反应