二苯并四硫代富瓦烯类衍生物的合成和电化学行为

合成了四个二苯并四硫代富瓦烯(DB-TTF)的衍生物(3a～b, 4a～b), 给出了它们的核磁共振氢谱和碳谱, 质谱,紫外吸收光谱及元素分析等数据. 用=循环伏安法测定了它们的氧化电位, 并将此与DB-TTF的氧化电位作了比较.发现: 两端取代的硫酮基对分子体系的吸电子效应较强,会明显增大分子的第一氧化电位 , 而且会降低分子内的Coulomb作用力, 相比之下, 在四周顶点上取代的烷氧基对分子体系的给电子效应较弱.     

Comparison of fast scan voltammetry with microelectrode voltammetry of reduction of 1,4-benzoquinone

The reduction of 1,4-benzoquinone (BQ) in acetonitrile was blocked in steady-state microelectrode voltammetry although it has been believed to be a sluggish electron transfer reaction. Ferrocene was added to the BQ solution with equi-concentration in order to confirm the diffusion-control step and to evaluate accurately the kinetic effect from potential differences. Fast scan voltammograms showed the negative potential shifts both of the cathodic and the anodic peaks with an increase in the scan rate. In contrast, microelectrode voltammetry showed that the ratio of the steady-state limiting current for BQ to that for ferrocene decreased with a decrease in the electrode radii. The halfwave potential of the reduction of BQ did not vary with the radii within error. These features are largely deviated from the Butler–Volmer kinetic behavior. The electrode surface after the long term electro-reduction was coated with a precipitate. The proposed reaction mechanism is formation of films by follow-up chemical reactions of BQ associated with slight potential shift. The film blocks diffusion of BQ. This model was theoretically formulated and elucidated the experimental results.     

Ultrafast synthesis of near-infrared-emitting aqueous CdTe/CdS quantum dots with high fluorescence

The traditional aqueous route to synthesis CdTe/CdS Core/shell (c/s) quantum dots (QDs) via decomposition of Cd-thiol complexes is usually time consuming. Herein, an ultrafast and facile aqueous synthetic approach under atmospheric pressure for CdTe/CdS c/s QDs with emission from the green to the near-infrared window (535–820 nm) is reported. With purified CdTe core QDs diluted in solution of Cd-3-mercaptopropionic acid (MPA) complexes, CdTe/CdS c/s QDs with emission wavelengths at 700 and 800 nm can be obtained within 20- and 45-min refluxing under the optimized experimental conditions, respectively. This is the most rapid way to prepare CdTe/CdS c/s QDs in aqueous phase, and the obtained QDs were highly luminescent without postsynthesis treatment. The influences of various experimental factors, including Cd²⁺ concentration, MPA-to-Cd ratio, pH value, and dilution ratio on the growth rate and luminescent properties of the obtained CdTe/CdS c/s QDs, have been taken into consideration. The three processes “purification-dilution-addition” ensure the synthesis environment with high pH value and low core concentration and have a marked impact on the rapid synthesis rate and the resulting high fluorescence of CdTe/CdS c/s QDs.     

Nonbonding pairs in cyclic thioethers: Electrostatic modeling and ab initio calculations for complexes of 2,5-dihydrothiophene,thietane, and thiirane with hydrogen fluoride

Electrostatic potential energies V(ϕ) of a non-perturbing, protonic charge at fixed distances r from the S atom in three cyclic thioethers were examined as functions of the angles ϕ made by the r-vector with the C₂ axis (thiirane and 2,5-dihydrothiophene) or the local C₂ axis (thietane). The electrostatic PE V_HF(ϕ) of HF (HF modelled as an extended electric dipole) was also calculated and the results compared with geometries of the thioether⋯HF complexes calculated at the CCSD(T)-F12c/cc-pVTZ-F12 level. The latter reveal angular deviations θ ∼10-20° of the S⋯H F nuclei from collinearity in directions suggesting secondary interactions of F with H atom(s) of the rings. Angles ϕ made by the S⋯H hydrogen bond with the C₂ (or local C₂) axes in the complexes are systematically larger (∼4-9°) than indicated by the V_HF(ϕ) functions. Minima in the simple V(ϕ) versus ϕ functions occur at values smaller (∼5-10°) than those in the V_HF(ϕ) curves.     

Differentiation between o- and p-quinol/quinone functionality with a simple test using cyclic voltammetry

Complexation with boric acid combined with cyclic voltammetry serves to prove theo-quinol/quinone functionality in emmotin H (1) and I (2). Supported by similar investigation of four reference compounds the method is suggested as a quick and reliable test ofo-quinol/quinone functionality and for differentiation fromp-quinol/quinone functionality. Voluminous groups such as 2-isopropanolyl ino-position do not interfere with the complex formation. The test requires quantities of materials in the order of 10 to 100g.     

Fast Fourier transformation with continuous cyclic voltammetry at an Au microelectrode for the determination of morphine in a flow injection system

For the fast morphine monitoring in flow injection systems a highly sensitive method is being introduced in this work. The fast Fourier transformation with continuous cyclic voltammetry (FFTCV) in a flowing solution as a detection system was applied for the prompt morphine monitoring. Here it should be stressed that this technique is simple, precise, accurate, time saving and economical. This research includes the observation of the effects of various parameters on the sensitivity of the detection system. Eventually, it was concluded that the best condition was obtained within the pH value of 2, scan rate value of 40 V s⁻¹, accumulation potential of 400 mV and accumulation time of 0.6 s.In detail, the noteworthy advantages which this method illustrates in comparison with other reported methods are the following; no necessity for the oxygen removal from the test solution, a sub-nano molar detection limit and the fast determination of any such compound in a wide variety of chromatographic methods.The method proved to be linear over the concentration range of 285-305,300 pg mL⁻¹ (r = 0.999) with a detection limit and a quantitation limit of 95.5 and 285 pg mL⁻¹, respectively. Consequently, the method illustrates the requisite accuracy, sensitivity, precision and selectivity to assay morphine in its tablets and biological fluids.     

Study of electrochemical oxidation of nickel catecholate complexes with bis(diphenylphosphino)ethane by cyclic voltammetry and ESR

One-and two-electron electrochemical oxidation of the (dppe)Ni(Cat) complexes (dppe is bis(diphenylphosphino)ethane, Cat is the sterically hindered catechol dianion) was studied. The transfer of the first electron proceeds reversibly to give paramagnetic species; parameters of their EPR spectra attest to a square planar geometry of one-electron oxidation products. The transfer of the second electron is irreversible because of co-proportionation of radical cations involving the initial complexes and the generated dications. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 99–102, January, 2007.     

Characterization of conducting copolymers of 2,2′-bithiophene and pyrrole by cyclic voltammetry and UV/visible spectroscopy

Several polymers have been prepared by electropolymerization of mixtures of pyrrole (PY) and 2,2′-bithiophene (BT). Cyclic voltammetry on prepared polymer films shows three anodic oxidation peaks, two of which match the oxidation potentials of homopolymeric PY and BT, and a third which is intermediate. UV/visible spectroscopy displays a unique spectrum for each of the reduced and oxidized forms of these polymers. Nernstian plots from UV/visible data exhibit three well-defined redox couples in polymer films produced at 1.3 V. Overall, the data strongly support the formation of a copolymer, consisting of three distinct oxidizable units. Two of these can be attributed to short blocks of either PY or BT, and a third to random and alternate groupings of PY and BT. The polymers produced are electrically conductive, but the conductivity drops rapidly as BT units are introduced into a homopolymer of PY. © 1992 John Wiley & Sons, Inc.     

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.     

Solution of equation for a current-voltage curve describing reversible metal electrodissolution with linear boundedly semi-infinite diffusion and a linear alteration of potential in the stripping voltammetry method

An exact, sufficiently simple, explicit expression is obtained and a full contour of the stripping-voltammetry peak is calculated for a reversible process on a thin-film mercury electrode of finite thickness (linear boundedly semi-infinite diffusion is taken into account) in conditions of stripping voltammetry at a linearly altering potential. That these results were obtained at all, is due to use made of two extra boundary conditions (Nemovs and Nazarovs). The addends in the four forms of equations derived are the limiting expressions and corrections in the form of Nemovs or Nazarovs boundary conditions. It is shown that it is advisable to employ different forms of equations at large and small values of parameter H. The peaks height, full width at half-maximum, and potential are found to depend on H.Translated from Elektrokhimiya, Vol. 41, No. 1, 2005, pp. 54–68.Original Russian Text Copyright © 2005 by Nazarov, Stromberg.To the Centennial of B.N. Kabanov.Deceased.     

A potential with low point charges for pure siliceous zeolites

A modified CHARMM force‐field (ZHB potential) with low point charges for silica was previously proposed by Zimmerman et al. (J. Chem. Theory Comput. 2011, 7, 1695). The ZHB potential is advantageous for quantum mechanics/molecular mechanics simulations as it minimizes the electron spill‐out problems. In the same spirit, here we propose a modified ZHB potential (MZHB) by reformulating its bonding potential, while retaining the nonbonding potential as in the ZHB force‐field. We show that several structural and dynamic properties of silica, like the IR spectrum, distribution functions, mechanical properties, and negative thermal expansion computed using the MZHB potential agree well with experimental data. Further, transferability of MZHB is also tested for reproducing the crystallographic structures of several polymorphs of silica. © 2015 Wiley Periodicals, Inc.     

高阳极电势窗口的SnO2-Sb2O3/Ti电极的制备

制备了不同热处理温度和涂层次数的SnO2-Sb2O3/Ti电极,研究了不同电极涂层的氧化物组成,涂层表面形貌和阳极电势窗口及其三者的内在关系,考察了不同制备工艺条件的电极对电催化高铁性能的影响.结果表明430℃是电极最佳的热处理温度,涂层次数增加为30次时,电极具有高的阳极电势窗口,同时能降低高铁氧化还原反应的超电势,更真实的展现高铁电化学生成的热力学原貌.     

Quantitative analysis of boldine alkaloid in natural extracts by cyclic voltammetry at a liquid-liquid interface and validation of the method by comparison with high performance liquid chromatography

The quantitative determination of boldine alkaloid in boldo leaf extracts by employing cyclic voltammetry, at a liquid/liquid interface as well as the validation of this methodology against the reference method, high performance liquid chromatography (HPLC), are reported in the present paper. The voltammetric analysis was performed successfully and economically using two kinds of liquid/liquid interfaces: water/1,2-dicholoroethane and water/PVC (polyvinyl chloride)-gelled 1,2-dichloroethane. Linear calibration curves in the concentration range of 1.04 × 10⁻⁵ mol L⁻¹ to 5.19 × 10⁻⁴ mol L⁻¹ were obtained with a detection limit equal to (6.1 ± 0.7) × 10⁻⁵ mol L⁻¹ and the quantitative determination of this alkaloid, in complex matrixes such as boldo leaf extracts, by the electrochemical technique proposed was found to be equal to the values obtained using the standard HPLC method. The validation analysis of this methodology against HPLC demonstrated that accuracy, linearity, limit of detection (LOD), limit of quantification (LOQ), specificity and precision are acceptable. The electroanalytical technique proposed is economical and selective, involves simple equipment and can be applied for the quantitative determination of boldine alkaloid in complex matrixes such as leaf extracts without special drug separation. Moreover, cyclic voltammetry (CV) experiments applied at the liquid/liquid interface under different experimental conditions allowed us to study the transfer mechanism of boldine, and determine a value of pK_a^w = 6.90 for protonated boldine, from the variation of voltammetric peak current with pH.     

Assignment of absolute configuration of cyclic secondary amines by NMR techniques using Mosher's method: a general procedure exemplified with (-)-isoanabasine

A general procedure to determine the absolute configuration of cyclic secondary amines with Mosher's NMR method is demonstrated, with assignment of absolute configuration of isoanabasine as an example. Each Mosher amide can adopt two stable conformations (named rotamers) caused by hindered rotation around amide C--N bond. Via a three-step structural analysis of four rotamers, the absolute configuration of (-)-isoanabasine is deduced to be (R) on the basis of Newman projections, which makes it easy to understand and clarify the application of Mosher's method to cyclic secondary amines. Furthermore, it was observed that there was an unexpected ratio of rotamers of Mosher amide derived from (R)-isoanabasine and (R)-Mosher acid. This phenomenon implied that it is necessary to distinguish the predominant rotamer from the minor one prior to determining the absolute configuration while using this technique.     

Hidden in plain sight: unlocking the full potential of cyclic voltammetry with the thin-film rotating (ring) disk electrode studies for the investigation of oxygen reduction reaction electrocatalysts

Cyclic voltammetry conducted with a thin-film rotating disk electrode, or ring-disk electrode (CV-TF-R(R)DE) is a very popular ‘ex situ’ tool for the rapid screening of electrocatalysts for their activity in oxygen reduction reaction. Despite its popularity and broad use, in most instances only a small part of the information that could be accessed by CV-TF-R(R)DE is actually used by scientists in their research. This work outlines both innovative and more traditional (but half-forgotten) ways of using CV-TF-R(R)DE to its optimal or full potential in the ongoing quest to study the most relevant features of oxygen reduction reaction electrocatalysts and quickly identify the most promising candidates for their applications in fuel cells or other electrochemical devices.     

Development of a potential method based on microchip electrophoresis with fluorescence detection for the sensitive determination of intracellular thiols in RAW264.7 cells

This paper, for the first time, reported the development of a simple, rapid, and reliable method for the separation and sensitive determination of four thiol compounds including homocysteine, cysteine, glutathione, and N‐acetylcysteine based on glass MCE with fluorescence detection using a highly reactive fluorogenic probe, 1,3,5,7‐tetramethyl‐8‐phenyl‐(2‐maleimide)‐difluoroboradiaza‐s‐indacene (TMPAB‐o‐M), as the labeling reagent. TMPAB‐o‐M reacted selectively with thiols to produce highly fluorescent derivatives and the highest derivatization efficiency was achieved within 6 min in physiological conditions. After the optimization of separation conditions, a baseline separation of the four thiol compounds was achieved with the detection limits ranging from 2 nM for glutathione to 4 nM for cysteine (S/N = 3) and RSDs (n = 5) in the range of 3.2–3.8%. The proposed method was significantly sensitive compared to those using electrochemical or even LIF detection in MCE‐based setup reported previously, and applied to the determination of intracellular thiols in macrophage RAW264.7 cells.     

Chemical, spectroscopic characterization, DFT studies and initial pharmacological assays of a silver(I) complex with N-acetyl-l-cysteine

A new silver(I) complex with N-acetyl-l-cysteine (NAC) of composition AgC₅H₈NO₃S·H₂O was synthesized and characterized by a set of chemical and spectroscopic measurements. Solid-state ¹³C nuclear magnetic resonance (SSNMR) and infrared (IR) analyses indicate the coordination of the ligand to Ag(I) through the sulfur atom. The Ag-NAC complex is slightly soluble in dimethyl sulfoxide. It is insoluble in water, methanol, ethanol, acetone and hexane. Antibacterial activity of the silver complex with N-acetyl-l-cysteine (Ag-NAC) was evaluated by antibiogram assays using the disc diffusion method. The compound showed an effective antibacterial activity against Staphylococcus aureus (Gram-positive), Escherichia coli and Pseudomonas aeruginosa (Gram-negative) bacterial cells. Biological analysis for evaluation of a potential cytotoxic effect of Ag-NAC was performed using HeLa cells derived from human cervical adenocarcinoma. The complex presented a significant cytotoxic activity, inducing 80% of cell death at a concentration of 200 μmol L⁻¹.     

Paper-based solid-state electrochemiluminescence sensor using poly(sodium 4-styrenesulfonate) functionalized graphene/nafion composite film

Herein, highly efficient solid-state ECL sensor was introduced for the first time onto the screen printed electrodes of the paper-based chips (PCs) based on the composite film of poly(sodium 4-styrenesulfonate) functionalized graphene (PSSG) and Nafion. Attributed to the cooperative characteristics of both PSS and graphene, PSSG ensured both effective Ru(bpy)₃²⁺ immobilization and fast electron transfer of Ru(bpy)₃²⁺ in the composite film. The ECL behaviors at the developed sensor were investigated using tripropylamine as a representative analyte and low detection limit (S N⁻¹ = 3) of 5.0 nM was obtained. It also exhibited more excellent reproducibility (relative standard deviations of 0.63% for continuous 45 cycles) and long-term stability (∼80% of its initial ECL intensity could be retained over 3 months). More importantly, assisted by the developed ECL sensor, discrimination of 1.0 nM single-nucleotide mismatch in human urine matrix could be realized on the PCs for the first attempt. Thus, the developed sensor was confirmed with the advantages of highly sensitivity, long-term stability, simplicity, low cost, disposability, high efficiency and potential applicability.