Electrochemical Behavior of Some Thiotriazoles in Aqueous‐Alcoholic Media at GCE

An electrochemical study related to the electrooxidation of 4‐amino‐3‐thio‐5‐methyl‐1,2,4‐triazole (I), 4‐amino‐3‐thio‐5‐phenyl‐1,2,4‐triazole (II) and 3‐thio‐5‐phenyl‐1,2,4‐triazole (III), in 10% v/v methanol‐acetate buffer pH 4.6 has been performed. A variety of electrochemical techniques such as differential pulse voltammetry, cyclic voltammetry, double‐potential step chronoamperometry, rotating‐disk electrode voltammetry and coulometry, were employed to clarify that the mechanism of the electrode process follows the oxidation of thiol compounds. All the compounds exhibit similar redox behavior under the given conditions. They display one irreversible oxidation peak, which is diffusion controlled. From the plot of current function in cyclic voltammetry and the ratio of i_c/i_a less than one in double‐potential step chronoamperometry, it was established that these compounds undergo an one electron oxidation followed by a dimerization process involving the formation of disulfide derivative (EC mechanism). The pK_a values were obtained by the dependence of limiting current and potential with in the wide pH interval. The transfer coefficients, the diffusion coefficients and rate constant of coupled chemical reaction were also reported. The substituent effects were also investigated.     

Characterization and Applications of a Bismuth Bulk Electrode

A bismuth bulk electrode (BiBE), a new solid‐state electrode, is presented. The polycrystalline metal bismuth disk‐shaped electrode was examined for its anodic stripping voltammetry performance, which was found to be well comparable to that achieved with the bismuth or mercury film electrodes. Useful potential windows of the BiBE in aqueous solutions of pH 1 to 13 were found to range from approximately ?1.7 to ?0.1 V, depending on pH, where either hydrogen evolution or anodic dissolution of metallic bismuth limit the electrochemical inertness of the BiBE. Employing cyclic voltammetry (CV), the cathodic behavior of the BiBE was examined by testing inorganic (cadmium(II) ions) and organic (2‐nitrophenol) model compounds; a CV quasi‐reversible behavior was recorded in the case of the Cd(II)‐Cd(0) couple. The characteristics of the BiBE under anodic conditions, i.e., at bismuth surface coated with a thin conductive Bi₂O₃ film, was examined by testing two well‐established redox systems, potassium hexacyanoferate(III) and ruthenium(III) hexaaminechloride; a nearly reversible behavior was recorded in the latter case. Based on the presented preliminary results, BiBE can be considered as an interesting alternative to common solid and (toxic) mercury electrodes for possible use in electrochemical studies and electroanalytical applications.     

Efficient electrosynthesis of 1,2,4-triazino[3,4-b]-1,3,4-thiadiazine derivatives

Electrochemical oxidation of catechols 1a-d has been studied in the presence of 4-amino-6-methyl-1,2,4-triazine-3-thion-5-one 3 as a nucleophile in aqueous solutions, using cyclic voltammetry and controlled-potential coulometry, leading to the efficient synthesis of 1,2,4-triazino[3,4-b]-1,3,4-thiadiazines.     

1,2,4-Triazines, 9. The synthesis of novel 4-amino-1,6-dihydro-1,2,4-triazinones

3-Alkylthio-4-amino-1,6-dihydro-1,2,4-triazin-5(4H)-ones were synthesized by the reduction of 3-thio-4-amino-1,2,4-triazine-3,5(2.H,4H)-diones and successive S-alkylation. The regiospecific alkylation on the N-1 position or the exo amino group leads to a variety of 1,6-dihydro-1,2,4-triazin-5(4H)-one derivatives. An alternative synthesis of 3-thio-4-amino-1,6-dihydro-1,2,4-triazine-3,5(2H,4H)-diones was accomplished through the cyclization of 1-thiocarbohydrazidoacetamide derivatives.     

An efficient electrochemical method for a unique synthesis of new derivatives of 7H-thiazolo[3,2-b]-1,2,4-triazin-7-one

The electrochemical oxidation of catechols (1a-c) has been studied in the presence of 6-methyl-1,2,4-triazine-3-thion-5-one 3 in aqueous sodium acetate, using cyclic voltammetry and controlled-potential coulometry. A plausible mechanism for the oxidation of catechols and their reaction with 3 is presented. All the catechol derivatives (1a-c) were converted into 7H-thiazolo[3,2-b]-1,2,4-triazin-7-one derivatives (6a-c) through a Michael-type addition reaction of 3 to anodically generated o-quinones. The electrochemical syntheses of 6a-c were successfully performed in one pot in an undivided cell using an environmentally friendly method with high atomic economy.     

Electrochemical and electrocatalytic studies of the N,N′-(1R,2R)-(–)-1,2-cyclohexylenebis(salicylideneiminato)cobalt(II) complex

The electrochemical properties and catalytic activity of a Co(II) complex with the optically active Schiff base derived from (1R,2R)-(–)-cyclohexanediamine and salicylaldehyde have been studied in non-aqueous solutions. When dissolved in deoxygenated non-aqueous solutions, the complex exhibits reversible redox properties for the Co(II)/Co(III) couple. Electrochemical reduction of oxygen and oxidation of cobalt(II) was observed on cyclic voltammograms of solutions containing both dioxygen and the Schiff base-cobalt(II) complex. An anodically formed film on a platinum electrode, studied by means of X-ray photoelectron spectroscopy, revealed the presence of the oxidized Co(III) species. Cyclic voltammetry of oxygenated solutions examined after a period of time indicates an electrochemical activity of coordinated superoxo/peroxo species in the 0.7–1.1 V potential range. In the presence of 4-methyl-1-cyclohexene the cyclic voltammetry curves reveal changes similar to those caused by the removal of oxygen. The GC-MS technique was used to identify some of the products formed by the catalytic oxidation of cyclohexene and 4-methyl-1-cyclohexene. Electronic Publication     

新型2H-噻唑[3,2-b][1,2,4]三嗪-3,7-二酮的超声辅助一锅法合成及乙酰胆碱酯酶抑制活性研究

以取代苯甲醛、溴乙腈和6-苄基-3-硫代-3,4-二氢-1,2,4-三嗪-5(2H)-酮为起始原料,在超声辅助下,一锅合成了9个新型6-苄基-2-亚苄基-2H-噻唑[3,2-b][1,2,4]三嗪-3,7-二酮类化合物,结构经_¹H NMR,_¹³C NMR和MS（ESI）表征并对其合成机理进行了初步研究。测试了目标化合物(4a~4i)的体外乙酰胆碱酯酶的抑制活性,其中4a和4d抑制活性最好,有进一步研究的价值。     

酸性介质中碘离子在铂电极上的电化学氧化行为

采用循环伏安法研究了酸性介质中碘离子在铂电极上不同电位区间, 不同酸度下的电化学反应行为. 结果表明, 当极化电位较低(小于0.6 V(vs Hg/Hg2SO4))时, 碘离子在铂电极上发生2I--2e→I2电氧化反应, 反应产物通过I2+I-=I-3被进一步溶解, 整个反应属于E-C(electrochemical-chemical)模式. 电氧化过程中可以形成碘膜, 其也可以被碘离子溶解. 当极化电位升高至0.6 V(vs Hg/Hg2SO4)或以上时, 碘离子会直接电氧化为高价态碘化合物, I-+3H2O→IO-3+6H++6e, 而析出的碘膜并不发生再氧化反应; 在电化学还原过程中, 出现了两个还原峰, 分别对应于I2、I-3的还原反应; 在无碘膜时, 碘离子电氧化过程受溶液中碘离子的液相扩散步骤控制; 碘膜形成后, 主要受碘膜中碘离子的固相扩散控制; 酸度对于碘离子的电化学氧化过程有很大的影响, 其线性极化曲线的起峰电位及电流峰值电位均随酸浓度升高而负移.     

Electro-inorganic synthesis: a convergent paired electrochemical synthesis and voltammetric studies of copper(II)-2-aminophenol derivatives

Electrochemical reduction of 2-nitrophenol and 5-methyl-2-nitrophenol has been studied in water/ethanol mixture using cyclic voltammetry and controlled-potential coulometry. Our voltammetric data indicate the formation of 2-aminophenol (HL^I) and 5-methyl-2-aminophenol (HL^II), respectively. Also, the electrochemical synthesis of copper(II) complex of 2-aminophenols has been carried out using copper metal as a sacrificial anode and lead metal as a cathode in water/ethanol (50/50 v/v). The electrochemical synthesis of copper(II)-2-aminophenols consists of a multi-step such as (a) cathodic reduction of 2-nitrophenols to related 2-aminophenols, (b) generation of Cu²⁺ from copper anode, (c) complexation of 2-aminophenols with Cu²⁺. In this work, we have proposed a mechanism for the electrode process. Some parameters such as electrode material, current density, electricity passed and temperature, were also systematically studied. The convergent paired electrochemical synthesis of copper(II) complex of 2-aminophenols has been successfully performed in a one-pot process, under constant current condition in an undivided cell, in a good yield and purity. Also, the electrochemical behavior of copper(II)-2-aminophenol complex was studied and the stability constant of copper(I)-2-aminophenol complex was evaluated using cyclic voltammetry.     

Electrochemical behavior in simulated body fluid of TiO2 nanotubes on TiAlNb alloy elaborated in various anodizing electrolyte

The present study is focused on tailoring the morphology of TiO₂ nanotubes obtained on Ti6Al7Nb alloy and evaluating their electrochemical behavior in simulated body fluid. The presence of the α and β phases on the Ti6Al7Nb alloy leads to a two‐scale organization of the nanotubes on the samples – which in turn affects the electrochemical stability. Furthermore, five different types of TiO₂ nanotubes were obtained in various electrolytes (e.g. Generation I, a mixture of Generation II and Generation III, Generation III). Electrochemical behavior analysis of all obtained nanotubes morphologies was composed of Tafel plots, cyclic voltammetry and electrochemical impedance spectroscopy and was correlated with morphology data obtained from SEM (nanotubes diameters from top‐view and nanotube length from cross‐section view). The electrochemical results showed that morphological modifications of the Ti6Al7Nb alloy's surface by electrochemical anodizing have induced changes to the electrochemical behavior of the material, evident in the corrosion rates. Copyright © 2014 John Wiley & Sons, Ltd.     

Electrochemical Reduction of 1,2-Di（p-tolylimino）ethane and 1,2-Di（2,4-dimethylphenylimino）ethane in Dimethylformamide

1,2-Di（p-tolylimino）ethane （Ⅰ） and 1,2-Di（2,4-dimethylphenylimino）ethane （Ⅱ） were synthesized and their electrochemical behavior investigated in dimethylformamide using classical voltammetry, differential pulse voltammetry, cyclic voltammetry, chronoamperometry, controlled potential electrolysis and coulometry. Both bis-Schiff base ligands examined show a cathodic irreversible peak which corresponds to one-electron reduction of the substrate to form anion radical. According to the fact obtained from cyclic voltammetry, that the current function （ip/v^1/2） is a decreasing function of the scan rate, it can be concluded that there is a following coupling chemical reaction （EC mechanism）. Thus, the most probable mechanism of electroreduction of both ligands is the coupling of two radicals to form a dimer.     

Reduced Graphene Oxide Impregnated Antimony Nanoparticle Sensor for Electroanalysis of Platinum Group Metals

A very sensitive electrochemical sensor based on a reduced graphene oxide film impregnated with antimony nanoparticles was prepared and applied to the electroanalysis of platinum group metal ions of Pd(II), Pt(II) and Rh(III). The electrochemical behavior of platinum group metals at the modified electrode was studied by adsorptive differential pulse cathodic stripping voltammetry in the presence of dimethylglyoxime as chelating agent. Several operational parameters were optimised to enhance the electroanalytical performance of the modified glassy carbon electrode sensor. The results showed sharp stripping peaks and a relatively constant peak potential with a good linear behaviour in the examined concentration range from 40 to 400 pg L^?1 for all metal ions investigated. The detection limit was found to be 0.45, 0.49 and 0.49 pg L^?1 (S/N=3) for Pd(II), Pt(II) and Rh(III), respectively. The developed electrochemical sensor also exhibited good precision with a relative standard deviation of 4.2 %, 2.55 % and 2.67 % for 5 successive measurements for Pd(II), Pt(II) and Rh(III), respectively. The proposed nanostructure showed good sensitivity and stability, which has promising potential applications in electrochemical sensors.     

Electrochemical and spectroscopic characterization of anodically formed nickel salen polymer films on glassy carbon, platinum, and optically transparent tin oxide electrodes in acetonitrile containing tetramethylammonium tetrafluoroborate

Anodically polymerized films of nickel salen formed on glassy carbon, optically transparent tin oxide, and platinum electrodes in acetonitrile containing tetramethylammonium tetrafluoroborate have been examined by means of cyclic voltammetry, thin-layer voltammetry, spectroelectrochemistry, and scanning electron microscopy. With the aid of thin-layer voltammetry, it has been confirmed that the global oxidative polymerization of nickel(II) salen involves three electrons per monomer. Polymerization proceeds through two distinct phases, the formation of which depend on the potential. Once the polymer film has been formed, the anodic process consists of the reversible one-electron nickel(III)/nickel(II) redox couple. Cyclic voltammetry along with spectroelectrochemistry has been employed to probe the roles of the nickel(III)/nickel(II) and nickel(II)/nickel(I) redox couples in the electrochemical response of the polymer film as well as the interconversion of the different oxidation states of nickel.     

卡托普利在汞电极表面的电化学行为

用循环伏安法、阴极溶出伏安法和电毛细管曲线测量等方法研究了卡托普利在汞电极表面的电氧化机理。实验结果表明,酸性溶液中卡托普利比较稳定,而在中、碱性溶液中卡托普利不稳定。在酸性溶液中有质子参与电极过程,卡托普利在电极表面发生单电子转移,生成汞（Ｉ）－硫化合物,该化合物在电极表面有强吸附,并进一步转化成汞（Ⅱ）－硫化合物。按照实验结果,计算了卡托普利的扩散系数和电极反应速率常数,提出了卡托普利电化学氧     

Electrochemical Behavior of Azo Compounds in Liquid Ammonia

Abstract

At -40°C, the behavior of lO compounds, differing widely in their standard potentials, has been investigated in liquid ammonia, using cyclic voltammetry at a smooth platinum electrode. The purpose of this study was the realization of a redox scale with reversible systems. With azobenzene, pyridazine, cin-noline, benzocinnoline and 4,4′-azobis-(pyridine-N-oxide), the first electron transfer is reversible and leads to the formation of the corresponding radical anions which are stable; the second electron transferleads to the ciianions which can be protonated yielding the corresponding hydrazo. Other compounds, such as azoxybenzene, 3-amino-1,2,4-triazine, pyridine-N-oxide, 8-azaadenine and 1H-tetrazole, have an electrochemical behavior which i s more intricate.     

Synthesis and characterization of a new Schiff base derived from 2,3-diaminopyridine and 5-methoxysalicylaldehyde and its Ni(II), Cu(II) and Zn(II) complexes. Electrochemical and electrocatalytical studies

We describe the synthesis and characterization of a new tetradentate Schiff base ligand obtained from 2,3-diaminopyridine and 5-methoxysalicylaldehyde. This ligand (H₂L) reacted with nickel(II), copper(II), and zinc(II) acetates to give complexes. The ligand and its metal complexes were characterized using analytical, spectral data (UV–vis, IR, and mass spectroscopy), and cyclic voltammetry (CV). The crystal structure of the copper complex was elucidated by X-ray diffraction studies. The electrochemical behavior of these compounds, using CV, revealed that metal centers were distinguished by their intrinsic redox systems, e.g. Ni(II)/Ni(I), Cu(II)/Cu(I), and Zn(II)/Zn(I). Moreover, the electrocatalytic reactions of Ni(II) and Cu(II) complexes catalyze the oxidation of methanol and benzylic alcohol.     

The determination of some 2-thiobarbiturates by cathodic stripping voltammetry

Pulse polarography and cyclic voltammetry are employed in studies of the electrochemical behaviour of 5-ethyl-5'-(l-methylbutyl)-2-thiobarbituric acid (I), l-methyl-5-ethyl-5'-(l-methylpropyl)-2-thiobarbituric acid (II) and l,3-dimethyl-5-ethyl-5'-p-chlorophenyl)-2-thiobarbituric acid (III) in the pH range 4–12. All three compounds show anodic and cathodic waves or peaks in this pH range. Compounds (I) and (II) are oxidized at mercury indicator electrodes to produce mercury salts which can adsorb thereon and are thus amenable to cathodic stripping voltammetric analysis (c.s.v.) down to concentrations of the order of 10^-6 M, which is superior to the sensitivities obtained by differential pulse polarography (d.p.p.) based on a reduction peak. Compound (III) oxidizes to produce sulphur which is subsequently plated as HgS. Again the sensitivity of the c.s.v. method is of the order of lO^-6 M and analytically superior to d.p.p. The optimum pH for the three determinations is 8. The determination of (II) in the presence of its oxygenated analogue and metabolite, phemitone, and the effect of chloride ions are reported.     

The synthesis of 5H-thiazolo[2,3-c][1,2,4]triazine derivatives and substituted 3-(2-acylvinylthio)-1,2,4-triazin-5-ones from 6-methyl-3-thioxo-1,2,4-triazin-5-one, 1-acyl-2-bromoacetylenes,and α-acetylenic ketones. X-ray study of 3-benzoyl-6-methyl-5H-thiazolo[2,3-c][1,2,4]triazin-5-one

3-Acyl-6-methyl-5H-thiazolo[2,3-c][1,2,4]triazines were synthesized by reaction of 1-acyl-2-bromoacetylenes with 6-methyl-3-thioxo-1,2,4-triazin-5-one in methanol in the presence of triethylamine at 20 °C. The structure of 3-benzoyl-6-methyl-5H-thiazolo[2,3-c][1,2,4]triazine was established by X-ray structural analysis. Substituted 3-(2-acetylvinylthio)1,2,4-triazin-5-ones were obtained by the reaction of -acetylenic ketones with 6-methyl-3-thioxo-1,2,4-triazin-5-one under the same conditions. The structures of the new compounds were confirmed by IR,¹H, and¹³C NMR spectroscopy.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2971–2975, December, 1996.     

胆红素LB膜的电化学行为研究

胆红素（BR）是存在于动物体内的一种重要生物物质，也是人和绝大多数哺乳动物体内血红蛋白等含铁卟啉化合物分解代谢的产物和代谢中间体。它是一种内源性抗氧化剂，对肝细胞的再生具有积极的作用，BR常以线状四吡咯或类卟啉结构的形式存在。胆红素及其金属配合物在水溶液犤１～６犦与有机介质（如DMF和DMSO）犤７～９犦中的电化学行为，文献上已有较多报道。前文犤１０～１２犦我们报道了胆红素可在不同亚相（酸性、中性及部分金属离子）表面形成Langmuir－Blodgett（LB膜）；在有磷脂存在时，其成膜性能更佳犤１３犦。由于LB膜同生…     

Electrochemical Formation of Al-Li Alloys by Codeposition of Al and Li from LiCl-KCl-AlF3 Melts at 853 K

The electrochemical behavior of Al(III) ions was studied in molten LiCl-KCl melts on a molybdenum electrode. Cyclic voltammetry, chronopotentiometry and chronoamperometry were used to explore the deposition mechanism of Al and Li. Cyclic voltammetry expriment indicates that under potential deposition(UPD) of lithium on pre-deposited aluminium led to the formation of liquid Al-Li alloys at 853 K. The diffusion coefficient of Al(III) ions at 853 K in LiCl-KCl-AlF₃(1%, mass fraction) melts was determined to be (2.79±0.05)×10^?5 cm²/s. Chronopotentiograms and chronoamperograms demonstrate that the codeposition of Al(III) and Li(I) ions formed Al-Li alloys at cathodic current densities higher than ?0.28 A/cm² or cathodic potentials more negative than ?2.20 V. X-Ray diffraction(XRD) pattern indicates that Al-Li alloys with different phases formed via galvanostatic electrolysis. Inductively coupled plasma(ICP) analyses of the samples obtained by electrolysis show that lithium and aluminium contents of Al-Li alloys could be controlled by AlF₃ concentration and current intensity.