液流电池正极活性物质钛铁试剂初探

应用循环伏安法研究钛铁试剂(4,5-二羟基-1,3-苯二磺酸钠)电对(石墨基底)在水溶液中的电化学行为.实验表明,溶液pH<4时,该试剂的氧化还原反应电位较高,可逆性好.以其作正极与V(III)/V(II)负极组成液流电池,在硫酸介质中,充放电库仑效率可达90%以上,而且循环寿命较好,性能衰减小,具备作为液流电池正极活性物质的可行性.     

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     

间苯二胺的电化学及紫外-可见薄层光谱电化学研究

研究了间苯二胺(MPD)在金电极和SnO₂;F膜电极上的循环伏安行为及在SnO₂;F膜电极上的紫外-可见薄层光谱电化学性质.获得了间苯二胺在SnO₂;F膜电极上电氧化的薄层恒电势电解-吸收光谱图,采用双对数法对紫外-可见薄层光谱电化学数据进行了处理.研究了间苯二胺的光谱及电化学性质,求得了间苯二胺的动力学修饰式量电位E⁰和αn等热力学参数.     

Nickel(II) Complex of N4 Schiff Base Ligand as a Building Block for a Conducting Metallopolymer with Multiple Redox States

Metal–ligand interactions in monomeric and polymeric transition metal complexes of Schiff base ligands largely define their functional properties and perspective applications. In this study, redox behavior of a nickel(II) N₄-anilinosalen complex, [NiAmben] (where H₂Amben = N,N′-bis(o-aminobenzylidene)ethylenediamine) was studied by cyclic voltammetry in solvents of different Lewis basicity. A poly-[NiAmben] film electrochemically synthesized from a 1,2-dichloroethane-based electrolyte was investigated by a combination of cyclic voltammetry, electrochemical quartz crystal microbalance, in situ UV-Vis spectroelectrochemistry, and in situ conductance measurements between −0.9 and 1.3 V vs. Ag/Ag⁺. The polymer displayed multistep redox processes involving reversible transfer of the total of ca. 1.6 electrons per repeat unit, electrical conductivity over a wide potential range, and multiple color changes in correlation with electrochemical processes. Performance advantages of poly-[NiAmben] over its nickel(II) N₂O₂ Schiff base analogue were identified and related to the increased number of accessible redox states in the polymer due to the higher extent of electronic communication between metal ions and ligand segments in the nickel(II) N₄-anilinosalen system. The obtained results suggest that electrosynthesized poly-[NiAmben] films may be viable candidates for energy storage and saving applications.     

Redox protein-polymer films for simultaneous determination of ascorbic Acid and hydrogen peroxide

Layer by layer films of protein and redox polymer were constructed and used to simultaneously analyze ascorbic acid and hydrogen peroxide. The films were made using hemoglobin and poly[4-vinylpyridine Os(bipyridine)(2)Cl]-co-ethylamine (Pos-Ea). The film growth was monitored using cyclic voltammetry, quartz crystal microbalance (QCM) and atomic force microscopy (AFM). Reversible pairs of oxidation-reduction peaks were observed using cyclic voltammetry corresponding to the Os(II)/Os(III) from redox polymer and HbFe(III)/HbFe(II) redox couples at 0.35 and -0.25 V vs. Ag/AgCl, respectively. The two redox centers were independent of each other. This enabled the simultaneous and independent determination of ascorbic acid and hydrogen. Peak currents were linearly related to concentration for both analytes in a mixture. The linear range of ascorbic acid was 0 - 1 mM (R(2) = 0.9996, n = 5) at scan rate of 50 mV s(-1) (sensitivity 3.5 microA/mM) while hydrogen peroxide linear range was 1.0 - 10.0 microM (R(2) = 0.991, n = 6) with sensitivity of 1.85 microA/microM.     

Spectroelectrochemical characterisation of poly[Ni(saltMe)]-modified electrodes

Electrogenerated polymers based on the nickel(II) complex 2,3-dimethyl-N,N'-bis(salicylidene)butane-2,3-diaminatonickel(II), poly[Ni(saltMe)], were characterised by in situ FTIR and UV/Vis spectroscopy and ex-situ EPR spectroscopy in order to gain insights into film structure, electronic states and charge conduction. The role of the nickel ions during film oxidation was probed by using EPR to study naturally abundant Ni and 61Ni-enriched polymers. The data from all the spectroscopic techniques are consistent, and clearly indicate that polymerisation and redox switching are associated with oxidative ligand based processes; coulometry suggests that one positive charge was delocalised through each monomer unit. EPR provided evidence for the non-direct involvement of the metal in polymer oxidation: the polymer is best described as a polyphenylene-type compound (conducting polymer), rather than an aggregation of nickel complexes (redox polymer), and the main charge carriers are identified as polarons. An explanation for the high electrochemical stability and conductivity of poly[Ni(saltMe)] with respect to that of poly[Ni(salen)] is proposed. based on stereochemical repulsion between monomeric units; this can impose a less compact supramolecular structure on polymers with bulkier substituents.     

Voltammetric Determination of Mercury(II) at Poly(3‐hexylthiophene) Film Electrode. Effect of Halide Ions

The well‐known method for the determination of mercury(II), which is based on the anodic stripping voltammetry of mercury(II), has been adapted for applications at the thin film poly(3‐hexylthiophene) polymer electrode. Halide ions have been found to increase the sensitivity of the mercury response and shift it more positive potentials. This behavior is explained by formation of mercuric halide which can be easily deposited and stripped from the polymer electrode surface. The procedure was optimized for mercury determination. For 120 s accumulation time, detection limit of 5 ng mL^?1 mercury(II) has been observed. The relative standard deviation is 1.3% at 40 ng mL^?1 mercury(II). The performance of the polymer film studied in this work was evaluated in the presence of surfactants and some potential interfering metal ions such as cadmium, lead, copper and nickel.     

New dinuclear nickel(II) complexes: synthesis, structure, electrochemical, and magnetic properties

The reaction of [NiBr(2)(bpy)(2)] (bpy = 2,2'-bipyridine) with organic phosphinic acids ArP(O)(OH)H [Ar = Ph, 2,4,6-trimethylphenyl (Mes), 9-anthryl (Ant)] leads to the formation of binuclear nickel(II) complexes with bridging ArP(H)O(2)(-) ligands. Crystal structures of the binuclear complexes [Ni(2)(μ-O(2)P(H)Ar)(2)(bpy)(4)]Br(2) (Ar = Ph, Mes, Ant) have been determined. In each structure, the metal ions have distorted octahedral coordination and are doubly bridged by two arylphosphinato ligands. Magnetic susceptibility measurements have shown that these complexes display strong antiferromagnetic coupling between the two nickel atoms at low temperatures, apparently similar to binuclear nickel(II) complexes with bridging carboxylato ligands. Cyclic voltammetry and in situ EPR spectroelectrochemistry show that these complexes can be electrochemically reduced and oxidized with the formation of Ni(I),Ni(0)/Ni(III) derivatives.     

Nickel(II) complexes of 21-C-alkylated inverted porphyrins: synthesis,protonation, and redox properties

Reaction of the nickel(II) complex of an inverted porphyrin, (5,10,15,20-tetraphenyl-2-aza-21-carbaporphyrinato)nickel(II) (1), with haloalkanes in the presence of proton scavengers yields 21-C-alkylated complexes. The products are separated and characterized spectroscopically. Chirality of the formed substituted metalloporphyrins is discussed on the basis of the (1)H NMR spectra. Diastereomers are observed for the complexes containing chiral substituents. Protonation of the external nitrogen of the inverted pyrrole is combined with coordination of the apical ligand that leads to paramagnetic nickel(II) complexes. Very strong differentiation of the isotropic shift for diastereotopic methylene protons is observed in (1)H NMR spectra of the protonated paramagnetic species. For the systems containing benzyl, allyl, and ethoxymethyl substituents a mild dealkylation in solution of protonated complexes is observed in the presence of oxygen. Redox properties of the alkylated complexes are studied by means of cyclic voltammetry. Oxidation of the nickel center in 21-alkylated systems takes place at the potentials comparable to that of unsubstituted complex 1. Protonation introduces small changes to the potential of the Ni(II)/Ni(III) redox couple, but it stabilizes nickel(I) species. Products of chemical oxidation and reduction of the alkylated complexes are detected by means of the EPR spectroscopy indicating in both cases metal-centered redox processes.     

Schiff碱基过渡金属镍络合物的电化学聚合:阳极电聚合中扫描速率的影响(英文)

采用线性电位扫描法制备了水杨醛-Schiff碱基过渡金属镍络合物的聚合物poly[Ni(salen)],扫描速率为5-150 mV.s-1.采用场发射显微镜观察了聚合物poly[Ni(salen)]的表面形貌.研究了电聚合中扫描速率对聚合物生长的影响,电聚合速率(dГ/dm)与扫描速率(v)呈指数衰退关系,通过库仑电量分析指出电聚合扫描速率在20mV.s-1时聚合产物中含有最多的氧化还原活性点.扫描速率提高时单体的扩散步骤限制了聚合物的生长,所以氧化还原活性点总量随着扫描速率的提高而开始下降.利用循环伏安法分析了聚合物poly[Ni(salen)]的扩散动力学,结果表明在20 mV.s-1时制备的聚合物具有较大的电荷扩散系数.     

Redox transitions of chromium, manganese, iron, cobalt and nickel protoporphyrins in aqueous solution

The electrochemical redox behavior of immobilized chromium, manganese, iron, cobalt, and nickel protoporphyrins IX has been investigated over the pH 0-14 range. In the investigated potential domain the metalloporphyrins were observed in four different oxidation states (M(I), M(II), M(III) and M(IV)). The metalloporphyrins differ in the potentials at which the redox transitions occur, but the observed pH dependence of the redox transitions was similar for the different metalloporphyrins and revealed that the M(II)/M(III) and M(III)/M(IV) transitions were accompanied by a hydroxide transfer at high pH. The fact that the metalloporphyrins are immobilized on graphite does not seem to have a large influence on their redox behavior, as can be deduced from the comparable behavior of immobilized metalloporphyrins on gold and of watersoluble metalloporphyrins in solution. We also performed density functional theory (DFT) calculations on the metalloporphyrins in different oxidation states. The geometries and spin states predicted by these calculations agree well with experimentally determined values; the calculations were also able to predict the electrochemical potentials of the [M(II)]/[M(III)-OH] redox transition to within about 300 mV.     

Donnan permselectivity in layer-by-layer self-assembled redox polyelectrolye thin films

Redox polyelectrolyte multilayers have been assembled with use of the layer-by-layer (LBL) deposition technique with cationic poly(allylamine) modified with Os(bpy)(2)ClPyCHO (PAH-Os) and anionic poly(styrene)sulfonate (PSS) or poly(vinyl)sulfonate (PVS). Different behavior has been observed in the formal redox potential of the Os(II)/Os(III) couple in the polymer film with cyclic voltammetry depending on the charge of the outermost layer and the electrolyte concentration and pH. The electrochemical quartz crystal microbalance (EQCM) has been used to monitor the exchange of ions and solvent with the external electrolyte during redox switching. At low ionic strength Donnan permselectivity of anions or cations is apparent and the nature of the ion exclusion from the film is determined by the charge of the topmost layer and solution pH. At high electrolyte concentration Donnan breakdown is observed and the osmium redox potential approaches the value for the redox couple in solution. Exchange of anions and water with the external electrolyte under permselective conditions and salt and water under Donnan breakdown have been observed upon oxidation of the film at low pH for the PAH-Os terminating layer. Moreover, at high pH values and with PVS as the terminating layer EQCM mass measurements have shown that cation release was masked by water exchange.     

Cobalt(II) Schiff Base/Large Mesoporous Carbon Composite Film Modified Electrode as Electrochemical Biosensor for Hydrogen Peroxide and Glucose

A simple method was developed to prepare a cobalt(II) Schiff base (Co(salen))/large mesoporous carbon (LMC) composite film. The structure and electrocatalytic performance of the Co(salen)/LMC film were investigated by scanning electron microscopy (SEM) and cyclic voltammetry (CV). The Co(salen)/LMC film exhibits high electrocatalytic activity toward H₂O₂, such as low detection limit (8.5×10^?7 M) and wide linear concentration range (2.0×10^?6–8.9×10^?3 M). Furthermore, glucose oxidase (GOD) was self‐assembled on the surface of the Co(salen)/LMC film modified electrode. Determination of glucose in human blood serum with satisfying result was investigated by the resulting biosensor.     

Synthesis of N-morpholine or N,N-diethyl, N′-monosubstituted benzoyl thiourea copper complexes: characterization and electrochemical investigations

A series of N-morpholine or N,N-diethyl, N′-substituted benzoyl thioureas (R = Cl, Br, OMe or NO₂ in ortho, meta or para position) have been synthesized by condensation of morpholine or diethylamine with substituted benzoyl isothiocyanates. All CuL₂ complexes have been characterized. Cyclic voltammetry has shown that the irreversible process copper(II)/copper(I) redox systems are influenced slightly by the substitution, whereas the quasi-reversible copper(III)/copper(II) redox systems are not.     

Transition metal complexes of acetamidomalondihydroxamate: synthesis,spectral, thermal and electrochemical studies

Acetamidomalondihydroxamate (K₂AcAMDH) and its manganese(II), iron(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes were synthesized and characterized by elemental analysis, UV–VIS, IR and magnetic susceptibility. The pK _a1 and pK _a2 values of the dihydroxamic acid in aqueous solution were found to be 8.0?±?0.1 and 9.7?±?0.1. The dihydroxamate anion AcAMDH behaves as a tetradentate bridging ligand through both hydroxamate groups, forming complexes with a metal to ligand ratio of 1?:?1 in the solid state. The FTIR spectra and thermal decompositions of the ligand and its metal complexes were recorded. The redox behavior of the complexes was investigated in aqueous solution by square wave voltammetry and cyclic voltammetry at neutral pH. In contrast to the solid state, in solution the copper(II) and zinc(II) ions form stable complex species with a metal to ligand ratio of 1?:?2. The iron(II) and nickel(II) complexes show a two-electron irreversible reduction behavior, while the copper(II) and zinc(II) complexes undergo reversible electrode reactions. The stability constants of the complexes were determined by square wave voltammetry.     

Concerning the Deactivation of Cobalt(III)‐Based Porphyrin and Salen Catalysts in Epoxide/CO2 Copolymerization

Functioning as active catalysts for propylene oxide (PO) and carbon dioxide copolymerization, cobalt(III)‐based salen and porphyrin complexes have drawn great attention owing to their readily modifiable nature and promising catalytic behavior, such as high selectivity for the copolymer formation and good regioselectivity with respect to the polymer microstructure. Both cobalt(III)–salen and porphyrin catalysts have been found to undergo reduction reactions to their corresponding catalytically inactive cobalt(II) species in the presence of propylene oxide, as evidenced by UV/Vis and NMR spectroscopies and X‐ray crystallography (for cobalt(II)–salen). Further investigations on a TPPCoCl (TPP=tetraphenylporphyrin) and NaOMe system reveal that such a catalyst reduction is attributed to the presence of alkoxide anions. Kinetic studies of the redox reaction of TPPCoCl with NaOMe suggests a pseudo‐first order in cobalt(III)–porphyrin. The addition of a co‐catalyst, namely bis(triphenylphosphine)iminium chloride (PPNCl), into the reaction system of cobalt(III)–salen/porphyrin and PO shows no direct stabilizing effect. However, the results of PO/CO₂ copolymerization by cobalt(III)–salen/porphyrin with PPNCl suggest a suppressed catalyst reduction. This phenomenon is explained by a rapid transformation of the alkoxide into the carbonate chain end in the course of the polymer formation, greatly shortening the lifetime of the autoreducible PO‐ring‐opening intermediates, cobalt(III)–salen/porphyrin alkoxides.     

ELECTROCHEMISTRY OF NICKEL(II) TRYPTOPHAN FILM ELECTRODE AND ELECTROCATALYTIC OXIDATION OF METHANOL

A polymer film of tryptophan was obtained at a glassy carbon electrode (GC) by cyclic voltammetry. The cyclic voltammograms of the polymer film electrode(poly-Try GC) exhibited two redox waves. After incorporation of Ni(II), the electrode (poly-Ni(II) Try/GC) was greatly improved in catalytic activity. The potential 0.65 V of methanol oxidation at the poly-Ni(II)Try/GC is much more negative than the potential at the poly-Try/GC and at the bare glassy carbon (GC) electrode in 0.01 mol/L NaOH.     

New Copper（Ⅱ） and Nickel（Ⅱ） Complexes of 4-Morpholinoacetophenone Thiosemicarbazone： Structural, Electrochemical and Antimicrobial Studies

4-Morpholinoacetophenone thiosemicarbazone, MAPT, and its nickel（Ⅱ） and copper（Ⅱ） complexes have been prepared and characterized by elemental analysis, magnetic susceptibility, spectral methods （FT-IR, ^1H NMR） and cyclic voltammetry. Electrochemical behaviors of the complexes have been studied by cyclic voltammetry in DMF media showing metal centered reduction processes for both of them. The redox properties, nature of the electrode processes and the stability of the complexes were discussed. [Cu（MAPT）2]Cl2 complex shows Cu（Ⅱ）/Cu（Ⅰ） couple and quasi-reversible wave associated with the Cu（Ⅲ）/Cu（Ⅱ） process. The reduction/oxidation potential values depend on the structures of complexes. Also, the antimicrobial activities of these complexes were determined against S. aureus, E. coli and B. subtilis.     

Synthesis,characterization, and electrochemical studies of Co(II,III) dithiocarbamate complexes

Cobalt(II) complexes of N-methyl phenyl, 1-phenylpiperazyl, and morpholinyl dithiocarbamates have been synthesized and characterized by UV–Visible, FTIR, ¹H-, ¹³C-NMR, and mass spectrometry. The spectroscopic data indicated that two ligands coordinated in bidentate chelating to the metal ion to form four-coordinate cobalt(II) complexes (1–3), which was confirmed by mass analysis (TOF MS ES⁺) of the complexes with m/z [M]⁺ = 450.98, 382.94, and 382.94 for 1, 2, and 3, respectively. Single crystal analysis of 2A and 3A show centrosymmetric mononuclear cobalt(III) bonded to three dithiocarbamate ligands forming a distorted octahedral geometry, indicating the cobalt(II) undergoes aerial oxidation to cobalt(III) during recrystallization. In addition, 2A crystallized with one solvated molecule of toluene. The redox behaviors of the complexes were studied by cyclic and square wave voltammetry in dichloromethane; the result revealed a metal centered redox process consisting of a one-electron quasi-reversible process assigned to Co(III)/Co(IV) oxidation and a corresponding Co(IV)/Co(III) reduction. Randles–Sevcik plots (anodic peak current versus the square root of the scan rate (I_p,a versus ν^1/2)) for the redox couples revealed diffusion-controlled behavior.     

Synthesis and Characterization of a New Series of Nickel(II) meso-Tetrakis (polyfluorophenyl)porphyrins Functionalized by Pyrrole Groups and Their Electropolymerized Films

A new series of nickel(II) meso-tetrakis(polyfluorophenyl)porphyrins functionalized by pyrrole groups have been synthesized. Each new complex was isolated and characterized by (1)H NMR, (19)F NMR, IR, UV-visible spectroscopy, and mass spectrometry as well as electrochemistry. This is the first example of polyfluorinated substituted porphyrins where the four possible compounds have been obtained by functionalization of the para-fluorine substituents of the nickel(II) meso-tetrakis(pentafluorophenyl)porphyrin. This functionalization has allowed the preparation for the first time of polyfluorinated metalloporphyrin films by oxidative electropolymerization. Electrochemical stability studies of these polymeric films have shown better stability for films derived from the monomer having four pyrrole groups because of their high degree of cross-linking degree. A large difference of electroactive solute permeation has been found in the polymeric films which have been obtained by electropolymerization of monomers for which one pyrrole group has been substituted compared to those for which four pyrrole groups have been substituted. This could be related to quite rigid polymer structures for tetrasubstituted polymer films and molecular sieving properties of monosubstituted polymer films. The spectroelectrochemistry of a polymeric film on an OTE has established that the two-electron-oxidized species are stable in the film; likewise the singly and doubly electroreduced species are stable and are more likely ligand-centered.