Potentiometric behaviour of the copper electrode in aqueous copper(II) perchlorate solutions containing sodium chloride

It is demonstrated that the copper metal electrode corrodes in the presence of copper(II) ions in solution. A model based on mass balance can properly describe the experimental results. In the presence of copper(II) ions the copper electrode responds to copper(I), indicating that the electrode potential corresponds to a mixed potential.     

The use of Nafion-coated thin mercury film electrodes for the determination of the dissolved copper speciation in estuarine water

Differential pulse anodic stripping voltammetry (DPASV) using a Nafion-coated thin mercury film electrode (NCTMFE) was implemented to determine the dissolved copper speciation in saline estuarine waters containing high concentrations of dissolved organic matter (DOM). The study used model ligands and estuarine water from San Francisco Bay, California, USA to demonstrate that the NCTMFE is more effective at distinguishing between electrochemically inert and labile copper species when compared to the conventional thin mercury film electrode (TMFE). Copper titration results verify that the NCTMFE better deals with high concentrations of DOM by creating a size-exclusion barrier that prevents DOM from interacting with the mercury electrode when performing copper speciation measurements. Pseudovoltammograms were used to illustrate that copper complexes found in natural waters were more apt to be electrochemically inert at the NCTMFE relative to the TMFE when subjected to high negative overpotentials. Copper speciation results using the NCTMFE from samples collected in San Francisco Bay estimated that >99.9% of all copper was bound to strong copper-binding ligands. These L₁-class ligands exceeded the concentration of total dissolved copper in all samples tested and control the equilibrium of ambient [Cu²⁺] in the San Francisco Bay estuary.     

A tetranuclear copper(II) complex: crystal structure,assembly, EPR,electrochemistry and magnetism

A tetranuclear copper(II) complex, [Cu₂L]₂(ClO₄)₂ · 4H₂O (1), where H₃L = N,N′-bis(4-(3′-formyl-5′-chlorosalicyclidene)iminoethyl)-4-chloro-2,6-bimethyliminophenol, has been synthesized and structurally characterized by ES-MS, IR and X-ray crystallography. The complex is a dimer of two dinuclear copper(II) acylic enantiomorph subunits ([Cu₂L]ClO₄ · 2H₂O), held together by π–π, coordination and hydrogen bond interactions. The Cu–Cu separation in each subunit, bridged by one phenoxide, is 3.228 Å, and the shortest distance of Cu–Cu between the two subunits is 3.252 Å. There are two crystallographically unique copper(II) environments, one (Cu1) is square-based pyramidal with O₃N₂ donor set, another (Cu2) square planar with O₂N₂ donor set. The cyclic voltammogram of the complex shows that it undergoes two stepwise reduction processes, E _pc = ?0.707 and ?0.850 V, respectively. Magnetic measurements in the 2–300 K range indicate strong antiferromagnetic interactions between Cu(II) ions in each subunit with the exchange constant J = ?211(2) cm^?1. The observation has been rationalized on the basis of the effective magnetic pathway.     

Study of photoelectrochemical corrosion of lead oxide in alkaline solution by the rotating ring-disk electrode technique

Photoelectrochemical corrosion of n-type α-PbO electrodes in aqueous Fe(CN)₆ ^3−/4− and I⁻/I₃ ⁻ electrolytes using the rotating ring-disk electrode technique has been investigated. The α-PbO thin film is found to be more stable in I⁻/I₃ ⁻ (48%) than in Fe(CN)₆ ^3−/4− electrolyte (10%). Preferential adsorption of iodide ions decreases the photocorrosion reaction of holes with α-PbO. Addition of CsI (0.4 mM) to the I⁻/I₃ ⁻ electrolyte decreases the photocorrosion from 48% to less than 10%. Cs⁺ ions perhaps nullify the effect of negatively charged surface states of α-PbO, thus minimizing the trapping of holes at the surface of α-PbO and hence decrease the possibility of photocorrosion of lead oxide with holes. Received: 30 June 1998 / Accepted: 20 April 1999     

Synthesis,crystal structure and antimicrobial properties of a copper(II) complex of an unsymmetrical tripodal ligand

A new copper(II) complex of an unsymmetrical tripodal ligand (NN₂O222) derived from tris(2-aminoethylamine)amine (tren) by substitution of one aminoethyl group by an hydroxyethyl group has been synthesized and characterized by X-ray crystallographic methods as [(NN₂O222)Cu(ImH)](ClO₄)₂·0.5H₂O (NN₂O222?=?2-[bis(2-aminoethyl)amino]ethanol; ImH?=?imidazole). Crystals of the complex are orthorhombic, space group Pna2₁, with a?=?29.983(10), b?=?15.568(5), c?=?8.127(3)?Å. Two similar monometallic cations exist in the asymmetric unit and in each case the Cu(II) ion is five-coordinate with tetragonally distorted trigonal bipyramidal geometry. Variable-temperature magnetic measurements show that there is very weak antiferromagnetic interaction between the metal ions. Cyclic voltammetry indicates quasi-reversible Cu^II/Cu^I redox behavior at +44?mV vs SCE. An antimicrobial activity study found that the complex is active against Candida albican, Staphylococcus aureus, Bacillus pumilus, Klebosiella pneumoniae and Escherichia coli, but to no greater extent than Cu(ClO₄)₂·6H₂O.     

旋转铂盘电极上Cu(phen)_2~(2 )与6-巯基嘌呤的相互作用

在Tris-NaC1*(pH=7.2)缓冲溶液中,应用循环伏安法,微分脉冲伏安法、旋转圆盘电极实验、交流阻抗法及其数据模拟等技术研究了Cu(phen)2 25(phcn=1.10-邻菲咯啉)与6-巯基嘌呤(6-MP)的相互作用.结果显示.Cu(phen)2 2MP与6-MP无论在扩散控制过程或电化学控制过程都发生了相互作用.Cu(phen)2 2及其与6-MP的作用产物于铂电极上均呈现一对氧化还原峰,但后者呈现的氧化还原峰负移.峰电流减小.交流阻抗结果显示,无论6-MP存在与否,Cu(phen)2 2在交流阻抗谱上均呈现两个清晰的电容弧,但当6-MP存在时,电化学反应电阻和电化学吸脱附电阻均增大.Cu(phen)2 2在不同转速下的阻抗拟合结果显示.随转速增大.电化学反应电阻和电化学吸脱附电阻均减小.双电层电容呈增大趋势,而吸脱附电容呈减小趋势:当6-MP存在时.仍然呈现此变化规律.     

The Mediation Effect of a Polyaniline-Coated Electrode on the Reduction of Iron (III) Ions

The mediation effect of polyaniline-coated platinum electrodes on the reduction of iron(III) ions was studied by the cyclic voltammetry and rotating disk electrode methods. The rate constants of the cross reaction between iron(III) ions and polyaniline (PA) were found to depend upon the amount of PA coated on the electrode. On the basis of the rate constants the PA-coated electrode mediates the reduction of iron(III) ion efficiently and behaves as well as a metallic electrode.     

Electrochemical Study of Tryptophan‐containing Peptides‐Cu(II) Complexes

This article presents rotating ring‐disc electrode investigations of (A = alanine, F = phenylalanine, G = glycine, L = leucine, W = tryptophan) W, GW, WGG, GWG, GGW, GWGG, and GGWA. In addition, the analyses of the copper complexes of the same peptides plus GF, FGG, GFG, FGG, GGFL, GGGG, AAAA, and GGGGGG have been carried out. The results suggest that an influential step in the reaction mechanism of the copper complexes of the tryptophan‐containing peptides (W‐peptides) is the alteration of the peptide structure after the one‐electron oxidation of tryptophan. This change in structure leads to a positive shift in redox potential for the Cu(III)/Cu(II) couple. The analytical implications for the electrochemical detection of W‐peptides as their copper complexes are applied for detection of W‐containing bioactive peptides. Application of the optimized detection conditions of peptides as their Cu(II) complexes are as follows: (1) If sensitivity is paramount, detect the copper complexes at a relatively high potential, around 0.7 V vs. Ag/AgCl. (2) If selectivity is paramount, use a dual electrode detector, oxidize at an upstream anode at 0.4 V, and detect at the downstream cathode at 0–0.1 V.     

Voltammetric study on the complex of thiram-copper(II) and its application

Based on the formation of tetramethylthiuram disulfide (thiram)-copper(II) complex by square-wave voltammetry on a glassy carbon electrode, a new method is proposed for determination of thiram. There is a good linear relationship between peak current and concentration of thiram in the range of  mol l⁻¹ (r=0.999). The method is applied to the determination of thiram residue in plant with satisfactory results, compared with results achieved by using HPLC. Two oxidation peaks and two reduction peaks are obtained by cyclic voltammetry on a glassy carbon electrode in 0.2 mol l⁻¹ HAc-NaAc (pH 4.0) solution containing thiram-copper(II) complex. The electrode reaction process is quasi-reversible with adsorptive characteristics. The mechanism of electrode reaction is discussed.     

旋转铂盘电极上Cu(phen)22+与6-巯基嘌呤的相互作用

在 Tris-NaCl(pH=7.2)缓冲溶液中,应用循环伏安法、微分脉冲伏安法、 旋转圆盘电极实验、交流阻抗法及其数据模拟等技术研究了Cu(phen)22+（phen=1,10-邻菲咯啉）与6-巯基嘌呤（6-MP）的相互作用.结果显示, Cu(phen)22+与6-MP无论在扩散控制过程或电化学控制过程都发生了相互作用. Cu(phen)22+及其与6-MP的作用产物于铂电极上均呈现一对氧化还原峰,但后者呈现的氧化还原峰负移,峰电流减小，交流阻抗结果显示,无论6-MP存在与否, Cu(phen)22+在交流阻抗谱上均呈现两个清晰的电容弧,但当6-MP存在时,电化学反应电阻和电化学吸脱附电阻均增大. Cu(phen)22+在不同转速下的阻抗拟合结果显示,随转速增大,电化学反应电阻和电化学吸脱附电阻均减小,双电层电容呈增大趋势,而吸脱附电容呈减小趋势;当6-MP存在时,仍然呈现此变化规律.     

Redox equilibria in the In(III)-In(I)-In system in aqueous KBr solutions II. A rotating ring-disc electrode study

Summary The open-circuit behaviour of thick indium films formed onto gold by the electroreduction of In(III) has been investigated in acidified aqueous KBr solutions using the rotating ring-disc electrode technique. The spontaneous dissolution of indium metal immersed in the solution containing its own ions of higher valency yields In(I) ions. Information about the equilibrium and mechanism of the process studied was drawn from measurements of the limiting ring current and disc potential as a function of the electrode rotation rate. It was proved that the overall reaction 2In+In(III)3In(I) occurs as a coupling of two electrochemical steps: InIn(I)+e^–, and In(III)+2e^–In(I). The cathodic half-reaction is the rate-determining step, whereas the anodic half-reaction is reversible.

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Das Redox-Gleichgewicht im In(III)-In(I)-In-System in wäßrigen KBr-Lösungen, 2. Mitt. Untersuchungen mit der rotierenden Ring-Scheiben-Elektrode

Zusammenfassung Die spontane Auflösung von Indium unter der Wirkung von eigenen lonen (In(III)) wurde in sauren bromidhaltigen Lösungen mit Hilfe der rotierenden Ring-Scheiben-Elektrode untersucht. Die Angaben über das Gleichgewicht und den Mechanismus des untersuchten Prozesses wurden auf Grund der Abhängigkeit der Grenzströme an der Ring-Elektrode und der Elektrodepotentiale der Scheiben-Elektrode von der Umdrehungsgeschwindigkeit erreicht. Aus den Messungen folgt, daß die Bruttoreaktion 2In+In(III)3In(I) aus zwei überlagerten Durchtrittsreaktionen, InIn(I)+e^– und In(III)+2e^–In(I), besteht. Die kathodische Reaktion ist geschwindigkeitsbestimmend, während die anodische Teilreaktion reversibel abläuft.

     

Response of the jalpaite membrane copper(II) ion-selective electrode in marine waters

The response of the Orion 94-29 Cu^II ion-selective electrode (ISE) [employing a jalpaite membrane] in seawater has been related to levels of free Cu^II yielding results for the Derwent River and San Diego Bay that are 2 to 3 orders of magnitude higher than those for the Pacific Ocean. Response data for the electrode in acidified seawater at pH 2 are internally consistent with total Cu^II levels determined using differential pulse anodic stripping voltammetry (DPASV) and graphite furnace atomic absorption spectrometry (GFAAS). It has been found that, even in acidified seawater, the organic ligands influence the response of the electrode, and this effect can be compensated successfully by either analyzing UV-photooxidized seawater and/or using a standard addition technique. The assigned ISE results for total Cu^II in acidified seawater fall within ± (0.1–0.5) pCu unit of values determined using GFAAS. Electrode drift in seawater can be minimized by using a polished electrode that has been conditioned in seawater for 24 h. The improved response rate of a conditioned ISE minimizes electrode soaking times and sample contamination through membrane corrosion.     

Thiocyanate-selective electrode based on N-salicylidene-benzylamineato copper(II) complex

Highly selective poly(vinyl chloride) (PVC) membrane electrode based on N-salicylidene-benzylamineato copper(II) complexes [Cu(SBA)₂] as new carriers towards thiocyanate-selective electrode was reported. The influence of membrane composition, pH and possible interfering anions were investigated on the response properties of the electrode. The resulting electrode exhibits anti-Hofmeister selectivity sequence: SCN⁻ > ClO₄⁻ > Sal⁻ > I⁻ > Br⁻ > NO₃⁻ > NO₂⁻ > SO₃²⁻ > H₂PO₄⁻ > Cl⁻ > SO₄²⁻, and a near-Nernstian potential linear range for thiocyanate from 1.0 × 10⁻¹ to 9.0 × 10⁻⁷ M with a detection limit of 7.0 10⁻⁷ M and a slope of , over a wide pH range of 3.0–9.0 in phosphate buffer solution at 20°C. The proposed electrode has a fast response time of about 5–10 s and can be used for at least 3 months without any considerable divergence in potential. The electrode was successfully applied to the determination of thiocyanate in waste water and human urine and saliva samples. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 3, pp. 293–299. The text was submitted by the authors in English.     

The solid state electrochemistry of samarium (III) hexacyanoferrate (II)

A new electroactive polynuclear inorganic compound of a rare earth metal hexacyanoferrate, samarium hexacyanoferrate (SmHCF), was prepared chemically and characterized using techniques of FTIR spectroscopy, thermogravimetric analysis (TGA), X-ray powder diffraction, UV–Vis spectrometry and X-ray photoelectron spectroscopy (XPS) etc. The cyclic voltammetric behavior of SmHCF mechanically attached to the surface of graphite electrode was well defined and exhibited a pair of redox peaks with the formal potential of 180.5 mV (versus SCE) at a scan rate of 100 mV/s in 0.2-M NaCl solution and the redox peak currents increased linearly with the square root of the scan rates up to as high as 1,000 mV/s. The effects of the concentration of supporting electrolyte on the electrochemical characteristics of SmHCF and the transport behavior of K⁺, Na⁺ and Li⁺ counter-ions through the ion channel of SmHCF were studied by voltammetry.     

Biodegradation of soluble redox polymers. Part 2: (0.017ferrocene)amylose at a rotating disk electrode

The behavior of (ferrocene)amylose (FA), in the presence of amylolytic depolymerases (α-amylase from Aspergillus oryzae and human saliva), has been investigated by cyclic voltammetry at a rotating disk electrode (CVA/RDE). Growth of the limiting current with time in the presence of the enzymes is proportional to the amount of enzyme introduced. The quantitative data treatment to assay the endoamylolytic activity of enzymes at CVA/RDE involves plotting (i_dt/i_d0)^4.5 against time; the slope of the linear plot being equal to (rate) M_n0C⁻¹, where i_dt and i_d0 are the limiting currents at time t and 0, respectively, (rate) is the enzymatic activity, M_n0 is the number averaged molecular weight of FA at t = 0, and c is its concentration. The comparison of CVA/RDE with the 3,5-dinitrosalicylic acid and the Somogyi–Nelson reducing saccharides procedures shows advantages of the former, especially in assaying small quantities of enzymes. Also the CVA/RDE approach is simpler and takes place under much milder conditions. The main disadvantage of CVA/RDE is the inhibiting effect of Triton X-100 in the reaction between FA and the amylases which is not observed in the case of native, ferrocene-free amylose. In general, CVA/RDE appears to be an attractive analytical method for monitoring diverse enzymatic depolymerization reactions.     

Investigation of Copper(II) Interference on the Anodic Stripping Voltammetry of Lead(II) and Cadmium(II) at Bismuth Film Electrode

The bismuth‐coated electrode is known to be prone to errors caused by copper(II). This study investigates copper(II) interference at bismuth film electrode for the detection of lead(II) and cadmium(II). It was conducted using glassy carbon electrode, while the bismuth film was plated in situ simultaneously with the target metal ions at ? 1200 mV. Copper(II) presented in solution significantly reduced the sensitivity of the electrode, for example there was an approximately 70 % and 90 % decrease in peak signals for lead(II) and cadmium(II), respectively, at a 10‐fold molar excess of copper(II). The decrease in sensitivity was ascribed to the competition between copper and bismuth or the metal ions for surface active sites. Scanning electron microscopy (SEM) and energy dispersive X‐ray (EDX) analysis suggested a large decrease in the amount of bismuth nanoparticles formed on the electrode surface in the presence of copper(II) occurred, validating the competition between copper and bismuth ions for surface active sites. Recovery of the stripping signal of lead(II) and cadmium(II) was obtained by adding ferrocyanide ion to the solution. Finally, the proposed method was successfully applied to determine lead(II) and cadmium(II) in water samples and the method was validated by ICP‐MS technique.     

Self-assembly and crystal structure of a three-dimensional copper(II) complex

A copper(II) complex of a sulfonate derivative of chrysin, 5,7-bihydroxyflavone-6-sulfonate, Cu(C₁₅H₈O₇S)(3H₂O), has been prepared. The complex was characterized by elemental analysis, spectroscopic measurements and single-crystal X-ray diffraction studies. It crystallizes in the monoclinic space group C2/c, with a?=?16.036(18), b?=?6.944(8), c?=?28.03(3)?Å, β?=?94.463(17)°, V?=?3112(6)?ų, Z?=?8. In the complex, Cu(II) is five-coordinate and all donors are oxygen atoms. Hydrogen bonds and π–π stacking interactions in the crystal lead to the formation of a three-dimensional supramolecular motif.     

Synthesis and crystal structure of a copper(II) complex of the tridentate ligand di-(2-benzimidazolylmethyl)imine

A copper complex [Cu(IDB)Cl] · 0.5[CuCl₄]?·?H₂O (1) (IDB?=?di(2-benzimidazolylmethyl)imine) was synthesized and its structure was determined by X-ray single crystal diffraction. In this complex, the central copper(II) ion is four-coordinate, IDB serves as a neutral tridentate chelating ligand for the tetragonal copper ion. The cyclic voltammogram of complex 1 in CH₃CN gave two reversible redox waves (E _1/2,1?=??0.14?V and E _1/2,2?=?0.08?V versus SCE) which correspond to the Cu(II,?II)/Cu(I,?II) and Cu(II,?II)/Cu(II,?I) redox processes, respectively.     

Synthesis of unsymmetrical compartmental oxime nickel(II) and copper(II) complexes: spectral, electrochemical and magnetic studies

A new series of binuclear unsymmetrical compartmental oxime complexes (1–5) [M₂L] [M=Cu(II), Ni(II)] have been synthesized using mononuclear complex [ML] (L=1,4-bis[2-hydroxy-3-(formyl)-5-methylbenzyl]piperazine), hydroxylamine hydrochloride and triethylamine. In this system there are two different compartments, one has piperazinyl nitrogens and phenolic oxygens and the other compartment has two oxime nitrogens and phenolic oxygens as coordinating sites. The complexes were characterized by elemental and spectral analysis. Electrochemical studies of the complexes show two step single electron quasi-reversible redox processes at cathodic potential region. For copper complexes E¹ _pc=−0.18 to −0.62 and E² _pc=−1.18 to −1.25 V, for nickel complexes E¹ _pc=−0.40 to −0.63 and E² _pc=−1.08 to −1.10 V and reduction potentials are sensitive towards the chemical environment around the copper and nickel atoms. The nickel(II) complexes undergo two electrons oxidation. The first one electron oxidation is observed around +0.75 V and the second around +1.13 V. ESR Spectra of the binuclear copper(II) complexes [Cu₂L](ClO₄), [Cu₂L(Cl)], [Cu₂L(NO₃)] shows a broad signal at g=2.1 indicating the presence of coupling between the two copper centers. Copper(II) complexes show a magnetic moment value of μ_eff around 1.59 B.M at 298 K and variable temperature magnetic measurements show a −2J value of 172 cm⁻¹ indicating presence of antiferromagnetic exchange interaction between copper(II) centres.