Highly thiocyanate-selective membrane electrodes based on the N,N′-bis-(benzaldehyde)-glycine copper(II) complex as a neutral carrier

Some novel PVC membrane electrodes based on N,N′-bis-(benzaldehyde)-glycine metallic complexes of Cu(II), Ni(II), Zn(II) and Co(II) as neutral carriers are described. The results showed that the electrode based on the N,N′-bis-(benzaldehyde)-glycine copper(II) complex [Cu(II)-BBAG] had a near-Nernstian response to the thiocyanate ion ranging from 1.0×10⁻¹ to 9.0×10⁻⁷ M in a phosphate buffer solution of pH 4.0 with a detection limit of 7.0×10⁻⁷ M and a slope of −57.6 mV/decade at 25°C. The electrode displays an anti-Hofmeister selectivity sequence in the following order: SCN⁻>ClO⁻₄>Sal⁻>I⁻>Br⁻>NO⁻₂>NO⁻₃>SO²⁻₃>SO²⁻₄>Cl⁻>H₂PO The response mechanism is discussed in view of both AC impedance and UV spectroscopy techniques. The [Cu(II)-BBAG]-based electrode was successfully applied to the determination of the thiocyanate ion in wastewater and human saliva.     

Preparation and characterization of thiocyanate-selective electrodes based on new complexes of copper(II) as neutral carriers

The complexes of hydroxycitronellal (o-aminobenzoic acid) copper(II) (Cu(II)-HXAB) and salicylaldehyde (o-aminobenzoic acid) copper(II) (Cu(II)-SHAB) were used as neutral carriers in PVC-based membrane ion-selective electrodes. The electrode based on Cu(II)-HXAB exhibited near-Nernstian potential response to thiocyanate (SCN⁻) in a linear range of 1.0 × 10^− 6 to 1.0 × 10^− 1 M with a detection limit of 8.5 × 10^− 7 M and a slope of − 57.3 mV/decade in 0.01 M phosphate buffer solution (pH 5.0). The electrode exhibited high selectivity to SCN⁻ over other tested anions with an anti-Hofmeister selectivity sequence. The selectivity behavior might be discussed in terms of UV-Vis spectrum and infrared spectrum. The transfer process of thiocyanate across the membrane interface was investigated by making use of the AC impedance technique. The electrode containing Cu(II)-HXAB could be applied to thiocyanate analysis in waste water with satisfactory results.     

Novel all-solid-state copper(II) microelectrode based on a dithiomacrocycle as a neutral carrier

A novel dithiomacrocycle (4-phenyl-11-decanoyl-1,7-dithia-11-azacyclotetradecane-4-sulfide) has been synthesized and used as a new ionophore in order to develop a plasticized poly(vinyl chloride) membrane for copper ion detection. The performance of these novel planar copper(II)-selective potentiometric microelectrodes was investigated using potentiometric measurements. The developed microelectrodes exhibits a good linear response of 29.5 ± 1 mV per decade within the concentration range of 1.0 × 10⁻⁶ to 1.0 × 10⁻² M (r = 0.9995) of Cu²⁺. The detection limit was determined as 5.62 × 10⁻⁷ M and the selectivity coefficients for possible interfering cations were evaluated. The microelectrodes are suitable for use with aqueous solutions of pH 3.5-6.0 and were found to be insensitive to the nature of the anions used in the sample.     

Synthesis and structures of dinuclear copper(II) complex and μ-phenolatotetrazinc(II) complex with 1,3-diphenyl-4-(salicylidene hydrazone)-phenylethylene-pyrazolone-5

Novel dinuclear copper(II) complex and phenoxy-bridged tetranuclear zinc(II) complex with 1,3-diphenyl-4-(salicylidene hydrazone)-phenylethylene-pyrazolone-5 (DPPeP-SAH) have been synthesized and characterized by X-ray crystallography. The X-ray diffraction analyses of the complexes show that two Cu(II) centers are bonded with two tetradentated ligands and the geometries around the central ions are slightly distorted square planar, while in zinc(II) complex central metal ions are held together by four μ-phenoxo bridges that lead to the formation of the tetra-μ-phenolatotetrazinc(II) centers.     

Kinetics of electroless copper deposition using cobalt(II)-ethylenediamine complex compounds as reducing agents

Electroless copper deposition using Co(II)-ethylenediamine (En) complexes as reducing agents was investigated in 0.4–1.2 M En solutions at 50 and 70 °C. There is a complicated dependence of the process rate on pH, En concentration and temperature. A copper deposition rate up to 6 m h^–1 (50–70 °C) in relatively stable solutions (pH 6) can be achieved. The stoichiometry of the Cu(II) reduction at pH 6–7 corresponds to the reaction:

Formation of an unusual copper(II) complex from the degradation of a novel tricopper(II) carbohydrazone complex

An unusual copper(II) complex [Cu(L^1a)₂Cl₂] CH₃OH·H₂O·H₃O⁺Cl⁻ (1a) was isolated from a solution of a novel tricopper(II) complex [Cu₃(HL¹)Cl₂]Cl₃·2H₂O (1) in methanol, where L^1a is 3-(2-pyridyl)triazolo[1,5-a]-pyridine, and characterized with single crystal X-ray diffraction study. The tricopper(II) complex of potential ligand 1,5-bis(di-2-pyridyl ketone) carbohydrazone (H₂L¹) was synthesized and physico-chemically characterized, while the formation of the complex 1a was followed by time-dependant monitoring of the UV–visible spectra, which reveals degradation of ligand backbone as intensity loss of bands corresponding to O → Cu(II) charge transfer.     

Electrocatalytic oxidation of hydrazine at a Co(II) complex multi-wall carbon nanotube modified carbon paste electrode

The catalytic oxidation of hydrazine was investigated by a cobalt(II) bis (benzoylacetone) ethylenediimino multi wall carbon nanotube-modified carbon paste electrode (Co(II)BBAEDI-MWCNT-MCPE) as a highly sensitive electrochemical sensor. The effect of variables such as pH and modifier percent on cyclic voltammograms peak current was optimized. The modified electrode showed very efficient electrocatalytic activity for anodic oxidation of hydrazine in 0.1 M phosphate buffer solution (pH 7.0). Anodic peak potential of hydrazine oxidation at the surface of modified electrode shifts by about 500 mV toward negative values compared with that on the bare electrode. The diffusion coefficient and electron transfer coefficient of hydrazine were obtained using electrochemical approaches. The Co(II)BBAEDI-MWCNT-MCPE showed good reproducibility (RSD < 3.3%). The electrocatalytic current increased linearly with the hydrazine concentration in the range of 0.3–70.0 μM and detection limit was 0.1 μM. The effect of various interferences on the hydrazine peak current was studied. This method was applied to determine hydrazine in water samples.     

水杨醛缩牛磺酸合铜配合物催化过氧化氢分解

用水杨醛与牛磺酸以1∶1的比例在无水乙醇中反应,合成了水杨醛缩牛磺酸席夫碱。再与Cu(Ⅱ)金属离子络合,合成了Sch iff碱铜配合物,红外光谱证实了其结构。研究了不同条件下该配合物对H2O2分解的催化性能。结果表明,该配合物能迅速催化过氧化氢的分解,在20℃、pH=11、0.05 g配合物的条件下,5%过氧化氢在20 s内分解放出32 mL氧气。催化反应速度还与配合物用量、过氧化氢浓度和溶液pH值等因素有关。     

Electrocatalytic addition reaction of bromide compounds and activated olefins on nickel(II) tetraazamacrocyclic complex-modified graphite felt electrode

Electrocatalytic addition reaction of bromide compounds and activated olefins was studied using a nickel(II) tetraazamacrocyclic complex-modified graphite felt (GF) electrode. The modified GF electrode was observed a catalytic current in the presence of bromide compound by cyclic voltammetry. A preparative electrocatalytic addition reaction of bromide compounds and activated olefins was successfully achieved on the modified GF electrode with an adequate yield (24-82%) and turnover number of the nickel catalyst (983-1533).     

Theoretical and practical investigations of copper ion selective electrode with polymeric membrane based on N,N′-(2,2-dimethylpropane-1,3-diyl)-bis(dihydroxyacetophenone)

A novel ion-selective poly(vinyl chloride) (PVC) membrane sensor for Cu²⁺ ions based on N,N′-(2,2-dimethylpropane-1,3-diyl)-bis(dihydroxyacetophenone) (NDHA) as a new ionophore was prepared and studied. The best performance was observed for the membrane composition, including 30:65:1:4 (wt%) = PVC:DBP:KTpClPB:NDHA. The electrode showed a good Nernstian slope of 30.0 ± 0.5 mV/decade in a wide linear range activity of 3.0 × 10⁻⁷ to 1.0 × 10⁻² mol dm⁻³ Cu(NO₃)₂ with limit of detection 2.5 × 10⁻⁷. Sensor exhibited a fast response time (t_95% < 10 s) and could be used for about 4 months in the pH range of 3.0–7.4. The proposed potentiometric sensor was found to work satisfactorily in partially non-aqueous media up to 30 (vol%) content of methanol, ethanol and acetone. Applications of this electrode for the determination of copper in real samples, and as an indicator electrode for potentiometric titration of Cu²⁺ ion using EDTA, were reported. In order to predict the extraction ability of NDHA for different metallic ions, the complexes [M(NDHA)] and [M(H₂O)₆] (where M = Cu²⁺, Co²⁺, Hg²⁺, Pb²⁺, Ag⁺, Mg²⁺, Ca²⁺, Mn²⁺, Zn²⁺, Cd²⁺, K⁺ and Al³⁺) were investigated using ab initio theoretical calculations. The metal binding capability was evaluated using the binding energy. Results of our study could be useful for prediction of the extraction power of this Schiff base and could play a guiding role in planning experiments.     

Mechanistic study of active transport of copper (II) using LIX 54 across a liquid membrane

The present work describes the mechanism of active transport of copper(II) through an immobilized liquid membrane (ILM) containing LIX 54 (β‐diketone) dissolved in Iberfluid as mobile carrier. An uphill transport model has been described and equations have been derived taking into account aqueous boundary layer diffusion and liquid membrane diffusion as simultaneous controlling factors. In the present model, various cases were discussed using the carrier LIX 54 and different chemical species; the diffusional membrane resistance for lower and higher concentrations of extractant was evaluated. The diffusion coefficients were observed to decrease with increase in ­the extractant concentration, ranging from 4.1 × 10⁻³ to 1.65 × 10⁻² mol dm⁻³ Plotting [Cu]₀−[Cu]_t vs time resulted in a slope of [HR]₀A/2Δ_orgV taking into account the complex species, CuR₂, in the membrane. The mass transfer coefficient (Δ_org ⁻¹), the diffusion coefficient of the metal carrier species (D_org) and the thickness of the aqueous boundary layer were calculated from the proposed model for LIX 54. More than 90% of the Cu(II) could be separated using LIX 54 in the presence of various metals such as Ni, Co(II) and Zn. © 2000 Society of Chemical Industry     

Electrogenerated chemiluminescence of ruthenium (II) bipyridyl complex directly immobilized on glassy carbon electrodes

Ru(bpy)₃Cl₂ was used to modify the glass carbon electrodes (GCE) by oxidation and co-deposition on the electrode surface. The modified electrodes were characterized by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). About 2.2 × 10⁻⁹ mol Ru(bpy)₃ ²⁺ was immobilized on the GCE surface (ϕ = 4 mm). The modified GC electrodes showed stable electrochemiluminescence with tripropylamine (TPrA) as the co-reactant with a linear range from 10 to 500 μM (R ² = 0.999). Among the 10 amino acids tested, the modified electrode system showed selective response to arginine and lysine, indicating that the molecular structure played an important role as co-reactant. This simple and sensitive electrode modifying method when combined with flow-injection or liquid chromatography systems has the potential for amino acid analyses.     

Fabrication of a novel holmium(III) PVC membrane sensor based on 4-chloro-1,2-bis(2-pyridinecarboxamido)benzene as a neutral ionophore

This paper introduces the development of an original PVC membrane electrode, based on 4-chloro-1,2-bis(2-pyridinecarboxamido)benzene (CBPB) as a suitable carrier for the Ho³⁺ ion. The electrode presents a Nernstian slope of 19.7 ± 0.3 mV per decade for the Ho³⁺ ions across a broad working concentration range from 1.0 × 10⁻⁶ to 1.0 × 10⁻² M. The lower detection limit was 8.5 × 10⁻⁷ M in the pH range 2.7–9.8, while the response time was rapid (<15 s). Therefore, this potentiometric sensor displayed good selectivity for a number of cations such as alkali, alkaline earth, transition and heavy metal ions. The practical applicability of the electrode was demonstrated by its use as an indicator electrode in the potentiometric titration of Ho³⁺ ions with EDTA and in the determination of F^- in mouth wash samples.     

Electrochemical impedance spectroscopy of lead(II) ion-selective solid-state membranes

Silver sulphide/lead sulphide membranes were studied using electrochemical impedance spectroscopy. The influence of the electrolyte concentration and the membrane thickness were evaluated. The complex impedance plots have shown two capacitive loops: one at high frequency range, related with the charge transfer resistance at the interface membrane-Ag and a second one at low frequency range, associated with the diffusion process through the membrane. A simple model was used to take into account the experimental results: the changes of the potential with the time and the electrolyte concentration; the changes of the charge transfer resistance and the diffusion resistance with the electrolyte concentration. An empirical equation was used to calculate the diffusion coefficient of Ag⁺ inside the membrane.     

Reactions of bis(3-aminopropyl)amine with formaldehyde in the presence of a metal ion: Preparation of a metal-free macropolycycle and a dinuclear copper(II) complex

The reaction of bis(3-aminopropyl)amine with excess formaldehyde in the presence of Ni²⁺ ion produces the macropentacyclic compound L¹(ClO₄)₂ (1) L¹ = 1,3,7,11,13,17- hexaazapentacyclo[15.3.1.1^3.7.1^7.13.1^13.17]tetracosane). The dinuclear complex [Cu₂(L²)₂(H₂O)₂](ClO₄)₂ (2) (HL¹ = 1-(3-aminopropyl)-3-(hydroxymethyl)-1,3-diazacyclohexane) as well as 1 can be prepared by the condensation reaction in the presence of Cu²⁺ ion. Interestingly, 2 · 2H₂O exhibits uncommon magnetic behavior.     

Adsorption and desorption of copper(II) from solutions on new spherical cellulose adsorbent

An investigation was conducted on the adsorption and desorption of copper(II) from aqueous solutions with a new spherical cellulose adsorbent containing the carboxyl anionic group. Various factors affecting the adsorption were optimized. The adsorption of Cu²⁺ ions on the adsorbent was found to be dependent on the initial time and pH, the concentration, and the temperature. The adsorption process follows both Freundlich and Langmuir adsorption isotherms and was found to be endothermic (ΔH = 23.99 kJ/mol). The Cu²⁺ ions adsorbed on the adsorbent can be recovered with a NaOH or HCl aqueous solution. The maximum percentage of recovery is about 100% when 2.4 mol/L HCl solution is used. In addition, only 7.2% of the adsorption capacity is lost after 30 replications of the adsorption and desorption. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 478–485, 2002; DOI 10.1002/app.10114     

Electrochemical biosensor based on the interaction between copper(II) complex with 4,5-diazafluorene-9-one and bromine ligands and deoxyribonucleic acid

The copper complex of 4,5-diazafluorene-9-one (dafone) and bromine ligands ([Cu(dafone)₂]Br₂) was prepared and its interaction with double-stranded salmon sperm DNA (dsDNA) in pH 8.0 Britton-Robinson (B-R) buffer solution was studied by electrochemical experiments at the glassy carbon electrode (GCE). It was revealed that Cu(dafone)₂Br₂ could bind with salmon sperm DNA strands mainly by intercalation mode. The binding number of [Cu(dafone)₂]Br₂ for each salmon sperm dsDNA chain and equilibrium constant of the binding reaction were calculated to be 3 and 2.8 × 10¹² L³ mol⁻³, respectively. The Cu(dafone)₂Br₂ was further utilized as a new electrochemical DNA indicator for the detection of human hepatitis B virus (HBV) DNA fragment by differential pulse voltammetry (DPV). The difference of its electrochemical responses occurred between hybridized dsDNA duplex and probe DNA was explored to assess the selectivity of the developed electrochemical DNA biosensor. The constructed electrochemical DNA biosensor achieved a detection limit of 3.18 × 10⁻⁹ mol L⁻¹ for complementary target DNA and also realized a robust stability and good reusability.     

Effect of Cu(II) ligands on electroless copper deposition rate in formaldehyde solutions: An EQCM study

The electroless copper deposition rate for 6 Cu^II complexes decreases in the ligand sequence: nitrilotriacetic acid (NTA) > N,N,N′,N′-tetrakis-(2-hydroxypropyl)-ethylenediamine (Quadrol) > glycerol > L(+)-tartrate ~ sucrose > -tartrate. Both Cu^II complex stability and specific ligand effects were found to influence the Cu deposition process. The specific ligand effects are most obvious in the case of Quadrol (high kinetic activity at a high Cu^II complex stability), glycerol and sucrose (additional reaction of Cu₂O formation by interaction of Cu^II with ligand). According to the EQCM data for 11 Cu^II complexes (including data from the former study) the higher kinetic activity is demonstrated by complexes with ligands containing amino groups; this factor is more important for Cu deposition rate than copper complex stability. A potential dependence of the Cu reduction partial current on the electrode potential has been extracted from the EQCM data in the complete electroless plating bath. An increase in Cu^II reduction rate was found to occur in electroless plating solution for Cu^II complexes with NTA and Quadrol compared with that in formaldehyde-free solutions. Possible reasons for the acceleration of the partial Cu^II reduction reaction and the overall process kinetics are discussed using a hypothetical reaction sequence involving intermediate copper oxy-species and active Cu* formation as well as development of the preferred Cu surface structure.     

Immobilization of copper(II)-poly(N-vinylimidazole) complex on magnetic nanoparticles and its catalysis of oxidative polymerization of 2,6-dimethylphenol in water

Poly(N-vinylimidazole) (PVI) was grafted onto magnetic Fe₃O₄ nanoparticles through siloxane bonds to produce PVI-grafted Fe₃O₄ nanoparticles (shortened as Fe₃O₄-g-PVI). The amount of imidazolyl groups in Fe₃O₄-g-PVI was estimated to be 1.16 mmol/g by elemental analysis and thermal gravimetric analysis. The Fe₃O₄-g-PVI coordinated with Cu(II) to form the immobilized Cu(II)-PVI complex. The stoichiometric ratio between imidazolyl groups in Fe₃O₄-g-PVI and Cu(II) was found to be 4 and the complex formation constant (K) was calculated to be 5.6 × 10¹⁴ mol⁻⁴ L⁴. The immobilized Cu(II)-PVI complex was employed to catalyze the oxidative polymerization of 2,6-dimethylphenol (DMP) in water and showed excellent C O/C C selectivity to form PPO. After polymerization, the immobilized Cu(II)-PVI complex catalyst was collected by an external magnetic field and reused in the next run with additional immobilized catalyst and copper ions. After three runs of oxidative polymerization of DMP, the recovery rate of the immobilized Cu(II)-PVI catalyst was above 95% and the yield of PPO maintained as high as 79.2% with the addition of supplementary catalysts. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012