Determination of ultramicroquantities of Au(III) by its catalytic effect on 4-hydroxyl coumarone oxidation with potassium permanganate

A simple and fast kinetic method is based on the oxidation of 4-OH coumarone using KMnO₄ and the determination of ultramicroamounts of Au(III) by its catalytic effect on this reaction. The sensitivity of the method is 25 ng/mL. The relative error ranges between 9.20–3.90% for the concentration interval 5 × 10⁻⁸–2 × 10⁻⁷ g/mL. The selectivity of the method is very good, and the effect of foreign ions is investigated. The proposed approach has been applied to the determination of traces of Au(III) in copper ore. The text was submitted by the authors in English.     

Catalytic adsorptive stripping voltammetric determination of copper(II) on a carbon paste electrode

A catalytic adsorptive stripping voltammetric method for the determination of copper(II) on a carbon paste electrode (PCE) in an alizarin red S (ARS)-K₂S₂O₈ system is proposed. In this method, copper(II) is effectively enriched by both the formation and adsorption of a copper(II)-ARS complex on the PCE, and is determined by catalytic stripping voltammetry. The catalytic enhancement of the cathodic stripping current of the Cu(II) in the complex results from a redox cycle consisting of electrochemical reduction of Cu(II) ion in the complex and subsequent chemical oxidation of the Cu(II) reduction product by persulfate, which reduces the contamination of the working electrode from Cu deposition and also improves analytical sensitivity. In Britton-Robinson buffer (pH 4.56±0.1) containing 3.6×10⁻⁵ mol L⁻¹ ARS and 1.6×10⁻³ mol L⁻¹ K₂S₂O₈, with 180 s of accumulation at −0.2 V, the second-order derivative peak current of the catalytic stripping wave was proportional to the copper(II) concentration in the range of 8.0×10⁻¹⁰ to ∼3.0×10⁻⁸ mol L⁻¹. The detection limit was 1.6×10⁻¹⁰ mol L⁻¹. The proposed method was evaluated by analyzing copper in water and soil.     

Spectrophotometric determination of furosemide in pharmaceutical dosage forms using complex formation with Cu(II)

A simple, sensitive, and accurate spectrophotometric method has been developed for the assay of furosemide (FUR), which is based on the complexation of the drug with copper(II) at pH 3.2 using Mclivaine buffer solution to produce a green adduct. The latter has maximum absorbance at 790 nm and obeys Beer’s law within the concentration range 5–30 μg/mL. Regression analysis of the calibration data showed a good correlation coefficient (r = 0.9997) with minimum detection limit of 0.23 μg/mL. The proposed procedure has been successfully applied to the determination of this drug in tablets. In addition, the spectral data and stability constant for the mononuclear copper(II) complex of furosemide (CuFUR₂(MeOH)₂) are reported. The text was submitted by the author in English.     

Structure and magnetic properties of the copper(II) complexes with diacyl hydrazides of salicylic acid

The structures and results of the static magnetic susceptibility investigation of the copper(II) binuclear complex with salicylic acid diacyl hydrazide (H₂L), [Cu₂(L)(Py)₄] (I), and the copper(II) trinuclear complex with diacyl dihydrazide of salicylic and glutaric acids (H₆L′), [Cu₃(L′)(Py)₄] · 2Py (II), are described. The exchange antiferromagnetic interactions between the paramagnetic centers with the exchange interaction parameter −2J = 119 cm⁻¹ for dimer I and 14 cm⁻¹ for trinuclear complex II are detected.     

Crystal structure and strong antiferromagnetic interaction of a terephthalate-bridged binuclear copper(II) Complex, [{Cu(dipn)}2(μ-TPHA)](ClO4)2 (dipn = N-(3-aminopropyl)-1,3-propanediamine)

Three binuclear copper(II) complexes bridged by three different bridging ligands: μ-TPHA (terephthalato), μ-PHTA (phthalato) and μ-TCB (tetracarboxylatobenzene) have been synthesized. The crystal structure of [{Cu(dipn)}₂(μ-TPHA)](ClO₄)₂ where dipn = N-(3-aminopropyl)-1,3-propanediamine was solved at room temperature. The [{Cudipn}₂(μ-TPHA)](ClO₄)₂ complex consists of a μ-terephthalato bridging binuclear copper(II) cationic unit and two non-coordinated perchlorate anions. The TPHA ligand bridges in a bismonodentate fashion. The environment of the copper(II) ion is a distorted plane-square-planar coordination sphere. The magnetic properties of the three complexes have been investigated in the 75–300 K range, and show that the geometry of the Cu^II atom is the important factor for magnetic interactions in the terephthalato bridging binuclear copper(II) complexes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Stability constants of oxalate complexes of copper (II) and nickel (II) by paper electrophoresis

Summary Stability constants of copper (II) and nickel (II) oxalates have been determined by paper electrophoresis. Oxalic acid (0.005 mol dm⁻³) was added to the background electrolyte: 0.1 mol dm⁻³ HClO₄. The proportions of HC₂O ₄ ⁻ and C₂O ₄ ²⁻ were varied by changing the pH of the electrolyte, these anions yielding the complex ions MHC₂O ₄ ⁺ and M(C₂O₄) ₂ ²⁻ , average values of the stability constants for which are 10^2.4 and 10^7.6 respectively for Cu(II), and 10^2.3 and 10^6.5 for Ni(II) (μ=0.1,30°).     

Triphenyltetrazolium chloride as a new analytical reagent for molybdenum(VI): Application to plant analysis

Solvent extraction of molybdenum(VI) ion associate with triphenyltetrazolium chloride (TTC) has been studied. TTC was proposed as reagent for the spectrophotometric determination of micro amounts of molybdenum(VI) at λ_max 250 nm. The optimum conditions for extraction of molybdenum(VI) as an ionassociation complex with TTC has been determined. Beer’s law is obeyed in the range of 0.5–10 μg/mL molybdenum(VI). The molar absorptivity of the ion-pair is 1 × 10⁶ L/mol cm. The sensitivity of the method is 9.6 × 10⁻⁵ μg/cm². The characteristic values for the extraction equilibrium and the equilibrium in the aqueous phase are: distribution constant K _D = 32.64, extraction constant K _ex = 2.19 × 10¹⁰ association constant β = 6.71 × 10⁸. The interferences of different cations, anions on molybdenum(VI) determination were also investigated. A sensitive and selective method for the determination of microquantities of molybdenum(VI) has been developed. The determination was carried out without preliminary separation of molybdenum. A novel procedure of molybdenum(VI) extraction and spectrophotometric determination in different plant samples was examined.     

Catecholase biomimetic catalytic activity of copper(II) complexes with 2-methyl-3-amino-(3H)-quinazolin-4-one

The oxidation of catechol by molecular oxygen in the presence of a catalytic amount of copper(II) complex with 2-methyl-3-amino-(3H)quinazoline-4-one (MAQ) and various anions (Cl⁻, Br⁻, ClO ₄ ⁻ , SCN⁻, NO ₃ ⁻ and SO ₄ ^– ) was studied. The catecholase biomimetic catalytic activity of the copper(II) complexes has been determined spectrophotometrically by monitoring the oxidative transformation of catechol to the corresponding light absorbing o-quinone (Q). The rate of the catalytic oxidation reaction was investigated and correlated with the catalyst structure, time, concentration of catalyst and substrate and finally solvent effects. Addition of pyridine or Et₃N showed a dramatic effect on the rate of oxidation reaction. Kinetic investigations demonstrate that the rate of oxidation reaction has a first order dependence with respect to the catalyst and catechol concentration and obeying Michaelis–Menten Kinetics. It was shown that the catalytic activity depends on the coordination environment of the catalyst created by the nature of counter anions bound to copper(II) ion in the complex molecule and follows the order: Cl⁻ > NO ₃ ⁻ > Br⁻ > SO ₄ ^– > SCN⁻ > ClO ₄ ⁻ . To further elucidate the catalytic activity of the complexes, their electrochemical properties were investigated and the catecholase mimetic activity has been correlated with the redox potential of the Cu²⁺/Cu⁺ couple in the complexes.     

Adsorption-spectroscopic method for multielement analysis: Determination of Cr(VI), V(V), Ni(II), and Cu(II) from one sample using a two-layer adsorbent

The possibility of preconcentrating vanadium, chromium, copper, and nickel by the simultaneous adsorption in a flow-through mode on a two-layer adsorbent and the determination of metal ions by diffuse reflectance spectroscopy was studied. The adsorbent was made of a polyacrylonitrile fiber, one layer of which was filled with an AV-17 anion exchanger (PANV-AV-17), while another layer, with a KU-2 cation exchanger (PANV-KU-2). The procedure was based on the simultaneous preconcentration of vanadium and chromium on the first disk and nickel and copper on the second disk, by pumping the analyzed solution through both disks in a flow-through cell. Then, vanadium was determined on the disk of PANV-AV-17 with 8-hydroxyquinoline-5-sulfonic acid in 0.1 M HCl; next, chromium was determined with 1,5-diphenylcarbazide; the complex of vanadium was decomposed by 0.5 M H₂SO₄ and ascorbic acid. In the PANV-KU-2 disk, nickel was determined with dimethylglyoxime and then copper was analyzed with sodium diethyldithiocarbamate; the complex of nickel was decomposed with 1 M HCl. The selectivity factors were determined. A procedure was developed for the dynamic adsorption-spectroscopic determination of the following elements present simultaneously (μg/mL): V, 0.01–0.05; Cr, 0.002–0.015; Ni, 0.02–0.10; and Cu, 0.02–0.15. The results of analysis of model solutions are presented for different component ratios, RSD < 20%.     

Synthesis,crystal structures and magnetic properties of a radical ligand and its corresponding copper(II) complex

A new chelating radical ligand, IMMeBzIm (IMMeBzIm = 2-{2′-[(l′-methyl)benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl) and its copper(II) complex [Cu(IMMeBzIm)₂(ClO₄)]·(ClO₄) have been prepared and characterized by IR, magnetic and single-crystal X-ray analysis. In the crystal structures, both free IMMeBzIm and the complex crystallize in monoclinic space groups P2(1)/c and C2/c, respectively. The structure of IMMeBzIm consists of mononuclear molecules. In the complex, the coordination geometry around copper is a distorted square pyramid, and the apical position is occupied by one oxygen atom of ClO₄ ⁻ anion. A 1-D polymer is formed through intermolecular H-bond interactions. The variable-temperature magnetic susceptibility of the free IMMeBzIm suggests weak antiferromagnetic coupling with J = −1.12 cm⁻¹ where the spin Hamitonian is defined as Ĥ = −2 JŜ ₁ Ŝ ₂ between radical and radical.     

Liquid chromatographic determination of chelates of cobalt (II), copper (II) and iron (II) with 2-thiophonaldehyde-4-phenyl-3-thiosemicarbazone

Summary A new chelating reagent 2-thiophenaldehyde-4-phenyl-3-thiosemicarbazone (TAPT) has been examined for high performance liquid chromatographic (HPLC) separations of cobalt (II), copper(II) and iron (II) or cobalt (II), nickel (II), iron (II), copper (II) and mercury (II) as metal chelates on a C₁₈, 5μm column (250×4 mm i.d.) The chelates were eluted isocratically with methanol: acetonitrile: water containing sodium acetate and tetrabutylammonium bromide (TBA), and detected at 254 nm. A solvent extraction procedure was developed for simultaneous determination of the metals with detection limits within 0.02–2.5 μ g.mL⁻¹. The method was applied to the determination of copper, cobalt and iron in natural waters.     

Ternary complex of molybdenum(VI) with 4-nitrocatechol and tetrazolium blue chloride and its application to extraction-spectrophotometric analysis of ferrous metallurgy products

The formation of a new tenary complex of molybdenum(VI) with 4-nitrocatechol (NC) and tetrazolium blue chloride (BTC), which is easily extractable from water into dichloroethane, is reported. The optimum extraction conditions (pH, concentration of the reagents, extraction time) and composition of the complex (Mo: NC: BTC = 1: 2: 1) were found. The spectrophotometric parameters of the extract were determined as well. Beer’s law is obeyed for concentrations of Mo ranging from 0.2 to 6.7 μg/mL with the molar absorptivity λ₄₄₅ = 2.38 × 10⁴ L mol⁻¹ cm. A precise, sensitive, and simple method for determination of Mo in steels and ferromolybdenum was developed. The text was submitted by the authors in English.     

Copper(II)-cetyltrimethylammonium chloride-chromal blue G ternary complex and its application to the spectrophotometric determination of copper(II)

A sensitive spectrophotometric method for the determination of copper(II) based on a ternary complex with chromal blue G, a triphenylmethane reagent in the presence of cetyltrimethylammonium chloride, is described. The sensitivity of color reaction between copper and chromal blue G has been greatly increased by the sensitizing action of cetyltrimethylammonium chloride, a cationic surfactant. The color development of the ternary complex can be utilized in the highly sensitive spectrophotometric determination of copper. The molar absorptivity of the binary complex between copper and chromal blue G ε_630nm = 9.56 × 10³liters · mol⁻¹ · cm⁻¹ is enchanced on ternary complex formation to ε_{542 nm} = 4.78 × 10⁴liters · mol⁻¹ · cm⁻¹. The ternary complex gave a maximal absorbance at 542 nm in the pH range 9.8–11. Beer's law is obeyed up to at least 1.2 ppm of copper. The maximal absorbance of the ternary complex was found to develop within 5 min and then it remains constant for several hours. The formation constant of the ternary complex is calculated to be 8.6 × 10¹⁰ under these conditions.     

Optimization of analytical procedures for the simultaneous voltammetric determination of total Hg(II) in presence of Cu(II) in environmental matrices

The present work reports the critical comparison about the employment of three different supporting electrolytes (0.1 mol L⁻¹ HClO₄, 0.01 mol L⁻¹ EDTA-Na² + 0.06 mol L⁻¹ NaCl + 2.0 mol L⁻¹ HClO₄ and 0.1 mol L⁻¹ KSCN + 0.001 mol L⁻¹ HClO₄) and their instrumental and chemical optimisation for the simultaneous voltammetric determination of total mercury(II) and copper(II) in sediments and sea water at gold electrode, especially discussing the reciprocal interference problems.     

Synthesis,biological evaluation and biodistribution of the <Superscript>99m</Superscript>Tc–Garenoxacin complex in artificially infected rats

The labeling of garenoxacin (GXN) with technetium-99m (^99mTc) using different concentrations of GXN, sodium pertechnetate (Na^99mTcO₄), stannous chloride dihydrate (SnCl₂·2H₂O) at different pH was investigated and evaluated in terms of in-vitro stability in saline, serum, binding with multi-resistant Staphylococcus aureus (MDRSA) and penicillin-resistant Streptococci (PRSC) and its biodistribution in artificially MDRSA and PRSC infected rats. ^99mTc–GXN complex with 97.45 ± 0.18% radiochemical stability was prepared by mixing 3 mg of GXN with 3 mCi of Na^99mTcO₄ in the presence of 150 μL of SnCl₂·2H₂O (1 μg/μL in 0.01 N HCl) at a pH 5.6. The radiochemical stability of the complex was evaluated in normal saline up to 240 min of reconstitution. It was observed that the complex showed maximum RCP values after 30 min of the reconstitution and remained more than 90% up to 240 min. The complex showed radiochemical stability in normal saline at 37 °C up to 16 h with a 17.80% de-tagging. The complex showed saturated in-vitro binding with living MDRSA and PRSC as compared to the insignificant binding with heat killed MDRSA and PRSC. Biodistribution behavior of the complex was assessed in artificially infected with living and heat killed MDRSA and PRSC rats. It was observed that the accumulation of the complex in the infected (live MDRSA and PRSC) tissue of the rats was almost five fold than in the inflamed and normal tissue. The high radiochemical stability in normal saline at room temperature, promising in-vitro stability in serum at 37 °C, saturated in-vitro binding with living MDRSA and PRSC, specific biodistribution behavior and high infected (target) to normal (non-target) tissue and low inflamed (non-target) to normal (non-target) tissue ratios we recommend ^99mTc–GXN complex for in-vivo localization of infection caused by MDRSA and PRSC effective stains.     

Copper(II) bis(hexafluoroacetylacetonate) complexes with 2-(2-methyltetrazolyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole 1-oxides

An efficient procedure was developed for the synthesis of alkyltetrazolyl-substituted nitronyl nitroxides (L ¹ and L ²). These compounds were used to prepare the first alkyltetrazolyl-substituted imino nitroxides (L ³ and L ⁴). The molecular structures of L ³ and L ⁴ were confirmed by X-ray diffraction. Investigation of the products prepared by the reaction of copper(II) bis(hexafluoroacetylacetonate), Cu(hfac)₂, with nitroxides made it possible to divide ligands L ¹—L ⁴ into two groups. The reactions of spin-labeled tetrazoles L ¹—L ³ with Cu(hfac)₂ afford the heterospin complexes Cu(hfac)₂L₂, whereas L ⁴ serves as a bidentate ligand in the Cu(hfac)₂ L ⁴ complex. In the solid Cu(hfac)₂L₂ complexes, antiferromagnetic exchange interactions between the unpaired electrons of the nitroxide fragments of the adjacent molecules prevail, due to which μ_eff decreases with decreasing temperature, and the spins of nitroxides are completely compensated at 5–10 K. The Cu(hfac)₂ L ⁴ complex displays strong intramolecular ferromagnetic coupling, due to which μ_eff at room temperature is close to 2.9 μ_B. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 64–70, January, 2006.     

Capillary electrophoretic speciation of Cu(II) and Co(III) in the electroless copper plating baths

Summary A capillary electrophoretic method for the determination of Cu(II) and Co(III) chelates with ethylenediamine in electroless copper plating baths has been developed. The influence of carrier electrolyte parameters such as nature of counter-ion and pH were studied and discussed. The optimised separations were carried out in a fused silica capillary (57 cm × 75 μm I.D.) filled with an ethylenediamine sulfate electrolyte (20 mol L⁻¹ ethylendiamine, pH7.0 with H₂SO₄; applied voltage, +25 kV) using direct UV detection at 214 nm. The detection limits for a signalto-noise ratio of 3 and 10s hydrodynamic injection were 5×10⁻⁶ mol L⁻¹ for Cu(II) and 1×10⁻⁶ mol L⁻¹ for Co(III). The relative standard deviations of the peak areas for Cu(II) and Co(III) were found to be 1.5% and 2.4%, respectively, with five consecutive injections of standard solution containing 5×10⁻⁵ mol L⁻¹ of each metal ion. Application of the method to the speciation of Cu(II) and Co(III) complexes in copper plating bath samples is also demonstrated.     

Synthesis and characterization of the [Cu(Cin2bda)2]ClO4 and [Cu(Ncin2bda)2]ClO4 complexes: Crystal structure of [Cu(Ncin2bda)2]ClO4

Two copper(I) complexes [Cu(Cin₂bda)₂]ClO₄ (I) and [Cu(Ncin₂bda)₂]ClO₄ (II) have been prepared by the reaction of the ligands N²,N²′-bis(3-phenylallylidene)biphenyl-2,2′-diamine (L¹) and N²,N²′-bis[3-(2-nitrophenyl)allylidene]biphenyl-2,2′-diamine (L²) and copper(I) salt. These compounds were characterized by CHN analyses, ¹H NMR, IR, and UV-Vis spectroscopy. The C=N stretching frequency in the copper(I) complexes shows a shift to a lower frequency relative to the free ligand due to the coordination of the nitrogen atoms. The crystal and molecular structure of II was determined by X-ray single-crystal crystallography. The coordination polyhedron about the copper(I) center in the complex is best described as a distorted tetrahedron. A quasireversible redox behavior was observed for complexes I and II. The article is published in the original.     

An x-ray diffraction study of the reaction products of copper(II) chloride with N<Superscript>1</Superscript>,N<Superscript>2</Superscript>-bis(5-methylpyridin-2-yl)oxalamide

Polymeric complexes of [Cu₂Cl₂L₂]_∞ copper(I) chloride (1) (L = N¹,N²-bis(5-methylpyridin-2-yl)-oxalamide)) and {[Cu₂(C₂O₄)Cl₂L](L)·2H₂O}_∞ copper(II) chloride (2) are obtained. The complexes are studied by powder and single crystal XRD. It is found that during the reaction of L with copper(II) chloride in the formation of complex 1 copper(II) is reduced to copper(I), while the formation of complex 2 is accompanied by the hydrolysis of the ligand.     

Spacered dinuclear copper(<Emphasis Type="SmallCaps">II</Emphasis>) complexes with acyldihydrazones of aliphatic dicarboxylic acids and 2-hydroxy-5-nitroacetophenone

Dinuclear copper(II) complexes with acyldihydrazones of 2-hydroxy-5-nitroacetophenone (H₄L) of the composition Cu₂(Py)_xL·mEtOH were synthesized and characterized. In these complexes, the coordination polyhedra of the copper atoms are linked to each other by a polymethylene chain of different lengths, from one to five monomer units. The structure of the [Cu₂L·4Mrf] complex (Mrf is morpholine) based on acyldihydrazone of malonic acid was established by X-ray diffraction. The copper(II) atoms in this complex are [4+1]-coordinated and are spaced by 6.94 Å. At room temperature, the signal in the ESR spectra of solutions of the complexes based on acyldihydrazones of malonic, succinic, glutaric, and adipic acids has a seven-line hyperfine structure with the constant of (35.3–38.8)·10⁻⁴ cm⁻¹ (g = 2.109–2.112) due to exchange interactions between unpaired electrons and two equivalent copper nuclei. An increase in the length of the polymethylene chain to five monomer units hinders exchange interactions, and the ESR signal of the complex based on acyldihydrazone of pimelic acid has a four-line hyperfine structure with a _Cu = 72.7·10⁻⁴ cm⁻¹ typical of mononuclear copper(II) complexes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 229–234, February, 2007.