Investigation of Cu(II)/2′, 3′-Isopropylidene Adenosine Complex

Abstract

The UV spectrum and polarographic behavior of Cu(II)/IpA complex was investigated, in an aqueous solution of Cu(II)/IpA complex, in Britton Robinson buffer solution at a pH from 5.0 to 8.0. At a low concentration of Cu(II)/IpA complex, maximum absorbance was shown to be 532 nm.

Only one polarographic wave was found dependent on a two electron reduction.

The composition ratio of the complex was obtained by both UV spectrum and polarography, it was found that the ratio of Cu(II) to IpA was 1:2. The polarography vas shown by a two-electron reduction wave.     

Polarographic Behaviour of Copper Complex with 3-(2′-Thiazolylazo)-2,6-diaminopyridine at Dropping Mercury Electrode

Abstract

The polarographic behaviour of Cu(II) has been investigated in the presence of increasing concentration of 3-(2′-Thiazolylazo)-2,6-Diaminopyridine (2,6-TADAP) at different pH values and in 50% ethanol. At all pH's the waves were found to be diffusion controlled and irreversible. The values of the kinetic parameters n_a, K_o and ? have been evaluated as a function of the ligand concentration. The maximum half-wave potential shifts were observed for the Cu(II) complex at pH 3.37. The polarographic wave height was proportional to the concentration of Cu(II). The method has also been applied to the determination of Cu(II) in aluminium alloys.     

Polarographic Studies on Se(IV) in Absence and Presence of Pb(II), Zn(II) and Sb(III) Ions in Aqueous N-(2-ACETAMIDO) Imino Diacetate Buffer Solutions

Abstract

The polarographic reduction and determination of selenite ions in absence and presence of a mixture of some cationic species such as, Pb(II), Zn(II) and Sb(III) in N-(2-acetamido) imino diacetate solutions, at constants of ionic strength 0.1 mol dm^?3 (KNO₃) and temperature 25°C was studied using direct current and differential pulse polarographic (DPP) techniques. It was shown that reduction of Se(IV) takes place along one, two or three waves depending on the pH value of the solution using the direct current polarographic measurements. The reduction of Se(IV) in N-(2-acetamido) imino diacetate buffer solutions was found to be reversible and involving six electron transfer process. Microcoulometric experiments was performed at the limiting current region of the different waves and at various pH values. Kinetic parameters and wave characteristics for the reduction of selenite ions have been calculated. A method for the analytical determination of selenite ions in either simple or quadruple mixture of ADA buffer solutions using DPP techniques are reported and discussed.     

Structural Elucidation of the Cu(II)- Streptomycin Complex. Indirect Estimation of Streptomycin by Atomic Absorption Spectroscopy

Abstract

The neutral [Cu(II) - streptomycin .4 H₂O] complex is prepared and characterized by elemental analysis, TGA, IR, electronic and ESR spectra. The bonding between Cu(II) and streptomycin is found to take place through a Cu-O bond. The indirect estimation of streptomycin sulfate by atomic absorption spectroscopy is affected by the addition of an excess of cupric ions in slightly alkaline medium; the unreacted copper is separated as insoluble carbonate. The concentration of streptomycin in its product with copper is then indirectly determined from a pre-drawn caliberation curve for standard copper sulfate solutions.     

Effect of Surfactant Microenvironment on SOD-like Activity of Cu(II)-Salicylate Complex

Cu(II)-salicylate was synthesized and characterized by X-ray diffraction. The reaction mechanism of the Cu(II) complex with superoxide anion was studied by ESR spectroscopy, and its (superoxide dismutase) SOD-like activity was determined by a modified illumination method in phosphate buffer (pH = 7.8), micelle solutions and lamellar liquid crystals formed from surfactants CTAB and TX-100. X-ray diffraction indicated that the Cu(II) complex had a formula Cu₂(Hsal)₄EtOHH₂O and a similar structure to the SOD active site. EPR spectra proved that the reaction mechanism of the Cu(II) complex catalyzing O ₂ ^.- dismutation was the same as that of the proposed dismutation reaction catalyzed by SOD. Results obtained by the NBT method indicated that the Cu(II)-complex showed SOD-like activity, and the effect of microenvironment created by surfactants on its activity was same as on SOD activity. The order of the inhibition of NBT reduction by the Cu(II)-complex in different microenvironments was: in phosphate buffer (pH = 7.8) > in TX-100 micelle > in TX-100 liquid crystal, and in nonionic TX-100 organized assemblies > in cationic CTAB organized assemblies. These results were explained by the catalytic effect of micelles, and by the space restriction and high viscosity of organized assemblies of surfactants.     

A Polarographic Method Determing Cu(II), Cu(I) and Metallic Copper Contents in Copper Oxide Samples

Abstract

A polarographic procedure was developed which permits the analysis of powdered cupric and cuprous oxides in the presence of metallic copper. To determine CuO, Cu₂O and metallic copper content in the sample two weight aliquots were used. The first aliquot was dissolved in medium of 50 % ethanol + 3 M hydrochloric acid + saturated ascorbic acid solution. Insoluable metallic copper was determined polarographically after its' separation and additional dissolving in concentrated nitric acid.

The second sample aliquot was dissolved in 6 M hydrochloric acid and the ratio of Cu(I) / Cu(II) in the solution was determined from the polarographic curves. To calculate CuO, Cu₂O and Cu content in a sample the proposed procedure was applied. The developed method provides the accurate results of the determination of CuO, Cu₂O and Cu content in a powdered mixture. The reproducibility expressed as the relative standard deviation is from 1 % to 5 %.     

Differential Pulse Polarography of the Cadmium(II)-Imidazole Complex System

Abstract

A differential pulse polarographic study of the complexation of cadmium(II) with imidazole gives the relationship, Ej/₂ = -0.798 – 0.132 log [imidazole]_t for the cadmium(II) half wave potential (E]/₂) with imidazole concentration. Also, the differences between the half-wave potentials (ΔEj/₂) of the complex and metal ion have been used to determine log g_n (6.75) and coordination number (4) for the cadmium-imidazole complex according to Subrahmanya's method.     

SYNTHESIS AND SPECTROSCOPIC STUDIES OF SOME NEW REDOX-ACTIVE BENZYLAMINE COMPLEXES OF COPPER(II) AND ESR STUDIES OF THEIR OXIDATIONREDUCTION PRODUCTS

Abstract

New Cu(II) complexes Cu(L′_x)₂, where L′_x=L′₁, L′₂, L′₃, L′₄ are monoanion of unsubstituted, 5-Cl, 5-Br and 3,5-di-Br-substituted 2-hydroxybenzylamines of redox-active N-(3,5-di-tert-butyl-1-hydroxyphenyl)-2-hydroxybenzylamines were synthesized. Each compound of L′_xH and Cu(L′_x)2 as well as products of their oxidation and reduction by PbO2 and PPh3, respectively, was characterized by IR, UV-visible and ESR spectroscopy. ESR results showed that one-electron oxidation of mononuclear tetrahedrally distorted Cu(L′_x)2 chelates with PbO2, via C-C coupling of the Cu(II)-stabilized ligand radical intermediates and by the oxidative dehydrogenation of amine-chelates, produce new Cu(II) complexes with square-planar geometry. The powder ESR spectra of these new Cu(II) complexes exhibit a triplet-state type pattern with the zero-field splitting due to interaction between the copper(II) pairs. Interaction of Cu(L′_x)2 with PPh3 via intramolecular ligand-metal electron transfer results in the formation of radical species and reduction of the metal center. All radical intermediates were characterized by ESR parameters.     

Polarographic behaviour of salicylaldehyde-2-pyridylhydrazone and its copper(II) complex

The polarographic behaviour of salicylaldehyde-2-pyridylhydrazone (SAPH) has been studied in aqueous buffer solution containing 40% ethanol using DC and DP polarographic methods. In the pH range 1.8–7.5 the observed single irreversible reduction wave is assigned to the splitting of the N-N bond and reduction of C=N centre. In alkaline medium, a second wave appears at a more negative potential due to the reduction of the salicylaldehyde which is formed by hydrolytic decomposition of the SAPH molecule. The effect of pH on the limiting current andE _1/2 as well as the reduction mechanism are discussed and compared with similar compounds. The kinetic parameters of the electrode reaction have been calculated.The analytical properties of the copper(II)-SAPH system is described. The complex gave rise to a single irreversible well-defined wave (E _1/2=–0.58 V at pH=5.2). The reaction process is diffusion controlled. A method is suggested for the determination of Cu(II) in presence of different metal ions as the difference in theirE _1/2 values is sufficient for the purpose.This work is taken partly from the M. Sc. Thesis of Jamal S. Shalabi     

Electroreduction of Mo(VI) Compounds in Ammonium–Acetate Solutions

The kinetics of cathodic reactions in ammonium acetate solutions proposed for electrodeposition of metallic molybdenum was studied. The reduction of molybdenum compounds in the oxidation state +6 was found to occur stepwise according to the scheme Mo(VI) → Mo(V) → Mo(III). The waves observed on the polarograms are complicated by adsorption effects. The reduction of molybdenum to the metallic state is possible only at high negative potentials of the cathode; under the polarographic analysis conditions, this wave was not recorded. The deposit that formed on the surface of the solid cathode during cathodic polarization (i = 0.5 A cm^–2) contains both molybdenum in the metallic state and molybdenum oxides. The ratio between the electrolysis products depends on the temperature of solution: a decrease in the temperature leads to an increase in the amount of metallic molybdenum.

     

Synthesis of new oxamide-based ligand and its coordination behavior towards copper(II) ion: spectral and electrochemical studies

A new ligand N,N'-bis{3-(2-formyl-4-methyl-phenol)-6-iminopropyl}oxamide (L) and its mono- and binuclear copper(II) complexes have been synthesized and characterized. The ligand shows absorption maxima at 249 and 360 with a weak transition at 455 nm. The ligand was found to be fluorescent and shows an emission maximum at 516 nm on excitation at 360 nm. The electronic spectra of the mono- and binuclear Cu(II) complexes exhibited a d-d transition in the region 520-560 nm characteristic of square planar geometry around Cu(II) ion. The ESR spectrum of the mononuclear complex showed four lines with nuclear hyperfine splitting. The binuclear complex showed a broad ESR spectrum with g=2.10 due to antiferromagnetic interaction between the two Cu(II) ions. The room-temperature magnetic moment values (micro(eff)) for the mono- and binuclear Cu(II) complexes are found to be 1.70 micro(B) and 1.45 micro(B), respectively. The electrochemical studies of the mononuclear Cu(II) complex showed a single irreversible one-electron wave at -0.70 V (E(pc)) and the binuclear Cu(II) complex showed two irreversible one-electron reduction waves at -0.75 V (E(pc)(1)) and -1.27 V (E(pc)(2)) in the cathodic region.     

COMPLEXATION OF METAL IONS WITH 3,5-DI-TERT-BUTYL-1,2-BENZOQUINONE-1-MONOOXIME,ESR STUDIES OF RADICAL INTERMEDIATES

Abstract

The possibility of chelate formation of 3,5-di-terf-butyl-o-benzoquinone-1-monooxime with Cu(II), Co(II), Ni(II), Mn(II), Pd(II) metal ions under N₂ and in air have been investigated. It was found that complexation of metals except Cu(II) and Mn(II) was accompanied by formation of various stable radical species under air. The complexation of Co(II) even under N₂ unlike other metal ions, results in the formation of very stable radical species, which are assigned to phenazinyl type radical. ESR examination of reduction of bis(3,5-di-tert-butyl-o-benzoquinone-1-monooximato)M(II) (M = Cu, Pd) with triarylphosphines P(C₆H₄ X)₃ (X = H, m-Cl, m-CH₃, p-Et₂N) reveal the formation of the N-(2′-hydroxy-3,5-di-tertbutylphenyl)-4′,6′-di-tertbutyl-o-benzosemiquinone iminate radical. Finally, ESR spectra of Cu(II), Ni(II), and Mn(II) complexes at 300 and 130 K, as well as reaction of bis(oximato)Ni(II) with PPh₃ have been studied.     

Synthesis,Crystal Structure and Properties of a 4,4′-Bipyridine Bridged Trigonal-Bipyramidal Copper Homobinuclear Complex with Tris(2-Aminoethyl)amine

The synthesis of the binuclear complex [(tren)Cu(4,4'-bipy)Cu(tren)] (ClO₄)₄ where tren = tris(2-aminoethyl) amine and 4,4'-bipy = 4,4'-bipyridine, is described. Single-crystal X-ray diffraction study of the homobinuclear complex shows that two copper(II) ions are bridged by 4,4'-bipyridine and each copper(II) ion is trigonal-bipyramidally coordinated, with tren occupying four sites [Cu-N = 2.030(2), 2.047(2), 2.078(2), and 2.119(2) Å respectively] and a bridging 4,4'-bipyridine in the apical position. The Cu-Cu distance is 11.11 Å. In variable-temperature ESR spectra, the presence of hyperfine structure suggest that some interaction exists between the two copper(II) ions. Temperature-dependent susceptibility studies indicate that it is a weak ferromagnetic interaction with 2J = 1.23 cm^-1.     

A polarographic study of the complexes of pontachrome violet sw

In a polarographic study of the aluminum, iron(II), cobalt(II), nickel, zinc, cadmium, manganese(II), and magnesium complexes with Pontachrome Violet SW, a 2.2'-dihydroxyazo dye, it was found that each complex produced a wave at more negative potentials than the dyo alone. Values for the diffusion current constant, I_d, for each complex were calculated from data obtained for alkaline solutions. Calculations of the ratio of dye molecules to each cation gave maximum values corresponding to expected values based on the usual coordination number of the cation and a bidentate ligand.     

Polarographic and Voltammetric Study of the Sc(III)-Acid Chrome Blue K Complex and Determination of Trace Scandium

Abstract

A new system of polarographic adsorptive wave for determining trace scandium was proposed. In 0.2 mol/L NH₄OAc, the Sc(III)- ACBK [1,8- dihydroxy- 2- (2- hydroxy- 5- sulfo- 1- phenylazo)- 3,6- disulfo- naphthalene, called acid chrome blue K] complex emerged a sensitive adsorptive complex wave(Ep′ = -0.67V). The molar ratio of Sc(III) to ACBK in the complex was established as 1: 2 and the apparent stability constant β₂ = 2.7 × 10¹⁵. But for Y(III), the molar ratio was 1: 1 and β = 1.5 × 10⁵. Because of the particularity of Sc complex, the sensitivity and the selectivity of determination Sc are much better than that of other rare earth ions. The detection limit is 1.1 × 10^?7 mol/L for oscillopolarography and 2.0 × 10^?8 mol/L for adsorptive stripping voltammetry.     

Catalytic Determination of Selenium in Human Hair by Polarography Using Glutathione

Abstract

A catalytic polarographic method has been proposed for the accurate determination of selenium in human hair. This method is based on the formation of Se(0)-GSH complex in alkaline medium which gives a catalytic reduction wave in polarography. The current observed is directly proportional to the amount of selenium present. The method has been applied for the determination of selenium in human hair and the recovery of added selenium from hair is found to be 97.5 to 102%. A suitable mechanism for the reduction process involving the catalytic reduction of oxidised glutathione is proposed.     

A NOVEL BINUCLEAR COPPER(II) COMPLEX: BIS[1,10-PHENANTHROLINE-N,N′-MALEATO- O,O′-COPPER(II)] DIMETHANOL TETRAHYDRATE

Abstract

A novel binuclear Cu(II) complex, [Cu₂(mal)₂(phen)₂]. 4H₂O. 2MeOH (phen= 1,10-phenanthroline, mal = maleato dianion), has been synthesized and characterized by elemental analysis, IR spectroscopy, solid-state ESR analysis and X-ray single crystal study. The complex consists of [Cu(mal)(phen)] subunits with two water and one methanol solvate molecules. The subunits show a distorted planar arrangement, existing in centrosymmetrically related pairs in the crystal packing. They have a distorted four-coordinate square-planar arrangement of N and O atoms about the central Cu atom; pairs of these [Cu(mal)(phen)] subunits form dimers by interaction of the fifth position on each Cu center with an O atom of a maleato ligand of the associated subunit with a Cu-Cu distance of 3.3425(9) å. The coordination around each Cu atom is best described as distorted square-pyramidal. The lattice water and methanol molecules are also confirmed by the TG study and IR spectra. The X-band solid-state ESR spectrum at room temperature exhibits an anisotropic feature with g′ = 2.24, g′ = 2.06.     

ELECTRON SPIN RESONANCE OR Pd(I). III: The Nature of the Metal-ligand Bonds in Square Planar Complexes of Palladium(I)

Abstract

ESR spectra for a variety of palladium(I) complexes produced in the powders and the frozen solutions of palladium(II) complexes by γ -ray irradiation have been interpreted in terms of the nature of the metal-ligand bonds. It has been found that the covalency for the palladium-ligand σ-bond increases in the order of Pd[sbnd]O, Pd[sbnd]Cl < Pd[sbnd]N < Pd[sbnd]S, Pd[sbnd]C, and that the nature of the metal-ligand bond in palladium(I) complexes is very similar to that in copper(II) complexes. The ratio of the magnitude of the ligand field splitting for palladium(I) complex to that for the copper(II) complex with the same ligand has been estimated from the comparison of their g values.     

Synthesis,Spectral Studies and Bio‐activity of Some Ligand Bridged Polymeric Transition Metal Complexes of Acetone p‐Amino Acetophenone Isonicotinoyl Hydrazone

Ligand bridged polymeric complexes of the type [M(apainh)(H₂O)X] where, M=Mn(II), Co(II), Ni(II), Cu(II), and Zn(II); X=Cl₂ or SO₄; apainh=acetone p‐amino acetophenone isonicotinoyl hydrazone have been synthesized and characterized. The complexes are stable solids, insoluble in common organic solvents and are non‐electrolytes. Magnetic moments and electronic spectral studies suggest a spin‐free octahedral geometry for all Mn(II), Co(II), Ni(II), and Cu(II) complexes. IR spectra show tridentate nature of the ligand bonding through two >C?N and a >C?O groups. X‐ray powder diffraction parameters for some of the complexes correspond to orthorhombic and tetragonal crystal lattices. Thermal studies (TGA and DTA) of [Mn(apainh)(H₂O)SO₄] complex show multi‐step decomposition pattern of both an endothermic and exothermic nature. ESR data of Cu(II) chloride complex in solid state show an axial spectra, whereas, Cu(II) sulfate complex is isotropic in nature. The complexes show a significant antifungal activity against a number of pathogenic fungal species and antibacterial activity against Pseudomonas sp. and Clostridium sp. The metal complexes are more active than the ligand.     

Studies on Polarographic Adsorptive Wave of the System of the Rare Earth (III)-Copper(Ii)-M-Trifluomethyl Chlorophosphonazo

Abstract

A new heteronuclear complex, rare earth (III)-copper (II)-m-trifluomethyl chlorophosphonazo (CPA-mCF₃) system for determining trace rare earth ions is presented. In a medium of 0.02mol/L NH₄Cl,1. 0×10^?3mol/L Cu(II),1.0×10^?5 mol/L CPA-mCF₃, a very sensitive polarographic adsorptive wave is observed by using a single sweep oscillopolarograph at about –0.83V (vs. Ag/AgCl). The linear relationship between the peak current and the concentration of rare earth exists from 6. 0×10^?9 to 1. 0×10^?6 mol/L. The detection limit of rare earth is down to 2. 0×10^?9 mol/L for Tm³⁺. This method has been applied to determine trace RE in several samples of Chinese tea. The results are satisfactory. The composition of the complex is detected as RE (II): Cu (II): CPA-mCF₃ = 1: 1: 2.