Showing papers on "Copper published in 1984"
TL;DR: In this article, the linear quadridentate N2S2 donor ligand 1,7-bis(N-methylbenzimidazol-2′-yl)-2,6-dithiaheptane (bmdhp) forms mono-and di-hydrate 1 : 1 copper(II) complexes which are significantly more stable toward autoreduction than those of the non-methylated analogue.
Abstract: The linear quadridentate N2S2 donor ligand 1,7-bis(N-methylbenzimidazol-2′-yl)-2,6-dithiaheptane (bmdhp) forms mono- and di-hydrate 1 : 1 copper(II) complexes which are significantly more stable toward autoreduction than those of the non-methylated analogue. The deep green monohydrate of the perchlorate salt crystallises as the mononuclear aqua-complex, [Cu(bmdhp)(OH2)][ClO4]2, in the monoclinic space group P21/n, with Z= 4, a= 18.459(3), b= 10.362(2), c= 16.365(3)A, and β= 117.14(1)°. The structure was solved and refined by standard Patterson, Fourier, and least-squares techniques to R= 0.047 and R′= 0.075 for 3 343 independent reflections with l > 2σ(l). The compound consists of [Cu(bmdhp)(OH2)]2+ ions and ClO4– counter ions. The co-ordination around copper is intermediate between trigonal bipyramidal and square pyramidal, with Cu–N distances of 1.950(4) and 1.997(4)A, Cu–O(water) 2.225(4)A, and Cu–S 2.328(1) and 2.337(1)A. In the solid state, the perchlorate dihydrate's co-ordination sphere may be a topoisomer of the monohydrate's. A new angular structural parameter, τ, is defined and proposed as an index of trigonality, as a general descriptor of five-co-ordinate centric molecules. By this criterion, the irregular co-ordination geometry of [Cu(bmdhp)(OH2)]2+ in the solid state is described as being 48% along the pathway of distortion from square pyramidal toward trigonal bipyramidal. In the electronic spectrum of the complex, assignment is made of the S(thioether)→ Cu charge-transfer bands by comparison with those of the colourless complex Zn(bmdhp)(OH)(ClO4). E.s.r. and ligand-field spectra show that the copper(II) compounds adopt a tetragonal structure in donor solvents.
7,886 citations
TL;DR: Human monocyte-derived macrophages took up and esterified the cholesterol from modified low density lipoprotein more extensively than from native low densitylipoprotein.
Abstract: Modification of low density lipoproteins by human arterial smooth muscle cells was characterized by increased electrophoretic mobility and increased content of malondialdehyde-like oxidation products reactive with thiobarbituric acid. Lipoprotein modification was promoted by micromolar concentrations of iron or copper in the culture medium and was metal ion concentration- and time-dependent. The ability of diverse media to promote smooth muscle cell-mediated low density lipoprotein modification correlated with their iron concentration. Therefore, metal ion concentration of culture media contributes substantially to low density lipoprotein modification in vitro. Human monocyte-derived macrophages took up and esterified the cholesterol from modified low density lipoprotein more extensively than from native low density lipoprotein. Metal ion-mediated modification of low density lipoprotein may be a contributing factor to the pathogenesis of arteriosclerosis.
526 citations
01 Jan 1984
TL;DR: As a consequence of the non-spherical symmetry of the copper(II) ion, d9 configuration, and of the influence of the Jahn-Teller, and pseudo Jahn Teller effect on six-coordinate geometries, the stereochemistries of copper( II) ion are characterized by non-rigid geometry (fluxional behaviour), and ranges of distorted geometry (Plasticity Effect) The latter may be connected by a series of Structural Pathways, which may be characterised by an "Electronic Criterion of Stereochemistry
Abstract: As a consequence of the non-spherical symmetry of the copper(II) ion, d9 configuration, and of the influence of the Jahn-Teller, and pseudo Jahn-Teller effect on six-coordinate geometries, the stereochemistries of the copper(II) ion are characterized by non-rigid geometries (fluxional behaviour), and ranges of distorted geometries (Plasticity Effect) The latter may be connected by a series of Structural Pathways, which may be characterised by an ‘Electronic Criterion of Stereochemistry’ for a related series of complexes, eg the [Cu(bipy)2X] [Y] complexes
441 citations
TL;DR: In this article, the dendritic growths of copper were electrodeposited in steady-state diffusion-limited conditions onto an initially point-like cathode, and their spatial extent R was inferred from the increased current and their mass M from the total charge transferred.
Abstract: Black dendritic growths of copper were electrodeposited in steady-state diffusion-limited conditions onto an initially point-like cathode. Their spatial extent R was inferred from the increased current and their mass M from the total charge transferred. Fractal behaviour M∝RD was observed with D = 2.43 ±0.03, in good agreement with computer simulations of diffusion-limited aggregation.
410 citations
TL;DR: In this paper, the partitioning of copper and molybdenum between silicate melts and aqueous fluids has been determined at 750°C and 1.4 Kb.
353 citations
TL;DR: Partage chimique de Cd, Cu, Ni et Zn dans 3 sols et un sediment ayant precedemment recu des additions massives de metaux lourds as discussed by the authors.
Abstract: Partage chimique de Cd, Cu, Ni et Zn dans 3 sols et un sediment ayant precedemment recu des additions massives de metaux lourds
341 citations
285 citations
TL;DR: In this paper, the difference d'energie S-T peut etre controlee par la nature des ligands terminaux lies aux ions Cu(II) (μ-oxalato).
Abstract: Dans le cas des complexes dinucleaires Cu(II) (μ-oxalato), la difference d'energie S-T peut etre controlee par la nature des ligands terminaux lies aux ions Cu(II). Etude structurale de trois nouveaux complexes
269 citations
TL;DR: Etude des structures cristallines du complexe acetate ferromagnetique [Cu 2 (L-Et)(OAc)][ClO 4 ] 2 et de complexe azoturo diamagnetiques [C 2 LEt(N 3 )]-BF 4 ) 2 ] 2, HL 4 ) as mentioned in this paper.
Abstract: Etude des structures cristallines du complexe acetate ferromagnetique [Cu 2 (L-Et)(OAc)][ClO 4 ] 2 et du complexe azoturo diamagnetique [Cu 2 (L-Et)(N 3 )](BF 4 ) 2 , HL-Et etant le coordinat heptadente N,N,N',N'-tetrakis(ethyl-1 benzimidazolyl-2) hydroxy-2 diamino-1,3 propane
262 citations
TL;DR: In this article, a new method is proposed for the determination of complexing capacities and conditional stability constants for complexes of copper(II) with dissolved organic ligands in seawater, based on ligand competition by the added ligand catechol for free metal ions.
259 citations
TL;DR: In this article, the authors studied the adsorption of lead, copper and cobalt by activated carbon from aqueous solution and found that the solution pH was the most important parameter affecting the adsoreption.
TL;DR: In this paper, the authors investigated the oxidation of fracture surfaces of chalcopyrite by means of X-ray photoelectron spectroscopy, and interpreted the formation of a sulfur-rich copper sulfide of stoichiometry CuS2.
Abstract: The oxidation of fracture surfaces of chalcopyrite has been investigated by means of X-ray photoelectron spectroscopy. Exposure of chalcopyrite to air resulted in iron becoming concentrated at the surface of the mineral to form an iron hydroxy-oxide. The sulfur spectrum of an oxidized surface, determined at 150 or 295 K, displayed new intensity at the high binding energy side of the peak arising from unaltered chalcopyrite. This is interpreted in terms of the formation of a sulfur-rich copper sulfide of stoichiometry CuS2. Extended exposure to air resulted in the formation of sulfate and copper(II). The products of oxidation of chalcopyrite in air-saturated ammonia solution were the same as those observed during exposure to air. Iron and some copper were dissolved in the oxidation in acid media and the resultant surface layer had a composition near Cu0.8S2 Reaction of an acid-leached surface with hydrogen peroxide produced elemental sulfur in addition to a metal deficient copper sulfide.
TL;DR: The CODATA Task Group on Thermophysical Properties is preparing a set of recommended values for the heat capacity, thermal expansion, and transport properties of key solids which are used in calibrating or checking measuring equipment.
Abstract: The CODATA Task Group on Thermophysical Properties is preparing a set of recommended values for the heat capacity, thermal expansion, and transport properties of key solids which are used in calibrating or checking measuring equipment. The present paper surveys selected data on heat capacity at constant pressure Cp of copper from 1 to 1300 K and tungsten from 1 to 3400 K. Selected values are tabulated for Cp and also for heat capacity at constant volume Cv. Interpolating functions are given for Cp.
TL;DR: The hypothesis that inadequate copper nutriture or altered copper metabolism contributes to the occurrence of ischemic heart disease is supported.
Abstract: Signs of copper depletion were produced in a healthy man by an amount of dietary copper (0.83 mg/day) similar to that in some contemporary diets. Urinary and fecal loss of copper exceeded intake. Plasma copper, ceruloplasmin, and superoxide dismutase activity in erythrocytes decreased. Cholesterol in plasma increased, and hematologic indices were unchanged. Lipid metabolism may be a more sensitive index of copper nutriture than are changes in hematology. The findings support the hypothesis that inadequate copper nutriture or altered copper metabolism contributes to the occurrence of ischemic heart disease.
TL;DR: In this article, a simple model, analogous to speciation in solution among soluble ligands, was developed to enable the distribution of metals within sediments to be estimated, which requires the conditional metal binding constants (slopes of the linear portions of the adsorption isotherms) to be evaluated for a small number of model sedimentary phases in isolation, as well as knowledge of the composition of the sediment and water.
Abstract: An understanding of the distribution of toxic trace metals and other materials of environmental interest among the different sedimentary phases is necessary to assess the hazard associated with pollution of aquatic sediments. A simple model, analogous to speciation in solution among soluble ligands, was developed to enable the distribution of metals within sediments to be estimated. The model requires the conditional metal binding constants (slopes of the linear portions of the adsorption isotherms) to be evaluated for a small number of model sedimentary phases in isolation, as well as knowledge of the composition of the sediment and water. The model has been applied to the distributions of copper and cadmium in estuarine sediments and predicts that iron and organic matter are the sedimentary constituents of greatest importance for these metals. Manganese phases may contribute to cadmium binding, but clay minerals and (probably) aluminosilicates are insignificant sinks for both copper and cadmium. The model predictions for copper and cadmium in estuarine sediments are in good semi-quantitative agreement with the results of selective extraction studies on natural sediments reported in the literature and studies reported here of cadmium uptake by natural sediments.
TL;DR: In this article, transition metal interferences in the determination of selenium using the hydride generation AAS technique were investigated in a system in which the seenium hydrides is generated in pure acid solution and comes into contact with the metal ions only in a second flask.
Abstract: Transition metal interferences in the determination of selenium using the hydride generation AAS technique were investigated in a system in which the selenium hydride is generated in pure acid solution and comes into contact with the metal ions only in a second flask. All investigated elements interfere in the ionic form with selenium when they are present in sufficiently high concentrations. Whenever a precipitation of the metallic species occurs, however, capture and decomposition of the selenium hydride by the finely dispersed metal appear to be the predominant mechanism of interference. In addition, this solid-gas reaction occurs typically at considerably lower interferent concentrations than the liquid-gas reaction of the ionic species. A substantial increase in the range of interference-free determination of selenium can be achieved by increasing the acid concentration of the solution for measurement because of the increased solubility of the reduced metal in the strong acid.
TL;DR: In this article, the effect of polyoxyethyleneglycole (PEG) on the copper deposition and dissolution was studied in an acid copper sulfate bath as a function of electrode potential, polymerization degree of PEG and Cl - concentrations.
Abstract: The offect of polyoxyethyleneglycole (PEG) on the copper deposition and dissolution were studied in an acid copper sulfate bath as a function of electrode potential, polymerization degree of PEG and Cl - concentrations. In the presence of Cl - , PEG adsorbed on the copper surface to give an adhesive film causing remarkable suppression of the reaction current in the wide potential range of copper deposition and dissolution. While, in the Cl - free solution, PEG suppressed the reaction current in the potential range less negative than -150mV vs Cu 2 +* /Cu . Only the PEG which has the polymer ions are grasped in PEG molecules.
TL;DR: In this paper, a reduction current is obtained when an aqueous solution of copper and catechol is subjected to differential-pulse cathodic stripping voltammetry (d.p.c.a.s.).
TL;DR: In this article, the authors describe the preparation and etude des complexes of a complex composed of [Cu(NH(py) 2 )(X)] and [C 2 H 4, C 3 H 6, ClO 4 ].
Abstract: Preparation et etude des complexes [(Cu(NH(py) 2 )(X)] Y(X=C 2 H 4 et C 3 H 6 , Y=ClO 4 ; X=C 2 H 2 , Y=BF 4 et [Cu(NH(py) 2 )(CO)ClO 4 ]
TL;DR: This reaction, dependent on the formation of oxygen radicals, was made the basis of a sensitive and specific assay for loosely bound copper in body fluids.
Abstract: Copper(II) ions, in the presence of 1,10-phenanthroline, O2 and a reducing agent, degrade DNA with the release of thiobarbituric-acid-reactive material. This reaction, dependent on the formation of oxygen radicals, was made the basis of a sensitive and specific assay for loosely bound copper in body fluids. When applied to certain extracellular fluids, trace amounts of copper could be detected in the lower micromolar range.
TL;DR: In this paper, the strength and nature of the binding of heavy metal ions to bacterial extracellular polymers has been investigated, and the conditional stability constants (Kt) for complexes formed between extracted Klebsiella aerogenes polymer and copper, cadmium, cobalt and nickel were determined, using a gel chromatographic technique.
TL;DR: In this article, the fraction of encaged phthalocyanine decreases in the sequence CoPc-X > NiPc X > CuPcX, which is interpreted with a respective increase of the Bronsted acidity in the zeolite framework.
TL;DR: A compartment model is proposed which describes the dynamics of different fractions of copper in worms living in varying soil environments and no longer contradict each other on toxicity and uptake of copper.
Abstract: Data in the literature on the toxicity and uptake of copper by soil invertebrates are contradictory. Copper toxicity and bioaccumulation studies were therefore performed using earthworms and oribatid mites. Field-simulating experiments in soil-filled plastic containers showed that earthworms try to escape moderately toxic situations and that they are much more sensitive than oribatid mites to temporary high Cu2+ concentrations in soils. The total copper concentration in the bodies of the earthworm species Octolasium cyaneum was measured in experiments with different soil types and different amounts of added CuSO4. The copper concentrations in the earthworms increased in response to the higher concentrations of the copper fraction extractable with 2.5% acetic acid in the soil. Furthermore, internal copper concentrations showed a slight tendency to oscillate. The worms died when the concentrations within their bodies exceeded about 100-120 ppm, calculated on a dry weight basis. To interpret the experimental results, a compartment model is proposed which describes the dynamics of different fractions of copper in worms living in varying soil environments. Applying this model, the different reports on toxicity and uptake of copper in the literature no longer contradict each other.
TL;DR: In this article, the products of surface oxidation of a natural sample of the copper iron sulphide mineral, bornite, have been determined from analysis of linear potential sweep voltammograms and from X-ray photoelectron spectroscopic examination of the oxidized layer.
Abstract: The products of surface oxidation of a natural sample of the copper iron sulphide mineral, bornite, have been determined from analysis of linear potential sweep voltammograms and from X-ray photoelectron spectroscopic examination of the oxidized layer. Anodic oxidation of bornite in alkaline media results initially in the formation of an iron(III) oxide/hydroxide and an iron-free copper sulphide of stoichiometry Cu5S4. The latter species is oxidized further at higher potentials to form a copper sulphide of lower copper content and cupric hydroxide. Air oxidation involves the first of these two steps. In acid solution, anodic oxidation yields iron(II) ions rather than an iron oxide in the first stage and copper(II) ions in the second. Sulphate and elemental sulphur are not formed under the experimental conditions investigated.
01 Oct 1984
TL;DR: The sedimentation rates of aluminium, cadmium, copper, iron manganese, nickel, phosphorus, lead, vanadium, and zinc in the Sargasso Sea have been determined from samples collected in a sediment trap 3200 m below the ocean surface as discussed by the authors.
Abstract: The sedimentation rates of aluminium, cadmium, copper, iron manganese, nickel, phosphorus, lead, vanadium, and zinc in the Sargasso Sea have been determined from samples collected in a sediment trap 3200 m below the ocean surface. The fluxes are temporally variable, being driven by the seasonal cycle of primary production in the surface waters. There is evidence to suggest anthropogenic perturbation of the copper, lead, and zinc fluxes. The measured fluxes imply short (>150 day) lifetimes of particulate trace elements in the surface layers.
TL;DR: In this article, the synthesis of σ-acetylide complexes of tungsten, iron, nickel, copper and silver has been studied and the results range from good to excellent, and the reactions are simpler to carry out than previous methods.
Abstract: Routes developed for the syntheses of σ-acetylide complexes of tungsten, iron, nickel, copper and silver include reactions of metal halide complexes with alk-1-ynes in organic amines, with copper(I) halides as catalysts, or in methanol in the presence of sodium methoxide. Yields range from good to excellent, and the reactions are generally simpler to carry out than previous methods.