Aqueous Solutions Of Cu Research Articles

Structural parameters of Cu2+ aqua complexes in aqueous solutions of its salts

Published data of various research techniques and own experimental results obtained by the X-ray structural analysis concerning structural characteristics of copper(II) aqua complexes in aqueous solutions of its salts under standard conditions have been generalized. Structural parameters of the nearest environment of this ion, such as coordination number, interparticle distances, and ionic association types, were considered. The possibility of the Jahn-Teller effect realization in aqueous solutions of Cu2+ salts was examined.

C3-Functionalized Cyclotriveratrylene Derivative Bearing Quinolinyl Group as a Fluorescent Probe for Cu2+

A new C(3)-functionalized cyclotriveratrylene (CTV) bearing three fluorogenic quinolinyl groups was synthesized and studied as a fluorescent probe. The CTV derivative exhibited a selective response of fluorescence enhancement toward Cu(2+). The fluorescence intensity in CH(3)CN was increased until the [Cu(2+)]/[CTV derivative] mole ratio was 3. Moreover, C(3)-functionalized CTV(2-quinolinemethyl)(3) was applied to a visible fluorescent probe by using a plasticized polymeric membrane. The emission profile was observed by a fluorescence microscope after immersing the membrane in a 1 x 10(-5) M aqueous solution of Cu(2+).

Fluorescence Quenching of Pheophytin‐a by Copper(II) Ions

Abstract A method was developed for determination of Cu(II) ions quantitatively by measuring fluorescent intensity of pheophytin‐a (Pheoa) solution. The Pheoa was obtained by de‐intercalation of magnesium from the porphyrin ring of chlorophyll‐a (Chla) extracted from fresh spinach leaves. Its two UV‐Vis absorption peaks at 505 and 535 nm in acetone solution have been observed but disappeared when the acetone solution of Pheoa was mixed with a Cu(II) ion aqueous solution. A fluorescence quenching phenomenon was thus observed when the acetone solution of Pheoa was mixed with an aqueous solution of Cu(II) ions. However, other physiologically relevant cations rarely caused any quenching fluorescence of Pheoa under the same experimental conditions. Kinetics of the fluorescence fading process was investigated by measuring the effects of Cu(II) ion concentration, reaction time and reaction temperature on the fluorescence intensity of the Pheoa acetone solution. An activation energy of (10±1) kJ·mol−1 was estimated from Arrhenius empirical relation assuming that the interaction between the Pheoa and the Cu(II) ions was the first order reaction. The calibration graph obtained with the fluorescence was linear over the Cu(II) concentration range of 8.0×10−5−8.0×10−7 mol·dm−3 with a detection limit of 8.0×10−7 mol·dm−3 for Cu(II) ion.

Synthesis and characterization of metal(II) complexes of poly(3-nitrobenzylidene-1-naphthylamine-co-succinic anhydride)

Abstract The alternating copolymer poly(3-nitrobenzylidene-1-naphthylamine-co-succinic anhydride) was synthesized from the Schiff base, 3-nitrobenzylidene-1-naphthylamine and succinic anhydride using hydroquinone monomethyl ether under nitrogen atmosphere. The molecular weight of the copolymer was determined by gel permeation chromatography. The metal–polymer complexes were synthesized by the reaction of THF solution of the alternating copolymer with aqueous solution of Cu(II) and Ni(II) acetates. The elemental analysis of the metal–polymer complexes suggests that the metal to ligand ratio is 1:2. The IR spectral data indicate that the metal ions are coordinated through the oxygen of the keto and ester groups. The UV–Visible, magnetic moments and ESR studies indicate square planar geometry for Cu(II) and distorted octahedral geometry for Ni(II) complexes. XRD studies revealed that the copolymer and its Cu(II) complex are crystalline, while the Ni(II) complex is amorphous. The intrinsic viscosity of the copolymer, thermal properties of metal–polymer complexes and their catalytic activity are discussed.

Hydration of Copper(II): New Insights from Density Functional Theory and the COSMO Solvation Model

The hydrated structure of the Cu(II) ion has been a subject of ongoing debate in the literature. In this article, we use density functional theory (B3LYP) and the COSMO continuum solvent model to characterize the structure and stability of [Cu(H2O)n](2+) clusters as a function of coordination number (4, 5, and 6) and cluster size (n = 4-18). We find that the most thermodynamically favored Cu(II) complexes in the gas phase have a very open four-coordinate structure. They are formed from a stable square-planar [Cu(H2O)8](2+) core stabilized by an unpaired electron in the Cu(II) ion d(x(2)-y(2)) orbital. This is consistent with cluster geometries suggested by recent mass-spectrometric experiments. In the aqueous phase, we find that the more compact five-coordinate square-pyramidal geometry is more stable than either the four-coordinate or six-coordinate clusters in agreement with recent combined EXAFS and XANES studies of aqueous solutions of Cu(II). However, a small energetic difference (approximately 1.4 kcal/mol) between the five- and six-coordinate models with two full hydration shells around the metal ion suggests that both forms may coexist in solution.

Zirconia-Supported Cu-KNO3 Catalyst: Characterization and Catalytic Behavior in the Catalytic Combustion of Soot with a NO/O2 Mixture

The catalytic combustion of diesel soot was studied in the presence of catalysts: CuZrO2, KNO3ZrO2, and CuKNO3ZrO2. The catalysts were prepared by impregnation of ZrO2·nH2O into an aqueous solution of Cu(NO3)2, KNO3, or both salts simultaneously. The catalysts were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and temperature-programmed reduction (TPR). Cu(n)KNO3ZrO2 catalysts present high activity, and the value of the combustion temperature decreases 200 °C with respect to the temperature of the process without catalyzing, with Tmax values between 370 and 380 °C. The activity is associated with KNO3 presence, and the role of KNO3 can be attributed to (i) an increase of contact between soot and the surface of the catalyst and (ii) a redox reaction in which the nitrate is reduced to nitrite by reaction with carbon and again reoxidized to nitrate. The copper contribution is associated with the reaction selectivity toward CO2 formation.

Synthesis of Copper Dendrite Nanostructures by a Sonoelectrochemical Method

Copper dendrites have been prepared by a sonoelectrochemical process from an aqueous solution of Cu(2+) in the presence of polyvinyl alcohol. A SEM image of the morpholohy of the copper formed on the electrode after one electric pulse is presented. A subsequent sonic pulse removes the copper from the electrode surface, cleaning it for the next step. The formation of the dendrites is accounted for by the "drying-mediated self-assembly of nanoparticles" theory.

The Influence of Macrocyclic Tetraamine Immobilization in Langmuir Monolayers on Complex Formation Selectivity

Selective complex formation in Langmuir dicetyl cyclene monolayers on the surface of aqueous solutions of Cu(II), Ni(II), and Zn(II) salts and their mixtures was studied. The effect of selectivity “inversion” of diphilic cyclene immobilized in monolayers on the surface of solutions of a mixture of copper(II) and nickel(II) salts was observed; the inversion was induced by a change in subphase pH. An analysis of the isotherms of monolayer compression and X-ray fluorescence spectra of the corresponding Langmuir-Blodgett films showed that subphase acidification caused a gradual transition from the selective formation of copper-containing macrocyclic complexes to selective complex formation between the ligand and nickel ions. The effect observed was not characteristic of complex formation with similar unsubstituted tetraamines in bulk solution. The phenomenon was interpreted from the point of view of specific conformational transitions of the diphilic macroring in the two-dimensional system organized at the interphase boundary.

A Seed-Mediated Growth Method for Vertical Array of Single-Crystalline CuO Nanowires on Surfaces

The preparation and characterization of a large-scale vertical array of single-crystalline CuO nanowires on different material surfaces is demonstrated for the first time. The procedure simply involved a room-temperatures liquid–solid growth process of attached CuO nanoseeds on ITO surface in the mixed aqueous solution of Cu(CH3COO)2 and NH3. By controlling the concentration of the chemical precursors in the growth solution, we can fabricate variable-shape 1D structures of CuO, such as nanowires and nanobelts. The FESEM image analysis indicated that these nanowires feature uniform size with tiny structures that have diameters and lengths in the range of 10 and 100 nm, respectively, and tend to form a bundlelike structure at the top end of the wires. The high-resolution transmission electron microscopy (HRTEM) study on individual CuO NWs reveals that the NWs are single-crystalline with growth orientation is [110]. The XRD analysis of the samples revealed that the nanostructures were a high-crystalline CuO ...

Saturation effect at high laser pulse energies in laser-induced breakdown spectroscopy for elemental analysis in water

AbstractSaturation effects in laser-induced breakdown spectroscopy in water for elemental analysis have been investigated. Existing theoretical model of laser-induced plasma in solids has been applied to liquid phase under some simplifying assumptions to take account of the laser pulse energy dependence of atomic emissions from Na and Cu in aqueous solution. The theory was found to explain the emission process for laser energies up to but below the saturation level. The saturation limit of the emission with laser pulse energy corresponds well with that of the plasma temperature deduced from blackbody emission considerations. The saturation energies for atomic emissions were found to be lower for bulk excitations compared to water jet excitations. The dependence of signal strength on sample concentration indicated that the concentration values at saturation are lower at higher laser energies, as is expected from the theoretical model.

Regular oscillatory behavior of aqueous solutions of Cu II salts related to effects on equilibrium dynamics of ortho/para hydrogen spin isomers of water

Cell surface and growth-related NADH oxidases with protein disulfide-thiol interchange activity, ECTO–NOX, exhibit copper-dependent, clock-related, temperature-independent and entrainable patterns of regular oscillations in the rate of oxidation of NAD(P)H as do aqueous solutions of copper salts. Because of time scale similarities, a basis for the oscillatory patterns in nuclear spin orientations of the hydrogen atoms of the copper-associated water was sought. Extended X-ray absorption fine structure (EXAFS) measurements at 9302 eV on pure water were periodic with a ca. 3.5 min peak to peak separation. Decomposition fits revealed 5 unequally spaced maxima similar to those observed previously for Cu IICl 2 to generate a period length of about 18 min. With D 2O, the period length was proportionately increased by 30% to 24 min. The redox potential of water and of D 2O also oscillated with 18 and 24 min period lengths, respectively. Measurements in the middle infrared spectral region above a water sample surface revealed apparent oscillations in the two alternative orientations of the nuclear spins (ortho and para) of the hydrogen atoms of the water or D 2O with 5 unequally spaced maxima and respective period lengths of 18 and 24 min. Thus, the time keeping oscillations of ECTO–NOX proteins appear to reflect the equilibrium dynamics of ortho–para hydrogen atom spin ratios of water where the presence of metal cations such as Cu II in solution determine period length.

Synthesis and chelation properties of new polymeric ligand derived from 8-hydroxy-5-azoquinoline hydroxy benzene

8-Hydroxy-5-azoquinoline phenyl methacrylate-formaldehyde (8H5AQPMA-F) macromonomer was prepared from methacryloyl chloride with condensation products of 8-hydroxy-5-azoquinoline phenol-formaldehyde, and polymerized in DMF at 70 °C using benzoyl peroxide as free radical initiator. Poly(8H5AQPMA-F) was characterized by infrared and nuclear magnetic resonance spectroscopic techniques. Polychelates were obtained when the DMF solution of the resin containing few drops of ammonia was treated with the aqueous solution of Cu(II)/Ni(II). Elemental analysis of the polychelates indicates that the metal to ligand ratio was about 1:2. The IR spectra of polychelates suggest that the metals were coordinated through the oxygen of the phenolic-OH group and nitrogen of the quinoline ligand. The DRS and magnetic moment data indicate a square planar for Cu(II) complex whereas octahedral for Ni(II) complex. The TGA data revealed the thermal stability of the resin and the polychelates. X-ray diffraction study revealed the incorporation of the metal ions significantly enhanced the degree of crystallinity. The sorption properties of the chelate-forming resin towards various divalent metal ions [Cu(II) and Ni(II)] were studied as a function of pH and electrolyte.

A New Strategy for the Improvement of the N2Adsorption Properties of Copper-Ion-Exchanged MFI-Type Zeolites at Room Temperature

A copper-ion-exchanged MFI-type zeolite, CuMFI, which exhibits an extremely efficient adsorption of the dinitrogen (N2) molecule at room temperature, has been successfully prepared by ion exchange in an aqueous solution of Cu(CH3COO)2 containing a component of NH4CH3COO. This ion-exchange method has unique characteristics as follows; first, the copper ion exchange takes place exclusively on the ion-exchangeable site that acts as the active site for N2 adsorption, and second, the extent of the reduction of the divalent copper ion exchanged attains a high value of 88%. In addition, the CuMFI sample thus prepared exhibits a high efficiency for N2 adsorption at 298 K where the monovalent copper ions act as adsorption sites; approximately 86% of them are effective for N2 adsorption. In this case, the heats of adsorption of N2 were large, 87−60 kJ mol-1. These observations were rationalized as showing that the site-selective ion exchange with copper ions occurs, accompanying acetate ligands by which the effect ...

Preparation of CuO/ZnO/Al 2O 3 catalysts for methanol synthesis using parallel-slurry-mixing method

A series of CuO/ZnO/γ-Al 2O 3 catalysts with different Al 2O 3 contents were prepared using the parallel-slurry-mixing method, in which an aqueous solution of Cu 2+ and Zn 2+ mixed nitrates and an aqueous solution of Na 2CO 3 were poured into a precipitation vessel containing γ-Al 2O 3 slurry in a parallel-flow manner. The catalyst structure and its performance for methanol synthesis were investigated. The results indicated that Al 2O 3 as a structural promoter can inhibit CuO and ZnO crystallites from enlarging during calcination. The catalyst with a Cu/Zn/Al ratio of 4/5/1 (molar ratio) exhibits the highest catalytic activity. With an increase in Al content, the amount of (Cu 0.3Zn 0.7) 5(CO 3) 2(OH) 6 phase in the catalyst precursor before calcination decreases, whereas that of Cu 2CO 3(OH) 2 phase increases; (Cu 0.3Zn 0.7) 5(CO 3) 2(OH) 6 in the precursor is beneficial to the catalytic activity of the final Cu/ZnO/γ-Al 2O 3 catalyst.

Synthesis and metal uptake studies on poly(8‐hydroxy‐5‐azoquinolinephenylacrylate‐formaldehyde) resin and its metal complexes

Abstract8‐hydroxy‐5‐azoquinolinephenylacrylate‐formaldehyde (8H5AQPA‐F) macromonomer was prepared from acryloylchloride, with condensation products of 8‐hydroxy‐5‐azoquinolinephenol‐formaldehyde, and polymerized in DMF at 70°C using benzoyl peroxide as free radical initiator. Poly(8H5AQPA‐F) was characterized by infrared and nuclear magnetic resonance spectroscopic techniques. Polychelates were obtained in alkaline solution of polymeric ligand, with the aqueous solution of Cu(II) and Ni(II). Elemental analysis of polychelates suggests that the metal to ligand ratio is about 1:2. The polymer metal complexes were also characterized by IR, XRD, magnetic moments, and thermal analysis. The effects of pH and electrolyte on the metal uptake behavior of the resin were also studied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 797–802, 2007

New insight into N2 adsorption and ion-exchange features of CuMFI with different Si/Al ratios

The effects of the Si/Al ratio of the mother MFI on the N2 adsorption phenomena at 301 K and on the ion-exchange features of copper-ion-exchanged MFI zeolites (CuMFI) were investigated. The CuMFI samples were prepared by ion exchange in an aqueous solution of Cu(C2H5COO)2, Cu(CH3COO)2, CuCl2 or Cu(NO3)2. The sample with an Si/Al ratio of 19.8, which had been prepared by using a Cu(C2H5COO)2 solution, exhibited extremely efficient N2 adsorption in terms of both the number of adsorbed molecules and its energetic behaviour, as compared to samples with other Si/Al ratios and/or with other ion-exchange solutions. The coordination environment of the copper ion adsorbing N2 on this sample was clarified for the first time by analysis of the EXAFS spectra. The IR and DR-UV-Vis spectra revealed that the state of exchanged Cu2+ in CuMFI differs remarkably, depending on the value of the Si/Al ratio of the MFI and the types of counter ion in the exchange solution. The Cu2+ species coordinated with propionate or acetate ion were preferentially ion-exchanged in samples with higher Si/Al ratios (i.e., 19.8 and above), in comparison with aqua complexes of Cu2+ ions. From the measurements of heats-of-adsorption of CO and photoemission spectra, it was elucidated that the relative proportion of the number of the sites located in the neighbourhood of the three lattice oxygen atoms (i.e., three-coordinate sites) to the total number of exchangeable sites in MFI including the two-coordinate sites increased with an increase in the Si/Al ratio; Cu2+ with propionate or acetate ion were exchanged selectively on the three-coordinate sites. The DR-UV-Vis and EPR spectroscopic signatures of two different Cu2+ species located in the two- and the three-coordinate sites were determined.

Preparation and performance of a Cu–CeO 2–ScSZ composite anode for SOFCs running on ethanol fuel

Solid oxide fuel cells (SOFCs) that can operate directly on hydrocarbon fuels, without external reforming, have the potential of greatly speeding up the application of SOFCs for transportation and distributed-power supplies. In this paper, a dual tape casting method for fabricating an anode-supported thin-electrolyte (scandia stabilized zirconia (ScSZ)) film and SOFCs that are active for the oxidation of wet ethanol was presented. The fabrication method relies upon the inclusion of ammonium oxalate ((NH 4) 2C 2O 4·H 2O) pore formers in the anode green tape in order to produce a porous ScSZ matrix, which forms the anode after wet impregnation with aqueous solutions of Cu(NO 3) 2 and Ce(NO 3) 3, and firing. Anodes with different ratios of copper to ceria but with the same total loading were fabricated and measured. The performance characteristics for such cells were studied in both H 2 and C 2H 5OH + H 2O, for comparison, and the long-term performance of the cells in C 2H 5OH stream at 800 °C was also presented.

Direct Nitric Oxide Detection in Aqueous Solution by Copper(II) Fluorescein Complexes

A series of FL(n) (n = 1-5) ligands, where FL(n) is a fluorescein modified with a functionalized 8-aminoquinoline group as a copper-binding moiety, were synthesized, and the chemical and photophysical properties of the free ligands and their copper complexes were investigated. UV-visible spectroscopy revealed a 1:1 binding stoichiometry for the Cu(II) complexes of FL(1), FL(3), and FL(5) in pH 7.0 buffered aqueous solutions. The reactions of FL(2) or FL(4) with CuCl(2), however, appear to produce a mixture of 1:1 and 1:2 complexes, as suggested by Job's plots. These binding modes were modeled by the synthesis and X-ray crystal structure determination of Cu(II) complexes of 2-[(quinolin-8-ylamino)methyl]phenol (modL), employed as a surrogate of the FL(n) ligand family. Two kinds of crystals, [Cu(modL)(2)](BF(4))(2) and [Cu(2)(modL')(2)(CH(3)OH)](BF(4))(2) (modL' = 2-[(quinolin-8-ylamino)methyl]phenolate), were obtained. The structures suggest that one oxygen and two nitrogen atoms of the FL(n) ligands most likely bind to Cu(II). Introduction of nitric oxide (NO) to pH 7.0 buffered aqueous solutions of Cu(FL(n)) (1 microM CuCl(2) and 1 microM FL(n)) at 37 degrees C induces an increase in fluorescence. The fluorescence response of Cu(FL(n)) to NO is direct and specific, which is a significant improvement over commercially available small molecule-based probes that are capable of detecting NO only indirectly. The NO-triggered fluorescence increase of Cu(FL(5)) occurs by reduction of Cu(II) to Cu(I) with concomitant dissociation of the N-nitrosated fluorophore ligand from copper. Spectroscopic and product analyses of the reaction of the FL(5) copper complex with NO indicated that the N-nitrosated fluorescein ligand (FL(5)-NO) is the species responsible for fluorescence turn-on. Density functional theory (DFT) calculations of FL(5) versus FL(5)-NO reveal how N-nitrosation of the fluorophore ligand brings about the fluorescence increase. The copper-based probes described in the present work form the basis for real-time detection of nitric oxide production in living cells.

A new cyanobridged one-dimensional coordination polymer based on the octahedral rhenium cluster [Re6Se8(CN)6]4−: Synthesis and crystal structure of [{Cu(H2O)0.5(en)2} {Cu(en)2}Re6Se8(CN)6]·3H2O

The rhenium cluster complex [{Cu(H2O)0.5(en)2} {Cu(en)2} Re6Se8(CN)6]·3H2O has been obtained by the reaction of an aqueous solution of K4[Re6Se8(CN)6]·3.5H2O with an aqueous solution of Cu(en)2Cl2 using cross diffusion through a gel. The structure of the compound has been characterized by a single-crystal X-ray diffraction method (a = 10.690(3) A, b = 15.035(5) A, c = 25.847(8) A, V = 4154(2) A3, Z = 4, space group P212121, R = 0.0651). Cluster anions [Re6Se8(CN)6]4− in the complex are connected with Cu2+ cations by cyano bridges resulting in zigzag chains. Coordination environment of cations is completed by ethylenediamine molecules. Additionally each cluster anion is coordinated by one terminal fragment {Cu(H2O)0.5(en)2}.

Spectrophotometric determination of copper(II) in natural waters, vitamins and certified steel scrap samples using acetophenone-p-chlorophenylthiosemicarbazone

A very simple, highly sensitive and selective spectrophotometric procedure was developed for the determination of copper(II). It is based on the reaction at pH 4–9 between the synthesized acetophenone-p-chlorophenylthiosemicarbazone (A-p-ClPT) and Cu(II) forming a green complex, Cu(II):A-p-ClPT (1:2), that floats quantitatively with oleic acid (HOL) surfactant. It exhibits a constant and maximum absorbance at 600 nm in both aqueous and surfactant layers. Beer’s law is obeyed over the concentration range 0.25–6.35 mg l−1 with a detection limit of 0.021 mg l−1 for a standard aqueous solution of Cu(II) with a concentration of 3.82 mg l−1 (calculated on the basis of 3σ) and molar absorptivities of 5.5 × 103 and 1.3 × 104 mol l−1 cm−1 in aqueous and surfactant layers, respectively. Sandell’s sensitivity was calculated to be 0.244 μg cm−2 and the relative standard deviation (n = 9) was 0.19%. The different analytical parameters affecting the flotation and determination processes were examined. The proposed procedure has been successfully applied to the analysis of Cu(II) in natural waters, certified scrap steel samples and vitamin samples. The results obtained agree well with those samples analyzed by atomic absorption spectrometry (AAS). Moreover, the flotation mechanism is suggested based on some physical and chemical studies on the solid complexes isolated from aqueous and surfactant layers.