0-D and 1-D inorganic-organic composite polyoxotungstates constructed from in-situ generated monocopper-substituted Keggin polyoxoanions and copper-organoamine complexes

Combination of in-situ generated monocopper^II-substituted Keggin polyoxoanions with copper^II-organoamine complexes under hydrothermal conditions results in seven inorganic-organic composite polyoxotungstates [Cu(en)₂(H₂O)]₂{[Cu(en)₂][α-PCuW₁₁O₃₉Cl]}·3H₂O (1), {[Cu(en)₂(H₂O)][Cu(en)₂]₂[α-PCuW₁₁O₃₉Cl]}·6H₂O (2), {[Cu(en)₂(H₂O)]₂[Cu(en)₂][α-XCuW₁₁O₃₉]}·5H₂O (3/4, X=Si^IV/Ge^IV), {[Cu(deta)(H₂O)₂]₂[Cu(deta)(H₂O)][α-XCuW₁₁O₃₉]}·5H₂O (5/6, X=Ge^IV/Si^IV) and [Cu(dap)₂]₂{[Cu(dap)₂]₂[Cu(dap)₂][α-PCuW₁₁O₃₉]₂} (7) (en=ethylenediamine, dap=1,2-diaminopropane and deta=diethylenetriamine). 1 is an isolated structure whereas 2 is a 1-D chain structure, but both contain [α-PCuW₁₁O₃₉Cl]⁶⁻ polyoxoanions. 3-6 contain the 1-D linear chains made up of [α-XCuW₁₁O₃₉]⁶⁻ polyoxoanions in the pattern of -A-A-A- (A=[α-XCuW₁₁O₃₉]⁶⁻), while 7 demonstrates the first 1-D zigzag chain constructed from [α-PCuW₁₁O₃₉]₂¹⁰⁻ polyoxoanions via [Cu(en)₂]²⁺ bridges in the pattern of -A-B-A-B- (A=[α-PCuW₁₁O₃₉]₂¹⁰⁻, B=[Cu(en)₂]²⁺). The successful syntheses of 1-7 can provide some experimental evidences that di-/tri-/hexa-vacant polyoxoanions can be transformed into mono-vacant Keggin polyoxoanions under hydrothermal conditions.     

Co(II) and Cu(II) Schiff base complexes of bis(<Emphasis Type="Italic">N</Emphasis>-(4-diethylamino-2-methylphenyl)-3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butylsalicylaldimine): Electrochemical and X-ray structural study

Copper(II) and cobalt(II) complexes of salicylaldimine obtained by the condensation of N,N-diethyl-2-methyl-1,4-phenylenediamine with 3,5-di-tert-butyl-2-hydroxybenzaldehyde have been synthesized and characterized by elemental analyses, magnetic susceptibility measurements, cyclic voltammetry, and FT-IR and UV–Vis spectroscopy. The molecular structure of the title copper(II) complex was determined by the single crystal X-ray diffraction technique. The Cu(II) center is coordinated by four atoms of the donor set in a compressed tetrahedral trans-[N₂O₂] environment, which can be essentially ascribed to the presence of bulky fragments of the ligand. The computed bond valences of the copper verify +2 oxidation state and indicate that the copper bonds, in particular Cu–N bonds, are elongated due to steric effects from bulky substituents in the ligands, N-(4-diethylamino-2-methylphenyl). Intermolecular C–H···π interactions leading to centrosymmetric synthons serve to stabilize periodic organization of the molecules.     

An integrated experimental and theoretical investigation of the vibrational modes and molecular structure of a new Cu(II)–phosphocreatine complex

A new complex of Cu(II) of stoichiometry [Cu(PCr)(H₂O)] was prepared from aqueous solution at pH 6. Its synthesis, characterization, thermogravimetric, vibrational spectroscopy, and electron paramagnetic resonance analyses were described and suggest that phosphocreatine (PCr) in solid state is acting as a tridentate ligand (the nitrogen atom of the guanidine group and the oxygen atoms of the phosphate group and the carboxylate group being the donor atoms). The fourth position is occupied by a water molecule. These results were confirmed through computational calculations (DFT/B3LYP:6-311G theoretical procedure). The tetra coordination of Cu(II) arranged in a quadratic planar geometry was found to be more stable in the DFT calculations. The calculated vibrational spectrum agrees well with the FT-IR experimental spectrum.     

A New 1D Chain-like Complex Built Up of Cu-containing Sandwich Tungstogermanate

Two new tungstogermanates K₂Na₁₀[Cu₄(GeW₉O₃₄)₂] · 15.5H₂O (1) and K₄Na₆[Cu_3.5W_0.5(H₂O)₂(GeW₉O₃₄)₂] · 17H₂O (2) have been obtained by the conventional aqueous solution methods and characterized by IR, element analysis, electrochemistry and single-crystal X-ray analysis. Compound 1 is composed of the [Cu₄(GeW₉O₃₄)₂]¹²⁻ anions linked by two equivalent bonds of Cu–O–W, representing the first one-dimensional chain-like structure based on sandwich-type polyoxometalates by direct condensation to form oxo-bridged arrays of clusters. Compound 2 is a sandwich structure, consisting of two trivacant [GeW₉O₃₄]¹⁰⁻ units linked by a [Cu_3.5W_0.5(H₂O)₂] cluster, and the anions are linked by the K⁺ and Na⁺ to form a three-dimensional structure. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

碳纳米管化学修饰电极测定土壤沉积物中的铜

本文研究了在碳纳米管(CNT)修饰的玻碳电极上,用微分脉冲溶出伏安法(DPSV)对土壤沉积物中铜的测定方法,在1.0mol/L的HCl介质中,于-0.6V电位处富集240s,静置10s,在阳极扫描过程中,被富集于修饰电极表面的铜在约-0.25V电位处出现特定的溶出峰,据此实现铜离子的测定。该方法的线性范围为8.0×10-7～1.2×10-5mol/L,检出限为2.0×10-7mol/L,结果令人满意     

铜(Ⅱ)催化过氧化氢氧化5-Cl-PADAT褪色反应的动力学研究及其应用

在KH2PO4 NaOH介质中研究了铜(Ⅱ)催化H2O2氧化5 Cl PADAT的褪色反应,测定了反应动力学参数,并建立了测定痕量铜的新方法。本法检出限为6.25×10-11g mL,铜(Ⅱ)的质量浓度在0～2.24ng mL范围内与log(A0 A)呈良好的线性关系。该法已用于核桃、人发样中痕量铜的测定。     

在仲丁醇脱氢反应中负载型铜催化剂的研究

采用浸渍法制备Cu/SiO₂和Cu-ZnO/SiO₂催化剂.研究了活性物种Cu和助剂ZnO的担载量对催化剂的结构和性能的影响,同时考察该催化剂对仲丁醇脱氢活性和选择性的影响.借助XRD和TPR对催化剂进行了表征,结果表明,高分散的Cu⁰为反应的活性中心,ZnO起到分散和稳定铜物种的作用.铜-锌之间的某种相互作用导致了缩合产物增加.     

Determination of copper in medicinal plants used as dietary supplements by atomic absorption spectrometry with direct flame solid analysis

An alternative device for the direct solid analysis (DSA) for copper determination by flame atomic absorption spectrometry (FAAS) is proposed. Copper was directly determined in commercial medicinal plants used as dietary supplements. The determination of copper in solid samples by DSA–FAAS was made by using a conventional air–acetylene flame. Between 0.05 and 1.5 mg of each test, sample was weighed directly into a small polyethylene vial connected to the device used for solid introduction into the flame. Test samples were introduced into the flame as a dry aerosol using a T-quartz cell set between the burner and the optical path. The T-quartz cell has a slit in the superior part by which the solid aerosol passes to the flame. A transient signal, evaluated as integrated absorbance, is produced and it is totally integrated in 2 s. Background signals always presented absorbance values less than 0.1. It was found a characteristic mass of 0.8 ng Cu and absolute limit of detection of 1.2 ng (3 s), or 1.2 μg g⁻¹ if a sample mass of 1 mg was used. Optimized conditions for air flow rate, flame stoichiometry, and so on were established as well. No excessive grinding of the samples was needed and samples with particle of size less than 80 μm were used throughout. No statistical difference between the results from the proposed system and those obtained by sample digestion and determination by conventional FAAS was observed. With the proposed procedure, more than 50 test samples can be analyzed in 1 h and it can be easily adapted to conventional spectrometers for FAAS.     

Lewis-Base Adducts of Group 11 Metal(I) Compounds. LXXVI Structural Studies in the Copper(I) Halide : Norbornadiene System

The structural characterizations of some copper(I) halide (CuX) adducts with norbornadiene (nbd) are recorded. CuCl : nbd (1:1)₄ (a redetermination), (2:1)_2(|), are systems both based around Cu₄Cl₄ cubane-type cluster arrays. CuBr : nbd (7:3)_(|)( 0.5 MeOH), a complex polymer with 3-symmetry, is believed to be the complex previously described as an adduct of 2:1 stoichiometry. Attempts to obtain an iodide counterpart have resulted in the definition of an ephemeral adduct CuI : MeCN (3:2)_(|). 0.5 C₇H₈ in which, remarkably, the nbd is uncoordinated; the complex is a polymer, related to the [AgX(quinoline)]_(|) (X = Cl, Br) saddle polymer.     

Simultaneous determination of copper and lead in ethanol fuel by anodic stripping voltammetry

The presence of trace metals in car fuels plays an important role in the engine maintenance. In addition, these metals contribute for the environmental contamination in big cities and their control is necessary. Square Wave Stripping Voltammetry (SWSV) is a very sensitive technique for elemental trace determination and was applied for ethanol fuel analysis. The first studies were done searching for the best conditions for copper determination in alcoholic medium, utilizing gold electrodes. During these studies, the possibility of the simultaneous determination of copper and lead in the same experiment was observed. Two procedures for the analysis of these metals were adopted: The direct quantification of metals in alcohol–water mixtures and a second way that involves the evaporation of the organic solvent and re-suspension of the ions with water+electrolyte. Good recovery values were obtained for synthetic samples spiked with known amounts of metals. The results obtained for the two methods were in good agreement. The detection limits for copper and lead in 75% ethanol–water ratio solution were calculated as 120 and 235 ng l⁻¹, respectively, for 15-min deposition time.