Direct Electrochemical Determination of Glyphosate at Copper Phthalocyanine/Multiwalled Carbon Nanotube Film Electrodes

A copper phthalocyanine/multiwalled carbon nanotube film-modified glassy carbon electrode has been used for the determination of the herbicide glyphosate (Gly) at -50 mV vs. SCE by electrochemical oxidation using differential pulse voltamtnetry (DPV). Cyclic voltammetry and electrochemical impedance spectroscopy showed that Gly is adsorbed on the metallic centre of the copper phthalocyanine molecule, with formation of Gly-copper ion complexes. An analytical method was developed using DPV in pH 7.4 phosphate buffer solution, without any pretreatment steps: Gly was determined in the concentration range of 0.83-9.90 mu mol L(-1), with detection limit 12.2 nmol L(-1) (2.02 mu g L(-1))

A three-dimensional network constructed from the assembly of 1,3-diaminopropane-copper(II) and tetracyanopalladate(II) moieties

The coordination polymer [Cu(Pd(CN)(4))(pn)](n) (pn = 1,3-diaminopropane) has been synthesized and characterized by elemental analysis, infrared spectroscopy and single-crystal X-ray diffraction. The crystal structure showed that three cyano groups of each [Pd(CN)(4)] unit bridge Cu(II) centers leading to the formation of a three-dimensional network. A series of bifurcated hydrogen bonds between the amino groups of the diamine and the nonbridging cyano groups of the cyanometallate result in the organization of suprarnolecular chains and rings along the polymer. (c) 2008 Elsevier B.V. All rights reserved.

Investigating the Nature of Noble Gas-Copper Bonds by the Quantum Theory of Atoms in Molecules

We investigated noble gas copper bonds in linear complexes represented by the NgCuX general formula in which Ng and X stand for a noble gas (neon, argon, krypton, or xenon) and a halogen (fluorine, chlorine or bromine), respectively, by coupled cluster methods and modified cc-pVQZ basis sets. The quantum theory of atoms in molecules (QTAIM) shows a linear relation between the dissociation energy or noble gas-copper bonds and the amount of electronic charge transferred mainly from the noble gas to copper during complexation. Large changes in the QTAIM quadrupole moments of copper and noble gases resulting from this bonding and a comparison between NgCuX and NgNaCl systems indicate that these noble gas-copper bonds should be better interpreted as predominantly covalent. Finally, QTAIM atomic dipoles of noble gases in NgNaCl systems agree satisfactorily with atomic dipoles given by a simple model for these NgNa van der Waals bonds.

A novel nanostructured composite formed by interaction of copper octa(3-aminopropyl)octasilsesquioxane with azide ligands: Preparation, characterization and a voltammetric application

This study presents the preparation, characterization and application of copper octa(3-aminopropyl)octasilsesquioxane following its subsequent reaction with azide ions (ASCA). The precursor (AC) and the novel compound (ASCA) were characterized by Fourier transform infrared spectra (FTIR), nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), scanning electronic microscopy (SEM), X-ray diffraction (XRD), Thermogravimetric analyses and voltammetric technique. The cyclic voltammogram of the modified graphite paste electrode with ASCA (GPE-ASCA), showed one redox couple with formal potential (E(1/2)(ox)) = 0.30 V and an irreversible process at 1.1 V (vs. Ag/AgCl; NaCl 1.0 M; v = 20 mV s(-1)). The material is very sensitive to nitrite concentrations. The modified graphite paste electrode (GPE-ASCA) gives a linear range from 1.0 x 10(-4) to 4.0 x 10(-3) mol L(-1) for the determination of nitrite, with a detection limit of 2.1 x 10(-4) mol L(-1) and the amperometric sensitivity of 8.04 mA/mol L(-1). (C) 2010 Elsevier Ltd. All rights reserved.

Factors affecting nucleolytic efficiency of some ternary metal complexes with DNA binding and recognition domains. Crystal and molecular structure of Zn(phen)(edda)

The binding selectivity of the M(phen)(edda) (M = Cu, Co, Ni, Zn; phen = 1,10-phenanthroline, edda = ethylenediaminediacetic acid) complexes towards ds(CG)(6), ds(AT)(6) and ds(CGCGAATTCGCG) B-form oligonucleotide duplexes were studied by CD spectroscopy and molecular modeling. The binding mode is intercalation and there is selectivity towards AT-sequence and stacking preference for A/A parallel or diagonal adjacent base steps in their intercalation. The nucleolytic properties of these complexes were investigated and the factors affecting the extent of cleavage were determined to be: concentration of complex, the nature of metal(11) ion, type of buffer, pH of buffer, incubation time, incubation temperature, and the presence of hydrogen peroxide or ascorbic acid as exogenous reagents. The fluorescence property of these complexes and its origin were also investigated. The crystal structure of the Zn(phen)(edda) complex is reported in which the zinc atom displays a distorted trans-N4O2 octahedral geometry; the crystal packing features double layers of complex molecules held together by extensive hydrogen bonding that inter-digitate with adjacent double layers via pi...pi interactions between 1,10-phenanthroline residues. The structure is compared with that of the recently described copper(II) analogue and, with the latter, included in molecular modeling. (C) 2008 Elsevier B.V. All rights reserved.

Adsorption of Cu(II) and Co(II) complexes on a silica gel surface chemically modified with 2-mercaptoimidazole

The isotherms of adsorption of MeX2 (Me = Cu2+, Co2+; X = Cl-, Br-, ClO4-) by silica gel chemically modified with 2-mercaptoimidazole (SiMI) were studied in acetone and ethanol solutions, at 25 degrees C. Covalently attached 2-mercaptoimidazole molecule to silica gel surface adsorbs MeX2 from solvent by forming a surface complex. The metal is bonded to the surface through the nitrogen atom of attached 2-mercaptoimidazole. At low loading, the electronic and ESR spectral parameters indicated that the Cu2+ complexes are in a distorted-tetragonal symmetry field. The d-d electronic transition spectra showed that for Cu(ClO4)(2) complex, the peak of absorption did not change for any degree of metal loading and for Cl- and Br- complexes, the peak maxima shifted to higher energy with lower metal loading. The CoX2(X = Cl-, Br-, ClO4-) analogues possess a distorted-tetrahedral field.

A spectroelectrochemical study of the inhibition of the electrode process on copper by 2-mercaptobenzothiazole in ethanolic solutions

The effect of 2-mercaptobenzothiazole (MBT) on the corrosion of copper in ethanol-water mixture with 0.01 mol dm(-3) HClO4 was investigated by linear sweep voltammetry and surface enhanced Raman scattering spectroscopy. The linear sweep voltammetry for the copper electrode in the presence of MBT shows one anodic process associated with the oxidation of MBT, which leads to the formation of a film on the electrode. This film inhibits the anodic copper dissolution and cathodic hydrogen evolution reaction. SERS studies indicated that MBT oxidizes and forms polymeric complexes involving copper ions and the ionized form of thiol. (C) 1997 Elsevier B.V. Ltd.

Preparation and thermal decomposition of copper(II), zinc(II) and cadmium(II) chelates with 8-hydroxyquinoline

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis, characterization, and investigation of the thermal behavior of Cu(II) pyrazolyl complexes

This work reports the synthesis, characterization, and thermal behavior of three complexes of copper (II): [CuCl(2)(HPz)(4)] (1), [CuCl(2)(HdmPz)(4)] (2), and [CuCl(2)(HIPz)(4)] (3) (HPz = pyrazole; HdmPz = 3,5-dimethylpyrazole; HIPz = 4-iodopyrazole). The compounds were characterized by elemental analysis, infrared spectroscopy, and UV-Vis measurements. The thermal study of the compounds showed that the ligands are eliminated in 2-4 stages, yielding CuO as final residue.

An investigation of the thermal behavior of heterobimetallic species containing copper(II) and tetracyanopalladate(II)

Synthesis, characterization and thermal behavior of four compounds that have the general formula [Cu{Pd(CN)(4)}(L)(x)](n), in which en = 1,2-diaminoethane and pn = 1,3-diaminopropane (L = en, x = 1 (I); L = pn, x = 1 (II); L = en, x = 2 (III); L = pn, x = 2 (IV)) were described in this work. The complexes were studied by elemental analysis, infrared spectroscopy (IR), differential thermal analysis (DTA) and thermogravimetry (TG) and the residues of the thermal decomposition were characterized by X-ray powder diffraction and found as a mixture of CuO and PdO. The stoichiometry of the compounds was established via thermogravimetric and elemental analyses and their structures were proposed as coordination polymers based on their infrared spectra. The following thermal stability sequence was found: IV < I=II < III.

Synthesis, characterization and thermal behavior of complexes of Cu(II), Zn(II) and Cd(II) with S,S '-methylenebis(cysteine)

Synthesis and characterization, including data on thermal decomposition, are reported for the complexes of S,S'-methylenebis(cysteine) (djenkolic acid) with copper(II), zinc(II) and cadmium(II): CuC(7)H(12)N(2)O(4)S(2) [I]; ZnC(7)H(12)N(2)O(4)S(2) [II] and CdC(7)H(12)N(2)O(4)S(2) [III] X-ray diffraction showed that the compounds are isostructural and belong to a monoclinic system. According to IR spectra, COO, NH(2) groups and bridging sulfur atoms are the main coordination sites.

A Chloro-Bridged Linear Chain Imine-Copper(II) Complex and Its Application as an Enzyme-Free Amperometric Biosensor for Hydrogen Peroxide

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Dinuclear Azide-Bridged Copper(II) Complex as Building Block for the Assembly of a 2D-Supramolecular Array

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A description of ligand field effects in the Di-μ-Azido-Bis [{Azido(N,N-diethylethylenediamine)}Copper(II)] compound by the simple overlap model

We present a theoretical description of ligand field effects in the di-μ-azido- bis[{azido(N,N-diethylethylenediamine)} copper(II)] compound by the Simple Overlap Model. The ligand field Hamiltonian is expressed in terms of irreducible tensor operators for an assumed D3h site symmetry occupied by the copper ion. The ligand field parameters, calculated from the available structural data, indicate that the copper ion is under the influence of a very strong ligand field. The energy of the d-d absorption band is well reproduced phenomenologically by the model.

Lead- and copper-complexing extracellular ligands released by Kirchneriella aperta (Chloroccocales, Chlorophyta)

The freshwater planktonic alga Kirchneriella aperta was grown in batch cultures to stationary growth phase. Copper and lead complexation properties of the exudate from stationary and exponential growth phases were determined by titrations monitored by ion-selective electrodes. Molecular weight fractionation dialysis) and analysis of the titration data (Scatchard Plot) revealed that K. aperta releases metal-complexing ligands. Copper is associated with low and high molecular weight compounds, whereas lead forms complexes with only high molecular weight compounds. Gas-liquid chromatography showed that mannose and rhamnose make up 74% of the total high molecular weight organic material, with uronic acids present at 19%.