Formation Of Cu Complexes Research Articles

Colorimetric determination of cysteine and copper based on the peroxidase-like activity of Prussian blue nanocubes.

Prussian blue nanocubes were synthesized via a hydrothermal method. Significantly, the redox couple Ni3+/Ni2+ provided rich oxidation and reduction reactions, which enhance catalytic activity. Furthermore, PBNCs mimic peroxidase activity which could oxidise colourless tetramethyl benzidine (TMB) to a blue colour (TMB+) in the presence of H2O2. Thus, it can be used as a colorimetric sensing platform for detecting cysteine and Cu2+. The addition of cysteine to a TMB + PBNCs sensing system decreases the intensity of the blue colour in the solution with a decrease in the absorption peak at 652 nm in the UV visible spectrum. Subsequently, the addition of Cu2+ into the TMB + PBNCs + Cys sensing system increases the intensity of the blue colour due to complex formation of Cu and cysteine. Therefore, the change in intensity of the blue colour of TMB is directly proportional to the concentration of Cys and Cu2+. As a result, this sensing system is highly sensitive and selective with an effective low detection limit of 0.002 mM for cysteine and 0.0181 mM for Cu2+. Furthermore, this method was applied to the detection of cysteine and copper in spiked real samples and gave satisfactory results.

Application of Ultrasound-assisted Cloud-point Extraction and Spectrophotometry for Preconcentration and Determination of Trace Amounts of Copper(II) in Beverages

A new method for preconcentration of trace Cu(II) in beverages before determination by spectrophotometry is presented. The method is based on the ternary complex formation of Cu(II) with Safranin T in presence of pyrogallol at pH 5.5 followed by its extraction into the micellar phase of Triton X-114. The ternary complex was monitored by spectrophotometry at 532 nm. Variables affecting extraction efficiency were evaluated and optimized. Under the optimal conditions, the detection limit was 0.6 µg/L in the range of 2–300 µg/L with sensitivity enhancement of 55 after preconcentration from 15 mL of the sample, and precision was in the range of 2.5–3.9%. The accuracy was verified by the analysis of two certified samples and recovery studies of the spiked samples. The intra- and inter-day precision varied in the ranges of 3.7–4.6 and 3.9–5.2%, respectively. The method was successfully applied to determination of trace Cu(II) in beverages.

H-point Standard Addition Method (HPSAM) for Simultaneous Spectrophotometric Determination of Cu(II) and Pd(II) by 1-(2-thiazolylazo)-2-naphthol (TAN) in Micellar Media

The H-point standard addition method (HPSAM) is proposed for the simultaneous determination of Cu(II) and Pd(II). It is a simple, selective, and sensitive, spectrophotometric method. The basis of this technique is the complex formation of Cu(II) and Pd(II) with 1-(2-thiazolylazo)-2-naphthol (TAN) at pH 2.2, and in the presence of sodium dodecyl sulfate (SDS) as a micellizing agent. The sensitivity and selectivity of the method improve in the presence of a micellar system and an acidic medium, respectively. Cu(II) and Pd(II) can be determined in the concentration ranges of 0.04-3.40 and 0.12-6.0 μg mL-1 with satisfactory accuracy and precision. The proposed method was used for the simultaneous determination of Cu(II) and Pd(II) in water and various synthetic alloy samples with different concentration ratios of Cu(II) and Pd(II) with good accuracy and precision.

Partitioning of metals in different binding phases of tropical estuarine sediments: importance of metal chemistry.

Distribution of metals in different binding phases of estuarine sediments provides chemically significant description of metal-sediment interactions. This study describes the influences of ligand field stabilization energy (LFSE), Jahn-Teller effect, and water exchange rate (k-w) on metal distribution in different binding phases of estuarine sediments. It was found that Cu had highest affinity for organic binding phases in the studied sediments followed by Ni and Pb. However, Pb showed strong association with Fe/Mn oxide phases followed by Ni and Cu. Faster k-w of Cu (II) (1 × 10(9) s(-1)) increased the rate of complex formation of Cu(2+) ion with ligand in the organic phases. The Cu-ligand (from organic phase) complexes gained extra stability by the Jahn-Teller effect. The combined effects of these two phenomena and high ionic potential increased the association of Cu with the organic phases of the sediments than Ni and Pb. The smaller ionic radii of Ni(2+) (0.72 Å) than Pb(2+) (1.20 Å) increase the stability of Ni-ligand complexes in the organic phase of the sediments. High LFSE of Ni(II) (compared with Pb(2+) ions) also make Ni-organic complexes increasingly stable than Pb. High k-w (7 × 10(9) s(-1)) of Pb did not help it to associate with organic phases in the sediments. The high concentration of Pb in the Fe/Mn oxyhydroxide binding phase was probably due to co-precipitation of Pb(2+) and Fe(3+). High surface area or site availability for Pb(2+) ion on Fe oxyhydroxide phase was probably responsible for the high concentration of Pb in Fe/Mn oxyhydroxide phase. Increasing concentrations of Cu in organic phases with the increasing Cu loading suggest that enough binding sites were available for Cu in the organic binding phases of the sediments. This study also describes the influence of nature of sedimentary organic carbon (terrestrial and marine derived OC) in controlling these metal distribution and speciation in marine sediment.

Selective recognition of d-tryptophan from d/l-tryptophan mixtures in the presence of Cu(II) by electropolymerized l-lysine film

Selective recognition of d-tryptophan (d-Trp) in the presence of Cu(II) was investigated at poly-l-lysine (p-l-Lys) film using electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). p-l-Lys film was immobilized on a glassy carbon electrode (GCE) by cyclic voltammetry between 0.0 and 1.9 V in 20 mM phosphate buffer solution (pH 8.6). After the p-l-Lys/GCE electrode was incubated with d-Trp solution containing Cu(II) ions, obvious enhancement of electron transfer resistance and decrease of voltammetric current could be observed. If d-Trp was replaced by l-tryptophan (l-Trp), there was no apparent resistance and current changes. Moreover, no resistance and current changes could be found in the absence of Cu(II). It may be due to the formation of Cu complex with l-lysine and d-tryptophan. Finally, this method was successfully applied to monitoring enantiomeric composition of the d-Trp and l-Trp mixtures.

Copper-containing polyvinyl alcohol composite systems: Preparation, characterization and biological activity

The present investigation reports, the complex formation of Cu(II) with polyvinyl alcohol (PVA) and the synthesis of PVA-stabilized Cu2O particles. This PVA–Cu2O composite has been prepared via chemical reduction method using PVA–Cu(II) complex as precursor. At first, Cu(II) ions were stabilized in PVA matrix via complex formation with OH groups; subsequently, this PVA–Cu(II) macromolecular complex as precursor reacted with ascorbic acid as reducing agent at pH=12 to prepare PVA–Cu2O composite. The products were characterized by FTIR, XRD, FE-SEM, HRTEM, Visible Spectroscopy and atomic absorption. In the following, the antibacterial properties of as-prepared composites were examined against Gram-positive (Bacillus thuringiensis) and Gram-negative bacteria (Escherichia coli), and the results showed excellent antibacterial activity of these materials.

Fluorescence, absorbance, and ion exchange: coupling analysis with water treatment for improved insight on copper complexation with natural organic matter

Groundwater high in dissolved organic carbon (DOC) was spiked with 0–120 μmol/L of copper(II) (Cu) at pH 4, 6, and 8 to observe changes in fluorescence and UV absorbance of natural organic matter (NOM). The groundwater had a fluorescence excitation–emission matrix (EEM) characteristic of humic-like substances. Addition of Cu to the groundwater resulted in fluorescence quenching of EEM peak intensity and increase in UV absorbance at 254nm (UVA254). Both fluorescence quenching and increase in UVA254 suggested the complex formation between Cu and NOM. Importantly, DOC measurements showed that physical loss of NOM did not play a measureable role in contributing to the observed fluorescence quenching and increase in UVA254, which supports the complex formation of Cu–NOM. The conditional stability constant for Cu–NOM was estimated using both fluorescence quenching and UVA254 increase at each pH and ranged from 4.26 to 5.77. As a follow up, anion exchange and cation exchange batch experiments were conducted using the groundwater spiked with 120 μmol/L Cu at pH 8 to gain insight on the behavior of Cu–NOM, and attempt to give physical meaning to the fluorescence quenching and UVA254 increase. The ion exchange results suggested the possibility of a neutral or partially negatively charged Cu–NOM complex. The significance of this work resides in the idea that fluorescence quenching and UV absorbance of NOM can be used as a tool to evaluate the co-removal of contaminants through water treatment processes.

Mixed ligand complex formation of 2-aminobenzamide with Cu(II) in the presence of some amino acids: Synthesis, structural, biological, pH-metric, spectrophotometric and thermodynamic studies

Mixed ligand Cu(II) complexes of 2-aminobenzamide (2AB) and amino acids viz., glycine (gly), l-alanine (ala), l-valine (val) and l-phenylalanine (phe) have been synthesised and characterized by various physico-chemical and spectral techniques. The calculated g-tensor values for Cu(II) complexes at 77K and 300K, show the distorted octahedral geometry which has been confirmed from the absorption studies. Consequently, the thermal studies illustrate that the loss of water and acetate molecules in the initial stage which are followed by the decomposition of organic residues. The powder X-ray diffraction and SEM analysis reflect that all the complexes have well-defined crystallinity nature with homogeneous morphology. The binding activities of CT DNA with CuAB complexes have been examined by absorption studies. Further, the oxidative cleavage interactions of 2-aminobenzamide and CuAB complexes with DNA were studied by gel electrophoresis method in H2O2 medium. Also, the complex formation of Cu(II) involving 2-aminobenzamide and amino acids were carried out by a combined pH-metric and spectrophotometric techniques in 50% (v/v) water-ethanol mixture at 300, 310, 320 and 330±0.1K with I=0.15moldm−3 (NaClO4). In solution, CuAB and CuAB2 species has been detected and the binding modes of 2-aminobenzamide and amino acids in both binary and mixed ligand complexes are same. The calculated stabilization value of ΔlogK, log X and log X′ indicates higher stabilities for the mixed ligand complexes rather than their binary species. The thermodynamic parameters like ΔG, ΔH and ΔS have been determined from temperature dependence of the stability constant. In vitro biological activities of 2-aminobenzamide, CuA and CuAB complexes show remarkable activities against some bacterial and fungal strains. The percentage distribution of various binary and mixed ligand species in solution at dissimilar pH intervals were also evaluated.

Mixed-Ligand Complex Formation of Cu (II) with 1,2-Diphenylethylenediamine as Primary Ligand and Amino Acids as Secondary Ligands

Mixed-Ligand Complex Formation of Cu (II) with 1,2-Diphenylethylenediamine as Primary Ligand and Amino Acids as Secondary Ligands

Electrochemical enantioselective recognition of tryptophane enantiomers based on chiral ligand exchange

Electrochemical enantioselective recognition of tryptophane (Trp) enantiomers in the presence of Cu(II) using l-cysteine (l-Cys) self-assembled gold electrode is described. The chiral recognition of Trp enantiomers was investigated via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and quartz crystal microbalance (QCM). Time dependencies of the enantioselective interaction for the l-Cys modified electrodes with Trp enantiomers solutions in the presence of Cu(II) were also studied. The results showed that l-Cys had stronger interaction with d-Trp than l-Trp in the presence of Cu(II), and the discrimination was caused by the selective formation of Cu complexes with l-Cys and Trp enantiomers relying on the principle of chiral ligand exchange. The structure of the Cu complexes was optimized by the hybrid density functional theory (DFT) method. And the enantiomeric composition of l- and d-Trp was monitored by measuring the current responses of the sample.

Anticlastogenic effect of aqueous extract from water yam (Dioscorea alata L.)

Dioscorea plants have been widely used as traditional medicine and food for health benefits. Several therapeutic properties such as anti-cough, anti-diabetic, anti-diarrhea, and anti-cancer have been reported. Although the steroidal saponins (such as diosgenin) account for some of Dioscorea’s activity, there is little information on the effective components. We have shown here that water yam (Dioscorea alata L.) aqueous extract (YAE) inhibited the H2O2-CuSO4 induced damage of calf thymus DNA, and protected cultured human lymphoblastoid cells from CuSO4-induced DNA damage. This aqueous extract exhibited a major absorption peak at 260 to 262 nm. Upon the addition of CuSO4, the absorption peak was shifted to 236 nm and it was sensitive to the divalent ion chelator EDTA. The aqueous extract of YAE was also capable of dissociating the complex formation of Cu (II) with tetramethyl murexide (a copper indicator). Thin layer chromatography indicated that it contains one major and several minor anisaldehyde-, sulfuric acid-reactive and highly polar compounds. Based on these findings, we suggest that water-soluble mucilaginous polysaccharides within YAE are likely the effective compounds/candidates, which carry copper-chelating activity, and protect DNA against H2O2-CuSO4 combination or CuSO4 alone. Key words: Water yam (Dioscorea alata L.), Fenton reaction, metal chelating activity, DNA damage protection, antioxidant.

Complex formation of nonsymmetric 1,2-diacylhydrazines with nonferrous metal ions

Complex formation of Cu(II), Co(II), Ni(II), and Zn(II) ions with nonsymmetric 1,2-diacylhydrazines (DAHs) in ammonia solutions was studied. [M(II): [DAH] ratios were found by equilibrium slope, isomolar series, and conductometric titration methods to be 1: 1 and 1: 2 for Cu(II), 2: 1 and 1: 1 for Co(II), 2: 1 and 1: 1 for Ni(II), and 1: 1 for Zn(II). Independent of the [M(II): [DAH] ratio, we have isolated only complexes of composition 1: 1 from ammonia solutions. The composition was confirmed by IR spectroscopy and elemental analyses. The solubility products of solid complexes of 1: 1 composition and the complex formation constants were calculated with considering the states of ligands and metal ions in ammonia solutions. The solubility products of the solid complexes were found to depend on the length of radical in DAHs.

UV Spectrophotometric Determination of Cu(II) in Synthetic Mixture and Water Samples

AbstractA new and novel UV spectrophotometric method has been developed for the determination Cu(II) in synthetic mixture and water samples. The method is based on complex formation of Cu(II) with cefixime immediately in 1,4‐dioxan‐distilled water medium at room temperature. The complex showed maximum absorption wavelength at 336 nm. Beer's law is obeyed in the concentration range of 1.015‐8.122 μg mL−1 (Linear regression: A = 1.59 × 10−3 + 1.305 × 10−1 C) with apparent molar absorptivity (8.29 × 103 L mol−1cm−1) and Sandell's sensitivity (0.008 μg/cm2/0.001 absorbance unit). The limits of detection and quantitation for the developed method are 3.19 × 10−2 and 9.65 × 10−2 μg mL−1, respectively. Interferences due to Mn(II), Ca(II), Mg(II), Cd(II), Al(III), Pb(II), Zn(II), Fe(II), Fe(III), Ni(II), Cr(III), Hg(II) and As(III) was investigated. Nine cations do not interfere in the determination of Cu(II). Proposed method was successfully applied to the determination of Cu(II) in synthetic mixture, sea and well water samples.

On diffusion of Cu in ZnO

An experimental study of Cu diffusion in bulk ZnO single crystals in the temperature range 1012–1220∘C is presented. Concentration profiles of substitutional Cu were determined by IR absorption at 5817cm-1. Our findings reveal that Cu in ZnO diffuses faster than previously reported [G. Müller, R. Helbig, J. Phys. Chem. Solids 32 (1971) 1971]. The discrepancy is tentatively explained by the formation of Cu complexes, which occurs at high Cu concentrations.

An effective route to montmorillonite intercalation with imidazole complexes: Experiment and theory

Intercalation of 1 H-imidazole (IM) and his derivative 2-phenylimidazole (2-PhIM) into the interlayer spaces of both natural Ca(II)-montmorillonite (Ca-MMT) and Cu(II)-montmorillonite (Cu-MMT) was carried out by two ways, solid-state intercalation and intercalation from solution. Only the presented solid-state intercalation gave required results. In situ formation of Cu complexes in the interlayer spaces of Cu(II)-MMT is not a feasible way to prepare required clay–coordination–intercalation compounds. The Cu complexes of IM and 2-PhIM have been synthesized separately and they were anchored on surface and edges of silicate layers, consequently they were not intercalated into the interlayer spaces of Ca-MMT. X-ray powder diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy were applied to characterize nanocomposites of mentioned above heterocyclic compounds and their Cu complexes with Ca-MMT and/or Cu-MMT. Infrared spectra of intercalation products indicating, that these compounds have been anchored only by non-bonding interactions into interlayer spaces. The experimental data are supported by calculated structure models using molecular dynamics simulations.

Complex formation of Cu(II), Ni(II), Zn(II), Co(II), and Cd(II) acetates with 3,3′,4,4′,5,5′-hexamethyldipyrrolylmethene

The reactions of complex formation of Cu(II), Co(II), Zn(II), Ni(II), and Cd(II) acetates with 3,3′,4,4′5,5′-hexamethyl-2,2′-dipyrrolylmethene (HL) in DMF were studied by the electronic spectroscopy and calorimetric titration methods at 298.15 K. The main products of the above reactions are [ML2] chelates. In the case of Cu and Ni salts, the process occurs through the spectrally recorded stage of formation of the heteroligand [ML(AcO)] complexes. The reaction with Cd acetate terminates at the stage of the heteroligand complex formation due to the large radius and decreasing electron affinity of the Cd2+ ion. The effect of the metal nature appears in the increasing thermodynamic stability of single-type complexes in the series [ML2]: Ni(II) < Zn(II) < Co(II) < Cu(II) and [ML(AcO)]: Cd(II) < Ni(II) < Cu(II).

Effect of copper complexation on the estrogenic activities of endocrine‐disrupting compounds using E‐screen bioassay

The complexation reaction between Cu and four targeted endocrine-disrupting compounds (EDCs)-17beta-estradiol (E2), 17alpha-ethynylestradiol (EE2), 4-octylphenol (OP), and bisphenol A (BPA)-was studied using the fluorescence quenching method, with the changed EDC forms evaluated for their estrogenic activities using an E-screen assay. The results of the E-screen showed no estrogenic activity of Cu, whereas results with the EDCs indicated high cell proliferation (decreasing order of induction: E2, EE2, OP, and BPA). The results of the fluorescence quenching response and FTIR (Fourier transformation infrared) strongly support the formation of Cu complexes on the -OH functional group of the targeted EDCs when Cu was spiked at concentrations between 10(-7) and 10(-4) M. The degree of complexation was in the following order: E2, EE2, OP, and BPA. The E-screen result for three of the EDCs, with the exception of BPA, was similar when estimating the effects of Cu on the estrogenic activities of the EDCs, which were significantly reduced at alpha = 0.05 with increasing Cu concentration. Consequently, the results of the complexation reaction and E-screen assay with the Cu-EDC mixtures indicated that Cu plays a significant role in the assessment of the estrogenic activities of EDCs in natural waters.

Synthesis and spectroscopic characterization of copper(H)-dextran complexes

Synthesis of stable copper(II) complexes with reduced dextran derivatives can be realized with low molar polysaccharides of an average molar mass 5000 g mol−1. A copper(II) content of 4–20% is achieved at pH 7–8 and at the boiling point. Copper(II) complex formation with dextran was analyzed by spectrophotometric VIS methods. The IR spectra of copper(II) complexes with dextran were analyzed to find the most stable conformation of the glucopyranose unit. The ESR parameters of the spectrum indicate a square-planar coordination of the Cu(II) ion with four oxygen ligand atoms in the same plane. Copper deficiency causes a number of pathological states [1]. In both human and veterinary medicine, commercial copper preparations based on dextran and its derivatives are used for such purposes [2]. According to the literature data, dextran has the ability of complex formation with various biometals (Zn, Fe, Co, Ca, and Mg) [3–6]. Iron complexes with different polysaccharides have special importance and they have been described in detail [7]. Synthetic procedures for the complex formation of Cu(II) with polysaccharides, including dextran, are described in scientific and patent literature [8]. However, literature data on the complex formation possibility of the Cu(II) ion with dextran derivatives are scarce.

Observation of the complex formation between Cu(II) and protein by capillary electrophoretic system incorporating an UV/CL dual detector

We investigated the complex formation between Cu(II) and human serum albumin (HSA) through a biuret reaction by use of capillary electrophoretic system incorporating an ultra-violet absorption (UV) and chemiluminescence (CL) dual detector. Cu(II)-tartrate complex and Cu(II)-human serum albumin complex were detected by UV detection (282 nm) with on-capillary, followed by CL detection (luminol-hydrogen peroxide CL reaction) with end-capillary. We examined the effects of the reaction time and temperature on the UV and CL responses. On the basis of the obtained results we considered the Cu(II)-human serum albumin complex formation processes and its catalytic activity for the CL reaction. The system easily, rapidly, and simultaneously produced useful information concerning the complex formation of Cu(II) and human serum albumin due to the presence of the both detectors.

DNA-Accelerated Atom Transfer Radical Polymerization on a Gold Surface

A significantly increased polymer growth rate was observed during a surface-initiated ATRP reaction in the presence of DNA molecules. To investigate this phenomenon, thiolated single-stranded DNA molecules (ssDNAs) with ATRP initiators coupled at the distal point were used as the model molecule in the study. In comparison, a small molecule, HS-(CH(2))(11)NHCOC(CH(3))(2)Br, was used to provide a less-polar surface coating for polymer grafting. 2-Hydroxyethyl methacrylate (HEMA) and monomethoxy-capped oligo(ethylene glycol) methacrylate (OEGMA) were used as the ATRP monomers. The polymer growth rates were monitored by measuring the thickness of the polymer films formed at different times. Our results show that the presence of DNA molecules, although at a less-than-1% surface coverage, significantly accelerated the growth rates of both poly(2-hydroxyethyl methacrylate) (PHEMA) and poly(oligoethylene glycol methacrylate) (POEGMA) at the beginning of the ATRP reactions. This accelerating effect was suspected to be a combined result of the highly charged sugar-phosphate backbones of DNA molecules and the formation of Cu complexes with DNA bases. After the initial polymer growth, a smaller yet constant polymer growth rate was observed, suggesting the reduced influence of DNA molecules as the ATRP reaction centers moved farther away from the surface. Similar to conventional ATRP reactions, the polymer growth from surface-anchored DNA molecules was found to be strongly dependent on the composition and the concentration of the catalysts used. Specifically, a catalyst mixture of CuCl/30% CuBr(2)/bpy with 23 mM CuCl was found to provide the optimal reaction condition to yield the fastest polymer film growth among the conditions tested.