Metal Ions Zn Research Articles

Enhanced Retention of Chelating Reagents in Octadecylsilyl Silica Phase by Interaction with Residual Silanol Groups in Solid Phase Extraction of Divalent Metal Ions.

Solid-phase extraction (SPE) of divalent metal ions with a lipophilic and potentially divalent hexadentate chelating reagent (H2L), with which octadecylsilyl silica (ODS), was impregnated with was studied to gain more insight into and develop the potential of this methodology. This is the first time to demonstrate that this reagent as well as other common nitrogen-containing reagents were retained both by adsorption due to hydrogen bonding between nitrogen atoms of the reagent and residual silanol groups in the ODS phase and by simple distribution into the hydrophobic space. An appreciably large amount of this reagent could be retained by the adsorption mechanism even with a relatively thin loading solution. The divalent metal ions of Mn(2+), Co(2+) and Zn(2+) were extracted as 1:1 neutral complexes ([ML]), while Ni(2+) and Cu(2+) as ion-pairs of 1:1 cationic complex ([MHL](+)) with anion in SPE with H2L. The extractability and selectivity were substantially the same as that in liquid-liquid extraction.

Biosorption of Zn<sup>2+</sup> and Ni<sup>2+</sup>, Cu<sup>2+</sup> by Four Kinds of Active Microalgae

To investigate the affinity of the terrestrial microalgae to metal ions (Zn2+, Cu2+ and Ni2+) in aqueous solutions, four kinds of living algae (Oscillatoria, Botryococcus, Scenedesmus and Spirulina platensis Geitl, abbreviated as CZ, PTZ, SZ and LXZ) were chosen to biosorption experiment, and the mechanism of algae biosorption to metal ions were explored by fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Results show that four kinds of algae have a good affinity for Cu, Zn, the removal rate could reach more than 95%; while for Ni, compared with CZ, SZ and PTZ, the adsorption rate of LXZ is weak. The results of FTIR and SEM experiments revealed that the function groups such as carboxyl, hydroxyl, amino, sulfonic groups and so on are the main groups which played important role in the procedure of absorbing metal ions from water aqueous. Specific algae have different affinity to different metals which will be great helpful in the field of biosorption.

Application of CPE-FAAS Methodology for the Analysis of Trace Heavy Metals in Real Samples using Phenanthraquinone Monophenyl Thiosemicarbazone and Triton X-114

In the present study, a cloud point extraction method was used for the preconcentration and extraction of cadmium (II) and zinc (II) ions in different environmental samples. The zinc and cadmium ions formed hydrophobic complexes with phenanthraquinone monophenyl thiosemicarbazone (PPT). These complexes were extracted using Triton X-114 nonionic surfactant. The surfactant-rich phase was diluted with acidified methanol. Then, the concentrations of the metal ions were determined by FAAS. The experimental factors controlling the process of separation are investigated e.g., pH, complexing agent concentration, surfactant's concentration, temperature, and incubation time. The present CPE-FAAS procedure has been used to preconcentrate and determine Cd(II) and Zn(II) metal ions in natural water samples, drug samples and certified reference materials. The LODs for cadmium(II) and zinc(II) ions were 0.38 and 1.85 μg/L, respectively with a preconcentration factor of 100. The recovery % of the extracted Cd(II) and Zn(II), is greater than 90% and the relative standard deviation(RSD,%) is less than 5%.

A Fluorescent Hypochlorite Probe Built on 1,10-Phenanthroline Scaffold and its Ion Recognition Features.

In this study, the synthesis of 7-((Hydroxyimino)methyl)-1,10-phenanthroline-4-carbaldehyde oxime (1) in two steps starting from 4,7-dimethyl-1,10-phenanthroline (2) is reported. It is found that compound 1 can be used as a fluorogenic probe for the detection of hypochlorite ion in aqueous solution. NMR and mass spectral analysis indicate that probe 1 undergoes a chemical transformation through its oxime units upon treatment with hypochlorite, which results in a remarkable enhancement of the emission intensity. Also, metal ion recognition properties of probe 1 is investigated. It is noted that compound 1 is responsive to Zn(2+), Cd(2+), Ni(2+) and Cu(2+) metal ions, which reduced the emission intensity under identical conditions. Graphical Abstract The design, synthesis and properties of a new fluorescent hypochlorite probe is described. It is found that probe 1 immediately undergoes an oxidation reaction with NaClO through its oxime units in 0.1M Na2CO3-NaHCO3 buffer containing DMF (pH=9.0, 30:1v/v) at room temperature, which resulted in a remarkable enhancement of the emission intensity. It is noteworthy that this novel probe 1 is highly selective to hypochlorite ion when compared to some other ROS and anions. On the other hand, probe 1 also induces turn-off fluorogenic responses to metal ions such as Zn(2+), Cd(2+), Ni(2+) and Cu(2+) ions under identical conditions.

Characterization, adsorption, and electrokinetic properties of modified sepiolite

The metal ion adsorption and electrokinetic properties of sepiolite modified by 3-(trimetoxysilyl)propyl metaacrylate was studied. The characterization of modified sepiolite was made by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), scanning electron micrograph (SEM), and differential thermal analysis/thermogravimetry (DTA/TG). The adsorption behavior of Fe(III), Mn(II), Co(II), Zn(II), Cu(II), and Cd(II) metal ions on modified sepiolite from aqueous solutions was investigated as a function of equilibrium pH, temperature, and ionic strength. The adsorption experiments were carried out using a batch method. The initial and final concentrations of heavy metals were determined by means of atomic absorption spectrophotometry. The zeta potential of the modified sepiolite suspensions was measured as a function of metal ion concentration and equilibrium pH using a Zeta Meter 3.0. The results showed that the amount of adsorbed metal ions increased with solution pH, and that the modified sepiolite adsorbed Cu(II) and Mn(II) ions more than other metal ions. It was found that the temperature had an important effect on metal ion adsorption and that the adsorption process was endothermic in nature. Equilibrium isotherms for the adsorption of metal ions were measured experimentally. Results were analyzed by the Freundlich and Langmuir equations and determined the characteristic parameters for each adsorption isotherm. The isotherm data were reasonably well correlated by Langmuir isotherm. Maximum monolayer adsorption capacity of modified sepiolite for Cu(II), Mn(II), Zn(II), Fe(III), Co(II), and Cd(II) metal ions was calculated from 12.3 × 10−5, 11.7 × 10−5, 9.0 × 10−5, 8.2 × 10−5, 5.7 × 10−5, and 1.8 × 10−5 mol L−1, respectively. The affinity order of adsorption was Cu(II) > Mn(II) > Zn(II)–Fe(III) > Co(II) > Cd(II). The results indicate that modified sepiolite is good adsorbent for the removal of metal ions from aqueous solutions.

Synthesis, characterization and crystal structure determination of a new Zn(II) Schiff base complex derived from condensation of a new asymmetrical tripodal amine, 3-((4-aminobutyl)(pyridin-2-ylmethyl)amino)propan-1-ol and 2-hydroxy-3-methoxybenzaldehyde

A new tripodal amine, 3-((4-aminobutyl)(pyridin-2-ylmethyl)amino)propan-1-ol (HL) has been prepared. This has been used to synthesize a new Schiff base complex by template condensation with 2-hydroxy-3-methoxybenzaldehyde in the presence of Zn(II) metal ion in methanol. The complex has been characterized using spectroscopic methods and the crystal structure of [ZnL]BF4, L:3-((4-aminobutyl)(pyridin-2-ylmethyl)amino)propan-1-ol was confirmed by single crystal X-ray diffraction studies. Single crystal X-ray structure analysis showed that in the mononuclear Zn(II) complex, [ZnL]BF4 the Zn(II) ion is in a distorted square pyramidal environment.

Two sensors based on π-extended TTF: synthesis and high selectivity for copper(II)

Two novel donor-π-acceptor chemosensors, exTTF-DPA and exTTF-ADPA, based on π-extended tetrathiafulvalene (exTTF) and di(pyridine-2-ylmethyl)amine (DPA) were synthesized and used as optical and electrochemical chemosensors for copper(II). The results showed that they possess specific selectivity for copper(II) in the presence of other competing metal ions (Zn2+, Sn2+, Pb2+, Pd2+, Hg2+, Al3+, Fe3+, Ag+, Co2+, Ni2+) in acetonitrile. Upon the addition of Cu2+, the solution color changed from yellow to orange, the cyclic voltammograms changed dramatically and the fluorescence quenched completely.

Biochemical Characterization and Validation of a Catalytic Site of a Highly Thermostable Ts2631 Endolysin from the Thermus scotoductus Phage vB_Tsc2631.

Phage vB_Tsc2631 infects the extremophilic bacterium Thermus scotoductus MAT2631 and uses the Ts2631 endolysin for the release of its progeny. The Ts2631 endolysin is the first endolysin from thermophilic bacteriophage with an experimentally validated catalytic site. In silico analysis and computational modelling of the Ts2631 endolysin structure revealed a conserved Zn2+ binding site (His30, Tyr58, His131 and Cys139) similar to Zn2+ binding site of eukaryotic peptidoglycan recognition proteins (PGRPs). We have shown that the Ts2631 endolysin lytic activity is dependent on divalent metal ions (Zn2+ and Ca2+). The Ts2631 endolysin substitution variants H30N, Y58F, H131N and C139S dramatically lost their antimicrobial activity, providing evidence for the role of the aforementioned residues in the lytic activity of the enzyme. The enzyme has proven to be not only thermoresistant, retaining 64.8% of its initial activity after 2 h at 95°C, but also highly thermodynamically stable (Tm = 99.82°C, ΔHcal = 4.58 × 104 cal mol-1). Substitutions of histidine residues (H30N and H131N) and a cysteine residue (C139S) resulted in variants aggregating at temperatures ≥75°C, indicating a significant role of these residues in enzyme thermostability. The substrate spectrum of the Ts2631 endolysin included extremophiles of the genus Thermus but also Gram-negative mesophiles, such as Escherichia coli, Salmonella panama, Pseudomonas fluorescens and Serratia marcescens. The broad substrate spectrum and high thermostability of this endolysin makes it a good candidate for use as an antimicrobial agent to combat Gram-negative pathogens.

The Removal of Zn(II) Through Calix[4]Recorcinarene Derivative Based Polymer Inclusion Membrane From Aqueous Solution

In the present work, the transport of Zn(II) metal ion from an aqueous nitrate solution of different metal ions through a polymer inclusion membrane (PIM) containing calix[4]resorcinarene derivative used as a carrier were investigated. Zn(II)metal ion showing high permeability were transported through PIMs prepared from cellulose triacetate (CTA) as a polymeric support material and 2-NPOE as a plasticizer. Total Zn(II) concentration was determined with an Atomic Absorption Spectrometer (AAS) in the acceptor phase. The prepared PIM and supported liquid membrane (SLM) were characterized by using Scanning Electron Microscopy(SEM) and Atomic Force Microscopy (AFM) techniques. The effects of membrane composition, effects of type of plasticizer in the membrane, effects of carrier concentration, and the thickness of the membranes were examined in the facilitated transport experiments of Zn(II) ion through PIM. We compared the performance of SLM experiments under the optimum conditions identified by the PIM studies. Higher permeability coefficient values for Zn(II) was found for SLM, while lower values were ascertained for PIM. The kinetic parameters which have been calculated as the constant rate (k), permeability coefficient (P), flux (J) and diffusion coefficient (D).

Quantum chemical study of the photolysis mechanisms of sulfachloropyridazine and the influence of selected divalent metal ions

Sulfonamides have been found in aquatic environments. Degradation of sulfachloropyridazine (SCP) mainly proceeds through direct and indirect photolysis in the aquatic environment. However, the mechanisms underlying the triplet photolysis of SCP and the influence of metal ions on the photolysis mechanism have not yet been fully explained. In this study, we elucidated the triplet photolysis mechanisms of SCP and the effects of three selected metal ions (Zn2+, Ca2+, and Cu2+) on the SCP photolysis mechanisms using quantum chemical calculation. Optimization of molecular structures and reaction pathways analysis of SCP were carried out at the B3LYP/6-31+G(d,p) level of theory. Two minimum energy pathways were investigated in the triplet photolysis of SCP. In Step 2 of Path-I, the photolysis product of SCP is a sulfur dioxide extrusion product, (4-(3-chloro-6-iminopyridazine-1(6H)-yl)aniline). The estimated activation energies of Step 2 and Step 3 of Path-I were much higher than in Path-II. Therefore, Path-II was found as the lowest energy pathway to obtain the SCP photoproducts, and Step 2 of Path-II was confirmed as the rate-determining step (RDS) in the photolysis mechanism of SCP. For the RDS of Path-II, computations with the three metal ions complexes (IM1–Cu2+, IM1–Ca2+, and IM1–Zn2+) show that the metal ions Cu2+ and Ca2+ promote triplet-sensitized photolysis of SCP by reducing the activation energy of RDS of Path-II, whereas Zn2+ showed an inhibitory effect in photolysis of SCP by increasing the activation energy.

Photophysical and photochemical properties of novel metallophthalocyanines bearing 7-oxy-3-(m-methoxyphenyl)coumarin groups

Tetra-peripherally and non-peripherally 7-oxy-3-(m-methoxyphenyl)coumarin-substituted zinc(II) (4a and 5a), indium(III)acetate (4b and 5b) and magnesium(II) (4c and 5c) phthalocyanines were synthesized for the first time. These phthalocyanines were characterized by elemental analysis, FT-IR, 1H NMR, UV–vis spectroscopy and mass spectra. The novel phthalocyanines showed excellent solubility in general organic solvents, such as dichloromethane, chloroform, tetrahydrofuran (THF), N,N-dimethylformamide (DMF) and dimethylsulfoxide (DMSO). The photophysical and photochemical properties of these phthalocyanines were investigated in DMF. The effects of the central metal ions (Zn2+, Mg2+, In+3) and the position (peripheral or non-peripheral) of the substituents on the photophysical and photochemical parameters were reported for comparison. The singlet oxygen quantum yield values of novel phthalocyanines ranged from 0.29 to 0.82 in DMF. In this study, the fluorescence quenching behavior of the studied zinc(II) and magnesium(II) phthalocyanine complexes was also described by the addition of 1,4-benzoquinone.

Triphenylamine substituted dipyrrinato metal complexes: Synthesis, optical and electrochemical studies

A series of triphenylamine substituted dipyrrinato metal complexes (1–8) have been synthesized. The mononuclear type complexes 1–6 have Ni(II), Co(II), Pd(II), In(III), and Zn(II) metal ions in the core. The binuclear type complexes 7 and 8 have Zn(II) metal ion in the center. All the compounds (1–8) were characterized by HRMS, NMR, IR, UV–vis absorption, cyclic voltammetry and fluorescence techniques. The presence of large electron rich triphenylamine moiety at dipyrrin ligands affected the spectral properties of complexes. Except Co(II) complex, other metal complexes exhibited blue shifted absorption maxima in UV–vis studies. The In(III) and Zn(II) metal complexes 4–6 showed red shifted emission maxima in fluorescence compared to their corresponding phenyl analogues. Complexes 3–8 exhibited good Stokes shifts in the range of 4600 to 7000cm−1 with reduced quantum yields. Singlet state lifetimes of complexes 3–8 were in the range of 2 to 4ns; also the decrease in radiative decay constants kr and the increase in non-radiative decay constants knr were in line with the quantum yield data. CV studies of complexes 1–8 showed anodic shifts in the oxidation potentials, suggesting that meso-triphenylamine group has affected the electronic properties of complexes by making them difficult to oxidize.

Preliminary investigations on a polygalacturonase from Aspergillus fumigatus in Chinese Pu’er tea fermentation

Abstract Background Polygalacturonase is one kind of pectinases which hydrolyze the alpha-1,4 glycosidic bond between galacturonic acid residue. Polygalacturonase has been widely used in the fields of food, biofuel, and textile industries, in which thermostable polygalacturonase is often demanded at high temperatures of 50–60 °C. Herein, we reported a thermostable polygalacturonase producing from Aspergillus fumigatus isolated from the pile fermentation of Pu’er tea in China. Results The thermophilic polygalacturonase-producing strain was identified as A. fumigatus L45 on basis of its morphology, physicochemical properties, and 18S rDNA analysis. The crucial fermentation parameters affecting polygalacturonase activity were optimized by response surface methodology (RSM); the optimum fermentation parameters were the following: inoculums concentration of 0.07 % (v/v), fermentation time of 36 h, pH of 5.0, and temperature of 45 °C. Under the optimized conditions, the highest polygalacturonase activity of 359.1 ± 10.1 U/mL was obtained. The polygalacturonase showed good thermostability and pH stability. The enzyme was activated by metal ions Zn2+ and Mg2+, but inhibited by K+. However, Na+ and Ca2+ showed little effects on its activity. K m and V max values were estimated to be 35.0 mg/mL and 7.69 μmol/mL/min, respectively. Conclusions A polygalacturonase from A. fumigatus L45 was preliminarily investigated, the crucial fermentation parameters were optimized by RSM, and the properties of polygalacturonase was examined. The polygalacturonase showed good thermostability and pH stability, which suggested the enzyme has potential applications in the biofuel and textile industries.

Studies on Stability Constants of the Complexes of 2,3 - Dihydroxybenzal-dehyde and its Schiff Bases with Cu(II), Zn(II), Ni(II), Co(II), Cd(II) and Mg(II) Metal Ions in 50% (v/v) Water - Ethanol Mixture at 0.1M Ionic Strength

Studies on Stability Constants of the Complexes of 2,3 - Dihydroxybenzal-dehyde and its Schiff Bases with Cu(II), Zn(II), Ni(II), Co(II), Cd(II) and Mg(II) Metal Ions in 50% (v/v) Water - Ethanol Mixture at 0.1M Ionic Strength

Calprotectin Increases the Activity of the SaeRS Two Component System and Murine Mortality during Staphylococcus aureus Infections.

Calprotectin, the most abundant cytoplasmic protein in neutrophils, suppresses the growth of Staphylococcus aureus by sequestering the nutrient metal ions Zn and Mn. Here we show that calprotectin can also enhance the activity of the SaeRS two component system (TCS), a signaling system essential for production of over 20 virulence factors in S. aureus. The activity of the SaeRS TCS is repressed by certain divalent ions found in blood or neutrophil granules; however, the Zn bound-form of calprotectin relieves this repression. During staphylococcal encounter with murine neutrophils or staphylococcal infection of the murine peritoneal cavity, calprotectin increases the activity of the SaeRS TCS as well as the production of proinflammatory cytokines such as IL-1β and TNF-α, resulting in higher murine mortality. These results suggest that, under certain conditions, calprotectin can be exploited by S. aureus to increase bacterial virulence and host mortality.

ChemInform Abstract: Zn(II) and Cu(II) Complexes Containing Bioactive O,O‐Chelated Ligands: Homoleptic and Heteroleptic Metal‐Based Biomolecules

AbstractReview: 127 refs.

Syntheses and Crystal Structures of Three Metal‐Organic Frameworks Constructed from a C3‐Symmetrical Tricarboxylic Acid

AbstractThree coordination polymers were synthesized by solvothermal reaction of a C3‐symmetrical organic ligand and metal ions (Zn2+, Cd2+, Mn2+). Single‐crystal X‐ray diffraction studies revealed that the compounds consist of trinuclear secondary building blocks connected by the organic linkers to form two‐dimensional layers, which are packed together to form the final architectures, although they crystallized in the different space groups.

Synthesis, spectroscopic, coordination and biological activities of some transition metal complexes containing ONO tridentate Schiff base ligand

The main target of this paper is to get an interesting data for the preparation and characterizations of metal oxide (MO) nanoparticles using H2L Schiff base complexes as precursors through the thermal decomposition procedure. Five Schiff base complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) metal ions were synthesized from 2-[(2-hydroxy-naphthalen-1-ylmethylene)-amino]-benzoic acid new adduct (H2L). Theses complexes were characterized using infrared, electronic, mass and 1H NMR spectroscopic techniques. The elemental analysis data was confirmed that the stoichiometry of (metal:H2L) is 1:1 molar ratio. The molar conductance indicates that all of complexes are non electrolytic. The general chemical formulas of these complexes is [M(L)(NH3)]·nH2O. All complexes are tetrahedral geometry. The thermal decomposition behavior of H2L hydrated and anhydrous complexes has been discussed using thermogravimetric analysis (TG/DTG) and differential thermal analyses (DTA) under nitrogen atmosphere. The crystalline phases of the reaction products were checked using X-ray diffractometer (XRD) and scanning electron microscopy (SEM).

Cobalt(III) tetraaza-macrocyclic complexes as efficient catalyst for photoinduced hydrogen production in water: Theoretical investigation of the electronic structure of the reduced species and mechanistic insight

We recently reported a very efficient homogeneous system for visible-light driven hydrogen production in water based on the cobalt(III) tetraaza-macrocyclic complex [Co(CR)Cl2]+ (1) (CR=2,12-dimethyl-3,7,11,17-tetra-azabicyclo(11.3.1)-heptadeca-1(17),2,11,13,15-pentaene) as a noble metal-free catalyst, with [RuII(bpy)3]2+ (Ru) as photosensitizer and ascorbate/ascorbic acid (HA−/H2A) as a sacrificial electron donor and buffer (PhysChemChemPhys 2013, 15, 17544). This catalyst presents the particularity to achieve very high turnover numbers (TONs) (up to 1000) at pH 4.0 at a relative high concentration (0.1mM) generating a large amount of hydrogen and having a long term stability. A similar activity was observed for the aquo derivative [CoIII(CR)(H2O)2]3+ (2) due to substitution of chloro ligands by water molecule in water. In this work, the geometry and electronic structures of 2 and its analog [ZnII(CR)Cl]+ (3) derivative containing the redox innocent Zn(II) metal ion have been investigated by DFT calculations under various oxidation states. We also further studied the photocatalytic activity of this system and evaluated the influence of varying the relative concentration of the different components on the H2-evolving activity. Turnover numbers versus catalyst (TONCat) were found to be dependent on the catalyst concentration with the highest value of 1130 obtained at 0.05mM. Interestingly, the analogous nickel derivative, [NiII(CR)Cl2] (4), when tested under the same experimental conditions was found to be fully inactive for H2 production. Nanosecond transient absorption spectroscopy measurements have revealed that the first electron-transfer steps of the photocatalytic H2-evolution mechanism with the Ru/cobalt tetraaza/HA−/H2A system involve a reductive quenching of the excited state of the photosensitizer by ascorbate (kq=2.5×107M−1s−1) followed by an electron transfer from the reduced photosensitizer to the catalyst (ket=1.4×109M−1s−1). The reduced catalyst can then enter into the cycle of hydrogen evolution.

“Turn on/off” proton transfer based fluorescent sensor for selective detection of environmentally hazardous metal ions (Zn2+, Pb2+) in aqueous media

Sensing ability of fluorescence based chemosensor: Indole-7-carboxaldehyde (I7C) for environmentally hazardous metal ions (Xn+=Zn2+, Pb2+, Co2+, Ni2+, Cu2+, Cd2+, Cr3+, and Fe3+) has been investigated. Based on excited state proton transfer (ESPT) phenomenon, the sensing capability of I7C is verified experimentally (UV–vis, FTIR, NMR) and theoretically (DFT, TD-DFT) in aqueous media. Chemical hardness (η), electrophilicity (ω) and electronic chemical potentials (μ) confirm the selective reactivity of I7C (Nc and Nt conformers) in the presence of metal ions by the formation of (1:1) metal ion: I7C complex (MX, MX⁎). MX, MX⁎ are found to display excellent sensing capability for Zn2+ and Pb2+ ions. “Turn-On” response for Zn2+ is observed through the appearance of a new enhanced fluorescence at ~430nm. By strong blue emission I7C establishes its strong candidature as “blue emitter”. “Turn-Off” response is observed for Pb2+ through the quenching of the existing fluorescence peak.