Extraction of Cu<Superscript>2+</Superscript>, Zn<Superscript>2+</Superscript>, and Co<Superscript>2+</Superscript> ions from aqueous solutions with calcium and magnesium phosphates

The efficiency of calcium and magnesium phosphates of different compositions in the extraction of Cu²⁺, Zn², and Co²⁺ ions from aqueous solutions was studied.     

Thermodynamics of citrate complexation with Mn<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> ions

Isothermal titration calorimetry has been used to determine the stoichiometry, formation constants and thermodynamic parameters (ΔG ^o, ΔH, ΔS) for the formation of the citrate complexes with the Mn²⁺, Co²⁺, Ni²⁺ and Zn²⁺ ions. The measurements were run in Cacodylate, Pipes and Mes buffer solutions with a pH of 6, at 298.15 K. A constant ionic strength of 100 mM was maintained with NaClO₄. The influence of a metal ion on its interaction energy with the citrate ions and the stability of the resulting complexes have been discussed.     

Specific features of absorption of Cu<Superscript>2+</Superscript>, Zn<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, and Pb<Superscript>2+</Superscript> cations from aqueous solutions by calcium phosphates

Kinetic characteristics of the interaction of trisubstituted calcium phosphate Ca₃(PO₄)₂ · xH₂O with Cu²⁺, Zn²⁺, Co²⁺, and Pb²⁺ ions in aqueous solutions were studied.     

Extraction of metal ions (Fe<Superscript>3+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript>, Cu<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript>) using immobilized-polysiloxane iminobis(n-2-aminophenylacetamide) ligand system

A new insoluble solid functionalized ligand system bearing chelating ligand group of the general formula P-(CH₂)₃-N[CH₂CONH(C₆H₄)NH₂]₂, where P represents [Si–O] _n polysiloxane network, was prepared by the reaction of the immobilized diethyliminodiacetate polysiloxane ligand system, P-(CH₂)₃N(CH₂CO₂Et)₂ with 1,2-diaminobenzene in toluene. ¹³C CP-MAS NMR, XPS and FTIR results showed that most ethylacetate groups (–COOEt) were converted into the amide groups (–N–C=O). The new functionalized ligand system exhibits high capacity for extraction and removal of the metal ions (Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺) with efficiency of 95–97% after recovery from its primary metal complexes. This functionalized ligand system formed 1:1 metal to ligand complexes.     

Thermodynamic characteristics of formation reactions of Zn<Superscript>2+</Superscript> and Ni<Superscript>2+</Superscript> complexes with succinic acid in aqueous solutions

The heat effects of complex formation between zinc(II) and nickel(II) ions and succinic acid were determined calorimetrically at 298.15 K and several ionic strength values against the background of NaNO₃. The standard thermodynamic characteristics of complex formation in aqueous solution were calculated.     

Interaction of the Ni<Superscript>2+</Superscript> ion with citric acid in an aqueous solution

The formation of nickel citrate complexes was studied at ionic strength values of 0.1 and 0.3 mol/l (Et₄NCl) and 298.15 K by potentiometric titration. The NiCit^?, NiHCit, and NiH₂Cit⁺ complexes were formed in a Ni²⁺ ion-citric acid (H₃Cit) system. The thermodynamic formation constants of the nickel(II) citrate complexes were calculated in an aqueous solution at \(I = 0:\log \beta _{NiCit^ - }^0 \) = 6.86 ± 0.12 (Ni²⁺ + Cit^3? ai NiCit^?), logK ₁ ⁰ = 4.18 ± 0.10 (Ni²⁺ + HCit^2? ai NiHCit), and logK ₂ ⁰ = 2.24 ± 0.11 (Ni²⁺ + H₂Cit^? ai NiH₂Cit⁺). The spectral properties of the Ni²⁺-H₃Cit system were studied by spectrometry. The conditions of calorimetric determination of the thermal effects of formation of the nickel citrate complexes in an aqueous solution were optimized on the basis of the calculated stability constants of the Ni(II) complexes with H₃Cit.     

Thermodynamics of L-valine complex formation with Cu<Superscript>2+</Superscript> ions in an aqueous solution

Heat effects of mixing of aqueous solutions of Cu(NO₃)₂ and L-valine were measured by the calorimetric method at 298.15 K and a ionic strength of 0.5–1.5 (KNO₃). The standard heat effects of formation of the Cu(II) complexes with L-valine in an aqueous solution were obtained by the extrapolation to the zero ionic strength using the equation with one individual parameter. The standard thermodynamic characteristics of complex formation in the Cu²⁺-L-valine system were calculated.     

Crystal structures of a family of layered coordination polymers containing divalent metal ions (Mn<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript>) and the 3-amino 4-methyl benzoate ion

The syntheses and crystal structures of the layered coordination polymers M(C₈H₈NO₂)₂ [M = Mn (1), Co (2), Ni (3) and Zn (4)] are described. These isostructural compounds contain centrosymmetric trans-MN₂O₄ octahedra as parts of infinite sheets; the ligand bonds to three adjacent metal ions in μ³-N,O,O′ mode from both its carboxylate O atoms and its amine N atom. In each case, weak intra-sheet N–H?O and C–H?O hydrogen bonds may help to consolidate the structure. Crystal data: 1, C₁₆H₁₆MnN₂O₄, M _r = 355.25, monoclinic, P2₁/c (No. 14), a = 10.6534(2) Å, b = 4.3990(1) Å, c = 15.5733(5) Å, β = 95.1827(10)°, V = 726.85(3) ų, Z = 2, R(F) = 0.026, wR(F ²) = 0.067. 2, C₁₆H₁₆CoN₂O₄, M _r = 359.24, monoclinic, P2₁/c (No. 14), a = 10.6131(10) Å, b = 4.3374(4) Å, c = 15.3556(17) Å, β = 95.473(4)°, V = 703.65(12) ų, Z = 2, R(F) = 0.041, wR(F ²) = 0.091. 3, C₁₆H₁₆N₂NiO₄, M _r = 359.02, monoclinic, P2₁/c (No. 14), a = 10.6374(4) Å, b = 4.2964(2) Å, c = 15.2827(8) Å, β = 95.9744(14)°, V = 694.66(6) ų, Z = 2, R(F) = 0.028, wR(F ²) = 0.070. 4, C₁₆H₁₆N₂O₄Zn, M _r = 365.68, monoclinic, P2₁/c (No. 14), a = 10.6385(5) Å, b = 4.2967(3) Å, c = 15.2844(8) Å, β = 95.941(3)°, V = 694.89(7) ų, Z = 2, R(F) = 0.038, wR(F ²) = 0.107.     

Incorporation of Mg<Superscript>2+</Superscript>, Sr<Superscript>2+</Superscript>, Ba<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> into aragonite and comparison with calcite

We have investigated the presence of foreign ions into the bulk structure and the external surfaces of aragonite using periodic ab-initio methods. Four cations isovalent to Ca²⁺ were studied: Mg²⁺, Sr²⁺, Ba²⁺ and Zn²⁺. The calculations were performed at structures (bulk, surface) that contain four and eight CaCO₃ units. Our results, at the Hartree-Fock level, show that the incorporation of those ions into aragonite depends strongly on their size. Mg²⁺ and Zn²⁺, due to their smaller size, can substitute Ca²⁺ ions in the crystal lattice while the incorporation of Sr²⁺ and Ba²⁺ into aragonite is energetically less favoured. Examination of the [011], [110] and [001] surfaces of aragonite revealed that the surface incorporation reduces the energetic cost for the larger ions. These systems provide challenging examples for most shape analysis methods applied in Mathematical Chemistry.     

The thermodynamic characteristics of formation of Zn<Superscript>2+</Superscript> complexes with D,L-tryptophan in aqueous solution

The heat effects of formation of D,L-tryptophan complexes with doubly charged zinc ions were determined calorimetrically. The heat effects of interaction of amino acid solutions with a solution of Zn(II) were measured at 288.15, 298.15, and 308.15 K and ionic strengths of 0.25, 0.50, and 0.75 against the background of KNO₃. The heats of dilution of solutions of zinc nitrate with solutions of the background electrolyte were determined under the same conditions. The corresponding corrections were introduced. The thermochemical data were processed taking into account step equilibria. Along with complex formation, “side” protolytic processes were included. The standard thermodynamic characteristics of complex formation were calculated. The influence of temperature on the heat effects of complex formation in the β-alanine-zinc(II) ions system was considered.     

Thermochemistry of complex formation of Ni<Superscript>2+</Superscript> with glycyl-L-asparagine in aqueous solutions

The heats of formation of complexes in the glycyl-L-asparagine—Ni²⁺ system were determined by calorimetry in an aqueous solution at ionic strengths of 0.5, 1.0, and 1.5 (KNO₃) and a temperature of 298.15 K. The thermodynamic characteristics of the formation of nickel complexes with dipeptide were determined. The influence of the ligand structure on the complexation thermodynamics in solutions was discussed.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 2, 2005, pp. 143–148.Original Russian Text Copyright © 2005 by Zelenin, Kochergina.     

Sorption of Cu<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> by Natural Biomaterial: Duck Feather

Feather fibers were modified by treatment with 5% tannic acid (TA) solution. Kinetics of the modification was investigated as a function of the reaction time. The maximum loading of TA on feather reached 8.3% after being treated by TA for 9 h. The adsorption of metal cations (Cu²⁺, Zn²⁺) by unmodified and TA-modified feather fibers was investigated as a function of fiber weight gain, temperature, and pH of the metal solution. The adsorption was enhanced at alkaline pH and ambient temperature and increased with the weight gain of TA. The maximum uptake of metal cations (Cu²⁺, 0.77 mmol/g; Zn²⁺, 0.95 mmol/g) was obtained by TA-modified feather at weight gain: 8.3%, pH 11, while at the acidic pH, the adsorption of metal cations by either unmodified or TA-modified feather was negligible. The influence of anions on the adsorption of metal cations was also studied. The uptake of Cu²⁺ from chloride was higher and faster than that from nitrate. Desorption of the metals was performed at acidic pH 2.5 for 48 h. The feather–TA–metal complexes exhibited higher stability for metal cations than the feather–metal complexes. All these experiments reveal that TA-modified feather fibers have good adsorption to metal cations and can be used as metal adsorbent in wastewater treatment.     

Thermodynamic characteristics of Cu<Superscript>2+</Superscript> complexation processes with L-phenylalanine in an aqueous solution

The heats of interaction of Cu²⁺ ions with L-phenylalanine in aqueous solution were determined by calorimetry at ionic strengths of 0.50, 0.75, 1.00 (KNO₃) and a temperature of 298.15 K. The results of thermochemical study were interpreted taken into account complexation reactions, protolytic processes, and complexation with the competing ligand (OH^?) taking place in parallel. The effect of supporting electrolyte concentration on the heats of Cu²⁺ complexation with the amino acid was considered. The standard enthalpies of complexation were found by extrapolation to zero ionic strength. The standard enthalpies of formation of complex species in an aqueous solution were calculated.     

Thermodynamics of resolvation of Mg<Superscript>2+</Superscript>, Ca<Superscript>2+</Superscript>, Cd<Superscript>2+</Superscript>, and Cu<Superscript>2+</Superscript> ions in aqueous-ethanol mixtures on the basis of volta potential difference method

The volta potential difference method at 298.15 K was used to determine the real primary medium effect for magnesium, calcium, cadmium, and copper ions, and also the real Gibbs transfer energy of these ions from water into a mixed water ethanol (EtOH) solution. The surface potential value at the nonaqueous solution/gas phase interface $ \Delta \chi _{H_2 O}^{EtOH} $ \Delta \chi _{H_2 O}^{EtOH} was obtained. With account for this value, chemical thermodynamic characteristics of the studied ions in the water-ethanol solvent were calculated and the effect of composition and nature of the mixed solvent on the values obtained was analyzed. The dependence of variation in the thermodynamic characteristics of cation resolvation was established on their crystallographic radius that corresponds to the following sequence: Ca²⁺ < Cd²⁺ < Cu²⁺ < Mg²⁺.     

Thermodynamic behavior of complexation of 18-crown-6 with Tl<Superscript>+</Superscript>, Pb<Superscript>2+</Superscript>, Hg<Superscript>2+</Superscript>, and Zn<Superscript>2+</Superscript> metal cations in methanol-water binary media

The equilibrium constants and thermodynamic parameters for complex formation of 18-Crown-6 (18C6) with Tl⁺, Pb²⁺, Hg²⁺, and Zn²⁺ metal cations have been determined by conductivity measurements in methanol (MeOH)-water (H₂O) binary solutions. 18-Crown-6 forms 1:1 complexes with Hg²⁺ and Zn²⁺ cations, but in the case of Tl⁺ and Pb²⁺ cations, in addition to 1:1 stoichiometry, 1:2 (ML₂) complexes are formed in some binary solvents. The thermodynamic parameters (ΔH _c⁰ and ΔS _c⁰), which were obtained from the temperature dependences of equilibrium constants, show that in most cases the complexes are enthalpy destabilized but entropy stabilized. Non-linear behavior is observed between the equilibrium constants (log K _f ) of complexes and the composition of the mixed solvent. The selectivity of the ligand for these metal cations is sensitive to the solvent composition, and, in some cases, the selectivity order is reversed in certain compositions of the mixed solvent. The results also show that the mechanism of complexation reactions and the stoichiometry of complexes of some metal cations change with the nature and even with the composition of the mixed solvent. The article was submitted by the authors in English.     

Difference of Electron Capture and Transfer Dissociation Mass Spectrometry on Ni<Superscript>2+</Superscript>-, Cu<Superscript>2+</Superscript>-, and Zn<Superscript>2+</Superscript>-Polyhistidine Complexes in the Absence of Remote Protons

Electron capture dissociation (ECD) and electron transfer dissociation (ETD) in metal-peptide complexes are dependent on the metal cation in the complex. The divalent transition metals Ni²⁺, Cu²⁺, and Zn²⁺ were used as charge carriers to produce metal-polyhistidine complexes in the absence of remote protons, since these metal cations strongly bind to neutral histidine residues in peptides. In the case of the ECD and ETD of Cu²⁺-polyhistidine complexes, the metal cation in the complex was reduced and the recombination energy was redistributed throughout the peptide to lead a zwitterionic peptide form having a protonated histidine residue and a deprotonated amide nitrogen. The zwitterion then underwent peptide bond cleavage, producing a and b fragment ions. In contrast, ECD and ETD induced different fragmentation processes in Zn²⁺-polyhistidine complexes. Although the N–C_α bond in the Zn²⁺-polyhistidine complex was cleaved by ETD, ECD of Zn²⁺-polyhistidine induced peptide bond cleavage accompanied with hydrogen atom release. The different fragmentation modes by ECD and ETD originated from the different electronic states of the charge-reduced complexes resulting from these processes. The details of the fragmentation processes were investigated by density functional theory.

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The thermodynamic characteristics of complex formation between Ni<Superscript>2+</Superscript> ions and D,L-threonine in aqueous solution

The heat effects of interaction between solutions of D,L-threonine and Ni(NO₃)₂ were measured by direct calorimetry at 298.15 K and ionic strength values of from 0.5 to 1.5 (KNO₃). The heat effects of formation of the NiL⁺, NiL₂, and NiL ₃ ^? complexes were calculated. The influence of background electrolyte concentration on the heats of complex formation in the Ni²⁺-D,L-threonine system was studied. The standard heat effects of formation of Ni²⁺ complexes with D,L-threonine were obtained by extrapolation to zero ionic strength. The standard enthalpies of formation of NiL⁺, NiL₂, and NiL ₃ ^? in aqueous solution were calculated.     

Synthesis,characterization and biological studies of Co<Superscript>II</Superscript>, Ni<Superscript>II</Superscript>, Cu<Superscript>II</Superscript> and Zn<Superscript>II</Superscript> complexes of Schiff bases derived from 4-substituted carbostyrils[quinolin2(1H)-ones]

Schiff bases derived from 4-aminomethylcarbostyril and their transition metal complexes with Co^II, Ni^II, Cu^II and Zn^II have been synthesized and characterized by elemental analysis, molar conductance, magnetic susceptibilities electronic, IR, PMR, ESR, FAB-Mass and thermal studies. From the above spectral studies it is concluded that the ligands of 4-substituted carbostyril Schiff bases, viz, salicylidene 4-aminomethylcarbostyril (SAMC); o-vanillinsalicylidene 4-aminomethylcarbostyril (VAMC) and 5′ chlorosalicylidene 4-aminomethylcarbostyril (CSAMC) act as bidenate molecules coordinating through azomethine nitrogen and phenolic oxygen. The ligands and their metal complexes have been screened in vitro for antibacterial, antifungal and antitumor activity. The results indicate that the biological activity increases on complexation. The Cu^II complexes of the above ligands show greater inhibitory action towards the P388/s tumor cells at lower concentrations.     

Complexation studies of Co<Superscript>2+</Superscript>ion with orthosilicic acid

Summary The complexation behavior of Co²⁺with ortho-silicic acid (o-SA) has been studied as a function of ionic strength (I) from 0.20 to 1.00M (NaClO₄) at pH 4.96±0.03 and 25 °C by solvent extraction with bis(2-ethylhexyl) phosphoric acid (HDEHP) as the extractant. The stoichiometry of the extracted species was determined to be Co(DEHP)₂(HDEHP)₂. Co²⁺forms a 1:1 complex, CoOSi(OH)₃⁺, as the predominant species witho-SA concentrations of 3.00^. 10^-4to 4.00^. 10^-3M. The stability constant (logb₁) values for CoOSi(OH)₃⁺complex decrease with the increase in ionic strength. These values were fitted with the extended Debye-Huckel expression to obtain the value of logb₁at I=0.00M. The effect of aging time of the o-SA solution on logb₁values for CoOSi(OH)₃⁺complex was investigated and compared with those of the UO₂OSi(OH)₃⁺complex.     

Interaction energies of histidine with cations (H<Superscript>+</Superscript>, Li<Superscript>+</Superscript>, Na<Superscript>+</Superscript>, K<Superscript>+</Superscript>, Mg<Superscript>2+</Superscript>, Ca<Superscript>2+</Superscript>)

The imidazol side group of histidine has two nitrogen atoms capable of being protonated or participating in metal binding. Hence, histidine can take on various metal-bound and protonated forms in proteins. Because of its variable structural state, histidine often functions as a key amino acid residue in enzymatic reactions. Ab initio (HF and MP2) calculations were done in modeling the cation (H⁺, Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺) interaction with side chain of histidine. The region selectivity of metal ion complexation is controlled by the affinity of the side of attack. In the imidazol unite of histidine the ring nitrogen has much higher metal ion (as well as proton) affinity. The complexation energies with the model systems decrease in the following order: Mg²⁺ > Ca²⁺ > Li⁺ > Na⁺ > K⁺. The variation of the bond lengths and the extent of charge transfer upon complexation correlate well with the computed interaction energies.