Polymerization of polystyryl-barium in THF—I. Kinetics of mono- and α,ω-dicarbanionic mixtures

The kinetics of propagation of mixtures of mono- and bicarbanionic polystyryl-barium (PS^?)₂Ba²⁺ and (PS^2?Ba²⁺) were studied in THF and the molecular weight distribution of the resulting polystyrene was analyzed. (PS^?)₂Ba propagates much more rapidly than PS^2?Ba²⁺, each kind of chain keeping a narrow molecular weight distribution. The propagation rate of (PS^?)₂Ba²⁺ is strongly decreased by the presence of oligo PS^2?Ba²⁺. The results are explained by the formation of mixed triple ions between cyclic PS^2?Ba²⁺ and monocarbanionic (PS^?)₂Ba²⁺ and by mixed associations of ion pairs, specially important for small PS^2?Ba²⁺.     

Theoretical estimate of the stability constants of metal complexes of aliphatic and heterocyclic amines in aqueous solutions

The stability constants of 1: 1 complexes of Mg²⁺, Ca²⁺, Cd²⁺, Co²⁺, Cu²⁺, Fe²⁺, Mn²⁺, Ni²⁺, and Zn²⁺ with 29 N-donor ligands (ammonia, alkylamines, aniline, pyridine, imidazole, pyrazole, benzimidazole, isoquinoline, and their alkyl-and halogen-substituted derivatives) in aqueous solutions at 298 K were calculated by integration of the ligand distribution function. The stability constants are determined by the effective charge on the electron donor atom of the ligand and by the sizes of the cation and ligand, as well as by the degree of covalence of the coordination bond.     

Cation binding by 2<Superscript>1</Superscript>,3<Superscript>1</Superscript>-diphenyl-l <Superscript>2</Superscript>,4<Superscript>2</Superscript>-dioxo-7,10,13-trioxa-1,4(3,1)-diquinoxalina-2 (2,3),3(3,2)-diindolizinacyclopentadecaphane and its acyclic analog

The binding of cations Li⁺, Na⁺, K⁺, Cs⁺, Ag⁺, Zn²⁺, Ni²⁺, Co²⁺, NH₄ ⁺ (group I), H⁺, Mg²⁺, Al³⁺, Ga³⁺ (group II), and Ca²⁺, Pb²⁺ (group III) by 2¹,3¹-diphenyl-l ²,4²-dioxo- 7,10,13-trioxa-l,4(3,1)-diquinoxalina-2(2,3),3(3,2)-diindolizinacyclopentadecaphane (1), which contains two indolizine and two quinoxaline fragments and 3,6,9-trioxaundecanes spacer, and by its acyclic analog (2) was studied using cyclic voltammetry in MeCN/0.1 M Bu₄NBF₄. It was concluded that the ions of group I are not bound by these compounds, the ions of group II exhibit the reversible redox-switched binding by the carbamoyl groups of the quinoxaline fragments, whereas the ions of group III are bound not only by the initial compounds and radical cations 1 and 2, but also by dication 1. This binding of the Ca²⁺ and Pb²⁺ ions stabilizes dication 1.     

Bulgarian natural diatomites: modification and characterization

Natural Bulgarian diatomite modified by oxidation with sulfuric acid and H₂O₂ or by coating with manganese oxide was characterized considering its chemical composition, surface area, pore volume, and structure. Modified diatomites displayed larger surface area and pore volumes in comparison with untreated natural diatomite, which favored their sorption behavior. Sorption properties of diatomites towards Fe³⁺, Pb²⁺, Cu²⁺, Cd²⁺, Mn²⁺, Ni²⁺, Co²⁺, Cr³⁺, Pd²⁺, Ca²⁺, and Mg²⁺ were investigated and their sorption capacities were determined. Sorption properties of manganese oxide-modified diatomite were superior to those of diatomite modified by oxidation. Owing to its high sorption capacity towards Co²⁺, Ni²⁺, Pb²⁺, Cr³⁺, Fe²⁺, Cu²⁺, and Cd²⁺, the manganese oxide-modified diatomite is a promising low-cost sorbent for selective removal of milligram amounts of these toxic metal ions from contaminated water.     

Analytical aspects of some organic acids Part III

Summary m-Phenylenedioxydiacetic acid gives a white precipitate with thorium even in the absence of an electrolyte which is quantitative up toph 4. Be²⁺, Mg²⁺, Ca²⁺, Zn²⁺, Pb²⁺ and Mn²⁺ ions are removed by single precipitation and Al³⁺, UO₂ ²⁺ and trivalent cerite earth ions are removed by double precipitation. Sn²⁺, Sn⁴⁺ and Cr³⁺ ions interfere.Part II: See. Z. analyt. Chem.165, 343 (1959).     

The Synthesis of New Triazole Ligands and Determination of Complex Stability Constants with Transition Metal Cations in Aqueous Media

Six new triazole compounds were synthesized. These compounds containing the substituted benzylidenamino group were obtained by reaction of 3-(pyridine-4-yl)-5-p-tolyl-4-amino-4H-l,2,4-triazole 1 with the corresponding aldehyde. The reduced forms were prepared with NaBH₄ in methanol. The structures of the compounds were determined by IR, ¹H NMR, and ¹³C NMR spectral data, and their interaction with cations such as Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Ba²⁺, Sr²⁺, Ca²⁺, Cu²⁺, Cr³⁺, Co²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Pb²⁺ and Ag⁺ were investigated by using UV-visible spectrophotometry. Of the tested metal cations, Cu²⁺, Cr³⁺, Co²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Pb²⁺ and Ag⁺ complexed with the ligands. The complex stability constants (log ₁₀ K) were measured in slightly acidic aqueous media at 25.0±0.1 °C. These stability constants were determined by measuring the increase in solubility of the nearly insoluble ligand molecule due to complex formation with a soluble cation, and this method is discussed. It was found that the position of chlorine atoms on the benzene ring strongly affects the complexation of Cu²⁺ ion with these ligands.     

Application of the inner product technique to double-well potentials in three-dimensional quantum systems by expanding the potential functions around their minima

Energy eigenvalues of double-well potentials for three-dimensional systems are calculated by means of an expansion of the potential function V(x,y,z;Z²,λ,a_IJ)=-Z²[x²+y²+z²] +λ{x⁴+y⁴+z⁴+2a_IJ[x²y²+x²z²+y²z²]} around its minimum, using the inner product technique, for various values of perturbation parameters Z²,λ and a_IJ. Some of the results calculated by this technique are compared with results obtained by other methods. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis and Characterization of Metal Complexes of two Novel Pyridine‐Derived Macrocyclic Ligands Bearing o‐ and p‐Nitrobenzyl Pendant Groups

The pendant‐armed ligands L¹ and L² were synthesized by N‐alkylation of the two secondary aminic groups of the oxaazamacrocyclic precursor L with o‐nitrobenzylbromide (L¹) or p‐nitrobenzylbromide (L²). Metal complexes of L¹ and L² have been synthesized and characterized by microanalysis, MS‐FAB, conductivity measurements, IR, UV‐Vis, ¹H and ¹³C NMR spectroscopy and magnetic studies. Crystal structures of ligands L¹ and L², as well as complexes [CdL¹(NO₃)₂]·2CH₃CN and [Ag₂Br(L²)₂](ClO₄)·2CH₃CN have been determined by single crystal X‐ray crystallography.     

Dinuclear Schiff-base copper(II) complexes with various bridging groups

Three new centrosymmetric dinuclear copper(II) complexes, [Cu₂Cl₂(L¹)₂] (1), [Cu₂(μ _1,3-NCS)₂(L²)₂] (2), and [Cu₂(μ _1,1-N₃)₂(L³)₂] (3), where L¹, L², and L³ are the deprotonated forms of the Schiff bases 1-[(2-propylaminoethylimino)methyl]naphthalen-2-ol (HL¹), 1-[(3-methylaminopropylimino)methyl]naphthalen-2-ol (HL²), and 2-[(2-isopropylaminoethylimino)methyl]phenol (HL³), respectively, have been prepared and characterized by elemental analysis, IR spectra, and single-crystal X-ray crystallography. Each Cu is coordinated by the three donors of the Schiff bases and by two bridging groups, forming a square-pyramidal geometry.     

Potentiometric and spectrophotometric titration of Cu2+ complexes with N-isopropyl-2-methyl-1,2-propanediamine

The complexation of Cu²⁺ by N-isopropyl-2-methyl-1,2-propanediamine (L) has been studied by potentiometric and spectrophotometric titration. The dominant complexes formed in this system are [CuL]²⁺, [CuL₂]²⁺, [Cu₂L₂(OH)₂]²⁺, and [CuL(OH)₂]. The data were thoroughly tested for different models with [CuL(OH)]⁺, [CuL(OH)]⁺, [Cu(OH)]⁺, and [Cu₂(OH)₂]²⁺ as additional species. The importance of steric factors is indicated by the d-d* spectra: for [CuL₂]²⁺, (λ_max = 499 nm) the absorption maximum is shifted by 50 nm to high energies relative to [Cu(en)₂]²⁺, (λ_max = 549 nm), whereas the opposite is true for the 1:1 complexes ([CuL]²⁺ : λ_max = 712 nm,s [Cu(en)]²⁺ : λ_max = 660 nm).     

The stability constants of some bivalent metal complexes of α-hydroxyisobutyrate and lactate

The stability constants of the lactate and α-hydroxyisobutyrate complexes of Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺ and UO₂²⁺ were determined by potentiometric titration. The average ligand number exceeds 2, indicating the formation of ML⁺, ML₂ and ML₃^- complexes. The existence of ML₃^- complexes was confirmed by electrophoretic experiments; no polynuclear complexes were formed. α-Hydroxyisobutyrate forms stronger complexes than lactate.     

Complex Compounds Based on 1-Isopropenylimidazoles and -pyrazole

With respect to Co²⁺, Ni²⁺, Zn²⁺,Cd²⁺, Cu²⁺, Pd²⁺, and Sn⁴⁺ salts, 1-isopropenyl-substituted imidazole, 2-methylimidazole, and pyrazole behave as monodentate ligands with only one coordination center on the N¹ and N² atoms, respectively; 1-isopropenylpyrazole under complex-formation conditions is dealkylated to form pyrazole complexes. The reaction with HCl leaves the unsaturated substituent in 1-isopropenylimidazole intact and yields corresponding hydrochlorides by the N³ atom of the heterocycle. The least basic 1-isopropenylpyrazole takes up HCl also by the double bond of the alkenyl group.     

Rigid ferrocenophane and its metal complexes with transition and alkaline-earth metal ions

The rigid [6]ferrocenophane, L¹, was synthesised by condensation of 1,1′-ferrocene dicarbaldehyde with trans-1,2-diaminocyclohexane in high dilution at r.t. followed by reduction. When other experimental conditions were employed, the [6,6,6]ferrocenephane (L²) was also obtained. Both compounds were characterised by single crystal X-ray crystallography. The protonation of L¹ and its metal complexation were evaluated by the effect on the electron-transfer process of the ferrocene (fc) unit of L¹ using cyclic voltammetry (CV) and square wave voltammetry (SWV) in anhydrous CH₃CN solution and in 0.1 M ⁿBu₄NPF₆ as the supporting electrolyte. The electrochemical process of L¹ between −300 and 900 mV is complicated by amine oxidation. On the other hand, an anodic shift from the fc/fc⁺ wave of L¹ of 249, 225, 81 and 61 mV was observed by formation of Zn²⁺, Ni²⁺, Pd²⁺ and Cu²⁺ complexes, respectively. Whereas Mg²⁺ and Ca²⁺ only have with L¹ weak interactions and they promote the acid-base equilibrium of L¹. This reveals that L¹ is an interesting molecular redox sensor for detection of Zn²⁺ and Ni²⁺, although the kinetics of the Zn²⁺ complex formation is much faster than that of the Ni²⁺ one. The X-ray crystal structure of [PdL¹Cl₂] was determined and showed a square–planar environment with Pd(II) and Fe(II) centres separated by 3.781(1) Å. The experimental anodic shifts were elucidated by DFT calculations on the [ML¹Cl₂] series and they are related to the nature of the HOMO of these complexes and a four-electron, two-orbital interaction.     

Quantitative Trennung von Schwermetallen mit Chelataustauschern auf der Basis von Polystyrol

Zusammenfassung Die Trennung und Isolierung von folgenden Schwermetallen bei einem hohen Überschuß an Fremdionen mit Hilfe neuer selektiver Chelataustauscher wird beschrieben: Cu²⁺/Zn²⁺, Cu²⁺/Pb²⁺, Ag⁺/Cu²⁺, Ag⁺/Pb²⁺, Hg²⁺/Zn²⁺, Hg²⁺/Cd²⁺; Abtrennung von Hg²⁺. Unter gleichen Bedingungen war mit dem handelsüblichen Austauscher Dowex A-1 keine Trennung möglich.

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Quantitative separation of heavy metals by means of chelating exchangers based on polystyrol

Summary The separation and isolation of the following heavy metals in presence of a high excess of foreign ions by means of new selective chelating exchangers is described: Cu²⁺/Zn²⁺, Cu²⁺/Pb²⁺, Ag⁺/Cu²⁺, Ag⁺/Pb²⁺, Hg²⁺/Zn²⁺, Hg²⁺/Cd²⁺; separation of Hg²⁺. Under the same conditions no separation could be achieved by the ion-exchanger Dowex A-1.

     

Chemosensor properties of 7-hydroxycoumarin substituted cyclotriphosphazenes

The newly synthesized cyclotriphosphazene cored coumarin chemosensors 5, 6, and 7 were successfully characterized by ¹ H NMR, ³¹ P NMR, and MALDI-TOF mass spectrometry. Additionally, the photophysical and metal sensing properties of the targeted compounds were determined by fluorescence spectroscopy in the presence of various metals (Li ⁺ , Na ⁺ , K ⁺ , Cs ⁺ , Mg ²⁺ , Ca ²⁺ , Ba ²⁺ , Cr ³⁺ , Mn ²⁺ , Fe ³⁺ , Co ²⁺ , Al ³⁺ , Hg ⁺ , Cu ²⁺ , Zn ²⁺ , Ag ⁺ , and Cd ²⁺ ) . The fluorescence titration results showed that compounds 5, 6, and 7 could be employed as fluorescent chemosensors for Fe ³⁺ ions with high sensitivity. The complex stoichiometry between final cyclotriphosphazene chemosensors and Fe ³⁺ ions was also determined by Job’s plots.     

A new chelating resin containing 2-aminothiophenol: Synthesis characterization and determination of mercury in waste water using <Superscript>203</Superscript>Hg radiotracer

A new stable chelating resin was synthesized by incorporating 2-aminothiophenol into Merrifield polymer through C-N covalent bond and characterized by elemental analysis, IR and thermal study. The sorption capacity of the newly formed resin for Hg²⁺ as a function of pH has been studied using ²⁰³Hg radioisotope. The resin exhibits no affinity to alkali or alkaline earth metal ions and common anions. The separation of mercury(II) in presence of different alkali and alkaline earth metal ions (Na⁺, K⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺), common anions (ClO₄ ⁻, SO₄ ²⁻) and other diverse ions (Ag⁺, Cu²⁺, Pb²⁺, Fe³⁺, Ni²⁺ and Zn²⁺) has been checked. In column operation it has been observed that Hg²⁺ content of the waste water can be removed at usual pH of natural water. Mercury was determined by isotope dilution method and the concentration of Hg²⁺ in the waste water spiked with ²⁰³Hg was found to be 0.05 to 0.09 μg/ml.     

A Highly Selective Colorimetric Sensor for Cu2+ Based on Phenolic Group Biscarbonyl Hydrazone

A novel copper selective sensor 2 based on hydrazide and salicylaldehyde has been designed and prepared. Sensor 2 behaves a single selectivity and sensitivity in the recognition for Cu²⁺ over other metal ions such as Fe³⁺, Hg²⁺, Ag⁺, Ca²⁺, Zn²⁺, Pb²⁺, Cd²⁺, Ni²⁺, Co²⁺, Cr³⁺ and Mg²⁺ in DMSO. The distinct color change and the rapid changement of fluorescence emission provide naked‐eyes detection for Cu²⁺. The UV‐vis data indicate that 1:2 stoichiometry complex is formed by sensor 2 and Cu²⁺. The association constant K_s was 3.51×10⁴ mol^?1·L. The detection limitation of Cu²⁺ with the sensor 2 was 2.2×10^?7 mol·L^?1. The sensing of Cu²⁺ by this sensor was found to be reversible, with the Cu²⁺‐induced color being lost upon addition of EDTA.     

Lifetimes and perturbations of the 3d9 4s(3D) 4p structure in the spectrum of copper I

Natural radiative lifetimes have been measured of the²P,²D,²F and⁴D_5/2 terms in the 3 d⁹ 4s(³D) 4p structure of copper I. A pulsed hollow cathode was used to generate 3d⁹ 4s^{2 2}D metastable atoms. From these metastable levels the states investigated were populated by a pulsed dye laser pumped by a Nd:YAG laser. A comparison with theoretical and experimental literature values is given.     

Kinetics of the exchange between MnO or Mn3O4 and some divalent cations in aqueous solution

The kinetics of the exchange between MnO or Mn₃O₄ and Co²⁺, Cu²⁺, Ni²⁺, or Zn²⁺ ions in solution, was determined by measuring the γ-activity of⁵⁶Mn acquired by the solution after shaking with the neutron irradiated solid. The results indicated a fast exchange followed by a slower apparently diffusion-controlled exchange. The exchange capacity increased in the series: Co²⁺<Ni²⁺<Cu²⁺=Zn²⁺ for MnO and Ni²⁺<Co²⁺<Zn²⁺<Cu²⁺ for Mn₃O₄. The trends could not be satisfactorily explained by the ionic radii or crystal field stabilisation-energies. In the case of MnO, the results were discussed in terms of the estimated standard enthalpy change of the exchange reaction.     

ADSORPTION OF UO2 2+ BY POLYETHYLENE HOLLOW FIBER MEMBRANE WITH AMIDOXIME GROUP

The polyethylene (PE) membrane was prepared by the radiation-induced grafting of acrylonitrile (AN) onto PE hollow fiber and by the subsequent amidoximation of cyano groups in poly-AN graft chains. The adsorption characteristics of the chelating hollow fiber membrane was examined as the solution of UO₂ ²⁺ permeated across the chelating hollow fiber membrane. The inner and outer diameter increased with an increasing grafting yield, whereas, the pure water flux and pore diameter decreased with an increasing grafting yield. The adsorption of UO₂ ²⁺ by the chelating hollow fiber membranes increased with an increasing amidoxime group. The adsorbed amount of UO₂ ²⁺ in the uranyl acetate solution was higher than that in the uranyl nitrate solution. The adsorbed amount of UO₂ ²⁺ is higher than that of Cu²⁺ when the solution of UO₂ ²⁺ and Cu²⁺ permeated across the chelating membrane, respectively. The adsorption characteristics of UO₂ ²⁺ by the amidoxime group-chelating fiber membrane in the presence of Na¹⁺ and Ca²⁺ showed a high selectivity for UO₂ ²⁺ even though there was a high concen-tration of Na¹⁺ and Ca²⁺ in the inlet solution.