Analytical complexation reactions of organic reagents with metal ions in a solidified gelatin gel

Solidified gelatin gel is an original medium for analytical complexation reactions between organic reagents and element ions. The chemical nature of this biopolymer enables the electrostatic immobilization of organic reagents bearing anionic groups, like Arsenazo III, by protonated amino groups of the macromolecule. It was shown that the exhaustive capacity of the matrix towards organic sulfonate reagents differing in the number of sulfonic groups and the geometrical size of molecules was related to the specific properties of matrices and the fractal properties of the gel surface. It was found that the conditions for the reactions of complex formation and decomposition of the reagents immobilized in the gel were identical to those for reactions in aqueous solutions. It was proved that the gel fixed on a transparent triacetylcellulose support could be used as a component of sensing elements of optical sensors and/or test systems. This was demonstrated by the examples of the determination of La(III), Th(IV), U(VI), Ca(II), and SO₄²⁻.     

Use of organic reagents for the voltammetric determination of rare-earth elements

The data on organic reagents used for the voltammetric determination of rare-earth elements (REE) is surveyed. The mechanisms of the reduction of complexes formed by REE with some reagents are presented. Procedures for determining REE in real samples using organic reagents are briefly characterized.__________Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 4, 2005, pp. 342–348.Original Russian Text Copyright © 2005 by Dubenskaya, Levitskaya, Poperechnaya.     

Solvent extraction of several metal ions with mercaptotropone

Mercaptotropone was synthesized from tropone, and its acid dissociation constant (K_a) and distribution coefficient (K_D) between benze and aqueous solution were spectrophotometrically determined as 5.75 (pK_a) and 2.46 (log K_D); Extraction behaviour of Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Pb(II), Cr(III), Fe(III), Y(III), and Zr(IV) with this reagent into benzene was examined. Cu(II) and Fe(III) were completely extracted from acidic solution, Mn(II), Co(II), Ni(II), Zn(II), Pb(II), and Zr(IV) were also extracted from intermediate pH region, a part of Cr(III) was extracted, but Y(III) was not extracted.     

CVD of metal organic and other rare-earth compounds

Three major applications have been found for rare-earth compounds in Metal Organic Chemical Vapour Depostion (MOCVD) or Chemical Vapour Deposition (CVD). Yttrium 2,2,6,6-tetramethyl-3,5-heptanedionates and 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionates have been used in conjunction with barium and copper(II) β-diketonates to deposit YBa₂Cu₃O_7−δ as superconducting thin films. Rare-earth fluorides and chlorides have been used for CFD doping of rare earths into MOCVD-deposited ZnS, whilst yttrium chloride has been used, with barium iodide and copper(I) chloride, to produce YBa₂Cu₃O_7−δ superconducting material by CVD. Lanthanoid (Ln) tris(cyclopentadienyl) compounds, Ln(C₅H₅)₃ or Ln(C₅H₄Me)₃, have been used for doping of rare earths into 13–15 (III–V) semiconductors. Their volatility, structure/volatility relationships, and preparations are discussed. Possible alternative reagents and problems to be faced in doping 12–16 (II–VI) semiconductors are also considered.     

Sulphoxides as solvating reagents for the separation of metal ions

The solvent extraction properties of the following sulphoxides have been evaluated: di-n-octyl sulphoxide (DOSO), bis(n-octylsulphinyl) methane (BOSM), bis(n-octylsulphinyl)ethane (BOSE) and p-tolyl sulphoxide (PTSO). By use of reversed-phase paper chromatography as a qualitative surveying technique, the interactions of these sulphoxides with some fifty metal ions were investigated in several acid-ligand systems. All sulphoxides were studied in 1-10M hydrochloric and nitric adds; DOSO and BOSM were also studied in perchloric acid and ammonium thiocyanate-perchloric acid mixtures. Observations are made concerning sulphoxide-metal interactions and the existence of several useful analytical separation systems is pointed out. The synthesis and characterization of BOSM and BOSE are described.     

Hydrodebromination of bromoarenes using Grignard reagents catalyzed by metal ions

The metal salts, FeCl^·₂4H₂O, FeCl₃, NiCl₂, CoCl₂, CuBr and some iron complexes were found to be efficient catalysts for hydrodebromination of bromoarenes under mild reaction conditions with two equivalents of Grignard reagents. Among them, the iron systems showed the best behavior regarding economic and environmental considerations. All the alkyl Grignard reagents (except CH₃MgCl) and p‐tolylMgBr were promising reductive reagents with the formation of their homo‐coupling products. Copyright © 2008 John Wiley & Sons, Ltd.     

噻吩在稀土离子改性Y型分子筛上吸附与催化转化研究

以NaY、HY、液相Ce离子交换改性Y分子筛(L-CeY)和稀土离子改性超稳Y分子筛(HRSY-3)为研究对象,运用XRD、N₂吸附、NH₃-TPD和Py-FTIR表征样品的物化性能;采用原位红外光谱技术与程序升温脱附-同步质谱检测联用技术(TPD-MS)研究噻吩在活性中心上的吸附及催化转化行为.结果表明,稀土离子改性不改变分子筛晶体的基本结构但改变其精细结构,并形成一定的介孔,同时降低分子筛强酸位的强度,并生成与稀土离子物种有关的弱L酸位.REY与HY均可通过B酸中心的质子化作用活化噻吩,而稀土离子物种促进氢转移反应及低聚反应的进行,进而利于噻吩裂化反应的进行.     

Polynuclear coordination compounds of alkali metal ions with organic chromophores

The crystal structures of sodium 4‐({4‐[N,N‐bis(2‐hydroxy­ethyl)­amino]­phenyl}diazenyl)­benzoate 3.5‐hydrate, Na⁺·C₁₇H₁₈N₃O₄^?·3.5H₂O, (I), and potassium 4‐({4‐[N,N‐bis(2‐hydroxy­ethyl)­amino]­phenyl}diazenyl)­benzoate dihydrate, K⁺·C₁₇H₁₈N₃O₄^?·2H₂O, (II), are described. The results indicate an octahedral coordination around sodium in (I) and a trigonal prismatic coordination around potassium in (II). In both cases, coordination around the metal cation is achieved through O atoms of the water mol­ecules and hydroxy groups of the chromophore. The organic conjugated part of the chromophore is approximately planar in (I), while a dihedral angle of 30.7 (2)° between the planes of the phenyl rings is observed in (II).     

Chiral allylic and allenic metal reagents for organic synthesis

This account traces the evolution of our work on the synthesis of chiral allylic and allenic organometal compounds of tin, silicon, zinc, and indium and their application to natural product synthesis over the past quarter century.     

Cation-exchange of metal ions in organic solvent-cupferron media

Distribution coefficients of 20 metal ions were determined on the strongly acidic cation-exchanger Dowex 50 in a 30:7:1 mixture of chloroform-methanol-lM hydrochloric acid which was 0.1M in cupferron. In this system the distribution coefficients of Fe(in), Ti(TV), Cu(II), Ce(III) and Th are lower by several orders of magnitude than those of Ni, Mn(II), Cd, Co(II), Ca, U(VI), and Sr. It is possible to separate these two groups of elements on an ion-exchange column.     

Membrane extraction of metal ions by aminophosphoryl reagents in the active transport conditions

The process of membrane extraction of rare earth ions, Nd(III), Sc(III), and Sm(III), and also the accompanying them in the natural raw material ions Al(III) and Mg(II), by N,N-bis(dihexylphosphorylmethyl)octylamine (BPA) was investigated under the conditions of active membrane transport, and its high efficiency and selectivity was demonstrated with respect to the two first rare earth metals. The influence of principal parameters of the three-phase extraction process, including the nitrate ion concentration, the releasing aqueous phase acidity, the extracting agent concentration in the membrane, and the nature of the membrane solvent, on the membrane permeability, characterizing the efficiency and selectivity of membrane transporters, was established. Comparison of the membrane permeability in the process of transmembrane transport of Nd(III) and Sc(III) with BPA and monophosphorylated amines showed a significant advantage of the biphosphorylated amine extractant.     

New fluorinated hydroxamic acid reagents for the extraction of metal ions with supercritical CO2

Research to date on the supercritical fluid extraction (SFE) of metal ions has focused on the use of dithiocarbamates and β-diketones. Hydroxamic acids are well known as effective chelating agents for a broad range of transition metal ions. Much attention has centred in inorganic chemistry on the effect of N-substitution on metal chelate stability and selectivity, and in analytical chemistry on the immobilisation of the chelating agents to the chosen solid supports such as silica. In this paper, the synthesis of selected fluorinated mono hydroxamic acids and their N-substituted derivatives is reported. The new reagents are applied in the SFE of metal ions in particular Fe(III) using unmodified supercritical CO₂. Metal extraction is monitored using atomic absorption spectroscopy and visible spectrophotometry. The extraction efficiencies were determined as a function of pressure and temperature. The new ligands synthesised and applied were perfluorooctanohydroxamic acid (PFOHA), heptafluorobutyrichydroxamic acid (HFBHA) and their N-methylhydroxamic acid derivatives. Of the synthesised reagents, PFOHA was the most soluble and effective extractant of Fe(III) from spiked filter paper, reaching 97% extraction of the metal ion under optimised conditions. The selectivity of this ligand for Fe(III) in the presence of Cu(II), Ni(II), Pb(II) and Zn(II) is also demonstrated.     

Effects of the alkali metal counter ions on the germanium-germanium double bond length in a heavier group 14 element ethenide salt

The first, well-characterized 1,2-dilithium salt of a group 14 element ethenide species, [[(dioxane)(0.5)(Et2O)LiGeC6H3-2,6-Mes2]2]infinity, shows that the positions of the cations have a large effect on the length of the Ge-Ge double bond.     

Polymeric sensors for determination of rare-earth metal ions, based on diamides of dipicolinic acid

New polymeric sensors with high sensitivity to cations of transition metals and lanthanides in acid media are suggested. The role of active substances in the polymeric membranes of the sensors is played by diamides of dipicolinic acid with various structures, which are compounds exhibiting a high extraction capacity for various metals.     

Studies on selenates: II. Thermal decomposition of heavier rare-earth selenate hydrates

Thermogravimetry, differential thermal analysis and differential thermogravimetry have been used to study the decomposition of hydrated selenates of heavier rare-earths and yttrium. Based on the results obtained, mechanisms of dehydration-decomposition have been proposed. Dehydration temperatures of the hydrated selenates show a gradual decrease with order of rare-earth elements.     

Detection and separation of metal ions on paper impregnated with 4-hydroxybenzthiazole

Zinc, magnesium and cadmium ions in the presence of ammonia, form intense blue chelates on paper impregnated, with 4-hydroxybenzthiazole, 0.25 microgram, 1.0 microgram and 0.1 microgram respectively, of these metal ions can be detected by means of this test. Several cations interfere.Alumunium can be separated from zinc, cadmium, copper, nickel and cobalt on paper impregnated with 4-hydroxybenzthiazole, which acts as a chromatographic column.     

Detection of metal ions in aqueous solution by voltohmmetry

A new electrochemical detection principle is described for the trace analysis of dissolved species which can be deposited at polycrystalline thin-film metal electrodes and which change the surface resistance of the electrode. Because the latter parameter is measured in dependence on the applied electrode potential this method is called voltohmmetry. The preparation of the required thin-film electrodes and the experimental set-up is introduced and discussed. Typical voltohmmetric experiments are illustrated by measurements of Tl+/Tl at polycrystalline gold electrodes with a thickness of 15 nm. The analytical capabilities of this new approach are discussed. It is already possible to determine heavy metals such as Tl+, Pb2+ or Cd2+ in the range of a few microgram/L by surface resistance-potential measurements at thin-film electrodes with a simple cyclic technique. Further developments of voltohmmetry are envisaged.