Complexation of copper(II) with 3-(2-hydroxyphenylazo)pentadione-2,4

It is shown that 3-(2-hydroxyphenylazo)pentadione-2,4 (H₂L) can exist in three tautomeric forms (enol-azo, keto-azo, and hydrazo). The effective atomic charges in the tautomeric forms of H₂L are calculated by the Hückel MO LCAO method. The molar fractions and molar absorptivities of the tautomers at different pH are found. The complexation of copper(II) with H₂L is studied by spectrophotometry. Beer’s law is obeyed for 0.51–5.12 μg/mL of copper. The assumed complex structure is given. The effect of foreign ions and masking agents on the complexation is studied. A procedure for the photometric determination of copper(II) in zinc-based alloys is proposed. Original Russian Text ? S.R. Gadzhieva, T.M. Mursalov, K.T. Makhmudov, F.G. Pashaev, F.M. Chyragov, 2006, published in Zhurnal Analiticheskoi Khimii, 2006, Vol. 61, No. 6, pp. 598–603.     

Methane Adsorption and Plasma-Assisted Catalytic Conversion on the Surface of γ-Alumina

Diffuse scattering IR spectroscopy was applied to study the adsorption and plasma-assisted catalytic conversion of methane (deuteromethane) on the surface of -alumina. It was found that CH₄ adsorption sites on the -Al₂O₃ surface were formed by molecular and dissociative mechanisms under the action of an electric-discharge plasma at room temperature. As distinct from -radiolysis, plasma treatment leads to the formation of acetylene in addition to other hydrocarbon products, aluminum hydrides, and surface hydroxyl groups. Plausible mechanisms were proposed for plasma-assisted catalytic reactions in the -Al₂O₃–adsorbed CH₄(CD₄) system.     

Giant magnetoresistance and kinetic phenomena in <Emphasis Type="Italic">n</Emphasis>-Ag<Subscript>4</Subscript>SSe in the vicinity of a phase transition

Isotropic giant negative magnetoresistance (from ?42 to ?52%) in magnetic fields of 6–9 kOe is revealed for the first time when studying kinetic phenomena and the magnetoresistive effect in silver sulfoselenide (n-Ag₄SSe) in the vicinity of a first-order phase transition. The electron transport and the magnetoresistive effect in n-Ag₄SSe are studied for the first time.     

Synthesis of 2-substituted benzo-1,3-ditelluroles

A method for the synthesis of 2-phenylbenzo-1,3-ditellurole by the reaction of disodiumo-benzeneditellurolate with benzylidene chloride was proposed. 2-Methylbenzo-1,3-ditellurole and benzo-1,3-ditellurole-2-carboxylic acid were prepared by the reaction of 2-lithiobenzo-1,3-ditellurole with MeI and CO₂, respectively. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1132–1134, June, 2000.     

Spectrophotometric study of scandium(III) complexation with 2,2′,3,4-tetrahydroxy-3′-sulfo-5′-nitroazobenzene in the presence of papaverine, dibazole, and urotropine

Complexes of scandium(III) with 2,2′,3,4-tetrahydroxy-3′-sulfo-5′-nitroazobenzene were studied in the absence and presence of a third component, papaverine, dibazole, or urotropine. Optimal conditions for their formation were found, and their spectrophotometric parameters were determined. It was found that binary compounds ScR and mixed-ligand compounds formed at pH 2 exhibited absorption maxima at 477, 482, 479, and 478 nm. The stability constants of the complexes were calculated. The determination of scandium(III) with 2,2′,3,4-tetrahydroxy-3′-sulfo-5′-nitroazobenzene in the presence of papaverine, dibazole, and urotropine was found to be selective in comparison to the other known reagents. A procedure was developed for the photometric determination of scandium in hard rocks.     

Quantum-chemical calculations of the tautomeric forms of 3-phenylazopentane-2,4-dione and the thermodynamic parameters of complexation between its isomers and some metals in aqueous ethanol

MO LCAO calculations in the Hückel approximation of the tautomeric (azo enol, oxo azo, and hydrazo) forms of 3-phenylazopentane-2,4-dione (L) revealed that the oxo azo tautomer is most reactive. The effective charges at the atoms of all the tautomers were calculated. Complexation between some metals and L in aqueous ethanol was studied by potentiometric and conductometric titration. The potentiometric data were used to calculate the standard thermodynamic functions of the complexation.     

Angular distributions in proton-nucleus interactions in emulsion at 800 GeV

Data on angular distributions of heavily ionizing and shower particles in incoherent protonnucleus collisions in emulsion at 800 GeV are reported and discussed in details. Dependence of angular distributions on the mass number of a target nucleus and on the multiplicity of charged particles is investigated. The data presented are systematically compared with results of emulsion experiments at lower energies and with predictions of the Lund Monte Carlo model FRITIOF.     

Stability constants of polymer-metal complexes

Conditional stability constants of metal complexes with synthesized copolymers are studied by potentiometric titration. Linear copolymers are found to form more stable complexes than cross-linked sorbents with analogous functional groups. The stability of these complexes decreases in the order Th(IV) > Fe(III) ≈ La(III) > Cu(II).