Synthesis and antimicrobial activities of gold(I) sulfanylcarboxylates

Reaction of NaAuCl₄·H₂O and thiodiglycol (1:3 molar ratio) with 3-(aryl)-2-sulfanylpropenoic acids, H₂ xspa = [x:p = 3-phenyl-, f = 3-(2-furyl)-, t = 3-(2-thienyl)-, o-py = 3-(2-pyridyl)-, Clp = 3-(2-chlorophenyl)-, -o-mp = 3-(2-methoxyphenyl)-, -p-mp = 3-(4-methoxyphenyl)-, -o-hp = 3-(2-hydroxyphenyl)-, -p-hp = 3-(4-hydroxyphenyl)-, diBr-o-hp = 3-(3,5-dibromo-2-hydroxyphenyl)] and 2-cyclopentylidene-2-sulfanylacetic acid (H₂cpa) in a 1:1 metal/ligand molar ratio gave compounds of the type [Au(Hxspa)] or [Au(Hcpa)]. These compounds were reacted with diisopropylamine to afford [HQ][Au(xspa)] or [HQ][Au(cpa)] (HQ = diisopropylammonium) and with NaOH to afford Na[Au(xspa)]·H₂O and Na[Au(cpa)]·H₂O. All of the new compounds were isolated and characterised by IR and ¹H and ¹³C NMR spectroscopy. The antimicrobial activities of the complexes against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Candida albicans, Pseudomonas aeruginosa and carbapenem-resistant P. aeruginosa were evaluated and compared to those of the equivalent silver(I) complexes. The comparison shows that the gold compounds generally show better activity than the silver analogues against S. aureus and B. subtilis, but low sensitivity against E. coli, P. aeruginosa and C. albicans, suggesting a different mode of antimicrobial action for equivalent silver and gold compounds.     

Phase Relations in the Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-V<Subscript>2</Subscript>O<Subscript>5</Subscript>-MoO<Subscript>3</Subscript> System in the Solid State. The Crystal Structure of AlVO<Subscript>4</Subscript>

Phase relations in the ternary oxide system Al₂O₃-V₂O₅-MoO₃ in the solid state in air have been investigated by using the x-ray diffraction (XRD) and differential thermal analysis/thermogravimetric (DTA/TG) methods. It was confirmed that in the subsolidus area of the Al₂O₃-V₂O₅-MoO₃ system, there exist seven phases, that is Al₂O₃, V₂O_5(s.s.), MoO₃, AlVO₄, Al₂(MoO₄)₃, AlVMoO₇, and V₉Mo₆O₄₀. Seven fields, in which particular phases coexist at equilibrium, were isolated. The crystal structure of AlVO₄ has been refined from x-ray powder diffraction data. Its space group is triclinic, , Z = 6, with a = 0.65323(1) nm, b = 0.77498(2) nm, c = 0.91233(3) nm, α = 96.175(2)°, β = 107.234(3)°, γ = 101.404(3)°, V = 0.42555 nm³. The crystal structure of the compound is isotypic with FeVO₄. Infrared (IR) spectra of AlVO₄ and FeVO₄ are compared.     

Gas adsorption at the components of the GaAs-CdS system

Adsorption properties of the GaAs-CdS-system solid solutions and binary compounds are studied with respect to CO and NH₃ by the piezoelectric quartz microweighing, programmed thermal desorption, and IR-spectroscopy. Based on the experimental dependences (α_p = f(T), αT = f(P), αT = f(t)), thermodynamic and kinetic characteristics of adsorption, analysis of the surface chemical composition, the adsorbents’ acid-base and other physicochemical characteristics. With due allowance for electron structure of the adsorbate’s molecules, the mechanism and specifity of adsorption processes are determined as functions of the operation conditions and system composition. By comparing the adsorption properties of the binary compounds (GaAs and CdS) with those of the solid solutions (GaAs) _x (CdS)_1−x , their similarities, as well as the specificity of the solid solutions as multicomponent systems, were revealed. Optimal adsorbent compositions to be used in primary transducers in the medicine-and environment-orientated sensors are found. Original Russian Text ? I.A. Kirovskaya, 2008, published in Zashchita Metallov, 2008, Vol. 44, No. 2, pp. 197–203.     

Nanostructure and energy properties of the stainless steel X18N10T surface studied by scanning tunneling microscopy and scanning tunneling spectroscopy. 2. Measurements at different potentials in HCl and H2SO4 solutions

Stainless steel Kh18N10T is studied by electrochemical scanning tunneling microscopy (ESTM) and electrochemical scanning tunneling spectroscopy (ESTS) at the interface with solutions of 0.01 N HCl and 0.1 N H₂SO₄ at the controlled sample and tip potentials. The sample potential varied from −0.46 to +1.14 V in 0.01 N HCl and from −0.06 to +0.74 V (NHE) in 0.1 N H₂SO₄. It is shown that although in the studied acid solutions at the controlled potential the surface is smother than in air, this does not allow one to determine the extremal values of parameters α, β, and γ corresponding to individual properties of Fe, Cr, and Ni or their oxides. It is shown that compared to the steel nanorelief, the sample potential has a stronger effect on the electrophysical properties that determine the tunneling transfer of electrons. Original Russian Text ? Yu.M. Stryuchkova, E.V. Kasatkin, 2008, published in Fizikokhimiya Poverkhnosti i Zashchita Materialov, 2008, Vol. 44, No. 6, pp. 620–626.     

Films containing nickel and iron compounds on aluminum and titanium

The composition of films formed by plasma electrochemical oxidation-deposition on aluminum and titanium in aqueous solutions containing both Ni(II) and Fe(III) polyphosphate complexes is studied. Elementary compositions of the outer part of the layers on aluminum and titanium differ insubstantially. Concentrations of nickel and iron (up to 30 wt %) in the films vary in proportion to their molar ratio in the electrolyte. Upon annealing in air, simple and multiple metal (M) oxides and phosphates crystallize in the layers, particularly, AlPO₄, NiAl₂O₄, and Fe₂O₃ on aluminum, while Ni₂P₂O₇, Ni_0.5TiOPO₄; NaTi₂(PO₄)₃, M(II)M(III)Ti(PO₄)₃, FePO₄, and Fe₂Fe(P₂O₇)₂ on titanium. Original Russian Text ? V.S. Rudnev, V.P. Morozova, 2008, published in Fizikokhimiya Poverkhnosti i Zashchita Materialov, 2008, Vol. 44, No. 5, pp. 506–509.     

Ternary Phase Equilibria at 450 °C in the Zn-Fe-P System

The 450 °C isothermal section of the Zn-Fe-P ternary phase diagram has been determined experimentally using optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD). The research of the work has concentrated on the Zn-rich corner, which is relevant to galvanizing. Experimental results indicate that P solubility in liquid zinc and all four Fe-Zn compounds, including ζ, δ, Г₁, and Г, is limited at 450 °C. Fe₂P is found to be in equilibrium with the ζ and δ phases. Fe₃P is found to be in equilibrium with δ, Г₁, Г, and αFe, respectively. Liquid Zn is in equilibrium with the Fe₂P and FeP phases.     

Oxide sublimation during the high-temperature oxidation of nickel alloys with protective coatings

It is shown that the oxidation of heat-resistant alloys is accompanied by a sublimation of the oxides MoO₃, WO₃, Al₂O₃, and CrO₃. The determinant in the sublimate is the molybdenum content, exceeding that in scale by a factor of 50–100. Protective coatings diminish the sublimation, rather than fully eliminate it. To diminish the molybdenum oxide sublimation decisively, it is expedient to alloy the coating with magnesium or magnesium oxide. Original Russian Text ? E.G. Ivanov, 2008, published in Fizikokhimiya Poverkhnosti i Zashchita Materialov, 2008, Vol. 44, No. 4, pp. 415–418.     

Electromagnetic and microwave absorbing properties of W-type barium ferrite doped with Gd<Superscript>3+</Superscript>

W-type barium ferrites doped with Gd3+,Ba1-xGdx(Zn0.3Co0.7)2Fe16O27(x = 0,0.05,0.10,0.15,0.20),were prepared by a sol-gel method.The effects of Gd3+ substitution on their microstructure,electromagnetic properties and microwave absorptive behavior were analyzed.The XRD patterns showed the single phase of W-type barium ferrite when x ≤ 0.15.Microwave electromagnetic properties of samples were studied at the frequency range from 2 GHz to 18 GHz using a network analyzer(Agilent 8722ET).The complex permittivity ...     

Solid-state phase equilibria in the Titanium-Aluminum-Nitrogen system

The 1273K isothermal section of the Ti-Al-N phase diagram was studied using modern methods of physical and chemical analyses. The data obtained by various techniques are in good agreement and in harmony with the results of thermodynamic calculations. It has been reliably established that AIN can coexist with TiN_1−x , Ti₂AIN, and TiAl₃; the ternary nitride Ti₂AIN can be in equilibrium with TiAl₃, AIN, TiAl₂, TiAl, TiN_1−x , and Ti₃AIN; the solid solution based on α(Ti) coexists with Ti₃Al, Ti₃AIN, TiN_1−x , and Ti₂N. Literature data on phase equilibria in the Ti-Al-N system were analyzed, and a 1273 K isothermal section of the phase diagram has been suggested.     

Scanning tunneling microscopic and scanning tunneling spectroscopic studies of nanostructure and surface energy properties of stainless steel Kh18N10T. 1. Measurements at interfaces with air and 0.01 N HCl solution

Stainless steel Kh18N10T is studied by electrochemical scanning tunneling microscopy (ESTM) and electrochemical scanning tunneling spectroscopy (ESCS) methods at the interface with air and for the fixed sample and probe potentials in 0.1 N HCl. Local spectral dependences of tunneling current on the tunneling voltage (I _t, U _t) are studied in either air or solution in the vicinity of potentials corresponding to stable properties. The local tunneling conductivity (G _o), the coefficient of the probability of tunneling transfer of an electron to the tip (α), and the logarithmic-dependence slope (β = U _t/ln(I _t) are calculated. As for Fe-Cr alloys, it is shown that at the atomic level, the local energy properties of a steel Kh18N10T are determined by the mutual effect of neighboring atoms (the matrix effect). Original Russian Text ? Yu.M. Stryuchkova, E.V. Kasatkin, 2008, published in Fizikokhimiya Poverkhnosti i Zashchita Materialov, 2008, Vol. 44, No. 5, pp. 464–471.     

Phase Equilibria,Crystal Chemistry and Physical Properties of Au-Ba-Ge Clathrates

In the Au-Ba-Ge system the clathrate type I solid solution, Ba₈Au _x Ge_46−x−y □ _y , extends at 800 °C from binary Ba₈Ge₄₃□₃ (□ is a vacancy) to Ba₈Au₆Ge₄₀. For the clathrate phase (1 ≤ x ≤ 6) cubic primitive symmetry (space group Pm[`3]n Pm{\bar{{3}}}n ) was confirmed by x-ray powder diffraction assisted by x-ray single crystal analyses of Ba₈Au_4.6Ge_40.3□_1.1. The lattice parameters of the solid solution show an almost linear increase with increasing gold content. Site preference from x-ray refinement shows that gold atoms preferably occupy the 6d site in random mixture with Ge and vacancies, which vanish at the solubility limit. Clathrate type ΙX (Ba₆Ge₂₅ type) has a maximum solubility of 2.7 at.% gold at 800 °C. Phase equlilibria at 800 °C are characterized by four ternary phases in the investigated region up to 33.3 at.% barium. The homogeneity range of Ba(Au_1−x Ge _x )₂ (AlB₂-type) and BaAu_1+x Ge_3−x has been established: Ba(Au_1−x Ge _x )₂ extends from BaAu_0.5Ge_1.5 to BaAu_0.9Ge_1.1 and BaAu_1+x Ge_3−x from BaAu_1.1Ge_2.9 (BaNiSn₃-type) to BaAu_2.7Ge_1.3 (Ce(Ni,Sb)₄-type). The crystal structures of two phases in the gold-rich part have been determined from single crystal x-ray data and were found to form new structure types: BaAu₃Ge with BaAu₃Ge-type (space group P4/nmm, a = 0.6459(2), c = 0.5487(2) nm) and BaAu_5+x Ge_2−x (x = 0, BaAu₅Si₂-type, space group Pnma, a = 0.8981(2), b = 0.7106(2) and c = 1.0363(2) nm), the latter revealing with increasing gold content a closely related derivative structure type (BaAu_5.3Ge_1.7, a = a_{\textBaAu5 \textSi2} ,  b = b_{\textBaAu5 \textSi2} ,  c = 2c_{\textBaAu5 \textSi2} a = a_{{{\text{BaAu}}_{5} {\text{Si}}_{2} }} ,\;b = b_{{{\text{BaAu}}_{5} {\text{Si}}_{2} }} ,\;c = 2c_{{{\text{BaAu}}_{5} {\text{Si}}{}_{2}}} ). Transport properties and particularly the thermoelectric behavior were studied for Ba₈Au₆Ge₄₀.     

Synthesis and Characterization of New Bismuth Lead Vanadate Pb<Subscript>2</Subscript>BiV<Subscript>3</Subscript>O<Subscript>11</Subscript>

It has been shown that BiVO₄ and Pb₂V₂O₇ react with each other, forming a new compound of the formula Pb₂BiV₃O₁₁ at molar ratio equal to 1:1. This compound has also been obtained from PbO, Bi₂O₃, and V₂O₅, mixed at a molar ratio of 4:1:3. It melts congruently at a temperature of 725 ± 5 °C and crystallizes in the triclinic system with unit-cell parameters: a = 0.710076 nm, b = 1.41975 nm, c = 1.42972 nm, α = 134.552°, β = 97.2875°, γ = 89.6083°, and Z = 4.     

Isothermal section at 1673 K of the Mo–Ru–Si diagram and crystallographic structures of ternary phases

Efforts to improve the high temperature behavior of MoSi₂ in oxidizing environments led to the investigation of the Mo–Ru–Si phase diagram. The isothermal section at 1673 K was determined by X-ray diffraction, optical and scanning electron microscopies and EPMA. Five new silicides were identified and their crystallographic structure was characterized using conventional and synchrotron X-ray as well as neutron powder diffraction. Mo₁₅Ru₃₅Si₅₀, denoted α-phase, is of FeSi-type structure, space group P2₁3, a=4.7535 (5) Å, D_x=7.90 g. cm⁻³, Bragg R=7.13. Mo₆₀Ru₃₀Si₁₀ is the ordered extension of the Mo₇₀Ru₃₀ σ-phase with space group P4₂/mnm, a=9.45940(8) Å, c=4.94273(5) Å, D_x=6.14 g. cm⁻³, Bragg R=5.75.     

Thermodynamic reassessment of the BaO-B2O3 system

The BaO-B₂O₃ pseudobinary system is assessed. A two-sublattice ionic solution model, (Ba²⁺) _P (O²⁻, BO₃³⁻, B₄O₇²⁻, B₃O_4.5) _Q , is adopted to describe the liquid phase. All the solid phases are treated as stoichiometric compounds. A set of parameters consistent with most of the available experimental data on both phase diagram and thermodynamic properties is obtained by using CALPHAD technique. A comparison between the calculated results and experimental data as well as a previous assessment is presented.     

Chronovoltammetry of the anodic dissolution of Ag-Au alloys in nitrate environments

A theory of quasi-reversible anodic chronovoltammetry of the selective dissolution of a homogeneous A-B alloy controlled by the solid-phase diffusion is proposed. The effects of the equilibrium solid-phase adsorption of the components and the roughness of the electrode surface with either homogeneously or statistically normally distributed microscopic irregularities of diverse kind on the shape of chronovoltammogram (the I _A current dependence on the η(t) overpotential) are successively taken into account. An expression for the I _{A, m} current at the voltammogram maximum, which is a generalization of the Randles-Sevik formula, is derived. A technique of estimating the recording-time boundaries of voltammograms, within which the surface roughness effect may be taken into account by simply multiplying the current by the roughness factor f _r , is founded. Outside the time interval, the I _A,m − ν^1/2 dependence (ν is the potential scanning rate), which is criterion for the diffusion kinetics, is shown to be substantially nonlinear. The diffusion-zone parameters (δ thickness and D _Ag heterodiffusion coefficient) obtained by processing the experimental data for Ag-Au alloys with a gold content of 15 or 20 at.% with the use of three models discussed are compared. Original Russian Text ? O.A. Kozaderov, V.V. Lozovskii, A.V. Vvedenskii, 2008, published in Fizikokhimiya Poverkhnosti i Zashchita Materialov, 2008, Vol. 44, No. 4, pp. 359–368.     

Sorption of Hg2+, Nd3+, Dy3+, and Uo 22+ ions at polysiloxane xerogels functionalized with phosphonic acid derivatives

The sorption properties of silicas with mono- and bifunctional surface layers containing the complexing fragment ≡Si(CH₂)₃NHP(S)(OC₂H₅)₂ were studied. It was found that xerogels synthesized by the solgel method (like mesoporous silicas obtained by the template method) can extract mercury(II) ions from acidified solutions (SSC up to 450 mg/g). In a nonporous xerogel with a bifunctional surface layer (≡P=S/-SH), thiol groups proved to be primary sorption sites for Hg²⁺ ions; part of the ligand groups were inaccessible to metal ions. Xerogels containing the phosphonic acid residues ≡Si(CH₂)₂P(O)(OH)₂ sorbed uranyl and lanthanide ions from their nitrate solutions. The resulting surface complexes contained two (for the UO₂²⁺ ion) or three innersphere ligand groups (for the Nd³⁺ and Dy³⁺ ions). The maximum SSCs were 340 mg/g for the uranyl ion and 120 mg/g for the lanthanide ions. Original Russian Text ? O.A. Dudarko, V.P. Goncharik, V.Ya. Semenii, Yu.L. Zub, 2008, published in Zashchita Metallov, 2008, Vol. 44, No. 2, pp. 207–212.     

Kinetics of forward extraction of Ti（IV） from H_2SO_4 medium by P_（507） in kerosene using the single drop technique

The kinetics of forward extraction of Ti(IV) from H2SO4 medium by P507 in kerosene has been investigated using the single drop technique.In the low concentration region of Ti(IV),the rate of forward extraction at 298 K can be represented by F(kmol·m-2·s-1)=10-5.07 [TiO 2 + ][H+]-1 [NaHA 2 ](o)·Analysis of the rate expression reveals that the rate determining step is(TiO)(i)2+ +(HA 2)(i)-[TiO(HA2)](i)+.The values of Ea,H±,S±,and G±298 are calculated to be 22 kJ·mol-1,25 kJ·mol-1,-218 J·mol-1·K-1,and 25 kJ·mol-1,respectively.The experimental negative S± values indicate that the reaction step occurs via SN2 mechanism.     

Surface tension and thermodynamic properties of liquid Ag-Bi solutions

With the maximum bubble pressure method, the density and surface tension were measured for five Ag-Bi liquid alloys (X _Bi=0.05, 0.15, 0.25, 0.5, and 0.75), as well as for pure silver. The experiments were performed in the temperature range 544–1443 K. Linear dependences of both density and surface tension versus temperature were observed, and therefore the experimental data were described by linear equations. The density dependence on concentration and temperature was derived using the polynomial method. A similar dependence of surface tension on temperature and concentration is presented. Next, the Gibbs energy of formation of solid Bi₂O₃, as well as activities of Bi in liquid Ag-Bi alloys, were determined by a solid-state electromotive force (emf) technique using the following galvanic cells: Ni, NiO, Pt/O ⁻²/W, Ag _X Bi _(1−X), Bi ₂ O _3(s). The Gibbs energy of formation of solid Bi₂O₃ from pure elements was derived: =−598 148 + 309.27T [J · mol⁻¹] and =−548 008 + 258.94T [J · mol⁻¹]; the temperature and the heat of the α → δ transformation for this solid oxide were calculated as 996 K and 50.14 J · mol⁻¹. Activities of Bi in the liquid alloys were determined in the temperature range from 860–1075 K, for five Ag-Bi alloys (X _Ag=0.2, 0.35, 0.5, 0.65, 0.8), and a Redlich-Kister polynomial expansion was used to describe the thermodynamic properties of the liquid phase. Using Thermo-Calc software, the Ag-Bi phase diagram was calculated. Finally, thermodynamic data were used to predict surface tension behavior in the Ag-Bi binary system.     

Surface tension and thermodynamic properties of liquid Ag-Bi solutions

With the maximum bubble pressure method, the density and surface tension were measured for five Ag-Bi liquid alloys (X _Bi=0.05, 0.15, 0.25, 0.5, and 0.75), as well as for pure silver. The experiments were performed in the temperature range 544–1443 K. Linear dependences of both density and surface tension versus temperature were observed, and therefore the experimental data were described by linear equations. The density dependence on concentration and temperature was derived using the polynomial method. A similar dependence of surface tension on temperature and concentration is presented. Next, the Gibbs energy of formation of solid Bi₂O₃, as well as activities of Bi in liquid Ag-Bi alloys, were determined by a solid-state electromotive force (emf) technique using the following galvanic cells: Ni, NiO, Pt/O ⁻²/W, Ag _X Bi _(1−X), Bi ₂ O _3(s). The Gibbs energy of formation of solid Bi₂O₃ from pure elements was derived: =−598 148 + 309.27T [J · mol⁻¹] and =−548 008 + 258.94T [J · mol⁻¹]; the temperature and the heat of the α → δ transformation for this solid oxide were calculated as 996 K and 50.14 J · mol⁻¹. Activities of Bi in the liquid alloys were determined in the temperature range from 860–1075 K, for five Ag-Bi alloys (X _Ag=0.2, 0.35, 0.5, 0.65, 0.8), and a Redlich-Kister polynomial expansion was used to describe the thermodynamic properties of the liquid phase. Using Thermo-Calc software, the Ag-Bi phase diagram was calculated. Finally, thermodynamic data were used to predict surface tension behavior in the Ag-Bi binary system.     

Gold complexes with

The reactions of methane with the gold complexes [Au(OH)]⁻, [Au(OCH₃)₄]⁻, [Au(O(CO)₂O₂]⁻ and [Au(O₂CH)₂]⁺, [Au^I(acac)], [Au^III(acac)₂]⁺ (acac-acetylacetonato) were studied using the DFT/PBE method with the SBK basis set. High activation barriers were obtained for the electrophilic substitution in [Au(OH)]⁻, [Au(OCH₃)⁴]⁻, [Au(O(CO)₂O)₂]-and [Au^III(acac)₂]⁺ complexes, which excludes the possibility that these reactions might proceed under mild conditions. The reactions of the [Au(HCO₂)₂]⁺ and [AuI(acac)] complexes with methane have rather low energy barriers and proceed through the formation of an intermediate complex. The alternative mechanism of methane oxidation with a gold complex in the presence of oxygen is simulated.