Coordination polymers with [Au(CN)4]- building blocks: a 1-d chain of molecular NiII2AuIII2 squares

A new coordination polymer utilizing the neglected cyanoaurate anion [Au(CN)₄]- building block is reported. Reaction of a Ni(II) salt, diethylenediamine (dien) and K[Au(CN)₄] yields Ni(dien)[Au(CN)4]₂, which consists of a unique bimetallic Ni(II)₂/Au(III)₂ supramolecular square through cis N(cyano) bridging of the [Au(CN)₄]- building block to [Ni(dien)]²⁺ cations. These squares further aggregate into a 1-D chain via Au-N(cyano) interactions; no Au(III)-Au(III) interactions are observed. Within the square, the magnetic coupling between the Ni(II) centres is very weak, indicating that the [Au(CN)₄]- unit is a poor mediator of magnetic exchange in this 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.     

Cyanide-bridged bimetallic multidimensional structures derived from organotin(IV) and dicyanoaurate building blocks: ion exchange, luminescence, and gas sorption properties

The recent success of using methyltin(IV) cations in constructing multidimensional structures containing the Au–CN–Sn link with interesting physical properties will be surveyed. The methyltin(IV)-dicyanoaurates, Me₃Sn[Au(CN)₂] (1) and Me₂Sn[Au(CN)₂]₂ (2) containing the Au–CN–Sn link can be easily prepared by aqueous reaction of Me₃SnCl or Me₂SnCl₂ with stoichiometric amounts of an aqueous solution of K[Au(CN)₂]. The room temperature solid-state emission spectrum of 1 excited at 254 nm shows two intense emission bands at 442 and 670 nm, and a shoulder at 390 nm. When excited at 320 nm, the crystalline sample shows two intense emission bands at 442 and 720 nm, and a shoulder at 380 nm. After 2 min of grinding, only the blue emission band at 442 nm is observed. In contrast, the emission spectrum of 2 shows only one emission maximum at 422 nm. The porosity of 1 and 2 was probed by gas sorption measurements performed at 77 K. 1 exhibited no detectable microporosity as revealed by the inspection of the N₂, H₂, as well as, O₂ isotherms. The gas adsorption studies reveal that only a small amount of N₂ and H₂ (3.82 and 4.66 cm³ g⁻¹, respectively) is adsorbed by the framework of 2 at 77 K. However, a CO uptake of 11.20 cm³ g⁻¹ can be reached at 1 atm. The framework of 2 can take up significant amounts of O₂ (23.27 cm³ g⁻¹). In addition to intriguing photoluminescence and gas sorption behavior, these complexes also exhibit ion exchange properties in the presence of bivalent transition metal cations, such as cobalt(II), nickel(II), copper(II), and zinc(II).     

A spectroscopic and electrochemical investigation of the oxidation pathway of glycyl-d,l-methionine and its N-acetyl derivative induced by gold(III)

The ¹H nuclear magnetic resonance spectroscopy was applied to study the reaction of the dipeptide glycyl-d,l-methionine (H-Gly-d,l-Met-OH) and its N-acetylated derivative (Ac-Gly-d,l-Met-OH) with hydrogen tetrachloridoaurate(III) (H[AuCl₄]). The corresponding peptide and [AuCl₄]^– were reacted in 1:1, 2:1, and 3:1 molar ratios, and all reactions were performed at pD 2.45 in 0.01 M DCl as solvent and at 25°C. It was found that the first step of these reactions is coordination of Au(III) to the thioether sulfur atom with formation of the gold(III)-peptide complex [AuCl₃(R-Gly-Met-OH-S)] (R=H or Ac). This intermediate gold(III) complex further reacts with an additional methionine residue to generate the R-Gly-Met-OH chlorosulfonium cation as the second intermediate product, which readily undergoes hydrolysis to give the corresponding sulfoxide. The oxidation of the methionine residue in the reaction between H-Gly-d,l-Met-OH and [AuCl₄]^– was five times faster (k ₂ = 0.363 ± 0.074 M^-1s^-1) in comparison to the same process with N-acetylated derivative of this peptide (k ₂ = 0.074 ± 0.007 M^-1s^-1). The difference in the oxidation rates between these two peptides can be attributed to the free terminal amino group of H-Gly-d,l-Met-OH dipeptide. The mechanism of this redox process is discussed and, for its clarification, the reaction of the H-Gly-d,l-Met-OH dipeptide with [AuCl₄]^– was additionally investigated by UV-Vis and cyclic voltammetry techniques. From these measurements, it was shown that the [AuCl₂]^– complex under these experimental conditions has a strong tendency to disproportionate, forming [AuCl₄]^– and metallic gold. This study contributes to a better understanding of the mechanism of the Au(III)-induced oxidation of methionine and methionine-containing peptides in relation to the severe toxicity of anti-arthritic and anticancer gold-based drugs.     

Two dication salts of ET: preparation and crystal structures of ET [FeII(CN)4(CO)2]

Single crystals of new dication bis(ethylenedithio)tetrathiafulvalene salts with [Fe^II(CN)₄(CO)₂]²⁻ were prepared electrochemically. Two kind crystals (A and B) with the same composition and different stacking patterns were derived from Na₂[Fe^II(CN)₄(CO)₂] and TBA₂[Fe^II(CN)₄(CO)₂], respectively.     

电子工业废水中酒石酸铜的配位构型（英文）

采用紫外可见光谱(UV-Vis)和液相色谱/质谱(LC-MS)分析酒石酸铜(Cu-TA)配合物的配位结构,并通过密度泛函理论(DFT)计算系统地揭示酒石酸铜在水溶液中的有效配位构型和电子特性。UV-Vis在230和255 nm处的Job图一致显示可能存在[Cu(TA)]和[Cu(TA)₂]^2-。LC-MS结果证实单配位和高配位配合物[Cu₂(TA)₂]⁺、[Cu(TA)₂]⁺和[Cu₂(TA)₃(H₂O)₂(OH)₂]²⁺的存在。DFT计算结果表明,酒石酸(TA)的羧基氧和羟基氧是Cu(Ⅱ)的优选配位位点。[Cu(TA)](酒石酸分子1号碳的羟基氧和3号碳的羟基氧与Cu(Ⅱ)配位)、[Cu(TA)₂]^2-(2个酒石酸分子1号碳的羧基氧和2号碳的羟基氧与Cu(Ⅱ)...     

Two Cd(II) coordination polymers based on asymmetrical Schiff-base ligand with five- and six-membered N-containing heterocyclic rings: Synthesis,crystal structures and luminescent properties

Two cadmium inorganic–organic hybrid coordination polymers [CdL(SCN)₂]_n (1) and [CdLI₂]_n (2), have been synthesized and characterized by IR spectroscopy, elemental analysis, XRPD, thermogravimetric (TG) analyses and X-ray crystallography, where L is 4-(pyridine-4-yl)methyleneamino-1,2,4-triazole. Asymmetrical Schiff-base ligand L acts as a bidentate bridging ligand to bind two Cd(II) centers through two terminal N_triazolyl and N_pyridyl donors in polymers 1 and 2. Polymer 1 displays a new 3D inorganic–organic hybrid network generated through the coordination interactions between Cd-(1,3-μ-SCN⁻) 2D inorganic sheets and bidentate bridging ligands. The structure of polymer 2 is a 3D chiral supramolecular framework which contains helical chains on 2₁ axis. Each Cd(II) center is coordinated by two ligands and two I⁻ donors to attain a distorted tetrahedral environment. The luminescent properties of polymers 1 and 2 were investigated in the solid state at room temperature.     

Kinetic Parameters and Mechanism of Gold Electrooxidation in Thiocarbamide Solutions

Kinetics and mechanism of gold electrooxidation in sulfuric acid solutions of thiocarbamide (TCA) are studied by measuring voltammograms (VA) of gold and glassy carbon (GC) electrodes. In a potential (E) range from –0.2 to 1.2 V (SCE), VA of a gold electrode demonstrate three peaks. The first and the second peaks correspond to gold electrooxidation to [AuTCA_ads] + and [Au(TCA_ads)₃]³⁺ ions at E of 0.152 and 0.554 V, while the third one corresponds to TCA electrooxidation. The electrooxidation of TCA on GC electrodes is characterized by two VA peaks at 0.983 and 1.437 V. The first peak corresponds to the formation of formamidine disulfide (FADS) (k _a1 = 6.40 × 10^–4 cm/s), while the second peak corresponds to TCA oxidation to sulfides and hydrosulfides (k _a2 = 7.78 × 10^–5 cm/s). The composition of adsorption layers formed at the Au electrode is analyzed by Auger spectroscopy. The introduction of sodium sulfide into TCA solutions eliminates the formation of adsorption layers and accelerates Au oxidation in such solutions. The rate constants of gold electrooxidation k _a = 6.31 × 10^–3 cm/s and Au(I) electroreduction k _c = 5.46 × 10^–4 cm/s in TCA solutions are estimated. Kinetic parameters (charge transfer coefficients, reactions orders in carbamide) are determined and the mechanisms of Au and TCA oxidation in sulfuric acid solutions are proposed.__________Translated from Zashchita Metallov, Vol. 41, No. 3, 2005, pp. 316–325.Original Russian Text Copyright © 2005 by Kozin, Kozina, Bogdanova.     

Factors affecting luminescence and aurophilicity on digold(I) complexes and their potential as cation probes

In the last few years we have analysed the factors that affect the structures and luminescence properties of Au(I) compounds, specifically in relation with the presence of aurophilic contacts and their application as cation probes. EXAFS studies have allowed us to obtain for the first time direct structural data of dissolved Au(I) compounds. An overview of the work reported to date is presented here. The optical properties of complex [Au₂Cl₂(μ-dpephos)] (dpephos =bis(2-diphenylphosphino) phenylether, 1) have been revisited and new results are now included. New aspects on the use of the complexes as Ag(I) probes are also discussed.     

Structural and magnetic properties of metal complexes constructed by pyridine-2,6-dicarboxylate and 5-(4-bromophenyl)-2,4′-bipyridine

Pyridine-2,6-dicarboxylic acid reacts as the first ligand (L1) under hydrothermal conditions with different metal ions such as Co^II, Ni^II, and Cu^II to form two 1D polymeric complexes [M(L1)(L2)₂·H₂O]_n (M = Co²⁺ or Ni²⁺) and a tetranuclear cluster with formula [Cu₄(L2)₄(L1)₄]·2H₂O in the presence of 5-(4-bromophenyl)-2,4′-bipyridine as the second ligand (L2). Intramolecular interactions were observed in the three compounds, being antiferromagnetic in both cobalt and nickel 1D coordination polymers and ferromagnetic interaction in the tetranuclear copper cluster.     

Study on the boundary structures in a series of lanthanide hexacyanoferrate(III) n-hydrates

The properties of a series of lanthanide hexacyanoferrate(III) n-hydrates were studied by means of thermal analysis, IR spectroscopy, Raman spectroscopy and X-ray crystallography. Thermal analyses showed that there were two kinds of complexes in this series, Ln[Fe(CN)₆]·5H₂O (Ln=La–Nd) and Ln′[Fe(CN)₆]·4H₂O (Ln′=Sm–Lu). The boundary complex between them was Nd[Fe(CN)₆]·5H₂O. The IR spectra of the two kinds of complexes were obviously different. For the pentahydrates, there were two sharp CN stretching bands at 2050 and 2140 cm⁻¹, and one band at 1600 cm⁻¹ assigned to the HOH bending. On the other hand, for the tetrahydrates besides the two CN stretching bands at 2050 and 2140 cm⁻¹, a new band was observed at 1940 cm⁻¹, and the HOH bending band split into three bands around 1600 cm⁻¹. From the X-ray crystal analysis, the structure of the boundary complex Nd[Fe(CN)₆]·5H₂O was determined. It belonged to hexagonal, P6₃/m, with a=7.467(2) Å, c=13.793(3) Å and Z=2 (R=0.082, R_w=0.126). Neodymium was nine-coordinated in the form of the NdN₆(H₂O)₃ group. The three coordinated water molecules of the 5H₂O complex with Nd have a large value for the equivalent isotropic thermal parameter. One of the three water molecules was dissociated easily and the 5H₂O complex changed into the stable 4H₂O complex with Nd. The crystal of the 4H₂O complex is orthorhombic, and belongs to the space group Cmcm as well as the other Ln[Fe(CN)₆]·4H₂O (Ln=Sm–Lu). Therefore, the structure of Nd[Fe(CN)₆]·5H₂O is regarded as the boundary structure.     

Electroless synthesis of nano-structured gold particles using conducting polymer nanoparticles

In this study, gold nanoparticles were synthesized by electroless recovery of [AuCl₄]⁻ from an acidic aqueous solution using nano-structured conducting polymer, polypyrrole nanoparticles, as active surface. The formation of gold nanoparticles was confirmed by TEM, SEM and EDX measurements. The effects of the initial Au(III) concentration on the gold uptake was examined. The recovery capability and gold particle morphology prepared from polypyrrole nanoparticle were compared to that from cast PPy film counterpart.     

Sensing behavior of silica-coated Au nanoparticles towards nitrobenzene

In the present work, we report silica-stabilized gold nanoparticles (SiO₂/Au NPs) as a wide-range sensitive sensing material towards nitrobenzene (NB). Surface hydroxyl groups of silica selectively form Meisenheimer complex with electron-deficient aromatic ring of NB and facilitate its immobilization and subsequent catalytic reduction by Au cores. Silica-coated Au NPs were synthesized and characterized for their chemical, morphological, structural, and optical properties. SiO₂/Au NPs-modified electrodes were characterized with impedometric and cyclic voltammetric electrochemical techniques. SiO₂/Au NPs are found to have a higher optical detection window of range, 0.1 M to 1 μM and a lower electrochemical detection window of range, 10⁻⁴ to 2.5 × 10⁻² mM with a detection limit of 12.3 ppb. A significant enhancement in cathodic peak current, C ₁, and sensitivity (102 μA/mM) was observed with modified electrode relative to bare and silica-modified electrodes. The I _P was found to be linearly co-related to NB concentration (R ² = 0.985). The interference of cationic and anionic species on sensor sensitivity was also studied. Selectivity in the present sensing system may be further improved by modifying silica with specific functional moieties.     

Effect of alloy formation in Ag?Au system on electrical double layer structure and hydrogen evolution kinetics

The variations of the zero-charge potential, specific surface charge, and free interface energy in the Ag−Au|F⁻(H₂O) system are studied with the use of impedance measurements in a wide range of alloy compositions. In terms of the concept of a finitely thick interface layer, a theoretical isotherm of the surface composition of the alloy, i.e., the concentration dependence of the activity coefficients of the components is plotted. It is shown that, in Ag−Au alloys at 298 K, gold is surface active, apparently, due to its higher hydrophilicity. The exchange current of the overall reaction of hydrogen evolution on Ag−Au alloys from aqueous sulfuric-acid solutions depends nonlinearily on the surface concentration of gold.     

New BETS salt with the square planar [Ni(CN)4]2− anion

The new radical cation salt based on bis(ethylenedithio)tetraselenafulvalene (BETS) with the square planar [Ni(CN)₄]²⁻ anion was synthesized by electrocrystallization: (BETS)₄·Ni(CN)₄. X-ray analysis, electron transport, magnetotransport and electronic band structure calculations are presented and discussed.     

Solid state electrical conductance properties of some new bimetallic salts and heterometallic coordination polymers derived from bis (1-ethoxycarbonyl-1-cyanoethylene-2,2-dithiolato) cuprate(II) ion

This paper describes the solid state conductivity of the salt [n-Bu₄N]₂[Cu(ecda)₂], bimetallic salts of the type, [M(diimine)₃][Cu(ecda)₂] and heterobimetallic coordination polymers, Pd[Cu(ecda)₂] and Ag₂[Cu(ecda)₂] (M=Fe(II), Co(II), Ni(II), or Cd(II); diimine=1,10-phenanthroline (phen) or ethylenediamine (en) and ecda²⁻=1-ethoxycarbonyl-1-cyanoethylene-2,2-dithiolate) that have been synthesized and investigated using molecular spectroscopies. A unique feature of [n-Bu₄N]₂[Cu(ecda)₂], Pd[Cu(ecda)₂] and Ag₂[Cu(ecda)₂] is the complete quenching of paramagnetism showing the presence of strongly antiferromagnetically coupled copper(II) centres at room temperature. Temperature dependent compressed pellet conductivities of the complexes have been determined in the temperature range 303–373 K. All the complexes exhibited σ_rt in 10⁻¹¹–10⁻⁷ S cm⁻¹ range. The complexes [n-Bu₄N]₂[Cu(ecda)₂], [Fe(phen)₃]-[Cu(ecda)₂], Pd[Cu(ecda)₂] and Ag₂[Cu(ecda)₂] are semiconductors as their conductivity increases with the increase in temperature, with E_a=0.03–4.70 eV.     

Spectral and adsorption characteristics of Au(III) and Au(0) composite materials

The adsorption of HAuCl₄ chloroauric acid on silica modified with γ-aminopropyltriethoxysilane (aminosilica) and on aluminum oxide is studied. Diffuse-scattering spectra of these Au(III) composite materials and their reduced Au(0) composites are recorded in the visible and infrared spectral ranges. Au(III) composites are selective with respect to the adsorption of phenylacetylene (PA) from octane due to the formation of π-complexes with Au(III). Au(III)-aluminum oxide composite material has a much larger capacity for PA adsorption than does aminosilica composite with the same gold content. The formation of coordination bonds between free aminopropyl groups of the silica carrier and gold atoms prevents PA adsorption. The formation of such bonds is manifested in a shift in λ_max of the spectral line from 408 to 522 and 546 nm with a decrease in [Au(III)] concentration from 400 to 120 and 60 μmol/g. The decrease in the intensity and the red shift of the absorption bands of NH₂ stretching vibrations in the infrared spectra of the specimen upon modification also confirms the supposition. There are absorption bands of free hydroxyl radicals, but no band of bound radicals in the infrared spectra of Au(0) composites. The electronic spectra (λ_max = 511, 504, and 512 nm) are close for all three specimens that differ in gold content, which means that the sizes of immobilized Au(0) nanoparticles are similar. Upon the sorption of HAuCl₄ on a Au(III)-aluminum oxide specimen, the absorption band of surface OH groups disappears, however, in Au(0) composite, it appears again near 3105 cm^?1.     

电镀软金用硫基无氰金配合物电解质研究进展

电镀金工艺中金氰化物([Au(CN)2]-)溶液在过程中会释放出剧毒的游离氰化物离子,严重危害到生产人员和自然环境的健康;此外,它们还会对光刻胶造成一定的破坏.近年来无氰电解质得到了发展.基于对50余篇文献的分析,本文比较了亚硫酸金([Au(SO3)2]3-)、硫代硫酸金([Au(S2O3)2]3-)和二者混合电解液,...     

New organic metal (BEDO-TTF)4Pt(CN)4·H2O

A new charge transfer salt of (BEDO-TTF)₄Pt(CN)₄·H₂O (BEDO-TTF = bis(ethylenedioxo)tetrathiafulvalene) composition has been prepared. X-ray analysis shows that the conducting donor layers of new θ″-type packing alternate with anion sheets composed of [Pt(CN)₄]⁻² anions, which are associated with H₂O molecules via hydrogen bonds. Temperature and magnetic field dependences of the resistance are presented.     

Long-range magnetic order displayed by a bimetallic pentanuclear cluster complex [(Ni(2,2′-bipy)2)3(Fe(CN)6)2]·13H2O and by a Cu(II) analog

A bimetallic pentanuclear cluster complex contains three bis(2,2′-bipyridine)nickel(II) moieties bridged, through two vacant cis-positions around each nickel, to two separate hexacyanoferrate(III) groups via NiNCFe linkages. Freshly prepared crystals of this compound contain 17 water and two dimethylformamide molecules of solvation per cluster. Loss of some solvent molecules is rapid in air, the resulting ‘partly desolvated’ material showing intracluster ferromagnetic coupling and a S=4 ground state, but without long-range magnetic order. In contrast, a rapidly precipitated powder sample, containing 13 waters of hydration [(Ni(2,2′-bipy)₂)₃(Fe(CN)₆)₂]·13H₂O, displays long-range order at a T_C of 11 K. Inter-cluster interactions occur via the H-bonded water pathways which join neighbouring Fe(CN)₆³⁻ groups in separate clusters. Thus, a new example of inter-cluster magnetic ordering has been achieved. A copper(II)-bipy analog also shows long-range order, with T_C of 13 K. In the absence of a crystal structure, the magnetic and spectral properties of this Cu derivative point to a different structural topology being present.