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1.
Pyridine Adducts of the Gold Halides. 1. Synthesis and Structure of [Hpy][AuCl4], AuC13 · py, [AuCl2(py)2]Cl · H2O, and [AuCl2(py)2] [AuCl2] HAuCl4 reacts with pyridine in aqueous solution to form sparingly soluble [Hpy] [AuCl4]. This goes into solution as [AuCl2(py)2]+ on adding an excess of pyridine. [Hpy][AuCl4] decomposes above 195°C to HCl and AuCl3 · py, which can also be obtained from NaAuCl4 and pyridine. AuCl2 · py is formed by the reaction of AuCl2 · S(CH2C6H4)2 with pyridine in CHCl3. According to the vibrational spectrum the complex is built up of trans[AuCl2(py)2]+ cations and [AuCl2]? anions. The IR spectra of [Hpy][AuCl4], AuCl3 · py, and [AuCl2(py)2]Cl · H2O are discussed and assigned with respect to the crystal structures. [Hpy][AuCl4] crystallizes monoclinic in the space group C2/m. In its structure alternating layers of [Hpy]+ cations and [AuCl4]? anions are observed. The monoclinic AuCl3 · py (space group C2/c) consists of molecular complexes, wherein the gold atom is surrounded by three Cl atoms and one pyridine molecule in a square planar arrangement. The coordination is completed to an elongated octahedron by two more distant Cl atoms of neighbouring complexes. [AuCl2(py)2]Cl · H2O crystallizes in the monoclinic space group P21/n. It forms planar trans[AuCl2(py)2]+ cations, weakly coordinated with an additional Cl? ion and one H2O molecule. The Au? Cl bond lengths in the complexes under investigation are in the range of 227 to 229 pm, the Au? N distances are between 197 and 199 pm.  相似文献   

2.
The first salt‐like compounds of dications with [AuCl4] anions are reported. The compounds Zn[AuCl4]2 · (AuCl3)1.115 ( 1 ) and Cd[AuCl4]2 ( 2 ) are obtained from reactions of MCl2 (M = Zn, Cd) and elemental gold in liquid chlorine at ambient temperature under autogenous pressure and subsequent annealing at 230 °C. The structure of 1 represents an incommensurately modulated composite [superspace group C2/c(α0γ)0s] built of two subsystems. The first subsystem contains chains of zinc(II) tetrachloridoaurate(III), which feature a slightly distorted octahedral coordination of Zn and can be described by the Niggli formula 1{Zn[AuCl4]1/1[AuCl4]2/2}. The second subsystem consists of Au2Cl6 molecules, which are located in channels built up by the first subsystem. The structural parameters of the hosted Au2Cl6 molecules show only small deviations from neat AuCl3. The crystal structure of Cd[AuCl4]2 ( 2 ) consists of chains built of Cd2+ ions coordinated by bridging [AuCl4] anions and alternating Cd‐Au sequence. Cd has a distorted octahedral coordination environment.  相似文献   

3.
The simple, fast and highly sensitive anodic stripping voltammetric detection of As(III) at a gold (Au) nanoparticle‐modified glassy carbon (GC) (nano‐Au/GC) electrode in HCl solution was extensively studied. The Au nanoparticles were electrodeposited onto GC electrode using chronocoulometric technique via a potential step from 1.1 to 0 V vs. Ag|AgCl|NaCl (sat.) in 0.5 M H2SO4 containing Na[AuCl4] in the presence of KI, KBr, Na2S and cysteine additives. Surfaces of the resulting nano‐Au/GC electrodes were characterized with cyclic voltammetry. The performances of the nano‐Au/GC electrodes, which were prepared using different concentrations of Na[AuCl4] (0.05–0.5 mM) and KI additive (0.01–1.0 mM) at various deposition times (10–30 s), for the voltammetric detection of As(III) were examined. After the optimization, a high sensitivity of 0.32 mA cm?2 μM?1 and detection limit of 0.024 μM (1.8 ppb) were obtained using linear sweep voltammetry.  相似文献   

4.
The synthesis and crystal structures of two novel semicarbazones and four gold(III) compound derivatives of these semicarbazones are presented. A pattern in the formation of the semicarbazones shows the association of Cl ions held together by intra- and intermolecular forces. [AuCl4]? and [AuBr4]? anions are co-crystallised with these semicarbazone ligands, and the packing architectures revealed by a single-crystal X-ray diffraction analysis showed the different influences of the anions and the association of these chemical species by intermolecular forces on the crystal packing. Crystal engineering led to gold(III) compounds that are stabilised by relevant hydrogen bonding networks, which demonstrated their importance to the supramolecular organisation of the studied compounds. Interestingly, Cl???Br interactions are observed and contribute to the formation of the supramolecular structures. Elemental analysis data and spectroscopic properties in the solid state and solution are also described.  相似文献   

5.
Reactions of freshly precipitated binuclear zinc dimethyldithiocarbamate with [AuCl4]? anions in 2 M HCl were studied. The heteropolynuclear complex [Au2{S2CN(CH3)2}4][ZnCl4] (I) and the polymeric heterovalent complex ([Au{S2CN(CH3)2}2][AuCl2]) n (II) were preparatively isolated from the chemisorption system [Zn2{S2CN(CH3)2}4]-Au3+/2 M HCl. The products were characterized by 13C MAS NMR data and by X-ray diffraction determination of crystal and molecular structures. The principal structural units of compounds I and II are the tetragonal planar complex cations [Au{S2CN(CH3)2}2]+ (in which the complex-forming ion coordinates two MDtc ligands in the S,S′-bidentate mode) and the anions, namely, the distorted tetrahedral anion [ZnCl4]2? in I and the linear [AuCl2]? anion in II. The further structural self-organization of complexes at the supramoleular level occurs through relatively weak secondary bonds Au?S and Au?Cl. The chemisorption capacities of zinc dimethyldithiocarbamate calculated from gold(III)-binding reactions are 644.1 and 1288.2 mg of gold per gram of the sorbent. Simultaneous thermal analysis studies of the thermal behavior of I and II were used to elucidate the conditions of gold recovery.  相似文献   

6.
The unique physico-chemical properties of gold nanoparticles portrayed in their chemical stability, the size-dependent electrochemistry, and the unusual optical properties make them suitable modifiers of various surfaces used in the fields of optical devices, electronics, and biosensors. In this work we present two different methods to obtain metallic gold nanoparticles at a liquid–liquid interface, and to control their growth by adjusting the experimental conditions. Decamethylferrocene (DMFC), used as an oxidizable compound dissolved in an organic solvent that is spread as a thin film on the surface of graphite electrode, serves as a redox partner to exchange electrons across the liquid–liquid interface with the other redox counter-partner [AuCl4]? present in the conjoined water phase. The interfacial electron transfer between the DMFC and the [AuCl4]? ions leads to deposition of metallic gold nanoparticles at the liquid–liquid interface. The structure and features of the deposited Au nanoparticles were studied by means of microscopic and voltammetric techniques. The morphology of the Au deposit depends on the concentration ratio of redox partners and both electrode and liquid–liquid interfacial potential differences. Depending on whether the Au deposit was obtained by ex situ (at open circuit potential) or by “in situ” (by cycling of the electrode potential) approach, we observed quite different effects to the ion transfer reactions probed by the thin-film electrode set-up. The possible reasons for the different behavior of the Au nanoparticles are discussed in terms of the structure and the properties of the obtained Au deposit. In separate experiments, we have demonstrated catalytic effects of the Au nanoparticles towards enhancing the electron transfer between DMFC and two aqueous redox substrates, hexacyanoferrate and hydrogen peroxide.  相似文献   

7.
The effect of nonionic micelles of Triton X‐100 on the oxidative decarboxylation of l ‐glutamic acid by chloroaurate(III) complexes has been investigated in acetate buffer medium. The reaction is first order with respect to Au(III), but a complex order with respect to glutamate. H+ ion has both accelerating and retarding effects in the pH range 3.72–4.80, whereas a Cl? ion has an inhibiting effect in the range 0.02–0.56 mol dm?3. Under the experimental conditions, AuCl?4 and AuCl3(OH)? are the predominant and effective oxidizing species, whereas the zwitterion (H2A) and mononegative anion (HA?) are the predominant reducing species of the amino acid. The reaction involves a one‐step two‐electron transfer process and passes through the intermediate formation of iminic cation. In the presence of surfactant, the reaction passes through a maximum and it appears to follow Berezin's model, where both the oxidant and the substrate are partitioned between the aqueous and the micellar phase and then react. The binding constants between the reactants and the surfactant have been evaluated at different temperatures. Compensation between substrate–water interaction and substrate–micelle interaction plays an important role in such redox reactions in the presence of a surfactant. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 482–493, 2012  相似文献   

8.
Cationic-anionic chloride complexes of gold(III), [(L)AuCl2]BF4 (L = 2,2??-bipyridine and 1,10-phenanthroline (Phen)), are synthesized. Their reactions and the reactions of complex [(Phen)AuCl2]Cl with silver(I) and sodium acetates are studied. The chloride ligands in complexes [(L)AuCl2]BF4 are easily substituted by the acetate ligands in the reaction with silver(I) acetate to form new carboxylate complexes [(L)Au(OAc)2]BF4. The reaction of complex [(Phen)AuCl2]Cl with sodium acetate in glacial acetic acid affords binary complex salt [(Phen)AuCl2][AuCl4], which is characterized by single-crystal X-ray diffraction analysis.  相似文献   

9.
The interaction of binuclear cadmium dialkyldithiocarbamates [Cd2(S2CNR2)4] with solutions of AuCl3 in 2M HCl gives polynuclear gold(III) complexes ([Au(S2CNR2)2][AuCl4]) n , where R = C4H9 (I) and R2 = (CH2)5 (II). The structures of the synthesized compounds solved by X-ray diffraction analysis are char-acterized by a complicated organization at the supramolecular level. The structures are based on polymer chains (I) and layers (II) involving isomeric cations [Au(S2CNR2)2]+ and anions [AuCl4]. The thermal behavior of the synthesized complexes is studied by simultaneous thermal analysis including thermogravimetry and differential scanning calorimetry. The final product of the thermal transformations of the studied complexes is shown to be reduced metallic gold.  相似文献   

10.
Summary The kinetics of the reaction between nitrous acid and gold(III) in an HCl medium was studied. The reaction was first order with respect to [AuIII] and [HNO2]·H+ and Cl- ions inhibit the rate and alkali metal ions have specific effects on the rate. The reaction appears to involve different gold(III) species, viz. AuCl inf4 sup– , AuCl3(OH2) and AuCl3(OH), which undergo a two-equivalent reduction to gold(I) leading to the formation of NO inf2 sup+ which under-goes rapid hydrolysis to give nitric acid.  相似文献   

11.
We study the interaction of dialkyl substituted and cyclic cadmium dithiocarbamates with [AuCl4]? anions in 2M HCl medium. The state of the chemisorbents upon contact with AuCl3 solutions is controlled by 113Cd MAS NMR spectroscopy. The result of the heterogeneous reactions involving chemisorption binding of gold(III) from the solutions and partial ion exchange is the formation of heteropolynuclear gold(III)-cadmium complexes. The crystal and molecular structure of the acetone-solvated form of polymeric bis-(N,N-diethyldithiocarbamato-S,S′) gold(III) hexachlorodicadmate is identified by single-crystal XRD. The main structural moieties of the compound are complex [Au{S2CN(C2H5)2}2]+ cations and [Cd2Cl6]2? anions. The structural self-organization of the complex at the supramolecular level is attributed to the secondary Au…S bonds between neighboring isomeric complex gold(III) cations; the bonding results in the formation of linear polymer ([Au{S2CN(C2H5)2}2]+) n chains, with [Cd2Cl6]2? anions alternating to the right and left of the chains.  相似文献   

12.
The formation of binary complex salts containing gold(III) in the cation and palladium(II) in the anion in the systems [(Bipy)AuCl2]+-[PdCl4]2? occurs by transfer of the N,N-electron-donating chelating ligand bipyridine and the chloride ligands between the gold-containing cation and the palladium-containing anion. The resulting neutral salt [(Bipy)PdCl2] crystallizes together with the anion [AuCl4]? from acetonitrile-water (1 : 1-1 : 2, v/v) to give the complex salt (NH 4 + )0.20[(Bipy)AuCl 2 + ]1.04[(Bipy)PdCl2]0.96[AuCl 4 ? ]0.76PdCl 4 2? ]0.24 with a total Au : Pd ratio of 3 : 2. The ammonium cation is formed from acetonitrile upon its hydrolysis most likely catalyzed by Pd complexes. Quantum-chemical calculations were performed to study the transfer of the chelating ligand theoretically.  相似文献   

13.
Gold nanoparticles were prepared in surfactant solutions by reduction of HAuCl4 under UV irradiation without adding extra reductants or other organic substances. The effect of the structure and the property of surfactant on the size and the optical properties of prepared gold nanoparticles were studied. It was found that the longer the alkyl chain of the surfactant, the larger gold particles are obtained. On the other hand, lengthen the geminis spacer benefits the formation of smaller gold particles. The formation of adduct micelles composed of the charged surface active portion of the surfactant molecule and the (AuIIICl4) ion in cationic surfactant solution serves as the gold source and favors the formation of gold particles with larger sizes. While the repulsion between the (AuIIICl4) ion and the negative charged surface of anionic surfactant micelle is in favor of the formation of gold nanoparticles with smaller sizes. The nonionic surfactants can also assist the formation of dispersed gold nanoparticles.  相似文献   

14.
Diffraction‐quality single crystals of two gold(I) complexes, namely bis(1,3‐dimesityl‐4,5‐naphthoquinoimidazol‐2‐ylidene)gold(I) chloride benzene monosolvate, [Au(C29H26N2O2)2]Cl·C6H6 or [(NQMes)2Au]Cl·C6H6, 2 , and bis(1,3‐dimesityl‐4,5‐naphthoquinoimidazol‐2‐ylidene)gold(I) dichloridoaurate(I) dichloromethane disolvate, [Au(C29H26N2O2)2][AuCl2]·2CH2Cl2 or [(NQMes)2Au][AuCl2]·2CH2Cl2, 4 , were isolated and studied with the aid of single‐crystal X‐ray diffraction analysis. Compound 2 crystallizes in a monoclinic space group C2/c with eight molecules in the unit cell, while compound 4 crystallizes in the triclinic space group P with two molecules in the unit cell. The crystal lattice of compound 2 reveals C—H…Cl? interactions that are present throughout the entire structure representing head‐to‐tail contacts between the aromatic (C—H) hydrogens of naphthoquinone and Cl? counter‐ions. Compound 4 stacks with the aid of short interactions between a naphthoquinone O atom of one molecule and the mesityl methyl group of another molecule along the a axis, leading to a one‐dimensional strand that is held together by strong π–η2 interactions between the imidazolium backbone and the [AuCl2]? counter‐ion. The bond angles defined by the AuI atom and two carbene C atoms [C(carbene)—Au—C(carbene)] in compounds 2 and 4 are nearly rectilinear, with an average value of ~174.1 [2]°. Though 2 and 4 share the same cation, they differ in their counter‐anion, which alters the crystal lattice of the two compounds. The knowledge gleaned from these studies is expected to be useful in understanding the molecular interactions of 2 and 4 under physiological conditions.  相似文献   

15.
The kinetics of the reaction between glycolaldehyde (GA) and tetrachloroaurate(III) in acetic acid-sodium acetate buffer has been studied. The reaction is first-order with respect to [AuIII] as well as [GA]. Both H+ and Cl ions retard the rate of reaction. AuCl4, AuCl3(OH2), and AuCl3(OH) are the reactive species of gold(III) with gradually increasing reactivity. A reaction mechanism involving two-electron transfer rate determining steps has been proposed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 613–619, 1998  相似文献   

16.
The analysis of 17O NMR transverse relaxation rates and EPR transverse electronic relaxation rates for aqueous solutions of the four DTPA‐like (DTPA = diethylenetriamine‐N,N,N,N″,N″‐pentaacetic acid) complexes, [Gd(DTPA‐PY)(H2O)]? (DTPA‐PY = N′‐(2‐pyridylmethyl)), [Gd(DTPA‐HP)(H2O)2]? (DTPA‐HP = N′‐(2‐hydroxypropyl)), [Gd(DTPA‐H1P)(H2O)2]? (DTPA‐H1P = N′‐(2‐hydroxy‐1‐phenylethyl)) and [Gd(DTPA‐H2P)(H2O)2] (DTPA‐H2P = N′‐(2‐hydroxy‐2‐phenylethyl)), at various temperatures allows us to understand the water exchange dynamics of these four complexes. The water‐exchange lifetime (τM) parameters for [Gd(DTPA‐PY)(H2O)]?, [Gd(DTPA‐HP)(H2O)2]?, [Gd(DTPA‐H1P)(H2O)2]? and [Gd(DTPA‐H2P)(H2O)2] are of 585, 98, 163, and 69 ns, respectively. Compared with [Gd(DTPA)(H2O)]2? (τM = 303 ns), the τM value of [Gd(DTPA‐PY)(H2O)]? is slightly higher, but the other three complexes values are significantly lower than those of [Gd(DTPA)(H2O)]2?. This difference is explained by the fact that the gadolinium(III) complexes of DTPA‐HP, DTPA‐H1P, and DTPA‐H2P have two inner‐sphere waters. The 2H longitudinal relaxation rates of the labeled diamagnetic lanthanum complex allow the calculation of its rotational correlation time (τR). The τR values calculated for DTPA‐PY, DTPA‐HP, DTPA‐H1P, and DTPA‐H2P are of 127, 110, 142 and 147 ps, respectively. These four values are higher than the value of [La(DTPA)]2? (τR = 103 ps), because the rotational correlation time is related to the magnitude of its molecular weight.  相似文献   

17.
A new, simple, rapid, sensitive, efficient and low‐cost spectrophotometric procedure for the determination of gold was developed. The method is based on the reaction of [AuCl4]? with 2‐[2‐(4‐dimethylaminophenyl)‐vinyl]‐1,3,3‐trimethyl‐3H‐indolium reagent to form a colored ion associate extractable by various organic solvents. The molar absorptivity of the ion associates is in the range (5.7–9.2) × 104 L mol?1 cm?1 depending on the extractant. Butyl acetate was chosen as the extractant. The optimum reaction conditions were established: pH 2–4, concentration of the dye reagent (0.8–1.5) × 10?4 mol L?1. The determination of gold is not hindered even by a 1000‐fold concentration of Ni and Co; a 500‐fold concentration of Pb and Zn; a 100‐fold concentration of Bi, Cu, Cd, Pt, Rh and Ru; or a 20‐fold concentration of Ag. The established method was applied to the determination of gold in model samples and enriched polymetallic ores.  相似文献   

18.
The ortho‐metallation product of the reaction of (±)‐amphetamine with gold(III) chloride, [D,L‐2‐(2‐aminopropyl)phenyl‐κ2N,C1]dichloridogold(III), [Au(C9H12N)Cl2], and the two salts resulting from crystallization of (+)‐methamphetamine with gold(III) chloride, D‐methyl(1‐phenylpropan‐2‐yl)azanium tetrachloridoaurate(III), (C10H16N)[AuCl4], and of (±)‐ephedrine with gold(III) chloride, D,L‐(1‐hydroxy‐1‐phenylpropan‐2‐yl)(methyl)azanium tetrachloridoaurate(III), (C10H16NO)[AuCl4], have different structures. The first makes a bidentate complex directly with a dichloridogold(III) group, forming a six‐membered ring structure; the second and third each form a salt with [AuCl4] (each has two formula units in the asymmetric unit). The organic components are all members of the same class of stimulants that are prevalent in illicit drug use. These structures are important contributions to the understanding of the microcrystal tests for these drugs that have been employed for well over 100 years.  相似文献   

19.
The effect of additions of hydrophobic dioctyl sulfide (L) on the kinetics of dissolution of gold nanoparticles in the interaction with a dispersed aqueous hydrochloric solution of H2O2 in Triton N-42 reverse micelles (decane was the dispersion medium) was studied spectrophotometrically. The process consists of a two-stage oxidation Au0 → AuCl2 → AuCl4 at the surface of gold particles; the first stage occurs in two ways: a spontaneous reaction and an autocatalytic reaction involving AuCl4 ions. With small additions of L (c L < c Au), only spontaneous oxidation of Au(0) to Au(I) takes place because Au(I) is completely bound in an inert complex AuLCl. When unbound L is exhausted, the newly formed AuLCl is accumulated in micellar shells, changes the properties of the medium inside the micelles, and affects the rate constant of the autocatalytic reaction, which increases with increasing c L. At high concentrations of L, the coagulation of particles occurs instead of their dissolution, because of the deterioration of the protective properties of micellar shells as a result of the ingression and accumulation of dioctyl sulfide molecules on account of selective adsorption on gold particles. The rate constants of all stages of dissolution and coagulation are determined.  相似文献   

20.
The interaction of freshly precipitated cadmium and zinc morpholinedithiocarbamates with solutions of AuCl3 in 2 M HCl is studied. In both cases, the heterogeneous reactions of gold(III) binding from solutions lead to the formation of the ionic gold(III) complex [Au3{S2CN(CH2)4O}6][Au2Cl8][AuCl4] (I), whose molecular and supramolecular structures are determined by X-ray diffraction analysis. Compound I includes centrosymmetric and noncentrosymmetric cations [Au{S2CN(CH2)4O}2]+ in a ratio of 1: 2. According to the manifested structural differences, the complex cations are related as conformers (cations A are Au(1) and cations B are Au(2)). At the supramolecular level, the isomeric cations form linear trinuclear structural fragments [Au3{S2CN(CH2)4O}6]3+ [A...B...A] due to secondary bonds Au...S of 3.6364 Å. The anionic part of compound I is presented by [AuCl4]? and centrosymmetric binuclear [Au2Cl8]2?, whose formation involved secondary bonds Au...Cl of 3.486 and 3.985 Å. The ultimate chemisorption capacity of cadmium and zinc morpholinedithiocarbamates calculated from the binding of gold(III) is 901.7 and 1010.4 mg of Au3+ per 1 g of the sorbent, respectively (i.e., each miononuclear fragment of the chemisorption complexes [M{S2CN(CH2)4O}2] participates in binding of two gold atoms). To establish the conditions for the isolation of bound gold, the thermal properties of compound I are studied by simultaneous thermal analysis. The thermal destruction process includes the thermolysis of the dithiocarbamate part of the complex and anions [AuCl4]? and [Au2Cl8]2? with the reduction of gold to the metal, being the only final product of the thermal transformations of compound I.  相似文献   

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