Au Compounds Research Articles

Mineralogical and geochemical features of human body ash residue of spatially-localized technogenic system (Norilsk city)

The paper presents the information on the element and mineral composition of the human body ash residue of Norilsk residents. The data are obtained by such methods as X-ray analysis, inductively coupled plasma mass spectrometry, and electron microscopy. This research has identified the content of 47 elements, 17 of which have their own mineral phases. Besides, the estimation of average content of chemical elements in terms of sex and correlation analysis of the data was conducted in this research. The final results indicate the influence of Norilsk industry on the element and mineral composition of ash residue. For example, the accumulation of such elements as Zr, Al, Ca, Y, some rare earth, and radioactive elements has been observed in the human body ash residue of Norilsk residents. The presence of Ag, Au, Pt microphases and numerous compounds of Cu, Ni etc. was detected among all mineral phases.

Synthetic strategies of gold(I)-selenolates from ortho-substituted diaryl diselenides via selenol and selenenyl sulfide intermediates

In the present study we describe the synthetic strategies to gold(I)-selenolate complexes by the reaction of ortho-substituted diaryl diselenides and electrophilic anti-arthritic gold(I)-compounds in the presence of thiol such as PhSH. Diselenides react with thiol to generate a mixture of selenol and selenenyl sulfide. While selenols react with electrophilic Au(I) compounds to form gold(I)-selenolate complexes, the selenenyl sulfides do not react and therefore, a prior conversion of selenenyl sulfide to selenol is necessary for an effective formation of gold(I)-selenolate from diselenide. However, this process is associated with the ligand exchange reaction in selenenyl sulfide in the presence of PhSH that hampers the regeneration of selenol. The structural aspects as well as the mode of reactivities of selenenyl sulfides and the products (gold(I)-selenolates) were analyzed using experimental as well as computational methods. These studies indicated that the presence of ortho-coordinating donor groups and oxidation state of Se-center play crucial roles towards their reactivities. Density functional theory calculations were undertaken to determine the natural charges on heteroatoms and to find the site for nucleophilic attack related to ligand exchange reactions.

Effects of coordination mode of 2-mercaptothiazoline on reactivity of Au(I) compounds with thiols and sulfur-containing proteins

Gold(I) based drugs are interesting for their potential medical use. The relatively facile ligand substitution in linear gold(I) compounds makes the identification of active species complicated. Ligands such as PR3 and CN− are likely to be carrier ligands due to their strong trans-directing properties and will dictate the nature of substitution reactions. The 2-mercaptothiazoline (mtz) ligand is an N,S-heterocyclic compound which presents an exocyclic thiol sulfur as well as a heterocyclic nitrogen. The coordination of mtz to transition metals can be modulated by the trans ligand and complexes with metal bound through the nitrogen and/or the exocyclic sulfur are known. Therefore, the complexes [NCAu(N-mtz)] (N-coordinated) and [(Ph3P)Au(S-mtz)] (S-coordinated) were investigated to compare the influence of CN− and PR3 as well as the coordination mode of the mtz ligand on reactivity with thiols and sulfur-containing proteins. As a further comparison the compound [(Ph3P)AuCN] was also studied. Human serum albumin, egg white lysozyme and, principally, the C-terminal zinc finger (ZF2) of the nucleocapsid NCp7protein of HIV-1 were studied. Results from zinc finger studies show that the coordination structure can determine the reactivity toward biomolecules. Due to ligand scrambling, the complex [NCAu(N-mtz)] forms very reactive species in solution generating [NCyAux-biomolecule] adducts, where x,y≤3. The observation by mass spectrometry of [(CN)Au]-ZF confirms the ability of Au(I) compounds to form [(Ligand)Au] adducts on zinc fingers, in contrast to Au(III), where all ligands are lost upon reaction with the zinc finger. On the other hand, [(Ph3P)Au(S-mtz)] also generates the [(Ph3P)2Au]+ species due to ligand scrambling, that showed lower reactivity, probably due to steric hindrance. For this complex [(Ph3P)Au-biomolecule] and [Au-biomolecule] adducts are dominant. The results corroborate the hypothesis of modulation through coordination as the reactivity clearly depends on not only the ligand, but also the coordination mode.

Gold nanoparticles: A critical review of therapeutic applications and toxicological aspects

ABSTRACTGold (Au) compounds have been utilized as effective therapeutic agents for the treatment of some inflammatory diseases such as rheumatoid arthritis. However, Au compound use has become limited due to associated high incidence of side effects. Recent development of nanomaterials for therapeutic use with Au-containing drugs is improving the beneficial actions and reducing toxic properties of these agents. Lower toxicity in conjunction with anti-inflammatory and antiangiogenic effects was reported to occur with gold nanoparticles (AuNP) treatment. However, despite this therapeutic potential, safety of AuNP remains to be determined, since the balance between therapeutic properties and development of adverse effects is not well established. Several variables that drive this benefit–risk balance, including physicochemical characteristics of nanoparticles such as size, shape, surface area, and chemistry, are poorly described in the scientific literature. Moreover, therapeutic and toxicological data were obtained employing nonstandardized or poorly described protocols with different experimental settings (animal species/cell type, route and time of exposure). In contrast, effective and safe application of AuNP may be established only after elucidation of various physicochemical properties of each specific AuNP, and determination of respective kinetics and interaction of compound with target tissue. This critical review conveys the state of the art, the therapeutic use, and adverse effects mediated by AuNP, with primary emphasis on anti-inflammatory and antiangiogenic potential, highlighting the limitations/gaps in the scientific literature concerning important points: (i) selection of experimental designs (in vitro and in vivo models) and (ii) consideration of different physicochemical properties of AuNP that are often disregarded in many scientific publications. In addition, prospects and future needs for research in this area are provided.

Formation of alloys upon the simultaneous electrochemical deposition of gold and tin from ethylene glycol and aqueous electrolytes

An ethylene glycol (EG) solution containing Au(III) and Sn(IV) compounds, and conditions for the electrochemical deposition of Au–Sn alloy based on AuSn and Au5Sn intermetallics with total tin content of 30–55 at % are proposed. Fundamental difficulties of the deposition of alloys with high tin content, (including eutectic Au–Sn alloy) from aqueous electrolytes are revealed. It is determined via voltammetry that the simultaneous deposition of gold and tin from aqueous and EG electrolytes proceeds with the depolarization effect of both Au(III) and Sn(IV) as a result of the formation of the alloy, the increase in the rate of tin cathodic reduction being more noticeable in case of EG solution. Formation of SnCl2EG(H2O)2+ complex upon the dissolution of SnCl4 · 5H2O in glycol, the stability of the composition of tetracyanoaurate ions upon the dissolution of K[Au(CN)4], and the weakening of intermolecular interactions in EG with small amounts of water were revealed via IR spectroscopy. It is suggested that the depolarization effect is due not only to alloy formation, but also to the formation of SnCl2EG(H2O)2+ cations, their association with Au(CN)4- anions, and a change in the mechanism of Au(III) and Sn(IV) reduction.

Atmospheric-Pressure DBD Cold Plasma for Preparation of High Active Au/P25 Catalysts for Low-Temperature CO Oxidation**supported by National Natural Science Foundation of China (Nos. 11505019, 21173028), the Science and Technology Research Project of Liaoning Provincial Education Department (No. L2013464), the Scientific Research Foundation for the Doctor of Liaoning Province (No. 20131004), and the Dalian Jinzhou New District Science and Technology Plan

Cold plasma generated by dielectric barrier discharge (DBD) at atmospheric pressure was adopted for preparation of commercial TiO2 Degussa P25 supported Au catalysts (Au/P25-P) with the assistance of the deposition-precipitation procedure. The influences of the plasma reduction time and calcination on the performance of the Au/P25-P catalysts were investigated. CO oxidation was performed to investigate the catalytic activity of the Au/P25 catalysts. The results show that DBD cold plasma for the fabrication of Au/P25-P catalysts is a fast process, and Au/P25-P (4 min) exhibited the highest CO oxidation activity due to the complete reduction of Au compounds and less consumption of oxygen vacancies. In order to form more oxygen vacancies active species, Au/P25-P was calcined to obtain Au/P25-PC catalysts. Interestingly, Au/P25-PC exhibited the highest activity for CO oxidation among the Au/P25 samples. The results of transmission electron microscopy (TEM) indicated that the smaller size and high distribution of Au nanoparticles are the mean reasons for a high performance of Au/P25-PC. Atmospheric-pressure DBD cold plasma was proved to be of great efficiency in preparing high performance supported Au catalysts.

Multi-scale imaging of anticancer platinum(iv) compounds in murine tumor and kidney.

Nano-scale secondary ion mass spectrometry (NanoSIMS) enables trace element and isotope analyses with high spatial resolution. This unique capability has recently been exploited in several studies analyzing the subcellular distribution of Au and Pt anticancer compounds. However, these studies were restricted to cell culture systems. To explore the applicability to the in vivo setting, we developed a combined imaging approach consisting of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), NanoSIMS and transmission electron microscopy (TEM) suitable for multi-scale detection of the platinum distribution in tissues. Applying this approach to kidney and tumor samples upon administration of selected platinum(iv) anticancer prodrugs revealed uneven platinum distributions on both the organ and subcellular scales. Spatial platinum accumulation patterns were quantitatively assessed by LA-ICP-MS in histologically heterogeneous organs (e.g., higher platinum accumulation in kidney cortex than in medulla) and used to select regions of interest for subcellular-scale imaging with NanoSIMS. These analyses revealed cytoplasmic sulfur-rich organelles accumulating platinum in both kidney and malignant cells. Those in the tumor were subsequently identified as organelles of lysosomal origin, demonstrating the potential of the combinatorial approach for investigating therapeutically relevant drug concentrations on a submicrometer scale.

Formation of heterobinuclear Pt–Au complexes by chelate ring-opening of cis-[Pt(κ2-C6R4PPh2)2] (R = H, F)

Mixed metal complexes of the type [Pt(κ2-2-C6R4PPh2) (PPh3) (μ-2-C6R4PPh2)AuCl] (R = H, F) can be prepared by treatment of cis-[Pt(κ2-C6R4PPh2)2] with [AuCl(PPh3)]. Under similar reaction conditions, the trans isomer of [Pt(κ2-C6F4PPh2)2] is unreactive. Computational studies have been performed to provide insights into the reasons for this difference in reactivity. Density Functional Theory (DFT) calculations show that formation of an AuCl adduct of [Pt(κ2-2-C6R4PPh2)2] is favoured over nucleophilic addition of PPh3 to Pt as the initial step of the reaction, and reveal the required energy of the cis and trans isomers of the bis-chelate [Pt(κ2-2-C6R4PPh2)2] in forming the mixed metal Pt–Au compounds. NBO analysis sheds more light on the bonding orbitals of the cis and trans isomers, suggesting that the Pt–P bonds in the cis isomer are more labile.

Chiral Ligand-Protected Bimetallic Nanoclusters: How does the Metal Core Configuration Influence the Nanocluster’s Chiroptical Responses?

ABSTRACTWe here present electronic structures and chiroptical responses of gold-based bimetallic nanoclusters protected by chiral thiolate ligand, glutathione (GSH), and compare them with those of monometallic counterparts. The nanoclusters examined are AuPd and AuAg bimetallic systems. The effect of Pd or Ag doping on the chiroptical responses of optically active Au nanoclusters as well as the importance of the bimetallic core configurations are discussed. Briefly, we find that GS-protected AuPd or AuAg nanoclusters exhibit quite different Cotton effects from those of the monometallic nanoclusters in metal-based electronic transition regions. In the AuPd system, all bimetallic nanoclusters exhibit featureless absorption profiles, but their circular dichroism (CD) signals are structured, offering a greater advantage in detecting a foreign atom doping in the nanocluster system. In the AuAg system, the nanocluster compounds exhibit relatively weaker CD responses than those of the corresponding Au compounds. This CD decrease can be explained in terms of the increased geometrical isomers that are formed by statistical distribution of Ag heteroatoms in the nanocluster, since an increased number of possible configurations gives an average in the CD response with positive and negative bands of different optical isomers.

Au(dien)(N-heterocycle)](3+): reactivity with biomolecules and zinc finger peptides.

The reaction of [Au(dien)(N-heterocycle)](3+) (AuN4) coordination compounds with simple amino acids and zinc finger proteins is reported. Compared to [AuCl(dien)](2+), NMR studies show that the presence of a more substitution-inert N-donor as the putative leaving group slows the reaction with the sulfur-containing amino acids N-acetylmethionine (NAcMet) and N-acetylcysteine (NAcCys). Lack of ligand dissociation upon reaction with NAcCys indicates, to our knowledge, the first long-lived N-heterocycle-Au-S species in solution. Reactions with zinc finger proteins show a higher reactivity with the Cys3His zinc finger than with Cys2His2, likely due to the presence of fewer aurophilic cysteines in the latter. Of the Au(III) compounds studied, [Au(dien)(DMAP)](3+) (DMAP = 4-dimethylaminopyridine) appears to be the least reactive, with ESI-MS studies showing the presence of intact zinc fingers at initial reaction times. These results, in combination with previously reported characterization and pH dependency studies, will further aid in optimizing the structure of these AuN4 species to obtain a substitution-reactive yet selective compound for targeting zinc finger proteins.

Gold(i) compounds with lansoprazole-type ligands: synthesis, characterization and anticancer properties in vitro

Initial results on Au(i) compounds containing lansoprazole-type ligands as possible anticancer agents.

Nearly Constant Electrical Resistance over Large Temperature Range in Cu3NMx (M = Cu, Ag, Au) Compounds

Electrical resistance is a material property that usually varies enormously with temperature. Constant electrical resistivity over large temperature range has been rarely measured in a single solid. Here we report the growth of Cu3NMx (M = Cu, Ag, Au) compound films by magnetron sputtering, aiming at obtaining single solids of nearly constant electrical resistance in some temperature ranges. The increasing interstitial doping of cubic Cu3N lattice by extra metal atoms induces the semiconductor-to-metal transition in all the three systems. Nearly constant electrical resistance over 200 K, from room temperature downward, was measured in some semimetallic Cu3NMx samples, resulting from opposite temperature dependence of carrier density and carrier mobility, as revealed by Hall measurement. Cu3NAgx samples have the best performance with regard to the range of both temperature and doping level wherein a nearly constant electrical resistance can be realized. This work can inspire the search of other materials of such a quality.

Synthesis and Evaluation of Polymeric Gold Glyco-Conjugates as Anti-Cancer Agents

The antitumor activity of organo-gold compounds is a focus of research from the past two decades. A variety of gold stabilizing ligands such as vitamins and xanthanes have been prepared and explored for their 'chelating effect' as well as for their antitumor activity. Dithiocarbamates (DTC) compounds and their metallic conjugates have been well explored for their antiproliferative activities. In this study, glycopolymer based DTC-conjugates are prepared by reversible addition-fragmentation chain transfer polymerization (RAFT) and subsequently modified with gold(I) phosphine. These polymer-DTC derivatives and their gold compounds are tested for their in vitro toxicity in both normal and cancer cell lines. The Au(I) phosphine conjugated cationic glycopolymers of 10 kDa and 30 kDa are evaluated for their cytotoxicity profiles using MTT assay. Au(I) compounds are well-known for their mitochondrial toxicity, hence hypoxic cell lines bearing unusually enlarged mitochondria are subjected to these anticancer compounds. It is concluded that these polymeric DTC derivatives and their gold conjugates indeed show higher accumulation as well as cytotoxicity to cancer cells under hypoxic conditions in comparison to the normoxic ones. Hypoxic MCF-7 cells showed significant sensitivity toward the low molecular weight (10 kDa) glycopolymer-Au(I) complexes.

‘Laser chemistry’ synthesis, physicochemical properties, and chemical processing of nanostructured carbon foams

Laser ablation of selected coordination complexes can lead to the production of metal-carbon hybrid materials, whose composition and structure can be tailored by suitably choosing the chemical composition of the irradiated targets. This ‘laser chemistry’ approach, initially applied by our group to the synthesis of P-containing nanostructured carbon foams (NCFs) from triphenylphosphine-based Au and Cu compounds, is broadened in this study to the production of other metal-NCFs and P-free NCFs. Thus, our results show that P-free coordination compounds and commercial organic precursors can act as efficient carbon source for the growth of NCFs. Physicochemical characterization reveals that NCFs are low-density mesoporous materials with relatively low specific surface areas and thermally stable in air up to around 600°C. Moreover, NCFs disperse well in a variety of solvents and can be successfully chemically processed to enable their handling and provide NCF-containing biocomposite fibers by a wet-chemical spinning process. These promising results may open new and interesting avenues toward the use of NCFs for technological applications.

Strength distribution of Au ball bond using nanoindentation approach

The evaluation of gold, Au ball bond requires a new approach to obtain a more localized and detailed result. This is due to the limited data in terms of quality and quantity obtained from conventional tests. The nanoindentation test is proposed in order to evaluate the quality of ball bond in more detail. The nanoindentation test was carried out to analyze the strengthening of Au ball bond after being subjected to high temperature storage, HTS. It was observed that Au and intermetallic compounds, IMC, have a higher creep behavior compared to that of silicon, Si. The dislocation glide was the responsible indentation creep mechanism for Au and IMC of ball bond that have been subjected to 0 and 1000h of HTS. It was observed that the variation of creep behavior of Au ball bond was reduced after being subjected to 1000h of HTS. The variation of creep behavior of IMC decreased after being subjected to 1000h of HTS. It was also noted that the creep behavior of both Au and IMC decreased with the increase of HTS time interval. It was found that the hardness value for Au decreased with the increase of HTS time interval, whereas, the hardness value of IMC increased with the increment of HTS time interval. Based on the results obtained, it was indicated that the nanoindentation test has the ability to evaluate the strengthening of Au ball bond in a localized manner and in more detail compared to that of the conventional tests.

A silver-free system for the direct C–H auration of arenes and heteroarenes from gold chloride complexes

A new methodology for the direct C–H auration of electron-deficient arenes and heteroarenes with simple bases and readily available [Au(PR3)Cl] complexes is described. This system allows the preparation of a wide scope of aryl–Au(I) compounds without the need for using Ag(I) additives or preparing and isolating basic Au(I) hydroxide complexes.

Electronic Structure of Pt and Au Compounds Measured by X-ray Emission and X-ray Absorption Spectroscopies

The electronic structure of the filled and unfilled states and the formation of the chemical bonding in PtO2, PtCl4, PtS2, and Au2S are studied by measured Pt and Au Lβ5 X-ray emission spectra (XES) and L3-edge X-ray absorption spectra (XAS). The study is based on the comparative analysis of the calculated local partial densities of electronic states (LPDOS) on the noble atom and on the neighboring ligands. It is revealed that theoretical description of experimental spectra requires going beyond MT-approximation and therefore the full-potential linearized augmented-plane-wave method realized in the code WIEN2k is applied. The effect of a static screened 2p core-hole potential of Pt and Au on the calculated Pt L3-edge XAS is examined with a supercell approach. The obtained agreement of theoretical spectra with the experimental ones validates the results of the LPDOS analysis and the made conclusions on electronic structure of the studied compounds.

First principles study on structural, electronic and elastic properties of AgX and AuX (X = Mg, Sc, Zn and Cd) intermetallic compounds

The electronic, elastic and mechanical properties of eight binary B2 – type intermetallic compounds of Ag and Au (AgX and AuX, X=Mg, Sc, Zn and Cd) have been studied systematically using first principles density functional theory within generalized gradient approximation. Ground state properties such as lattice constant (a0), bulk modulus (B), its pressure derivative (B′) and elastic constants are calculated. The present results are in good agreement with the experimental and other available theoretical results. Poisson’s ratio (σ), Young’s moduli (E), shear moduli (GH) and the ratio of elastic anisotropy factor (A) are also estimated. Ductility for these compounds is further analysed by calculating the ratio of B/GH and Cauchy pressure (C12–C44). Amongst all the intermetallics AuZn is found to be most ductile due to the presence of strong metallic bonding, and AgZn is least ductile in all the Au and Ag intermetallic compounds.

Cytotoxic hydrophilic iminophosphorane coordination compounds of d8 metals. Studies of their interactions with DNA and HSA

The synthesis and characterization of a new water-soluble N,N-chelating iminophosphorane ligand TPAN―C(O)―2-NC5H4 (N,N-IM) (1) and its d8 (AuIII, PdII and PtII) coordination complexes are reported. The structures of cationic [AuCl2(N,N-IM)]ClO4 (2) and neutral [MCl2(N,N-IM)] M=Pd (3), Pt(4) complexes were determined by X-ray diffraction studies or by means of density-functional calculations. While the Pd and Pt compounds are stable in mixtures of DMSO/H2O over 4days, the gold derivative (2) decomposes quickly to TPAO and previously reported neutral gold(III) compound [AuCl2(N,N-H)] 5 (containing the chelating N,N-fragment HN―C(O)―2-NC5H4). The cytotoxicities of complexes 2–5 were evaluated in vitro against human Jurkat-T acute lymphoblastic leukemia cells and DU-145 human prostate cancer cells. Pt (4) and Au compounds (2 and 5) are more cytotoxic than cisplatin to these cell lines and to cisplatin-resistant Jurkat sh-Bak cell lines and their cell death mechanism is different from that of cisplatin. All the compounds show higher toxicity against leukemia cells when compared to normal human T-lymphocytes (PBMC). The interaction of the Pd and Pt compounds with calf thymus and plasmid (pBR322) DNA is different from that of cisplatin. All compounds bind to human serum albumin (HSA) faster than cisplatin (measured by fluorescence spectroscopy). Weak and stronger binding interactions were found for the Pd (3) and Pt (4) derivatives by isothermal titration calorimetry. Importantly, for the Pt (4) compounds the binding to HSA was reversed by addition of a chelating agent (citric acid) and by a decrease in pH.

Trends in the Electronic Structure of Extended Gold Compounds: Implications for Use of Gold in Heterogeneous Catalysis

First-principles electronic structure calculations are presented on a variety of Au compounds and species--encompassing a wide range of formal oxidation states, coordination geometries, and chemical environments--in order to understand the potentially systematic behavior in the nature and energetics of d states that are implicated in catalytic activity. In particular, we monitor the position of the d-band center, which has been suggested to signal catalytic activity for reactions such as CO oxidation. We find a surprising absence of any kind of correlation between the formal oxidation state of Au and the position of the d-band center. Instead, we find that the center of the d band displays a nearly linear dependence on the degree of its filling, and this is a general relationship for Au irrespective of the chemistry or geometry of the particular Au compound. Across the compounds examined we find that even small calculated changes in the d-band filling result in a relatively large effect on the position of the d-band center. The results presented here have some important implications for the question of the catalytic activity of Au and indicate that the formal oxidation state is not a determining factor.