Distribution by Scientific Domains
Distribution within Chemistry

Kinds of Gold

  • cationic gold
  • colloidal gold
  • quantiferon-tb gold

  • Terms modified by Gold

  • gold Nanoparticle
  • gold Nanorod
  • gold alloy
  • gold atom
  • gold catalysis
  • gold catalyst
  • gold cluster
  • gold coast
  • gold coating
  • gold colloid
  • gold complex
  • gold compound
  • gold concentration
  • gold deposit
  • gold electrode
  • gold film
  • gold layer
  • gold mine
  • gold mineralization
  • gold nanocrystal
  • gold nanoparticle
  • gold nanoparticle array
  • gold nanorod
  • gold np
  • gold particle
  • gold precursor
  • gold screw
  • gold standard
  • gold standard method
  • gold standard test
  • gold standard treatment
  • gold standards
  • gold substrate
  • gold surface

  • Selected Abstracts

    Phosphino-Aminothiazoline Platinum(II) and Platinum(II)/Gold(I) Complexes: Structural, Chemical and Vapoluminescent Properties

    Roberto Pattacini Dr.
    Abstract Phosphino-amino-thiazolines and -thiazoles can exist in solution in two tautomeric forms, in which the NH proton involves the endo-cyclic or exo-cyclic nitrogen atom. The two tautomers show different reactivities toward alcoholysis; the imino form degrades more rapidly. Their bischelated platinum complexes were studied in the solid state by single crystal X-ray diffraction. Thus, the unique stereoelectronic features of the [Pt(PNth)] (PNth=diphenylposphino-aminothiazoline) moiety were revealed. The complex cis -[Pt(PNth)2] reacts with gold(I) salts to yield dimetallic compounds, the molecular structures of which have been determined by X-ray diffraction. Solid cis -[Pt(PNth)2] shows vapoluminescent properties if exposed to alcohol vapors. A combined photophysical and crystallographic investigation has been carried out to clarify the unprecedented rigidochromic role of the alcohol in this phenomenon. [source]

    Study of a highly accurate and fast protein,ligand docking method based on molecular dynamics

    M. Taufer
    Abstract Few methods use molecular dynamics simulations in concert with atomically detailed force fields to perform protein,ligand docking calculations because they are considered too time demanding, despite their accuracy. In this paper we present a docking algorithm based on molecular dynamics which has a highly flexible computational granularity. We compare the accuracy and the time required with well-known, commonly used docking methods such as AutoDock, DOCK, FlexX, ICM, and GOLD. We show that our algorithm is accurate, fast and, because of its flexibility, applicable even to loosely coupled distributed systems such as desktop Grids for docking. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Genetic variation in COL17A1 and the development of bullous pemphigoid

    Samantha Winsey
    Background: Bullous pemphigoid (BP) is an autoimmune blistering disease of the skin characterized by autoantibody attack on collagen XVII. Objectives: To characterize the genetic complexity of COL17A1, the gene which encodes for the autoantigen collagen XVII. The data will be used to determine whether there is an association between polymorphisms and haplotypes of COL17A1 and genetic susceptibility to development of BP. Methods: The genetic complexity in COL17A1 was deduced by screening and then sequencing the gene. Haplotypes were constructed from the resulting polymorphisms using the statistical programme PHASE. The linkage disequilibrium (D,) between the polymorphisms was deduced from haplotypic data using the statistical programme GOLD. Association of the polymorphisms and haplotypes was tested for, in a cohort of BP patients and controls. Results: Screening of COL17A1 for genetic variation was carried out in 29 individuals of North European caucasoid origin, and it revealed 19 single-nucleotide polymorphisms in approximately 14.7 kb of sequence. These variants resulted in 60 different haplotypes in 191 individuals, of which 13 occurred above 1% in the population. D, between the variants was found to be extensive, have a low correlation with physical distance and to extend over 33.8 kb. No association was found with any of the polymorphisms or haplotypes and development of BP, when tested for, in a cohort of patients and controls. Conclusion: This study provides an extensive description of the genetic variation in COL17A1 and shows no association of the genetic variants with susceptibility to BP. [source]

    A review of the GOLD guidelines for the diagnosis and treatment of patients with COPD

    L. Fromer
    Summary Chronic obstructive pulmonary disease (COPD) is a leading cause of death in the USA, and represents a major health, social and economic burden. COPD is underdiagnosed and often misdiagnosed, which likely contributes to the continuing increases in the prevalence, morbidity and mortality associated with this disease. This is unfortunate because whereas COPD cannot be cured, it can be treated effectively, particularly during the earlier stages of the disease. Evidence-based guidelines, developed to assist in the prevention, diagnosis and management of COPD, are available to healthcare professionals interested in learning more about COPD. These guidelines are updated and revised on a regular basis to reflect recent advances in our understanding of the pathophysiology of and treatments available for COPD. Nevertheless, primary-care physicians have reported a lack of awareness of the fundamental concepts underpinning the optimal treatment and management of COPD presented in the guidelines. Thus, the objective of this article is to summarise key physiologic, diagnostic and management concepts provided in the most recent update of the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines, which were published in November 2006. [source]


    Stephen J. Bennett
    First page of article [source]

    MINERAL: GOLD: Burkina Faso

    Article first published online: 1 SEP 2010
    No abstract is available for this article. [source]

    GOLD: Gold Mine Cost Report

    Article first published online: 8 JUL 2010
    No abstract is available for this article. [source]

    SODOCK: Swarm optimization for highly flexible protein,ligand docking

    Hung-Ming Chen
    Abstract Protein,ligand docking can be formulated as a parameter optimization problem associated with an accurate scoring function, which aims to identify the translation, orientation, and conformation of a docked ligand with the lowest energy. The parameter optimization problem for highly flexible ligands with many rotatable bonds is more difficult than that for less flexible ligands using genetic algorithm (GA)-based approaches, due to the large numbers of parameters and high correlations among these parameters. This investigation presents a novel optimization algorithm SODOCK based on particle swarm optimization (PSO) for solving flexible protein,ligand docking problems. To improve efficiency and robustness of PSO, an efficient local search strategy is incorporated into SODOCK. The implementation of SODOCK adopts the environment and energy function of AutoDock 3.05. Computer simulation results reveal that SODOCK is superior to the Lamarckian genetic algorithm (LGA) of AutoDock, in terms of convergence performance, robustness, and obtained energy, especially for highly flexible ligands. The results also reveal that PSO is more suitable than the conventional GA in dealing with flexible docking problems with high correlations among parameters. This investigation also compared SODOCK with four state-of-the-art docking methods, namely GOLD 1.2, DOCK 4.0, FlexX 1.8, and LGA of AutoDock 3.05. SODOCK obtained the smallest RMSD in 19 of 37 cases. The average 2.29 Å of the 37 RMSD values of SODOCK was better than those of other docking programs, which were all above 3.0 Å. © 2006 Wiley Periodicals, Inc. J Comput Chem 28: 612,623, 2007 [source]


    Lee M. Williams
    The gap between research and clinical practice is one of the key challenges facing family therapy. Clinicians often fail to incorporate research findings into their practice because they do not know how to search, evaluate, or apply research to their clinical work. The purpose of this article is to help clinicians become better consumers of research. This article explores the potential value of research to clinicians, as well as negative beliefs that clinicians may have about research. The article also describes how clinicians can use research to inform their clinical work, as well as potential challenges that can be encountered. [source]

    Mining GOLD and new model organisms in biotechnology

    P. Pizarro-Tobías

    Fostering a Community-Based Learning Culture: A Model for Success and Institutional Barriers

    María (Lorena) Núñez
    This article offers a case study in Community-Based Learning by describing a collaborative gang-intervention effort developed for children in Los Angeles. Project GOLD (Goal Oriented Life Decisions), is an educational-intervention effort designed by representatives from Occidental College, Garvanza Elementary School, the LAPD, and the Los Angeles City Attorney's Office and implemented in the elementary school. Both authors are directly involved with the program and offer a first-hand description of the project. They also detail some of the obstacles and barriers to the program's sustainability. Even as Community-Based Learning (CBL) has become more acceptable and its value as a pedagogical approach is gaining attention, Project GOLD remains vulnerable because the resources are not yet there. Project GOLD and efforts like it will only truly succeed when CBL becomes institutionalized in colleges and universities, releasing professors and students into communities with the resources and support necessary for long-term success. [source]


    PALAEONTOLOGY, Issue 6 2007
    Abstract:, An essential tool in micropalaeontological studies is analysis and imaging using a scanning electron microscope (SEM). It is commonly necessary to coat the sample with a thin layer of gold or gold-palladium alloy in order to prevent charging of the surface, to promote the emission of secondary electrons so that the specimen conducts evenly, and to provide a homogeneous surface for analysis and imaging. However, coating a specimen with gold is a semi-destructive process that masks the surface of specimens, and a common curatorial practice is to prohibit coating of important specimens. We describe a non-destructive, simple and inexpensive technique that uses KCN (or NaCN), a glass jar, paper towels, cardboard and a fume hood for the removal of gold coatings from SEM samples. This technique requires little additional handling of the specimen, and there is no need to place the specimen in a solution. [source]

    Nanomolar Competitive Inhibitors of Mycobacterium tuberculosis and Streptomyces coelicolor Type,II Dehydroquinase

    CHEMMEDCHEM, Issue 2 2007
    Verónica F.
    Abstract Isomeric nitrophenyl and heterocyclic analogues of the known inhibitor (1S,3R,4R)-1,3,4-trihydroxy-5-cyclohexene-1-carboxylic acid have been synthesized and tested as inhibitors of M.,tuberculosis and S.,coelicolor type,II dehydroquinase, the third enzyme of the shikimic acid pathway. The target compounds were synthesized by a combination of Suzuki and Sonogashira cross-coupling and copper(I)-catalyzed 2,3-dipolar cycloaddition reactions from a common vinyl triflate intermediate. These studies showed that a para -nitrophenyl derivative is almost 20-fold more potent as a competitive inhibitor against the S.,coelicolor enzyme than that of M.,tuberculosis. The opposite results were obtained with the meta isomer. Five of the bicyclic analogues reported herein proved to be potent competitive inhibitors of S.,coelicolor dehydroquinase, with inhibition constants in the low nanomolar range (4,30,nM). These derivatives are also competitive inhibitors of the M.,tuberculosis enzyme, but with lower affinities. The most potent inhibitor against the S.,coelicolor enzyme, a 6-benzothiophenyl derivative, has a Ki value of 4,nM,over 2000-fold more potent than the best previously known inhibitor, (1R,4R,5R)-1,5-dihydroxy-4-(2-nitrophenyl)cyclohex-2-en-1-carboxylic acid (8,,M), making it the most potent known inhibitor against any dehydroquinase. The binding modes of the analogues in the active site of the S.,coelicolor enzyme (GOLD,3.0.1), suggest a key , -stacking interaction between the aromatic rings and Tyr,28, a residue that has been identified as essential for enzyme activity. [source]

    Factors Associated with Hospital Admission among Emergency Department Patients with Chronic Obstructive Pulmonary Disease Exacerbation

    Chu-Lin Tsai MD
    Abstract Objectives To determine the patient factors associated with hospital admission among adults who present to the emergency department (ED) with acute exacerbations of chronic obstructive pulmonary disease (COPD) and to determine whether admissions were concordant with recommendations in the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines. Methods The authors performed a prospective multicenter cohort study involving 29 EDs in the United States and Canada. By using a standard protocol, consecutive ED patients with COPD exacerbation were interviewed, and their charts were reviewed. Predictors of admission were determined by multivariate logistic regression. Results Of 384 patients, 233 (61%; 95% confidence interval = 56% to 66%) were admitted. Multivariate analysis showed that a higher likelihood of admission was associated with older age, female gender, more pack-years of smoking, recent use of inhaled corticosteroid, self-reported activity limitation in the past 24 hours, higher respiratory rate at ED presentation, and a concomitant diagnosis of pneumonia. Patients who reported the ED as their usual site for problem COPD care, or who had mixed COPD and asthma, were less likely to be admitted. The authors confirmed five of the seven testable indications for hospital admission in the GOLD guidelines. Conclusions Several patient factors were independently associated with hospital admission among ED patients with COPD exacerbations. Overall, concordance with admission recommendations in the GOLD guidelines was high. The authors also identified a few novel predictors of admission (female gender, ED as the usual site for problem COPD care, mixed diagnosis of COPD and asthma, recent use of inhaled corticosteroid) that require replication in future studies. [source]

    A correlation found between gold concentration in blood and patch test reactions in patients with coronary stents

    CONTACT DERMATITIS, Issue 3 2008
    Susanne Ekqvist
    Background:, Patients with dental gold restorations are known to have a higher level of gold concentration in blood (B-Au). Objectives:, To further investigate, in a study on patients with intracoronary stents and contact allergy to metals, the gold and nickel release from stainless steel stent with (Au stent) and without (Ni stent) gold plating. Method:, A total of 460 patients treated with stenting underwent patch testing with metals, and information on gold and nickel exposure and blood samples were collected. About 200 blood samples were randomly selected and the analysis of B-Au and nickel concentration in blood (B-Ni) was made using inductively coupled plasma mass spectrometry. Results:, There was a correlation between the intensity of Au patch test reaction and B-Au (P < 0.001). This correlation could not be seen between Ni patch test reaction and B-Ni. A Au stent gave a fivefold higher B-Au than a Ni stent. Conclusions:, Gold is released from the Au stent and patients with a Au stent have a fivefold higher B-Au than patients with an Ni stent. The patch test reactions for gold were correlated with B-Au. [source]

    Rushing for Gold: Mobility and Small-Scale Mining in East Africa

    Jesper Bosse Jønsson
    ABSTRACT African rural dwellers have faced depressed economic prospects for several decades. Now, in a number of mineral-rich countries, multiple discoveries of gold and precious stones have attracted large numbers of prospective small-scale miners. While their ,rush' to, and activities within, mining sites are increasingly being noted, there is little analysis of miners' mobility patterns and material outcomes. In this article, on the basis of a sample survey and interviews at two gold-mining sites in Tanzania, we probe when and why miners leave one site in favour of another. Our findings indicate that movement is often ,rushed' but rarely rash. Whereas movement to the first site may be an adventure, movement to subsequent sites is calculated with knowledge of the many risks entailed. Miners spend considerable time at each site before migrating onwards. Those with the highest site mobility tend to be more affluent than the others, suggesting that movement can be rewarding for those willing to ,try their luck' with the hard work and social networking demands of mining another site. [source]

    IMF Gold and the World Bank's Unfunded HIPC Deficit

    Jonathan E. Sanford
    The World Bank is to forgive $12.24 billion in IDA debt payments from HIPC borrowers. It has received $1 billion from the HIPC Trust Fund to help offset these losses, but still has a $11.6 billion unfunded liability. The IMF has gold worth $38 billion on hand for which it has no actual use. This article proposes that a small portion of IMF gold be sold annually, just enough to offset IDA's annual HIPC deficit, over the next twenty years. The new money would be additional and predictable, and would eliminate the prospect that IDA would have to cut back its future flow of aid because the HIPC programme had drained its resources. [source]

    Gas Diffusion Electrodes for Use in an Amperometric Enzyme Biosensor

    ELECTROANALYSIS, Issue 21 2008
    Martin Hämmerle
    Abstract The preparation of gas diffusion electrodes and their use in an amperometric enzyme biosensor for the direct detection of a gaseous analyte is described. The gas diffusion electrodes are prepared by covering a PTFE membrane (thickness 250,,m, pore size 2,,m, porosity 35%) with gold, platinum, or a graphite/PTFE mixture. Gold and platinum are deposited by e-beam sputtering, whereas the graphite/PTFE layer is prepared by vacuum filtration of a respective aqueous suspension. These gas diffusion electrodes are exemplarily implemented as working electrodes in an amperometric biosensor for gaseous formaldehyde containing NAD-dependent formaldehyde dehydrogenase from P. putida [EC.] as enzyme and 1,2-naphthoquinone-4-sulfonic acid as electrochemical mediator. The resulting sensors are compared with regard to background current, signal noise, linear range, sensitivity, and detection limit. In this respect, sensors with gold or graphite/PTFE covered membranes outclass ones with platinum for this particular analyte and sensor configuration. [source]

    Pulsed Amperometric Detection of Histamine at Glassy Carbon Electrodes Modified with Gold Nanoparticles

    ELECTROANALYSIS, Issue 4 2005
    V. Carralero
    Abstract Gold nanocrystal-modified glassy carbon electrodes (nAu-GCE) were prepared and used for the determination of histamine by flow injection and high performance liquid chromatography using pulsed amperometric detection (PAD) as the detection mode. Experimental variables involved in the electrodeposition process of gold from a HAuCl4 solution were optimized. A catalytic enhancement of the histamine voltammetric response was observed at the nAu-GCE when compared with that obtained at a conventional Au disk electrode, as a consequence of the microdispersion of gold nanocrystals on the GC substrate. The morphological and electrochemical characteristics of the nAu-GCE were evaluated by SEM and cyclic voltammetry. PAD using a very simple potential waveform consisting of an anodic potential (+700,mV for 500,ms) and a cathodic potential (,300,mV for 30,ms), was used to avoid the electrode surface fouling when histamine was detected under flowing conditions. Flow injection amperometric responses showed much higher Ip values and signal-to-noise ratios at the nAu-GCE than at a conventional gold disk electrode. A limit of detection of 6×10,7,mol L,1 histamine was obtained. HPLC-PAD at the nAu-GCE was used for the determination of histamine in the presence of other biogenic amines and indole. Histamine was determined in sardine samples spiked at a 50,,g g,1 concentration level, with good results. Furthermore, the chromatographic PAD method was also used for monitoring the formation of histamine during the decomposition process of sardine samples. [source]

    A New Optically Reflective Thin Layer Electrode (ORTLE) Window: Gold on a Thin Porous Alumina Film Used to Observe the Onset of Water Reduction

    ELECTROANALYSIS, Issue 1-2 2004

    Abstract The fabrication and unique characteristics of a new type of thin layer electrode, an optically reflective thin layer electrode (ORTLE), are described. The electrode was fabricated by the anodization of a thin layer of aluminum sputtered onto a plain glass microscope slide to create a 750,nm-thick porous alumina film. A thin film of gold was then sputtered atop the porous and transparent alumina film. The gold layer remained porous to allow solution into the pores but was optically thick and reflective. Reflectance measurements made through the microscope slide did not interrogate the bulk solution, but show spectral features that shift with the optical properties of the material filling the pores of the alumina film. A simple series of experiments, in which the potential of the ORTLE was stepped negatively to various values in an aqueous sodium sulfate solution, shows that interference fringes shift measurably in the ORTLE spectrum at potentials several hundred millivolts positive of the potential at which gas evolution was visible to the naked eye. [source]

    Gold nanoparticle-enhanced capillary electrophoresis-chemiluminescence assay of trace uric acid

    ELECTROPHORESIS, Issue 15 2009
    Shulin Zhao
    Abstract A sensitive method based on gold nanoparticle-enhanced CE-chemiluminescence (CL) detection was developed for quantifying uric acid (UA) in serum. In this work, gold nanoparticles were added into the running buffer of CE to catalyze the post-column CL reaction between luminol and hydrogen peroxide, achieving highly efficient CL emission. Negative peaks were produced due to the inhibitory effects on CL emission from UA eluted from the electrophoretic capillary. The decrease in CL intensity was proportional to the concentration of UA in the range of 2.5×10,7,1.0×10,5,M. Detection limit was 4.6×10,8,M UA. Ten human serum samples were analyzed by the presented method. Serum level of UA was found to be in the range from 204 to 324,,M for healthy subjects (n=5), and from 464 to 497,,M for diabetic patients (n=5). The two groups were significantly different (p<0.05). The results suggested a potential application of the proposed assay in rapid primary diagnosis of diseases such as diabetes. [source]

    Optimization of a single-effect evaporation system to effectively utilize thermal energy

    Raafat Alnaizy
    Abstract Wastewater treatment facilities at Emirates Gold in Dubai seek to improve the steam economy of the existing single-effect with recirculation and vapor-compression evaporation process. Maximizing steam economy is important as it impacts treatment costs. There are two main approaches for improving steam economy in evaporators. One is to use a multiple-effect evaporator; the other is to use a mechanical vapor recompression. Multiple-effect evaporators were rejected because of higher capital and power cost. One of the suggestions that were made towards improving the steam economy was to recover heat from the steam condensate. A modified process flow diagram was proposed and investigated. The modified process was simulated using SuperPro Designer and Hysys with complete material and energy balance computation. The modified process increased the total water evaporation capacity and gained 40% better steam economy of the process. Another advantage was an increase in the amount of water reused, which is both economical and environmentally friendly. © 2008 American Institute of Chemical Engineers Environ Prog, 2009 [source]

    Mono-, Bi-, Tri- and Tetranuclear Palladium(II), Copper(I), and Gold(I) Complexes of Morpholine- and N -Methylpiperazine-Functionalized Cyclodiphosph(III)azans, cis -[(tBuN-,)2(PNC4H8X)2] (X = O, NMe)

    Maravanji S. Balakrishna
    Abstract Bis(amido)cyclodiphosphazanes, cis -[(tBuN-,)2(PNC4H8O)2] (2) and cis -[(tBuN-,)2(PNC4H8NMe)2] (3) were synthesized by treating the corresponding amines with cis -[ClP(tBuN-,)2PCl] (1). The stoichiometric reactions of 2 or 3 with elemental sulfur and selenium afforded the bis-chalcogenides, cis -[(tBuN-,)2(P(E)NC4H8X)2] (X = O, E = S; 4, X = NMe, E = S; 5, X = O, E = Se; 6, X = O, E = Se; 7). The reactions of 2 or 3 with [PdCl2(SMe2)2] produced exclusively the mononuclear trans -[PdCl2{(tBuN-,)2(PNC4H8X)2}2] (X = O; 8, X = NMe; 9), whereas the reactions with [Pd(,-Cl)(,3 -C3H5)]2 afforded the bimetallic complexes [{PdCl(,3 -C3H5)}2{(tBuN-,)2(PNC4H8X)2}] (X = O; 10, X = NMe; 11) in good yield. Treatment of 2 or 3 with [AuCl(SMe2)] in 1:1 and 1:2 molar ratios yielded the mono- and binuclear complexes, [{AuCl(tBuN-,)2(PNC4H8O)2}] (X = O; 12, X = NMe; 13), [{AuCl}2{(tBuN-,)2(PNC4H8O)2}] (X = O; 14, X = NMe; 15), respectively. The PdII (8) and AuI (12) complexes were used as metallo-ligands to prepare homo- and heterometallic complexes, trans -[PdCl2{(tBuN-,)2(PNC4H8O)2}2{Pd(,3 -C3H5)Cl}2] (16), trans -[PdCl2{(tBuN-,)2(PNC4H8O)2}2(AuCl)2] (17), and [Cu(CH3CN)(,-Cl)2Cu(CH3CN){(tBuN-,)2(PNC4H8O)2}2(AuI)2](18). The crystal structures of 2, 4, 7,9, 14, 15, and 18 were established by single-crystal X-ray diffraction studies. [source]

    Dual Luminescent Dinuclear Gold(I) Complexes of Terpyridyl-Functionalized Alkyne Ligands and Their Efficient Sensitization of EuIII and YbIII Luminescence

    Xiu-Ling Li
    Abstract Reaction of (tpyC6H4C,CAu)n {tpyC6H4C,CH = 4,-(4-ethynylphenyl)-2,2,:6,,2,-terpyridine} with diphosphane ligands Ph2P(CH2)xPPh2 (x = 2 dppe, 3 dppp, 4 dppb, 5 dpppen, 6 dpph) in CH2Cl2 afforded the corresponding dual luminescent binuclear gold(I) complexes [(tpyC6H4C,CAu)2(,-dppe)] (1), [(tpyC6H4C,CAu)2(, - dppp)] (2), [(tpyC6H4C,CAu)2(,-dppb)] (3), [(tpyC6H4C,CAu)2(,-dpppen)] (4), [(tpyC6H4C,CAu)2(,-dpph)] (5). Crystal structural analysis of complexes 1·2CH2Cl2 and 2·2CH2Cl2 show that the terpyridine moieties are free of coordination in these gold(I)-acetylide-phosphane complexes. Spectrophotometric titration between complex 1 and [Eu(tta)3] (Htta = 2-thenoyltrifluoroacetone) or [Yb(hfac)3(H2O)2] (Hhfac = hexafluoroacetylacetone) gave a 2:1 ratio between Ln(,-diketonate)3 (Ln = Eu, Yb) units and the complex 1 moiety, indicating the formation of Au2Ln2 complexes. Both the luminescence titrations and the luminescence quantum yields of Au2Ln2 (Ln = Eu, Yb) solutions show that the energy transfer occurs efficiently from the binuclear gold(I) antennas 1,5 to EuIII and YbIII centers, and all complexes 1,5 are good energy donors for sensitization of visible and NIR luminescence of EuIII and YbIII ions. [source]

    Gold(I) Complexes of P,N Ligands and Their Catalytic Activity

    Chosu Khin
    Abstract Gold(I) complexes were readily prepared by reaction of the respective ligands with (Me2S)AuCl in CH2Cl2. Complexes of formula LAuCl {L = diphenyl(2-pyridyl)phosphane (PPh2Py), (R)-(+)-4-[(2)-(diphenylphosphanyl)-1-naphthyl]- N -[(R)-1-phenylethyl]-1-phthalazinamine (PINAP)} were obtained when a 1:1 molar ratio of ligand to starting gold precursor was used. When a 2:1 ratio of ligand to gold precursor was used with PPh2Py or MandyPhos as ligands, complexes of the type L2AuCl were obtained. All complexes were fully characterized, and single-crystal X-ray structures could be determined for four complexes. Chloride ions were removed by reaction with silver salts, such as AgNTf2, AgOTf and AgBF4, for the use of these complexes as catalysts. After the catalytic reaction with alkynes and alcohols in acetonitrile, a unique trinuclear gold(I) complex derived from [(PPh2Py)Au]BF4 could be characterized by X-ray structural analysis, showing a mode of catalyst deactivation. [source]

    Study of the Effect of the Phosphane Bridging Chain Nature on the Structural and Photophysical Properties of a Series of Gold(I) Ethynylpyridine Complexes

    Montserrat Ferrer
    Abstract Alkynyl AuI complexes of the type [Au(C,CC5H4N)(PPh3)] (1) [Au2(C,CC5H4N)2 (diphosphane)] [diphosphane = bis(diphenylphosphanyl)methane (2), bis(diphenylphosphanyl)isopropane] (3), bis(diphenylphosphanyl)acetylene (4), 1,2-bis(diphenylphosphanyl)ethane (5), 1,3-bis(diphenylphosphanyl)propane (6), 1,4-bis(diphenylphosphanyl)butane (7), 1,1,-bis(diphenylphosphanyl)ferrocene (8) and [Au3(C,CC5H4N)3(triphos)] [triphos = 1,1,1-tris(diphenylphosphanylmethyl)ethane] (9) were prepared by reaction of [Au(C,CC5H4N)]n with the suitable phosphane. Determination of the X-ray crystal structures of several compounds bearing different carbon backbones between the phosphorus atoms reveals the influence of the nature of the phosphane spacer on the establishment of intra and/or intermolecular gold,gold interactions. The absorption and emission properties of the complexes were analysed by taking into account the presence or absence of intermetallic interactions. Although UV/Vis spectra show differences for compounds with intramolecular Au,Au contacts, a conclusive trend was not observed in the emission behaviour. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Luminescent Gold(I) and Copper(I) Phosphane Complexes Containing the 4-Nitrophenylthiolate Ligand: Observation of ,,,* Charge-Transfer Emission

    Cheng-Hui Li
    Abstract Gold(I) and copper(I) phosphane complexes containing the 4-nitrophenylthiolate ligand, namely [(PCy3)Au(SC6H4NO2 -4)] (1) (PCy3 = tricyclohexylphosphane), [Au2(,-dcpm)(SC6H4NO2 -4)2] (2) [dcpm = bis(dicyclohexylphosphanyl)methane], [Au2(,-dppm)(SC6H4NO2 -4)2] (3) [dppm = bis(diphenylphosphanyl)methane], and [(,2 -SC6H4NO2 -4)2(,3 -SC6H4NO2 -4)2(CuPPh3)4] (4), were prepared and characterized by X-ray crystal analysis. All of these complexes show an intense absorption band with ,max at 396,409 nm attributed to the intraligand (IL) ,(S),,*(C6H4NO2 -4) charge-transfer transition. The assignment is supported by the results of DFT and TDDFT calculations on the model complexes [PH3Au(SC6H4NO2 -4)] and [(,2 -SC6H4NO2 -4)2(,3 -SC6H4NO2 -4)2(CuPH3)4]. The emissions of solid samples and glassy solutions (methanol/ethanol, 1:4, v/v) of 1,4 at 77 K are assigned to the [,(S),,*(C6H4NO2 -4)] charge-transfer excited state. Metallophilic interactions are not observed in both solid state and solutions of complexes 1,3. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    First Example of a Gold(I) N -Heterocyclic-Carbene-Based Initiator for the Bulk Ring-Opening Polymerization of L -Lactide

    Lipika Ray
    Abstract Synthesis, structure, and catalysis studies of two Au- and Ag-based initiators, namely, [3-(N - tert -butylacetamido)-1-(2-hydroxycyclohexyl)imidazol-2-ylidene]AuCl (1c) and [3-(N - tert -butylacetamido)-1-(2-hydroxycyclohexyl)imidazol-2-ylidene]AgCl (1b), for the bulk ring-opening polymerization of L -lactide are reported. Specifically, gold complex 1c was obtained from silver complex 1b by the transmetalation reaction with (SMe2)AuCl. Silver complex 1b was synthesized by the treatment of 3-(N - tert -butylacetamido)-1-(2-hydroxycyclohexyl)imidazolium chloride (1a) with Ag2O. Compound 1a was synthesized directly from the reaction of N - tert -butyl-2-chloroacetamide, cyclohexene oxide, and imidazole. The molecular structures of 1a, 1b, and 1c have been determined by X-ray diffraction studies. The formation of neutral monomeric complexes with linear geometries at the metal centers was observed for both 1b and 1c. The Au and Ag complexes 1c and 1b successfully catalyzed the bulk ring-opening polymerization of L -lactide at elevated temperatures under solvent-free melt conditions to produce moderate to low molecular weight polylactide polymers with narrow molecular weight distributions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    A Facile One-Step Synthesis of a Lipophilic Gold(I) Carbene Complex ,X-ray Crystal Structures of LAuCl and LAuC,CH (L = 1,3-di- tert- Butylimidazol-2-ylidene)

    Sanjay Singh
    Abstract The reaction of Au(CO)Cl with 1,3-di- tert -butylimidazol-2-ylidene and 1,3-dimesitylimidazol-2-ylidene in toluene at room temperature results in CO evolution and readily affords in high yield the adducts 1a and 1b, respectively. The reaction of 1a and 1b with ethynylmagnesium chloride in THF yields 2a and 2b, respectively. The crystal structures of 1a, 1b, and 2a were determined. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

    Gold(I)-Catalyzed Tandem Rearrangement,Nucleophilic Substitution of ,-Acetoxy Alkynyl Oxiranes or Aziridines: Efficient Approach to Furans and Pyrroles

    Aurélien Blanc
    Abstract Highly substituted furans and pyrroles were efficiently formed by a new gold(I)-catalyzed tandem rearrangement,nucleophilic substitution of acetoxylated alkynyl oxiranes and aziridines in the presence of various nucleophiles. [source]