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Gold catalysis

Leonora Velleman, Debabrata Sikdar, Vladimir A Turek, Anthony R Kucernak, Steve J Roser, Alexei A Kornyshev, Joshua B Edel
Understanding the structure and assembly of nanoparticles at liquid|liquid interfaces is paramount to their integration into devices for sensing, catalysis, electronics and optics. However, many difficulties arise when attempting to resolve the structure of such interfacial assemblies. In this article we use a combination of X-ray diffraction and optical reflectance to determine the structural arrangement and plasmon coupling between 12.8 nm diameter gold nanoparticles assembled at a water|1,2-dichloroethane interface...
October 19, 2016: Nanoscale
Fumiya Kikuchi, Yugo Kato, Kazuo Furihata, Toshihiro Kogure, Yuki Imura, Etsuro Yoshimura, Michio Suzuki
Gold nanoparticles have particular properties distinct from those of bulk gold crystals, and such nanoparticles are used in various applications in optics, catalysis, and drug delivery. Many reports on microbial synthesis of gold nanoparticles have appeared. However, the molecular details (reduction and dispersion) of such synthesis remain unclear. In the present study, we studied gold nanoparticle synthesis by Lactobacillus casei. A comparison of L. casei components before and after addition of an auric acid solution showed that the level of unsaturated lipids decreased significantly after addition...
October 11, 2016: Scientific Reports
Aurélien Blanc, Valérie Bénéteau, Jean-Marc Weibel, Patrick Pale
Silver and gold have become incredibly versatile and mild catalysts for numerous transformations, especially in heterocycle synthesis. For the most prominent of them, i.e. furans, silver and gold, with their unique reactivity and mildness, allow numerous possible routes to highly substituted and/or functionalized furans from a large variety of starting materials. Silver and gold catalysis provide thus the most flexible way to this important family of compounds. The present review describes these silver and gold-catalyzed routes, with some emphasis on mechanistic aspects, and proposes a comparison of both the silver and the gold-catalyzed syntheses of furans...
October 4, 2016: Organic & Biomolecular Chemistry
Mingyue Liu, Libing Wang, Renliang Huang, Yanjun Yu, Rongxin Su, Wei Qi, Zhimin He
Bionanomaterials synthesized by bio-inspired templating methods have emerged as a novel class of composite materials with varied applications in catalysis, detection, drug delivery, and biomedicine. In this study, two kinds of cross-linked lysozyme crystals (CLLCs) of different sizes were applied for the in situ growth of Au nanoparticles (AuNPs). The resulting composite materials were characterized by light microscopy, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy...
October 8, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Fei Pan, Chao Shu, Long-Wu Ye
N-Containing tricyclic compounds, especially the tricyclic N-heterocycles, are important structural motifs that possess significant potential in organic chemistry for their momentous applications in natural and man-made bioactive molecules. Gold catalysis, which exhibits specific catalytic properties in terms of both high reactivity and selectivity for various organic transformations, has proven to be a powerful tool for the straightforward synthesis of cyclic compounds, especially the polycyclic molecules...
October 12, 2016: Organic & Biomolecular Chemistry
Xiaofang Zhang, Wenjing Lin, Liyang Wen, Na Yao, Shuyu Nie, Lijuan Zhang
Unimolecular polymeric micelles have several features, such as thermodynamic stability, small particle size, biocompatibility, and the ability to internalize hydrophobic molecules. These micelles have recently attracted significant attention in various applications, such as nano-reactors, catalysis, and drug delivery. However, few attempts have explored the formation mechanisms and conditions of unimolecular micelles due to limited experimental techniques. In this study, a unimolecular micelle system formed from β-cyclodextrin-graft-{poly(lactide)-block-poly(2-(dimethylamino) ethyl multimethacrylate)-block-poly[oligo (2-ethyl-2-oxazoline) methacrylate]} β-CD-g-(PLA-b-PDMAEMA-b-PEtOxMA) star-like block copolymers in aqueous media was investigated by dissipative particle dynamics (DPD) to explore the formation process of unimolecular micelles...
September 29, 2016: Physical Chemistry Chemical Physics: PCCP
Xiaoping Chen, Qiaoling Wang, Biao Yu
C-Glycosylation of glycosyl ortho-hexynylbenzoates with allyltrimethylsilane or silyl enol ethers could proceed smoothly under the catalysis of Ph3PAuNTf2 to provide the corresponding C-glycosides in high yields and stereoselectivity, wherein the moisture sequestered by the molecular sieves was disclosed to play a critical role in the gold(i)-catalytic cycle.
October 6, 2016: Chemical Communications: Chem Comm
Azusa Kondoh, Sho Ishikawa, Takuma Aoki, Masahiro Terada
An efficient synthetic method for 2,3-allenylamides having an oxygen functionality at the 2-position, which are difficult to access by conventional methods, was newly developed by utilizing the [1,2]-phospha-Brook rearrangement under Brønsted base catalysis. Further manipulation of the 2,3-allenylamides via gold-catalyzed cycloisomerization enables the formation of 2-aminofuran derivatives.
October 13, 2016: Chemical Communications: Chem Comm
Liyan Zhang, Shuai Li, Minmin Dong, Yao Jiang, Ru Li, Shuo Zhang, Xiaoxia Lv, Lijun Chen, Hua Wang
A facile and efficient enzymatic reconstitution methodology has been proposed for high-catalysis peroxidase mimics by remolding the redox active centers of heme-containing proteins with the in-site biomineralized gold using hemoglobin (Hb) as a model. Catalytic hemin (Hem) was extracted from the active centers of Hb for the gold biomineralization and then reconstituted into apoHb to yield the Hem-Au@apoHb nanocomposites showing dramatically improved intrinsic catalysis and electrocatalysis over natural Hb and Hem...
September 22, 2016: Biosensors & Bioelectronics
Guangfang Grace Li, Ye Lin, Hui Wang
Percolation dealloying of multimetallic alloys entangles selective dissolution of the less-noble elements with nanoscale restructuring of the more-noble components, resulting in the formation of sponge-like, nanoporous architectures with a unique set of structural characteristics highly desirable for heterogeneous catalysis. While the dealloyed nanoporous materials are compositionally dominated by the more-noble elements, they inevitably contain residual less-noble elements that cannot be completely removed through the percolation dealloying process...
October 3, 2016: Nano Letters
Adam M Kubas, Daniel Berger, Harald Oberhofer, Dimitrios Maganas, Karsten Reuter, Frank Neese
Coupled cluster theory with single, double and perturbative triple excitations (CCSD(T)) is widely considered to be the 'gold standard' of ab initio quantum chemistry. Using the domain-based pair natural orbital local correlation concept (DLPNO-CCSD(T)), these calculations can be performed on systems with hundreds of atoms at an accuracy of about 99.9% of the canonical CCSD(T) method. This allows for ab initio calculations providing reference adsorption energetics at solid surfaces with an accuracy approaching 1 kcal/mol...
October 3, 2016: Journal of Physical Chemistry Letters
Qian He, Simon J Freakley, Jennifer K Edwards, Albert F Carley, Albina Y Borisevich, Yuki Mineo, Masatake Haruta, Graham J Hutchings, Christopher J Kiely
The identity of active species in supported gold catalysts for low temperature carbon monoxide oxidation remains an unsettled debate. With large amounts of experimental evidence supporting theories of either gold nanoparticles or sub-nm gold species being active, it was recently proposed that a size-dependent activity hierarchy should exist. Here we study the diverging catalytic behaviours after heat treatment of Au/FeOx materials prepared via co-precipitation and deposition precipitation methods. After ruling out any support effects, the gold particle size distributions in different catalysts are quantitatively studied using aberration corrected scanning transmission electron microscopy (STEM)...
2016: Nature Communications
Pablo Barrio, Manish Kumar, Zhichao Lu, Junbin Han, Bo Xu, Gerald B Hammond
A systematic study on the effects of Lewis or Brønsted acid co-catalysts in gold-catalyzed reactions was undertaken using representative reactions (O-, N-, and C-nucleophilic additions to alkynes). Through these reactions, it was demonstrated that an acidic co-catalyst can increase the catalyst turnover significantly, enabling practical reaction rates at competitive catalyst loadings (<1 mol %). Further investigation is currently underway to improve the understanding of the subtle principles underlying these experimental observations...
September 19, 2016: Chemistry: a European Journal
Shibdas Banerjee, Chanbasha Basheer, Richard N Zare
We have developed nanoparticle-embedded paper-spray mass spectrometry for studying three types of heterogeneously catalyzed reactions: 1) Palladium-nanoparticle-catalyzed Suzuki cross-coupling reactions, 2) palladium- or silver-nanoparticle-catalyzed 4-nitrophenol reduction, and 3) gold-nanoparticle-catalyzed glucose oxidation. These reactions were almost instantaneous on the nanocatalyst-embedded paper, which subsequently transferred the transient intermediates and products to a mass spectrometer for their detection...
October 4, 2016: Angewandte Chemie
Rosaria Ciriminna, Ermelinda Falletta, Cristina Della Pina, Joaquim Henrique Teles, Mario Pagliaro
Gold catalysis has recently found its first large-scale applications in the chemical industry. This Minireview provides a critical analysis of the success factors and of the main obstacles that had to be overcome on the long way from the discovery to the commercialization of gold catalysts. The insights should be useful to researchers in both academia and industry working on the development of tomorrow's gold catalysts to tackle significant environmental and economic issues.
September 14, 2016: Angewandte Chemie
Matthew N Hopkinson, Adrian Tlahuext-Aca, Frank Glorius
Since the beginning of this century, π-Lewis acidic gold complexes have become the catalysts of choice for a wide range of organic reactions, especially those involving nucleophilic addition to carbon-carbon multiple bonds. For the most part, however, the gold catalyst does not change oxidation state during the course of these processes and two-electron redox cycles of the kind implicated in cross-coupling chemistry are not easily accessible. In order to address this limitation and expand the scope of gold catalysis beyond conventional hydrofunctionalization, extensive efforts have been made to develop new oxidative reactions using strong external oxidants capable of overcoming the high potential of the Au(I)/Au(III) redox couple...
October 18, 2016: Accounts of Chemical Research
Alexander Preinfalk, Antonio Misale, Nuno Maulide
The reaction of aryl-substituted allenes with alcohols under gold catalysis led to highly substituted indenes in good yields, with low catalyst loading and under mild conditions. During this domino transformation, two C-C bonds are formed with water as the only byproduct.
October 4, 2016: Chemistry: a European Journal
Stephanus T Malherbe, Shubhada Shenai, Katharina Ronacher, Andre G Loxton, Gregory Dolganov, Magdalena Kriel, Tran Van, Ray Y Chen, James Warwick, Laura E Via, Taeksun Song, Myungsun Lee, Gary Schoolnik, Gerard Tromp, David Alland, Clifton E Barry, Jill Winter, Gerhard Walzl, Lance Lucas, Gian van der Spuy, Kim Stanley, Lani Theart, Bronwyn Smith, Nelita Burger, Caroline G G Beltran, Elizna Maasdorp, Annare Ellmann, Hongjo Choi, Joonsung Joh, Lori E Dodd, Brian Allwood, Coenie Kogelenberg, Morné Vorster, Stephanie Griffith-Richards
The absence of a gold standard to determine when antibiotics induce a sterilizing cure has confounded the development of new approaches to treat pulmonary tuberculosis (PTB). We detected positron emission tomography and computerized tomography (PET-CT) imaging response patterns consistent with active disease, along with the presence of Mycobacterium tuberculosis (MTB) mRNA in sputum and bronchoalveolar lavage samples, in a substantial proportion of adult, HIV-negative patients with PTB after a standard 6-month treatment plus 1 year follow-up, including patients with a durable cure and others who later developed recurrent disease...
October 2016: Nature Medicine
Tobias A Engesser, Christian Friedmann, Arthur Martens, Daniel Kratzert, Przemysław J Malinowski, Ingo Krossing
A series of gold acetonitrile complexes [Au(NCMe)2 ](+) [WCA](-) with weakly coordinating counterions (WCAs) was synthesized by the reaction of elemental gold and nitrosyl salts [NO](+) [WCA](-) in acetonitrile ([WCA](-) =[GaCl4 ](-) , [B(CF3 )4 ](-) , [Al(OR(F) )4 ](-) ; R(F) =C(CF3 )3 ). In the crystal structures, the [Au(NCMe)2 ](+) units appeared as monomers, dimers, or chains. A clear correlation between the aurophilicity and the coordinating ability of counterions was observed, with more strongly coordinating WCAs leading to stronger aurophilic contacts (distances, C-N stretching frequencies of [Au(NCMe)2 ](+) units)...
October 10, 2016: Chemistry: a European Journal
Rongchao Jin, Chenjie Zeng, Meng Zhou, Yuxiang Chen
Colloidal nanoparticles are being intensely pursued in current nanoscience research. Nanochemists are often frustrated by the well-known fact that no two nanoparticles are the same, which precludes the deep understanding of many fundamental properties of colloidal nanoparticles in which the total structures (core plus surface) must be known. Therefore, controlling nanoparticles with atomic precision and solving their total structures have long been major dreams for nanochemists. Recently, these goals are partially fulfilled in the case of gold nanoparticles, at least in the ultrasmall size regime (1-3 nm in diameter, often called nanoclusters)...
September 28, 2016: Chemical Reviews
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