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Gold catalysis

Oscar Gutierrez-Sanz, Enrico Forbrig, Ana P Batista, Manuela M Pereira, Johannes Salewski, Maria Andrea Mroginski, Robert Goetz, Antonio L De Lacey, Jacek Kozuch, Ingo Zebger
Respiratory Complex I (CpI) is a key player in the way organisms obtain energy, being an energy transducer, which couples NADH:quinone oxidoreduction with proton translocation by a mechanism that remains elusive so far. In this work, we monitored the function of CpI in a biomimetic supported lipid membrane (SLM) system assembled on a 4-aminothiophenol (4-ATP) self-assembled monolayer (SAM) by surface-enhanced infrared absorption spectroscopy (SEIRAS). 4-ATP serves not only as linker molecule to a nanostructured gold-surface but also as pH sensor, as indicated by concomitant density functional theory (DFT) calculations...
March 19, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Jay K Bhattarai, Dharmendra Neupane, Bishal Nepal, Vasilii Mikhaylov, Alexei V Demchenko, Keith J Stine
Nanoporous gold (np-Au), because of its high surface area-to-volume ratio, excellent conductivity, chemical inertness, physical stability, biocompatibility, easily tunable pores, and plasmonic properties, has attracted much interested in the field of nanotechnology. It has promising applications in the fields of catalysis, bio/chemical sensing, drug delivery, biomolecules separation and purification, fuel cell development, surface-chemistry-driven actuation, and supercapacitor design. Many chemical and electrochemical procedures are known for the preparation of np-Au...
March 16, 2018: Nanomaterials
Agustina La-Venia, Mirta P Mischne, Ernesto G Mata
The gold-catalyzed intermolecular hydroalkylation of olefins with β-ketoesters represents a conceptually attractive and useful synthetic tool; however, it has been scarcely applied, remaining a challenge for chemists. The aim of the current study was to investigate the addition of these 1,3-diketo-compounds to alkenes under gold catalysis conditions, in order to establish the electronic and steric effects of the alkenyl substrates in the reaction outcome. The screening of different catalyst systems and diverse olefins enabled defining the alkenyl requirements and the best reaction conditions to efficiently achieve the coupled products...
March 10, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
David Avnir
A unique materials' methodology enables the doping of metals with functional molecules, polymers, enzymes, and nanoparticles. The resulting materials have either the combined properties of the metal and the dopants, or new, sometimes synergetic properties that are not found in the separate components, emerge. Metals that have been doped so far include gold, silver, copper, iron, gallium, palladium, platinum, and several alloys. Numerous applications have been demonstrated including catalysis, biocatalysis, bioactivity, electrochemistry (including new type of batteries), corrosion resistance, induction of chirality, tailoring unconventional properties to metals, and more...
March 12, 2018: Advanced Materials
Rajeev Ramanan, David Danovich, Debasish Mandal, Sason Shaik
Oriented external-electric-fields (OEEFs) are potent effectors of chemical change and control. We show that the Menshutkin reaction, between substituted pyridines and methyl iodide, can be catalyzed/inhibited at will, by just flipping the orientation of the EEF (FZ) along the "reaction axis" (Z), N---C---I. A theoretical analysis shows that catalysis/inhibition obey the Bell-Evans-Polanyi Principle. Significant catalysis is predicted also for EEFs oriented off the reaction axis. Hence, the observation of catalysis can be up-scaled and may not require orienting the reactants vis-à-vis the field...
March 7, 2018: Journal of the American Chemical Society
Rong Ye, Aleksandr V Zhukhovitskiy, Roman V Kazantsev, Sirine C Fakra, Brent B Wickemeyer, F Dean Toste, Gabor A Somorjai
Attachment of N-heterocyclic carbenes (NHCs) on the surface of metal nanoparticle (NP) catalysts permits fine-tuning of catalytic activity and product selectivity. Yet, NHC-coated Au NPs have been seldom used in catalysis beyond hydrogenation chemistry. One challenge in this field has been to develop a platform that permits arbitrary ligand modification with-out having to compromise NP stability toward aggregation or leaching. Herein, we exploit the strategy of supported den-drimer-encapsulated metal clusters (DEMCs) to achieve aggregation-stable yet active heterogeneous Au NP catalysts with NHC ligands...
March 5, 2018: Journal of the American Chemical Society
Jose Miguel Alonso, Maria Paz Muñoz
Heterobimetallic catalysis offers new opportunities for reactivity and selectivity but still presents challenges and only a few metal combinations have been explored so far. We have developed a Pt-Au bimetallic catalysis for the synthesis of a family of multi heteroaromatic structures through tandem cyclisation/C-X coupling reaction. Au-catalysed 6-endo-cyclisation occurs as the first fast step and Pt-Au clusters are responsible for the increased activity of the intermolecular second nucleophilic addition that occurs through an outer-sphere mechanism by hybrid homo-heterogeneous catalysis...
March 1, 2018: Angewandte Chemie
K L Dimuthu M Weerawardene, Hannu Häkkinen, Christine M Aikens
Ligand-stabilized gold and silver nanoparticles are of tremendous current interest in sensing, catalysis, and energy applications. Experimental and theoretical studies have closely interacted to elucidate properties such as the geometric and electronic structures of these fascinating systems. In this review, the interplay between theory and experiment is described; areas such as optical absorption and doping, where the theory-experiment connections are well established, are discussed in detail; and the current status of these connections in newer fields of study, such as luminescence, transient absorption, and the effects of solvent and the surrounding environment, are highlighted...
February 28, 2018: Annual Review of Physical Chemistry
Johnny Saavedra, Christopher J Pursell, Bert D Chandler
The mechanism of CO oxidation over supported gold catalysts has long been debated, with two prevailing mechanisms dominating the discussion: a water-assisted mechanism and a mechanism involving O-defect sites. In this study, we directly address this debate through a kinetic and mechanistic investigation of the role of water in CO oxidation over Au/TiO2 and Au/Al2O3 catalysts; the results clearly indicate a common water-assisted mechanism to be at work. Water adsorption isotherms were determined with infrared spectroscopy; the extracted equilibrium constant was essentially the same...
February 25, 2018: Journal of the American Chemical Society
Min Shi, Wei Fang
During the past decades, cycloisomerizations of methylenecyclopropanes under gold catalysis have attracted much attention from organic chemists. The different patterns of cycloisomerizations have been developed from gold(I)-catalyzed ring-opening and ring-expansion of methylenecyclopropanes. This synthetic methodology provides a new approach to novel cyclic- or polycyclic compounds and even polycyclic aromatic hydrocarbons, organic light emitting materials and biologically active substances. The corresponding products have great potential for material science, medicinal chemistry and total synthesis...
February 21, 2018: Chemistry: a European Journal
Yu Zhao, Fei Zhao, Lihua Kang
The mechanisms for the acetylene hydrochlorination reaction on pristine Au7 and Au8 clusters and on the Si-doped Au clusters Au6 Si and Au7 Si were systematically investigated via density functional theory using the PBE functional. The band gap (∆Eg ) of the Au7 Si cluster was found to smaller than that of its undoped equivalent (Au8 ), thus enhancing its catalytic activity, and Au7 Si presented a significantly reduced activation barrier (16.69 kcal mol-1 ) for the acetylene hydrochlorination reaction compared with the pristine Au8 cluster (21...
February 20, 2018: Journal of Molecular Modeling
Maher Sayhi, Oussama Ouerghi, Kamel Belgacem, Marwa Arbi, Yudum Tepeli, Abdeljalil Ghram, Ülkü Anik, Lars Österlund, Dhafer Laouini, Mohamed Fethi Diouani
Influenza is a viral infectious disease considered as a source of many health problems and enormous socioeconomic disruptions. Conventional methods are inadequate for in-field detection of the virus and generally suffer from being laborious and time-consuming. Thus, studies aiming to develop effective alternatives to conventional methods are urgently needed. In this work, we developed an approach for the isolation and detection of influenza A virus subtype H9N2. For this aim, two specific influenza receptors were used...
February 7, 2018: Biosensors & Bioelectronics
Julia Holz, Marta Ayerbe García, Wolfgang Frey, Felix Krupp, René Peters
In the last few decades, gold complexes have demonstrated huge potential for soft Lewis acid catalysis. Despite the intensive research on Au complexes and planar chiral metallacycles, enantiopure ferrocenylgold complexes have - surprisingly - not been reported until the studies presented in this article. Herein, we report the asymmetric synthesis of planar chiral ferrocenyl Au(i) complexes. These dinuclear species form helically chiral ten-membered (NCCCAu) 2 rings stabilized by aurophilic interactions. In supramolecular solid state structures, linear, zigzag or helical Au(i) wires with regular AuAu separations were observed...
February 16, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Minh Tran, Colton Mundt, Tian Lan, Sonal Padalkar
Gold (Au) nanostructures exhibit unique electronic, optoelectronic and plasmonic properties. This makes them potential candidates for applications in areas including biosensing, catalysis, optics, and electronics. These unique properties are governed by the precise control over their morphologies and size. The present work investigates the electrodeposition process of Au nanostructures. Additionally, the influence of applied potential, electrolyte pH and presence of L-cysteine on the morphology, size, distribution and density of Au nanostructured was studied...
May 1, 2018: Journal of Nanoscience and Nanotechnology
Krishna Kant Sharma, Deepti Singh, Surender Rawat
Laccase in Cryptococcus neoformans is covalently linked to the carbohydrate moiety of the cell wall, which allows it to get access to the different substrates for catalyzing their oxidation and therefore plays a vital role in the virulence. The laccase gene (3.0 kb) from C. neoformans serotype D was amplified, cloned and sequenced for protein modeling, docking and simulation studies. The three dimensional homology models of laccase protein from C. neoformans and other pathogenic gut bacteria were docked with selected biomolecules like prostaglandins (PG), membrane phospholipids, neurotransmitters (serotonin) using GOLD software...
February 3, 2018: Computational Biology and Chemistry
Jiangping Xu, Hang Zhou, Qing Yu, Ian Manners, Mitchell A Winnik
Nucleated self-assembly in selective solvents of core-crystalline block copolymers (BCPs) is a special case of living supramolecular polymerization, leading to rodlike micelles of controlled and uniform length. For the crystallization-driven self-assembly of PFS-containing BCPs (PFS = polyferrocenyldimethylsilane), the formation of block comicelles by sequential addition of different BCPs is well-established. But there are only a few examples of living copolymerization, the simultaneous addition of pairs of BCPs with different corona-forming chains...
February 5, 2018: Journal of the American Chemical Society
Xiang-Fei Kong, Feng Zhan, Guo-Xue He, Cheng-Xue Pan, Chen-Xi Gu, Ke Lu, Dong-Liang Mo, Gui-Fa Su
An efficient method to synthesize rutaecarpine derivatives via the gold-catalyzed selective cyclization of alkyn-tethered indoles under mild conditions is described. The alkyn-tethered indole can undergo 6-exo-dig cyclization by oxidation and sequential gold catalysis, while it goes through 7-endo-dig cyclization by gold catalysis and sequential oxidation. Substrate scope studies reveal that the selectivity of cyclization was controlled by the substrates with sp3 and sp2 hybridization of carbon at the 2 position in quinazolinone...
February 2, 2018: Journal of Organic Chemistry
Mingyun Zhu, Yunqian Dai, Wanlin Fu, Yanan Wu, Xixi Zou, Tengye You, Yueming Sun
Gold nanoparticles (Au NPs) have attracted remarkable research interests in heterogeneous catalysis due to their unique physical and chemical properties. However, only small-size Au NPs (<7 nm) exhibit promising catalytic activity. In this work, dumbbell-like Au NPs (D-Au NPs) with average size of 37 × 11 nm were prepared by a secondary seed-mediated growth method to serve as novel photocatalyst for ammonia borane (AB) hydrolysis in the solution with specific pH value. Our results demonstrate that ⅰ) the strengthened LSPR compensation effect could effectively remedy the loss of catalytic activity resulting from the size enlarging of D-Au NPs, proven by that the heating power of a single Au nanoparticle (Ps) and turnover frequency of AB molecules within 10 minutes of D-Au NPs are 52...
January 31, 2018: Nanotechnology
Yubiao Niu, Philomena Schlexer, Bela Sebok, Ib Chorkendorff, Gianfranco Pacchioni, Richard E Palmer
Au nanoparticles represent the most remarkable example of a size effect in heterogeneous catalysis. However, a major issue hindering the use of Au nanoparticles in technological applications is their rapid sintering. We explore the potential of stabilizing Au nanoclusters on SiO2 by alloying them with a reactive metal, Ti. Mass-selected Au/Ti clusters (400 000 amu) and Au2057 clusters (405 229 amu) were produced with a magnetron sputtering, gas condensation cluster beam source in conjunction with a lateral time-of-flight mass filter, deposited onto a silica support and characterised by XPS and LEIS...
January 12, 2018: Nanoscale
Daniel Muñoz-Santiburcio, Matteo Farnesi Camellone, Dominik Marx
Gold/titania catalysts are widely used for key reactions, notably including the selective oxidation of alcohols in the liquid phase. Our large-scale ab initio simulations disclose that the liquid-phase reaction mechanism is distinctly different from that in the gas phase due to active participation of water molecules. While concerted charge transfers related to O₂ splitting and abstraction of both, protonic and hydridic hydrogens are enforced under dry conditions, stepwise charge transfer is preferred in the condensed phase...
January 11, 2018: Angewandte Chemie
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