Identity of the Active Site in Gold Nanoparticle-Catalyzed Sonogashira Coupling of Phenylacetylene and Iodobenzene

Beaumont, Simon K.; Kyriakou, Georgios; Lambert, Richard M.

doi:10.1021/ja1063179

Cited by 126 publications

(87 citation statements)

References 23 publications

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“…. The BE peak at ~402.80 eV (higher than typically observed for amines BE= ~399 eV -400.5 eV and much more for -NH 2 + group) for N1s is an indication of C-O-NH 2 + structure whereas the O atom peak at ~534.40 eV shows the same 39,40 . These results strongly indicate H-bonding interactions between the amine group of the API and ester/carboxyl group of the polymer (L100) (Fig.…”

Section: Flory Huggins (F-h) Theory For the Prediction Of Drug/polymementioning

confidence: 64%

Molecular Modeling as a Predictive Tool for the Development of Solid Dispersions

et al. 2015

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In this study molecular modelling is introduced as a novel approach for the development of pharmaceutical solid dispersions. A computational model based on quantum mechanical (QM) calculations was used to predict the miscibility of various drugs in various polymers by predicting the binding strength between the drug and dimeric form of the polymer. The drug/polymer miscibility was also estimated by using traditional approaches such as Van Krevelen/Hoftyzer and Bagley solubility parameters or Flory Huggins interaction parameter in comparison to the molecular modelling approach.The molecular modelling studies predicted successfully the drug-polymer binding energies and the preferable site of interaction between the functional groups. The drug-polymer miscibility and the physical state of bulk materials, physical mixtures and solid dispersions were determined by thermal analysis (DSC/MTDSC) and X-ray diffraction. The produced solid dispersions were analysed by X-ray photoelectron spectroscopy (XPS), which confirmed not only the exact type of the intermolecular interactions between the drugpolymer functional groups but also the binding strength by estimating the N-coefficientvalues. The findings demonstrate that QM-based molecular modelling is a powerful tool to predict the strength and type of intermolecular interactions in a range of drug/polymeric systems for the development of solid dispersions.

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Section: Flory Huggins (F-h) Theory For the Prediction Of Drug/polymementioning

confidence: 64%

Molecular Modeling as a Predictive Tool for the Development of Solid Dispersions

et al. 2015

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“…In the present context, the ability of oxygenated silver surfaces to react with unsaturated organic adsorbates without totally disrupting them by deep oxidation-unlike the platinum group metals, which induce total combustion 14 [20][21][22][23][24] In this paper we report the first observation of the silver-catalyzed homocoupling of phenylacetylene on extended Ag(100) single crystal surfaces in vacuum and also the corresponding behavior of Ag particles in solution. STM and XPS single crystal results unambiguously established that the presence of chemisorbed oxygen was critical for efficient reaction to occur and that the crucial reaction-initiating step was abstraction of the acetylenic hydrogen atom by O(a), which caused the reaction to propagate over the entire metal surface, as opposed to being confined to island boundaries.…”

Section: Introductionmentioning

confidence: 89%

Critical Role of Oxygen in Silver-Catalyzed Glaser–Hay Coupling on Ag(100) under Vacuum and in Solution on Ag Particles

et al. 2017

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The essential role of oxygen in enabling heterogeneously catalyzed Glaser−Hay coupling of phenylacetylene on Ag(100) was elucidated by STM, laboratory and synchrotron photoemission, and DFT calculations. In the absence of coadsorbed oxygen, phenylacetylene formed well-ordered dense overlayers which, with increasing temperature, desorbed without reaction. In striking contrast, even at 120 K, the presence of oxygen led to immediate and complete disruption of the organic layer due to abstraction of acetylenic hydrogen with formation of a disordered mixed layer containing immobile adsorbed phenylacetylide. At higher temperatures phenylacetylide underwent Glaser−Hay coupling to form highly ordered domains of diphenyldiacetylene that eventually desorbed without decomposition, leaving the bare metal surface. DFT calculations showed that, while acetylenic H abstraction was otherwise an endothermic process, oxygen adatoms triggered a reaction-initiating exothermic pathway leading to OH(a) + phenylacetylide, consistent with the experimental observations. Moreover, it was found that, with a solution of phenylacetylene in nonane and in the presence of O 2 , Ag particles catalyzed Glaser−Hay coupling with high selectivity. Rigorous exclusion of oxygen from the reactor strongly suppressed the catalytic reaction. Interestingly, too much oxygen lowers the selectivity toward diphenyldiacetylene. Thus, vacuum studies and theoretical calculations revealed the key role of oxygen in the reaction mechanism, subsequently borne out by catalytic studies with Ag particles that confirmed the presence of oxygen as a necessary and sufficient condition for the coupling reaction to occur. The direct relevance of model studies to a mechanistic understanding of coupling reactions under conditions of practical catalysis was reaffirmed.

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“…[16][17][18][19][20] A suitable substrate not only provides a high surface area to stabilize small nanoparticles (NPs) under long-term catalysis but also renders hybrid junctions with rich redox reactions on the two-phase interface. With the development of synthetic techniques in nanoscience, small noble metal NPs, especially atomically precise nanoclusters/metal oxide hybrid nanostructures, have been successfully fabricated very recently, and these materials exhibit remarkable enhanced catalytic activity and selectivity.…”

Section: Introductionmentioning

confidence: 99%

CeO2-encapsulated noble metal nanocatalysts: enhanced activity and stability for catalytic application

2015

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Encapsulation of small noble metal nanoparticles has received attention owing to the resulting highly increased stability and high catalytic activity and selectivity. Among the types of inert metal oxides, CeO 2 is unique. It is inexpensive and highly stable, and, more importantly, the unique electronic configuration gives it a strong capability to provide active oxygen. The method of fabricating CeO 2 -encapsulated noble metal nanocatalysts is determined by the requirements of the application. In this review, we first describe the various types of encapsulated noble metals and then the current developments of synthesis in detail, including the types of hybrid nanostructures and successful synthetic strategies. The following section, concerning catalytic applications, is divided into three topics: anti-sintering capabilities, catalytic activities and selectivities. We hope that this review of the recent achievements and the proposed strategy for addressing the emerging challenges will inspire further developments in this research area. NPG Asia Materials (2015) 7, e179; doi:10.1038/am.2015.27; published online 8 May 2015 INTRODUCTIONNoble metal catalysts have received much attention in the past decade because of their unique chemical and physical properties, and they have been widely applied in industrial use. [1][2][3][4][5][6][7][8][9][10] With the help of noble metal catalysts, environmental friendly catalysis resulting in the decreased production of pollutants, waste minimization and new synthetic routes that circumvent modern synthetic techniques such as Sonogashira-, Heck-and Miyaura-Suzuki-type reactions can be easily realized. 11-15 However, for most technologically important chemical processes, noble metal catalysts spontaneously aggregate and grow to reduce the surface energy, which limits the catalysts' lifetime and efficiency. The ultra-high prices of noble metals have also seriously limited their further development. Because of the development of modern industry, there remains a critical need for robust, simple and readily controllable routes to fabricate highly active, stable and recyclable nanocatalysts.To maximize the catalytic performance of noble metals and reduce the quantity used, it is necessary to load the active centers on a substrate. [16][17][18][19][20] A suitable substrate not only provides a high surface area to stabilize small nanoparticles (NPs) under long-term catalysis but also renders hybrid junctions with rich redox reactions on the two-phase interface. With the development of synthetic techniques in nanoscience, small noble metal NPs, especially atomically precise nanoclusters/metal oxide hybrid nanostructures, have been successfully fabricated very recently, and these materials exhibit remarkable enhanced catalytic activity and selectivity. [21][22][23] However, this simple loading form cannot meet the growing demand for the stability, because the noble metal catalysts contain numerous exposed surfaces

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Identity of the Active Site in Gold Nanoparticle-Catalyzed Sonogashira Coupling of Phenylacetylene and Iodobenzene

Cited by 126 publications

References 23 publications

Molecular Modeling as a Predictive Tool for the Development of Solid Dispersions

Molecular Modeling as a Predictive Tool for the Development of Solid Dispersions

Critical Role of Oxygen in Silver-Catalyzed Glaser–Hay Coupling on Ag(100) under Vacuum and in Solution on Ag Particles

CeO2-encapsulated noble metal nanocatalysts: enhanced activity and stability for catalytic application

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