scholarly journals A novel strategy for stabilization of sub-nanometric Pd colloids on kryptofix functionalized MCM-41: nanoengineered material for Stille coupling transformation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hassan Alamgholiloo ◽  
Nader Noroozi Pesyan ◽  
Sadegh Rostamnia
Keyword(s):  
Catalytic Activity ◽  
Large Scale ◽  
Coupling Reaction ◽  
Vital Role ◽  
Metal Particles ◽  
Stille Coupling ◽  
Coupling Transformation ◽  
Novel Strategy ◽  
Average Size ◽  
Mcm 41

AbstractThe stabilization of sub-nanometric metal particles (< 1 nm) with suitable distribution remained challenging in the catalytic arena. Herein, an intelligent strategy was described to anchoring and stabilizing sub-nanometric Pd colloids with an average size of 0.88 nm onto Kryptofix 23 functionalized MCM-41. Then, the catalytic activity of Pd@Kryf/MCM-41 was developed in Stille coupling reaction with a turnover frequency (TOF) value of 247 h−1. The findings demonstrate that porous MCM-41 structure and high-affinity Kryptofix 23 ligand toward adsorption of Pd colloids has a vital role in stabilizing the sub-nanometric particles and subsequent catalytic activity. Overall, these results suggest that Pd@Kryf/MCM-41 is a greener, more suitable option for large-scale applications and provides new insights into the stabilization of sub-nanometric metal particles.

Synthesis of terminal arylacetylenes by a Stille coupling reaction catalysed by a MCM-41-supported bidentate phosphine palladium(O) complex

2008 ◽  
Vol 2008 (11) ◽  
pp. 615-618 ◽  
Author(s):  
Wenyan Hao ◽  
Yue Wang ◽  
Shouri Sheng ◽  
Mingzhong Cai
Keyword(s):  
Aqueous Medium ◽  
Palladium Catalyst ◽  
Basic Problem ◽  
Coupling Reaction ◽  
Aryl Halides ◽  
Stille Coupling ◽  
Bidentate Phosphine ◽  
Stille Coupling Reaction ◽  
High Yields ◽  
Mcm 41

A variety of terminal arylacetylenes have been conveniently synthesised in good to high yields by Stille coupling of aryl halides with ethynyltributylstannane catalysed by a MCM-41-supported bidentate phosphine palladium(O) complex in an aqueous medium and under air. Our system not only avoids the requirement for water-free and oxygen-free conditions, but also solves the basic problem of palladium catalyst reuse.

The design and catalytic performance of molybdenum active sites on an MCM-41 framework for the aerobic oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran

2019 ◽  
Vol 9 (3) ◽  
pp. 811-821 ◽  
Author(s):  
Zhao-Meng Wang ◽  
Li-Juan Liu ◽  
Bo Xiang ◽  
Yue Wang ◽  
Ya-Jing Lyu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Aerobic Oxidation ◽  
Catalytic Performance ◽  
Mcm 41

The catalytic activity decreases as –(SiO)3Mo(OH)(O) > –(SiO)2Mo(O)2 > –(O)4–MoO.

Nickel (II) and oxovanadium (IV) complexes supported on MCM-41 mesoporous and their application in catalytic selective sulfide and thiol oxidation

2020 ◽  
Vol 23 ◽  
Author(s):  
Mohsen Nikoorazm ◽  
Maryam Khanmoradi ◽  
Masoumeh Sayadian
Keyword(s):  
Catalytic Activity ◽  
Room Temperature ◽  
Sol Gel ◽  
Reaction Times ◽  
Significant Loss ◽  
Spectral Studies ◽  
High Catalytic Activity ◽  
Catalytic Systems ◽  
Solvent Free Conditions ◽  
Mcm 41

Introduction:: MCM-41 was synthesized using the sol-gel method. Then two new transition metal complexes of Nickel (II) and Vanadium (IV), were synthesized by immobilization of adenine (6-aminopurine) into MCM-41 mesoporous. The compounds have been characterized by XRD, TGA, SEM, AAS and FT-IR spectral studies. Using these catalysts provided an efficient and enantioselective procedure for oxidation of sulfides to sulfoxides and oxidative coupling of thiols to their corresponding disulfides using hydrogen peroxide at room temperature. Materials and Methods:: To a solution of sulfide or thiol (1 mmol) and H2O2 (5 mmol), a determined amount of the catalyst was added. The reaction mixture was stirred at room temperature for the specific time under solvent free conditions. The progress of the reaction was monitored by TLC using n-hexane: acetone (8:2). Afterwards, the catalyst was removed from the reaction mixture by centrifugation and, then, washed with dichloromethane in order to give the pure products. Results:: All the products were obtained in excellent yields and short reaction times indicating the high activity of the synthesized catalysts. Besides, the catalysts can be recovered and reused for several runs without significant loss in their catalytic activity. Conclusion:: These catalytic systems furnish the products very quickly with excellent yields and VO-6AP-MCM-41 shows high catalytic activity compared to Ni-6AP-MCM-41.

Random graphs

2018 ◽  
Author(s):  
Mark Newman
Keyword(s):  
Random Graph ◽  
Random Graphs ◽  
Large Scale ◽  
Random Network ◽  
Graph Model ◽  
Clustering Coefficient ◽  
Giant Component ◽  
Random Graph Model ◽  
Definition Of ◽  
Average Size

An introduction to the mathematics of the Poisson random graph, the simplest model of a random network. The chapter starts with a definition of the model, followed by derivations of basic properties like the mean degree, degree distribution, and clustering coefficient. This is followed with a detailed derivation of the large-scale structural properties of random graphs, including the position of the phase transition at which a giant component appears, the size of the giant component, the average size of the small components, and the expected diameter of the network. The chapter ends with a discussion of some of the shortcomings of the random graph model.

scholarly journals Water-promoted dehydrative coupling of 2-aminopyridines in heptane via a borrowing hydrogen strategy

RSC Advances ◽  
2021 ◽  
Vol 11 (37) ◽  
pp. 23144-23150
Author(s):  
Taku Nakayama ◽  
Hidemasa Hikawa ◽  
Shoko Kikkawa ◽  
Isao Azumaya
Keyword(s):  
Coupling Reaction ◽  
Direct Amination ◽  
Borrowing Hydrogen ◽  
Novel Strategy

We describe a novel strategy for the water-promoted dehydrative coupling reaction in heptane, which offers a sustainable direct amination of alcohols.

scholarly journals Tyrosinase Nanoparticles: Understanding the Melanogenesis Pathway by Isolating the Products of Tyrosinase Enzymatic Reaction

2021 ◽  
Vol 22 (2) ◽  
pp. 734
Author(s):  
Paul K. Varghese ◽  
Mones Abu-Asab ◽  
Emilios K. Dimitriadis ◽  
Monika B. Dolinska ◽  
George P. Morcos ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Large Scale ◽  
Magnetic Beads ◽  
Enzymatic Reaction ◽  
Oculocutaneous Albinism ◽  
Transmission Electron ◽  
Hill Kinetics ◽  
Rate Limiting ◽  
Human Tyrosinase

Human Tyrosinase (Tyr) is the rate-limiting enzyme of the melanogenesis pathway. Tyr catalyzes the oxidation of the substrate L-DOPA into dopachrome and melanin. Currently, the characterization of dopachrome-related products is difficult due to the absence of a simple way to partition dopachrome from protein fraction. Here, we immobilize catalytically pure recombinant human Tyr domain (residues 19–469) containing 6xHis tag to Ni-loaded magnetic beads (MB). Transmission electron microscopy revealed Tyr-MB were within limits of 168.2 ± 24.4 nm while the dark-brown melanin images showed single and polymerized melanin with a diameter of 121.4 ± 18.1 nm. Using Hill kinetics, we show that Tyr-MB has a catalytic activity similar to that of intact Tyr. The diphenol oxidase reactions of L-DOPA show an increase of dopachrome formation with the number of MB and with temperature. At 50 °C, Tyr-MB shows some residual catalytic activity suggesting that the immobilized Tyr has increased protein stability. In contrast, under 37 °C, the dopachrome product, which is isolated from Tyr-MB particles, shows that dopachrome has an orange-brown color that is different from the color of the mixture of L-DOPA, Tyr, and dopachrome. In the future, Tyr-MB could be used for large-scale productions of dopachrome and melanin-related products and finding a treatment for oculocutaneous albinism-inherited diseases.

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