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copper catalyst

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https://www.readbyqxmd.com/read/28921973/evans-showell-type-polyoxometalates-constructing-high-dimensional-inorganic-organic-hybrid-compounds-with-copper-organic-coordination-complexes-synthesis-and-oxidation-catalysis
#1
Haiyan An, Yujiao Hou, Lin Wang, Yumeng Zhang, Wei Yang, ShenZhen Chang
Four new hybrid architectures containing a [Co2Mo10H4O38](6-) polyoxoanion, (en)[Cu3(ptz)4(H2O)4][Co2Mo10H4O38]·24H2O (1), (Hbim)2[{Cu(bim)2(H2O)2}2{Co2Mo10H4O38}]·5H2O (2), H2[Cu(dpdo)3(H2O)4][{Cu2(dpdo)3(H2O)4(CH3CN)}2{Co2Mo10H4O38}2]·9H2O (3), and (H2bpp)4[{Cu(H2O)2}{NaCo2Mo10H4O38}2]·10H2O (4), where ptz = 5-(4-pyridyl)-1H-tetrazole, en = ethylenediamine, bim = benzimidazole, dpdo = 4,4'-bipyridine-N,N'-dioxide, and bpp = 1,3-bis(4-pyridyl)propane, have been prepared and characterized through elemental analysis, thermogravimetric analysis, IR spectroscopy, and powder and single-crystal X-ray diffraction...
September 18, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28921958/electronic-structural-analysis-of-copper-ii-tempo-abno-complexes-provides-evidence-for-copper-i-oxoammonium-character
#2
Richard C Walroth, Kelsey C Miles, James T Lukens, Samantha N MacMillan, Shannon S Stahl, Kyle M Lancaster
Copper/aminoxyl species are proposed as key intermediates in aerobic alcohol oxidation. Several possible electronic structural descriptions of these species are possible, and the present study probes this issue by examining four crystallographically characterized Cu/aminoxyl halide complexes by Cu K-edge, Cu L2,3-edge, and Cl K-edge X-ray absorption spectroscopy. The mixing coefficients between Cu, aminoxyl, and halide orbitals are determined via these techniques with support from density functional theory...
September 18, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28921692/mechanistic-studies-on-the-role-of-cuii-co3-n-2-2n-as-a-water-oxidation-catalyst-carbonate-as-a-non-innocent-ligand
#3
Amir Mizrahi, Dan Meyerstein, Israel Zilbermann, Haya Kornweitz, Eric Maimon, Haim Cohen
Recently it was reported that copper bicarbonate/ carbonate complexes are good electro-catalysts for water oxidation. However, the results did not enable a decision whether the active oxidant is a CuIII or a CuIV complex. Kinetic analysis of pulse radiolysis measurements coupled with DFT calculations point out that CuIII(CO3)n3-2n complexes are the active intermediates in the electrolysis of CuII(CO3)n2-2n solution. The results enable the evaluation of E°((CuIII/II(CO3)n)aq) ~ 1.42 V vs. NHE at pH 8.4. This redox potential is in accord with the electrochemical report...
September 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28920681/access-to-cyano-containing-isoxazolines-via-copper-catalyzed-domino-cyclization-cyanation-of-alkenyl-oximes
#4
Fei Meng, Honglin Zhang, Kang Guo, Jiayue Dong, Ai-Min Lu, Yingguang Zhu
A highly efficient copper-catalyzed cyclization/cyanation cascade of unactivated olefins bearing oximes is described. A variety of cyano-containing isoxazolines have been obtained in high yields with cheap Cu(NO3)2·3H2O as the catalyst and TMSCN as the non-metallic cyanide source. The present method provides a mild, simple, and practical access to cyano-substituted isoxazolines and is amenable to gram scale. The simultaneous construction of C(sp3)-CN and C-O bonds can be achieved in one step.
September 18, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28920121/room-temperature-cu-catalyzed-n-arylation-of-aliphatic-amines-in-neat-water
#5
Deping Wang, Yanwen Zheng, Min Yang, Fuxing Zhang, Fangfang Mao, Jiangxi Yu, Xiaohong Xia
A room-temperature and PTC-free copper-catalyzed N-arylation of aliphatic amines in neat water has been developed. Using a combination of CuI and 6,7-dihydroquinolin-8(5H)-one oxime as the catalyst and KOH as the base, a wide range of aliphatic amines are arylated with various aryl and heteroaryl halides to give the corresponding products in up to 95% yield.
September 18, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28918376/effect-of-precursors-on-the-structure-and-activity-of-cuo-coox-%C3%AE-al2o3-catalysts-for-no-reduction-by-co
#6
Lingling Zhang, Xiaojiang Yao, Yiyang Lu, Chuanzhi Sun, Changjin Tang, Fei Gao, Lin Dong
Catalytic reduction of NO by CO was studied over a series of CuO-CoOx/γ-Al2O3 catalysts prepared by co-impregnation with different copper and cobalt precursors (acetate and nitrate) to evaluate the structure-activity relationship. The obtained samples were characterized in detail by means of XRD, LRS, XPS, H2-TPR and in situ FT-IR technologies. Results indicate that copper oxide is agglomerated while cobalt oxide is dispersed on γ-Al2O3 for the catalyst prepared from copper acetate and cobalt acetate precursors (CuACoA); CuxCo3-xO4 spinel is formed and agglomerated on the catalyst prepared from copper nitrate and cobalt nitrate precursors (CuNCoN); while both copper oxide and cobalt oxide could be homogeneously dispersed for the catalyst prepared from copper nitrate and cobalt acetate precursors (CuNCoA), which exhibits the best activity for NO reduction by CO...
September 8, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28914299/a-dinuclear-copper-i-thiodiacetate-complex-as-an-efficient-and-reusable-click-catalyst-for-the-synthesis-of-glycoconjugates
#7
Neha Sareen, Anoop S Singh, Vinod K Tiwari, Rajni Kant, Subrato Bhattacharya
We report herein the facile synthesis and structural characterization of a highly stable dinuclear Cu(i) complex, [(PPh3)2Cu(μ-tda)Cu(PPh3)2]·6H2O 1 (tda = thiodiacetate anion), in which the Cu-Cu distance is 7.197 Å. This "pre-formed" complex serves as an extremely efficient and recyclable homogeneous catalyst (2 mol%, 30 min) for CuAAC in dichloromethane solvent. The synthesis of a variety of glycoconjugates under ambient conditions is successfully achieved using 1 as a catalyst. The products are obtained in high yields and very short reaction times while complying with the "click protocols"...
September 15, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28913532/stereodivergent-hydrodefluorination-of-gem-difluoroalkenes-selective-synthesis-of-z-and-e-monofluoroalkenes
#8
Ryoto Kojima, Koji Kubota, Hajime Ito
We have developed a novel approach for the stereodivergent hydrodefluorination of gem-difluoroalkenes using copper(i) catalysts to obtain stereodefined monofluoroalkenes. Both (Z)- and (E)-terminal monofluoroalkenes were obtained by the hydrodefluorination of gem-difluoroalkenes in the presence of copper(i) catalysts and diboron or hydrosilane, respectively, with high stereoselectivity. DFT calculations were conducted to elucidate the stereoselectivity.
September 15, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28913427/ultrastable-atomic-copper-nanosheets-for-selective-electrochemical-reduction-of-carbon-dioxide
#9
Lei Dai, Qing Qin, Pei Wang, Xiaojing Zhao, Chengyi Hu, Pengxin Liu, Ruixuan Qin, Mei Chen, Daohui Ou, Chaofa Xu, Shiguang Mo, Binghui Wu, Gang Fu, Peng Zhang, Nanfeng Zheng
The electrochemical conversion of CO2 and H2O into syngas using renewably generated electricity is an attractive approach to simultaneously achieve chemical fixation of CO2 and storage of renewable energy. Developing cost-effective catalysts for selective electroreduction of CO2 into CO is essential to the practical applications of the approach. We report a simple synthetic strategy for the preparation of ultrathin Cu/Ni(OH)2 nanosheets as an excellent cost-effective catalyst for the electrochemical conversion of CO2 and H2O into tunable syngas under low overpotentials...
September 2017: Science Advances
https://www.readbyqxmd.com/read/28902440/real-time-control-of-the-enantioselectivity-of-a-supramolecular-catalyst-allows-selecting-the-configuration-of-consecutively-formed-stereogenic-centres
#10
Jeremy M Zimbron, Xavier Caumes, Yan Li, Christophe M Thomas, Matthieu Raynal, Laurent Bouteiller
The enantiomeric state of a supramolecular copper catalyst can be switched in situ in ca. five seconds. The dynamic property of the catalyst is provided by the non-covalent nature of the helical assemblies supporting the copper centres. These assemblies are formed by mixing an achiral benzene-1,3,5-tricarboxamide (BTA) phosphine ligand (for copper coordination) and both enantiomers of a chiral phosphine-free BTA co-monomer (for chirality amplification). The enantioselectivity of the hydrosilylation reaction is fixed by the BTA enantiomer in excess, which can be altered by simple BTA addition...
September 13, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28899086/copper-catalyzed-enantioselective-hydroboration-of-unactivated-1-1-disubstituted-alkenes
#11
Won Jun Jang, Seung Min Song, Jong Hun Moon, Jin Yong Lee, Jaesook Yun
We report an efficient and highly enantioselective hydroboration of aliphatic 1,1-disubstituted alkenes with pinacolborane using a phosphine-Cu catalyst. The method allows facile preparation of enantiomerically enriched β-chiral alkyl pinacolboronates from a range of 1,1-disubstituted alkenes with high enantioselectivity up to 99% ee. Unprecedented enantiodiscrimination between the geminal alkyl substituents was observed with functional group compatibility in the hydroboration. Furthermore, a catalyst loading as low as 1 mol % furnished the desired product without a decrease in yield or selectivity, demonstrating its efficiency in gram scale synthesis...
September 18, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28898954/degradation-of-2-4-6-trichlorophenol-with-peroxymonosulfate-catalyzed-by-soluble-and-supported-iron-porphyrins
#12
Tuğçe Günay, Yasemin Çimen
Degradation of 2,4,6-trichloropenol (TCP) with peroxymonosulfate (PMS) catalyzed by iron porphyrin tetrasulfonate ([FePTS)] was investigated in an 8-to-1 (v/v) CH3OH-H2O mixture. Typical reaction medium contained a 4.00 mL methanol solution of TCP (0.100 mmol), a 0.50 mL aqueous solution of catalyst (5.0 × 10(-4) mmol), and 0.100 mmol PMS (as 0.031 g of Oxone). The reaction was performed at ambient temperature. The conversion of TCP was 74% in 30 min and 80% in 6 h when the catalyst was [FePTS]. Amberlite IRA-900 supported [FePTS] catalyst was also prepared...
September 8, 2017: Environmental Pollution
https://www.readbyqxmd.com/read/28891636/cuaac-based-click-chemistry-in-self-healing-polymers
#13
Diana Döhler, Philipp Michael, Wolfgang H Binder
Click chemistry has emerged as a significant tool for materials science, organic chemistry, and bioscience. Based on the initial concept of Barry Sharpless in 2001, the copper(I)-catalyzed azide/alkyne cycloaddition (CuAAC) reaction has triggered a plethora of chemical concepts for linking molecules and building blocks under ambient conditions, forming the basis for applications in autonomous cross-linking materials. Self-healing systems on the other hand are often based on mild cross-linking chemistries that are able to react either autonomously or upon an external trigger...
September 11, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28887563/the-most-active-cu-facet-for-low-temperature-water-gas-shift-reaction
#14
Zhenhua Zhang, Sha-Sha Wang, Rui Song, Tian Cao, Liangfeng Luo, Xuanye Chen, Yuxian Gao, Jiqing Lu, Wei-Xue Li, Weixin Huang
Identification of the active site is important in developing rational design strategies for solid catalysts but is seriously blocked by their structural complexity. Here, we use uniform Cu nanocrystals synthesized by a morphology-preserved reduction of corresponding uniform Cu2O nanocrystals in order to identify the most active Cu facet for low-temperature water gas shift (WGS) reaction. Cu cubes enclosed with {100} facets are very active in catalyzing the WGS reaction up to 548 K while Cu octahedra enclosed with {111} facets are inactive...
September 8, 2017: Nature Communications
https://www.readbyqxmd.com/read/28881436/rational-design-of-sulfur-doped-copper-catalysts-for-the-selective-electroreduction-of-carbon-dioxide-to-formate
#15
Yun Huang, Yilin Deng, Albertus Denny Handoko, Gregory K L Goh, Boon Siang Yeo
The selective electroreduction of CO2 to formate (or formic acid) is currently of great interest in the field of renewable energy utilization. In this work, we designed a sulfur-doped Cu2O-derived Cu catalyst, and showed that the presence of sulfur could significantly tune the selectivity of Cu from producing a myriad of CO2 reduction products to almost exclusively formate. Sulfur is doped into the Cu catalysts by dipping the Cu substrates into ammonium polysulfide solutions. Catalyst films with the highest sulfur content of 2...
September 7, 2017: ChemSusChem
https://www.readbyqxmd.com/read/28879000/an-investigation-into-the-unusual-linkage-isomerization-and-nitrite-reduction-activity-of-a-novel-tris-2-pyridyl-copper-complex
#16
Isolda Roger, Claire Wilson, Hans M Senn, Stephen Sproules, Mark D Symes
The copper-containing nitrite reductases (CuNIRs) are a class of enzymes that mediate the reduction of nitrite to nitric oxide in biological systems. Metal-ligand complexes that reproduce the salient features of the active site of CuNIRs are therefore of fundamental interest, both for elucidating the possible mode of action of the enzymes and for developing biomimetic catalysts for nitrite reduction. Herein, we describe the synthesis and characterization of a new tris(2-pyridyl) copper complex ([Cu1(NO2)2]) that binds two molecules of nitrite, and displays all three of the common binding modes for [Formula: see text], with one nitrite bound in an asymmetric quasi-bidentate κ(2)-ONO manner and the other bound in a monodentate fashion with a linkage isomerism between the κ(1)-ONO and κ(1)-NO2 binding modes...
August 2017: Royal Society Open Science
https://www.readbyqxmd.com/read/28873243/circumventing-metallic-intrinsic-reactivity-radical-generation-with-redox-active-ligands
#17
Jérémy Jacquet, Khaled Cheaib, Yufeng Ren, Hervé Vezin, Maylis Orio, Sébastien Blanchard, Louis Fensterbank, Marine Desage-El Murr
Nickel complexes have gained sustained attention as efficient catalysts in cross-coupling reactions and co-catalysts in dual systems due to their ability to react with radical species. Central to this reactivity is nickel's propensity to shuttle through several accessible redox states from Ni0 to NiIV. Here, we report the catalytic generation of trifluoromethyl radicals from a nickel complex bearing redox-active iminosemiquinone ligands. This unprecedented reactivity is enabled through ligand-based oxidation performing electron transfer to an electrophilic CF3+ source while the nickel oxidation state is preserved...
September 5, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28871167/supported-cu-0-nanoparticles-catalyst-for-controlled-radical-polymerization-reaction-and-block-copolymer-synthesis
#18
Aurel Diacon, Edina Rusen, Alexandra Mocanu, Leona Cristina Nistor
The synthesis of Cu(0) nanoparticles on different supports and their activity in controlled living radical polymerization processes is presented. The type of support influences the final size of the copper nanoparticles as well as their adhesion to the support. These aspects have a direct influence on the characteristics of the polymers obtained. The best results were obtained for SiO2 particles, which afforded a good molecular weight distribution (Mw/Mn = 1.25). The activity, recovery and recycling of the catalyst was explored for ultrafast polymerization reaction of butyl acrylate...
September 4, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28868648/evident-improvement-of-electrochemical-water-oxidation-by-fine-tuning-the-structure-of-tetradentate-n4-ligands-of-molecular-copper-catalysts
#19
Junyu Shen, Mei Wang, Jinsuo Gao, Hongxian Han, Hong Liu, Licheng Sun
Two copper complexes, [L1Cu(OH2)](BF4)2 [1, L1 = N,N'-dimethyl-N,N'-bis(pyridin-2-ylmethyl)-1,2-diaminoethane] and [L2Cu(OH2)](BF4)2 [2, L2 = 2,7-bis(2-pyridyl)-3,6-diaza-2,6-octadiene], were prepared as molecular water oxidation catalysts. Complex 1 displayed an overpotential (η) of 1.07 V at 1 mA cm-2 and an observed rate constant (kobs) of 13.5 s-1 at η 1.0 V in pH 9.0 phosphate buffer solution, while 2 exhibited a significantly smaller η (0.70 V) to reach 1 mA cm-2 and a higher kobs (50.4 s-1) than 1 under identical test conditions...
September 3, 2017: ChemSusChem
https://www.readbyqxmd.com/read/28867707/development-of-batch-and-flow-immobilized-catalytic-systems-with-high-catalytic-activity-and-reusability
#20
Yoichi M A Yamada
My mission in catalysis research is to develop highly active and reusable supported catalytic systems in terms of fundamental chemistry and industrial application. For this purpose, I developed three types of highly active and reusable supported catalytic systems. The first type involves polymeric base-supported metal catalysts: Novel polymeric imidazole-Pd and Cu complexes were developed that worked at the mol ppm level for a variety of organic transformations. The second involves catalytic membrane-installed microflow reactors: Membranous polymeric palladium and copper complex/nanoparticle catalysts were installed at the center of a microtube to produce novel catalytic membrane-immobilized flow microreactor devices...
2017: Chemical & Pharmaceutical Bulletin
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