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copper catalyst

Peter Warneck
The dependences on ionic strength of the hydrolysis constants of Fe3+ and of the first dissociation constant of sulfurous acid are briefly reviewed. The data are needed to derive from apparent stability constants reported in the literature the stability constants for the three iron-sulfito complexes defined by the equilibria (c1) FeOH2+ + HSO3- = FeSO3+ + H2O, (c2) FeSO3+ + HSO3- = Fe(SO3)2- + H+, (c3a) Fe(SO3)2- + HSO3- = Fe(SO3)3H2-, where Kc1 = 1982 ± 518 dm3 mol-1, Kc2 = 0.72 ± 0.08, Kc3a = 189 ± 9 dm3 mol-1 (ionic strength μ = 0...
January 19, 2018: Physical Chemistry Chemical Physics: PCCP
Kim Degn Jensen, Jakub Tymoczko, Jan Rossmeisl, Aliaksandr Bandarenka, Ib Chorkendorff, Maria Escudero-Escribano, Ifan Erfyl Lester Stephens
Herein we experimentally explore the relationship between the binding of the reaction intermediates and oxygen reduction activity in alkaline media. By introducing Cu into the 2nd surface layer of a Pt(111) single crystal, we tune the surface reactivity. We demonstrate that in both NaOH and KOH, the optimal catalyst should exhibit OH binding ~0.1 eV weaker than Pt(111), via a Sabatier volcano; this observation suggests that the reaction is mediated via the same surface bound intermediates as in acid, in contrast to previous reports...
January 18, 2018: Angewandte Chemie
Matthias Meier, Zdeněk Jakub, Jan Balajka, Jan Hulva, Roland Bliem, Pardeep K Thakur, Tien-Lin Lee, Cesare Franchini, Michael Schmid, Ulrike Diebold, Francesco Allegretti, David A Duncan, Gareth S Parkinson
Accurately modelling the structure of a catalyst is a fundamental prerequisite for correctly predicting reaction pathways, but a lack of clear experimental benchmarks makes it difficult to determine the optimal theoretical approach. Here, we utilize the normal incidence X-ray standing wave (NIXSW) technique to precisely determine the three dimensional geometry of Ag1 and Cu1 adatoms on Fe3O4(001). Both adatoms occupy bulk-continuation cation sites, but with a markedly different height above the surface (0.43 ± 0...
January 15, 2018: Nanoscale
Cheng Chi, Baohong Sun, Ninglin Zhou, Ming Zhang, Xiaohong Chu, Ping Yuan, Jian Shen
A novel catalyst system of Reverse Atom Transfer Radical Polymerization (RATRP) to prepare Polyurethane (PU) films modified by poly(2-methacryloyloxyethyl phosphorylcholine) (pMPC) was studied in this article. In this system, PU film was pretreated by LaCl3/CA ethanol solution to obtain a hydrated surface allowing more initiators to be immobilized on it. Moreover, complexes composed of silane coupling agent 3-chloropropyltrimethoxysilane (CPTM), chlorhexidine acetate (CA) and lanthanum(III) worked as ligands of copper ions as a whole during RATRP process...
January 8, 2018: Colloids and Surfaces. B, Biointerfaces
Navid Zanganeh, Vamshi Krishna Guda, Hossein Toghiani, Jason M Keith
A novel gold-copper based silica encapsulated mixed metal oxide (MMO) core-shell catalyst - with sub 5-nm MMO particles - was successfully synthesized via a reverse micelle process. The SiO2 encapsulated MMO catalyst was reduced under hydrogen flow to produce Au-Cu@SiO2 catalyst. XRD and XPS characterization confirmed the presence of Au-Cu nanocomposites in the catalyst while TEM characterization revealed the core-shell structure of the catalyst with the presence of sub 5-nm Au-Cu nanoparticle cores inside SiO2 shells...
January 12, 2018: ACS Applied Materials & Interfaces
Di-Chang Zhong, Wen-Ju Liu, Hai-Hua Huang, Ting Ouyang, Long Jiang, Wen Zhang, Tong-Bu Lu
A catalyst developed from a Cu(II) complex of (Et4N)[Cu(pyN2Me2)(HCO2)]∙0.5CH3OH∙H2O (1∙0.5CH3OH∙H2O; pyN2Me2 = bis(2,6-dimethylphenyl)-2,6-pyridinedicarboxamidate(2-)) shows a high activity to catalyze the reduction reaction of CO2 to CO driven by visible light in 4:1 acetonitrile/water (v:v) using [Ru(phen)3](PF6)2 as photosensitizer and TEOA as sacrificial reductant, with a high TON of 9900 and a high selectivity of 98%. The results of isotope labeling experiment, durable test and energy dispersive spectroscopy reveal that 1 is robust during the photocatalytic process...
January 11, 2018: Chemistry: a European Journal
Rambabu Dakarapu, John R Falck
Cross-coupling reactions are a staple in organic synthesis, especially for C-C bond formation with sp- and sp2-carbon electrophiles. In recent years, the range of accessible C-C bonds has been extended to stereogenic centers which expedites access to greater molecular complexity. However, these reactions predominantly depend upon late transition metal (LTM) catalysts whose cost, toxicity, and/or environmental impact have come under increasing scrutiny and governmental regulation. Here, we report Mn(II)Cl2 complexes alone, or with assistance from copper, catalyze the stereospecific cross-coupling of α-alkoxyalkylstannanes with organic electrophiles with complete retention of configuration...
January 10, 2018: Journal of Organic Chemistry
Thomas G Ribelli, Marco Fantin, Jean-Claude Daran, Kyle F Augustine, Rinaldo Poli, Krzysztof Matyjaszewski
The synthesis and characterization of tris[(4-dimethylaminopyridyl)methyl]amine (TPMANMe2) as a ligand for copper catalyzed atom transfer radical polymerization (ATRP) is reported. In solution, the [CuI(TPMANMe2)Br] complex shows fluxionality by variable temperature NMR, indicating rapid ligand exchange. In the solid-state, the [CuII(TPMANMe2)Br][Br] complex exhibits a slightly distorted trigonal bipyramidal geometry (τ = 0.89). The UV-Vis spectrum of [CuII(TPMANMe2)Br]+ salts is similar to those of other pyridine-based ATRP catalysts...
January 10, 2018: Journal of the American Chemical Society
Bing-Bing Lu, Jin Yang, Guang-Bo Che, Wen-Yuan Pei, Jian-Fang Ma
A new highly stable copper(I)-based metal-organic framework (MOF), namely, [CuI4(SiW12O40)(L)]·6H2O·2DMF (1), was synthesized by incorporating Keggin-type polyoxometalate (POM) anions and a functionalized wheel-like resorcin[4]arene-based ligand (L) under sovothermal condition. 1 exhibits a charming 3D supramolecular architecture sandwiched by the POM anions. Noticeably, 1 has exceptional chemical stability, especially in organic solvents or aqueous solutions with a wide range of pH values. Considering the catalytically active Cu(I) sites in 1, the azide-alkyne cycloaddition (AAC) reaction was studied by employing 1 as the heterogeneous catalyst...
January 10, 2018: ACS Applied Materials & Interfaces
Xingyu Jiang, Philip Boehm, John F Hartwig
We report stereodivergent allylic substitution reactions of allylic esters with prochiral enolates derived from azaaryl acetamides and acetates to form products from addition of the enolates at the most substituted carbon of an allyl moiety with two catalysts, a chiral metallacyclic iridium complex and a chiral bisphosphine-ligated copper(I) complex, which indi-vidually control the configuration of the electrophilic and nucleophilic carbon atoms, respectively. By simple permuta-tions of enantiomers of the two catalysts, all four stereoiso-mers of products containing two stereogenic centers were syn-thesized individually with high diastereoselectivity and enan-tioselectivity...
January 10, 2018: Journal of the American Chemical Society
Huanhuan Yang, Yanyan Chen, Xiaojing Cui, Guofu Wang, Youliang Cen, Tiansheng Deng, Wenjun Yan, Jie Gao, Shanhui Zhu, Unni Olsbye, Jianguo Wang, Weibin Fan
Identification of active copper species, and further illustration of catalytic mechanism of Cu-based catalysts is still a challenge because of the mobility and evolution of Cu0 and Cu+ species in the reaction process. Thus, an unprecedentedly stable Cu-based catalyst was fabricated by uniformly embedding Cu nanoparticles in mesoporous silica shell for clarifying the catalytic roles of Cu0 and Cu+ with dehydrogenation of methanol to methyl formate by combining isotope-labeling experiment, in situ spectroscopy and DFT calculations...
January 4, 2018: Angewandte Chemie
Johannes G Rebelein, Thomas R Ward
Bioorthogonal chemistry largely relies on the use of abiotic metals to catalyze new-to-nature reactions in living systems. Over the past decade, metal complexes and metal-encapsulated systems such as nanoparticles have been developed to unravel the reactivity of transition metals, including ruthenium, palladium, iridium, copper, iron, and gold in biological systems. Thanks to these remarkable achievements, abiotic catalysts are able to fluorescently label cells, uncage or form cytotoxic drugs and activate enzymes in cellulo/vivo...
January 4, 2018: Current Opinion in Biotechnology
Wenjin Zhu, Lei Zhang, Piaoping Yang, Xiaoxia Chang, Hao Dong, Ang Li, Congling Hu, Zhiqi Huang, Zhi-Jian Zhao, Jinlong Gong
Electrochemical conversion of carbon dioxide (electrochemical reduction of carbon dioxide) to value-added products is a promising way to solve CO2 emission problems. This paper describes a facile one-pot approach to synthesize palladium-copper (Pd-Cu) bimetallic catalysts with different structures. Highly efficient performance and tunable product distributions are achieved due to a coordinative function of both enriched low-coordinated sites and composition effects. The concave rhombic dodecahedral Cu3 Pd (CRD-Cu3 Pd) decreases the onset potential for methane (CH4 ) by 200 mV and shows a sevenfold CH4 current density at -1...
December 27, 2017: Small
Xuan Zhang, Nicolaas A Vermeulen, Zhiyuan Huang, Yuexing Cui, Jian Liu, Matthew D Krzyaniak, Zhanyong Li, Hyunho Noh, Michael R Wasielewski, Massimiliano Delferro, Omar K Farha
Two new UiO-68 type of Zr-MOFs featuring redox non-innocent catechol-based linkers of different redox activities have been synthesized through a de novo mixed-linker strategy. Metalation of the MOFs with Cu(II) precursors triggers the reduction of Cu(II) by the phenyl-catechol groups to Cu(I) with the concomitant formation of semiquinone radicals as evidenced by EPR and XPS characterization. The MOF-supported catalysts are selective toward the allylic oxidation of cyclohexene and it is found that the presence of in situ-generated Cu(I) species exhibits enhanced catalytic activity as compared to a similar MOF with Cu(II) metalated naphthalenyl-dihydroxy groups...
December 26, 2017: ACS Applied Materials & Interfaces
Inayat Ullah, Khakemin Khan, Muhammad Sohail, Kifayat Ullah, Anwar Ullah, Shabnum Shaheen
In this research work, copper (Cu), palladium (Pd) and their bimetallic palladium@ copper (Pd@Cu) nanoparticles were synthesized using trisodium citrate as a stabilizing agent using the known chemical reduction method. The synthesized Cu, Pd and Pd@Cu nanoparticles were characterized by the ultraviolet-visible spectroscopy, scanning electron microscopy and X-ray diffraction spectroscopy, respectively. The different volumes of trisodium citrate were used for the stability of synthesized monometallic Cu, Pd and bimetallic Pd@Cu nanoparticles...
2017: International Journal of Nanomedicine
Yen-Yie Lau, Yee-Shian Wong, Tze-Zhang Ang, Soon-An Ong, Nabilah Aminah Lutpi, Li-Ngee Ho
The theme of present research demonstrates performance of copper (II) sulfate (CuSO4) as catalyst in thermolysis process to treat reactive black 5 (RB 5) dye. During thermolysis without presence of catalyst, heat was converted to thermal energy to break the enthalpy of chemical structure bonding and only 31.62% of color removal. With CuSO4 support as auxiliary agent, the thermally cleaved molecular structure was further destabilized and reacted with CuSO4. Copper ions functioned to delocalize the coordination of π of the lone paired electron in azo bond, C=C bond of the sp2 carbon to form C-C of the sp3 amorphous carbon in benzene and naphthalene...
December 23, 2017: Environmental Science and Pollution Research International
Giovanni La Penna, Li Mai Suan
Transition metal ions often interact with disordered proteins. The affinity is high enough to compete with structured proteins, but the catalytic activity of the metal center is often out of control and, therefore, potentially dangerous for cells. An example is a single copper ion interacting with the amyloid-beta (Abeta) peptide and triplet dioxygen, an interaction that is fundamental in producing reactive oxygen species in neurodegeneration. In this work, we apply a high-throughput modelling of the Cu-Abeta-O2 system, with the aim at providing a tool to dissect the structural features that characterize dangerous Cu-based catalysts in neurodegeneration...
December 18, 2017: Chemistry: a European Journal
Xiang Ren, Xuqiang Ji, Yicheng Wei, Dan Wu, Yong Zhang, Min Ma, Zhiang Liu, Abdullah M Asiri, Qin Wei, Xuping Sun
It is highly desired to develop efficient earth-abundant electrocatalysts for the oxygen evolution reaction (OER) in alkaline media. In this communication, we report the in situ electrochemical conversion of a nanoarray of Cu(tetracyanoquinodimethane), Cu(TCNQ), an inorganic-organic hybrid, on Cu foam into CuO nanocrystals confined in a highly conductive nanoarray via anode oxidation. As a 3D catalyst electrode, the resulting CuO-TCNQ/CF shows high OER activity and demands an overpotential of only 317 mV to drive a geometrical catalytic current density of 25 mA cm-2...
December 18, 2017: Chemical Communications: Chem Comm
Lindsay E Chatkewitz, John F Halonski, Marshall S Padilla, Douglas D Young
The prevalence of 1,3-dipolar cycloadditions of azides and alkynes within both biology and chemistry highlights the utility of these reactions. However, the use of a copper catalyst can be prohibitive to some applications. Consequently, we have optimized a copper-free microwave-assisted reaction to alleviate the necessity for the copper catalyst. A small array of triazoles was prepared to examine the scope of this approach, and the methodology was translated to a protein context through the use of unnatural amino acids to demonstrate one of the first microwave-mediated bioconjugations involving a full length protein...
December 6, 2017: Bioorganic & Medicinal Chemistry Letters
Hongli Jia, Qi Li, Aruuhan Bayaguud, Yichao Huang, Shan She, Kun Chen, Yongge Wei
In this work, we confirmed that the copper-catalysed azide-alkyne cycloaddition (CuAAC) reaction is an effective method for the organic-functionalization of polyoxometalates (POMs). Herein, for the first time, four novel 1,2,3-triazole functionalized polyoxovanadate (POV) organic-inorganic hybrids, (Bu4N)2[V6O13{(OCH2)3C5H6N3O}2]·1.5CH3CN 2, (Bu4N)2[V6O13{(OCH2)3C7H8N3O2}2]·2CH3CN 3, (Bu4N)2[V6O13{(OCH2)3C11H10N3}2] 4 and (Bu4N)2[V6O13{(OCH2)3C10H7N3Cl}2] 5 were prepared through the CuAAC reaction using the azide functionalized hexavanadate, (Bu4N)2[V6O13{(OCH2)3CCH2N3}2]·2...
December 14, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
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