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Chemistry: a European Journal

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https://www.readbyqxmd.com/read/27933684/enhancement-of-ag-based-plasmonic-photocatalysis-in-the-hydrogen-production-from-ammonia-borane-by-the-assist-of-single-site-ti-oxide-moiety-within-the-silica-framework
#1
Priyanka Verma, Yasutaka Kuwahara, Kohsuke Mori, Hiromi Yamashita
Ag nanoparticles (NPs) have gained great attention owing to their interesting plasmonic properties showing efficient catalysis under visible light irradiation. In this study, Ag-based plasmonic catalyst supported on the mesoporous silica involving isolated and tetrahedrally coordinated single-site Ti-oxide moieties, Ag/Ti-SBA-15, has been designed with the purpose of utilizing the broad spectrum range of solar energy. The Ti-SBA-15 support allows the deposition of small Ag NPs with a narrow size distribution...
December 9, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27933670/gold-i-fluorohalides-theory-and-experiment
#2
Babil Menjón, Miguel Baya, Alberto Pérez-Bitrián, Sonia Martínez-Salvador, José María Casas, Jesús Orduna
The anionic trifluoromethyl-gold(I) derivatives [CF₃AuX]⁻, which have been prepared and isolated as their [PPh₄]⁺ salts in good yield, undergo thermally-induced difluorocarbene extrusion in the gas phase giving rise to the mixed gold(I) fluorohalide complexes [F-Au-X]⁻ (X = Cl, Br, I). These triatomic species have been detected by tandem mass spectrometry (MS2) experiments and their properties have been analyzed by DFT methods. The CF₂ extrusion mechanism from the Au-CF₃ moiety serves as a model for the CF₂ insertion into the Au-F bond, since both reactivity channels are connected by the microreversibility principle...
December 9, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27933682/high-efficient-intramolecular-electrochemiluminescence-energy-transfer-for-ultrasensitive-bioanalysis-of-aflatoxin-m1
#3
Jiali Liu, Min Zhao, Ying Zhuo, Yaqin Chai, Ruo Yuan
The intermolecular electrochemiluminescence resonance energy transfer (ECL-RET) between luminol and Ru(bpy)32+ was studied extensively to achieve the sensitive bio-analysis owing to the perfect spectral overlap of the donor and acceptor, but it still suffers from the challenging issue of low energy transfer efficiency. Here, the intramolecular ECL-RET towards the novel ECL compound containing the donor of luminol and the acceptor of Ru(bpy)2(mcbpy)2+ was designed and investigated for the first time (The compound was abbreviated as Lum-Ru)...
December 8, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27933675/c3-symmetric-boron-lewis-acid-with-a-cage-shape-for-chiral-molecular-recognition-and-asymmetric-catalysis
#4
Akihito Konishi, Koichi Nakaoka, Hikaru Maruyama, Hideto Nakajima, Tomohiro Eguchi, Akio Baba, Makoto Yasuda
Chiral Lewis acids have played an important role in the precise construction of various types of chiral molecules. Here, we designed and synthesized a cage-shaped borate 2 as a chiral Lewis acid, which possesses a unique C3-symmetric structure composed of three homochiral binaphthyl moieties. The highly symmetrical structure of 2 with homochirality was clearly elucidated by X-ray crystallographic analysis. The peculiar chiral environment of 2·THF exhibited the chiral recognition of some simple amines and a sulfoxide...
December 8, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27930832/borinic-acid-catalysed-hydrosilanes-reduction-of-tertiary-amides-a-mild-and-chemoselective-synthesis-of-amines
#5
Aurélien Chardon, Tharwat Mohy El Dine, Rémi Legay, Michael De Paolis, Jacques Rouden, Jérôme Blanchet
A reduction of various aryl, alkyl and α,β-unsaturated amides with phenylsilane catalysed by a borinic acid is reported. The reaction carried out under unprecedented very mild conditions and led to useful amines. Furthermore, the reaction tolerates a variety of functional groups. Initial investigation of the reaction mechanism was shown to involve an intermediate diarylhydroborane.
December 8, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27925698/frustrated-lewis-pairs-like-reactivity-of-rare-earth-metal-complexes-1-4-addition-reactions-and-polymerizations-of-conjugated-polar-alkenes
#6
Pengfei Xu, Yingming Yao, Xin Xu
Three rare-earth aryloxide ion pairs ([L1REOAr]+[B(C6F5)4]-; L1 = CH3C(2,6-iPr2C6H3N)CHC(CH3)(NCH2CH2PPh2); RE = Sc, Y, Lu; Ar = 2,6-tBu2C6H3) are reported, which feature RE/P combinations exhibiting frustrated Lewis pair (FLP)-like 1,4-addition reactions towards conjugated carbonyl substrates e.g. enone, ynone and acrylic substrates. Furthermore, these RE/P complexes are found to be effective catalysts for polymerizations of conjugated polar alkene monomers. Mechanistic studies reveal that the polymerizations are initiated by novel FLP-type 1,4-additions, rather than traditional and ubiquitous covalent RE-E (E = H, C, N, etc...
December 7, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27925694/a-photoresponsive-orthogonal-supramolecular-complex-based-on-host-guest-interactions
#7
Dongsheng Wang, Manfred Wagner, Andrew Saydjari, Julius Mueller, Svenja Winzen, Hans-Jürgen Butt, Si Wu
We synthesized a novel green-light-responsive tetra-ortho-isopropoxy-substituted azobenzene (ipAzo). Cis ipAzo forms a strong host-guest complex with γ-cyclodextrin (γ-CD) while trans ipAzo binds weakly. This new photoresponsive host-guest interaction is reverse to the well-known azobenzene (Azo)/α-cyclodextrin (α-CD) complex, which is strong only between trans Azo and α-CD. By combining the UV-light-responsive Azo/α-CD and green-light-responsive ipAzo/γ-CD host-guest complexes, a photoresponsive orthogonal supramolecular system is developed...
December 7, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27925327/crystal-structure-of-a-metalled-double-helix-generated-by-infinite-and-consecutive-c-agi-c-c-n1-hexylcytosine-base-pairs-through-argentophilic-and-hydrogen-bond-interactions
#8
Angel Terron, Blas Moreno-Vachiano, Antonio Bauza, Angel Garcia-Raso, Juan J Fiol, Miquel Barcelo-Oliver, Elies Molins, Antonio Frontera
The synthesis of a metalled double-helix containing exclusively silver-mediated C*-C* base pairs is reported herein (C* = N1hexylcytosine). Remarkably, it is the first crystal structure containing infinite and consecutive C*-AgI-C* base pairs that form a double helix. The AgI ion occupies the center between two C* residues with N(3)-Ag bond distances of 2.1 Å and short AgI-AgI distances (3.1 Å) suggesting an interesting argentophilic attraction as a stabilization source of the helical disposition. The solid state structure is further stabilized by metal-mediated base-pairs, hydrogen bonding and π-stacking interactions...
December 7, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27925324/the-delicate-balance-of-preorganisation-and-adaptability-in-multiply-bonded-host-guest-complexes
#9
Larissa K S von Krbek, Andreas J Achazi, Stefan Schoder, Marius Gaedke, Tobias Biberger, Beate Paulus, Christoph A Schalley
Rigidity and preorganisation are believed to be required for high affinity in multiply bonded supramolecular complexes as they help reducing the entropic penalty of the binding event. This comes at the price that such rigid complexes are sensitive to small geometric mismatches. In marked contrast, nature uses more flexible building blocks. Thus, one might consider putting the rigidity-high affinity notion to the test. Multivalent crown/ammonium complexes are ideal for this purpose as the monovalent interaction is well understood...
December 7, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27925323/synthesis-binding-properties-and-differences-on-cell-uptake-of-g-quadruplex-ligands-based-on-carbohydrate-naphthalene-diimide-conjugates
#10
Matilde Arevalo, Filippo Doria, Efres Belmonte-Reche, Aurore De Rache, Jenny Campos-Salinas, Ricardo Lucas, Eva Falomir, Miguel Carda, Jose María Pérez-Victoria, Jean-Louis Mergny, Mauro Freccero, Juan Carlos Morales
G-quadruplex (G4) are currently being explored as therapeutic targets in cancer and other pathologies. We have synthesized six carbohydrate naphthalene diimide conjugates (carb-NDIs) as G4 ligands to investigate their potential selectivity on G4 binding and on cell penetration. Carb-NDIs have shown certain selectivity for G4 structures against DNA duplexes but the different sugar moieties did not induce a preference for a specific G4 topology. Interestingly, when monosaccharides were attached through a short ethylene linker to the NDI scaffold their cellular uptake was 2-3 fold more efficient than when the sugar was directly attached through its anomeric position...
December 7, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27925321/chiral-primary-amine-catalyzed-asymmetric-%C3%AE-benzylation-with-in-situ-generated-ortho-quinone-methides
#11
Sanzhong Luo, Yunbo Zhu, Wenzhao Zhang, Long Zhang
A dual activation strategy integrating primary amine catalysis and Lewis base activation has been developed for asymmetric α-benzylation reaction. Enamine derived from β-ketocarbonyls could react effectively with in situ-generated ortho-QM under Lewis base activation in asymmetric α-benzylation of β-ketocarbonyls and α-branched aldehydes. The approach enables the creation of acyclic all-carbon quaternary stereocenters with excellent enantioselectivities and good activity.
December 7, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27925320/three-dimensional-fibrous-network-of-na0-21mno2-for-aqueous-sodium-ion-hybrid-supercapacitor
#12
Natarajan Karikalan, Chelladurai Karuppiah, Shen-Ming Chen, Murugan Velmurugan, Periyasami Gnanaprakasam
Sodium ion hybrid supercapacitors are the potential energy storage devices and recently received an enormous interest. However, the development of desired cathode material and the use of non-aqueous electrolyte remains a great challenge. Hence, we developed the aqueous Na-ion hybrid supercapacitor based on three dimensional fibrous network of NaMnO2. The described cathode material was synthesized by the electro-oxidation of potassium manganese hexacyanoferrate (KMnHCF) nanocubes. The oxidized compound was confirmed as Na0...
December 7, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27925318/total-synthesis-of-the-mycobacterium-tuberculosis-dideoxymycobactin-838-and-stereoisomers-diverse-cd1a-restricted-t-cells-display-a-common-hierarchy-of-lipopeptide-recognition
#13
Janice Cheng, Ligong Liu, Daniel Pellicci, Scott Jj Reddiex, Rachel Cotton, Tan-Yun Cheng, David Young, Ildiko Van Rhijn, Branch Moody, Jamie Rossjohn, David Fairlie, Dale Godfrey, Spencer John Williams
Mycobacterium tuberculosis produces dideoxymycobactin-838 (DDM-838), a lipopeptide that potently activates T cells upon binding to the MHC-like antigen-presenting molecule CD1a. M. tuberculosis produces DDM-838 in only trace amounts and a previous solid-phase synthesis provided sub-milligram quantities. We describe a high yielding solution-phase synthesis of DDM-838 that features a Mitsunobu substitution that avoids yield-limiting epimerization at lysine during esterification, and amidation conditions that prevent double-bond isomerization of the Z-C20:1 acyl chain, and provides material with equivalent antigenicity to natural DDM-838...
December 7, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27925316/functional-species-encapsulated-in-nitrogen-doped-porous-carbon-as-a-highly-efficient-catalyst-to-oxygen-reduction-reaction
#14
Li Song, Tao Wang, Yiou Ma, Hairong Xue, Hu Guo, Xiaoli Fan, Wei Xia, Hao Gong, Jianping He
The scarcity, high cost and poor stability of precious metal-based electrocatalysts have stimulated the development of novel non-precious metal catalysts to oxygen reduction reaction (ORR) for the use in fuel cells and metal-air batteries. Here, we in-situ fabricated a hybrid material (Co-W-C/N) with functional species (tungsten carbide and cobalt nanoparticles) encapsulated in N-doped porous carbon framework, through a facile multi-constituents co-assembly method combined with subsequent annealing treatment...
December 7, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27925314/a-simple-approach-to-develop-tailored-mesoporosity-in-nanostructured-heteropolysalts
#15
Juan Alcaniz-Monge
In this work, we describe a very simple approach to develop tailored mesoporosity in any nanostructured heteropolysalt with control over both the mesoporous volume and the pore size. This approach consisting in a treatment of the solid microporous precursor with a basic agent has been tested on the ammonium salt of the Keggin-type [PMo12O40]3- heteropolyanion, and constitutes a novel procedure for the preparation of mesoporous solids with no precedents in the literature. The results obtained in this study allows for extracting two main conclusions: (i) The micro- and mesoporosity structures in the heteropolysalt nanoparticles are independent from each other; and (ii) The development of mesoporosity in the solid material must be related with a process of alkaline degradation within the core of the nanocrystals aggregating into the particles...
December 7, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27925311/the-chemistry-of-a-non-interacting-vicinal-frustrated-phosphane-borane-lewis-pair
#16
Lisa-Maria Elmer, Gerald Kehr, Constantin G Daniliuc, Melanie Siedow, Hellmut Eckert, Matthias Tesch, Armido Studer, Kamille Williams, Timothy H Warren, Gerhard Erker
The dimesitylphosphinocyclopentene/HB(C6 F5 )2 -derived vicinal trans-1,2-P/B frustrated Lewis pair (FLP) 4 shows no direct phosphane-borane interaction. Toward some reagents it behaves similar to an intermolecular FLP; it cleaves dihydrogen, deprotonates terminal alkynes, and adds to organic carbonyl compounds including CO2 . It shows typical intramolecular FLP reaction modes (cooperative 1,1-additions) to mesityl azide, to carbon monoxide, and to NO. The latter reaction yields a persistent P/B FLPNO nitroxide radical, which undergoes H-atom abstraction reactions...
December 7, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27925306/graphene-oxide-based-enzyme-nanoarchitectonics-for-substrate-channeling
#17
Motilal Mathesh, Jingquan Liu, Colin J Barrow, Wenrong Yang
The controlled spatial organization or compartmentalization of multi-enzyme cascade reactions to transfer a substrate from one enzyme to another for substrate channeling on scaffolds has sparked increasing interest in recent years. Here, we use graphene oxides to study the dependence of the activity of cascade reactions in a closely packed, randomly immobilized enzyme system on a 2 D scaffold. We first observe that the hydrophobicity of graphene oxides and various enzyme architectures for co-immobilized systems are important attributes for achieving high product-conversion rates...
December 7, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27925302/a-three-dimensionally-structured-electrocatalyst-cobalt-embedded-nitrogen-doped-carbon-nanotubes-nitrogen-doped-reduced-graphene-oxide-hybrid-for-efficient-oxygen-reduction
#18
Changting Wei, Hongjing Wang, Kamel Eid, Jeonghun Kim, Jung Ho Kim, Zeid Abdullah Alothman, Yusuke Yamauchi, Liang Wang
To develop low-cost and efficient oxygen reduction reaction (ORR) catalysts, a novel hybrid comprising cobalt-embedded nitrogen-doped carbon nanotubes and nitrogen-doped reduced graphene oxide (Co-NCNT/NrGO-800) was simply prepared by pyrolysis. The combination of nanotubes and graphene, and the efficient doping with cobalt and nitrogen, greatly contribute to the excellent ORR performance. This optimized Co-NCNT/NrGO catalyst exhibits a positive onset potential of 0.91 V and a half-wave potential of 0.82 V, combined with a relatively low peroxide yield, better durability, and better methanol tolerance than commercially available Pt/C, which makes it a promising candidate as a low-cost and effective non-precious-metal ORR catalyst...
December 7, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27922730/anchoring-nitrogen-doped-tio2-nanocrystals-on-nitrogen-doped-3d-graphene-frameworks-for-enhanced-lithium-storage
#19
Yan Yu, Xiaowu Liu, Zhenzhong Yang, Lin Gu
An advanced architecture design of nitrogen doped TiO2 anchored on nitrogen doped 3D graphene frameworks composites (denoted as N-TiO2/N-3D GFs) have been fabricated by a facile template process and further NH3 treatment. The 3D graphene framework allows the electrolyte penetrate into the inverse opal structure and possess high electronic conductivity. The intimate contact between the N-TiO2 and the graphene suppresses the growth and aggregation of TiO2 nanoparticles during heating process, leading to decreased Li+ diffusion length...
December 6, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27922726/bichromophoric-compounds-with-orthogonally-and-parallelly-arranged-chromophores-separated-by-rigid-spacers
#20
Dirk N H Meineke, Mariano L Bossi, Haisen Ta, Vladimir N Belov, Stefan W Hell
Electronic energy transfer (EET) between chromophores is of fundamental importance for many biological processes and optoelectronic devices. However, common models fall short in fully describing the process, especially in bichromophoric model systems with a donor and acceptor connected by a rigid linker providing perpendicular geometries. Herein, we report a novel strategy to prepare bichromophores containing adamantane or 2-(2-adamantylidene)-adamantane as rigid spacers, providing a fixed distance between chromophores, and their parallel or perpendicular arrangement without chromophore rotation...
December 6, 2016: Chemistry: a European Journal
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