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Metallic hydrogen

Yosuke Hisamatsu
 In this review, we introduce the development of supermolecules, host-guest complexes, and metal complexes formed from the combination of non-covalent interactions and/or coordination bonds, as well as their biological applications. An adenine selective host molecule 1 provides a correctly oriented array of complementary hydrogen bonding sites for the adenine nucleobase. Furthermore, the new DDAA (D: hydrogen bond donor, A: hydrogen bond acceptor) module 4 and ADDA module 7 have been developed as quadruple hydrogen-bonding modules...
2016: Yakugaku Zasshi: Journal of the Pharmaceutical Society of Japan
Soham Mandal, Marian Hebenbrock, Jens Müller
1,N6-Ethenoadenine (eA) and cytosine (C) are able to form two different metal-mediated base pairs. When the glycosidic bonds are arranged in a cisoid manner (i.e. in antiparallel-stranded DNA), the eA:C mispair binds one Ag(I) ion, leading to a mononuclear eA-Ag(I)-C base pair that contains a synergistic hydrogen bond. In contrast, a transoid orientation of the glycosidic bonds (as found in parallel-stranded DNA) results in the formation of a dinuclear metal-mediated base pair eA-Ag(I)2-C.
November 30, 2016: Chemistry: a European Journal
Yun Pei Zhu, Tian Yi Ma, Mietek Jaroniec, Shi Zhang Qiao
In spite of recent advances in the synthesis of hollow micro/nanostructures, the fabrication of three-dimensional electrodes on the basis of these structures remains a major challenge. Herein, we develop an electrochemical sacrificial-template strategy to fabricate hollow Co3 O4 microtube arrays with hierarchical porosity. The resultant unique structures and integrated electrode configurations impart enhanced mass transfer and electron mobility, ensuring high activity and stability in catalyzing oxygen and hydrogen evolution reactions...
November 30, 2016: Angewandte Chemie
Hui Li, Yue-Feng Qiu, Xiao-Li Wang, Jie Yang, Yun-Jiang Yu, Ya-Qin Chen, Yong-di Liu
In this study, Ni/Fe nanoparticles supported by biochar to stimulate the reduction of 1,1,1-trichloroethane (1,1,1-TCA) in groundwater remediation was investigated. In order to enhance the reactivity of ZVI (zero valent iron) nanoparticles, surface modification of ZVI was performed using nickel and biochar. The removal efficiency of 1,1,1-TCA increased from 42.3% to 99.3% as the biochar-to-Ni/Fe mass ratio increased from 0 to 1.0. However a higher biochar-to-Ni/Fe ratio showed little difference in the 1,1,1-TCA degradation efficiency...
November 26, 2016: Chemosphere
Timothée Stassin, Helge Reinsch, Ben Van de Voorde, Stefan Wuttke, Dana D Medina, Norbert Stock, Thomas Bein, Rob Ameloot, Dirk De Vos
Biomass-derived lactic acid (LA) is an important platform chemical towards the sustainable production of numerous materials. However, the fermentation process currently in use is limited by the difficult recovery of the LA product from the fermentation broth and results in the generation of stoichiometric amounts of gypsum waste. Herein, we show that metal-organic frameworks (MOFs) of the UiO-66(Zr) type are effective adsorbents for the separation of LA from aqueous (buffer) solutions. These frameworks based on zirconium clusters and terephthalic acid derivatives display a tremendous uptake (up to 42 wt %) and a high affinity for LA...
November 29, 2016: ChemSusChem
Xuyang Wang, Xin Gan, Tao Hu, Kazunori Fujisawa, Yu Lei, Zhong Lin, Ben Xu, Zheng-Hong Huang, Feiyu Kang, Mauricio Terrones, Ruitao Lv
Free-standing and flexible WS2 /WO2.9 /C hybrid membranes are synthesized and used as catalytic electrodes for electrochemical hydrogen evolution, exhibiting a high and stable catalytic activity. In virtue of the synergetic effect, a low onset overpotential of 20 mV and a Tafel slope of 36 mV dec(-1) are achieved.
November 28, 2016: Advanced Materials
E Rangel, E Sansores, E Vallejo, A Hernández-Hernández, P A López-Pérez
The hydrogen spill-over mechanism was studied by applying Density Functional Theory. We used small palladium clusters to act as the catalyst supported on the substrate (comprised of pyridinic and pyrrolic nitrogen doped graphene), in order to study hydrogen dissociation, migration and diffusion. Charge transfer and strong binding between the catalyst and the substrate lead to dissociated states of H2 and prevent clusters from detaching and coalescing. In dissociated cases of H2 on Pd clusters, energy barriers below 0...
November 28, 2016: Physical Chemistry Chemical Physics: PCCP
Jingwen Zhu, Emilie-Laure Zins, Mohammad Esmaïl Alikhani
For over a decade, amine-borane has been considered as a potential chemical hydrogen vector in the context of a search for cleaner energy sources. When catalyzed by organometallic complexes, the reaction mechanisms currently considered involve the formation of β-BH agostic intermediates. A thorough understanding of these intermediates may constitute a crucial step toward the identification of ideal catalysts. Topological approaches such as QTAIM and ELF revealed to be particularly suitable for the description of β-agostic interactions...
December 2016: Journal of Molecular Modeling
Ivan I Naumov, Russell J Hemley
Metallization of dense hydrogen and associated possible high-temperature superconductivity represents one of the key problems of physics. Recent theoretical studies indicate that before becoming a good metal, compressed solid hydrogen passes through a semimetallic stage. We show that such semimetallic phases predicted to be the most stable at multimegabar (∼300  GPa) pressures are not conventional semimetals: they exhibit topological metallic surface states inside the bulk "direct" gap in the two-dimensional surface Brillouin zone; that is, metallic surfaces may appear even when the bulk of the material remains insulating...
November 11, 2016: Physical Review Letters
Xuemei Zhou, Ning Liu, Jochen Schmidt, Axel Kahnt, Andres Osvet, Stefan Romeis, Eva M Zolnhofer, Venkata Ramana Reddy Marthala, Dirk M Guldi, Wolfgang Peukert, Martin Hartmann, Karsten Meyer, Patrik Schmuki
Ball milling TiO2 anatase together with TiH2 can create an effective photocatalyst. The process changes the lattice and electronic structure of anatase. Lattice deformation created by mechanical impact combined with hydride incorporation yield electronic gap-states close to the conduction band of anatase. These provide longer lifetimes of photogenerated charge carriers and lead to an intrinsic cocatalytic activation of anatase for H2 evolution.
November 25, 2016: Advanced Materials
D V Korabel'nikov, Yu N Zhuravlev
The structural and electronic properties of energetic nitrates with organic cations (uronium and 3,3'-diamino-4,4'-azo-1,2,4-triazole) and a metal-organic framework crystal [Ag(ethylenediamine)]NO3 have been investigated using density functional theory including van der Waals interactions. It is found that the linear compressibility of urea nitrate is positive and anisotropic (a ≈ b < c), whereas 3,3'-diamino-4,4'-azo-1,2,4-triazole nitrate and [Ag(ethylenediamine)]NO3 show both positive and negative linear compressibility along the b, c and a-axes, respectively...
November 25, 2016: Physical Chemistry Chemical Physics: PCCP
Teng-Hao Chen, Ilya Popov, Ognjen Š Miljanić
A microporous metal-organic framework (MOF) was synthesized from [Zr6 O4 (OH)4 (C6 H5 COO)12 ] clusters and a triacid ligand based on a shape-persistent arylene ethynylene macrocycle. This framework, dubbed Zr-MCMOF, is held together by metal-ligand coordination and multiple weak interactions: hydrogen bonding, [π⋅⋅⋅π] stacking, and [C-H⋅⋅⋅π] interactions. The rigid ligand has a 9 Å-wide central void, which serves as a predesigned aperture for the 1D channels; all of the porosity of Zr-MCMOF comes from the ligand...
November 7, 2016: Chemistry: a European Journal
Xiaoyong Zhang, Lung Wa Chung
Recently, a lactate racemase was discovered as a new Ni-dependent enzyme with a unique tethered NAD-like cofactor. We report the first computational study aimed at deciphering the previously unclear role of the Ni-tethered cofactor in reactions of lactate racemase. Our calculations revealed that the cofactor increases the dehydrogenation barriers. The formation of a metastable NADH-like pyruvate intermediate and two nearby histidine bases are proposed as the key factors in the racemization reaction. Such destabilization of intermediates by the cofactor is uncommon in enzymatic catalysis...
November 24, 2016: Chemistry: a European Journal
Xiao-Nan Wu, Jilai Li, Maria Schlangen, Shaodong Zhou, Patricio González-Navarrete, Helmut Schwarz
The thermal reactivity of the heteronuclear metal-oxide cluster cations [XAlO₄]·+ (X = V, Nb and Ta) towards methane has been studied by using mass spectrometry in conjunction with quantum mechanical calculations. Experimentally, hydrogen-atom transfer (HAT) from methane is mediated by all the three oxide clusters at ambient conditions. However, [VAlO₄]·+ is unique in that this cluster transforms directly methane into formaldehyde. The absence of this reaction for the Nb and Ta analogues demonstrates a striking doping effect on the chemoselectivity in the conversion of methane...
November 24, 2016: Chemistry: a European Journal
Stefano F Pizzolato, Beatrice S L Collins, Thomas van Leeuwen, Ben Lucas Feringa
The emerging field of artificial photoswitchable catalysis has recently shown striking examples of functional light-responsive systems allowing for dynamic control of activity and selectivity in organocatalysis and metal-catalysed transformations. While our group has already disclosed systems featuring first generation molecular motors as the switchable central core, a design based on second generation molecular motors is lacking. Herein, the syntheses of two bifunctionalized molecular switches based on a photoresponsive tetrasubstituted alkene core are reported...
November 23, 2016: Chemistry: a European Journal
Olga Ekkert, Andrew J P White, Mark R Crimmin
Through a dramatic advance in the coordination chemistry of the zinc-hydride bond, we describe the trajectory for the approach of this bond to transition metals. The dynamic reaction coordinate was interrogated through analysis of a series of solid state structures and is one in which the TM-H-Zn angle becomes increasingly acute as the TM-Zn distance decreases. Parallels may be drawn with the oxidative addition of boron-hydrogen and silicon-hydrogen bonds to transition metal centers.
November 23, 2016: Angewandte Chemie
Renhao Dong, Zhikun Zheng, Diana Tranca, Jian Zhang, Naisa Chandrasekhar, Shaohua Liu, Xiaodong Zhuang, Gotthard Seifert, Xinliang Feng
Carbon electrocatalysts consisting of metal complexes (such as MNx and MSx) are promising candidates for use as alternatives to high-cost Pt catalysts for the hydrogen evolution reaction (HER). However, the exact HER active sites remain elusive. Here, we selectively incorporate the molecular metal dithiolene-diamine (MS2N2, M=Co and Ni), metal bis(dithiolene) (MS4), and metal bis(diamine) (MN4) complexes into carbon-rich 2D metal-organic frameworks (2D MOFs) as model carbon electrocatalysts. The 2D MOF single layers, powders, and composites with graphene are thus prepared and devote definite active sites for H2 generation...
November 22, 2016: Chemistry: a European Journal
Cuize Yao, Shiting Yu, Xiuqing Li, Ze Wu, Jiajie Liang, Qiangqiang Fu, Wei Xiao, Tianjiu Jiang, Yong Tang
Here, we describe the development of a triangular silver nanoprism (AgNPR) etching-based plasmonic ELISA for the colorimetric determination of Cr(III) levels in environmental water samples. This involved the creation of a novel signal generation system (substrate reaction solution) for a competitive ELISA in which hydrogen peroxide (H2O2) is used to etch triangular AgNPRs, inducing a change in color. This is achieved by controlling the H2O2 concentration that remains after degradation by catalase, which is conjugated to the secondary antibody of the ELISA...
November 22, 2016: Analytical and Bioanalytical Chemistry
Bora Karasulu, René H J Vervuurt, Wilhelmus M M Kessels, Ageeth A Bol
Integrating metals and metal oxides with graphene is key in utilizing its extraordinary material properties that are ideal for nanoelectronic and catalyst applications. Atomic layer deposition (ALD) has become a key technique for depositing ultrathin, conformal metal(oxide) films. ALD of metal(oxide) films on graphene, however, remains a genuine challenge due to the chemical inertness of graphene. In this study we address this issue by combining first-principles density functional theory (DFT) simulations with ALD experiments...
November 23, 2016: Nanoscale
Mahmoud Ibrahim, Raju Poreddy, Karine Philippot, Anders Riisager, Eduardo J Garcia-Suarez
Polyvinylpyrrolidone-stabilized Rh nanoparticles (RhNPs/PVP) of ca. 2.2 nm in size were prepared by the hydrogenation of the organometallic complex [Rh(η(3)-C3H5)3] in the presence of PVP and evaluated as a catalyst in the hydrogenation of a series of arene substrates as well as levulinic acid and methyl levulinate. The catalyst showed excellent activity and selectivity towards aromatic ring hydrogenation compared to other reported transition metal-based catalysts under mild reaction conditions (room temperature and 1 bar H2)...
November 23, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
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