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Nature Chemistry

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https://www.readbyqxmd.com/read/30224686/thiophene-and-its-sulfur-inhibit-indenoindenodibenzothiophene-diradicals-from-low-energy-lying-thermal-triplets
#1
Justin J Dressler, Mitsuru Teraoka, Guzmán L Espejo, Ryohei Kishi, Shota Takamuku, Carlos J Gómez-García, Lev N Zakharov, Masayoshi Nakano, Juan Casado, Michael M Haley
Many qualitative structure-property correlations between diradical character and emerging molecular properties are known. For example, the increase of diradical character further decreases the singlet-triplet energy gap. Here we show that inclusion of thiophenes within a quinoidal polycyclic hydrocarbon imparts appreciable diradical character yet retains the large singlet-triplet energy gap, a phenomenon that has no precedent in the literature. The low aromatic character of thiophene and its electron-rich nature are the key properties leading to these unique findings...
September 17, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30224685/carbohydrate-stabilization-extends-the-kinetic-limits-of-chemical-polysaccharide-depolymerization
#2
Ydna M Questell-Santiago, Raquel Zambrano-Varela, Masoud Talebi Amiri, Jeremy S Luterbacher
Polysaccharide depolymerization is an essential step for valorizing lignocellulosic biomass. In inexpensive systems such as pure water or dilute acid mixtures, carbohydrate monomer degradation rates exceed hemicellulose-and especially cellulose-depolymerization rates at most easily accessible temperatures, limiting sugar yields. Here, we use a reversible stabilization of xylose and glucose by acetal formation with formaldehyde to alter this kinetic paradigm, preventing sugar dehydration to furans and their subsequent degradation...
September 17, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30224684/spontaneous-doping-of-the-basal-plane-of-mos-2-single-layers-through-oxygen-substitution-under-ambient-conditions
#3
János Pető, Tamás Ollár, Péter Vancsó, Zakhar I Popov, Gábor Zsolt Magda, Gergely Dobrik, Chanyong Hwang, Pavel B Sorokin, Levente Tapasztó
The chemical inertness of the defect-free basal plane confers environmental stability to MoS2 single layers, but it also limits their chemical versatility and catalytic activity. The stability of pristine MoS2 basal plane against oxidation under ambient conditions is a widely accepted assumption however, here we report single-atom-level structural investigations that reveal that oxygen atoms spontaneously incorporate into the basal plane of MoS2 single layers during ambient exposure. The use of scanning tunnelling microscopy reveals a slow oxygen-substitution reaction, during which individual sulfur atoms are replaced one by one by oxygen, giving rise to solid-solution-type 2D MoS2-x Ox crystals...
September 17, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30202105/author-correction-amine-hemilability-enables-boron-to-mechanistically-resemble-either-hydride-or-proton
#4
C Frank Lee, Diego B Diaz, Aleksandra Holownia, Sherif J Kaldas, Sean K Liew, Graham E Garrett, Travis Dudding, Andrei K Yudin
During the revision of this Article prior to publication, a computational study was reported (Vallejos, M. M. & Pellegrinet, S. C. Theoretical study of the BF3 -promoted rearrangement of oxiranyl N-methyliminodiacetic acid boronates. J. Org. Chem. 82, 5917-5925; 2017) that evaluates the nucleophilic boryl transfer mechanism predicted in this Article; this reference has now been added as number 19, and the subsequent references renumbered.
September 10, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30202104/chromopynones-are-pseudo-natural-product-glucose-uptake-inhibitors-targeting-glucose-transporters-glut-1-and-3
#5
George Karageorgis, Elena S Reckzeh, Javier Ceballos, Melanie Schwalfenberg, Sonja Sievers, Claude Ostermann, Axel Pahl, Slava Ziegler, Herbert Waldmann
The principles guiding the design and synthesis of bioactive compounds based on natural product (NP) structure, such as biology-oriented synthesis (BIOS), are limited by their partial coverage of the NP-like chemical space of existing NPs and retainment of bioactivity in the corresponding compound collections. Here we propose and validate a concept to overcome these limitations by de novo combination of NP-derived fragments to structurally unprecedented 'pseudo natural products'. Pseudo NPs inherit characteristic elements of NP structure yet enable the efficient exploration of areas of chemical space not covered by NP-derived chemotypes, and may possess novel bioactivities...
September 10, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30202103/formation-of-the-layered-conductive-magnet-crcl-2-pyrazine-2-through-redox-active-coordination-chemistry
#6
Kasper S Pedersen, Panagiota Perlepe, Michael L Aubrey, Daniel N Woodruff, Sebastian E Reyes-Lillo, Anders Reinholdt, Laura Voigt, Zheshen Li, Kasper Borup, Mathieu Rouzières, Dumitru Samohvalov, Fabrice Wilhelm, Andrei Rogalev, Jeffrey B Neaton, Jeffrey R Long, Rodolphe Clérac
The unique properties of graphene, transition-metal dichalcogenides and other two-dimensional (2D) materials have boosted interest in layered coordination solids. In particular, 2D materials that behave as both conductors and magnets could find applications in quantum magnetoelectronics and spintronics. Here, we report the synthesis of CrCl2 (pyrazine)2 , an air-stable layered solid, by reaction of CrCl2 with pyrazine (pyz). This compound displays a ferrimagnetic order below ∼55 K, reflecting the presence of strong magnetic interactions...
September 10, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30202102/easy-as-one-two-three
#7
Laura Castoldi, Vittorio Pace
No abstract text is available yet for this article.
September 10, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30202101/stereoselective-synthesis-of-a-composite-knot-with-nine-crossings
#8
Liang Zhang, Alexander J Stephens, Alina L Nussbaumer, Jean-François Lemonnier, Pia Jurček, Iñigo J Vitorica-Yrezabal, David A Leigh
The simultaneous synthesis of a molecular nine-crossing composite knot that contains three trefoil tangles of the same handedness and a [Formula: see text] link (a type of cyclic [3]catenane topologically constrained to always have at least three twists within the links) is reported. Both compounds contain high degrees of topological writhe (w = 9), a structural feature of supercoiled DNA. The entwined products are generated from the cyclization of a hexameric Fe(II) circular helicate by ring-closing olefin metathesis, with the mixture of topological isomers formed as a result of different ligand connectivity patterns...
September 10, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30202100/gas-phase-sugar-formation-using-hydroxymethylene-as-the-reactive-formaldehyde-isomer
#9
André K Eckhardt, Michael M Linden, Raffael C Wende, Bastian Bernhardt, Peter R Schreiner
Carbohydrates (CH2 O)n are the formal adducts of carbon (atoms) to water with a repeating unit that structurally resembles H-C̈-OH (hydroxymethylene). Although hydroxymethylene has been suggested as a building block for sugar formation, it is a reactive species that had escaped detection until recently. Here we demonstrate that formaldehyde reacts with its isomer hydroxymethylene to give glycolaldehyde in a nearly barrierless reaction. This carbonyl-ene-type transformation operates in the absence of base and solvent at cryogenic temperatures similar to those found in extraterrestrial environments or interstellar clouds...
September 10, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30202099/what-tangled-webs-we-weave
#10
Edward E Fenlon
No abstract text is available yet for this article.
September 10, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30177780/dynamic-self-correcting-nucleophilic-aromatic-substitution
#11
Wen Jie Ong, Timothy M Swager
Dynamic covalent chemistry, with its ability to correct synthetic dead-ends, allows for the synthesis of elaborate extended network materials in high yields. However, the limited number of reactions amenable to dynamic covalent chemistry necessarily confines the scope and functionality of materials synthesized. Here, we explore the dynamic and self-correcting nature of nucleophilic aromatic substitution (SN Ar), using ortho-aryldithiols and ortho-aryldifluorides that condense to produce redox-active thianthrene units...
September 3, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30177779/narrow-band-single-photon-emission-through-selective-aryl-functionalization-of-zigzag-carbon-nanotubes
#12
Avishek Saha, Brendan J Gifford, Xiaowei He, Geyou Ao, Ming Zheng, Hiromichi Kataura, Han Htoon, Svetlana Kilina, Sergei Tretiak, Stephen K Doorn
The introduction of sp3 defects into single-walled carbon nanotubes through covalent functionalization can generate new light-emitting states and thus dramatically expand their optical functionality. This may open up routes to enhanced imaging, photon upconversion, and room-temperature single-photon emission at telecom wavelengths. However, a significant challenge in harnessing this potential is that the nominally simple reaction chemistry of nanotube functionalization introduces a broad diversity of emitting states...
September 3, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30150727/a-fluorescent-membrane-tension-probe
#13
Adai Colom, Emmanuel Derivery, Saeideh Soleimanpour, Caterina Tomba, Marta Dal Molin, Naomi Sakai, Marcos González-Gaitán, Stefan Matile, Aurélien Roux
Cells and organelles are delimited by lipid bilayers in which high deformability is essential to many cell processes, including motility, endocytosis and cell division. Membrane tension is therefore a major regulator of the cell processes that remodel membranes, albeit one that is very hard to measure in vivo. Here we show that a planarizable push-pull fluorescent probe called FliptR (fluorescent lipid tension reporter) can monitor changes in membrane tension by changing its fluorescence lifetime as a function of the twist between its fluorescent groups...
August 27, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30150726/isoreticular-two-dimensional-magnetic-coordination-polymers-prepared-through-pre-synthetic-ligand-functionalization
#14
J López-Cabrelles, S Mañas-Valero, I J Vitórica-Yrezábal, P J Bereciartua, J A Rodríguez-Velamazán, J C Waerenborgh, B J C Vieira, D Davidovikj, P G Steeneken, H S J van der Zant, G Mínguez Espallargas, E Coronado
Chemical functionalization is a powerful approach to tailor the physical and chemical properties of two-dimensional (2D) materials, increase their processability and stability, tune their functionalities and, even, create new 2D materials. This is typically achieved through post-synthetic functionalization by anchoring molecules on the surface of an exfoliated 2D crystal, but it inevitably alters the long-range structural order of the material. Here we present a pre-synthetic approach that allows the isolation of crystalline, robust and magnetic functionalized monolayers of coordination polymers...
August 27, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30150725/free-atom-like-d-states-in-single-atom-alloy-catalysts
#15
M T Greiner, T E Jones, S Beeg, L Zwiener, M Scherzer, F Girgsdies, S Piccinin, M Armbrüster, A Knop-Gericke, R Schlögl
Alloying provides a means by which to tune a metal catalyst's electronic structure and thus tailor its performance; however, mean-field behaviour in metals imposes limits. To access unprecedented catalytic behaviour, materials must exhibit emergent properties that are not simply interpolations of the constituent components' properties. Here we show an emergent electronic structure in single-atom alloys, whereby weak wavefunction mixing between minority and majority elements results in a free-atom-like electronic structure on the minority element...
August 27, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30150724/micrometre-long-covalent-organic-fibres-by-photoinitiated-chain-growth-radical-polymerization-on-an-alkali-halide-surface
#16
Franck Para, Franck Bocquet, Laurent Nony, Christian Loppacher, Michel Féron, Fréderic Cherioux, David Z Gao, Filippo Federici Canova, Matthew B Watkins
On-surface polymerization is a promising technique to prepare organic functional nanomaterials that are challenging to synthesize in solution, but it is typically used on metal substrates, which play a catalytic role. Previous examples on insulating surfaces have involved intermediate self-assembled structures, which face high barriers to diffusion, or annealing to higher temperatures, which generally causes rapid dewetting and desorption of the monomers. Here we report the photoinitiated radical polymerization, initiated from a two-dimensional gas phase, of a dimaleimide monomer on an insulating KCl surface...
August 27, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30150723/efficient-and-stereodivergent-synthesis-of-unsaturated-acyclic-fragments-bearing-contiguous-stereogenic-elements
#17
Jeffrey Bruffaerts, David Pierrot, Ilan Marek
Synthetic organic strategies that enable the catalytic and rapid assembly of a large array of organic compounds that possess multiple stereocentres in acyclic systems are somewhat rare, especially when it comes to reaching today's high standards of efficiency and selectivity. In particular, the catalytic preparation of a three-dimensional molecular layout of a simple acyclic hydrocarbon skeleton that possesses several stereocentres from simple and readily available reagents still represents a vastly uncharted domain...
August 27, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30150722/non-intuitive-rotational-reorientation-in-collisions-of-no-a-2-%C3%AE-with-ne-from-direct-measurement-of-a-four-vector-correlation
#18
Thomas R Sharples, Joseph G Leng, Thomas F M Luxford, Kenneth G McKendrick, Pablo G Jambrina, F Javier Aoiz, David W Chandler, Matthew L Costen
Stereodynamic descriptions of molecular collisions concern the angular correlations that exist between vector properties of the motion of the participating species, including their velocities and rotational angular momenta. Measurements of vector correlations provide a unique view of the forces acting during collisions, and are a stringent test of electronic-structure calculations of molecular interactions. Here, we present direct measurement of the four-vector correlation between initial and final relative velocities and rotational angular momenta in a molecular collision...
August 27, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30127512/activation-of-diverse-carbon-heteroatom-and-carbon-carbon-bonds-via-palladium-ii-catalysed-%C3%AE-x-elimination
#19
Van T Tran, John A Gurak, Kin S Yang, Keary M Engle
Chemists' ability to synthesize structurally complex, high-value organic molecules from simple starting materials is limited by methods to selectively activate and functionalize strong alkyl C(sp3 ) covalent bonds. Recent activity has focused on the activation of abundant C-O, C-N and C-C bonds via a mechanistic paradigm of oxidative addition of a low-valent, electron-rich transition metal. This approach typically employs nickel(0), rhodium(I), ruthenium(0) and iron catalysts under conditions finely tuned for specific, electronically activated substrates, sometimes assisted by chelating functional groups or ring strain...
August 20, 2018: Nature Chemistry
https://www.readbyqxmd.com/read/30127511/enzyme-powered-motility-in-buoyant-organoclay-dna-protocells
#20
B V V S Pavan Kumar, Avinash J Patil, Stephen Mann
Reconstitution and simulation of cellular motility in microcompartmentalized colloidal objects have important implications for microcapsule-based remote sensing, environmentally induced signalling between artificial cell-like entities and programming spatial migration in synthetic protocell consortia. Here we describe the design and construction of catalase-containing organoclay/DNA semipermeable microcapsules, which in the presence of hydrogen peroxide exhibit enzyme-powered oxygen gas bubble-dependent buoyancy...
August 20, 2018: Nature Chemistry
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