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Journal of the American Chemical Society

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https://www.readbyqxmd.com/read/30240562/kinetic-strategies-for-the-formation-of-graphyne-nanowires-via-sonogashira-coupling-on-ag-111
#1
Tao Wang, Jianmin Huang, Haifeng Lv, Qitang Fan, Lin Feng, Zhijie Tao, Huanxin Ju, Xiaojun Wu, Steven L Tait, Junfa Zhu
The selection of a reaction pathway with high energy barrier in a multipath on-surface reaction system has been chal-lenging. Herein, we report the successful control of the reaction system of 1,1'-biphenyl, 4-bromo-4'-ethynyl (BPBE) on Ag(111), in which three coupling reactions (Glaser, Ullman, Sonogashira) are involved. Either graphdiyne (GDY) or graphyne (GY) nanowires can be formed by distinct kinetic strategies. As the energetically favorable pathway, the formation of GDY nanowire is achieved by hierarchical activation of Glaser (with lowest energy barrier) and Ullman coupling of BPBE...
September 21, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30240211/tandem-allylation-1-2-boronate-rearrangement-for-the-asymmetric-synthesis-of-indolines-with-adjacent-quaternary-stereocenters
#2
Santanu Panda, Joseph M Ready
A three-component coupling using lithiated indoles, boronate esters and allylic acetates generates chiral indolines with adjacent quaternary stereocenters. Successful stereocontrol required the use of phosphoramadite ligands not previously described for orgranopalladium chemistry. Mechanistic studies indicate a monodentate PdL intermediate, and a stepwise allylation-aryl/alkyl migration. A protodeborylation strategy was used to install a C-H bond in place of the C-B bond. A photoredox cou-pling was used to replace C-B bond with a C-C bond in a highly diastereoselective manner...
September 21, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30240200/cell-permeable-activity-based-ubiquitin-probes-enable-intracellular-profiling-of-human-deubiquitinases
#3
Weijun Gui, Christine A Ott, Kun Yang, Jedidiah S Chung, Siqi Shen, Zhihao Zhuang
Advancement in our knowledge of deubiquitinases (DUBs) and their biological functions requires biochemical tools permitting interrogation of DUB activities under physiologically relevant conditions. Activity-based DUB probes (DUB ABPs) have been widely used in investigating the function and activity of DUBs. However, most ubiquitin (Ub)-based DUB ABPs are not cell-permeable, limiting their utility to purified proteins and cell lysates. Lysis of cells usually leads to dilution of the cytoplasm and disruption of the normal cellular organization, which may alter the activity of many DUBs and DUB complexes...
September 21, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30239198/construction-of-challenging-proline-proline-junctions-via-diselenide-selenoester-ligation-chemistry
#4
Jessica Sayers, Phillip M T Karpati, Nicholas J Mitchell, Anna M Goldys, Stephen M Kwong, Neville Firth, Bun Chan, Richard J Payne
Polyproline sequences are highly abundant in prokaryotic and eukaryotic proteins where they serve as key components of secondary structure. To date, construction of the proline-proline motif has not been possible owing to steric congestion at the ligation junction, together with an n→π* electronic interaction that reduces the reactivity of acylated proline residues at the C terminus of peptides. Here, we harness the reactivity of prolyl selenoesters and a trans-γ-selenoproline moiety to access the elusive proline-proline junction for the first time via a diselenide-selenoester ligation-deselenization manifold...
September 21, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30238744/hierarchical-self-organization-of-chiral-columns-from-chiral-supramolecular-spheres
#5
Dipankar Sahoo, Mohammad R Imam, Mihai Peterca, Benjamin E Partridge, Daniela A Wilson, Xiangbing Zeng, Goran Ungar, Paul A Heiney, Virgil Percec
The supramolecular column is an archetypal architecture in the field of periodic liquid crystalline and crystalline arrays. Columns are generated via self-assembly, co-assembly, and polymerization of monomers containing molecules shaped as discs, tapered, twin- and Janus-tapered, crowns, hat-shaped crowns, and fragments thereof. These supramolecular columns can be helical and therefore exhibit chirality. In contrast, spheres represent a fundamentally distinct architecture, generated from conical and crown-like molecules, which self-organize into body-centered cubic (BCC), Pm3¯n cubic (also known as Frank-Kasper A15), and tetragonal (also known as Frank-Kasper σ) phases...
September 21, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30230822/blue-emitting-single-crystalline-assembly-of-metal-halide-clusters
#6
Chenkun Zhou, Haoran Lin, Michael Worku, Jennifer Neu, Yan Zhou, Yu Tian, Sujin Lee, Peter Djurovich, Theo Siegrist, Biwu Ma
The rich chemistry of organic-inorganic metal halide hybrids has enabled the development of a variety of crystalline structures with controlled morphological and molecular dimensionalities. Here we report for the first time a single crystalline assembly of metal halide clusters, (C9 NH20 )7 (PbCl4 )Pb3 Cl11 , in which lead chloride tetrahedrons (PbCl4 2- ) and face-sharing lead chloride trimer clusters (Pb3 Cl11 5- ) cocrystallize with organic cations (C9 NH20 + ) to form a periodical zero-dimensional (0D) structure at the molecular level...
September 21, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30227706/enhancing-pore-environment-complexity-using-a-trapezoidal-linker-toward-stepwise-assembly-of-multivariate-quinary-metal-organic-frameworks
#7
Jiandong Pang, Shuai Yuan, Junsheng Qin, Mingyan Wu, Christina T Lollar, Jialuo Li, Ning Huang, Bao Li, Peng Zhang, Hong-Cai Zhou
Multicomponent metal-organic frameworks (MOFs) promise the precise placement of synergistic functional groups with atomic-level precision, capable of promoting fascinating developments in basic sciences and applications. However, the complexity of multicomponent systems poses a challenge to their structural design and synthesis. Herein, we show that linkers of low symmetry can bring new opportunities to the construction of multicomponent MOFs. A carbazole-tetracarboxylate linker of  C s point group symmetry was designed and combined with an 8-connected Zr6 cluster to generate a low-symmetry MOF, PCN-609...
September 21, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30226769/photochemistry-of-so-2-at-the-air-water-interface-a-source-of-oh-and-hoso-radicals
#8
Marilia T C Martins-Costa, Josep M Anglada, Joseph S Francisco, Manuel F Ruiz-López
The photochemistry of sulfur dioxide in the near UV-vis energy range has been studied in aqueous environments. The combination of previously reported experimental measurements with accurate quantum chemical calculations achieved in this work reveals that the process represents an important source of OH radicals in the troposphere. It implicates the reaction of the lowest triplet excited state of SO2 with a water molecule. When the process occurs in the gas-phase, photochemical OH production is only significant under high humidity conditions and high SO2 concentrations as those measured in polluted urban areas...
September 21, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30217108/ir-iii-catalyzed-stereoselective-haloamidation-of-alkynes-enabled-by-ligand-participation
#9
Seung Youn Hong, Junsoo Son, Dongwook Kim, Sukbok Chang
Described herein is the application of a strategy of ligand participation for the Ir-catalyzed imido transfer into alkynes. On the basis of a stoichiometric [3 + 2] cycloaddition of Cp*Ir(III)(κ2 - N, O-chelate) with alkynyl dioxazolone, a catalytic haloamidation was developed for the first time by employing [Cp*IrCl2 ]2 precatalyst and NaX salts (X = Cl or Br) as practical halide sources to furnish synthetically versatile Z-(halovinyl)lactams with excellent stereoselectivity.
September 21, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30207468/a-thiourea-tether-in-the-second-coordination-sphere-as-a-binding-site-for-co-2-and-a-proton-donor-promotes-the-electrochemical-reduction-of-co-2-to-co-catalyzed-by-a-rhenium-bipyridine-type-complex
#10
Eynat Haviv, Dima Azaiza-Dabbah, Raanan Carmieli, Liat Avram, Jan M L Martin, Ronny Neumann
The electrochemical reduction of CO2 has been extensively investigated in recent years, with the expectation that a detailed mechanistic understanding could achieve the goal of finding a stable catalyst with high turnover frequencies and low reduction potentials. In the catalytic cycle of the carbon dioxide hydrogenase enzyme, it has been suggested that the reduced metal center reacts with CO2 to form a carboxylate intermediate that is stabilized by hydrogen bonding using a histidine moiety in the second coordination sphere...
September 21, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30204442/photoinduced-heterocyclic-ring-opening-of-furfural-distinct-open-chain-product-identification-by-ultrafast-x-ray-transient-absorption-spectroscopy
#11
Aditi Bhattacherjee, Kirsten Schnorr, Sven Oesterling, Zheyue Yang, Tian Xue, Regina de Vivie-Riedle, Stephen R Leone
The ultraviolet-induced photochemistry of five-membered heterocyclic rings often involves ring opening as a prominent excited-state relaxation pathway. The identification of this particular photoinduced mechanism, however, presents a challenge for many experimental methods. We show that femtosecond X-ray transient absorption spectroscopy at the carbon K-edge (∼284 eV) provides core-to-valence spectral fingerprints that enable the unambiguous identification of ring-opened isomers of organic heterocycles. The unique differences in the electronic structure between a carbon atom bonded to the oxygen in the ring versus a carbon atom set free of the oxygen in the ring-opened product are readily apparent in the X-ray spectra...
September 21, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30196697/modulation-of-water-vapor-sorption-by-a-fourth-generation-metal-organic-material-with-a-rigid-framework-and-self-switching-pores
#12
Shi-Yuan Zhang, Stephanie Jensen, Kui Tan, Lukasz Wojtas, Matthew Roveto, Jeremy Cure, Timo Thonhauser, Yves J Chabal, Michael J Zaworotko
Hydrolytically stable adsorbents are needed for water vapor sorption related applications; however, design principles for porous materials with tunable water sorption behavior are not yet established. Here, we report that a platform of fourth-generation metal-organic materials (MOMs) with rigid frameworks and self-switching pores can adapt their pores to modulate water sorption. This platform is based upon the hydrolytically stable material CMOM-3S, which exhibits bnn topology and is composed of rod building blocks based upon S-mandelate ligands, 4,4-bipyridine ligands, and extraframework triflate anions...
September 21, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30192541/a-dual-app-nucleoside-probe-provides-structural-insights-into-the-human-telomeric-overhang-in-live-cells
#13
Sudeshna Manna, Debayan Sarkar, Seergazhi G Srivatsan
Understanding the topology adopted by individual G-quadruplex (GQ)-forming sequences in vivo and targeting a specific GQ motif among others in the genome will have a profound impact on GQ-directed therapeutic strategies. However, this remains a major challenge as most of the tools poorly distinguish different GQ conformations and are not suitable for both cell-free and in-cell analysis. Here, we describe an innovative probe design to investigate GQ conformations and recognition in both cell-free and native cellular environments by using a conformation-sensitive dual-app nucleoside analogue probe...
September 21, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30235415/protein-electronics-chemical-modulation-of-contacts-control-energy-level-alignment-in-gold-azurin-gold-junctions
#14
Jerry A Fereiro, Gilad Porat, Tatyana Bendikov, Israel Pecht, Mordechai Sheves, David Cahen
Making biomolecular electronics a reality will require control over charge transport across biomolecules. Here we show that chemical modulation of the coupling between one of the electronic contacts and the biomolecules in a solid-state junction allows controlling electron transport (ETp) across the junction. Employing the protein Azurin (Az), we achieve such modulation as follows: Az is covalently bound by Au-S bonding to a lithographically prepared Au electrode (Au-Az). Au nanowires (AuNW) onto which linker molecules, with free carboxylic group, are bound via Au-S bonds, serve as top electrode...
September 20, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30235414/synthetic-lateral-metal-semiconductor-heterostructures-of-transition-metal-disulfides
#15
Wei Sun Leong, Qingqing Ji, Nannan Mao, Yimo Han, Haozhe Wang, Aaron J Goodman, Antoine Vignon, Cong Su, Yunfan Guo, Pin-Chun Shen, Zhenfei Gao, David A Muller, William A Tisdale, Jing Kong
Lateral heterostructures with planar integrity form the basis of two-dimensional (2D) electronics and optoelectronics. Here we report that, through a two-step chemical vapor deposition (CVD) process, high-quality lateral heterostructures can be constructed between metallic and semiconducting transition metal disulfide (TMD) layers. Instead of edge epitaxy, polycrystalline monolayer MoS2 in such junctions was revealed to nucleate from the vertices of multilayered VS2 crystals, creating one-dimensional junctions with ultralow contact resistance (0...
September 20, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30234982/a-concave-convex-%C3%AF-%C3%AF-template-approach-enables-the-synthesis-of-10-cycloparaphenylene-fullerene-2-rotaxanes
#16
Youzhi Xu, Ramandeep Kaur, Bingzhe Wang, Martin B Minameyer, Sebastian Gsänger, Bernd Meyer, Thomas Drewello, Dirk M Guldi, Max von Delius
The cycloparaphenylenes (CPPs) are a class of strained macrocycles that until recently were considered beyond the reach of organic synthesis. With its cyclic array of ten para-substituted phenylene rings, [10]CPP possesses a concave π-system that is perfectly preorganized for the strong supramolecular association of convex fullerenes such as C60. Although mechanically interlocked CPP architectures have been observed in the gas phase, the rational synthesis of bulk quantities has not been achieved yet, which is likely due to the fact that conventional template strategies are not amenable to CPP rings that lack heteroatoms...
September 20, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30234979/ni-catalyzed-enantioselective-reductive-diarylation-of-activated-alkenes-by-domino-cyclization-cross-coupling
#17
Kuai Wang, Zhengtian Ding, Zhijun Zhou, Wangqing Kong
A Ni-catalyzed enantioselective reductive diarylation of activat-ed alkenes by domino cyclizative/cross-coupling of two aryl bromides is developed. This reaction proceeds under very mild conditions and shows broad substrate scope, without requiring the use of preformed organometallic reagents. Moreover, this approach provides direct access to enantioenriched bis-heterocycles bearing all-carbon quaternary centers in syntheti-cally useful yield (up to 81%) with excellent enantioselectivity (>30 examples, 90-99% ee)...
September 20, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30234298/nitric-oxide-releasing-cyclodextrins
#18
Haibao Jin, Lei Yang, Mona Jasmine R Ahonen, Mark H Schoenfisch
A series of secondary amine-modified cyclodextrin (CD) derivatives were synthesized with diverse exterior terminal groups (i.e., hydroxyl, methyl, methoxyl, and primary amine). Subsequent reaction with nitric oxide (NO) gas under alkaline condi-tions yielded N-diazeniumdiolate-modified CD derivatives. Adjustable NO payloads (0.6‒2.4 µmol/mg) and release half-lives (0.7‒4.2 h) were achieved by regulating both the amount of secondary amine precursors and the functional groups around the NO donor. The bactericidal action of these NO-releasing cyclodextrin derivatives was evaluated against Pseudo-monas aeruginosa, a Gram-negative pathogen with antibacterial activity proving dependent on both the NO payload and exterior modification...
September 20, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30234293/halogen-bond-asymmetry-in-solution
#19
Sofia Lindblad, Krenare Mehmeti, Alberte X Veiga, Bijan Nekoueishahraki, Jürgen Gräfenstein, Máté Erdélyi
Halogen bonding is the noncovalent interaction of halogen atoms in which they act as electron acceptors. Whereas three-center hydrogen bond complexes, [D... H... D]+ where D is an electron donor, exist in solution as rapidly equilibrating asymmetric species, the analogous halogen bonds, [D... X... D]+ , have been observed so far only to adopt static and symmetric geometries. Herein, we investigate whether halogen bond asymmetry, i.e. a [D-X... D]+ bond geometry, in which one of the D-X bonds is shorter and stronger, could be induced by modulation of electronic or steric factors...
September 20, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/30232877/oriented-external-electric-fields-create-absolute-enantioselectivity-in-diels-alder-reactions-the-importance-of-the-molecular-dipole-moment
#20
Zhanfeng Wang, David Danovich, Rajeev Ramanan, Sason Shaik
The manuscript studies the enantioselectivity and stereoselectivity of Diels-Alder (DA) cycloadditions between cyclopentadiene (CPD) and a variety of dienophiles (ranging from halo-ethenes to cyano-ethenes), under oriented external electric fields (OEEFs). Applying OEEFs oriented in the X/Y-directions, perpendicular to the reaction axis (Z), will achieve complete isomeric and enantiomeric discrimination of the products. Unlike the Z-OEEF, which involve charge-transfer from the diene to the dienophile, and thereby brings about catalysis due to increased intramolecular bonding, an OEEF along X, aligned with the C=C bond of the dienophile, will lead to R/S enantiomeric discrimination by means of intramolecular-bond polarization...
September 20, 2018: Journal of the American Chemical Society
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