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    Chemistry

    Angewandte Chemie Cover
    Journal of the American Chemical Society

    Redox mediators (RMs) are considered an effective countermeasure to reduce the large polarization in lithium–oxygen batteries. Nevertheless, achieving sufficient enhancement of the cyclability is limited by the trade–offs of freely mobile RMs, which are beneficial for charge transport but also trigger the shuttling phenomenon. Here, we successfully decoupled the charge–carrying redox property of RMs and shuttling phenomenon by anchoring the RMs in polymer form, where physical RM migration was replaced by charge transfer along polymer chains. Using a model system of a polymer, PTMA (2,2,6,6–tetramethyl–1–piperidinyloxy–4–yl methacrylate), based on the well–known RM tetramethylpiperidinyloxyl (TEMPO), it is demonstrated that PTMA is capable of functioning as a stationary RM, preserving the redox activity of TEMPO. The efficiency of RM–mediated Li 2 O 2 decomposition remains remarkably stable without the consumption of oxidized RMs or degradation of the lithium anode, resulting in marked improvement of the performance of the lithium–oxygen cell. [...]
    Sat, Jan 18, 2020
    Source: Angewandte Chemie Int. edition Category: CHEMISTRY GENERAL
    A strategically novel synthetic method for the fluoroarylation of allenic ester was successfully developed, which enables an expedient construction of a host of β‐fluoroalkyl‐containing cinnamate derivatives. By resorting to visible light‐promoted gold redox catalysis, this reaction proceeds smoothly under very mild reaction conditions, accommodates a large variety of functional groups, and more importantly allows the incorporation of fluorine and aryl groups in excellent regio‐ and stereoselectivity. The concomitant activation mode for both allene motif and hydrogen fluoride is ascribed as the key for the success of this reaction. [...]
    Sat, Jan 18, 2020
    Source: Angewandte Chemie Int. edition Category: CHEMISTRY GENERAL
    Expanded porphyrins with proper metalation provided us with an excellent opportunity to study excited‐state aromaticity. The coordinated metal helped us to observe the excited‐state aromaticity in the triplet state by the heavy atom effect, but other metalation effects on the excited‐state aromaticity were ambiguous. Here, the excited‐state aromaticity of gold(III) hexaphyrins through the relaxation dynamics was revealed via the electronic and vibrational spectroscopy. The S Q states of gold [26]‐ and [28] hexaphyrins showed interconvertible absorption and IR spectra with those of counterparts in the ground‐state, indicating aromaticity reversal. Furthermore, while the T 1 states of gold [28] hexaphyrins also exhibited reversed aromaticity according to Baird's rule, the ligand‐to‐metal charge transfer state of gold [26] hexaphyrins contributed by the gold metal showed nonaromatic feature due to the odd‐number of π‐electrons. [...]
    Sat, Jan 18, 2020
    Source: Angewandte Chemie Int. edition Category: CHEMISTRY GENERAL
    University of Seville researchers, in collaboration with the University of Nottingham, have managed to create the first image of nanoparticles of stabilised gold with biodegradable and biocompatible systems that have been obtained with 3-D-printng techniques. The image chosen for this test was the logo of the University of Seville. [...]
    Fri, Jan 17, 2020
    Source: PhysOrg Chemistry Category: CHEMISTRY GENERAL
    Simple LEGO bricks can be assembled to more complicated structures, which can be further associated into a wide variety of complex architectures, from automobiles, rockets, and ships to gigantic castles and amusement parks. Such an event of multi-step assembly, so-called 'hierarchical self-assembly,' also happens in living organisms. [...]
    Fri, Jan 17, 2020
    Source: PhysOrg Chemistry Category: CHEMISTRY GENERAL
    A chemist from RUDN University has proposed a new method for the synthesis of secondary propargylamine used to create antidepressants, drugs for Parkinson's disease and other neurodegenerative diseases, as well as malaria. It differs from the known methods in its simplicity and stability of the resulting substance. The paper was published in the Journal of Organic Chemistry. [...]
    Fri, Jan 17, 2020
    Source: PhysOrg Chemistry Category: CHEMISTRY GENERAL
    Manufacturing products from titanium and its alloys using traditional methods remains a complex technological task that requires a lot of time and money. Scientists at South Ural State University have developed a new universal technology for manufacturing titanium alloy parts using additive technologies. The new technology will allow significant savings in further machining. An article about the study was published in Materials. [...]
    Fri, Jan 17, 2020
    Source: PhysOrg Chemistry Category: CHEMISTRY GENERAL
    Transition metal‐catalyzed direct asymmetric reductive amination (ARA) of diaryl or sterically hindered ketones remains unknown and an open challenge. Herein, Ru‐catalyzed direct asymmetric reductive amination of ortho ‐OH‐substituted diaryl and sterically hindered ketones with ammonium salts has been disclosed for the first time, offering a straightforward route toward the synthesis of synthetically useful chiral primary diarylmethylamines and sterically hindered benzylamines (up to 97% yield, 93−>99% ee). The elaborations of chiral amine products into bioactive compounds have been exhibited through manipulations on the removable and convertible ‐OH group. Moreover, gram‐scale synthesis of chiral sterically bulky amine 6ac and its application in the synthesis of a new benzo‐bisoxazine ligand further showcase the utility of this method. [...]
    Fri, Jan 17, 2020
    Source: Angewandte Chemie Int. edition Category: CHEMISTRY GENERAL
    The 60‐year high Bordetella pertussis ( B. pertussis ) infection rate in the world suggests the urgent need for new anti‐pertussis vaccines. Lipopolysaccharide (LPS) of B. pertussis is an attractive antigen for vaccine development. With the presence of multiple rare sugars and unusual glycosyl linkages, B. pertussis LPS is a highly challenging synthetic target. In this work, aided by molecular dynamics simulation and modeling, the pertussis LPS like pentasaccharide was chemically synthesized for the first time. The pentasaccharide was conjugated with a powerful carrier, bacteriophage Qβ as a vaccine candidate. Immunization of mice with the conjugate induced robust anti‐glycan IgG responses with IgG titers reaching several million enzyme‐linked immunosorbent assay (ELISA) units. The antibodies generated were long lasting and boostable, and could recognize multiple clinical strains of B. pertussis , highlighting the potential of Qβ‐glycan as a new anti‐pertussis vaccine. [...]
    Fri, Jan 17, 2020
    Source: Angewandte Chemie Int. edition Category: CHEMISTRY GENERAL
    University of Alberta researchers have developed techniques that save a significant amount of time in developing more efficient carbon capture technologies, which may help lower the costs to use the technologies and increase their adoption as a way to mitigate carbon dioxide emissions. [...]
    Fri, Jan 17, 2020
    Source: PhysOrg Chemistry Category: CHEMISTRY GENERAL

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