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  Subjects -> CHEMISTRY (Total: 846 journals)
    - ANALYTICAL CHEMISTRY (50 journals)
    - CHEMISTRY (597 journals)
    - CRYSTALLOGRAPHY (22 journals)
    - ELECTROCHEMISTRY (25 journals)
    - INORGANIC CHEMISTRY (41 journals)
    - ORGANIC CHEMISTRY (45 journals)
    - PHYSICAL CHEMISTRY (66 journals)

CHEMISTRY (597 journals)                  1 2 3 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 7)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 26)
ACS Catalysis     Full-text available via subscription   (Followers: 31)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 17)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 22)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 39)
ACS Nano     Full-text available via subscription   (Followers: 218)
ACS Photonics     Full-text available via subscription   (Followers: 10)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 20)
Acta Chemica Iasi     Open Access   (Followers: 2)
Acta Chimica Sinica     Full-text available via subscription  
Acta Chimica Slovaca     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access  
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Scientifica Naturalis     Open Access   (Followers: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 7)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 5)
Advanced Functional Materials     Hybrid Journal   (Followers: 48)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 53)
Advances in Chemical Science     Open Access   (Followers: 12)
Advances in Chemistry     Open Access   (Followers: 12)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Enzyme Research     Open Access   (Followers: 10)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 14)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 18)
Advances in Nanoparticles     Open Access   (Followers: 12)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15)
Advances in Polymer Science     Hybrid Journal   (Followers: 40)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 18)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Science and Technology     Full-text available via subscription   (Followers: 10)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 2)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 65)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 14)
American Journal of Chemistry     Open Access   (Followers: 25)
American Journal of Plant Physiology     Open Access   (Followers: 13)
American Mineralogist     Full-text available via subscription   (Followers: 12)
Analyst     Full-text available via subscription   (Followers: 38)
Angewandte Chemie     Hybrid Journal   (Followers: 153)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 204)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 1)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 3)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 7)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 14)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 6)
Applied Spectroscopy     Full-text available via subscription   (Followers: 22)
Applied Surface Science     Hybrid Journal   (Followers: 26)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 2)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Atomization and Sprays     Full-text available via subscription   (Followers: 3)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 9)
Biochemistry     Full-text available via subscription   (Followers: 278)
Biochemistry Insights     Open Access   (Followers: 5)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 9)
Bioinspired Materials     Open Access   (Followers: 3)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access  
Biomacromolecules     Full-text available via subscription   (Followers: 18)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 109)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 99)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 2)
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 2)
Canadian Journal of Chemistry     Full-text available via subscription   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 3)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 67)
Catalysis for Sustainable Energy     Open Access   (Followers: 6)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 7)
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 12)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 69)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 23)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 19)
Chemical Reviews     Full-text available via subscription   (Followers: 165)
Chemical Science     Open Access   (Followers: 21)
Chemical Technology     Open Access   (Followers: 15)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 4)
Chemical Week     Full-text available via subscription   (Followers: 7)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 55)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 25)
ChemInform     Hybrid Journal   (Followers: 7)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 6)
Chemistry & Biology     Full-text available via subscription   (Followers: 30)
Chemistry & Industry     Hybrid Journal   (Followers: 5)
Chemistry - A European Journal     Hybrid Journal   (Followers: 137)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 17)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Hybrid Journal   (Followers: 2)
Chemistry Letters     Full-text available via subscription   (Followers: 43)
Chemistry of Materials     Full-text available via subscription   (Followers: 189)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry-Didactics-Ecology-Metrology     Open Access  
ChemistryOpen     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 2)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 8)
ChemPlusChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 10)
Chromatographia     Hybrid Journal   (Followers: 23)
Chromatography Research International     Open Access   (Followers: 7)
Clay Minerals     Full-text available via subscription   (Followers: 9)
Cogent Chemistry     Open Access  
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 10)
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 8)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 3)
Combustion Science and Technology     Hybrid Journal   (Followers: 18)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 2)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 2)
Copernican Letters     Open Access  
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Crystal Structure Theory and Applications     Open Access   (Followers: 3)
CrystEngComm     Full-text available via subscription   (Followers: 10)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Metabolomics     Hybrid Journal   (Followers: 4)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 48)
Dalton Transactions     Full-text available via subscription   (Followers: 18)
Detection     Open Access   (Followers: 2)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)
Diamond and Related Materials     Hybrid Journal   (Followers: 11)
Dislocations in Solids     Full-text available via subscription  
Doklady Chemistry     Hybrid Journal  
Drying Technology: An International Journal     Hybrid Journal   (Followers: 3)
Eclética Química     Open Access   (Followers: 1)
Ecological Chemistry and Engineering S     Open Access   (Followers: 4)
Ecotoxicology and Environmental Contamination     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
EJNMMI Radiopharmacy and Chemistry     Open Access  
Elements     Full-text available via subscription   (Followers: 2)
Environmental Chemistry     Hybrid Journal   (Followers: 8)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 4)
Environmental Science & Technology Letters     Full-text available via subscription   (Followers: 5)
Environmental Science : Nano     Partially Free   (Followers: 1)
Environmental Toxicology & Chemistry     Hybrid Journal   (Followers: 19)

        1 2 3 | Last

Journal Cover Chemistry - An Asian Journal
  [SJR: 1.833]   [H-I: 75]   [15 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1861-4728 - ISSN (Online) 1861-471X
   Published by John Wiley and Sons Homepage  [1583 journals]
  • Photo-Induced Cyclization of (o-Alkylbenzoyl)phosphonates to
           Benzocyclobutenols
    • Authors: Naoki Ishida; Takaaki Yano, Tatsuya Yuhki, Masahiro Murakami
      Abstract: (o-Alkylbenzoyl)phosphonates readily cyclize to highly strained benzocyclobutenols simply upon irradiation with UV light. The remarkable efficiency is ascribed to the electron-accepting character of the phosphonate substituent, which facilitates thermal ring closing of the o-quinodimethane intermediate and suppresses reversion to the starting carbonyl compound.
      PubDate: 2017-05-23T21:20:35.337571-05:
      DOI: 10.1002/asia.201700766
       
  • Impact of Hydrogen Bonding on the Susceptibility of Peptides to Oxidation
    • Authors: Bun Chan; Damian Moran, Christopher J. Easton, Leo Radom
      Abstract: The tendency of peptides to be oxidized is intimately connected with their function and even their ability to exist in an oxidative environment. Here we report high-level theoretical studies that show that hydrogen bonding can alter the susceptibility of peptides to oxidation, with complexation to a hydrogen-bond acceptor facilitating oxidation, and vice versa, impacting the feasibility of a diverse range of biological processes. It can even provide an energetically viable mechanistic alternative to direct hydrogen-atom abstraction. We find that hydrogen bonding to representative reactive groups leads to a broad (≈400 kJ mol−1) spectrum of ionization energies in the case of model amide, thiol and phenol systems. While some of the oxidative processes at the extreme ends of the spectrum are energetically prohibitive, subtle environmental and solvent effects could potentially mitigate the situation, leading to a balance between hydrogen bonding and oxidative susceptibility.Ionization energy spectrum: Increased hydrogen bonding, through to full deprotonation, results in a spectrum of ionization energies for key functional groups, leading to subtle mechanisms and environmental factors that are likely to provide a fine balance between hydrogen bonding and oxidation, which impacts on a broad range of oxidative processes involving peptides.
      PubDate: 2017-05-23T08:05:29.350106-05:
      DOI: 10.1002/asia.201700492
       
  • Aqueous Oxidations Started by TiO₂ Photo-induced Holes Can Be a
           Rate-determining Step
    • Authors: Yuanzheng Gong; Chun Yang, Hongwei Ji, Chuncheng chen, Wanhong Ma, Jincai Zhao
      Abstract: In aqueous TiO2 photocatalytic hydroxylation of weakly polar aromatics, unlike usual polar aromatic cases of normal H/D KIEs, a series of inverse H/D KIEs of 0.7~0.8 were observed, which indicated that the oxidtion started by photo-induced hvb+ can be the rate-determining step.
      PubDate: 2017-05-23T03:20:24.855003-05:
      DOI: 10.1002/asia.201700658
       
  • Aziridine-Mediated Ligation at Phenylalanine and Tryptophan Sites
    • Authors: Kiran Bajaj; Rajeev Sakhuja
      Abstract: An efficient approach towards peptide synthesis has been described that allows an easy access to variety of small peptides via one-pot aziridine-mediated ligation-desulfurization strategy. The present protocol afforded a library of phenylalanine and tryptophan containing α-peptides in good yields by regioselective ring-opening of aziridine-3-aryl-2-carboxylates with peptide thioacids followed by desulfurization.
      PubDate: 2017-05-23T02:20:26.504238-05:
      DOI: 10.1002/asia.201700538
       
  • Hydrogen bond-Driven Self–Assembly between Amidinium Cations and
           Carboxylate Anions: A Combined Molecular Dynamics, NMR Spectroscopy, and
           Single Crystal X-ray Diffraction Study
    • Authors: Michael Thomas; Thomas Anglim Lagones, Martyna Judd, Mahbod Morshedi, Megan L. O'Mara, Nicholas G. White
      Abstract: A combination of molecular dynamics (MD), NMR spectroscopy, and single crystal X-ray diffraction (SCXRD) techniques was used to probe the self–assembly of para- and meta-bis(amidinium) compounds with para-, meta-, and ortho-dicarboxylates. Good concordance was observed between the MD and experimental results. In DMSO solution, the systems form several rapidly exchanging assemblies, in part because a range of hydrogen bonding interactions is possible between the amidinium and carboxylate moieties. Upon crystallization, the majority of the systems form 1D supramolecular polymers, which are held together by short N−H⋅⋅⋅O hydrogen bonds.Understanding self–assembly: The interaction between bis(amidinium) cations and dicarboxylate anions was studied in a range of solvents using NMR spectroscopy and molecular dynamics techniques. The results indicate that both linear and cyclic architectures are present in solution, and they can be crystallized to give 1D hydrogen bonded polymeric systems.
      PubDate: 2017-05-23T01:45:50.852963-05:
      DOI: 10.1002/asia.201700406
       
  • Effective, Low Cost Recovery of Toxic Arsenate Anions from Water Using
           Hollow Sphere Trapper Geodes
    • Authors: Sherif A. El-Safty; Mohamed A. Shenashen, Naeem Akhtar, Mahmoud M. Selim, Wafaa M. Morsy, Hitoshi Yamaguchi, Satoshi Kawada, Abdulaziz A. Alhamid, Naoki Ohashi, Izumi Ichinose, Ahmed Alamoudi
      Abstract: Because of the devastating impacts of arsenic to terrestrial and aquatic organisms, recovery, removal, disposal and management of arsenic-contaminated water has a considerable challenge and become an urgent necessity in the field of water treatment. This study reports control fabrication of low-cost adsorbents based on microscopic NiO hollow sphere geode-shelled a 100 nm of poly-CN nano-sphere particles-like nodules of poly-carbon nitride that intrinsically stacked and wrapped around the hollow nest spheres to form 500-700 nm shell. This C-, N-doped NiO hollow sphere adsorbent (named CNN) with multi-diffusive open-pore holes, and caves with connective open macro/meso-windows along the entire and well-dispersed hollow sphere particles lead to create trap vesicles for capture/extraction/separation of arsenate (AsO43 −) species from an aqueous solution. The CNN considered as potentially attractive adsorbent for AsO43 − species due to (i) superior removal/trapping capacity from water samples, and (ii) selectively AsO43 − trapping from real sample water that mainly includes chloride and nitrate anions and Fe2+, and Mn2+, Ca2+, and Mg2+ cations. The structural stability of hierarchal geodes in trap vehicle-shaped nests after 20 reuse/cycles without significant decrease in recovery efficiency of AsO43 - species was evident. For affording control of low-capital adsorbent and toxin waste-management, such superior CNN dead-end AsO43 - trapping/recovery system may lead to the following; (i) evidently enabled continuous control on the AsO43 - disposal management to re-diffuse or spread in water scarcity environment, and (ii) economically presented low-cost and eco-friendly CNN adsorbent for AsO43 - species, and (iii) selectively produced water-free-arsenate species. These CNN trapper geodes show potential to be excellent adsorbent candidates for environment remediation tools and humanhealthcare from toxicants.
      PubDate: 2017-05-22T21:21:17.068086-05:
      DOI: 10.1002/asia.201700666
       
  • Activation of CO2 by Vanadium Nitrogenase
    • Authors: Nathaniel Sickerman; Yilin Hu, Markus Walter Ribbe
      Abstract: The reduction of CO2 into useful products, including hydrocarbon fuels, is an ongoing area of particular interest due to efforts to mitigate buildup of this greenhouse gas. While the industrial Fischer-Tropsch process can facilitate the hydrogenation of CO2 with H2 to form short-chain hydrocarbon products under high temperatures and pressures, a desire to perform these reactions under ambient conditions has inspired the use of biological approaches. Particularly, enzymes offer insight into how to activate and reduce CO2, but only one enzyme, nitrogenase, can perform the multielectron, multiproton reduction of CO¬2 into hydrocarbons. The vanadium-containing variant, V-nitrogenase, displays especial reactivity towards the hydrogenation of CO and CO2. This Focus Review discusses recent progress towards the activation and reduction of CO2 with three primary V-nitrogenase systems. These systems span both ATP-dependent and ATP-independent processes and utilize approaches with whole cells, isolated proteins, and extracted cofactors.
      PubDate: 2017-05-22T13:20:27.221542-05:
      DOI: 10.1002/asia.201700624
       
  • Pd Nanoparticles immobilized on individual calcium carbonate plate derived
           from mussel shell waste: An eco-friendly catalyst for copper-free
           Sonogashira coupling reaction
    • Authors: Trin Saetan; Chutiparn Lertvachirapaiboon, Ekgasit Sanong, Mongkol Sukwattanasinitt, Sumrit Wacharasindhu
      Abstract: Conversion of waste into high value materials has been considered an important sustainability strategy in modern chemical industries. Large volume of shell waste is generated globally from mussel cultivation. In this work, mussel shell wastes (Perna viridis) are transformed into individual calcium carbonate plate (ICCP) and apply as a support for heterogeneous catalyst. Palladium nanoparticles (3-6 nm) are deposited with even dispersion on ICCP surface as demonstrated by X-ray diffraction and scanning electron microscopy. Using the system, Sonogashira cross coupling reactions between aryl iodides and terminal acetylenes are accomplished in high yields with the use of 1% Pd/ICCP in the presence of potassium carbonate without any use of copper metal or external ligand. The Pd/ICCP can also be reused up to three times with remaining activity over 90% and negligible Pd metal leaching. This work demonstrates that mussel shell waste can be used as an inexpensive and effective support for metal catalysts in coupling reactions as demonstrated by our successful performance of Pd catalyzed, copper-free Sonogashira cross coupling process
      PubDate: 2017-05-22T10:21:49.272613-05:
      DOI: 10.1002/asia.201700537
       
  • Hetero Face-to-Face Porphyrin Array with the Cooperative Effects of
           Coordination and Host-Guest Complexation
    • Authors: Yusuke Chiba; Maning Liu, Yasuhiro Tachibana, Tetsuaki Fujihara, Yasushi Tsuji, Jun Terao
      Abstract: We successfully synthesized a hetero face-to-face porphyrin array composed of ZnTPP and RuTPP(DABCO)₂ (TPP: 5,10,15,20-tetraphenylporphyrin, DABCO: 1,4-diazabi-cyclo[2.2.2]octane) in 2:1 molar ratio. A cyclic Zn porphyrin dimer (ZnCP) was also used as the host molecule for the Ru porphyrin. In the latter, the Ru-DABCO bonding in RuTPP(DABCO)₂ was stabilized by the host-guest complexation. Reaction progress kinetic analysis of the ligand substitution reaction of RuTPP(DABCO)₂ and that in ZnCP revealed the stabilization mechanism of the Ru-DABCO bonding. Photoinduced electron transfer (PET) from the Zn porphyrin to the Ru porphyrin was observed in the porphyrin array. The host-guest stabilization of unstable complex for construction of a donor-accepter-donor structure is expected to be a new method for an artificial photosynthesis.
      PubDate: 2017-05-22T08:20:29.819223-05:
      DOI: 10.1002/asia.201700738
       
  • Understanding the Mechanisms of Gold Shell Growth onto Polymer
           Microcapsules to Control Shell Thickness
    • Authors: Alison Louise Tasker; James Hitchcock, Elaine Alice Baxter, Olivier Cayre, Simon Biggs
      Abstract: Polymer microcapsules have been used commercially for decades, however they have an inherent flaw which renders them impractical as a carrier of small, volatile molecules. The porous nature of the polymer shell allows for diffusion of the encapsulated molecules into the bulk. The use of metal shells is an innovative way to prevent undesired loss of small molecules from the core of microcapsules, however it is important, particularly when using expensive metals to ensure that the resulting shell is as thin as possible. Here we investigate the fundamental mechanisms controlling the gold shell thickness when a fragrance oil is encapsulated in a poly(methyl methacrylate) shell. We consider the distribution of the nanoparticles on the capsule surface, and from quantification of the adsorbed NP density and resulting shell thickness, we propose mechanisms to describe the gold shell growth for systems with high and low NP surface coverage. We suggest from our observations that the gold grows to fill in the gaps between NPs. At low NP concentrations, thicker metal shells form. We postulate that this is due to the low NP density on the surface, forcing the gold clusters to grow larger before they meet the adjacent ones. Thus, to grow the thinnest possible shells a densely packed monolayer of platinum nanoparticles is required on the capsule surface.
      PubDate: 2017-05-21T21:20:30.825728-05:
      DOI: 10.1002/asia.201700536
       
  • Catalytic Systems for the Cross-Linking of Organosilicon Polymers
    • Authors: Dengxu Wang; Johann Klein, Esteban Mejía
      Abstract: Silicone rubbers are so widespread in our daily lives that we take their presence for granted. But, how are the fine threads of polydimethylsiloxane (PDMS) woven into sturdy silicone rubbers' Depending on the desired material properties, organosilicon polymers can be cross-linked through most diverse mechanisms, from the “classic” radical-based methods to the modern metal-free or enzymatic approaches, always based on catalysis. These technologies, even the older ones, are still subject of intense research and inspiration for the development of fascinating new catalytic methodologies and materials. More information can be found in the Focus Review by Esteban Mejía et al. (
      DOI : 10.1002/asia.201700304).
      PubDate: 2017-05-19T07:10:47.220419-05:
       
  • Sequential Functionalization of a Natural Crosslinker Leads to Designer
           Silicone Networks
    • Authors: Scott E. Laengert; Alyssa F. Schneider, Eric Lovinger, Yang Chen, Michael A. Brook
      Abstract: The three different functional groups of eugenol, a natural aromatic crosslinker, are sequentially and selectively linked in high yield to commercial HSi-terminated silicone polymers using the Piers–Rubinsztajn and hydrosilylation reactions in any order. The physical properties of the resulting networks – exemplified by the spider's web – are readily tuned by changing molecular weights and the backbone constituents of the silicone chains. More information can be found in the Communication by Michael A. Brook et al. (
      DOI : 10.1002/asia.201700160).
      PubDate: 2017-05-19T07:10:26.309549-05:
       
  • Dihydrogen Splitting Using Dialkylsilylene-Based Frustrated Lewis Pairs
    • Authors: Zhaowen Dong; Zhifang Li, Xupeng Liu, Chenting Yan, Ningka Wei, Mitsuo Kira, Thomas Müller
      Abstract: An isolable dialkylsilylene reacts with dihydrogen in the presence of a small amount of a conventional Lewis acid (BPh3, BEt3) or a base (PPh3, PEt3, NPh3, NEt3) at low temperatures in a hydrocarbon solvent, giving the corresponding dihydrosilane in high yields. Both the silylene/Lewis acid and silylene/Lewis base pairs work as a frustrated Lewis pair (FLP) to split dihydrogen, being in accord with the amphoteric nature of the silylene. More information can be found in the Communication by Zhaowen Dong, Zhifang Li, Mitsuo Kira, Thomas Müller et al. (
      DOI : 10.1002/asia.201700143).
      PubDate: 2017-05-19T07:10:24.271094-05:
       
  • Lewis Base-Mediated Silylations of Alcohols: Asymmetric Synthesis of
           Chiral Organosilicon Compounds Controlled by Chiral Ar-BINMOLs
    • Authors: Li-Wen Xu
      Abstract: In the past years, successful stereoselective functionalizations of hydroxyl groups of alcohol substrates with chlorosilanes have evolved silyl ether formation from a functional group protection to an enantioselective synthetic strategy. In this work, a family of structurally specific chiral diols, chiral 1,1'-binaphthalene-2--arylmethanol-2'-ol (Ar-BINMOL), -controlled desymmetrization of dichlorosilanes is presented, which led to the facile construction of desired silicon-stereogenic organosilicon compounds with high yields and good diastereoselectivities. IN addition, the enantioselective silylation of Ar-BINMOLs or Ar-BINMOL-derived phosphines might not only be of interest for the development of highly stereoselective nucleophilic silylation, but also bring light into the construction of novel chiral phosphine ligands bearing an atropisomeric silicon-stereogenic siloxane as silicon-based bulky group.
      PubDate: 2017-05-18T20:45:49.429655-05:
      DOI: 10.1002/asia.201700640
       
  • On-demand Antimicrobial Treatment with Antibiotic-Loaded Porous Silicon
           Capped with a pH-Responsive Dual Plasma Polymer Barrier
    • Authors: Roshan Bharath Vasani; Endre J Szili, Gayathri Rajeev, Nicolas Hans Voelcker
      Abstract: Chronic wounds are a major socio-economic problem. Bacterial infections in such wounds are a major contributor to lack of wound healing. An early indicator of wound infection is an increase in pH of the wound fluid. Herein, we describe the development of a pH-responsive drug delivery device that can potentially be used for wound decontamination in situ and on-demand in response to an increase in the pH of the wound environment. The device is based on a porous silicon film that provides a reservoir for encapsulation of an antibiotic within the pores. Loaded porous silicon is capped with dual plasma polymer layers of poly(1,7-octadiene) and poly(acrylic acid), which provide a pH-responsive barrier for on-demand release of the antibiotic. We demonstrate that release of the antibiotic is inhibited in aqueous buffer at pH 5, whereas the drug is released in a sustainable manner at pH 8. Importantly, the released drug was bacteriostatic against the Pseudomonas aeruginosa wound pathogen. In the future, incorporation of the delivery device into wound dressings could potentially be utilized for non-invasive decontamination of wounds.
      PubDate: 2017-05-16T03:40:33.308266-05:
      DOI: 10.1002/asia.201700427
       
  • Graphene Oxide Conjugated Magnetic Beads for RNA Extraction
    • Authors: Xuan-Hung Pham; Ahruem Baek, Tae Han Kim, Sang Hun Lee, Won-Yeop Rho, Woo-Jae Chung, Dong-Eun Kim, Bong-Hyun Jun
      Abstract: A magnetic material that consists of silica-coated magnetic beads conjugated with graphene oxide (GO) was successfully prepared for facile ribonucleic acid (RNA) extraction. When the GO-modified magnetic beads were applied to separate the RNA from the lysed cell, the cellular RNAs were readily adsorbed to and readily desorbed from the surface of the GO-modified magnetic beads by urea. The amount of RNA extracted by the GO-modified magnetic beads was ~170% as much as those of the control extracted by a conventional phenol-based chaotropic solution. These results demonstrate that the facile method of RNA separation by using GO-modified magnetic beads as an adsorbent is an efficient and simple way to purify intact cellular RNAs and/or microRNA from cell lysates.
      PubDate: 2017-05-16T01:50:33.194459-05:
      DOI: 10.1002/asia.201700554
       
  • Dual-fluorophore raspberry-like nanohybrids for ratiometric pH sensing
    • Authors: Isaac Acquah; Jinkyu Roh, Dong June Ahn
      Abstract: We report on the development of raspberry-like silica structures formed by the adsorption of 8-hydroxypyrene-1,3,6-trisulfonate (HPTS)@silica nanoparticles (NPs) on rhodamine B isothiocyanate (RBTIC)@silica NPs for ratiometric fluorescence-based pH sensing. To overcome the well-known problem of dye leaching which occurs during encapsulation of anionic HPTS dye in silica NPs, we utilized a polyelectrolyte-assisted incorporation of the anionic HPTS. The morphological and optical characterization of the as-synthesized dye-doped NPs and the resulting nanohybrids were carried out. The pH-sensitive dye, HPTS, incorporated in the HPTS-doped silica NPs provided a pH-dependent fluorescence response while the RBITC-doped silica provided the reference signal for ratiometric sensing. We evaluated the effectiveness of the nanohybrids for pH sensing; the ratio of the fluorescence emission intensity at 510 nm and 583 nm at excitation wavelengths of 454 nm and 555 nm respectively. The results showed a dynamic response in the acidic pH range. With this approach, nanohybrids containing different dyes or receptors could be developed for multifunctioning and multiplexing applications.
      PubDate: 2017-05-14T23:21:10.024294-05:
      DOI: 10.1002/asia.201700616
       
  • Pyrazole[4,3-h]quinoline ligand based iridium(III) complexes for
           electrochemiluminescence
    • Authors: Luisa De Cola; Chien-Wei Hsu, Elena Longhi, Stephan Sinn, Chris Hawes Hawes, David Young, Paul Kruger
      Abstract: Electrochemiluminescence (ECL) based on [Ru(bpy)3]2+ systems is widely utilized for immunoassays. In order to extend the promising potential of ECL based applications, Ir(III) complexes have recently attracted attention as probes because of their excellent luminescent properties and tunable emission wavelength. Here we describe a series of Ir complexes using a large π-conjugated ligand and different ancillary chelates. The complexes synthesized have been chemically and spectroscopically characterized and used for ECL measurements with annihilation and co-reactant methods. One of the Ir(III) complexes investigated exhibits the brightest, ever reported, ECL efficiency in acetonitrile employing benzoyl peroxide (BPO) co-reactant method.
      PubDate: 2017-05-14T21:25:34.115706-05:
      DOI: 10.1002/asia.201700556
       
  • Selective Separation of Aliphatic Nitriles Employing a Two-Dimensional
           Interdigitated Coordination Polymer
    • Authors: Srinivasan Natarajan; R Hota, S Mistry
      Abstract: A room temperature slow diffusion reaction of the metal nitrates [M = Zn(II) and Co(II)] with 5-azido isopthalic acid (AIPA) and 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene (BPDB) resulted a new two dimensional interdigitated coordination polymer, [M(C8H3N3O4)(C12H10N4)].DMF [DMF = dimethyl formamide (C3H7NO)]. The non bonded DMF molecules, was found to exchange through a single-crystal to single-crystal (SCSC) fashion with many aliphatic nitrile compounds. More importantly, the present compound, I.DMF(Zn) appears to absorb cis-crotononitrile selectively from the cis-trans mixture as well as a mixture containing the structural isomer (allylnitrile). It also preferentially absorbs propionitrile from an equimolar mixture of acetonitrile, propionitrile and butyronitrile (1:2:1). The cobalt compound exhibits anti-ferromagnetic behavior.
      PubDate: 2017-05-12T06:10:53.458284-05:
      DOI: 10.1002/asia.201700485
       
  • Inverse Electron-Demand Diels-Alder Reactions: Principles and Applications
    • Authors: Jianwei Xu; Zhuang Mao Png Png, Huining Zeng Zeng, Qun Ye
      Abstract: Inverse electron-demand Diels-Alder reaction (iEDDA) represents an intriguing class of cycloaddition reaction that has attracted increasing attention for its applications in bioorthogonal chemistry, total synthesis of natural products, and materials science. In many cases, the application of iEDDA has been demonstrated as an innovative approach to achieve the target structures. The theoretical aspects of this class of reactions are of particular interest for scientists to understand various factors, such as steric strain and electron density of the attached groups, to govern the reaction and thus to elucidate the reaction mechanism. This review aims to summarize both the theoretical investigations and the application-driven research work of iEDDA. First of all, the historical aspects and the theoretical basis of the reaction, especially the recent advances on time-dependent density functional theory (TD-DFT) calculations as well as catalysis strategies will be highlighted and discussed. Secondly, the applications of this novel reaction in the context of materials science, bioorthogonal chemistry and total synthesis of natural products will be elaborated with selected recent examples. The challenges and opportunities of iEDDA will be highlighted to render more insights for its potential applications in many other research areas.
      PubDate: 2017-05-12T02:16:36.673353-05:
      DOI: 10.1002/asia.201700442
       
  • Multi-functional free-standing gel polymer electrolyte with carbon
           nanofibre interlayers for high performance lithium-sulfur batteries
    • Authors: Sinho Choi; Jianjun Song, Chengyin Wang, Soojin Park, Guoxiu Wang
      Abstract: Free-standing trimethylolpropane ethoxylate triacrylate gel polymer electrolyte is synthesized by a chemical cross-linking process and used as an electrolyte and separator membrane in lithium-sulfur batteris. The cross linked gel polymer electrolyte also exhibited a stable geometric size retention of 95% at the high temperature of 130 oC. The as-prepared gel polymer electrolyte membrane with carbon nanofibers interlayer can effectively prevent polysulfide dissolution and shuttle effect, leading to significantly enhanced electrochemical properties including high capacity and cycling stability with an enhanced specific capacity of 790 mAh g-1 after 100 cycles.
      PubDate: 2017-05-12T02:15:46.215543-05:
      DOI: 10.1002/asia.201700402
       
  • Single-walled Carbon Nanotube Based Ultrafast High Capacity Al-ion Battery
    • Authors: Preeti Bhauriyal; Arup Mahata, Biswarup Pathak
      Abstract: Exploring a suitable electrode material is a fundamental step in the direction of the development of Al-ion battery for enhanced performance. In this work, we have explored the feasibility of single-walled carbon nanotubes (SWNTs) as a cathode material for Al-ion batteries using the density functional theory calculations. Carbon nanotubes with the hollow structures and large surface area overcome the difficulty of activating the opening of interlayer spaces as observed in graphite electrode during the first intercalation cycle. Our results show that AlCl4 binds strongly with the SWNT resulting into energetically and thermally stable AlCl4 adsorbed SWNT system. The diffusion calculation shows that the SWNT system allows ultrafast diffusion of AlCl4 with a more favourable inner surface diffusion over outer surface diffusion. Our charge density difference and Bader atomic charge analysis confirm the oxidation of SWNT on AlCl4 adsorption, showing a similar behaviour like previously studied graphite cathode. The average open-circuit voltage and AlCl4 storage capacity increases with increasing SWNT diameter and can be as high as 1.96 V and 275 mAh/g, respectively in (25,25) SWNT compared to graphite (70 mAh/g). All of these properties show that SWNTs are potential cathode material for high-performance Al-ion batteries and should be explored further.
      PubDate: 2017-05-11T06:55:43.566348-05:
      DOI: 10.1002/asia.201700570
       
  • Thiomaleimide functionalization for selective biological fluorescence
           detection of peroxynitrite as tested in HeLa and RAW 264.7 cells
    • Authors: Tesla Yudhistira; Sandip V. Mulay, Kyungjin Lee, Youngsam Kim, Hee-Sung Park, David G. Churchill
      Abstract: Abstract: The role of fluorescent molecules in diagnosis, treatments as well as in biomedical research has great current medicinal significance; related research continues to reveal new practical systems with enhanced features for interfacing of substituted molecules with biological systems. As part of an effort to better understand chalcogenide systems, a new dithiomaleimide BODIPY (BDP-NGM) probe has been designed, synthesized and characterized. The fluorescence of BDP-NGM was quenched by the incorporation of [3,4-bis(phenylthio)] on the maleimide-4-phenyl moiety which is in turn placed at the meso-position of the BODIPY system. The probe shows a "turn-ON" fluorescence response upon reaction with ONOO−; mass spec evidence reveals evidence for oxidation of the sulfur groups to sulfone groups. A ~18.0-fold emission intensity enhancement was found, compared with emission signal from other ROS/RNS; superoxide however gave a modest turn on signal (~5.0-fold). The reaction was completed within 10 min judging from the monitoring of the turn-ON fluorescence process; the detection limit was found to be 100 nM. BDP-NGM can be used for the detection of ONOO− under both acidic and basic conditions. Live cell imaging showed that the current probe can be used for the selective detection of ONOO− in living systems.
      PubDate: 2017-05-11T03:56:36.1191-05:00
      DOI: 10.1002/asia.201700527
       
  • Nitrogen-Doped Graphitic Porous Carbons Derived from in Situ Formed g-C3N4
           Templates for Oxygen Reduction Reaction
    • Authors: Feng Yan; Qi Li, Dan Xu, Xu Ou
      Abstract: Heteroatom-doped carbon materials have been considered as substitutes of Pt-based electrocatalysts for oxygen reduction reaction (ORR) in alkaline fuel cells. Here, we reported the synthesis of oxygen-containing nitrogen-doped carbon (ONC) nanosheets via the carbonization of a mixture containing glucose and dicyandiamide (DCDA). In situ formed graphitic carbon nitride (g-C3N4) derived from DCDA provides a nitrogen-rich template, facilitating the formation of ONC nanosheets. The resultant ONC materials with high nitrogen contents, high specific surface areas, and mesoporous total volume displayed the excellent electrochemical performances, including a similar ORR onset potential, half-potential, a higher diffusion-limited current and excellent tolerance to methanol than that of the commercial Pt/C catalyst, respectively. Moreover, the ONC-850 remained high long-term durability even after 1000 cycles, as well as the high electron transfer number of 3.92 (4.0 for Pt/C). Additionally, this work provides a deep insights and versatile strategy for the synthesis of cost-effective 2D N-doped carbon electrocatalysts.
      PubDate: 2017-05-11T02:55:36.086608-05:
      DOI: 10.1002/asia.201700586
       
  • Current Advances in Highly-multiplexed Antibody-based Single-cell
           Proteomic Measurements
    • Authors: Lu Huang; Sean Alan Michael, Yangfan Chen, Hongkai Wu
      Abstract: Single cell measurements have played a critical role in revealing the complex signaling dynamics and heterogeneity present in cells but there is still much to learn. Measuring samples from bulk populations of cells often masks information and dynamics present in subsets of cells. Common single cell protein studies rely on fluorescent microscopy and flow cytometry but are limited in multiplexing ability due to spectral overlap. Recently, technology advancements in single cell proteomics have allowed highly multiplexed measurement of multiple parameters simultaneously using barcoded microfluidic enzyme-linked immunosorbent assays (ELISA) and mass cytometry techniques. In this review, we will describe recent work around multi-parameter single cell protein measurements and critically analyze the techniques.
      PubDate: 2017-05-11T01:55:52.213714-05:
      DOI: 10.1002/asia.201700404
       
  • Janus Copper Mesh Film with Water Unidirectional Transportation Ability
           toward High Efficiency Oil/Water Separation
    • Authors: Zhongjun Cheng; Bohan Wang, Hua Lai, Pengchang Liu, Dongjie Zhang, Da Tian, Hongwei Liu, Xiaoyan Yu, Bo Sun, Kening Sun
      Abstract: Inspired by the special asymmetric wettability and controllable permeating function of cell membrane, we reported a Janus nanostructured copper mesh film with unidirectional water transportation ability, on which, water can permeate from the hydrophobic side to the hydrophilic side, while it be retained from the opposite direction. Noticeably, based on the special unidirectional water permeation property, both heavy oil/water mixtures (ρoil> ρwater) and light oil/water mixtures (ρoil < ρwater) can be separated. Meanwhile, the film demonstrates high separating efficiency and good recyclability. This paper reports a new Janus film to realize the high efficient oil/water separation, given the smart controllability in wettability of the film, it is believed to potentially be used in many practical applications, such as wastewater treatment and oil spill clean-up.
      PubDate: 2017-05-10T09:00:35.961673-05:
      DOI: 10.1002/asia.201700488
       
  • Low band gap donor - acceptor conjugated systems based on 3-alkoxy or
           3-pyrrolidino - 4-cyanothiophene and benzothiadiazole units
    • Authors: Gurunathan Savitha; Chady Moussallem, Magali Allain, Frédéric Gohier, Pierre Frère
      Abstract: 3-hexyloxy-4-cyanothiophene, 3-pyrrolidino-4-cyanothiophene and 3,4-ethylenedioxythiophene (EDOT) units are used with benzothiadiazole as building blocks for developing three new conjugated Donor-Acceptor-Donor derivatives. The DAD molecules have in common the central acceptor part formed by combining the electron-withdrawing cyano groups and benzothiadiazole moiety. Theoretical calculations and the UV-vis and electrochemical data reveal the key role of the end capped donor to tune the electronic properties of the derivatives. The study of the electropolymerization process of the three derivatives show the strong influence of the donor parts both on the reactivity of the precursors and on the electronic properties of the resulting polymers. Derivatives end capped with pyyrolidinocyano thiophene or EDOT units lead to film of polymers presenting low band gap around 0.9 - 1.4 eV. Upon oxidation, the two polymers present well different behaviors. In presence of the pyrrolidino-cyanothiophene moieties, the oxidation leads to a blue shift of the absorption bands while with EDOT units, classical red shift giving high absorption in the NIR region was observed for the oxidized states.
      PubDate: 2017-05-09T20:55:28.327547-05:
      DOI: 10.1002/asia.201700545
       
  • A Tunable Cyclic Container: Guest-Induced Conformational Switching,
           Efficient Guest Exchange and Selective Isolation of C70 from Fullerene
           Mixture
    • Authors: Sankar Prasad Rath; Pritam Mondal
      Abstract: An adaptable cyclic porphyrin dimer with highly flexible linkers has been utilized as an artificial molecular container, which can efficiently encapsulate various aromatic guests (TCNQ/C60/C70) through strong π-π interaction by adjusting its cavity size and conformation. Also, the planar aromatic guest (TCNQ) can be easily exchanged by the larger aromatic guests (C60/C70) selectively. During the guest exchange process, the two porphyrin rings switch their relative orientation according to the size and shape of the guests. Such behaviors of the cyclic container have been thoroughly investigated using UV-visible, NMR, and X-ray crystal structure determination of the host-guest assemblies. The electrochemical and photophysical studies demonstrate an occurrence of photoinduced electron transfer from bisporphyrin to TCNQ/C60/C70 in the respective host-guest assemblies. The cyclic host can form complexes with C60 and C70 with association constants of 2.8±0.2×105 and 1.9±0.3×108 M-1, respectively, which represents the highest binding affinities for C70 reported so far for the zinc(II) bisporphyrinic receptors. Such a high selectivity in binding C70 over C60 further allows easy extraction and efficient isolation of C70 from a C60/C70 fullerene mixture. Experimental evidences are substantiated by DFT calculations.
      PubDate: 2017-05-09T14:50:27.04512-05:0
      DOI: 10.1002/asia.201700600
       
  • Porphyrin Bound to i-motifs: Intercalation versus External Groove Binding
    • Authors: Tingxiao Qin; Kunhui Liu, Di Song, Chunfan Yang, Hongmei Su
      Abstract: G-rich and C-rich DNA can fold into the tetrastranded helical structures G-quadruplex or C-quadruplex (i-motif) that are considered as specific drug targets for cancer therapy. A large number of small molecules (the so-called ligands), which could bind and modulate the stability of G-quadruplexes structures, have been widely examined. Hitherto, much less is known for the ligand binding interactions with the relatively young C-quadruplex (i-motif). Here by combining steady-state measurements (UV-vis, fluorescence, and ICD) with time-resolved laser flash photolysis spectroscopy, we study the binding interactions of cationic porphyrin (TMPyP4) with i-motifs (C₃TA₂)₃C₃T and (C₄A₄C₄)2. The intercalation binding mode via π-π stacking of porphyrin macrocyle and the C:C+ hemiprotonated base-pair has been identified for the first time. The coexisted binding modes of intercalation (~80%) versus external major groove binding (~20%) are determined quantitatively, allowing a full picture understanding of the porphyrin/i-motif interactions. Ionic strength is found to play important roles affecting the binding modes, with the progressive increase of the ionic strength resulting in gradual decrease of the intercalation percentage and increase of groove binding percentage. Further, extended study for the porphyrin derivative with four bulky side arm substituents (T4), suggests a complete prohibition of the intercalation mode due to large steric hindrance, and thus providing a novel groove-binding ligand with site selectivity. These results provide in-depth mechanistic insights for understanding the ligand interactions with i-motifs and guidance for related applications in anticancer drug design.
      PubDate: 2017-05-09T01:21:18.26702-05:0
      DOI: 10.1002/asia.201700398
       
  • Synthesis of substituted 2-amino-1,3-oxazoles via copper-catalyzed
           oxidative cyclization of enamines and N, N-dialkyl formamides
    • Authors: Peng Gao; Juan Wang, Zijing Bai, Desuo Yang, Ming-Jin Fan, Zheng-Hui Guan
      Abstract: A facile synthesis of 2-amino-1,3-oxazoles via CuI-catalyzed oxidative cyclization of enamines and N,N-dialkyl formamides has been developed. The reaction proceeds through an oxidative C-N bond formation, followed by an intramolecular C(sp2)-H bond functionalization/C-O cyclization in one-pot. This protocol provides a direct access to useful 2-amino-1,3-oxazoles and features protecting group free nitrogen sources, readily available starting materials, broad substrate scope and mild reaction conditions.
      PubDate: 2017-05-09T01:20:42.12867-05:0
      DOI: 10.1002/asia.201700503
       
  • A Facile Construction of Quinoline-2-carboxylate Esters through An Aerobic
           Oxidation of Alkyl 4-Anilinocrotonates Induced by Radical Cation Salt
    • Authors: Xiao Dong Jia; Pengfei Li, Yu Shao, Yu Yuan, Wentao Hou, Xiaofei Liu, Xuewen Zhang, Honghe Ji
      Abstract: A facile construction of quinoline-2-carboxylate esters through an aerobic oxidation of alkyl 4-anilinocrotonates was described. In the presence of dioxygen, sp3 C-H bonds in 4-anilinocrotonates can easily be oxidized by catalytic radical cation salt, providing a radical intermediate. After further oxidation and domino cyclization, the desired quinoline derivatives were afforded in high yields. This reaction provided a new way to construct the pharmaceutically relevant quinoline skeleton, avoiding harsh reaction conditions and tedious starting material synthesis.
      PubDate: 2017-05-08T21:26:05.487284-05:
      DOI: 10.1002/asia.201700560
       
  • Mechanism of Nickel-catalysed Suzuki-Miyaura coupling of amides
    • Authors: Xu Zhengyang; Haizhu Yu, Fu Yao
      Abstract: Ni-catalyzed Suzuki-Miyaura coupling of N-tert-butoxycarbonyl (N-Boc) protected amides provides a versatile strategy for the construction of C-C bonds. Herein, density functional theory (DFT) methods have been used to elucidate the mechanistic details, and especially the necessity of N-Boc, K3PO4 and H2O in this reaction. Our study corroborates the previous proposal that the overall catalytic cycle includes three steps: oxidative addition, transmetalation, and reductive elimination. Three possible transmetalation mechanisms are examined to interpret the effect of K3PO4 and H2O. In the most feasible transmetalation mechanism, K3PO4 (acting as a Lewis base) first ligates with the Lewis acid PhBpin. The formed K3PO4-PhBpin complex readily undergoes the H transfer step with H2O. Throughout the catalytic cycle, the H transfer in the transmetalation step is the rate-determining step. The theoretical results show good agreement with the experimental data.
      PubDate: 2017-05-08T10:25:42.975578-05:
      DOI: 10.1002/asia.201700313
       
  • Core-shell-structured dendritic mesoporous silica nanoparticles for
           combined photodynamic therapy and antibody delivery
    • Authors: Chengzhong Yu; Prasanna Lakshmi Abbaraju, Yannan Yang, Meihua Yu, Jianye Fu, Chun Xu
      Abstract: Multifunctional core-shell-structured dendritic mesoporous silica nanoparticles with a fullerene doped silica core and a dendritic silica shell with large pores have been prepared. The combination of photodynamic therapy and antibody therapeutics significantly inhibits the cancer cell growth by effectively reducing the level of anti-apoptotic proteins.
      PubDate: 2017-05-08T08:20:43.94805-05:0
      DOI: 10.1002/asia.201700392
       
  • Supported C-scorpionate vanadium (IV) complexes as reusable catalysts for
           xylene oxidation
    • Authors: Jiawei Wang; Luisa Martins, Ana P. C. Ribeiro, Sónia A. C. Carabineiro, José L. Figueiredo, Armando J. L. Pombeiro
      Abstract: C-scorpionate vanadium(IV) [VOxCl3-x{κ3-RC(pz)3}] [pz = pyrazol-1-yl; x = 0, R = SO3 (1); x = 1, R = CH2OH (2) or CH2OSO2Me (3)] complexes supported on functionalized carbon nanotubes (CNT) are the first V-scorpionate catalysts used so far for the neat oxidation of o-, m- or p-xylene, with TBHP (70% aqueous solution), to the corresponding toluic acids (main products), tolualdehydes and methylbenzyl alcohols. Remarkably, a p-toluic acid yield of 43% (73% selectivity, TON = 1.34 × 103) was obtained with 2@CNT in a simple microwave-assisted mild oxidation procedure, using a very low catalyst charge (3.2 × 10-2 mol% vs. substrate). Further, this occurred in the absence of any bromine source, what is significant towards the development of a greener and more sustainable process for xylenes oxidation. Moreover, catalysts reuse with preservation of their activity was found for up to six consecutive cycles. The effects of reaction parameters, such as reaction time, temperature, amount of catalyst or type of heating source, on the performance of the above catalytic systems are reported and discussed.
      PubDate: 2017-05-06T06:23:26.076716-05:
      DOI: 10.1002/asia.201700499
       
  • Two-Dimensional Crystallization of Rylene Diimide Based n-Type
           Semiconductors Tuned by the Dimensions of the Aromatic Core at the
           Liquid–Solid Interface
    • Authors: Zongxia Guo; Ping Yu, Kai Sun, Wenpin Wang, Yuhan Wei, Zhibo Li
      Abstract: Size of destiny! 2D crystallization of rylene diimide-based n-type semiconductors was explored at the liquid/HOPG interface by means of scanning tunneling microscopy (STM). It was found that the dimension size of the aromatic core affects the surface assembly behaviors of such n-type semiconductors. The 2D patterns and the surface chirality can also be tuned by solvent nature. In addition, the long-range ordered properties of the monolayers can be adjusted by changing the molecular symmetry. More information can be found in the Full Paper by Zongxia Guo, Zhibo Li et al. (
      DOI : 10.1002/asia.201700271).
      PubDate: 2017-05-05T06:43:36.659136-05:
       
  • Asymmetric Total Syntheses of (−)-α-Lycorane, (−)-Zephyranthine and
           Formal Synthesis of (+)-Clivonine
    • Authors: Xing-Wen Sun; Yong-Jian Chen, Sen-Lin Cai, Chuan-Chuan Wang, Jin-Duo Cheng, Søren Kramer
      Abstract: We report the successful achievement of an asymmetric route to (−)-α-lycorane and (−)-zephyranthine as well as a formal total synthesis of (+)-clivonine. A pivotal intermediate, which serves as a potent precursor for the divergent syntheses of these natural products, was accessed by a diastereoselective Pd-catalyzed cinnamylation of an N-tert-butanesulfinyl imine.
      PubDate: 2017-05-04T23:15:32.301566-05:
      DOI: 10.1002/asia.201700555
       
  • CO2 Assisted Activating Cellulose for Preparation of Superhydrophobic
           Nanocoating
    • Authors: Jinfang Wang; Zhimin Xue, Tingting Yu, Zhimin Liu, Tiancheng Mu
      Abstract: There is increasing demand for superhydrophobic materials which could be used for separating oil and water efficiently. In order to avoid secondary pollution, it is desirable to prepare such materials with green technology. Here we present an environment benign method for fabricating superhydrophobic materials by using organic base based solvents in which cellulose can be dissolved and activated. Then dissolved cellulose could be chemical modified with green silanization reagent, and the solvent can be recycled after CO2 is removed. The obtained cellulose nanocoating exhibited excellent hydrophobic effect. Spray it on the filter paper (water contact angle (WCA) is 165°) for oil and water separation, the separation efficiency is more than 95%; spray it on ordinary sponge (WCA is 163°), it can be used as oil absorber. It can also absorb a certain amount of bisphenol A (BPA) (the concentration decreased by 66% from the origin concentration 0.1 mM). Besides the high efficiency for the separation of oil and water, it is resistant to a wide range of pH solutions, which means that it could be used in harsh environments. More importantly, the process is cost-effective, the solvent can be recycled and the whole process is green. Thus the activation method provides a green route for the preparation of other cellulose-based materials.
      PubDate: 2017-05-04T08:15:48.02596-05:0
      DOI: 10.1002/asia.201700335
       
  • The development of G-quadruplex-based assays for the detection of small
           molecules and toxic substances
    • Authors: Dik-Lung Ma; Chung-Hang Leung
      Abstract: G-quadruplexes can be induced to form from guanine-rich (G-rich) DNA sequences by certain small molecules or metal ions. In concert with an appropriate signal transducer, such as a fluorescent dye or a phosphorescent metal complex, the ligand recognition event can be transduced into a luminescent response. This Focus Review is aimed to highlight the recent examples of aptamer-based or metal-mediated G-quadruplex assays for the detection of small molecules and toxic substances in the latest three years. We discuss the mechanisms and features of the different assays and present an outlook and perspective for the future of this field.
      PubDate: 2017-05-03T22:15:31.818301-05:
      DOI: 10.1002/asia.201700533
       
  • Nickel hydroxide supercapacitor with a theoretical capacitance and high
           rate capability based on hollow dendritic 3D-nickel current collectors
    • Authors: Ji-Hyun Jang; Sung-Wook Kim, Ik-Hee Kim, Sun-I Kim
      Abstract: We propose a straightforward way to realize the theoretical capacitance and high rate capability of nickel hydroxide supercapacitors, by utilizing a mesoporous hollow dendritic three-dimensional-nickel (3D-nkckel) current collector. A facile electrodeposition method employing a hydrogen bubble template is chosen for rapid fabrication of the dendritic 3D-nickel structure. After nickel hydroxide is deposited on the hollow 3D-nickel current collector, it exhibits a highest capacitance of 3,637 F/g at a current density of 1 A/g, and retains 97% of capacitance at a high current density of 100 A/g with great cycle stability of over 80% after 10,000 cycles. The enhanced performance can be attributed to the large surface area and high conductivity of the moss-like dendritic 3D-nickel current collector, which allows direct contact between the active materials and the current collector and reduced diffusion resistance between the surface of the active materials and the electrolyte. These results not only confirm a facile fabrication method for high-performance 3D-metal nanostructures, but also offer a promising solution for state-of-the-art energy storage systems.
      PubDate: 2017-05-03T07:50:22.551724-05:
      DOI: 10.1002/asia.201700454
       
  • Water Solubilization of Fullerene Derivatives by β-(1,3-1,6)-d-Glucan and
           Their Photodynamic Activities toward Macrophages
    • Authors: Atsushi Ikeda; Tatsuya Iizuka, Naotake Maekubo, Kazuyuki Nobusawa, Kouta Sugikawa, Kazuya Koumoto, Toshio Suzuki, Takeshi Nagasaki, Motofusa Akiyama
      Abstract: A fullerene derivative bearing a carboxylic acid was dissolved in water by formation of a globular structure, which looks like the bamboo work in the picture, using β-1,3-glucan as a solubilizing agent. The complex has a high photodynamic activity toward macrophages under visible-light irradiation, because the carboxylic acid moieties in the complex enhance the binding affinity with β-1,3-glucan-receptors on the macrophage surface. More information can be found in the Full Paper by Atsushi Ikeda et al. (
      DOI : 10.1002/asia.201700182.).
      PubDate: 2017-05-03T06:05:30.025502-05:
       
  • Arrangement of Proteinogenic α-Amino Acids on a Cyclic Peptide Comprising
           Alternate Biphenyl-Cored ζ-Amino Acids
    • Authors: Shohei Tashiro; Masayuki Chiba, Mitsuhiko Shionoya
      Abstract: A water-soluble cyclic hexapeptide comprising an alternate sequence of biphenyl-cored ζ-amino acids and proteinogenic α-amino acids such as l-leucine has been developed. The amino acids were connected by typical peptide synthesis, and the resultant linear hexapeptide was intramolecularly cyclized to form the target cyclic peptide. Theoretical and NMR spectroscopic analyses suggested that the cyclic peptide was folded into an unsymmetrical conformation, and the structure was likely to be flexible. Furthermore, the cyclic peptide became soluble in water by introducing three carboxylate groups. More information can be found in the Full Paper by Mitsuhiko Shionoya et al. (
      DOI : 10.1002/asia.201700203).
      PubDate: 2017-05-03T06:05:27.079991-05:
       
  • Metal oxide nanostructures generated from in-situ sacrifice of zinc in
           bimetallic textures as flexible Ni/Fe fast battery electrodes
    • Authors: Tianyi Huang; Zhifang Liu, Zitong Zhang, Bangqing Xiao, Yong Jin
      Abstract: An "in-situ sacrifice" process was devised in this work as a room-temperature, all-solution processed electrochemical method to synthesize nanostructured NiOx and FeOx directly on current collectors. After electrodepositing NiZn/FeZn bimetallic textures on copper net, zinc component is etched and the remnant nickel/iron are evolved into NiOx and FeOx by the "in-situ sacrifice" activation we proposed. As prepared electrodes exhibit high areal capacities of 0.47 mAh cm-2 and 0.32 mAh cm-2, respectively. By integrating NiOx as cathode, FeOx as anode and PVA/KOH gel as separator/solid-state electrolyte, the assembled quasi-solid-state flexible battery delivers a volumetric capacity of 6.91 mAh cm-3 at 5 mA cm-2, along with a maximum energy density of 7.40 mWh cm-3 under a power density of 0.27 W cm-3 and a maximum tested power density of 3.13 W cm-3 with a 2.17 mWh cm-3 energy density retention. Our room-temperature synthesis, which only consumes minute electricity, makes it a promising approach for large-scale production. We also emphasize the etching zinc in-situ sacrifice process used in this work as a general strategy for the growth of metal-based nanostructures for high performance battery materials.
      PubDate: 2017-05-03T01:20:39.98308-05:0
      DOI: 10.1002/asia.201700518
       
  • Efficient generation of lactic acid from glycerol over Ru-Zn-Cu(I)/HAP
           catalyst
    • Authors: Zhiwei Jiang; Zhanrong Zhang, Tianbing Wu, Pei Zhang, Jinliang Song, Chao Xie, Buxing Han
      Abstract: The biodiesel production process generates a significant amount of glycerol as a by-product. Its valorization has attracted worldwide attention in terms of improving the overall effectiveness and profitability of bio-diesel production. Herein, we report hydroxyapatite (HAP) supported Ru-Zn-Cu(I) (Ru-Zn-Cu(I)/HAP) as effective catalysts for the transformation of glycerol to lactic acid (LA).The catalysts were characterized by different techniques. The effects of catalyst composition, reaction time and temperature on conversion and the product distribution were investigated. It was revealed that Ru nanoparticles of less than 2 nm were dispersed uniformly on HAP. Cu(I) could effectively inhibit the cleavage of C-C bonds, leading to improved yields of LA. Under optimized conditions, the yield of LA could achieve 70.9% over Ru-Zn-Cu(I)/HAP. Furthermore, the catalyst could be reused at least four times without obvious loss of activity and selectivity.
      PubDate: 2017-05-02T11:21:13.943881-05:
      DOI: 10.1002/asia.201700412
       
  • Resistance Controllability in Alkynylgold(III) Complex- based Resistive
           Memory for Flash-type Storage Applications
    • Authors: Peng Wang; Yu Fang, Jun Jiang, Yujin Ji, Youyong Li, Junwei Zheng, Qingfeng Xu, Jian-Mei Lu
      Abstract: Due to the demands of state-of-the-art information technologies that are suitable for big data storage, the necessity for organic memory devices (OMDs) materials is highlighted. However, OMDs based on metal complexes are limited to only several types of transition metal complex systems bearing nitrogen-donor ligands. In this paper, we attempt to introduce novel alkynylgold(III) materials into memory devices with superior performance. In this respect, an alkynyl-containing coumarin gold (III) complex, (C19N5H11)Au-C≡C-C9H5O, has been synthesized and integrated into a sandwiched Al/[(C19N5H11)Au-C≡C-C9H5O]/ITO device. By precisely controlling the compliance current (Icc), the devices show different switching characteristics from Flash-type binary resistance switching (Icc ≤ 10-3 A) to WORM-type ternary resistance switching (Icc = 10-2 A). This work explores electrical gold(III) complex-based memories for potential use in organic electronics.
      PubDate: 2017-05-02T10:16:17.776603-05:
      DOI: 10.1002/asia.201700369
       
  • Lateral Extension of Benzodithiophene System: Construction of Heteroacenes
           Containing Various Chalcogens
    • Authors: Lei Zhang; Jichang Wei, Dong Meng, Zhaohui Wang
      Abstract: A series of novel linear acenes with five fused rings, which contain thiophene, selenophene, and tellurophene as the outmost rings, have been successfully synthesized from well-known benzodithiophene (BDT). It was found that the optical, electrochemical properties and crystal packing motifs could be modulated by changing heteroatoms in the outmost rings.
      PubDate: 2017-05-02T09:54:48.973814-05:
      DOI: 10.1002/asia.201700552
       
  • Enhanced fluorescence imaging and photodynamic cancer therapy using hollow
           mesoporous nanocontainer
    • Authors: Suk ho Hong; Hyunjin Kim, Yongdoo Choi
      Abstract: Here we show that "off-on" type of photodynamic therapy agents could be developed using hollow mesoporous silica nanoparticles (HMSNP), which can be used not only for enhancing delivery of photosensitizers to cancer cells but also for enabling switchable optical properties of the photosensitizers. Fluorescence and singlet oxygen generation of the photosensitizer-loaded HMSNP is turned off in its native state. In vitro cell studies showed that this HMSNP-based "off-on" agent may have potential utility in selective fluorescence detection and photodynamic therapy of cancers.
      PubDate: 2017-04-30T10:53:39.220393-05:
      DOI: 10.1002/asia.201700371
       
  • Establishing the True Structure of the Sorbicillinoid-derived Isolate
           Rezishanone C by Total Synthesis
    • Authors: Martin Banwell; Qiao Yan, Michelle L Coote, Richmond Lee, Anthony C Willis
      Abstract: The enantiomer, ent-4, of the true structure, 4, of the sorbicillinoid rezishanone C (sorbivinetone) has been synthesized from a homochiral cis-1,2-dihydrocatechol that is itself generated through the whole-cell biotransformation of toluene. These studies together with dispersion-corrected DFT calculations support the proposal that rezishanone C is an artefact of the isolation process and arises through a Diels-Alder reaction between ethyl vinyl ether and sorbicillinol (3).
      PubDate: 2017-04-28T23:37:38.569101-05:
      DOI: 10.1002/asia.201700456
       
  • Aggregation behaviour of non-ionic twinned amphiphiles and their
           application as biomedical nanocarriers
    • Authors: Abhishek K. Singh; Bala N. S. Thota, Boris Schade, Katharina Achazi, Abdullah Khan, Christoph Böttcher, Sunil K. Sharma, Rainer Haag
      Abstract: A new class of twinned amphiphiles was developed by conjugating a pair of hydrophilic head groups from mPEG chains (Mn: 350 or 1000) and a pair of hydrophobic segments from linear alkyl chains (C11 or C18) through a novel spacer synthesized from glycerol and p-hydroxybenzoic acid. The aggregation phenomena of the amphiphiles were proven by DLS and fluorescence experiments, whereas size and morphology of the aggregates were evaluated by cryo-TEM, the measurements proved the formation of globular, thread-like or rod-like micelles as well as planar double-layer assemblies, depending on the amphiphile's molecular structure. The applicability of these non-ionic amphiphilic systems as nanocarriers for hydrophobic guest molecules was demonstrated by encapsulating a hydrophobic dye, Nile red, and a hydrophobic drug, Nimodipine. The transport capacity results for both Nimodipine and Nile Red prove them as a promising candidate for drug delivery.
      PubDate: 2017-04-28T10:30:38.355246-05:
      DOI: 10.1002/asia.201700450
       
  • Silicon-substituted xanthene dyes and their unique photophysical
           properties for fluorescent probes
    • Authors: Takayuki Ikeno; Tetsuo Nagano, Kenjiro Hanaoka
      Abstract: Fluorescence imaging is a powerful technique for visualizing temporal and spatial changes of biological events in living samples by utilizing fluorescent probes whose properties are altered upon interaction with the target biomolecule. In the past few years, many fluorescent probes have been developed based on xanthene dyes in which the O atom at the 10-position is replaced with a Si atom, such as 2,7-N,N,N',N'-tetramethyl-9-dimethyl-10-hydro-9-silaanthracene (TMDHS), Si-rhodamines and TokyoMagentas. Interestingly, these fluorophores not only retain the advantages of the typical xanthene dyes, but also have a number of unique properties, including far-red to near-infrared emission. This review summarizes silicon-substituted xanthene dyes reported to date, along with their photophysical properties. We include examples of applications of probes utilizing these fluorophores, such as multi-color imaging and super-resolution live-cell microscopy.
      PubDate: 2017-04-28T03:21:03.131508-05:
      DOI: 10.1002/asia.201700385
       
  • Preparation, Structural Determination, and Characterization of Electronic
           Properties of [5,6]- and [6,6]-carbosilylated Sc3N@Ih-C80
    • Authors: Masahiro Kako; Takeshi Sugiura, Kyosuke Miyabe, Masanori Yasui, Michio Yamada, Yutaka Maeda, Jing-Dong Guo, Shigeru Nagase, Takeshi Akasaka
      Abstract: Photochemical carbosilylation of Sc3N@Ih-C80 with silirane 1 afforded two corresponding [5,6]-adducts 2 and 3, and a [6,6]-adduct 4. The structural and electronic properties of these products were characterized using spectroscopic, electrochemical, and theoretical methods. The structure of 2 was disclosed using single-crystal X-ray crystallographic analysis. Thermal isomerization of 3 to 2 was observed, whereas that of 2 to 3 proceeded less efficiently at 100 °C. Upon heating under the same conditions, 4 underwent facile decomposition to afford Sc3N@Ih-C80, or isomerized to small amounts of 2 and 3. The relative stabilities of 2, 3, and 4 were rationalized using theoretical calculations. In contrast, 2, 3, and 4 were found to be stable under the photolytic condition employed for the carbosilylation. The photochemical functionalization of Sc3N@Ih-C80 represents a convenient synthetic method to obtain thermally labile fullerene-based products.
      PubDate: 2017-04-28T00:20:39.481155-05:
      DOI: 10.1002/asia.201700506
       
  • Mechanistic Insights of Palladium-Catalyzed Silylation of Aryl Iodides
           with Hydrosilanes by DFT Study
    • Authors: Zheng Xu; Jin-Zhou Xu, Jin Zhang, Zhan-Jiang Zheng, Jian Cao, Yu-Ming Cui, Li-Wen Xu
      Abstract: The catalytic cycles of palladium-catalyzed silylation of aryl iodides initiated by oxidative addition of hydrosilane or aryl iodide via three different mechanisms, which are characterized by intermediates R3Si-PdII-H (Cycle A), Ar-PdII-I (Cycle B) and PdIV (Cycle C), have been explored by hybrid density functional theory (DFT) in details. Our calculations suggested that the chemical selectivity and reactivity of the reaction depend on the ligation state of catalyst and specific reaction conditions including feeding order of substrates, and the presence of base. For less bulky biligated catalyst, Cycle C is energetically favored over Cycle A, through which the silylation process is slightly favored over the reduction process. Interestingly, for bulky monoligated catalyst, Cycle B is energetically more favored over the general accepted Cycle A, in which the silylation channel is slightly disfavored in comparison to that of the reduction channel. Moreover, the inclusion of base in this channel allows the silylated product become dominant. These findings offer a good explanation for the complex experimental observations. Designing reaction process, which allow the oxidative addition of Pd0 catalyst to aryl iodide occurs prior to hydrosilane, was thus suggested to improve reactivity and chemoselectivity for silylated product by pushing the catalytic cycle proceeds via Cycle B (monoligated Pd0 catalyst) or Cycle C (biligated Pd0 catalyst) instead of Cycle A.
      PubDate: 2017-04-28T00:20:37.563285-05:
      DOI: 10.1002/asia.201700174
       
  • Template- and additive-free electrosynthesis and characterization of
           spherical gold nanoparticles on hydrophobic conducting
           polydimethylsiloxane
    • Authors: Saurav Kumar Guin; Peter Knittel, Sven Daboss, Anton Breusow, Christine Kranz
      Abstract: Carbon-doped poly(dimethylsiloxane) (C-PDMS) modified with gold nanoparticles (AuNPs) is a highly promising material for the development of flexible lab-on-chip biosensors. Here, we present an electrochemical method to prepare stabilizer-free AuNPs directly on hydrophobic conducting substrates like C-PDMS without physical or chemical pre-treatment of the C-PDMS substrate. Using a potentiostatic triple pulse strategy, spherical, non-stabilized AuNPs of diameter 78 ± 5 nm could be deposited within 5 s with very narrow size-dispersion on the hydrophobic C-PDMS substrate in the absence of any structure directing or stabilizing agent. The detailed investigation of the mechanism of electrochemical formation of gold seeds and their three-dimensional growth on the hydrophobic surface along with nanomechanical atomic force - scanning electrochemical microscopy (QNM-AFM-SECM) characterization as well as conductive AFM allowed developing this fast electrochemical strategy with control in the desired size and size-dispersion of AuNPs. A detailed electrochemical investigation using cyclic voltammetry, anodic differential pulse voltammetry, and electrochemical impedance spectroscopy was conducted to characterize the electrochemical behavior of uncapped AuNPs deposited on C-PDMS. The Fc+(MeOH)2/Fc(MeOH)2 redox reaction at AuNPs-C-PDMS showed an improved charge transfer coefficient and heterogeneous charge transfer rate constant compared to the bare C-PDMS substrate.
      PubDate: 2017-04-27T19:04:57.141656-05:
      DOI: 10.1002/asia.201700444
       
  • Self-assembly of Luminescent Lanthanide Mesocates as Efficient Catalysts
           for Transforming CO2 into Cyclic Carbonates
    • Authors: Qingxin Han; Li Wang, Zhaohua Shi, Cong Xu, Zhe Dong, Zuolin Mou, Weisheng Liu
      Abstract: Four di-nuclear lanthanide mesocates have been fabricated through a spontaneous self-assembly method, and the formation of these complexes was well studied by their absorption and emission spectra. These stable complexes also exhibit superior catalytic performance and excellent recyclability in catalyzing the coupling reaction between epoxides and CO2. Meanwhile the catalyst can be prepared large scale. Moreover, Yb-complex and Lu-complex can feature near-infrared and visible emission, respectively, the intensity and life time of which could be used to identify the catalysts. Thus, this new approach is ready for constructing promising lanthanide complexes as efficient catalysts and it identifies the possibility to better study a catalytic reaction with a luminescent catalyst.
      PubDate: 2017-04-25T12:20:30.945709-05:
      DOI: 10.1002/asia.201700418
       
  • Divergent Total Syntheses of (-)-Huperzine Q, (+)-Lycopladine B,
           (+)-Lycopladine C and (-)-4-epi-Lycopladine D
    • Authors: Xiaoguang Lei; Benke Hong, Dachao Hu, Jinbao Wu, Jing Zhang, Houhua Li
      Abstract: We report herein our synthetic efforts towards the divergent syntheses of (-)-huperzine Q (1), (+)-lycopladines B (2), C (3) and (-)-lycopladine D (4). The 10-step total synthesis of (-)-huperzine Q (1) and the first total syntheses of (+)-lycopladines B (2) and C (3) have been accomplished via a series of cascade reactions. Our approach features a Michael addition/aldol/intramolecular C-alkylation sequence to forge the 6/9 spirocycle ring followed by an ethylene-accelerated carbonyl-olefin metathesis to construct the common 6/5/9 ring system. Finally, a late-stage enamine bromofunctinalization enables us to access (-)-huperzine Q (1), (+)-lycopladines B (2), C (3) and a tandem C4-epimerization/retro-Claisen condensation furnished (-)-4-epi-lycopladine D (63).
      PubDate: 2017-04-25T07:21:14.822358-05:
      DOI: 10.1002/asia.201700364
       
  • K2ZnSn3Se8: A New Noncentrosymmetric Zinc Selenidostannate(IV) Featuring
           Interesting Covalently Bonded [ZnSn3Se8]2- Layer and Exhibiting Intriguing
           SHG Activity
    • Authors: Molin Zhou; Xingxing Jiang, Yi Yang, Yangwu Guo, Zheshuai Lin, Jiyong Yao, Yicheng Wu
      Abstract: A new noncentrosymmetric zinc selenidostannate (IV) K2ZnSn3Se8 was synthesized. It features interesting covalently bonded [ZnSn3Se8]2- layers with K+ cations filling in the interlayer voids. The phonon spectrum was calculated to clarify its structural stability. Based on the X-ray diffraction data along with the Raman spectrum, the major bonding features of the title compound were identified. According to the UV-vis-NIR spectroscopy, K2ZnSn3Se8 possesses a typical direct band gap of 2.10 eV, which is in good agreement with the band structure calculations. Moreover, our experimental measurements and detailed theoretical calculations reveal that K2ZnSn3Se8 is a new phase-matchable nonlinear optical material with a powder SHG signal about 0.6 times of that of AgGaS2.
      PubDate: 2017-04-24T01:23:53.685727-05:
      DOI: 10.1002/asia.201700426
       
  • Small Molecular Anion Recognition by a Shape-responsive Bowl-type
           Dodecavanadate
    • Authors: Sho Kuwajima; Yuji Kikukawa, Yoshihito Hayashi
      Abstract: A dodecavanadate, [V₁₂O₃₂]⁴¯, is an inorganic bowl-type host with a cavity entrance with a diameter of 4.4 Å in the optimized structure. The linear, bent, and trigonal planar anions, are tested as a guest anion and the formation of host-guest complexes, [V₁₂O₃₂(X)]⁵¯ (X = CN¯, OCN¯, NO₂¯, NO₃¯, HCO₂¯, and CH₃CO₂¯) were confirmed by X-ray crystallographic analyses and ⁵¹V NMR study. The degree of the distortion of the bowl from a regular bowl to an oval bowl depends on the shape of the guest anion, after host-guest complex formation. In ⁵¹V NMR spectroscopy, all the chemical shifts of the host-guest complexes are clearly shifted after the guest incorporation. The incorporation reaction rates for OCN¯, NO₂¯, HCO₂¯, and CH₃CO₂¯ are much larger than those of NO₃¯ and halides. The incorporated non-spherical molecular anions in the dodecavanadate host are easily dissociated or exchanged to other anions, while the spherical halides in the dodecavanadate host are preserved without dissociation even in the presence of the tested anions.
      PubDate: 2017-04-22T05:30:42.533474-05:
      DOI: 10.1002/asia.201700489
       
  • Vanadium(V)-induced Oxidative Cross-coupling of Various Boron and Silyl
           Enolates
    • Authors: Toru Amaya; Yuma Osafune, Yusuke Maegawa, Toshikazu Hirao
      Abstract: Intermolecular oxidative cross-coupling of two different enolates is one of the most useful reactions to synthesize unsymmetrical 1,4-dicarbonyl compounds. In this study, the oxovanadium(V)-induced intermolecular oxidative cross-coupling of enolates was achieved to give the corresponding unsymmetrical 1,4-dicarbonyl compounds, where combination of various boron and silyl enolates such as ketone-ester, ester-ketone, ester-ester, amide-ketone, and amide-ester enolates was adapted. These results clearly exhibit the versatility of the present oxidative cross-coupling protocol.
      PubDate: 2017-04-20T22:41:26.344497-05:
      DOI: 10.1002/asia.201700470
       
  • Nitrogenase Cofactor: Inspiration for model chemistry
    • Authors: Ivana Djurdjevic; Oliver Einsle, Laure Decamps
      Abstract: The cofactor of nitrogenase is the largest and most intricate metal cluster known in nature. Its reactivity, mode of action and even the precise binding site of substrate remain a matter of debate. For decades, synthetic chemists have taken inspiration from the exceptional structural, electronic and catalytic features of the cofactor and have tried to either mimic the unique topology of the entire site, or to extract its functional principles and build them into novel catalysts that achieve the same - or very similar - astounding transformations. We review some of the available model chemistry as it represents the various approaches that have been taken from studying the cofactor, to eventually summarize the current state of knowledge on catalysis by nitrogenase and highlight the mutually beneficial role of model chemistry and enzymology in bioinorganic chemistry.
      PubDate: 2017-04-20T02:30:37.940622-05:
      DOI: 10.1002/asia.201700478
       
  • Rigid non-fullerene acceptors based on triptycene-perylene dye for organic
           solar cells
    • Authors: Dong Meng; Huiting Fu, Bingbing Fan, Jianqi Zhang, Yan Li, Yanming Sun, Zhaohui Wang
      Abstract: Three kinds of non-conjugated rigid perylene bisimide (PBI) derivatives based on a triptycene core were designed, synthesized and characterized. The unique three-dimensional (3D) conformation of triptycene could enable formation of polymer with the favorable morphology for organic polymer solar cells (PSCs) by relieving the self-aggregation of rigid PBI units. The low-lying LUMO energy levels of these compounds demonstrated that they are very suitable for using as acceptors in organic solar cells. A higher power conversion efficiency (PCE) of 6.15% was obtained for the blend film using T-2 as acceptor and commercial poly[[4,8-bis[5-(2-ethylhexyl)thiophene-2-yl]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)-carbonyl]thieno[3,4-b]thiophenediyl]] (PCE-10) as the electron donor.
      PubDate: 2017-04-19T04:20:47.976286-05:
      DOI: 10.1002/asia.201700440
       
  • Effects of stoichiometry on the H2 storage properties of
           Mg(NH2)2-LiH-LiBH4 tri-component system
    • Authors: Han Wang; Hujun Cao, Claudio Pistidda, Sebastiano Garroni, Guotao Wu, Thomas Klassen, Martin Dorheim, Ping Chen
      Abstract: Hydrogen desorption pathways and storage properties of 2Mg(NH2)2-3LiH-xLiBH4 samples (x = 0, 1, 2 and 4) were investigated systematically by combination of Pressure-Composition-Isotherm (PCI), Differential scanning calorimetric (DSC) and volumetric release methods. Experimental results show that the desorption peak temperatures of 2Mg(NH2)2-3LiH-xLiBH4 samples are ca. 10-15 oC lower compared to that of 2Mg(NH2)2-3LiH. Especially the 2Mg(NH2)2-3LiH-4LiBH4 composite begins to release hydrogen at 90 oC, exhibiting a superior dehydrogenation performance. All the LiBH4 doped samples can be fully dehydrogenated and re-hydrogenated at the temperature of 143 oC. The high hydrogen pressure region (above 50 bar) of PCI curves for the LiBH4 doped samples rise with the increasing of the LiBH4 amount. LiBH4 changes the desorption pathway of the 2Mg(NH2)2-3LiH sample under 50 bar hydrogen pressure, resulting in the formation of MgNH and molten [LiNH2-2LiBH4], which is different from the dehydrogenation pathways of 2Mg(NH2)2-3LiH sample without LiBH4 forming Li2Mg2N3H3 and LiNH2 as reported before. In addition, DSC results show that the doped samples exhibit two independent endothermic events, which may be related to two different desorption pathways.
      PubDate: 2017-04-18T23:22:02.835459-05:
      DOI: 10.1002/asia.201700287
       
  • Short-step Syntheses of 4-Deoxycarbazomycin B, Sorazolon E, and
           (+)-Sorazolon E2
    • Authors: Makoto Sako; Kazuya Ichinose, Shinobu Takizawa, Hiroaki Sasai
      Abstract: Short-step syntheses of 4-deoxycarbazomycin B and sorazolon E were established through the condensation of cyclohexanone and commercially available 4-methoxy-2,3-dimethylaniline, followed by Pd(II)-catalyzed dehydrogenative aromatization/intramolecular C-C bond coupling and deprotection. A chiral dinuclear vanadium complex (Ra,S,S)-6 mediated the first enantioselective oxidative coupling of sorazolon E, affording (+)-sorazolon E2 in good enantioselectivity.
      PubDate: 2017-04-18T07:20:30.011977-05:
      DOI: 10.1002/asia.201700471
       
  • Cyclometalated Iridium(III) Bipyridine-Phenylboronic Acid Complexes as
           Luminescent Probes for Sialic Acids and Bioimaging Reagents
    • Authors: Hua-Wei Liu; Wendell Ho-Tin Law, Lawrence Cho-Cheung Lee, Jonathan Chun-Wai Lau, Kenneth Kam-Wing Lo
      Abstract: Sialic acids play important roles in mammalian development, cell-cell attachment, and signaling. Since cancer cells utilize their overexpressed sialylated antigens to propagate metastases, the development of probes for sialic acids is of high importance. Herein, we report three luminescent cyclometalated iridium(III) bipyridine complexes bearing a phenylboronic acid (PBA) moiety. Spectrophotometric titrations revealed that the PBA complexes displayed higher binding affinity to the most common sialic acid N-acetylneuraminic acid (Neu5Ac) compared with simple sugars that are commonly found on glycoproteins. Notably, cellular imaging and uptake experiments showed that the PBA complexes were able to recognize cellular sialic acid residues, resulting in more efficient uptake than the boronic acid-free analogues. Additionally, one of the PBA complexes was shown to discriminate between cancerous and noncancerous cells.
      PubDate: 2017-04-18T06:21:12.671889-05:
      DOI: 10.1002/asia.201700359
       
  • A Scalable and Versatile Synthesis of Oxime-Based Hormone Dimers and Gels
           for Sustained Release
    • Authors: Christopher W. Bennett; Joe Collins, Zeyun Xiao, Daniel Klinger, Luke A. Connal
      Abstract: Well-defined steroid hormone dimers and organogels were produced via a facile and scalable synthesis using oxime click chemistry. The versatile synthetic procedure extends to a wide range of hormones and linker groups exemplified here through the synthesis of cortisol- and progesterone-dimers linked via hydrophobic, hydrophilic or functional groups. This method was also extended to the synthesis of cortisone-based organogels. Owing to the dynamic nature of the oxime bond, the hormone-based materials are degradable via acidic hydrolysis and transoximination representing new materials for the controlled release of steroid hormones.Keeping hormones in balance: Well-defined steroid hormone dimers and organogels were produced via a facile and scalable synthesis using oxime click chemistry. Owing to the dynamic oxime bonds, the hormone-based materials are degradable via acidic hydrolysis and transoximination, therefore representing new materials for the controlled release of steroid hormones.
      PubDate: 2017-04-18T01:55:36.879718-05:
      DOI: 10.1002/asia.201700288
       
  • A Novel Bat-Shaped Dicyanomethylene-4H-pyran-Functionalized
           Naphthalimidefor Highly Efficient Solution-Processed Multilevel Memory
           Devices
    • Authors: Jian-Mei Lu; Qi-jian Zhang, Shi-feng Miao, Hua Li, Jing-hui He, Na-jun Li, Qing-feng Xu, Dong-yun Chen
      Abstract: Small molecule based multilevel memory device has attracted increasing attentions since the advantages as super-high storage density, fast reading speed, light weight, low energy consumption, and shock resistance. However, the fabrication of small molecule-based device always needs expensive vacuum deposition techniques or high temperature for spin-coating. In this paper, through rationally tailoring of the previous molecule DPCNCANA, a novel bat-shaped A-D-A-type symmetric framework has been successfully synthesized, and can be dissolved in common solvents under room temperature. Meantime, it processes low bandgap in energy and densely intramolecular stacking in film state. The solution-processed memory devices exhibited high-performance nonvolatile multilevel data storage properties with low switching threshold voltages of about 1.3 V and 2.7 V, respectively, which is beneficial for low-power consumption. Our result will prompt the study of highly efficient solution-processed multilevel memory devices in the field of organic electronics.
      PubDate: 2017-04-18T01:20:59.505418-05:
      DOI: 10.1002/asia.201700438
       
  • Four-State Molecular Shuttling of [2]Rotaxanes Featuring Ammonium, Aniline
           (Anilinium), and Tetra(ethylene glycol) Stations in Response to Acid/Base
           and Alkali Metal Cation Stimuli
    • Authors: Masaki Kimura; Takuma Mizuno, Masahiro Ueda, Shinobu Miyagawa, Tsuneomi Kawasaki, Yuji Tokunaga
      Abstract: In this study we synthesized [2]rotaxanes possessing three recognition sites—a dialkylammonium, an alkylarylamine, and a tetra(ethylene glycol) station—in their dumbbell-like axle component and dibenzo[24]crown-8 (DB24C8) as their macrocyclic component. These [2]rotaxanes behaved as four-state molecular shuttles: (i) under acidic conditions, the DB24C8 unit encircled both the dialkylammonium and alkylarylammonium stations; (ii) under neutral conditions, the dialkylammonium unit was the predominant station for the DB24C8 component; (iii) under basic conditions, when both ammonium centers were deprotonated, the alkylarylamine unit became a suitable station for the DB24C8 component; and (iv) under basic conditions in the presence of an alkali metal cation, the tetra(ethylene glycol) unit recognized the DB24C8 component through cooperative binding of the alkali metal ion. In addition, we observed that the [2]rotaxanes exhibited selective recognition for metal cations. These shuttling motions of the macrocyclic component proceeded reversibly.
      PubDate: 2017-04-13T21:25:41.511987-05:
      DOI: 10.1002/asia.201700493
       
  • Arrangement of Proteinogenic α-Amino Acids on a Cyclic Peptide Comprising
           Alternate Biphenyl-Cored ζ-Amino Acids
    • Authors: Shohei Tashiro; Masayuki Chiba, Mitsuhiko Shionoya
      Abstract: Aiming at precisely arranging several proteinogenic α-amino acids on a folded scaffold, we have developed a cyclic hexapeptide comprising an alternate sequence of biphenyl-cored ζ-amino acids and proteinogenic α-amino acids such as l-leucine. The amino acids were connected by typical peptide synthesis, and the resultant linear hexapeptide was intramolecularly cyclized to form a target cyclic peptide. Theoretical analyses and NMR spectroscopy suggested that the cyclic peptide was folded into an unsymmetrical conformation, and the structure was likely to be flexible in CHCl3. The optical properties including UV/Vis absorption, fluorescence, and circular dichroism (CD) were also evaluated. Furthermore, the cyclic peptide became soluble in water by introducing three carboxylate groups at the periphery of the cyclic skeleton. This α/ζ-alternating cyclic peptide is therefore expected to serve as a unique scaffold for arranging several functionalities.α/ζ-Cyclic hexapeptide: A cyclic peptide comprising biphenyl-cored ζ-amino acids was synthesized to arrange proteinogenic α-amino acids alternately on a folded scaffold. Its conformation was elucidated based on NMR analyses and theoretical calculations. Furthermore, the cyclic peptide became soluble in water by introducing three carboxylate groups at the periphery of the cyclic skeleton.
      PubDate: 2017-04-13T11:37:55.963028-05:
      DOI: 10.1002/asia.201700203
       
  • Adsorption and desorption of single stranded DNA from single walled carbon
           nanotubes
    • Authors: Cameron James Shearer; LePing Yu, Renzo Fenati, Alex Sibley, Jamie Scott Quinton, Christopher Thomas Gibson, Amanda Vera Ellis, Gunther Andersson, Joseph George Shapter
      Abstract: The chemical affinity of single stranded DNA (ssDNA) to adsorb to the surface of single walled carbon nanotubes (SWCNTs) is used for SWCNT purification, separation and in bio-devices. Despite the popularity of research on SWCNT-ssDNA conjugates, very little work has been dedicated to study the removal of adsorbed ssDNA on SWCNTs. This paper reports a comprehensive study of biological, physical and chemical treatments for the removal of ssDNA from SWCNT-ssDNA suspensions. These include enzymatic cleavage, heat treatment under vacuum up to 400 oC, chemical treatments with high or low pH, oxidising conditions, and high ionic strength solvents. Complimentary characterisation techniques including fluorescence from a DNA intercalating dye (YO-PRO-1) and photoelectron spectroscopy are used to exhaustively study and compare the methods investigated. Enzyme treatment is found to remove the phosphate backbone only, leaving nucleosides adsorbed to SWCNTs. Heating in inert atmosphere is ineffective at removing ssDNA. Acid, base and oxidative treatment are found to be effective for the removal of ssDNA from SWCNTs. Where possible the mechanism of desorption is described and from the findings suggestions for 'best practise' are provided.
      PubDate: 2017-04-13T11:34:11.221704-05:
      DOI: 10.1002/asia.201700446
       
  • Reactivity of functionalized ynamides with tetracyanoethylene: scope,
           limitations and optoelectronic properties of the adducts
    • Authors: Marie Betou; Raphaël J. Durand, Antoine Sallustrau, Claire Gousset, Erwann Le Coz, Yann R. Leroux, Loïc Toupet, Elzbieta Trzop, Thierry Roisnel, Yann Trolez
      Abstract: The reactivity of functionalized ynamides and arylynamines with tetracyanoethylene at room temperature has been evaluated. In most cases, the corresponding 1,1,4,4-tetracyanobutadienes (TCBDs) have been obtained in good to excellent yields, following a sequence of [2+2]cycloaddition and [2+2]retroelectrocyclization. The influence of diverse functional groups on the yield of the reaction has been investigated, in particular concerning multiple ynamides. These TCBDs have been characterized by various spectroscopic techniques, electrochemistry and X-Ray diffraction for some of them.
      PubDate: 2017-04-13T11:33:10.136145-05:
      DOI: 10.1002/asia.201700353
       
  • Halogen-free synthesis of carbamates from CO2 and amines using titanium
           alkoxides
    • Authors: Jun-Chul Choi; Hao-Yu Yuan, Norihisa Fukaya, Syun-ya Onozawa, Qiao Zhang, Seong Jib Choi, Hiroyuki Yasuda
      Abstract: The direct synthesis of carbamates from amines and carbon dioxide in the presence of Ti(OR)4 (R = nBu (1), Me (2), Et (3), nPr (4)) was investigated. Aniline was reacted with the titanium n-butoxide (1) in the presence of carbon dioxide (5 MPa) to give the corresponding n-butyl N-phenylcarbamate (BPC) in nearly quantitative yield (99%) within 20 min. Furthermore, 1 could be regenerated upon reaction with n-butanol during water removal. The recovered 1 could then be reused in a subsequent reaction.
      PubDate: 2017-04-12T23:47:32.543681-05:
      DOI: 10.1002/asia.201700465
       
  • Preparation of Magnetically Recyclable Yolk/Shell FexOy/PdPt@CeO2
           Nanoreactors with Enhanced Catalytic Activity
    • Authors: Jie Wu; Chenchen Guan, Tongjie Yao, Junshuai Zhang, Xiao Zhang, Xin Huang
      Abstract: Noble metal nanoparticles (NPs) have received considerable attention in the field of catalysis. However, exploitation of their maximal catalytic properties is still a chanllenge. Nanoreactors could dramatically improve activity with the help of the intrinsic confinement effect. Herein, we designed a kind of yolk/shell FexOy/PdPt@CeO2 composites, in which FexOy NPs acted as movable core and allowed uniform distribution of PdPt alloys on the inner surface of the CeO2 shell. Due to the porosity of CeO2 shell and existence of hollow voids, FexOy/PdPt@CeO2 composites could be used as nanoreactors in catalytic reactions. Besides the confinement effect, two other structural aspects further contribute to enhance the catalytic activity: bimetallic PdPt alloys replacing monometallic NPs, and the reactive CeO2 shell replacing the chemically inert support. As a result, the nanoassembled catalysts displayed higher activity in catalytic reduction of dyes than the reference samples. Moreover, these catalysts were reusable because they could be quickly separated by a magnet due to the presence of the magnetic FexOy core.
      PubDate: 2017-04-12T22:18:26.192312-05:
      DOI: 10.1002/asia.201700525
       
  • Unusual Assembly and Conversion of Graphene Quantum Dots into Crystalline
           Graphite Nanocapsules
    • Authors: Liangti Qu; Jian Gao, Chenyu Xu, Yue Hu, Fei Zhao, Changxiang Shao, Yang Zhao, Shilv Chen
      Abstract: The development of a facile strategy for conversion of graphene quantum dots (GQDs) into crystalline graphite is of great practical significance, which still remains challenging. Herein, a rationally assembled crystalline-intercrossed graphite nanocapsules (CI-GNCs) has been achieved by a one-step electrochemical-induced strategy with the assistant of soft template, in which the GQDs act as the initial building blocks. The as-prepared CI-GNCs exhibit high crystalline graphitic-like nanostructures. Moreover, it possesses a promising electrocatalytic activity for oxygen reaction reduction (ORR) in an alkaline medium. This simple fabrication technology presents a great advance for synthesizing CI-GNCs composite catalyst which holds the potential as new metal free catalysts for efficient ORR application.
      PubDate: 2017-04-12T22:17:39.309642-05:
      DOI: 10.1002/asia.201700297
       
  • Stabilities and Biological Activities of Vanadium Drugs: What is the
           Nature of Active Species?
    • Authors: Aviva Levina; Peter Andrew Lay
      Abstract: Diverse biological activities of vanadium(V) drugs mainly arise from their abilities to inhibit phosphate-dependent enzymes and to alter cell signaling. Initial interest focused on anti-diabetic activities but has shifted to anti-cancer and anti-parasitic drugs. V-based anti-diabetics are pro-drugs that release active components (e.g., H₂VO₄¯) in biological media. By contrast, V anti-cancer drugs are generally assumed to enter cells intact; however, speciation studies indicate that nearly all drugs are likely to react in cell culture media during in-vitro assays and the same would apply in vivo. The biological activities are due to V(V) and/or V(IV) reaction products with cell culture media, or the release of ligands (e.g., aromatic diimines, 8-hydroxyquinolines or thiosemicarbazones) that bind to essential metal ions in the media. Careful consideration of the stability and speciation of V complexes in cell culture media and in biological fluids is essential to design targeted V-based anti-cancer therapies.
      PubDate: 2017-04-11T21:26:00.891775-05:
      DOI: 10.1002/asia.201700463
       
  • Symmetry Breaking in Pyrrolo[3,2-b]pyrroles: Synthesis,
           Solvatofluorochromism, and Two-photon Absorption
    • Authors: Daniel T Gryko; Aleksander Mikhaylov, Łukasz Łukasiewicz, Hye Gun Ryu, Aleksander Rebane, Kyo Han Ahn, Marzena Banasiewicz, Bolesław Kozankiewicz, Denis Jacquemin, Cloe Azarias
      Abstract: Five centrosymmetric and one dipolar pyrrolo[3,2-b]pyrroles, possessing, respectively, either two- or one strongly electron-withdrawing nitro groups have been synthesized in a straightforward manner from simple building blocks. In the symmetric compounds the nitroaryl groups induced spontaneous breaking of inversion symmetry in the excited-state, leading to large solvatofluorochromism. To study the origin of this effect, the series employed peripheral structural motifs that control the degree of conjugation via altering of dihedral angle between the 4-nitrophenyl moiety and the electron-rich core. We observed that for compounds with a larger dihedral angle, fluorescence quantum yield decreased quickly when exposed to even moderately polar solvents. Reducing the dihedral angle (i.e., placing the nitrobenzene moiety in the same plane as the rest of the molecule) moderated the dependence on solvent polarity so that the dye exhibited significant emission, even in THF. To investigate at what stage the symmetry breaking occurs, we measured two-photon absorption (2PA) spectrum and 2PA cross-sections (σ2PA) for all six compounds. The 2PA transition profile of the dipolar pyrrolopyrrole, followed the corresponding one-photon absorption (1PA) spectrum, which provided an estimate of the change of the permanent electric dipole upon transition ~18 D. The nominally symmetric compounds displayed an allowed 2PA transition in the wavelength range, 700-900 nm. In the S0S1 transition region, the symmetric structures also showed a partial overlap between 2PA and 1PA transitions in the long-wavelength wing of the band, from which a tentative, relatively small dipole moment change, 2-7 D, was deduced, thus suggesting that some slight symmetry breaking may be possible in the ground state, even before major symmetry breaking occurs in the excited-state.
      PubDate: 2017-04-11T08:20:27.9954-05:00
      DOI: 10.1002/asia.201700159
       
  • Simple Nanodroplet Templating Functional Surfaces with Tailored
           Wettability and Microstructures
    • Authors: Shuhua Peng; Xuehua Zhang
      Abstract: Recently, solvent exchange has been demonstrated as a simple, solution based approach for the controlled formation of surface nanodroplets over large areas. The as-formed surface nanodroplets provide new opportunities for a wide range of droplet based applications. In this work, we demonstrate that surface nanodroplets can be used as versatile structural templates for fabrication of functional surfaces with tailored wettability and morphology. Guided by the microstructural and wetting properties of desert beetle back and cactus spine, we prepared two types of functional surfaces. The first biomimetic surface of desert beetle back with hydrophilic lumps on a hydrophobic background was obtained by independently selective surface modification of polymerized surface nanodroplets and background surface. The second surface with anisotropic wetting microstructures was fabricated by controlled deposition of droplets on the rim of polymer lenses. Our results showed that systematic improvement of wettability and the efficiency of water collection by using the as-prepared biomimetic surfaces, compared to the substrates without the designed microstructures. This work demonstrates surface nanodroplets as a new type of templates to design and prepare functional surfaces with controlled wettability and morphology.
      PubDate: 2017-04-10T21:20:27.513384-05:
      DOI: 10.1002/asia.201700358
       
  • Cu(І)-Mediated Denitrogenative Macrocyclization for the Synthesis of
           Cyclic α3β-Tetrapeptide Analogs
    • Authors: Chun-Chi Chen; Sheng-Fu Wang, Yung-Yu Su, Yuya A. Lin, Po-Chiao Lin
      Abstract: A copper(I)-mediated denitrogenative reaction has beensuccessfully developed in the preparation of cyclic tetrapeptides. A key reactive intermediate, ketenimine, triggers the key intramolecular cyclization by the terminal amine group and therefore generates an internal β-amino acid with an amidine linkage. The chemistry developed here provides a new synthetic route for the preparation of cyclic α3β-tetrapeptide analogs which are rich in information to the conformational study of macrocycles as well as important biologically active peptides. With the success of this Cu(I)-catalyzed macrocyclization, two histone deacetylase (HDAC) inhibitor analogs whose frameworks constituted by cyclic α3β-tetrapeptides have been successfully synthesized.
      PubDate: 2017-04-10T12:15:28.573012-05:
      DOI: 10.1002/asia.201700339
       
  • Catalytic Systems for the Cross-linking of Organosilicon Polymers
    • Authors: Esteban Mejía; Dengxu Wang, Johann Klein
      Abstract: Silicones and silicone rubbers are omnipresent in household and industrial products like lubricants, coatings, sealants, insulators, medical devices, etc. This plethora of applications arises from their unparalleled properties like hydrophobicity, low surface energy, chemical inertness, extreme temperature stability, elasticity and biocompatibility. Even though silicones are known since more than five decades, they are still ill-characterized and their chemistry is still far from fully understood. Industrially, the vast majority of processes for their synthesis, transformation and use are based in rather well established, alas outdated technologies, which are frequently empirical and poorly investigated. This review attempts to summarize the different approaches for the synthesis of silicone rubbers via vulcanization or curing of silicone polymers, the catalysts used and the corresponding reaction mechanisms. Apart from the well-known methods, (radical, hydrosilylation, and metal-based condensation), novel approaches like organo-, and bio-catalysis are also addressed
      PubDate: 2017-04-10T09:20:45.057726-05:
      DOI: 10.1002/asia.201700304
       
  • Cimicifoetones A and B, Dimeric Prenylindole Alkaloids as Black Pigments
           of Cimicifuga foetida
    • Authors: Chang-Xin Zhou; Yu-E Yu, Rong Sheng, Jian-Xia Mo, Min Huang, Liang Ouyang, Lishe Gan
      Abstract: Two dimeric prenylindole alkaloids with an unique indole-benzoindolequinone skeleton, cimicifoetones A (1) and B (2), were isolated as black pigments from the rhizomes of Cimicifuga foetida. The structures were elucidated by spectroscopic methods including HRMS and 2D NMR, as well as single crystal X-ray diffraction and computational chemical modeling techniques. Cimicifoetones A and B represented the first examples of dimeric indole alkaloids generated through [4+2] Diels-Alder cycloaddition between the prenyl side chain in one 3-prenylindole and the aromatic ring in another. The two compounds showed promising anti-proliferative activity on seven tumor cell lines with IC50 in the range of 1.36-21.09 μM. Flow cytometric and western blot analysis revealed that compound 2 induced cell apoptosis via death receptor-mediated extrinsic and mitochondrial-mediated intrinsic pathways.
      PubDate: 2017-04-09T23:20:30.316439-05:
      DOI: 10.1002/asia.201700348
       
  • Recent Developments on the Preparation of Silicones with Antimicrobial
           Properties
    • Authors: Annika Kottmann; Esteban Mejia, Therese Hemery, Johann Klein, Udo Kragl
      Abstract: This focus review describes the state of the art of the methods for preparing antimicrobial silicones. Considering the diversity of antimicrobial activity and their mechanisms, the performance of these materials is highly dependent on the characteristics of the polymeric matrix. Therefore, different synthetic routes have been developed, including (a) physical treatments, (b) chemical transformations and (c) copolymerization. This classification is not exclusive, so some products belong to more than one "class". Herewith, we attempt to make a handy overview about the development of antimicrobial silicones, their most important application fields, the most relevant antimicrobial assays, and, as the title suggests, an overview of the most relevant preparation methods.
      PubDate: 2017-04-09T21:25:45.500974-05:
      DOI: 10.1002/asia.201700244
       
  • Ambient-pressure stabilization of β-GdB3O6 by doping Bi3+ and
           color-tunable emissions by co-doping Tb3+ and Eu3+: the first
           photoluminescence study on the high-pressure polymorph
    • Authors: Tao Yang; Xiaorui Sun, Pengfei Jiang, Wenliang Gao, Xianju Zhou, Rihong Cong
      Abstract: Rare earth borates are good candidates in optical applications. Till now, the high-pressure/high-temperature technique produced a large number of novel borates, however, whose optical properties were rarely investigated due to the severe problem of containing substantial defects. We targeted the high-pressure polymorph of β-GdB3O6 and synthesized three solid solutions of β-Gd0.75-xBi0.25TbxB3O6 (0 ≤ x ≤ 0.75), β-Gd0.75-yBi0.25EuyB3O6 (0 ≤ y ≤ 0.75), and β-Gd0.50-zBi0.25Tb0.25EuzB3O6 (0 ≤ z ≤ 0.05) by typical solid state reactions at 820 °C. Here, the function of Bi3+ is to stabilize the high-pressure phase by lowering down the synthetic temperature as well as being the sensitizers to promote the green and red emissions of Tb3+ and Eu3+. The multiple energy transfer paths were investigated by lifetime decay experiments and photoluminescent spectra, and both efficiency and mechanism were determined. Eventually, color-tunable and white emissions were achieved by rational doping of Bi3+, Tb3+, and Eu3+ into β-GdB3O6, i.e. the CIE chromaticity coordinate for β-Gd0.44Bi0.25Tb0.30Eu0.01B3O6 is (0.318, 0.365) with correlated color temperature of 6101 K
      PubDate: 2017-04-07T10:20:39.115921-05:
      DOI: 10.1002/asia.201700405
       
  • Targeted Synthesis of Ultrastable High-Silica RHO Zeolite through Alkali
           Metal-Crown Ether Interaction
    • Authors: Quanli KE; Tianjun Sun, Hao Cheng, Haijun Chen, Xiaowei Liu, Xiaoli Wei, Shu-Dong Wang
      Abstract: High-silica RHO zeolite was directly synthesized using an alkali metal-crown ether (AMCE) complex as organic structure-directing agent (OSDA). Derived from the UV-vis spectra and zeolite patterns, the crown ether-cesium cation interaction was found to have crucial effect on the enhancement of silica content within the zeolite framework. The synthesized RHO zeolites possess up to four times larger silica/alumina ratio (SAR) values than that in their conventional form, which gives them extraordinarily rigid frameworks even after hydrothermal aging under 800℃. Compared to commercial zeolites, copper-exchanged high-silica RHO zeolites demonstrate considerably high reaction activity in NOX removal, making them promising candidates for diesel exhaust treatment.
      PubDate: 2017-04-06T11:32:41.016306-05:
      DOI: 10.1002/asia.201700303
       
  • Structural elucidation of trace amounts of volatile compounds Using the
           crystalline sponge method
    • Authors: Nicolas Zigon; Takashi Kikuchi, Junko Ariyoshi, Yasuhide Inokuma, Makoto Fujita
      Abstract: Volatile organic compounds are widely present as scents and odors in our daily lives and are readily found in a variety of natural extracts. Because these compounds are highly volatile and usually available only in minute quantities, little attention has been paid to X-ray diffraction as a technique for their structure determination. Here, we show that the structures of volatile organic compounds are easily elucidated using minute quantities of the compounds and the crystalline sponge method. The compound vapors can be directly absorbed into the sponge crystals, or alternatively, preparative gas-chromatography can be used to separate the desired compound from a natural mixture.
      PubDate: 2017-04-05T21:21:12.019061-05:
      DOI: 10.1002/asia.201700515
       
  • Probing Effect of Salinity and pH on Surface Interactions between Air
           Bubbles and Hydrophobic Solids: Implications on Colloidal Assembly at
           Air/Water Interface
    • Authors: Xin Cui; Chen Shi, Shuo Zhang, Lei Xie, Jing Liu, Dazhi Jiang, Hongbo Zeng
      Abstract: In this work, bubble probe atomic force microscope (AFM) was employed to quantify the interactions between two air bubbles and between an air bubble and an octadecyltrichlorosilane (OTS)-hydrophobized mica under various aqueous conditions. The key parameters (e.g. surface potentials, decay length of hydrophobic attraction) were obtained by analyzing the measured forces through a theoretical model based on Reynolds lubrication theory and augmented Young-Laplace equation by including effect of disjoining pressure. The bubble-OTS hydrophobic attraction with a decay length of 1.0 nm was found to be independent of solution pH and salinity. These parameters were further used to predict the attachment of OTS-hydrophobized particles onto air/water interface, demonstrating that particle attachment driven by hydrophobic attraction could be facilitated by suppressing electrical double-layer repulsion at low pH or high salinity condition. This facile methodology can be readily extended to quantify interactions of many other colloidal particles with gas/water and oil/water interfaces, with implications on colloidal assembly at different interfaces in many engineering applications.
      PubDate: 2017-04-05T14:21:30.026487-05:
      DOI: 10.1002/asia.201700388
       
  • Porous Peptide Complexes by a Folding-and-Assembly Strategy
    • Authors: Tomohisa Sawada; Motoya Yamagami, Shuji Akinaga, Tatsuki Miyaji, Makoto Fujita
      Abstract: Concerted folding and assembly processes are necessary for protein self-assembly, yet such a concerted strategy has rarely been attempted by synthetic chemists. In this work, we have created a new porous peptide structure through a coordination-driven folding-and-assembly strategy. A porous framework with 1.5 nm-sized pores and a PII helical peptide scaffold was successfully obtained by complexation of AgNTf2 and tripeptide ligands containing the Gly-Pro-Pro sequence. The pores were modified in various ways with retention of the latent PII helical conformation of the peptide ligand.
      PubDate: 2017-04-05T11:21:20.630746-05:
      DOI: 10.1002/asia.201700458
       
  • A stimuli responsive metallohydrogel exhibiting cyclohexane like
           hydrophobicity
    • Authors: Uday Maitra; Raju Laishram
      Abstract: Silver(I) forms a hydrogel in the presence of cholate with unusual properties, not observed with other cations. Polarity-sensitive probes have shown that the spherical aggregates observed in the gel have 'pockets' with hydrophobicity comparable to that of degassed cyclohexane. The gel exhibited thermo- and mechanoresponsive properties. Color tunability from blue to cyan and green was observed with prodan. The two sol phases of the gel form by applying stress and temperature showed very different properties.
      PubDate: 2017-04-05T08:21:46.540041-05:
      DOI: 10.1002/asia.201700289
       
  • Electronic spectroscopy of protonated 1-aminopyrene in a cold ion trap
    • Authors: Christophe Jouvet; Jennifer Anna Noble, Claude Dedonder-Lardeux, Joëlle Mascetti
      Abstract: For aromatic systems with an amino group there is a competition between protonation on a carbon atom of the skeleton and on the amino group. In this work we study thephotofragmentation of protonated 1-aminopyrene in a cold ion trap and observe mainly the protonated amino tautomer, leading to fragmentation pathways via loss of H or loss of NH3, Several excited states have been assigned, among which the fourth excited state shows broadened bands indicating a fast decay attributed to the presence of a πσ* charge transfer state by comparison of the xperimental results with ab-initio calculations. We show that we can deduce the πσ* transition energy in protonated aromatic amino compounds of increasing size directly from the ionisation potential of the neutral aromatic unsubstituted molecule. Tautomers protonated on a carbon atom of the pyrene skeleton are also weakly observed, and we show that two tautomers protonated on a carbon atom of the aromatic ring can be distinguished by their electronic pectroscopy.
      PubDate: 2017-04-05T08:21:45.028866-05:
      DOI: 10.1002/asia.201700327
       
  • CO2 Fixation with Epoxides under Mild Conditions with a Cooperative Metal
           Corrole - Quaternary Ammonium Salt Catalyst System
    • Authors: Maximilian Tiffner; Sabrina Gonglach, Michael Haas, Wolfgang Schöfberger, Mario Waser
      Abstract: We have investigated the cooperative catalytic activity of several metal corrole complexes in combination with tetrabutyl-ammonium bromide (TBAB) for the reaction of epoxides with CO2 to cyclic carbonates. It was found that the use of just 0.05 mol% of a manganese(III)corrole with 2 mol% TBAB exhibits excellent catalytic activity under 1 atmosphere of CO2.
      PubDate: 2017-04-05T07:20:49.828281-05:
      DOI: 10.1002/asia.201700354
       
  • High-Efficiency, Green, and Scalable β-Cyclodextrin-Assisted Aqueous
           Exfoliation of Transition Metal Dichalcogenides: the Cases of MoS2 and
           ReS2
    • Authors: Wancheng Zhao; Xingxing Tan, Jingyun Jiang, Feijie Liu, Tiancheng Mu
      Abstract: β-cyclodextrin-assisted aqueous-exfoliation method is successfully introduced to prepare transition metal dichalcogenides nanosheets (TMDs), which is cheap, high-efficiency, scalable, and environmentally friendly. As the cases, MoS2 and ReS2 nanoflakes are prepared using our method. Particularly, the effective exfoliation of ReS2 crystal in aqueous environment is demonstrated for the first time. Moreover, exfoliated nanomaterials can be availably utilized in hydrogen evolution reaction (HER) as noble-metal-free catalyst. This work provides new chances for high-efficiency exfoliation of TMDs and other 2D nanomaterials into few-layer nanosheets in aqueous medium, which production possesses better biocompatibility, broader applicability and greater sustainability.
      PubDate: 2017-04-03T22:20:30.168424-05:
      DOI: 10.1002/asia.201700355
       
  • A novel self-quenching system based on bis-naphthalimide: a dual
           two-photon-channel GSH fluorescent probe
    • Authors: Shen Wei; Jingyan Ge, Siyang He, Ruoyu Zhang, Chengyan Zhao, Yong Fan, Shian Yu, Bin Liu, Qing Zhu
      Abstract: Abstract: The single fluorescent signal output often does not satisfy the requirement of detection accuracy for bioactive compounds in biological system. It is of great interest to develop a dual-channel turn-on fluorescence sensing system for self-validated detection. Herein, we report a novel self-quenching nanoparticle composed of dual two-photon dyes of naphthalimides, displaying almost no fluorescence at both channels due to aggregation-caused quenching (ACQ). A dual two-photon-channel fluorescent probe for GSH was further developed by inserting a disulfide bond between two naphthalimides. Upon the treatment of GSH, the disulfide bond was cleaved and two napthalimide fluorophores were separated, leading to turn-on fluorescence at both channels. This dual-two-photon-channel design strategy can be easily extended to other analytes, simply by changing the linker molecules, which opens new opportunities to accurately monitor various biological processes in living cells.
      PubDate: 2017-04-01T03:20:38.642026-05:
      DOI: 10.1002/asia.201700340
       
  • 2D Crystallization of Rylene Diimide-Based n-Type Semiconductors Tuned by
           Aromatic Dimension at the Liquid/Solid Interface
    • Authors: Zongxia Guo; Ping Yu, Kai Sun, Wenpin Wang, Yuhan Wei, Zhibo Li
      Abstract: Investigation of semiconducotors at the surface provides opportunities for deep observation and understanding the mechanism of molecular interaction for designing semiconductors to build up organic electronics with fine performance. Herein, 2D crystallization of rylene diimide-based n-type semiconductors (1, 2, 3 and 4) are explored at the liquid/highly oriented pyrolytic graphite (HOPG) interface by means of scanning tunneling microscopy (STM). Rylene diimide 1, 2, 3 with increased aromatic dimensions show diffrent surface crystalization behaviours and distinguished 2D patterns. Surface chirality is directly affected by the aromatic dimension as well. The 2D patterns and the surface chirality can also be tuned by solvent nature. In addition, the molecular symmetry is of great important to form long range ordered 2D monolayers. This investigation hilights the importance of the rational design on molecular dimension and geometrical symmetry in achieving determined 2D nanopatterns on surfaces, especially for the rylene diimide-based n-type semiconductors.
      PubDate: 2017-03-31T06:40:22.764739-05:
      DOI: 10.1002/asia.201700271
       
  • Enzymatic synthesis of 7',5'-bicyclo-DNA oligonucleotides
    • Authors: Stella Diafa; Damien Evéquoz, Christian J Leumann, Marcel Hollenstein
      Abstract: The selection of artificial genetic polymers with tailor-made properties for their application in synthetic biology requires the exploration of new nucleosidic scaffolds that can be used in selection experiments. Here, we describe the synthesis of a bicyclo-DNA triphosphate (7',5'-bc-TTP) and show its potential to serve for the generation of new xeno-nucleic acids (XNAs) based on this scaffold. 7',5'-bc-TTP is a good substrate for Therminator DNA polymerase and up to seven modified units can be incorporated into a growing DNA chain. In addition, this scaffold sustains XNA-dependent DNA synthesis as well aspotentially XNA-dependent XNA synthesis . However, the DNA-dependent XNA synthesis on longer templates is hampered by the competitive misincorporation of dATP caused by the slow rate of incorporation of 7',5'-bc-TTP.
      PubDate: 2017-03-31T04:25:25.22949-05:0
      DOI: 10.1002/asia.201700374
       
  • Biocatalysis in Silicon Chemistry
    • Authors: Mark B Frampton; Paul M. Zelisko
      Abstract: The application of biocatalytic or chemoenzymatic techniques in silicon chemistry serves two roles. It provides a greater understanding of the processing of silicon species by natural systems such as plants, diatoms, and sponges as well opening avenues to green methodologies in the field. In the latter case biocatalytic approaches have been applied to the synthesis of small molecule systems as well as polymeric materials. Often these biocatalytic approaches allow access to molecular structures under mild conditions and, in some cases, molecular structures that are not accessible through traditional chemical methodologies. A focused review of the recent advances in the applications of biocatalysis in silicon chemistry is presented.
      PubDate: 2017-03-29T08:28:37.752806-05:
      DOI: 10.1002/asia.201700214
       
  • Nonconventional Luminescence Enhanced by Silicone Induced Aggregation
    • Authors: Hang Lu; Ziqi Hu, Shengyu Feng
      Abstract: Nonconventional organic luminogens have attracted a great deal of interests because of the unusual fluorescence emission, interesting properties and promising applications. According to previous studies, introduction of Si-O units in the luminogens could enhance the fluorescence emission. Herein, we have synthesized some fluorescent siloxane derivatives and similar molecules without Si-O units by simple and efficient modification to investigate the role of the Si-O units in the emission. It was found that the strong emission could be observed in siloxane derivatives dilute solution, but not in the carbon compounds. UV−vis absorption, luminescence spectra, nuclear magnetic resonance spectra, and theoretical calculations were further performed to indicate that the heteroatom and the Si-O unit formed the coordination bond in the siloxane derivatives, resulting in the enhanced fluorescence emission.
      PubDate: 2017-03-29T02:25:35.743748-05:
      DOI: 10.1002/asia.201700234
       
  • Intuitive Understanding of σ Delocalization in Loose and σ Localization
           in Tight Helical Conformations of an Oligosilane Chain
    • Authors: Milena Jovanovic; Dean Antic, David Rooklin, Annika Bande, Josef Michl
      Abstract: Conformational effects on σ-electron delocalization in oligosilanes are addressed by Hartree-Fock and time-dependent density functional theory (B3LYP, 6-311G**) at MP2 optimized geometries of permethylated uniformly helical linear oligosilanes (all-ω-SinR2n+2) up to n = 16 and for backbone dihedral angles ω = 55 - 180̊. The extent of σ delocalization is judged by the partition ratio of the highest occupied molecular orbital and is reflected in the dependence of its shape and energy and of UV absorption spectra on n. The results agree with known spectra of all-transoid conformers (all-[±165]-SinMe2n+2) and reveal a transition at ω = ~90̊ from the "σ-delocalized" limit at ω = 180̊ toward and close to the physically non-realizable "σ-localized" limit ω = 0 with entirely different properties. The distinction is also obtained in the simple Hückel Ladder H and C models of σ delocalization. An easy intuitive way to understand the origin of the two contrasting limits is to first view the linear chain as two subchains with alternating primary and vicinal interactions (σ-hyperconjugation), one consisting of the odd and the other of the even σ(SiSi) bonds, and then allow the two subchains to interact by geminal interactions (σ conjugation).
      PubDate: 2017-03-27T13:20:26.052474-05:
      DOI: 10.1002/asia.201700226
       
  • Self-Healable Suparmolecular Hydrogel Formed by Nor-Seco-Cucurbit[10]uril
           as a Supramolecular Crosslinker
    • Authors: Kyeng Min Park; Joon Ho Roh, Gihyun Sung, James Murray, Kimoon Kim
      Abstract: A supramolecular hydrogel was formed by a simple mixing of solutions of nor-seco-cucurbit[10]uril (NS-CB[10]) and adamantylamine terminated-4 armed polyethyleneglyol (AdA-4-arm-PEG). In the formation of the hydrogel, NS-CB[10] acted as a noncovalent crosslinker to form a ternary complex with two AdA moieties. The dynamic and selective nature of the host-guest interaction between NS-CB[10] and AdA enabled the supramolecular hydrogel to rapidly recover its physical properties after it was damaged. In addition, the recovered hydrogel showed sustained physical properties with negligible differences from those of the pristine material, even after multiple self-healing cycles. The NS-CB[10] based hydrogel with the self-healing property may be useful for various bioapplications such as drug delivery, cell therapy and tissue engineering.
      PubDate: 2017-03-24T02:00:34.877659-05:
      DOI: 10.1002/asia.201700386
       
  • Simple and Versatile Preparation of Luminescent Amphiphilic
           Platinum(II)-containing Polystyrene Complexes With Transformable
           Nanostructures Assisted by Pt⋅⋅⋅Pt and π–π Interactions
    • Authors: Heung-Kiu Cheng; Clive Yik-Sham Chung, Kaka Zhang, Vivian Wing-Wah Yam
      Abstract: Platinum(II)-containing polystyrene (PS) complexes have been synthesized by dehydrohalogenation of α-alkyne-PS and chloroplatinum(II) precursors with different functionalities on the terpyridine ligands. Through modulation of the hydrophilicity/hydrophobicity of the terpyridine ligands and hence the overall amphiphilicity of the complexes, the complexes can undergo self-assembly into various superstructures with remarkable luminescence properties in different solution mixtures, as revealed by electron microscopy, UV/Vis absorption and emission spectroscopy. Pt⋅⋅⋅Pt and/or π–π interactions among the platinum(II) terpyridine moieties are found to play substantial roles in the stabilization of the superstructures and the turn-on/off of the triplet metal–metal-to-ligand charge transfer (3MMLCT) emission of the complexes.Go platinum: A series of platinum(II)-containing polystyrene complexes has been synthesized and demonstrated to undergo self-assembly into different superstructures in various solvent mixtures with the stabilization of Pt⋅⋅⋅Pt and/or π–π interactions, resulting in remarkable luminescence changes.
      PubDate: 2017-03-23T08:25:32.136895-05:
      DOI: 10.1002/asia.201700123
       
  • Photoelectrochemical hydrogen peroxide production from water on a
           WO3/BiVO4 photoanode and from O2 on an Au cathode without external bias
    • Authors: Kojiro Fuku; Yuta Miyase, Yugo Miseki, Takashi Funaki, Takahiro Gunji, Kazuhiro Sayama
      Abstract: The photoelectrochemical production and degradation properties of hydrogen peroxide (H2O2) were investigated on a WO3/BiVO4 photoanode in an aqueous electrolyte of hydrogen carbonate (HCO3−). Highly-concentration of HCO3- species rather than CO32- species inhibited the oxidative degradation of H2O2 on the WO3/BiVO4 photoanode, resulting in achieving effectively oxidative H2O2 generation and accumulation from water (H2O). Moreover, the Au cathode facilitated two-electron reduction of O2, resulting in reductive H2O2 production with high current efficiency. Combining the WO3/BiVO4 photoanode with a HCO3- electrolyte and an Au cathode also produced a clean and promising design for a photoelectrode system specializing in H2O2 production (Selectivity: anode(H2O2)=ca 50%, cathode(H2O2)=ca 90%) even without applied voltage between photoanode and cathode under simulated solar light via 2-photon process; this achieved effective H2O2 production using an Au-supported porous BiVO4 photocatalyst sheet.
      PubDate: 2017-03-23T03:20:27.658597-05:
      DOI: 10.1002/asia.201700292
       
  • Bifunctional cage-type cubic mesoporous silica SBA-1 nanoparticles for
           selective adsorption of dyes
    • Authors: Chien-Hua Lin; Juti Rani Deka, Cheng-En Wu, Cheng-Hsun Tsai, Diganta Saikia, Yung-Chin Yang, Hsien-Ming Kao
      Abstract: Bifunctional SBA-1 mesoporous silica nanoparticles (MSNs) with carboxylic acid and amino groups (denoted as CNS-10-10) are successfully synthesized, characterized and employed as adsorbents for dye removal. The adsorbent CNS-10-10 shows high affinity towards cationic and anionic dyes in a wide pH range, and exhibits selective dye removal of a two dye mixture system of cationic methylene blue and anionic eosin Y. By changing the medium pH, the selectivity of adsorption behavior can be easily modulated. For comparison purposes, the counterparts, i.e., pure silica SBA-1 MSNs (CS-0) and the ones with either carboxylic acid or amino functional groups (denoted as CS-10 and NS-10, respectively) are also prepared to evaluate their dye adsorption behaviors. As revealed by the zeta potential measurements, the electrostatic interaction between the adsorbent surface and the dye molecule plays an important role in the adsorption mechanism. The adsorbent CNS-10-10 can be easily regenerated and reused, and remains its adsorption efficiency up to 80% after four cycles.
      PubDate: 2017-03-23T01:30:39.521938-05:
      DOI: 10.1002/asia.201700286
       
  • Synthesis of pyridine-zinc-based porous organic polymer for
           cocatalyst-free cycloaddition of epoxides
    • Authors: He Li; Chunzhi Li, Jian Chen, Lina Liu, Qihua Yang
      Abstract: Synthesis of solid catalysts for co-catalyst free CO2 cycloaddition reaction has attracted much research attention. Herein we report a hierarchical porous organic polymer, Py-Zn@MA which could catalyze cycloaddition reaction with epoxides and CO2 without using any additives or co-catalyst to afford turnover frequency (TOF) as high as 250 and 97 h-1 at 130 oC using pure and diluted CO2 (a simulating flue gas), respectively. These results are superior to most ever reported heterogeneous co-catalyst free systems. The high activity of Py-Zn@MA is mainly attributed to its bifunctional nature with ZnBr2 and pyridine activating epoxide in a cooperative way. It is worth mentioning that Py-Zn@MA could be easily prepared in large-scale without using any catalyst and the chemicals are cost-effective. Meanwhile, Py-Zn@MA shows good substrate universality for cycloaddition reactions of epoxides. Our designed POP material Py-Zn@MA has the potential to serve as an efficient catalyst in direct conversion of flue gas with epoxides into value-added cyclic carbonates.
      PubDate: 2017-03-22T01:27:59.119846-05:
      DOI: 10.1002/asia.201700258
       
  • De novo Synthesis of Mono- and Oligosaccharides via Dihydropyran
           Intermediates
    • Authors: Wangze Song; Shuojin Wang, Weiping Tang
      Abstract: The importance of carbohydrates is evident by its essential role in all living systems. Their syntheses have attracted chemists' attention for over a century. Most chemical syntheses in this area focused on the preparation of carbohydrates from naturally occurring monosaccharides. De novo chemical synthesis of carbohydrates from feedstock starting materials has emerged as a complementary method for the preparation of diverse mono- and oligosaccharides. In this review, we will briefly discuss the history of de novo carbohydrate synthesis and focus on methods that address the formation of glycosidic bonds for potential de novo synthesis of oligosaccharides. Almost all methods of this kind involve the formation of dihydropyran intermediates. We will discuss recent progresses on forming dihydropyrans by Achmatowicz rearrangement, hetero-Diels-Alder cycloaddition, ring-closing metathesis, and other methods.
      PubDate: 2017-03-20T09:21:05.404738-05:
      DOI: 10.1002/asia.201700212
       
  • Surface Triggered Tandem Coupling Reactions of Cyclic Azasilanes
    • Authors: Youlin Pan; Annalese Maddox, Taewoo Min, Ferdinand Gonzaga, Jonathan Goff, Barry Arkles
      Abstract: Cyclic azasilanes have been synthesized for the purpose of developing coupling agents appropriate for a variety of nanotechnologies including surface modification of nanoparticles, nanocrystals, mesoporous materials and substrates. N-methyl-aza-2,2,4-trimethylsilacyclopentane is representative of this class of compounds. Preliminary data for the treatment of inorganic surfaces, including nanoparticles and oxidized silicon wafers, with cyclic azasilanes suggest high density monolayer deposition by a ring-opening reaction. Cyclic azasilanes contain cryptic amine functionality that can perform a subsequent 'tandem' coupling reaction with functional molecules after the surface triggered ring-opening reaction, allowing for a one-pot self-assembly route on nanostructures. Tandem coupling reactions are demonstrated via addition reactions of the cryptic amine with epoxy and acrylate systems.
      PubDate: 2017-03-20T02:16:02.100163-05:
      DOI: 10.1002/asia.201700137
       
  • Brazilin Inhibits Prostatic Acidic Phosphatase Fibrillogenesis and Reduces
           its Cytotoxicity
    • Authors: Ming Li; Xiaoyan Dong, Yang Liu, Yan Sun
      Abstract: Abstract: The 39-amino acid peptide fragment derived from prostatic acidic phosphatase (PAP), PAP248-286, is secreted in large amount into human semen and form amyloid fibrils. The fibrils can capture HIV virions and increase the attachment of virions to target cells, so they are called semen-derived enhancer of virus infection (SEVI). Therefore, it is of significance to inhibit the formation of PAP248-286 amyloid fibrils. Herein, we have demonstrated that brazilin could effectively inhibit PAP248-286 aggregation. The inhibition effect increased with increasing brazilin concentration. Thioflavin T fluorescence assays and transmission electron microscopic observations proved that few fibrils formed when brazilin was present with PAP248-286 in an equimolar concentration. Circular dichroism spectra indicated that brazilin inhibited the secondary structural transitions from α-helix and random coils to β-sheet. Cytotoxicity assays showed that brazilin significantly reduced the fibrils cytotoxicity at 0.01 mmol/L. Isothermal titration calorimetry revealed that hydrophobic interaction was the main force for brazilin binding to PAP248-286 monomer (dissociation constant, 4.03 μmol/L), and brazilin binding affinity for its fibrils was at least three orders of magnitude lower than for the monomer. The results indicate that brazilin would be a potential small molecule agent against SEVI.
      PubDate: 2017-03-16T23:40:39.738792-05:
      DOI: 10.1002/asia.201700058
       
  • Synthesis of Silyl Cobalt Hydride and its Catalytic Performance in Kumada
           Coupling Reactions
    • Authors: Hongjian Sun; Peng Zhang, Xiaoyan Li, Benjing Xue, Hongjian Sun, Olaf Fuhr, Dieter Fenske
      Abstract: Abstract:In this paper, we reported the syntheses of four silyl [P,Si]-chelate cobalt complexes (2-5) through the chelate-assisted Si-H activation of bidentate preligand o-HSi(Me)2(PPh2)C6H4(1) with CoMe(PMe3)4 and CoCl(PMe3)3. The silyl Co(I) complex, Co(PMe3)3(1-Si(Me)2-2-(PPh2)C6H4) (2), was synthesized by Si-H activation of 1 with CoMe(PMe3)4 or the combination of complex 5 with MeLi and PMe3. Complex 2 was treated with CH3I or EtBr and generating the silyl Co(II) products CoI(PMe3)2(1-Si(Me)2-2-(PPh2)C6H4) (3) and CoBr(PMe3)2(1-Si(Me)2-2-(PPh2)C6H4) (4). The silyl Co(III) hydride, CoHCl(PMe3)2(1-Si(Me)2-2-(PPh2)C6H4) (5), was obtained by the reaction of complex 1 with CoCl(PMe3)3.The catalytic performance of complex 5 was explored for the Kumada coupling reactions. With a load of 2mol% of catalyst, complex 5 displayed good to excellent catalytic efficiency for the reactions of aryl chlorides or aryl bromides with Grignard reagents. It is noteworthy that the synthesis of 5 as a chelate complex is easier than that of our early reported [PSiP]-pincer cobalt hydride.With similar catalytic efficiency for the Kumada reactions, the catalyst loading (2%) of 5 is lower than that (5%) of [PSiP]-pincer cobalt hydride.
      PubDate: 2017-03-16T06:41:33.473899-05:
      DOI: 10.1002/asia.201700144
       
  • Efficient Color-Tunable Copper(I) Complexes and Their Applications in
           Solution-Processed Organic Light-Emitting Diodes
    • Authors: Gary Kwok-Ming So; Gang Cheng, Jian Wang, Xiaoyong Chang, Chi-Chung Kwok, Hongxing Zhang, Chi-Ming Che
      Abstract: A series of dppnc- and neocuproine-based CuI complexes (dppnc=7,8-bis(diphenylphosphino)-7,8-dicarba-nido-undecaborate) are synthesized and the emission color of these CuI complexes can be tuned from green to deep red via rational modification of the neocuproine ligand structure. The molecular structures of the emissive CuI complexes, Cu(dppnc)-G (green emitting), Cu(dppnc)-Y (yellow emitting), and Cu(dppnc)-R (red emitting), are characterized and their electronic structures and related transition properties are elucidated by photo-physical and computational (density functional theory) studies. The calculation results suggest that thermally activated delayed fluorescence (TADF) is the emission mechanism for these CuI complexes. Efficient solution-processed green-, yellow-, and red-emitting OLEDs are fabricated based on the emissive complexes as the dopants. High external quantum efficiency (EQE) of 15.20 % and current efficiency of 48.15 cd A−1 at 1000 cd m−2 are achieved in the green-emitting device with Cu(dppnc)-G. A maximum EQE of 10.17 %, CIE coordinates of (0.61, 0.38) and a maximum electroluminescent peak of 631 nm are achieved in the red device based on Cu(dppnc)-R.OLED School Reggae: The emission color of dppnc- and neocuproine-based CuI complexes are tuned from green to deep red via rational modification of the neocuproine ligand structure. EQE of 15.20 % and a current efficiency of 48.15 cd A−1 at 1000 cd m−2 are achieved in the green-emitting device with Cu(dppnc)-G. A maximum EQE of 10.17 % and a maximum electroluminescent peak of 631 nm are achieved in the red device based on Cu(dppnc)-R.
      PubDate: 2017-03-10T10:28:09.035056-05:
      DOI: 10.1002/asia.201700081
       
  • Sequential Functionalization of a Natural Crosslinker Leads to Designer
           Silicone Networks
    • Authors: Scott E Laengert; Alyssa F Schneider, Yang Chen, Michael A Brook
      Abstract: Abstract: Precise silicone networks are difficult to prepare from multiple starting materials because of poor special control over crosslink location, competing side reactions, and incompatible catalysts among other reasons. We demonstrate that cure processes catalyzed by B(C6F5)3 (the Piers-Rubinsztajn reaction) and platinum-catalyzed hydrosilylation are perfectly compatible, and can be used in either order. It is possible to perform three different, selective, sequential reactions in the same pot using H-terminated silicones as chain extenders in all cases to give explicit networks. Eugenol, a readily available aromatic compound, acts as trifunctional crosslinker (HO, MeO, HC=CH2), each functional group of which can be induced to undergo selective reaction. With platinum catalysis, the reaction of SiH groups with alkenes is fastest, while B(C6F5)3 catalyzes reaction at phenols much faster than methoxybenzene; hydrosilylation of the alkene was not catalyzed by B(C6F5)3 under these conditions. Thus, a variety of H-terminated telechelic siloxanes can be used to form chain extended polymers, or elastomers or foams in which the morphology of the material and its constituent parts can be manipulated at will. The resulting elastomers proved to be surprisingly resistant to hydrolysis.
      PubDate: 2017-03-10T01:27:06.682031-05:
      DOI: 10.1002/asia.201700160
       
  • Tightly bound double-caged [60]fullerene derivatives with enhanced
           solubility: structural features and application in solar cells
    • Authors: Victor A. Brotsman; Vitaliy A. Ioutsi, Alexey V. Rybalchenko, Vitaliy Yu. Markov, Nikita M. Belov, Natalia S. Lukonina, Sergey I. Troyanov, Ilya N. Ioffe, Vasiliy A. Trukhanov, Galina K. Galimova, Artur A. Mannanov, Dmitry N. Zubov, Erhard Kemnitz, Lev N Sidorov, Tatiana V. Magdesieva, Dmitry Yu. Paraschuk, Alexey A Goryunkov
      Abstract: A series of novel highly soluble double-caged [60]fullerene derivatives were prepared by means of lithium salt-assisted [2+3]-cycloaddition. The bispheric molecules feature rigid linking of the fullerene spheres via a four-membered cycle and a pyrrolizidine bridge with an ester function CO2R (R=n-decyl, n-octadecyl, benzyl, and n-butyl: compounds 1a-d, respectively), as demonstrated by NMR spectroscopy and X-ray diffraction. Cyclic voltammetry studies revealed three closely overlapping pairs of reversible peaks due to consecutive one-electron reductions of fullerene cages, as well as an irreversible oxidation peak attributed to abstraction of an electron from the nitrogen lone electron pair. Due to charge delocalization over both carbon cages, compounds 1a-d are characterized by upshifted energies of frontier molecular orbitals, narrowed band gap, and reduced electron transfer reorganization energy compared to pristine C60. Neat thin films of the n-decyl compound 1a demonstrated the electron mobility (1.3 ± 0.4)×10-3 cm2V-1s-1, comparable to PCBM and thus potentially advantageous for organic solar cells (OSC). An application of compounds 1 in OSC allowed a two-fold increase in power conversion efficiencies of as-cast P3HT/1 devices compared to the P3HT/PCBM ones. This is attributed to good solubility of 1 and their enhanced charge transport properties, both intramolecular, due to tightly linked fullerene cages, and intermolecular, due to large number of close contacts between the neighboring double-caged molecules. Test P3HT/1 OSCs demonstrated power conversion efficiencies up to 2.6% (1a). Surprisingly low optimal content of double-caged fullerene acceptor 1 in the photoactive layer (ca 30 wt%) favored better light harvesting and carrier transport due to larger content of P3HT and its higher degree of crystallinity.
      PubDate: 2017-03-09T14:30:29.36442-05:0
      DOI: 10.1002/asia.201700194
       
  • Insertion of Group 12-16 Hydrides into NHCs: A Theoretical Investigation
    • Authors: Kalon J Iversen; Jason L Dutton, David Wilson
      Abstract: The endocyclic ring expansion of N-heterocyclic carbene (NHC) rings by transition metal (Group 12) and main group (Group 13-16) element hydrides has been investigated in a computational study. In addition to previously reported insertion reactivity with Si, B, Be and Zn, similar reactivity is predicted to be feasible for heavier group 13 elements (Al, Ga, In, Tl), with the reaction barriers for Al-Tl calculated to be lower than for boron. Insertion is not expected with group 15-16 element hydrides, as the initial adduct formation is thermodynamically unfavourable. The reaction pathway with group 12 hydrides is calculated to be more favourable with two NHCs rather than a single NHC (analogous to Be), however hydride ring insertion with metal dihydrides is not feasible, but rather a reduced NHC is thermodynamically favoured. For group 14, ring-insertion reactivity is predicted to be feasible with the heavier dihydrides. Trends in reactivity of element hydrides may be related to the protic or hydridic character of the element hydrides.
      PubDate: 2017-03-06T23:15:27.230773-05:
      DOI: 10.1002/asia.201700082
       
  • Water-Solubilization of Fullerene Derivatives by β-(1,3-1,6)-D-Glucan and
           Their Photodynamic Activities toward Macrophages
    • Authors: Atsushi Ikeda; Tatsuya Iizuka, Naotake Maekubo, Kazuyuki Nobusawa, Kouta Sugikawa, Kazuya Koumoto, Toshio Suzuki, Takeshi Nagasaki, Motofusa Akiyama
      Abstract: Anionic and neutral fullerene derivatives were dissolved in water by β-(1,3-1,6)-D-glucan (β-1,3-glucan) as a solubilizing agent. In the water-solubilized complexes, the concentrations of fullerene derivatives were ca. 0.30 mM and the average particle sizes were ca. 90 nm. The β-1,3-glucan complexed fullerene derivative with a carboxylic acid was found to have higher photodynamic activity toward macrophages under visible-light irradiation (λ> 610 nm) when compared with that of other β-1,3-glucan-complexed fullerene derivatives. This result suggests that carboxylic acid moieties in the complex enhance the binding affinity with β-1,3-glucan-receptors on the surface of macrophages when β-1,3-glucan is recognized. In contrast, all β-1,3-glucan complexed fullerene derivatives showed no photodynamic activity toward HeLa cells under the same conditions.
      PubDate: 2017-03-06T22:20:45.314877-05:
      DOI: 10.1002/asia.201700182
       
  • Dihydrogen Splitting Using Dialkylsilylene-Based Frustrated Lewis Pairs
    • Authors: Zhaowen Dong; Zhifang Li, Xupeng Liu, Chenting Yan, Ningka Wei, Mitsuo Kira, Thomas Müller
      Abstract: Isolable dialkylsilylene 5 reacts with dihydrogen in the presence of a small amount of a conventional Lewis acid (BPh3, BEt3) or a base (PPh3, PEt3, NPh3, NEt3) at low temperatures in a hydrocarbon solvent, giving the corresponding dihydrosilane 10 in high yields. Both 5/Lewis acid and Lewis base/5 pairs work as a frustrated Lewis pair (FLP) to split dihydrogen, being in accord with the amphoteric nature of silylene 5.Splitting up based on frustration: Amphoteric dialkylsilylene 5 that forms frustrated Lewis pairs (FLPs) with either a Lewis acid or base splits dihydrogen at low temperatures in hexane giving the corresponding dihydrosilane 10 in high yields.
      PubDate: 2017-03-01T03:25:33.827188-05:
      DOI: 10.1002/asia.201700143
       
  • Molecular Oligogermanes and Related Compounds: Structure, Optical and
           Semiconductor Properties
    • Authors: Kirill V. Zaitsev; Viktor A. Tafeenko, Yuri F. Oprunenko, Anastasia V. Kharcheva, Zhaisan Zhanabil, Yerlan Suleimen, Kevin Lam, Vladimir B. Zaitsev, Anna V. Zaitseva, Galina S. Zaitseva, Sergey S. Karlov
      Abstract: The optical (UV/Vis absorbance, fluorescence in the solid state and in solution) and semiconducting properties of a number of di- and trigermanes as well as related silicon- and tin-containing germanes, 1–6 ((p-Tol)3GeGeMe3 (1), Ph3SnGe(SiMe3)3 (2), (C6F5)3GeGePh3 (3), (p-Tol)3GeSiMe2SiMe3 (4), (p-Tol)3GeGeMe2Ge(p-Tol)3 (5), (p-Tol)3GeSiMe2SiMe2Ge(p-Tol)3 (6)) were investigated. Molecular structures of 5 and 6 were studied by X-ray diffraction analysis. All compounds displayed luminescence properties. In addition, a band gap (of about 3.3 eV) was measured for compounds 1–6 showing that those molecules display semiconductor properties.Semiconducting molecular oligogermanes: A series of molecular catenated group 14 derivatives was obtained and their structure, optical (UV/Vis absorbance, luminescence) and electrochemical properties were studied. A band gap of about 3.3 eV was measured for such compounds, indicating that these molecules have semiconductor properties.
      PubDate: 2017-02-28T07:21:21.669681-05:
      DOI: 10.1002/asia.201700151
       
  • Silole Silylene Route to NHC-Stabilized Fused 1-Silabicylcles and
           1,1'-Spirobisiloles
    • Authors: Chunming Cui; Tianhao Li, Jianying Zhang
      Abstract: The reaction of an NHC-stabilized silole silylene (1-silacyclopentadienylidene) with one equivalent of internal acetylenes resulted in the formation of NHC stabilized 1-silabicyclo[3.2.0]hepta-1,3,6-trienes, which subsequently reacted with one equivalent of the acetylene to give aryl-substituted 1,1'-spirobisilole (SBS). The SBSs can be alternatively prepared by the reaction of the NHC-stabilized silole silylene with two equivalents of the acetylenes in good yields. The electronic structures of these SBSs have been studied by UV-vis and emission spectroscopy as well as DFT calculations.
      PubDate: 2017-02-24T00:20:25.110337-05:
      DOI: 10.1002/asia.201700050
       
  • Stereoisomerization of Cyclic Silanols
    • Authors: Hisayuki Endo; Nobuhiro Takeda, Masafumi Unno
      Abstract: Stereoisomerization of readily available all-cis-1,3,5,7-tetrahydroxy-1,3,5,7-tetraisobutylcyclotetrasiloxane (1a) was carried out in acidic condition to afford cis-trans-cis (1b), all-trans (1c), and cis-cis-trans (1d) isomers. Reaction mixture could be easily separated into 1a and a mixture of 1b, 1c, and 1d by the treatment with chloroform. Mixture of 1b, 1c, and 1d were further isolated and each structure was identified. The experimental results indicated that the most of plausible mechanism is substitution reaction of silicon center via pentacoordinate intermediate without cyclic siloxane bond cleavage reaction. Obtained isomer 1a or 1b was further reacted with dichlorodiphenylsilane in the presence of triethylamine to give syn-type laddersiloxane (2a) or anti-type laddersiloxane (2b), respectively.
      PubDate: 2017-02-22T04:21:01.710191-05:
      DOI: 10.1002/asia.201700125
       
  • Towards organic zeolites and inclusion catalysts: heptazine imide salts
           can exchange metal cations in the solid state
    • Authors: Markus Antonietti; Aleksandr Savateev, Sergey Pronkin, Marc Willinger, Dariya Dontsova
      Abstract: Highly crystalline potassium (heptazine imides) were prepared by the thermal condensation of substituted 1,2,4-triazoles in eutectic salt melts. These semiconducting salts are already known to be highly active photocatalysts, e.g. for the visible light driven generation of hydrogen from water. Herein, we show that within the solid state structure, potassium ions can be exchanged to other metal ions while the crystal habitus is essentially preserved.
      PubDate: 2017-02-15T11:00:40.614146-05:
      DOI: 10.1002/asia.201700209
       
 
 
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