for Journals by Title or ISSN
for Articles by Keywords
help
  Subjects -> CHEMISTRY (Total: 852 journals)
    - ANALYTICAL CHEMISTRY (52 journals)
    - CHEMISTRY (598 journals)
    - CRYSTALLOGRAPHY (21 journals)
    - ELECTROCHEMISTRY (25 journals)
    - INORGANIC CHEMISTRY (41 journals)
    - ORGANIC CHEMISTRY (46 journals)
    - PHYSICAL CHEMISTRY (69 journals)

CHEMISTRY (598 journals)                  1 2 3 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 10)
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: 38)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 18)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 24)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 39)
ACS Nano     Full-text available via subscription   (Followers: 252)
ACS Photonics     Full-text available via subscription   (Followers: 12)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 23)
Acta Chemica Iasi     Open Access   (Followers: 2)
Acta Chimica Sinica     Full-text available via subscription   (Followers: 1)
Acta Chimica Slovaca     Open Access   (Followers: 1)
Acta Chimica Slovenica     Open Access  
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: 8)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 5)
Advanced Functional Materials     Hybrid Journal   (Followers: 51)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 57)
Advances in Chemical Science     Open Access   (Followers: 13)
Advances in Chemistry     Open Access   (Followers: 15)
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: 9)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 16)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 9)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 21)
Advances in Nanoparticles     Open Access   (Followers: 15)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15)
Advances in Polymer Science     Hybrid Journal   (Followers: 41)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Science and Technology     Full-text available via subscription   (Followers: 12)
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)
Al-Kimia : Jurnal Penelitian Sains Kimia     Open Access  
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: 66)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 15)
American Journal of Chemistry     Open Access   (Followers: 27)
American Journal of Plant Physiology     Open Access   (Followers: 14)
American Mineralogist     Hybrid Journal   (Followers: 14)
Analyst     Full-text available via subscription   (Followers: 39)
Angewandte Chemie     Hybrid Journal   (Followers: 179)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 229)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 4)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 4)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 8)
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: 16)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal   (Followers: 1)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7)
Applied Spectroscopy     Full-text available via subscription   (Followers: 22)
Applied Surface Science     Hybrid Journal   (Followers: 28)
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: 4)
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: 10)
Biochemistry     Full-text available via subscription   (Followers: 326)
Biochemistry Insights     Open Access   (Followers: 6)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 9)
Bioinspired Materials     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 1)
Biomacromolecules     Full-text available via subscription   (Followers: 19)
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: 5)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 120)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 85)
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: 3)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 3)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 5)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 68)
Catalysis for Sustainable Energy     Open Access   (Followers: 7)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 7)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 8)
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 5)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 15)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 70)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 25)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 21)
Chemical Reviews     Full-text available via subscription   (Followers: 184)
Chemical Science     Open Access   (Followers: 22)
Chemical Technology     Open Access   (Followers: 16)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemical Week     Full-text available via subscription   (Followers: 8)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 56)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 24)
ChemInform     Hybrid Journal   (Followers: 8)
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: 146)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 20)
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: 42)
Chemistry of Materials     Full-text available via subscription   (Followers: 246)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 22)
Chemistry-Didactics-Ecology-Metrology     Open Access   (Followers: 1)
ChemistryOpen     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 4)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 14)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 10)
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: 24)
Clay Minerals     Full-text available via subscription   (Followers: 10)
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: 6)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 19)
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: 11)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 3)
Copernican Letters     Open Access   (Followers: 1)
Corrosion Series     Full-text available via subscription   (Followers: 6)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Croatica Chemica Acta     Open Access  
Crystal Structure Theory and Applications     Open Access   (Followers: 4)
CrystEngComm     Full-text available via subscription   (Followers: 13)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Metabolomics     Hybrid Journal   (Followers: 5)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Opinion in Molecular Therapeutics     Full-text available via subscription   (Followers: 18)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 64)
Dalton Transactions     Full-text available via subscription   (Followers: 23)
Detection     Open Access   (Followers: 2)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)
Diamond and Related Materials     Hybrid Journal   (Followers: 12)
Dislocations in Solids     Full-text available via subscription  
Doklady Chemistry     Hybrid Journal  
Drying Technology: An International Journal     Hybrid Journal   (Followers: 4)
Eclética Química     Open Access   (Followers: 1)
Ecological Chemistry and Engineering S     Open Access   (Followers: 3)
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  

        1 2 3 | Last

Journal Cover Chemistry - A European Journal
  [SJR: 2.323]   [H-I: 188]   [146 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0947-6539 - ISSN (Online) 1521-3765
   Published by John Wiley and Sons Homepage  [1589 journals]
  • Rates of chemical reactions embedded in a metabolic network by dissolution
           dynamic nuclear polarization NMR
    • Authors: aude sadet; Emmanuelle Weber, Aditya Jhajharia, Dennis Kurzbach, Geoffrey Bodenhausen, Emeric Miclet, Daniel Abergel
      Abstract: The isomerisation of 6-phosphogluconolactones and their hydrolyses into 6-phosphogluconic acid form a non enzymatic side cycle of the pentose-phosphate pathway (PPP) in cells. We show that dissolution dynamic nuclear polarization can be used for determining its kinetic rates in real time. It is found that the hydrolysis of both lactones is significantly slower than the isomeration process, thereby shedding new light onto this subtle and puzzling chemical process.
      PubDate: 2018-01-22T03:28:53.797761-05:
      DOI: 10.1002/chem.201705520
       
  • Complexes of Stiboranium Mono-, Di-and Tri-cations
    • Authors: Neil Burford; Christopher Frazee, Robert McDonald, Michael Ferguson, Brian Patrick, Andreas Decken
      Abstract: Reaction of Ph2SbCl3 with 2,2'-bipyridine and Me3SiOSO2CF3 releases chlorobenzene, which is interpreted as a reductive (SbV/SbIII) elimination from a cationic complex of a stiboranium cation. Conversely, reactions of Ph2SbCl3 with 4-methylpyridine-N-oxide and AgOSO2CF3 give redox resistant complexes with the generic formulae [Ph2SbCl3-xLx+1][OTf]x, including a compound containing the first example of a pnictogen(V) trication.
      PubDate: 2018-01-22T03:24:43.090226-05:
      DOI: 10.1002/chem.201800196
       
  • Recent Advances in the Synthesis of Peptoid Macrocycles
    • Authors: Alexandra M Webster; Steven Lorimer Cobb
      Abstract: Over the past two decades, developing medical applications for peptides has, and continues to be a highly active area of research. At present there are over 60 peptide-based drugs on the market and more than 140 in various stages of clinical trials. The interest in peptide-based therapeutics arises from their biocompatibility and their ability to form defined secondary and tertiary structures, resulting in a high selectivity for complex targets. However, there are significant challenges associated with the development of peptide-based therapeutics, namely peptides are readily metabolised in vivo. Peptoids are an emerging class of peptidomimetic and they offer an alternative to peptides. Peptoids are comprised of N-substituted glycines where side-chains are located on the nitrogen atom of the amide backbone rather than the α-carbon as is the case in peptides. This change in structure confers a high degree of resistance to proteolytic degradation but the absence of any backbone hydrogen bonding means that peptoids exhibit a high degree of conformational flexibility. Cyclisation has been explored as one possible route to rigidify peptoid structures, making them more selective, and, therefore more desirable as potential therapeutics. This review outlines the various strategies that have been developed over the last decade to access new types of macrocyclic peptoids.
      PubDate: 2018-01-22T03:24:39.072711-05:
      DOI: 10.1002/chem.201705340
       
  • Recent Advances in Germanium-Based Photoinitiator Chemistry
    • Authors: Harald Stueger; Michael Haas, Judith Radebner, Anna Eibel, Georg Gescheidt
      Abstract: Acylgermanes provide an outstanding photo-induced reactivity at highly useful absorption wavelengths. This encouraged multidisciplinary research groups to utilize them as highly effective and non-toxic photoinitiators for, particularly medical applications. In this minireview, we present the most recent breakthroughs to synthesize acylgermanes. We also outline mechanistic aspects of photo-induced reactions of several acylgermane derivatives based on fundamental spectroscopic insights. These studies may aid future developments for tailor-made photoinitiators.
      PubDate: 2018-01-22T03:24:02.117258-05:
      DOI: 10.1002/chem.201705567
       
  • Crystal field in rare-earth complexes: From electrostatics to bonding.
    • Authors: Hélène Bolvin; Riccardo Alessandri, Habiburrahman Zulfikri, Jochen Autschbach
      Abstract: We take advantage of the flexibility of first principles (ab initio) calculations with the SO-CASSCF method to quantify the electrostatic and covalent contributions to Crystal Field Parameters. Two types of systems are chosen for illustration; i) The ionic and experimentally well-characterized PrCl3 crystal. This study permits to revisit the partition of contributions proposed in the early days of Crystal Field Theory. ii) A series of sandwich molecules [Ln(eta^n-CnHn)2]q with Ln= Dy, Ho, Er, Tm and n=5,6,8 where the interaction between the Ln(III) and the aromatic ligands is more difficult to describe within an electrostatic approach. It is shown that a model with three layers of charges reproduces the electrostatic field generated by the ligands and that the covalency plays a qualitative role. The one-electron character of the Crystal Field Theory is discussed and shown to be valuable, even through it is not completely quantitative. This permits to reduce the many-electron problem to the discussion of the energy of the seven 4f orbitals.
      PubDate: 2018-01-22T03:22:12.886386-05:
      DOI: 10.1002/chem.201705748
       
  • Electron Injection Promoted High Oxygen Evolution Activity of Co-Ni Alloy
           Nanochains
    • Authors: Xiaotao Yuan; Muhammad Sohail Riaz, Xin Wang, Chenlong Dong, Zhe Zhang, Fu-Qiang Huang
      Abstract: Abstract: Metal alloy nanoparticles have shown promising applications in electrocatalysis. However, the nanoparticles usually suffer from limited charge transfer efficiency, which can be solved by preparing one-dimensional materials. In this work, Co-Ni alloy nanochains are prepared by a direct-current arc-discharge method. The nanochains, comprised of uniform nanospheres coupled to each other, can range up to several micrometers. When the alloy is exposed to the air or under the electro oxidation process, a metal-metal oxide heterostructure is obtained. The alloy can inject electrons into oxide which manipulates the work function of the oxide and makes it more apposite for electrocatalysis. The composition of the samples can be changed by varying the ratio of Ni/Co (Co, Co7Ni3, Co5Ni5, Co3Ni7, Ni) in the synthesis process. The nanochains show good oxygen evolution performance which is reliant on the proportion of Ni/Co. The Co7Ni3 illustrates the optimal activity with an onset point of 1.50 V (vs. RHE) and overpotential of 350 mV at 10 mA cm-2. The alloy nanochains also show excellent durability with 95.0% current retention after a long-term test for 12 hours.
      PubDate: 2018-01-22T03:22:04.157818-05:
      DOI: 10.1002/chem.201800044
       
  • Frontispiece: Low Molecular Weight Supramolecular Gels Under Shear:
           Rheology as the Tool for Elucidating Structure–Function Correlation
    • Authors: Arnab Dawn; Harshita Kumari
      Abstract: Rheological studies on supramolecular gel phase materials offer an extensive insight of the structure-function relationship lies in assembly properties of the molecules participated. The outcome of rheological experiments becomes even more interpretive when a concurrent experiment like rheo-optics is performed. The review by A. Dawn and H. Kumari on page 762 ff. gives a comprehensive picture of rheology-based research on supramolecular gel phase materials, and shows the path to rationalize the behaviors of healable and non-healable supramolecular gel systems based on the interplay between molecular and supramolecular domains.
      PubDate: 2018-01-19T05:53:56.294671-05:
      DOI: 10.1002/chem.201880462
       
  • Frontispiece: Reduction of Carbonyl Groups by Uranium(III) and Formation
           of a Stable Amide Radical Anion
    • Authors: Kimberly C. Mullane; Thibault Cheisson, Eiko Nakamaru-Ogiso, Brian C. Manor, Patrick J. Carroll, Eric J. Schelter
      Abstract: Reduction of organic ketones, esters and amides by UIII[N(SiMe3)2]3 resulted in a variety of uranium(IV) compounds. The fates of the organic fragments ranged from reversible radical coupling, to bond cleavage, group transfer or one-electron reduction. In particular, the first example of a stable, charge-separated amide radical was established, supported by magnetic, UV-Vis-NIR, electrochemical and EPR measurements, as well as computational studies. For more details see the Full Paper by E. J. Schelter et al. on page 826 ff.
      PubDate: 2018-01-19T05:53:55.063122-05:
      DOI: 10.1002/chem.201880464
       
  • Frontispiece: Amino Acid Coordinated Self-Assembly
    • Authors: Qianli Zou; Xuehai Yan
      Abstract: A new strategy for supramolecular chemistry, amino acid coordinated self-assembly paves the way for constructing hierarchical materials by using basic units of biomolecules as the building blocks. Similar to other supramolecular self-assembly strategies, the morphologies and architectures of the micro- and nanomaterials fabricated from amino acid coordinated self-assembly can be readily tuned by changing the types, ratios, and concentrations of the building blocks along with the metal ions. For more information see the Concept article by Q. Zou and X. Yan on page 755 ff.
      PubDate: 2018-01-19T05:53:52.174193-05:
      DOI: 10.1002/chem.201880461
       
  • Frontispiece: Pillar[5]arene-Based Supramolecular Organic Framework with
           Multi-Guest Detection and Recyclable Separation Properties
    • Authors: Qi Lin; Yan-Qing Fan, Peng-Peng Mao, Lu Liu, Juan Liu, You-Ming Zhang, Hong Yao, Tai-Bao Wei
      Abstract: The supramolecular organic framework (SOF-THBP) with multi-guest detection and recyclable separation properties, constructed by bis-thioacetylhydrazine-functionalized pillar[5]arenes, shows fluorescent response for Fe3+, Cr3+, Hg2+ and Cu2+. In addition, the xerogel of SOF-THBP shows excellent recyclable separation properties for these metal ions. By introducing these metal ions into the SOF-THBP, a series of metal ions coordinated SOFs (MSOF) were constructed. These MSOF could selectively and sensitively sense F−, Br−, and l-Cys, respectively. For more details, see the Communication by Q. Lin et al. on page 777 ff.
      PubDate: 2018-01-19T05:53:45.702183-05:
      DOI: 10.1002/chem.201880463
       
  • Rational Design of Organically Functionalized Polyoxopalladates and Their
           Supramolecular Properties
    • Authors: Peng Yang; Hui Li, Tian Ma, Fadi Haso, Tianbo Liu, Linyuan Fan, Zhengguo Lin, Changwen Hu, Ulrich Kortz
      Abstract: The SrII-centered 12-palladate(II) open-cube {SrPd12(OAc)3} has been systematically evolved by substitution of the three acetate ligands by a library of saturated carboxylic acids with increasing chain lengths leading to four novel polyoxopalladates(II) with the formula [SrPd12O6(OH)3(PhAsO3)6(L)3]4− (SrPd12L3, L=CnH2n+1COO, n=2 to 5). These first examples of surfactant-type polyoxopalladates with a hydrophilic metal-oxo unit and three hydrophobic alkyl chains were characterized in the solid state (single-crystal XRD, FTIR, TGA), in solution (1H, 13C NMR spectroscopy), and in the gas phase (ESI-MS). The two polyanions SrPd12L3 with chain lengths of 5 and 6 are the first examples of polyoxopalladates that are soluble and stable in organic media. The Na salts of the amphiphilic polyoxopalladates SrPd12L3 were shown to self-assemble into “blackberry”-type spherical supramolecular structures in dilute solutions, of which an unusual “volcano”-shaped trend of assembly size versus solvent polarity is chiefly influenced by directional hydrogen bonding interactions.Polyoxometalates: Four surfactant-type polyoxo-12-palladates(II) SrPd12L3 with three carboxylate ligands L (chain lengths from 3 to 6) were prepared, resulting in discrete polyanions, which exhibit aqueous and organic solubility and unprecedented supramolecular interactions.
      PubDate: 2018-01-19T04:35:48.877918-05:
      DOI: 10.1002/chem.201705303
       
  • The Rickiols: 20-, 22-, and 24-membered Macrolides from the Ascomycete
           Hypoxylon rickii
    • Authors: Frank Surup; Eric Kuhnert, Andreas Böhm, Tim Pendzialek, Danny Solga, Vincent Wiebach, Hauke Engler, Albrecht Berkessel, Marc Stadler, Markus Kalesse
      Abstract: In preceding studies the neotropical ascomycete Hypoxylon rickii turned out to be a prolific source of new secondary metabolites, considering that we had obtained terpenoids with five different scaffolds along with a series of terphenyls. From the mycelial extracts of a 70 L scale fermentation of this strain we additionally isolated nine new macrolides (1–9) by RP-HPLC. The planar structures were elucidated by NMR spectroscopy complemented by HR-ESIMS. The relative configurations were assigned by J-based configuration analyses and confirmed by Kishi′s Universal Database. Subsequently, the absolute configurations were assigned by Mosher′s method using the shift analysis of a tetra-MTPA derivative. For rickiol A (1) and E (5) we observed transesterification of 20-membered ring structures to 22-membered isomers rickiol A2 (6) and E2 (7), and to 24-membered isomers rickiol A3 (8) and rickiol E3 (9), respectively. Cytotoxic effects and moderate antibiotic activity against Gram-positive bacteria were observed for 1–8 and 1–6 and 8, respectively. The total synthesis of rickiol E3 (9) established easier access to these compounds.Meet the Rickiols: If one solvent does not work for structure elucidation, then try another! To determine the stereo configuration of 20-, 22-, and 24-membered macrolactones through J-based analysis, the solvent had to be changed twice. Comprehensive analysis was confirmed with Kishi′s Universal Database, and finalized by Mosher′s method. The total synthesis of one representative confirmed the assignment.
      PubDate: 2018-01-19T04:34:27.708778-05:
      DOI: 10.1002/chem.201704928
       
  • Synthesis and Dimerization Studies of a Lipophilic Photoresponsive
           Aryl-Extended Tetraurea-Calix[4]pyrrole
    • Authors: Ryo Sekiya; Alejandro Díaz-Moscoso, Pablo Ballester
      Abstract: We describe the syntheses of the lipophilic aryl-extended α,α,α,α-tetraurea-phenyl-calix[4]pyrrole 1, featuring four appended azo-phenyl groups with two tert-butoxy carbonyl meta-substituents and its photo-inactive counterpart 2. In CD2Cl2 solutions, both tetraurea-calix[4]pyrroles self-assemble into dimeric capsules by encapsulating one molecule of a suitable bis-N-oxide or two molecules of a mono-N-oxide. The dimeric capsules are mainly stabilized by a cyclic array of sixteen hydrogen bonds established between the eight unidirectionally oriented urea groups. Photoirradiation experiments demonstrated the trans-to-cis isomerization of the azo-phenyl groups and the formation of a plethora of stereo isomeric cis-azo-enriched capsular assemblies. The highly cis-azo enriched capsular assemblies seem to show a reduced stability and their involvement in equilibria with non-capsular counterparts that also bind the N-oxides. The thermally induced cis-to-trans interconversion processes demonstrated the reversibility of the photoisomerization and the photostability of most binding partners. An equimolar mixture of the two tetraureas produced two homodimeric capsules and the heterodimeric counterpart in a ratio close to statistical distribution.An aryl extension in light: The syntheses of a lipophilic aryl-extended α,α,α,α-tetraurea-phenyl-calix[4]pyrrole, and its photo-inactive counterpart are reported. Both tetraureas self-assemble into dimeric capsules by encapsulating one molecule of a bis-N-oxide or two molecules of mono-N-oxide. The results of light irradiation experiments performed with the photoresponsive homo- and heterocapsules are described.
      PubDate: 2018-01-19T04:33:41.051397-05:
      DOI: 10.1002/chem.201704777
       
  • Nitrite Reduction in Aqueous Solution Mediated by Amavadin Homologues: N2O
           Formation and Water Oxidation
    • Authors: Lúcia Dias; Nihel Bekhti, Dr Maxim L. Kuznetsov, Dr José A. B. Ferreira, Maria C. Bacariza, Dr José Armando L. da Silva
      Abstract: Reactions of two vanadium(IV) complex anions that are homologues of amavadin, [V(HIDPA)2]2− and [V(HIDA)2]2− (HIDPA=N-oxyiminodipropionate, HIDA=N-oxyiminodiacetate), with the nitrite ion (NO2−) in aqueous solution were investigated by experimental (absorption spectroscopy in the visible range, through measurements of dioxygen formed in solution from water oxidation and identification of nitrogen oxide species of a gaseous atmosphere from nitrite reduction by using an IR analyser) and theoretical methods. Two reactions, mediated by the vanadium complexes, with environmental and biological significance, were observed in this system, namely, reduction of nitrite to N2O and oxidation of water to molecular oxygen. The reduction of nitrite, as studied by DFT calculations, occurs through the formation of NO (ΔG≠=14.3 kcal mol−1), which is strongly dependent on pH and slightly endergonic, and is then easily converted into N2O, with an overall activation barrier of ΔG≠=11.8 kcal mol−1. The later process includes dimerisation of NO assisted by one molecule of the V complex, protonation and oxidation of the formed ONNO.− ligand by another amavadin molecule or by nitrite, and NO bond cleavage/proton transfer in the ONNOH− ligand. The results indicate that amavadin exhibits an unusual nitrite reductase type activity that could be involved in nitrogen metabolism of Amanita muscaria and other fungi containing this vanadium complex.Fungal metabolism: Reaction mechanisms of two vanadium(IV) complex anions that are homologues of amavadin, which is found in some fungi species, with NO2− in aqueous solution were investigated by experimental and theoretical methods. Direct nitrite reduction to N2O is unusual for reactions mediated by biomolecules and is a promoter of water oxidation (see scheme).
      PubDate: 2018-01-19T04:33:21.39303-05:0
      DOI: 10.1002/chem.201705385
       
  • Mono-Substituted Hydrocarbon Diastereomer Combinations Reveal Stapled
           Peptides with High Structural Fidelity
    • Authors: Fergus S. McWhinnie; Kristel Sepp, Charlotte Wilson, Tilo Kunath, Ted R. Hupp, Terry S. Baker, Douglas R. Houston, Alison N. Hulme
      Abstract: Modified peptides, such as stapled peptides, which replicate the structure of α-helical protein segments, represent a potential therapeutic advance. However, the 3D solution structure of these stapled peptides is rarely explored beyond the acquisition of circular dichroism (CD) data to quantify bulk peptide helicity; the detailed backbone structure, which underlies this, is typically undefined. Diastereomeric stapled peptides based on helical sections of three proteins (αSyn, Cks1 and CK1α) were generated; their overall helicity was quantified by CD; and the most helical peptide from each series was selected for structural analysis. Solution-phase models for the optimised peptides were generated using NMR-derived restraints and a modified CHARMM22 force field. Comparing these models with PDB structures allowed deviation between the stapled peptides and critical helical regions to be evaluated. These studies demonstrate that CD alone is not sufficient to assess the structural fidelity of a stapled peptide.Mix and match! Rapid and accessible protocol facilitates the identification of stapled peptides with backbone structures which replicate that of the parent protein with high fidelity. These techniques could be applied to any helical protein target enabling pre-validation of synthesized material before in vitro or in vivo analysis.
      PubDate: 2018-01-19T04:26:34.500719-05:
      DOI: 10.1002/chem.201705983
       
  • Direct and Enantioselective Synthesis of N−H-Free
           1,5-Benzodiazepin-2-ones by an N-Heterocyclic Carbene Catalyzed [3+4]
           Annulation Reaction
    • Authors: Chao Fang; Jing Cao, Kewen Sun, Jindong Zhu, Tao Lu, Ding Du
      Abstract: An NHC-catalyzed formal [3+4] annulation of α,β-unsaturated acylazoliums with protecting-group-free aryl 1,2-diamines was developed for a direct and highly enantioselective synthesis of 4-aryl N−H-free 1,5-benzodiazepin-2-ones. This methodology offers an efficient and rapid access to a wide range of enantioenriched target compounds from easily accessible starting materials. The protocol is also scalable and the desired products can easily undergo subsequent N-functionalization to afford diverse N-substituted derivatives. Additionally, a mechanism was proposed to explain the high enantioselectivity in this process.Get selective! An N-heterocyclic carbene catalyzed formal [3+4] annulation of α,β-unsaturated acylazoliums with protecting-group-free aryl 1,2-diamines was developed for a direct and highly enantioselective synthesis of 4-aryl N−H-free 1,5-benzodiazepin-2-ones (see scheme).
      PubDate: 2018-01-19T04:26:10.693014-05:
      DOI: 10.1002/chem.201705050
       
  • Experimental Observation of Thermally Excited Triplet States of Heavier
           Group 15 Element-Centered Diradical Dianions
    • Authors: Yong Fang; Li Zhang, Cheng Cheng, Yue Zhao, Manabu Abe, Gengwen Tan, Xinping Wang
      Abstract: One-electron reductions of Mes*As=Fl* (1; Fl* = 2,7-di-tert-butylfluorenylidene, Mes* = 2,4,6-tBu3C6H2) and diarsaalkenes [1,2-b]-IF(=AsMes*)2 (2; IF = indenofluorene) with potassium led to the isolation of the arsenic-centered radical anion salts 1K and 2K, respectively. The diradical dianion salts 2K2 and 3K2 were afforded by the reduction of 2 and 2,8-tBu2-[2,1-b]-IF(=AsMes*)2 (3) with an excess amount of KC8. The radicals have been investigated by single-crystal X-ray crystallography, EPR and UV-Vis absorption spectroscopy, along with theoretical calculations. The calculations revealed that 2K2 and 3K2 feature open-shell singlet ground states with singlet-triplet energy gaps of 2.1 and 1.0 kcal mol-1, respectively. They are readily to be thermally excited to triplet states as demonstrated by EPR spectroscopy. The obtained diradicals represent the first examples of heavier Group 15 element-centered diradicals with experimentally observable triplet states.
      PubDate: 2018-01-18T23:31:47.834741-05:
      DOI: 10.1002/chem.201706060
       
  • Synthesis and Structure of a Longitudinally Twisted Hexacene
    • Authors: Robert G. Clevenger; Bharat Kumar, Elizabeth M. Menuey, Kathleen Victoria Kilway
      Abstract: The addition of phenyllithium to a polycyclic quinone, 9,11,12,21,22,24-hexaphenyltetrabenzo[a,c,n,p]hexacene-10,23-di-one (10), followed by SnCl2-mediated reduction of the diol intermediate, yielded 9,10,11,12,21,22,23,24-octaphenyltetrabenzo-[a,c,n,p]hexacene (4). Crystallographic analysis of hexacene 4 showed it to possess a longitudinal twist of 184°, which was in good agreement with AM1 calculations. In addition to being the most twisted acene synthesized to this point, compound 4 contains within its substructure the most twisted naphthalene, anthracene, tetracene, and pentacene moieties described.
      PubDate: 2018-01-18T22:09:17.477127-05:
      DOI: 10.1002/chem.201705676
       
  • Synthesis of Single and Double Dibenzohelicenes via Rhodium-Catalyzed
           Intramolecular [2+2+2] and [2+1+2+1] Cycloadditions
    • Authors: Ryota Yamano; Yu Shibata, Ken Tanaka
      Abstract: Dibenzo[7]helicenes were synthesized with up to 99% ee via the rhodium(I)/binap complex-catalyzed enantioselective intramolecular [2+2+2] cycloaddition of 2-phenylnaphthalene-linked tryines. Additionally, [2+1+2+1] cycloaddition products, twisted anthracenes, were also synthesized by using difluorphos as a ligand. Although this compound is not configurationally stable at elevated temperature, the Scholl reaction of which afforded a configurationally stable double dibenzo[6]helicene. The thus obtained dibenzo[7]helicene exhibited good circularly polarized luminescence property and the double dibenzo[6]helicene exhibited high fluorescence quantum yield.
      PubDate: 2018-01-18T22:09:06.656836-05:
      DOI: 10.1002/chem.201706008
       
  • Exact Mapping from Many-Spin Hamiltonians to Giant-Spin Hamiltonians
    • Authors: Shadan Ghassemi Tabrizi; Alexei V Arbuznikov, Martin Kaupp
      Abstract: Exchange-coupled molecular spin clusters (e.g. single-molecule magnets) are routinely described in terms of a many-spin Hamiltonian (MSH) that considers individual spins, or a giant-spin Hamiltonian (GSH) that treats the system as a collective spin. When isotropic coupling is weak, the mapping MSH GSH ('spin projection'), becomes non-trivial due to mixing of spin multiplets by anisotropic terms, an effect crucial for generating transverse magnetic anisotropy. Going beyond perturbational spin-projection schemes, based on exact diagonalization and canonical effective Hamiltonian theory, we construct a GSH that exactly matches the energies of the relevant (2S+1) states. For comparison, we adapt a recently developed strategy for the unique definition of effective ('pseudospin') Hamiltonians of mononuclear systems, through adiabatic connection to a high-symmetry point in parameter space. The developed exact MSH GSH mapping is of importance for various weakly-coupled systems. An application to a Ni4 single-molecule magnet (S = 4) attributes the large tunnel splitting in the M = ± 4 ground doublet, responsible for fast magnetization tunneling, to a Stevens operator with eightfold rotational symmetry.
      PubDate: 2018-01-18T11:55:37.482625-05:
      DOI: 10.1002/chem.201705897
       
  • Rewiring chemical networks based on dynamic dithioacetal and disulfide
           bonds
    • Authors: Gaston Orrillo; Agustina La-Venia, Escalante Andrea, Ricardo L.E. Furlan
      Abstract: The control of the connectivity between nodes of synthetic networks is still largely unexplored. To address this point we take advantage of a simple dynamic chemical system with two exchange levels that are mutually connected and can be activated simultaneously or sequentially. Dithioacetals and disulfides can be exchanged simultaneously under UV light in the presence of a sensitizer. Crossover reactions between both exchange processes produce a fully connected chemical network. On the other hand, the use of acid, base or UV light connects different nodes allowing network rewiring.
      PubDate: 2018-01-18T09:25:25.143142-05:
      DOI: 10.1002/chem.201705654
       
  • Versatile Modes of Cooperative B-H Bond Activation Reactions in Ruthenium
           Carbene Complexes: Addition, Ring-opening and Insertion
    • Authors: Scharf T. Lennart; Julia Weismann, Kai-Stephan Feichtner, Felix Lindl, Viktoria H. Gessner
      Abstract: Cooperative B-H bond activation reactions with thio- and iminophosphoryl tethered ruthenium carbene complexes are reported. The complexes show surprisingly different reactivities towards the commonly employed boranes CatBH, PinBH and BH3∙LB as a result of different modes of metal ligand cooperation. While the iminophosphoryl system allows for selective 1,2-addition of the B-H bond across the Ru=C double bond, the sulfur analogue only delivers the 1,2-addition product for CatBH, while activation of BH3 and PinBH lead to further insertion reactions in one or more sides of the Ru-C-P-S-ring. The different reactivities can be explained by the differences in the electronics of the carbene complexes and the phosphoryl tether and by the Lewis acidities of the boranes. DFT calculations show that the mechanism of the reactions either proceeds via an addition across the Ru=C bond with different regioselectivities or across the Ru-S linkage.
      PubDate: 2018-01-18T09:00:39.135204-05:
      DOI: 10.1002/chem.201800248
       
  • Synthesis and Electric Properties of a Two-Dimensional Metal-Organic
           Framework Based on Phthalocyanine
    • Authors: Hisanori Nagatomi; Nobuhiro Yanai, Teppei Yamada, Kanji Shiraishi, Nobuo Kimizuka
      Abstract: Complexation of copper(II) 2,3,9,10,16,17,23,24-octahydroxy-29H,31H-phthalocyanine (CuPcOH) with copper(II) ions gives a two-dimensional (2D) metal-organic framework (MOF). This is the first report of a phthalocyanine-based MOF. This 2D MOF was obtained as a black powder and showed an electrical conductivity of 1.6×10−6 S cm−1 at 80 °C. When this MOF is used as a cathode of lithium ion battery (LIB), large charge/discharge capacities of 151/128 mAh g−1 were obtained. In addition, it showed a good stability during 200 charge/discharge cycles. The obtained LIB performance mainly originates from the electrically conductive and redox-active framework of the phthalocyanine-based 2D MOF and its hierarchical microporous/mesoporous structure.Complexation of the copper(II) phthalocyanine derivative, having four catechol moieties, with copper(II) ions gave a two-dimensional MOF with hierarchical micro/mesoporous structure. The redox-activity and conductivity of the framework rendered this Cu-CuPc MOF a unique cathode material for the lithium-ion battery system, showing large charge/discharge capacity with high cycle stability.
      PubDate: 2018-01-18T04:55:45.567216-05:
      DOI: 10.1002/chem.201705530
       
  • Remote C-H Activation of Various N-Heterocycles Using a Single Template
    • Authors: Guoqiang Yang; Dajian Zhu, Peng Wang, Ri-Yuan Tang, Jin-Quan Yu
      Abstract: A single simple ortho-sulfonyl benzonitrile template was developed to achieve remote C-H olefination of six different classes of N-heterocycles. We demonstrate that, by varying precatalysts and conditions, the same template can be applied to the remote C-H activation of six structurally distinct heterocyclic scaffolds, and the site-selectivity can be predicted based on distance and geometry. Furthermore, this new development shows that template-directed remote C-H activation are possible via macrocyclopalladation processes with smaller ring sizes.
      PubDate: 2018-01-18T03:55:24.764261-05:
      DOI: 10.1002/chem.201800105
       
  • Integration of open metal sites and Lewis basic sites for construction of
           a Cu MOF with rare chiral Oh type of cage for high performance of methane
           purification
    • Authors: Zhan Shi; Lingkun Meng, Ziyuan Niu, Chen Liang, XingLong Dong, Kang Liu, Guanghua Li, Chunguang Li, Yu Han, Shouhua Feng
      Abstract: A Cu MOF [Cu4(PMTD)2(H2O)3]·20H2O, 1, (Where PMTD is (1,4-phenylenebis(5-methyl-4H-1,2,4-triazole-3,4-diyl)bis(5-carboxylato-3,1-phenylene)bis(hydroperoxymethanide) with rare chiral Oh type of cage and dual functionalities of open metal sites and Lewis basic sites based on a designed U-shaped ligand was synthesized by hydrothermal method. It exhibits high-capacity of CO2, C2 and C3 hydrocarbon storage capacity under atmospheric pressure as well as high H2 (1.96% wt) adsorption capacity at 77K. Methane purification capacity was tested and verified step by step. Isosteric heats (Qst) study reveals that CH4 has the weakest van der Waals host- guest interactions among the seven gases at 298K. Ideal adsorbed solution theory (IAST) calculation reveals that compound 1 is more selective toward CO2, C2H6 and C3H8 over CH4 in further calculating its separation capacity, as exemplified for CO2/CH4 (50:50, 5:95), C2H6/CH4 (50:50, 5:95) or C3H8/CH4 (50:50, 5:95) binary gas mixtures. Breakthrough experiments show that 1 has a significantly higher adsorption capacity for CO2, C2H6 and C3H8 than CH4. The selective adsorption properties of 1 make it a promising candidate for methane purification.
      PubDate: 2018-01-18T03:25:24.654048-05:
      DOI: 10.1002/chem.201800010
       
  • Oxidation of Methylalumoxane Oligomers
    • Authors: Harmen Zijlstra; Scott Collins, Jason Scott McIndoe
      Abstract: The anions formed from methylalumoxane (MAO) and suitable donors (e.g. octamethyltrisiloxane) are amenable to mass spectrometric (MS) analysis. Their composition as deduced from this data allows direct insight into the chemical transformations of their neutral precursors. One such process is oxidation, which is well-known to be facile for MAO without any clear idea of what actually occurs at a molecular level. Addition of O2 to MAO results in immediate gelation, but MS analysis reveals no corresponding change to the composition of the principal oligomeric anions. A slow (hours) reaction does occur that involves net incorporation of Me2AlOMe into the oligomeric anions, and the identities of the OMe-containing anions were confirmed by 1H NMR, MS/MS analysis, and addition of an authentic sample of Me2AlOMe to MAO. The result tallies with the fact that addition of O2 to MAO produces Me2AlOMe from free Me3Al which eventually leads to formation of oxidized MAO oligomers and changes in ion abundance. Aging of the oxygenated MAO results in further growth of the oligomers similar to that of the non-oxidized species. Mass spectrometric analysis therefore reveals useful insights into the environmental history of a given MAO batch.
      PubDate: 2018-01-17T13:55:21.05559-05:0
      DOI: 10.1002/chem.201705458
       
  • Mixed Fluorotryptophan Substitutions at the Same Residue Expand the
           Versatility of ¹⁹F Protein NMR Spectroscopy
    • Authors: Calem Kenward; Kyungsoo Shin, Jan Rainey
      Abstract: The strategy of applying fluorine NMR to characterize ligand binding to a membrane protein prepared with mixtures of tryptophans substituted with F at different positions on the indole ring was tested. The ¹⁹F NMR behavior of 4-, 5-, 6-, and 7-fluorotryptophan were directly compared as a function of both micellar environment and fragment size for two overlapping apelin receptor (AR/APJ) segments - one with a single transmembrane (TM) helix and two tryptophan residues, the other with three TM helices and two additional tryptophan residues. Chemical shifts, peak patterns, and nuclear spin relaxation rates were observed to vary as a function of micellar conditions and F substitution position in the indole ring, with the exposure of a given residue to micelle or solvent being the primary differentiating factor. Titration of the 3-TM AR segment biosynthetically prepared with mixtures of 5- and 7-fluorotryptophan by two distinct peptide ligands - apelin-36 and apela-32 - demonstrated site-specific ¹⁹F peak intensity changes for one ligand but not the other. In contrast, both ligands perturbed ¹H-¹⁵N heteronuclear single quantum coherence experiment peak patterns to a similar degree. Characterization of fluorotryptophan mixtures for a given set of tryptophan residues, thus, significantly augments the potential to apply ¹⁹F NMR to track otherwise obscure modulation of protein conformation and dynamics without an explicit requirement for mutagenesis or chemical modification.
      PubDate: 2018-01-17T12:55:32.283146-05:
      DOI: 10.1002/chem.201705638
       
  • Twisted charge-transfer antennas for ultra-bright terbium(III) and
           dysprosium(III) bioprobes.
    • Authors: Anh Thy Bui; Amandine Roux, Alexei Grichine, Alain Duperray, Chantal Andraud, Olivier Maury
      Abstract: The design of original twisted charge transfer antennas where a non planar geometry is enforced thanks to one or two bulky ortho-Me substituents allows us to prepare the corresponding ultra-bright Tb(III) and Dy(III) bioprobes. The brightness of the Tb(III) derivative compares well with that of the benchmark Tb-Lumi4 complex. The first bio-imaging experiments with a Dy(III) luminescent bioprobe are also reported
      PubDate: 2018-01-17T11:56:51.386588-05:
      DOI: 10.1002/chem.201705933
       
  • Title Synthesis of α-L-fucopyranoside-presenting glycoclusters and
           investigation of their interaction with recombinant Photorhabdus
           asymbiotica lectin (PHL)
    • Authors: Jančaříková Gita; Mihály Herczeg, Eva Fujdiarová, Josef Houser, Katalin E. Kövér, Anikó Borbás, Michaela Wimmerová, Magdolna Csávás
      Abstract: Photorhabdus asymbiotica is a gram-negative bacterium that is not only as effective an insect pathogen as other members of the genus, but it also causes serious diseases in humans. The recently identified lectin PHL from P. asymbiotica verifiably modulates an immune response of humans and insects, which supports the idea that the lectin might play an important role in the host-pathogen interaction. Dimeric PHL contains up to seven L-fucose specific binding sites per monomer, and in order to target multiple binding sites of PHL, α-L-fucoside-containing di-, tri- and tetravalent glycoclusters were synthesized. Methyl gallate and pentaerythritol were chosen as multivalent scaffolds, and the fucoclusters were built from the above-mentioned cores by coupling with different oligoethylene bridges and propargyl α-L-fucosides using 1,3-dipolar azide-alkyne cycloaddition. The interaction between fucoside derivates and PHL was investigated by several biophysical and biological methods, ITC and SPR measurements, hemagglutination inhibition assay and an investigation of bacterial aggregation properties were carried out. Moreover, details of the interaction between PHL and propargyl α-L-fucoside as a monomer unit were revealed using X-ray crystallography. Besides this, the interaction with multivalent compounds was studied by NMR techniques. The newly synthesized multivalent fucoclusters proved to be up to several orders of magnitude better ligands than the natural ligand, L-fucose.
      PubDate: 2018-01-17T11:56:42.171752-05:
      DOI: 10.1002/chem.201705853
       
  • Chiral Phosphine–Phosphite Ligands in Asymmetric Gold Catalysis: Highly
           Enantioselective Synthesis of Furo[3,4-d]-Tetrahydropyridazine Derivatives
           through [3+3]-Cycloaddition
    • Authors: Qingwei Du; Jörg-Martin Neudörfl, Hans-Günther Schmalz
      Abstract: The AuI-catalyzed reaction of 2-(1-alkynyl)-2-alken-1-ones with azomethine imines regio- and diastereoselectively affords furo[3,4-d]tetrahydropyridazines in a tandem cyclization/intermolecular [3+3]-cycloaddition process under mild conditions. By employing a chiral gold catalyst (prepared in situ from a Taddol-derived phosphine-phosphite ligand, Me2SAuCl, and AgOTf) high yields and enantioselectivities (up to 94 % yield, up to 96 % ee) are obtained. The method provides an efficient modular route to substituted heterotricyclic furan derivatives and can be easily scaled up (using catalyst loads of only 0.15 mol %).The AuI-catalyzed reaction of 2-(1-alkynyl)-2-alken-1-ones with azomethine imines regio- and diastereoselectively affords furo[3,4-d]tetrahydropyridazines in a tandem cyclization/intermolecular [3+3]-cycloaddition process under mild conditions.
      PubDate: 2018-01-17T11:42:28.612071-05:
      DOI: 10.1002/chem.201800042
       
  • Isomeric Column-Forming Esters and Imides with Varying Curvatures of the
           Aromatic Plane
    • Authors: Marli Ferreira; Thamires S. Moreira, Rodrigo Cristiano, Hugo Gallardo, Ahmed Bentaleb, Pierre Dechambenoit, Elizabeth A. Hillard, Fabien Durola, Harald Bock
      Abstract: Dibenzo[a,j]coronene-tetracarboxylic alkyl esters and imides with either a centrosymmetric bis-peri substitution pattern or a polar bis-ortho substitution pattern form hexagonal columnar mesophases, which in the case of the imides persist at room temperature. The bis-peri isomers are obtained via a two-fold oxidative photocyclization; the bis-ortho isomers are accessed via a glyoxylic Perkin reaction of triphenylene and naphthalene building blocks. Steric congestion between the substituents and the adjacent benzo protrusion in the bis-ortho esters and imides leads to bending of the aromatic plane, which thus avoids twisting. These isomers surprisingly show a more pronounced liquid crystalline behaviour than their non-bent bis-peri homologs, accommodating non-planarity with columnar order by slipped stacking. Whereas both types of ester and the bis-peri imide show an optical behaviour typical for perylene chromophores, the strongly bent bis-ortho imide distinguishes itself notably from them by its absorption spectrum. The electron acceptor strength of the isomeric diimides is found to differ, the hexagonal (peri) diimide having a 0.20 eV lower LUMO energy than the pentagonal (ortho) isomer.Stacking up: Bent polar disks form slipped stacks and broad-range mesophases.
      PubDate: 2018-01-17T11:40:04.160137-05:
      DOI: 10.1002/chem.201705084
       
  • Preparation of a Si/SiO2–Ordered-Mesoporous-Carbon Nanocomposite as an
           Anode for High-Performance Lithium-Ion and Sodium-Ion Batteries
    • Authors: Lingxing Zeng; Renpin Liu, Lei Han, Fenqiang Luo, Xi Chen, Jianbiao Wang, Qingrong Qian, Qinghua Chen, Mingdeng Wei
      Abstract: In this work, an Si/SiO2–ordered-mesoporous carbon (Si/SiO2–OMC) nanocomposite was initially fabricated through a magnesiothermic reduction strategy by using a two-dimensional bicontinuous mesochannel of SiO2–OMC as a precursor, combined with an NaOH etching process, in which crystal Si/amorphous SiO2 nanoparticles were encapsulated into the OMC matrix. Not only can such unique porous crystal Si/amorphous SiO2 nanoparticles uniformly dispersed in the OMC matrix mitigate the volume change of active materials during the cycling process, but they can also improve electrical conductivity of Si/SiO2 and facilitate the Li+/Na+ diffusion. When applied as an anode for lithium-ion batteries (LIBs), the Si/SiO2–OMC composite displayed superior reversible capacity (958 mA h g−1 at 0.2 A g−1 after 100 cycles) and good cycling life (retaining a capacity of 459 mA h g−1 at 2 A g−1 after 1000 cycles). For sodium-ion batteries (SIBs), the composite maintained a high capacity of 423 mA h g−1 after 100 cycles at 0.05 A g−1 and an extremely stable reversible capacity of 190 mA h g−1 was retained even after 500 cycles at 1 A g−1. This performance is one of the best long-term cycling properties of Si-based SIB anode materials. The Si/SiO2–OMC composites exhibited great potential as an alternative material for both lithium- and sodium-ion battery anodes.On the hunt for anode materials: Si/SiO2–ordered-mesoporous-carbon (OMC) composite was initially fabricated through a magnesiothermic reduction strategy by using two-dimensional bicontinuous mesochannel of SiO2–OMC as a precursor, combined with a NaOH etching process. In addition the material exhibited great potential as an alternative material for both LIBs and SIBs anodes.
      PubDate: 2018-01-17T11:38:21.667794-05:
      DOI: 10.1002/chem.201704780
       
  • Dehydrogenation of N-Heterocycles by Superoxide Ion Generated through
           Single-Electron Transfer
    • Authors: Yuan-Qiong Huang; Hong-Jian Song, Yu-Xiu Liu, Qing-Min Wang
      Abstract: Nitrogen-containing heteroarene motifs are found in numerous pharmaceuticals, natural products, and synthetic materials. Although several elegant methods for synthesis of these compounds through dehydrogenation of the corresponding saturated heterocycles have been reported, some of the methods are hampered by long reaction times, harsh conditions, and the need for catalysts that are not readily available. This work reports a novel method for dehydrogenation of N-heterocycles. Specifically, O2.− generated in situ acts as the oxidant for N-heterocycle substrates that are susceptible to oxidation through a hydrogen atom transfer mechanism. This method provides a general, green route to N-heteroarenes.Superoxide ion: a novel method for dehydrogenation of N-heterocycles has been developed. Specifically, reductive electron transfer from Na/naphthalene to O2 generates O2.−, which oxidizes the N-heterocycles through a hydrogen atom transfer mechanism.
      PubDate: 2018-01-17T11:38:09.180404-05:
      DOI: 10.1002/chem.201705202
       
  • Highly Electrophilic, Catalytically Active and Redox-Responsive
           Cobaltoceniumyl and Ferrocenyl Triazolylidene Coinage Metal Complexes
    • Authors: Stefan Vanicek; Maren Podewitz, Jessica Stubbe, Dennis Schulze, Holger Kopacka, Klaus Wurst, Thomas Müller, Petra Lippmann, Simone Haslinger, Herwig Schottenberger, Klaus R. Liedl, Ingo Ott, Biprajit Sarkar, Benno Bildstein
      Abstract: A convenient access to a triad of triazoles with ferrocenyl and cobaltoceniumyl substituents are reported. N-Alkylation, deprotonation and metalation with CuI/AgI/AuI synthons affords the heteroleptic triazolylidene complexes. Due to the combination of neutral, electron-donating ferrocenyl substituents and cationic, strongly electron-withdrawing cobaltocenium substituents, the mesoionic carbene (MIC) ligands of these complexes are electronically interesting “push–pull”, “pull–push” and “pull–pull” metalloligands with further switchable redox states based on their fully reversible FeII/FeIII, (ferrocene/ferrocenium) and CoIII/CoII, (cobaltocenium/cobaltocene) redox couples. These are the first examples of metal complexes of (di)cationic NHC ligands based on cobaltoceniumyl substituents. DFT calculated Tolman electronic parameter (TEP) of the new MIC ligands, show these metalloligands to be extremely electron-poor NHCs with properties unmatched in other carbene chemistry. Utilization of these multimetallic electronically tunable compounds in catalytic oxazoline synthesis and in antitumor studies are presented. Remarkably, 1 mol % of the AuI complex with the dicationic MIC ligand displays full catalytic conversion, without the need for any other additives, in less than 2 hours at ambient temperatures. These results thus firmly establish these new classes of cobaltoceniumyl based (di)cationic MIC ligands as prominent players in several branches of chemistry.Cationic mesoionic carbene ligands with cobaltoceniumyl substituents are presented. These are the first examples of NHC ligands with such substituents. The cationic MIC ligands are extremely electron-poor displaying unprecedented high TEP values for NHC ligands. This fact was used in catalysis with their AuI complex that functions without the need of any additive.
      PubDate: 2018-01-17T11:37:59.031975-05:
      DOI: 10.1002/chem.201705051
       
  • BODIPY-Based Antiaromatic Macrocycles: Facile Synthesis by Knoevenagel
           Condensation and Unusual Aggregation-Enhanced Two-Photon Absorption
           Properties
    • Authors: Ming Hui Chua; Taeyeon Kim, Zheng Long Lim, Tullimilli Y. Gopalakrishna, Yong Ni, Jianwei Xu, Dongho Kim, Jishan Wu
      Abstract: Two stable boron dipyrromethene (BODIPY)-based antiaromatic macrocycles, Mc-Fur and Mc-Th, were synthesized through a one-pot Knoevenagel condensation reaction between a BODIPY precursor and furan-2,5-dicarboxaldehyde or thiophene-2,5-dicarboxaldehyde, respectively. 1H NMR spectroscopic characterization of the two macrocycles supported their highly antiaromatic character. The oxidation properties of the two macrocycles were studied through electron spin resonance spectroscopy and UV/Vis absorption spectrophotometry, which suggested the formation of a stable monoradical cation species on first oxidation followed by an aromatic dicationic species on subsequent oxidation. Both molecules have a nearly planar π-conjugated backbone and show a strong tendency to aggregate in solution due to efficient stacking of the antiaromatic macrocycles. Transient absorption and two-photon absorption (TPA) measurements in solution and aggregated states of the macrocycles revealed that aggregation resulted in large enhancement of TPA cross sections and increased excited-state lifetimes, in accordance with the decrease in the antiaromatic character in the aggregated state.Coming together: Antiaromatic macrocycles based on boron dipyrromethene (BODIPY) were synthesized through a one-pot Knoevenagel condensation reaction (see figure). These macrocycles exhibit a strong tendency to aggregate in solution and display aggregation-enhanced two-photon absorption properties.
      PubDate: 2018-01-17T11:37:46.569358-05:
      DOI: 10.1002/chem.201705271
       
  • In situ Formed Co(TCNQ)2 Metal-Organic Framework Array as a
           High-Efficiency Catalyst for Oxygen Evolution Reactions
    • Authors: Yicheng Wei; Xiang Ren, Hongmin Ma, Xu Sun, Yong Zhang, Xuan Kuang, Tao Yan, Dan Wu, Qin Wei
      Abstract: Energy conversion and storage systems such as water splitting devices and metal-air batteries need excellent and energy-efficiency oxygen evolution reaction (OER) catalysts. This work reports the in situ development of sawtooth-like Co(TCNQ)2 (TCNQ=tetracyanoquinodimethane) metal–organic framework array on Co foil (Co(TCNQ)2/Co) by means of a solution immersion method at room temperature. As an oxygen-evolving catalyst, the resulting Co(TCNQ)2/Co demonstrates superior OER activity with overpotential of 310 mV to drive a geometrical catalytic current density of 15 mA cm−2 in 1.0 M KOH. Notably, it also shows good long-term electrochemical durability with its activity being retained for at least 20 h and achieves a high turnover frequency of 0.66 mol O2 s−1 at overpotential of 380 mV.Blowing bubbles: A sawtooth-like Co(TCNQ)2 MOF array was fabricated by means of a solution immersion method at room temperature. This Co(TCNQ)2/Co shows superior oxygen-evolving activity, and only needs an overpotential as low as 310 mV to drive a geometrical catalytic current density of 15 mA cm−2 in 1.0 m KOH. Notably, it also demonstrates good long-term electrochemical durability with a high turnover frequency.
      PubDate: 2018-01-17T11:37:36.358155-05:
      DOI: 10.1002/chem.201705606
       
  • Multi-Functional Peptide–MicroRNA Nanocomplex for Targeted MicroRNA
           Delivery and Function Imaging
    • Authors: Xiao Xiao; Xingxing Wang, Yuqi Wang, Tianren Yu, Lei Huang, Lei Chen, Jinbo Li, Chenyu Zhang, Yan Zhang
      Abstract: Targeted delivery of microRNA (miRNA) mimics into specific cells/tissues and real-time monitoring on the biological function of delivered miRNA mimics at molecular level represent two major challenges in the development of miRNA-based therapeutics. Here we report a highly efficient method to address these two challenges simultaneously by using the self-assembled nanocomplex formed by miRNA mimics with a multi-functional peptide conjugate. Using the nanocomplex formed by tumor-suppressive miR-34a and the multi-functional peptide conjugate FA-R9-FPcas3, we demonstrated the highly efficient and target-selective delivery of miR-34a into HeLa cells and tumors. With the activatable fluorescence probe integrated in the peptide conjugate FA-R9-FPcas3, the intracellular function of miR-34a delivered by the nanocomplex to upregulate active Caspase-3 was imaged in real-time. The nanocomplex also showed significant therapeutic effects to induce apoptosis in HeLa cells and to suppress tumor growth upon tail vein injection into living mice bearing subcutaneous HeLa tumors.Mimics in a complex: A nanocomplex formed by a multi-functional peptide conjugate with microRNA mimic was prepared for targeted microRNA delivery, real-time imaging of microRNA function and therapeutics.
      PubDate: 2018-01-17T11:37:30.534096-05:
      DOI: 10.1002/chem.201705695
       
  • Laterally and Temporally Controlled Intracellular Staining by
           Light-Triggered Release of Encapsulated Fluorescent Markers
    • Authors: Karsten Kantner; Joanna Rejman, Karl V. L. Kraft, Mahmoud G. Soliman, Mikhail V. Zyuzin, Alberto Escudero, Pablo del Pino, Wolfgang J. Parak
      Abstract: Fluorescent molecular markers were encapsulated. The capsules were additionally modified with plasmonic nanoparticles. The encapsulated markers were endocytosed by cells. Upon light stimulation the plasmonic nanoparticles generated heat, which opened the encapsulation and transiently perforated the endosomal/lysosomal membrane surrounding the capsule, thus allowing for release of the marker into the cytosol. Fluorescence labeling of different intracellular compartments was demonstrated in this way. Most important, the cells do not need to be fixed and perforated, as the molecular markers are introduced into cells by endocytosis and subsequent light-induced release. Thus this technique allows for intracellular fluorescence labeling of living cells.Lighting up single cells: Encapsulated molecular markers can be intracellularly released upon an external light trigger and stain intracellular structures in living cells (see figure). Importantly, the cells do not need to be fixed and perforated, as the molecular markers are introduced into cells by endocytosis.
      PubDate: 2018-01-17T11:37:17.698884-05:
      DOI: 10.1002/chem.201706135
       
  • The Role of Terminal Functionality in the Membrane and Antibacterial
           Activity of Peptaibol-Mimetic Aib Foldamers
    • Authors: Catherine Adam; Anna D. Peters, M. Giovanna Lizio, George F. S. Whitehead, Vincent Diemer, James A. Cooper, Scott L. Cockroft, Jonathan Clayden, Simon J. Webb
      Abstract: Peptaibols are peptide antibiotics that typically feature an N-terminal acetyl cap, a C-terminal aminoalcohol, and a high proportion of α-aminoisobutyric acid (Aib) residues. To establish how each feature might affect the membrane-activity of peptaibols, biomimetic Aib foldamers with different lengths and terminal groups were synthesised. Vesicle assays showed that long foldamers (eleven Aib residues) with hydrophobic termini had the highest ionophoric activity. C-terminal acids or primary amides inhibited activity, while replacement of an N-terminal acetyl with an azide group made little difference. Crystallography showed that N3Aib11CH2OTIPS folded into a 310 helix 2.91 nm long, which is close to the bilayer hydrophobic width. Planar bilayer conductance assays showed discrete ion channels only for N-acetylated foldamers. However long foldamers with hydrophobic termini had the highest antibacterial activity, indicating that ionophoric activity in vesicles was a better indicator of antibacterial activity than the observation of discrete ion channels.Cap it off: To uncover how the structural features of peptaibols affect their membrane activity, α-aminoisobutyric acid (Aib) foldamers with different lengths and terminal groups were synthesised. The longest foldamers (eleven residues) with hydrophobic termini had the highest ionophoric activity in vesicles and best antibacterial activity, but only N-acetylated foldamers produced long-lived discrete ion channels.
      PubDate: 2018-01-17T11:37:09.938652-05:
      DOI: 10.1002/chem.201705299
       
  • Safe-by-Design Ligand-Coated ZnO Nanocrystals Engineered by an
           Organometallic Approach: Unique Physicochemical Properties and Low
           Toxicity toward Lung Cells
    • Authors: Małgorzata Wolska-Pietkiewicz; Katarzyna Tokarska, Agnieszka Grala, Anna Wojewódzka, Elżbieta Chwojnowska, Justyna Grzonka, Piotr J. Cywiński, Krzysztof Kruczała, Zbigniew Sojka, Michał Chudy, Janusz Lewiński
      Abstract: The unique physicochemical properties and biocompatibility of zinc oxide nanocrystals (ZnO NCs) are strongly dependent on the nanocrystal/ligand interface, which is largely determined by synthetic procedures. Stable ZnO NCs coated with a densely packed shell of 2-(2-methoxyethoxy)acetate ligands, which act as miniPEG prototypes, with average core size and hydrodynamic diameter of 4–5 and about 12 nm, respectively, were prepared by an organometallic self-supporting approach, fully characterized, and used as a model system for biological studies. The ZnO NCs from the one-pot, self-supporting organometallic procedure exhibit unique physicochemical properties such as relatively high quantum yield (up to 28 %), ultralong photoluminescence decay (up to 2.1 μs), and EPR silence under standard conditions. The cytotoxicity of the resulting ZnO NCs toward normal (MRC-5) and cancer (A549) human lung cell lines was tested by MTT assay, which demonstrated that these brightly luminescent, quantum-sized ZnO NCs have a low negative impact on mammalian cell lines. These results substantiate that the self-supporting organometallic approach is a highly promising method to obtain high-quality, nontoxic, ligand-coated ZnO NCs with prospective biomedical applications.Small but safe: A one-pot, self-supporting organometallic approach was used to synthesize stable ZnO nanocrystals (NCs) with a densely packed shell of 2-(2-methoxyethoxy)acetate ligands (see figure) as a model system for toxicological studies. These brightly luminescent ZnO NCs exhibit low toxicity, despite their small average core diameter of 4–5 nm, ultralong-lived luminescence, and EPR silence.
      PubDate: 2018-01-17T11:36:38.346157-05:
      DOI: 10.1002/chem.201704207
       
  • A Precisely Assembled Carbon Source to Synthesize Fluorescent Carbon
           Quantum Dots for Sensing Probes and Bioimaging Agents
    • Authors: Yiqiang Qiao; Dan Luo, Min Yu, Ting Zhang, Xuanping Cao, Yanheng Zhou, Yan Liu
      Abstract: A broad range of carbon sources have been used to fabricate varieties of carbon quantum dots (CQDs). However, the majority of these studies concern the influence of primary structures and chemical compositions of precursors on the CQDs; it is still unclear whether or not the superstructures of carbon sources have effects on the physiochemical properties of the synthetic CQDs. In this work, the concept of molecular assembly is first introduced into the design of a new carbon source. Compared with the tropocollagen molecules, the hierarchically assembled collagen scaffolds, as a new carbon source, immobilize functional groups of the precursors through hydrogen bonds, electrostatic attraction, and hydrophobic forces. Moreover, the accumulation of functional groups in collagen self-assembly further promotes the covalent bond formation in the obtained CQDs through a hydrothermal process. Both of these two chemical superiorities give rise to high quality CQDs with enhanced emission. The assembled collagen scaffold-based CQDs with heteroatom doping exhibit superior stability, and could be further applied as effective fluorescent probes for Fe3+ detection and cellular cytosol imaging. These findings open a wealth of possibilities to explore more nanocarbons from precursors with assembled superstructures.Put on the spot: Fluorescent carbon quantum dots (CQDs) have been synthesized from molecular tropocollagen and an assembled collagen scaffold. The concept of molecular assembly facilitates accumulation of functional groups; therefore, CQDs from an assembled collagen scaffold exhibit a higher quantum yield and stability than those from a collagen monomer (see figure).
      PubDate: 2018-01-17T11:35:54.200365-05:
      DOI: 10.1002/chem.201705310
       
  • Cyclobutanone Mimics of Intermediates in Metallo-β-Lactamase
           Catalysis
    • Authors: Martine I. Abboud; Magda Kosmopoulou, Anthony P. Krismanich, Jarrod W. Johnson, Philip Hinchliffe, Jürgen Brem, Timothy D. W. Claridge, James Spencer, Christopher J. Schofield, Gary I. Dmitrienko
      Abstract: The most important resistance mechanism to β-lactam antibiotics involves hydrolysis by two β-lactamase categories: the nucleophilic serine and the metallo-β-lactamases (SBLs and MBLs, respectively). Cyclobutanones are hydrolytically stable β-lactam analogues with potential to inhibit both SBLs and MBLs. We describe solution and crystallographic studies on the interaction of a cyclobutanone penem analogue with the clinically important MBL SPM-1. NMR experiments using 19F-labeled SPM-1 imply the cyclobutanone binds to SPM-1 with micromolar affinity. A crystal structure of the SPM-1:cyclobutanone complex reveals binding of the hydrated cyclobutanone through interactions with one of the zinc ions, stabilisation of the hydrate by hydrogen bonding to zinc-bound water, and hydrophobic contacts with aromatic residues. NMR analyses using a 13C-labeled cyclobutanone support assignment of the bound species as the hydrated ketone. The results inform on how MBLs bind substrates and stabilize tetrahedral intermediates. They support further investigations on the use of transition-state and/or intermediate analogues as inhibitors of all β-lactamase classes.Mimicking intermediates: Solution and crystallographic studies on the interaction of a cyclobutanone penem analogue with the clinically important MBL SPM-1 are described. The results inform on how metallo-β-lactamases bind substrates and stabilize tetrahedral intermediates.
      PubDate: 2018-01-17T11:35:45.846369-05:
      DOI: 10.1002/chem.201705886
       
  • A Self-Repairing Cathode Material for Lithium–Selenium Batteries: Se−C
           Chemically Bonded Selenium–Graphene Composite
    • Authors: Linna Sha; Peng Gao, Xiaochen Ren, Qianqian Chi, Yujin Chen, Piaoping Yang
      Abstract: Lithium–selenium batteries, employing selenium as a cathode material, exhibit some notable advantages, such as high discharge rates and good cycling performance, due to their high electrical conductivity, high output voltages, and high volumetric capacity density. However, an important problem, termed the “shuttle effect”, can lead to capacity decay in Li-Se cells (and in Li-S cells), which arises from aggregation and the loss of Se or S from the cathode into the electrolyte. In this work, in order to solve this problem, a new self-repairing system has been devised, in which some Se atoms are chemically bonded to the carbon atoms of graphene and act as reclaiming points for dissociated Se atoms through the establishment of -Se-Se-Se- chains. Se-decorated graphene (Se-GE) was first constructed through a facile high-energy ball-milling process. Its formation was confirmed by XRD, SEM, HRTEM, XPS, and Raman analyses. As we anticipated, in examining cell properties, the as-prepared Se-GE composite underwent an initial capacity decay in the first 20 cycles (from 1050 mAh g−1 to 750 mAh g−1, ca. 29 % loss), but the capacity then reverted to 970 mAh g−1 (ca. 92 % of the initial value). Other measurements were also consistent with the recapture of dissociated Se atoms.Let it Se: An Se−C-bonded interface has been constructed in a Se–graphene (GE) composite through facile high-energy ball-milling. Due to the presence of Se−C bonds, a new self-repairing Se-GE cathode material has been obtained (see graphic). It shows high reversible capacity, long cycle life, and high coulombic efficiency.
      PubDate: 2018-01-17T10:00:31.792855-05:
      DOI: 10.1002/chem.201704079
       
  • Enantioselective Synthesis of Aminodiols by Sequential Rh-Catalysed
           Oxyamination/Kinetic Resolution. Expanding the Substrate Scope of
           Amidine-Based Catalysis
    • Authors: Joan Guasch; Irene Giménez, Ignacio Funes-Ardoiz, Isabel Matheu, Feliu Maseras, Sergio Castillón, Yolanda Díaz, Miguel Bernús
      Abstract: Regio- and stereoselective oxyamination of dienes through a tandem rhodium catalysed aziridination-nucleophilic opening affords racemic oxazolidinone derivatives, which undergo a kinetic resolution acylation process using ABCs (amidine-based catalysts) achieving s values up to 117. This protocol was applied to the enantioselective synthesis of sphingosine.
      PubDate: 2018-01-17T08:56:47.022942-05:
      DOI: 10.1002/chem.201705670
       
  • Brønsted Base-Catalyzed Umpolung Intramolecular Cyclization of
           Alkynyl Imines
    • Authors: Azusa Kondoh; Masahiro Terada
      Abstract: A novel "umpolung" intramolecular cyclization of alkynyl imines, in which the electrophilic imine sp2-carbon formally serves as a nucleophilic site, was developed under Brønsted base catalysis. The reaction involves the unprecedented catalytic generation of α-aminoester enolates from α-iminoesters via the 1,2-addition of the anion of a secondary phosphite to an imine moiety followed by the [1,2]-rearrangement of a dialkoxyphosphoryl moiety from carbon to nitrogen, which is a formal umpolung process, and the intramolecular addition to an alkyne. This is a rare example of a [1,2]-rearrangement of a dialkoxyphosphoryl moiety from carbon to nitrogen to generate an α-amino carbanion and the first catalytic carbon-carbon bond forming reaction utilizing the resulting carbanion as a nucleophile.
      PubDate: 2018-01-17T08:56:20.821053-05:
      DOI: 10.1002/chem.201800219
       
  • Ligand- and Metal-Based Reactivity of a Neutral Ruthenium Diolefin
           Diazadiene Complex; The Innocent, the Guilty, and the Suspicious
    • Authors: Vivek Sinha; Bruno Pribanic, Bas de Bruin, Monica Trincado, Hansjörg Grützmacher
      Abstract: Coordination of the diazadiene diolefin ligand trop2dad to ruthenium leads to various complexes of composition [Ru(trop2dad)(L)]. DFT studies indicate that the closed-shell singlet (CSS), open-shell singlet (OSS) and triplet electronic structures of this species are close in energy, with the OSS state being the lowest in energy for all tested functionals. Singlet state CASSCF calculations reveal a significant multireference character for these complexes. The closed-shell singlet wavefunction dominates, but these complexes have a significant (~8-16%) open-shell singlet [d7 Ru(I)(L)(trop2dad●-] contribution mixed into the ground state. In agreement with their ambivalent electronic structure, these complexes reveal both metal and ligand centered reactivity. Most notably are the reactions with AdN3, diazomethane, and a phosphaalkyne leading to scission of the C-C bond of the diazadiene moiety of the trop2dad ligand, resulting in net (formal) nitrene, carbene or P-C insertion in the dad C-C bond, respectively. Supporting DFT studies reveal that several of the ligand-based reactions proceed via low barrier radical-type pathways, involving the dad●- ligand radical character of the OSS or triplet species.
      PubDate: 2018-01-17T08:25:30.819137-05:
      DOI: 10.1002/chem.201705957
       
  • Everything You Always Wanted to Know about Poly-l-lysine Dendrigrafts (But
           Were Afraid to Ask)
    • Authors: Jean-Patrick Francoia; Laurent Vial
      Abstract: Less than a decade ago, dendrigrafts of poly-l-lysine (DGLs) joined the family of polycationic dendritic macromolecules. Resulting from the iterative polycondensation of an N-carboxyanhydride in water, four generations of the dendrigraft can be obtained on a multigram scale and without chromatographic purification. DGLs share features with both dendrimers and hyperbranched polymers, but turned out to have unique biophysical and bioactive properties. The macromolecules—in their native form or functionalized—have been extensively characterized by various analytical and computational methods, and have already found numerous applications in the biomedical field, such as drug and gene delivery, biomaterials, tissue engineering, bioimaging, and biosensing. Despite a growing interest for DGLs, there is still plenty of room for further exciting developments that could result from a better exposure of these macromolecules, which is the ambition of this short review.Talkin′ ′bout my generation: Despite a growing interest for poly-l-lysine dendrigrafts, there is still plenty of room for further exiting developments that could result from a better exposure of these macromolecules, which is the ambition of this Minireview.
      PubDate: 2018-01-17T08:15:44.752416-05:
      DOI: 10.1002/chem.201704147
       
  • Direct Evidence for the Origin of Bis-Gold Intermediates: Probing Gold
           Catalysis with Mass Spectrometry
    • Authors: Mei Lu; Yijin Su, Pengyi Zhao, Xiaohan Ye, Yi Cai, Xiaodong Shi, Eric Masson, Fengyao Li, J. Larry Campbell, Hao Chen
      Abstract: Gold-catalyzed alkyne hydration was studied by using in situ reacting mass spectrometry (MS) technology. By monitoring the reaction process in solution under different conditions (regular and very diluted catalyst concentrations, different pH values) and examining the reaction occurrence in the early reaction stage (1–2 ms after mixing) with MS, we collected a series of experimental evidence to support that the bis-gold complex is a potential key reaction intermediate. Furthermore, both experimental and computational studies confirmed that the σ,π-bis-gold complexes are not active intermediates toward nucleophilic addition. Instead, formation of geminally diaurated complex C is crucial for this catalytic process.Going for gold: Gold-catalyzed alkyne hydration was studied by using in situ reacting mass spectrometry (MS) technology. By monitoring the reaction process in solution under different conditions and examining the reaction occurrence in the early reaction stage, experimental evidence to support that the bis-gold complex is a crucial reaction intermediate was collected (see scheme).
      PubDate: 2018-01-17T08:15:28.791279-05:
      DOI: 10.1002/chem.201703666
       
  • Brønsted Acid-Catalyzed Tandem Cyclizations of Tryptamine-Ynamides
           Yielding 1H-Pyrrolo[2,3-d]carbazole Derivatives
    • Authors: Yanshi Wang; Jingsheng Lin, Xiaoyu Wang, Guanghui Wang, Xinhang Zhang, Bo Yao, Yuandong Zhao, Pengfei Yu, Bin Lin, Yongxiang Liu, Maosheng Cheng
      Abstract: A highly efficient novel method for the construction of the core tetracyclic motif of numerous biologically active indole alkaloids was described. The cyclization precursors were easily prepared from tryptamine derivatives in five steps with excellent yields. The full potential of the developed method was demonstrated by the synthesis of Büchi ketone, a well-known intermediate in the synthesis of vindorosine. More information can be found in the Full Paper by Y. Liu, M. Cheng et al. (
      DOI : 10.1002/chem.201705189).
      PubDate: 2018-01-17T08:10:59.505172-05:
       
  • Tsuji–Trost Reaction of Non-Derivatized Allylic Alcohols
    • Authors: Sunisa Akkarasamiyo; Supaporn Sawadjoon, Andreas Orthaber, Joseph S. M. Samec
      Abstract: Pd[κ2-BiPhePhos][η3-C3H5][OTf] is reported as an efficient catalyst in the Tsuji–Trost reaction of non-derivatized allylic alcohols. Both inter- and intramolecular stereospecific allylic substitutions with various types of nucleophiles (C-, S-, N-, and O-centered) were successfully transformed. The desired products were obtained in high yield and high enantiospecificity and the only by-product was water. The catalyst complexes were also studied and a pivotal effect of a counter ion was found where the chloride promotes decoordination of one of the phosphites that gets oxidized and this leads to decomposition of the catalyst. Application of this robust catalytic system in the total syntheses of bioactive natural products (S)-cuspareine and (+)-lentiginosine is demonstrated. More information can be found in the Full Paper by A. Orthaber, J. S. M. Samec et al. (
      DOI : 10.1002/chem.201705164).
      PubDate: 2018-01-17T08:10:57.58598-05:0
       
  • Self-Assembly Process of a Pd2L4 Capsule: Steric Interactions between
           Neighboring Components Favor the Formation of Large Intermediates
    • Authors: Shumpei Kai; Masanori Nakagawa, Tatsuo Kojima, Xin Li, Masahiro Yamashina, Michito Yoshizawa, Shuichi Hiraoka
      Abstract: The effect of molecular interactions between the components on the self-assembly process of Pd2L4 structures was investigated by a 1H NMR-based quantitative approach (QASAP: quantitative analysis of self-assembly process). Although the self-assembly of the Pd2L4 cage without interactions between the bent ligands took place, mainly producing small intermediates, the self-assembly of the Pd2L4 capsule composed of bent ligands with anthracene panels tends to produce large intermediates containing more components than the capsule. This is ascribed to steric interactions between the panels.Bending New Corners: The introduction of anthracene panels in a bent ditopic ligand alters the self-assembly pathway of the Pd2L4 complex, transiently producing large intermediates containing more components than the capsule. This effect can be ascribed to steric interactions between the neighboring panels.
      PubDate: 2018-01-17T08:10:55.622051-05:
      DOI: 10.1002/chem.201705253
       
  • Characterization at the Level of Individual Crystals: Single-Crystal MFI
           Type Zeolite Grains
    • Authors: Tim Gruene; Teng Li, Eric van Genderen, Ana B. Pinar, Jeroen A. van Bokhoven
      Abstract: Electron-diffraction data on the zeolites Silicalite-1 and ZSM-5 (both MFI framework type) were collected from individual grains of about 150×100×50 nm3. Crystals were synthesized with tetrapropylammonium as structure-directing agent. The resolution extended to about 0.8 Å for Silicalite-1 and about 0.9–1.0 Å for ZSM-5 crystals. Analysis of several data sets showed that at the nanometre-scale, these zeolite crystals are single crystals and not intergrown.Electron-diffraction data on the zeolites Silicalite-1 and ZSM-5 (both MFI framework type) were collected from individual grains of about 150×100×50 nm3. Crystals were synthesized with tetrapropylammonium as structure-directing agent. Analysis of several data sets showed that at the nanometer-scale, these zeolite crystals are single crystals and not intergrown (see scheme).
      PubDate: 2018-01-17T08:10:38.560017-05:
      DOI: 10.1002/chem.201704213
       
  • Evidence for a Cooperative Mechanism Involving Two Palladium(0) Centers in
           the Oxidative Addition of Iodoarenes
    • Authors: Luca Alessandro Perego; Pierre-Adrien Payard, Baptiste Haddou, Ilaria Ciofini, Laurence Grimaud
      Abstract: Oxidative addition of iodoarenes (ArI) to Pd0 ligated by 1-methyl-1H-imidazole (mim) in polar solvents leads to cationic arylpalladium(II) complexes [ArPd(mim)3]+. Kinetic analyses evidence that this reaction is second order with respect to the concentration of Pd0, and a mechanism involving the cooperative intervention of two Pd0 centers has been postulated to explain this finding. This unusual behavior is also observed with other nitrogen-containing ligands and it is general for iodobenzenes substituted with electron-donating or weakly electron-withdrawing groups. In contrast, bromoarenes and electron-poor iodoarenes display first-order kinetics with respect to Pd0. Theoretical calculations performed at the density functional theory (DFT) level suggest the existence of mim-ligated ArI-Pd0 complexes, in which the iodoarene is bound to the metal in a halogen-bond-like fashion. Coordination weakens the C−I bond and facilitates the oxidative insertion of another Pd0 center across this C−I bond. This conceptually novel mechanism, involving the cooperative participation of two distinct metal centers, allows a full explanation of the experimentally observed kinetics.A palladium duo: Oxidative addition of iodoarenes to Pd0 complexes with nitrogen ligands obeys second-order kinetics with respect to Pd0, and a mechanism involving the cooperative intervention of two metal centers is proposed to explain this finding (see graphic). Theoretical calculations suggest the existence of ArI−Pd0 complexes, in which the iodoarene is bound to the metal in a halogen-bond-like fashion, thus weakening the C−I bond and facilitating the insertion of another Pd0 center.
      PubDate: 2018-01-17T08:10:30.219386-05:
      DOI: 10.1002/chem.201704899
       
  • Fluorescence redox blinking adaptable to structural analysis of nucleic
           acids
    • Authors: Takafumi Miyata; Naohiko Shimada, Atsushi Maruyama, Kiyohiko Kawai
      Abstract: The phenomenon of "blinking" is unique to single-molecule fluorescence measurements. By designing a fluorophore with an appropriate dark state lifetime (τoff), we have devised a kinetic analysis based on the control of fluorescence blinking (KACB) to investigate the dynamics of biomolecules. By controlling the redox reaction based blinking (rKACB), we have previously investigated conformational dynamics of RNA at the single-molecule level. However, there have been little knowledge about suitable fluorescent molecules for rKACB, and the application of rKACB has been limited to the analysis of hairpins and duplex structures of nucleic acids. In this paper, we evaluated various fluorescent molecules, including ATTO 655, ATTO 647N, TAMRA, R6G, and Alexa 488, for rKACB. rKACB was adapted to the discrimination of DNA/DNA and DNA/RNA nucleic acid duplexes and investigation of antigen-antibody interactions. Further, by changing the size of the oxidant, we were able to determine the solvent accessibility of the target domain of the biomolecules analysed.
      PubDate: 2018-01-17T07:55:21.87609-05:0
      DOI: 10.1002/chem.201705668
       
  • 2,2'-Bipyridine Equipped with a Disulfide/Dithiol Switch for Coupled Two
           Electron and Proton Transfer
    • Authors: Mauricio Cattaneo; Christine Schiewer, Anne Schober, Sebastian Dechert, Inke Siewert, Franc Meyer
      Abstract: [1,2]dithiino[4,3-b:5,6-b']dipyridine (1) and its protonated open form 3,3'-dithiol-2,2'-bipyridine (2) were synthesised and their interconversion investigated. The X-ray structure of 2 revealed an anti orientation of the two pyridine units and a zwitterionic form. In depth electrochemical studies in combination with DFT calculations lead to a comprehensive picture of the redox chemistry of 1 in the absence and presence of protons. Initial one electron reduction at E1 = −1.97 V results in the formation of the radical anion 1red with much elongated S-S bond, which readily undergoes further reduction at E2 = −2.15 V. Water triggers a potential inversion (E ≥ −1.9 V for the second reduction) as the radical anion 1red is protonated at its basic N atom. DFT studies revealed that S−S bond breaking and twisting of the pyridine units generally occurs after the second reduction step while the potential inversion induced by protonation is a result of charge compensation. The CV data were simulated to derive rate constants for the individual chemical and electrochemical reactions for both scenarios in the absence and presence of protons.
      PubDate: 2018-01-17T07:26:21.572604-05:
      DOI: 10.1002/chem.201705022
       
  • The Pentagonal-Pyramidal Hexamethylbenzene Dication: The Many Shades of
           Coordination Chemistry at Carbon
    • Authors: Johannes E. M. N. Klein; Remco W. A. Havenith, Gerald Knizia
      Abstract: A recent report of the crystal structure of the pentagonal-pyramidal hexamethylbenzene dication C6(CH3)62+ by Malischewski and Seppelt [Angew. Chem. Int. Ed. 2017, 56, 368.] confirmed the structural proposal made in the first report of this compound in 1973 by Hogeveen and Kwant [Tetrahedron Lett. 1973, 14, 1665]. The widespread attention that this compound quickly gained led us to reinvestigate its electronic structure. Based on intrinsic bond orbital analysis, effective oxidation state analysis, ring current analysis and comparison to well established coordination complexes, we demonstrate that the central carbon atom behaves like a transition metal. The central (apical) carbon atom, although best described as a highly Lewis-acidic carbon atom coordinated with an anionic cyclopentadienyl ligand, is also capable to act as an electron pair donor to a formal CH3+ group. The different roles of coordination chemistry are discussed.
      PubDate: 2018-01-17T06:55:23.026196-05:
      DOI: 10.1002/chem.201705812
       
  • One-Pot Synthesis of Functionalized Fused Furans via a BODIPY Catalyzed
           Domino Photooxygenation
    • Authors: Audrey Mauger; Jonathan Farjon, Pierrick Nun, Vincent Coeffard
      Abstract: Six-membered ring fused furans containing a tetrasubstituted tertiary carbon were prepared via an unprecedented one-pot BODIPY-catalyzed domino photooxygenation/reduction process. A series of functionalized furans was synthesized from readily available 2-alkenylphenols and mechanistic studies were performed to account for the domino photosensitized oxygenation.
      PubDate: 2018-01-17T06:25:26.807938-05:
      DOI: 10.1002/chem.201706087
       
  • NOE-Derived Methyl Distances from a 360 kDa Proteasome Complex
    • Authors: Celestine N. Chi; Dean Strotz, Roland Riek, Beat Vögeli
      Abstract: Nuclear magnetic resonance spectroscopy is the prime tool to probe structure and dynamics of biomolecules at atomic resolution. A serious challenge for that method is the size limit imposed on molecules to be studied. Standard studies are typically restricted to ca. 30–40 kDa. More recent developments lead to spin relaxation measurements in methyl groups in single proteins or protein complexes as large as a mega-Dalton, which directly allow the extraction of angular information or experiments with paramagnetic samples. However, these probes are all of indirect nature in contrast to the most intuitive and easy-to-interpret structural/dynamics restraint, the internuclear distance, which can be measured by nuclear Overhauser enhancement (NOE). Herein, we demonstrate time-averaged distance measurements on the 360 kDa half proteasome from Thermoplasma acidophilium. The approach is based on exact quantification of the NOE (eNOE). Our findings open up an avenue for such measurements on very large molecules. These restraints will help in a detailed determination of conformational changes upon perturbation such as ligand binding.Dalton protractor: Time-averaged distance measurements on the 360 kDa half proteasome from Thermoplasma acidophilium are demonstrated. The approach is based on exact quantification of the nuclear Overhauser enhancement (eNOE). The findings open up an avenue for such measurements on very large molecules. These restraints will help in a detailed determination of conformational changes upon perturbation such as ligand binding.
      PubDate: 2018-01-17T05:57:06.983042-05:
      DOI: 10.1002/chem.201705551
       
  • Green Synthesis of a New Al-MOF Based on the Aliphatic Linker Mesaconic
           Acid: Structure, Properties and In Situ Crystallisation Studies of
           Al-MIL-68-Mes
    • Authors: Helge Reinsch; Thomas Homburg, Niclas Heidenreich, Dominik Fröhlich, Stefan Hennninger, Michael Wark, Norbert Stock
      Abstract: A new aluminium metal-organic framework (MOF), based on the short aliphatic linker molecule mesaconic acid (H2Mes; methylfumaric acid) is reported. Al-MIL-68-Mes with composition [Al(OH)(O2C-C3H4-CO2)]⋅n H2O is obtained after short reaction times of 45 minutes under mild, aqueous synthesis conditions (95 °C). It exhibits a kagome-like framework structure with large hexagonal, and small trigonal channels (diameters of ≈6 and ≈2 Å, respectively) and a specific surface area of SBET ≈1040 m2 g−1 (VMIC=0.42 cm3 g−1). A sigmoidal vapour sorption isotherm for water, and uptakes of water and methanol above 30 wt. % were observed. Al-MIL-68-Mes is stable against water ad-/desorption and its thermal stability is 350 °C in air. The proton conductivity for the hydrated MOF showed values up to 1.1×10−5 S cm at 130 °C and 100 % relative humidity, which exceeds the values observed for the non-hydrated compound by up to four orders of magnitude. Using synchrotron radiation the crystallisation of the MOF by in situ PXRD was also studied at temperatures from 80 to 100 °C. Kinetic evaluation revealed that the induction periods and crystallization times vary depending on the synthesis batch, but the rate limiting steps are consistently observed.Green Aluminium Mesaconate: The new MOF Al-MIL-68-Mes based on mesaconic acid was obtained under green synthesis conditions and exhibits the rare kagome structure. It shows high porosity and stability under humid conditions. Its formation was followed by in situ PXRD.
      PubDate: 2018-01-17T05:45:42.957327-05:
      DOI: 10.1002/chem.201704771
       
  • An Efficient Protocol to Synthesize N-Acyl-enamides and -Imines by
           Pd-Catalyzed Carbonylations
    • Authors: Lin Wang; Helfried Neumann, Anke Spannenberg, Matthias Beller
      Abstract: For the first time, the bidentate phosphinite ligand 1,2-bis(di-tert-butylphosphinoxy)ethane (tBu2POCH2CH2OPtBu2) was synthesized. In the presence of this ligand, various N-acyl enamides were obtained in good yields and chemoselectivity by Pd-catalyzed carbonylation reaction of imines containing α-H. Meanwhile, imines without α-H could be transformed to N-acyl imines, which form highly hindered amides by straightforward addition of Grignard reagents.The new phosphinite ligand 1,2-bis(di-tert-butylphosphinoxy)ethane (tBu2POCH2CH2OPtBu2) allows Pd-catalyzed carbonylation reaction of N−H imines to give selectively N-acyl-enamides and -imines (see scheme).
      PubDate: 2018-01-17T05:35:41.57609-05:0
      DOI: 10.1002/chem.201704704
       
  • Plasmid-Templated Control of DNA-Cyclodextrin Nanoparticle Morphology
           Through Molecular Vector Design for Effective Gene Delivery
    • Authors: Laura Gallego-Yerga; Juan M Benito, Laura Blanco-Fernández, María Martínez-Negro, Itziar Vélaz, Emilio Aicart, Elena Junquera, Carmen Ortiz Mellet, Conchita Tros de Ilarduya, Jose M. Garcia Fernandez
      Abstract: Engineering self-assembled superstructures through complexation of plasmid DNA (pDNA) and single-isomer nanometric size macromolecules (molecular nanoparticles) is a promising strategy for gene delivery. Notably, the functionality and overall architecture of the vector can be precisely moulded at the atomic level by chemical tailoring, enabling unprecedented opportunities for structure/self-assembling/pDNA delivery relationship studies. Beyond this notion, by judiciously preorganizing the functional elements in cyclodextrin (CD)-based molecular nanoparticles through covalent dimerization, here we demonstrate that the morphology of the resulting nanocomplexes (CDplexes) can be tuned, from spherical to ellipsoidal, rod-type or worm-like nanoparticles, which makes it possible to gain understanding of their shape-dependent transfection properties. The experimental findings are in agreement with a shift from chelate to cross-linking interactions on going from primary face- to secondary face-linked CD dimers, the pDNA partner acting as an active payload and as a template. Most interestingly, transfection efficiency in different cells was shown to be differently impacted by modifications on CDplex morphology, which has led to the identification of an optimal prototype for tissue-selective DNA delivery to the spleen in vivo.
      PubDate: 2018-01-17T05:25:34.559778-05:
      DOI: 10.1002/chem.201705723
       
  • Circularly Polarized Luminescence Appeared from Complete Inorganic
           Materials Encapsulating Guest Lanthanide Oxides in Host Chiral Silica
    • Authors: Ren-Hua Jin
      Abstract: Recently, circularly polarized luminescence (CPL)-active systems have become a very hot and interesting subject in chirality- and optics-related areas. The CPL-active systems are usually available by two approaches: combining covalently a luminescent centre to chiral motif or associating the guest of luminescent probe to a chiral host. However, all the chiral components in CPL materials were organics although the parts of luminescent were alternative as organics or inorganics. Herein, we proposed the first totally inorganic CPL-active system by "luminescent guest - chiral host" strategy. Typically, luminescent sub-10 nm lanthanide oxides (Eu2O3 or Tb2O3) nanoparticles ("guest") were encapsulated on chiral non-helical SiO2 nanofibres ("host") via the calcination (at 900 oC) of chiral SiO2 hybrids nanofibres of trapping Eu3+ (or Tb3+). These lanthanide oxides showed circular dichroism (CD) optical activity in the ultraviolet wavelength and CPL signals around at 615 nm for Eu3+ or 545 nm for Tb3+. This work would be very instructive to design inorganics-based CPL-active systems by incorporation of various luminescent guests in chiral inorganic hosts.
      PubDate: 2018-01-17T02:57:51.219866-05:
      DOI: 10.1002/chem.201705862
       
  • Synthesis, Crystal Analysis and Optoelectronic Properties of
           Diazole-functionalized Acenes and Azaacenes
    • Authors: Jinchong Xiao; Huahang Pan, Tingting Song, Xiaomeng Yin, Pengcheng Jin
      Abstract: Doping heteroatoms into the skeletons of parent acenes can provide more chances to construct novel thermally and photo-stable organic π-conjugated semiconductors. Herein, a family of diazole-decorated acenes (APyS and APySe) and azaacenes (PyP, PyTh, PyPy, PyPh and PyAP) have been successfully synthesized through the classical reactions. Single crystal X-ray analyses showed that these as-formed diazole-modified derivatives adopted twisted topology configuration, whereas the azaacenes display reclining-chair architectures, besides twisted structure. All these compounds displayed yellow or red light in solution. Moreover, their electrochemical behaviors were also examined. We also found that the azaacenes exhibited positive spectroscopic response to acid.
      PubDate: 2018-01-17T02:57:29.465567-05:
      DOI: 10.1002/chem.201705657
       
  • Chemical and Enzymatic Strategies for Bacterial and Mammalian Cell Surface
           Engineering
    • Authors: Xiaobao Bi; Juan Yin, Ashley Chen Guanbang, Chuan-Fa Liu
      Abstract: Cell surface serves important functions such as the regulation of cell-cell and cell-environment interactions. The understanding and manipulation of the cell surface is important for a wide range of fundamental studies of cellular behavior and for biotechnological and medical applications. With the rapid advance of biology, chemistry and materials science, many strategies have been developed for the functionalization of bacterial and mammalian cell surfaces. Here, we review the recent development of chemical and enzymatic approaches to cell surface engineering with particular emphasis on discussing the advantages and limitations of each of these strategies.
      PubDate: 2018-01-17T02:27:06.528461-05:
      DOI: 10.1002/chem.201705049
       
  • Graphitic Carbon Nitride as a Distinct Solid Stabilizer for Emulsion
           Polymerization
    • Authors: Qian Cao; Qianling Cui, Yu Yang, Jingsan Xu, Chenhui Han, Lidong Li
      Abstract: g-C3N4 has been found to be highly functional in many fields, such as photocatalysis, electrocatalysis, and chemical analysis. Pickering emulsion polymerization is a fascinating strategy to fabricate a range of nanomaterials, in which the emulsion is stabilized by solid particles, rather than molecular surfactants. Herein, we demonstrate that g-C3N4 can act as a remarkable stabilizer for Pickering emulsion polymerization. Contrary to normal Pickering systems, monodisperse polystyrene microspheres with tunable size, surface charge, and morphology were achieved using this approach. Importantly, the g-C3N4 hybridized latex is highly processable and has exhibited multiple functions: manufacture of photonic crystals via self-organization, stabilizing Pickering emulsion owing to proper wettability, and acting as bioimaging agents with enriched fluorescent colors. Considering the easy synthesis and low cost of g-C3N4, our approach has a high potential for scale-up synthesis and practical translation.Small wonder: Graphitic carbon nitride (g-C3N4) was used as a Pickering-type stabilizer for emulsion polymerization. Monodisperse polystyrene microspheres with tunable size, surface charge, and morphologies are produced, demonstrating remarkable processability and versatility (see scheme).
      PubDate: 2018-01-17T02:06:16.685069-05:
      DOI: 10.1002/chem.201705885
       
  • Interlocked Photo-degradable Macrocycles Allow One-Off Photo-triggerable
           Gelation of Organo- and Hydrogelators
    • Authors: Shun-Te Tung; Hung-Te Cheng, Alex Inthasot, Fang-Che Hsueh, Ting-Jia Gu, Pei-Cong Yan, Chien-Chen Lai, Sheng-Hsien Chiu
      Abstract: [2]Rotaxanes displaying one-off photo-triggerable gelation properties have been synthesized through the “clipping” of photo-degradable macrocycles around the amide or urea functionalities of organo- and hydrogelators. Irradiation with UV-light cleaved the photo-labile macrocyclic components from the [2]rotaxanes, resulting in the free gelators being released into solution and, thereafter, forming gels. When the rate of gelation was sufficiently rapid, selective gelation of specific regions of the solution—and, indeed, photo-patterning of the solution—was possible.“Clipping” a photo-degradable macrocycle around the amide or urea functionalities of organo- and hydrogelators has provided [2]rotaxanes displaying one-off photo-triggerable gelation properties-in one case allowing photo-patterning of a solution with specific “letters” of gel.
      PubDate: 2018-01-17T02:06:08.452079-05:
      DOI: 10.1002/chem.201705753
       
  • Metalation Control of Open-Shell Character in meso-meso Linked Porphyrin
           meso-Oxy Radical Dimers
    • Authors: Yuta Jun-i; Norihito Fukui, Ko Furukawa, Atsuhiro Osuka
      Abstract: Control of open-shell character of meso-meso linked porphyrin meso-oxy radical dimers has been demonstrated by core metalation. Namely, NiII-porphyrin dimer 6Ni exhibits a clear 1H NMR spectrum and a distorted but rather coplanar quinonoidal structure consisting of two ruffled porphyrin rings, in accordance with the previous report. Freebase dimer 6H2 shows a similar quinonoidal structure in the solid state but displays slightly broader and temperature-dependent 1H NMR spectra, indicating a partial diradical character in solution that increases at high temperature. In sharp contrast, bis-imidazole-coordinated ZnII-porphyrin dimer 6ZnIm2 exhibits a perpendicular structure consisting of two planar ZnII-porphyrins and has been characterized as a distinct open-shell diradical on the basis of its non-observable 1H NMR signals, a clear ESR signal, and a characteristic absorption spectrum reaching about 1700 nm. Despite the distinct diradical character, 6ZnIm2 is an extremely stable molecule.Control of open-shell character in meso-meso linked porphyrin meso-oxy radical dimers has been achieved by core metalation. Whereas NiII-porphyrin dimer exhibits a distorted but coplanar quinonoidal structure with the closed-shell ground state, bis-imidazole-coordinated ZnII-porphyrin dimer displays a perpendicular structure consisting of two planar porphyrin segments with the open-shell singlet diradical ground state.
      PubDate: 2018-01-17T02:05:35.502368-05:
      DOI: 10.1002/chem.201705769
       
  • Redox-Active Ligand-Assisted Two-Electron Oxidative Addition to
           Gallium(II)
    • Authors: Igor L. Fedushkin; Vladimir A. Dodonov, Alexandra A. Skatova, Vladimir G. Sokolov, Alexander V. Piskunov, Georgii K. Fukin
      Abstract: The reaction of digallane (dpp-bian)Ga−Ga(dpp-bian) (2) (dpp-bian=1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with allyl chloride (AllCl) proceeded by a two-electron oxidative addition to afford paramagnetic complexes (dpp-bian)Ga(η1-All)Cl (3) and (dpp-bian)(Cl)Ga−Ga(Cl)(dpp-bian) (4). Treatment of complex 4 with pyridine induced an intramolecular redox process, which resulted in the diamagnetic complex (dpp-bian)Ga(Py)Cl (5). In reaction with allyl bromide, complex 2 gave metal- and ligand-centered addition products (dpp-bian)Ga(η1-All)Br (6) and (dpp-bian-All)(Br)Ga−Ga(Br)(dpp-bian-All) (7). The reaction of digallane 2 with Ph3SnNCO afforded (dpp-bian)Ga(SnPh3)2 (8) and (dpp-bian)(NCO)Ga−Ga(NCO)(dpp-bian) (9). Treatment of GaCl3 with (dpp-bian)Na in diethyl ether resulted in the formation of (dpp-bian)GaCl2 (10). Diorganylgallium derivatives (dpp-bian)GaR2 (R=Ph, 11; tBu, 14; Me, 15; Bn, 16) and (dpp-bian)Ga(η1-All)R (R=nBu, 12; Cp, 13) were synthesized from complexes 3, 10, Bn2GaCl, or tBu2GaCl by salt metathesis. The salt elimination reaction between (dpp-bian)GaI2 (17) and tBuLi was accompanied by reduction of both the metal and the dpp-bian ligand, which resulted in digallane 2 as the final product. Similarly, the reaction of complex 10 with MentMgCl (Ment=menthyl) proceeded with reduction of the dpp-bian ligand to give the diamagnetic complex [(dpp-bian)GaCl2][Mg2Cl3(THF)6] (18). Compounds 11, 12, 13, 15, and 16 were thermally robust, whereas compound 14 decomposed when heated at reflux in toluene to give complex (dpp-bian-tBu)GatBu2 (19). Both complexes 7 and 19 contain R-substituted dpp-bian ligand: in the former compound the allyl group was attached to the imino-carbon atom, whereas in complex 19, the tBu group was situated on the naphthalene ring. Crystal structures of complexes 3, 8, 9, 10, 13, 14, 18, and 19 were determined by single-crystal X-ray analysis. The presence of dpp-bian radical anions in 3, 6, 8, and 10–16 was determined by ESR spectroscopy.Gallium complexes: Redox-active catalysts can substantially expand the reactivity of metal complexes, which can enable possible applications into catalysis. They are commonly incorporated into transition-metal complexes; however, this paper reports the oxidative addition of organic substrates to a gallium complex of redox-active 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (see scheme).
      PubDate: 2018-01-17T01:56:24.265809-05:
      DOI: 10.1002/chem.201704128
       
  • Structural factors affecting binding of platinum anticancer agents with
           phospholipids. Influence of charge and phosphate clamp formation
    • Authors: Anil Kumar Gorle; Junyong Zhang, Qin Liu, Susan J. Berners-Price, Nicholas P Farrell
      Abstract: We report a detailed NMR and DFT study of the interaction of polynuclear platinum anticancer agents (PPCs) with negatively charged phospholipids as a mechanism for their cellular uptake. The reactions of fully 15N-labelled [{trans-PtCl(NH3)2}2(-trans-Pt(NH3)2{NH2(CH2)6NH2}2)]4+ (15N-1, 1,0,1/t,t,t) and the dinuclear [{trans-PtCl(NH3)2}2{-H2N(CH2)6NH2}]2+ (15N-2, 1,1/t,t) with the sodium salt of 1,2-dihexanoyl-sn-glycero-3-phosphate (DHPA) were studied at 298 K, pH ~5.4, by [1H,15N] HSQC 2D NMR spectroscopy. Both 15N-1 and -2 form an initial mono-adduct in which the DHPA is coordinated via the phosphate O atom. For the dinuclear 15N-2, coordination of a second DHPA, in two different orientations, leads to two conformers of the bifunctional adduct. For 15N-1, coordination of the second DHPA allows the central {PtN4} coordination unit to bind electrostatically to two additional DHPA molecules via phosphate clamp interactions, in an extended network. For both 1,0,1/t,t,t (1) and 1,1/t,t (2), equilibrium conditions are obtained more slowly (> 35 h) than in the presence of phosphate (12 h) and in each case the rate constant for the first step of DHPA binding (kL) is about 8 times higher than that for phosphate, whereas the rate constants for the reverse reactions are quite similar. Reaction of 15N-1 with the sodium salt of 1,2-dihexanoyl-sn-glycero-3-[phosphatidyl-L-serine] (DHPS) showed only minor adduct formation via coordination to the N-donor atom of the phosphoserine group
      PubDate: 2018-01-17T00:20:34.729555-05:
      DOI: 10.1002/chem.201705822
       
  • Controlling selectivity in aliphatic C-H oxidation via supramolecular
           recognition
    • Authors: Diego Vidal; Giorgio Olivo, Miquel Costas
      Abstract: Aliphatic C-H oxidation is the most attractive approach to functionalize hydrocarbon skeletons. The main challenge of this reaction is the control of regioselectivity since organic molecules contain multiple C-H bonds. This control is perfectly achieved in natural enzymes by means of a web of interactions that orient the substrate in a specific geometry and override intrinsic reactivity patterns. Replication of this control by combination of molecular catalysts and supramolecular recognition is highly desirable in this regard. This strategy would unlock hydroxylation of C-H bonds that are not accessible with conventional methodologies, in which the selectivity dictated by the geometry of the substrate-receptor adduct. Herein, we review the reports of recognition-driven C-H oxidations and highlight the key design principles that inspired these works.
      PubDate: 2018-01-16T14:50:24.669503-05:
      DOI: 10.1002/chem.201704852
       
  • Fixing the conformation of calix[4arenes:when are three carbons not
           enough'
    • Authors: Susan Matthews; Samy Cecioni, John E O’Brien, Colin J MacDonald, David L Hughes, Garth A Jones, Stephen H. Ashworth, Sébastien Vidal
      Abstract: Calix[4]arenes are unique macrocycles that through judicious functionalisation at the lower-rim can be either fixed in one of four conformations or remain conformationally flexible. Introduction of propynyl or propenyl groups unexpectedly provides a new possibility; a unidirectional conformational switch, with the 1,3-alternate and 1,2-alternate conformers switching to the partial cone conformation, whilst the cone conformation is unchanged, under standard experimental conditions. Using 1H NMR kinetic studies, rates of switching have been shown to be dependent on the starting conformation, upper-rim substituent, where reduction in bulk enables faster switching, solvent and temperature with 1,2-alternate conformations switching fastest. Ab initio calculations (DFT) confirmed the relative stabilities of the conformations and point towards the partial cone conformer being the most stable of the four. The potential impact on synthesis through the 'click' reaction has been investigated and found not to be significant.
      PubDate: 2018-01-16T12:20:39.926742-05:
      DOI: 10.1002/chem.201705955
       
  • Organotin dyes bearing anionic boron clusters as cell-staining fluorescent
           probes.
    • Authors: Rosario Nuñez; Blanca M. Muñoz Flores, Justo Cabrera-González, Clara Viñas, Arturo Chávez-Reyes, H. V. Rasika Dias, Victor Manuel Jiménez Pérez
      Abstract: Herein, the design of novel fluorescent organotin compounds derived from 4-hydroxy-N'-((2-hydroxynaphthalen-1-yl)methylene)benzohydrazidato and their cytoplasm and nucleoli staining in vitro (B16F10 cells) are described. Tin compounds were prepared to bear an aliphatic carbon chain (-C12H25) and an electrodonor group (-OH), being also the latest derivatised to contain boron cluster anions, [B12H12]2- and [3,3′-Co(1,2-C2B9H11)2]- (COSAN). All the conjugates have been fully characterised and their luminescence properties assessed. They show in general good quantum yields in solution (24% - 49%), being lower for COSAN derivatives. Remarkably, the linking of [B12H12]2- and COSAN into the complexes made them more soluble without loosing their luminescence properties. Living B16F10 cells were treated with all the compounds to determine their staining fluorescent properties; the compounds bearing the aliphatic chain showed a reduced staining capacity with the formation of aggregates. Noticeable, the presence of each boron cluster in the complexes structure produces a different staining effect; those bearing [B12H12]2- produce extraordinary nucleoli and cytoplasmic staining, while the COSAN-containing dyes are only detected in the cytoplasm. The remarkable fluorescence staining properties showed by theses organotin compounds make them excellent candidates for fluorescent bioimaging in vitro.
      PubDate: 2018-01-16T12:20:34.992796-05:
      DOI: 10.1002/chem.201705804
       
  • Synthesis of multifunctional spirocyclic azetidines, and their application
           in drug discovery.
    • Authors: Alexander Kirichok; Irina Shton, Irina Pishel, Sergey Zozulya, Petro Borysko, Vladimir Kubyshkin, Olha Zaporozhets, Andrei Tolmachev, Pavel Mykhailiuk
      Abstract: Spirocyclic polyfunctional azetidines have been synthesized and validated in drug discovery. Spirocyclic analogue of the anesthetic drug Bupivacaine with 5-times smaller toxicity was developed.
      PubDate: 2018-01-16T10:56:29.935537-05:
      DOI: 10.1002/chem.201800193
       
  • Real-Time Visualization of Lysosome Destruction Using a Photosensitive
           Toluidine Blue Nanogel
    • Authors: Weiqi Zhang; Ching-Hsuan Tung
      Abstract: Breaking the lysosome helps its sequestered payloads access their molecular targets in cells and thus enhances the intracellular drug delivery. Current strategies for lysosomal escape involve direct physical interactions with the lipid membrane. These interactions pose a systemic toxicity and uncontrolled membrane rupture risk. Here, we report a light-detonated lysosome disruption using a hyaluronan (HA) nanogel packed with toludine blue (TB). The HA/TB nanogel is concentrated within the lysosomes. The applied light assists TB in generating reactive oxygen species and destroying the lysosome in situ, both in cells and isolated lysosomes. Real time fluorescent tracking reveals that quenched TB fluorescence recovers along with lysosome explosion, relocates to the nucleus, and is presented as a fluorescent sparkling in cells. This HA/TB, composed of all clinically approved materials, represents a biocompatible and facile strategy to “bomb” lysosomes in a spatiotemporally controlled fashion.Light-triggered precision bombing of lysosome is achieved by toluidine blue (TB)-loaded hyaluronan (HA) nanogel (HA/TB). The detonation of the lysosome-entrapped nanogel and release of lysosomal contents can be monitored in real time.
      PubDate: 2018-01-16T10:26:19.548142-05:
      DOI: 10.1002/chem.201705697
       
  • Mechanochromic Polymers that Turn Green upon the Dissociation of
           Diarylbibenzothiophenonyl: The Missing Piece toward Rainbow
           Mechanochromism
    • Authors: Kuniaki Ishizuki; Hironori Oka, Daisuke Aoki, Raita Goseki, Hideyuki Otsuka
      Abstract: Mechanochromic polymers, i.e., polymers sensitive to mechanical impact, promise great potential for applications in damage sensors. In particular, radical-type mechanochromic polymers, which produce colored radical species in response to mechanical stress, may enable not only the visualization of mechanical stress, but also its quantitative evaluation by electron paramagnetic resonance analysis. In this work, a radical-type mechanochromic polymer that exhibits a color change from white to green upon dissociation of a diarylbibenzothiophenonyl moiety at the mid-point of a polystyrene chain is presented, and its mechanochromic behavior examined. Mechanochromic materials that show a variety of colors ('rainbow colors') in response to mechanical stress were prepared by simply mixing radical-type mechanochromic polymers of primary colors.
      PubDate: 2018-01-16T10:20:39.251841-05:
      DOI: 10.1002/chem.201800194
       
  • Interrogating Protein Phosphatases with Chemical Activity Probes
    • Authors: Garrett Casey; Cliff Stains
      Abstract: Protein phosphatases, while long overlooked, have recently become appreciated as drivers of both normal- and disease-associated signaling events. As a result, the spotlight is now turning torwards this enzyme family and efforts geared towards the development of modern chemical tools for studying these enzymes are well underway. This minireview focuses on the evolution of chemical activity probes, both optical and covalent, for the study of protein phosphatases. Small-molecule probes, global monitoring of phosphatase activity through the use of covalent modifiers, and targeted fluorescence-based activity probes are discussed. We conclude with an overview of open questions in the field and highlight the potential impact of chemical tools for studying protein phosphatases.
      PubDate: 2018-01-16T10:20:34.081298-05:
      DOI: 10.1002/chem.201705194
       
  • Understanding Local Structure versus Long-Range Structure: The Case
           of UO2
    • Authors: Lionel Desgranges; Yue Ma, Philippe Garcia, Gianguido Baldinozzi, David Siméone, Henry E. Fischer
      Abstract: A recent trend in the development of new optimized materials makes use of crystalline domains having nanometer sizes for which characterization methods at the atomic scale are mandatory. Amongst them is pair-distribution function analysis (PDF-analysis), a diffraction technique that has already shown that a short-range or “local” atomic structure of a given domain, having a lower symmetry than the average long-range structure, often exists in many compounds having valuable properties for industrial applications, such as pyrochlores, spinels, and doped ceria among others. However, the manner by which these domains are arranged to produce the average long-range structure is still an open question. Herein, the first structural model that accounts for both the local structure (inside a given domain) and the long-range structure (averaged over all domains) that is observed in the PDF of uranium dioxide is presented. The structural model describes domain walls in such a way as to preserve the uranium coordination polyhedron and to obey the needed symmetry rules. The proper description of domain walls is an important step in the understanding and the modelling of nanostructured materials.Domain Patterning in UO2: A structural model that accounts for both the local structure (inside a given domain) and the long-range structure (averaged over all domains) that is observed for uranium dioxide is presented. The structural model describes domain walls in such a way as to preserve the uranium coordination polyhedron and to obey the needed symmetry rules. The proper description of domain walls is an important step in the understanding and the modelling of nanostructured materials.
      PubDate: 2018-01-16T10:16:21.769528-05:
      DOI: 10.1002/chem.201705674
       
  • Multilayer Cucurbit[6]uril-Based Magnetic Nanoparticles Prepared by
           Host–Guest Interaction: Remarkable Adsorbent for Low Density Lipoprotein
           Removal from Plasma
    • Authors: Dandan Jiang; Xiqian Li, Qiong Jia
      Abstract: Efficient removal of low density lipoprotein (LDL) is a key challenge due to its high level in plasma as a primary risk factor in the pathogenesis of atherosclerotic cardiovascular disease. In this work, a facile synthesis strategy based on host–guest interactions was developed to prepare multilayer cucurbit[6]uril-based magnetic nanoparticles, MNPs-(HA-DAH5/HA-CB[6]5). The compound was employed as a blood purification material for the removal of LDL from plasma because it had good blood compatibility and could be easily separated with an external magnet. The efficient removal of LDL was attributed to the electrostatic interactions between the positive charged apoB-100 domain of LDL and the negative charged adsorbent. Moreover, the prepared material exhibited high recyclability and could release LDL in physiological saline for recyclable use. MNPs-(HA-DAH5/HA-CB[6]5) offered promising perspectives and broad applications in extracorporeal treatment for the removal of LDL.A facile synthetic strategy based on host–guest interactions was developed to prepare multilayer cucurbit[6]uril-based magnetic nanoparticles, MNPs-(HA-DAH5/HA-CB[6]5). The compound was employed as a blood purification material for the removal of LDL from plasma because it had good blood compatibilitiy and could be easily separated with an external magnet.
      PubDate: 2018-01-16T10:12:59.056758-05:
      DOI: 10.1002/chem.201705280
       
  • Fluorine-Containing Silsesquioxane-Based Hybrid Porous Polymers Mediated
           by Bases and Their Use in Water Remediation
    • Authors: Mingtao Ge; Hongzhi Liu
      Abstract: Two different silsesquioxane-based porous polymers (FHPPs), namely FHPP-1 and FHPP-2, have been prepared, respectively, by changing the acid scavenger from sodium bicarbonate to triethylamine in the Heck reaction between octavinylsilsesquioxane (OVS) and 1,4-dibromotetrafluorobenzene. It was observed that defluorination occurred in the case of triethylamine. FHPP-1 possesses a higher surface area of 600 m2 g−1 and a hierarchical porous structure; in contrast, FHPP-2 possesses a SBET value of 325 m2 g−1 and a microporous structure. This work provides a new approach to the preparation and tuning of fluorine-containing porous polymers based on silsesquioxanes. These porous materials were employed to remove dyes and a heavy metal from water, showing good binding efficiencies.Tuning silsesquioxanes: Two different silsesquioxane-based porous polymers (FHPPs), namely FHPP-1 and FHPP-2, have been prepared by the Heck reaction between octavinylsilsesquioxane (OVS) and 1,4-dibromotetrafluorobenzene using sodium bicarbonate or triethylamine, respectively, as the acid scavenger (see scheme). It was observed that defluorination occurred in the case of triethylamine. This work provides a new approach to the preparation and tuning of fluorine-containing porous polymers based on silsesquioxanes.
      PubDate: 2018-01-16T10:12:45.903114-05:
      DOI: 10.1002/chem.201705192
       
  • All-Solid-State Mechanochemical Synthesis and Post-Synthetic
           Transformation of Inorganic Perovskite-type Halides
    • Authors: Provas Pal; Sujoy Saha, Ananya Banik, Arka Sarkar, Kanishka Biswas
      Abstract: All-inorganic and hybrid perovskite type halides are generally synthesized by solution-based methods, with the help of long chain organic capping ligands, complex organometallic precursors, and high boiling organic solvents. Herein, a room temperature, solvent-free, general, and scalable all-solid-state mechanochemical synthesis is demonstrated for different inorganic perovskite type halides, with versatile structural connectivity in three (3D), two (2D), and zero (0D) dimensions. 3D CsPbBr3, 2D CsPb2Br5, 0D Cs4PbBr6, 3D CsPbCl3, 2D CsPb2Cl5, 0D Cs4PbCl6, 3D CsPbI3, and 3D RbPbI3 have all been synthesized by this method. The all-solid-state synthesis is materialized through an inorganic retrosynthetic approach, which directs the decision on the solid-state precursors (e.g., CsX and PbX2 (X=Cl/Br/I) with desired stoichiometric ratios. Moreover, post-synthetic structural transformations from 3D to 2D and 0D perovskite halides were performed by the same mechanochemical synthetic approach at room temperature.Daily grind: Inorganic perovskite-type halides with different structural connectivity were synthesized by a simple, room temperature, scalable all-solid-state mechanochemical grinding method. Post synthetic structural transformations from 3D to 2D and 0D halides and vice-versa have been achieved by the same all-solid-state synthesis.
      PubDate: 2018-01-16T10:10:29.03653-05:0
      DOI: 10.1002/chem.201705682
       
  • Domino Ring Expansion: Regioselective Access to 9-Membered Lactones with a
           Fused Indole Unit from 2-Nitrophenyl-1,3-cyclohexanediones
    • Authors: David Reyes Loya; Alexandre Jean, Morgan Cormier, Catherine Fressigné, Stefano Nejrotti, Jérôme Blanchet, Jacques Maddaluno, Michaël De Paolis
      Abstract: The domino anionic fragmentation of 2-nitrophenyl-1,3-cyclohexanediones containing an electrophilic appendage such as aldehyde and epoxide is disclosed. This reaction, initiated by a series of nucleophiles, involves the generation of an intermediate hydroxylate followed by the regioselective formation and fragmentation of an intermediate lactolate into enolate. This strategy, devoid of any protecting group, enlarges the initial ring and provides an original access to decorated 9-membered lactones with a fused indole unit.The domino ring expansion of 2-nitrophenyl-1,3-cyclohexanediones connected to an electrophilic appendage–aldehyde and epoxide–into 9-membered lactones was developed. Regio- and stereoselectivity were observed upon treatment with carbon, aza, bromide, and hydride nucleophiles, giving access to highly substituted lactones.
      PubDate: 2018-01-16T10:05:59.860074-05:
      DOI: 10.1002/chem.201705645
       
  • Switching Multivalent DNA Complexation using Metal-Controlled Cationic
           Supramolecular Self-Assemblies
    • Authors: Wojciech Drożdż; Yannick Bessin, Virginie Gervais, Xiao-Yu Cao, Jean-Marie Lehn, Artur R. Stefankiewicz, Sébastien Ulrich
      Abstract: We provide a proof-of-principle that coordination chemistry drives the in situ self-assembly of an inactive ligand into a multivalent cluster capable of effectively complexing DNA. We show that metal coordination and scavenging can be used to switch the multivalency of the system. Thus, controlled DNA complexation and decomplexation could be achieved.On demand: Metal coordination and scavenging processes enable the switching of multivalent DNA complexation through the controlled self-assembly of cationic grid complexes.
      PubDate: 2018-01-16T10:05:41.914859-05:
      DOI: 10.1002/chem.201705630
       
  • Large Proton-Affinity Enhancements Triggered by Noncovalent Interactions
    • Authors: Carlos Martín-Fernández; M. Merced Montero-Campillo, Ibon Alkorta, Manuel Yáñez, Otilia Mó, José Elguero
      Abstract: High affinity: The proton affinity (PA) of the OH group of YHxOH compounds is always increased by noncovalent interaction (NCI) with a Lewis base (LB; see figure). This PA enhancement depends on the type of NCI. Weak NCIs can give rise to PA enhancements equal to or even larger than strong NCIs. The binding energies of protonated species play a major role in the case of sigma-hole interactions.
      PubDate: 2018-01-16T10:01:10.733811-05:
      DOI: 10.1002/chem.201705047
       
  • Establishing the Critical Role of Oriented Aggregation in Molecular Solid
           State Fluorescence Enhancement
    • Authors: P. Srujana; T. P. Radhakrishnan
      Abstract: The general occurrence of fluorescence emission quenching in molecular aggregates is circumvented in select classes of molecules. This has largely been attributed to the rigidification of the molecule and its environment, which hinders non-radiative excited state energy loss through structural relaxation; since such an effect should in principle apply to most aggregates and crystals, there must clearly be other critical factors that make the select molecules exceptional. Discovery of three crystalline structures of a new push–pull molecule in its enantiomorphic and racemic forms, exhibiting not only very high, but distinctly different solid state fluorescence enhancements, has now allowed a systematic investigation of the role of intramolecular and intermolecular excited state energy loss pathways. Crystallographic, spectroscopic and computational investigations provide a detailed appraisal of the assembly patterns in the crystals, and rigorous establishment of an inverse correlation between intermolecular energy transfer and solid state fluorescence. The study provides a clear visualization of the critical role of oriented molecular aggregation in solid state fluorescence efficiency enhancement.Orientation-controlled fluorescence: Three crystalline structures of a new push–pull molecule in its enantiomorphic and racemic forms show not only very large but also distinctly different enhancement of the fluorescence emission over the solution. The critical role of specific relative molecular orientations and hence intermolecular energy transfer in effecting the enhancement is established, demonstrating that intramolecular factors alone are insufficient to understand the phenomenon.
      PubDate: 2018-01-16T10:00:39.659471-05:
      DOI: 10.1002/chem.201705041
       
  • Acid-Triggered O−O Bond Heterolysis of a Nonheme FeIII(OOH) Species for
           the Stereospecific Hydroxylation of Strong C−H Bonds
    • Authors: Joan Serrano-Plana; Ferran Acuña-Parés, Valeria Dantignana, Williamson N. Oloo, Esther Castillo, Apparao Draksharapu, Christopher J. Whiteoak, Vlad Martin-Diaconescu, Manuel G. Basallote, Josep M. Luis, Lawrence Que, Miquel Costas, Anna Company
      Abstract: A novel hydroperoxoiron(III) species [FeIII(OOH)(MeCN)(PyNMe3)]2+ (3) has been generated by reaction of its ferrous precursor [FeII(CF3SO3)2(PyNMe3)] (1) with hydrogen peroxide at low temperatures. This species has been characterized by several spectroscopic techniques and cryospray mass spectrometry. Similar to most of the previously described low-spin hydroperoxoiron(III) compounds, 3 behaves as a sluggish oxidant and it is not kinetically competent for breaking weak C−H bonds. However, triflic acid addition to 3 causes its transformation into a much more reactive compound towards organic substrates that is capable of oxidizing unactivated C−H bonds with high stereospecificity. Stopped-flow kinetic analyses and theoretical studies provide a rationale for the observed chemistry, a triflic-acid-assisted heterolytic cleavage of the O−O bond to form a putative strongly oxidizing oxoiron(V) species. This mechanism is reminiscent to that observed in heme systems, where protonation of the hydroperoxo intermediate leads to the formation of the high-valent [(Porph.)FeIV(O)] (Compound I).Reaction of a novel FeIII(OOH) species with acid makes this species capable of hydroxylating strong C−H bonds in a stereospecific manner. Stopped-flow kinetic analyses and theoretical studies provide a rationale for the observed chemistry, an acid-assisted heterolytic cleavage of the O−O bond to form a strongly oxidizing oxoiron(V) species.
      PubDate: 2018-01-16T10:00:33.995088-05:
      DOI: 10.1002/chem.201704851
       
  • Synthesis and X-Ray Crystallographic Characterisation of Frustum-Shaped
           Ligated [Cu18H16(DPPE)6]2+ and [Cu16H14(DPPA)6]2+ Nanoclusters and Studies
           on Their H2 Evolution Reactions
    • Authors: Jiaye Li; Howard Z. Ma, Gavin E. Reid, Alison J. Edwards, Yuning Hong, Jonathan M. White, Roger J. Mulder, Richard A. J. O'Hair
      Abstract: We report new structural motifs for Cu nanoclusters that conceptually represent seed crystals for large face-centred cubic (FCC) crystal growth. Kinetically controlled syntheses, high resolution mass spectrometry experiments for determination of the dication formulae and crystallographic characterisation were carried out for [Cu18H16(DPPE)6][BF4][Cl] (DPPE=bis(diphenylphosphino)ethane) and [Cu16H14(DPPA)6][(BF4)2] (DPPA=bis(diphenylphosphino)amine) polyhydrido nanoclusters, which feature the unprecedented bifrustum and frustum metal-core architecture in metal nanoclusters. The Cu18 nanocluster contains two Cu9 frustum cupolae and the Cu16 nanocluster has one Cu9 frustum cupola and a Cu7 distorted hexagonal-shape base. Gas-phase experiments revealed that both Cu18H16 and Cu16H14 cores can spontaneously release H2 upon removal of one bisphosphine capping ligand.Frustum-shaped ligated nanoclusters: The reduction of CuI precursors yielded the smallest triangular frustum-shaped Cu polyhydrido nanoclusters, [Cu18H16(DPPE)6][BF4][Cl] and [Cu16H14(DPPA)6][(BF4)2]. The Cu nanoclusters maintained their metal core after the complete hydride loss in the gas phase.
      PubDate: 2018-01-16T09:56:33.449463-05:
      DOI: 10.1002/chem.201705448
       
  • Recent Advances in Micro-/Nanostructured Metal–Organic Frameworks
           towards Photonic and Electronic Applications
    • Authors: Xiaogang Yang; Xianqing Lin, Yong Sheng Zhao, Dongpeng Yan
      Abstract: Micro- and nanometer-sized metal–organic frameworks (MOFs) materials have attracted great attention due to their unique properties and various potential applications in photonics, electronics, high-density storage, chemo-, and biosensors. The study of these materials supplies insight into how the crystal structure, molecular components, and micro-/nanoscale effects can influence the performance of inorganic–organic hybrid materials. In this Minireview article, we introduce recent breakthroughs in the controlled synthesis of MOF micro-/nanomaterials with specific structures and compositions, the tunable photonic and electronic properties of which would provide a novel platform for multifunctional applications. Firstly, the design strategies for MOFs based on self-assembly and crystal engineering principles are introduced. Attention is then focused on the methods of fabrication of low-dimensional MOF micro-/nanostructures. Their new applications including two-photon excited fluorescence, multi-photon pumped lasing, optical waveguides, nonlinear optical (NLO), and field-effect transistors are also outlined. Finally, we briefly discuss perspectives on the further development of these hybrid crystalline micro-/nanomaterials.Photonic MOFs: Recent breakthroughs in the controlled synthesis of metal–organic frameworks (MOFs) micro-/nanomaterials with specific structures and compositions are introduced, the tunable photonic and electronic properties of which would provide a novel platform for multifunctional applications.
      PubDate: 2018-01-16T09:56:22.425741-05:
      DOI: 10.1002/chem.201704650
       
  • Efficient Reduction of CO2 to CO Using Cobalt–Cobalt Oxide
           Core–Shell Catalysts
    • Authors: Guoheng Yin; Xiaotao Yuan, Xianlong Du, Wei Zhao, Qingyuan Bi, Fuqiang Huang
      Abstract: The route of converting CO2 to CO by reverse water-gas shift (RWGS) reaction is of particular interest due to the direct use of CO as feedstock in many significant industrial processes. Here, an engineered cobalt–cobalt oxide core–shell catalyst (Co@CoO) with nanochains structure has been made for the efficient reduction of CO2 to useful CO. Owing to the excellent performance for H2 activation of metal nanoparticles and the enhanced absorption and activation for CO2 molecule of defective metal oxides, the unique synergistic effect of metallic Co and encapsulating coordinatively unsaturated CoO species shows high performance for clean generation of CO under moderate and practical conditions. Furthermore, with N-dopant into the defective CoO shell, the Co@CoO-N achieves the highest conversion of 19.2 % and an exceptional CO evolution rate of 96 mL min−1 gcat−1 at 523 K with a gas hourly space velocity (GHSV) of 42,000 mL gcat−1 h−1, which is comparable with the previously reported materials under identical conditions.Co-Co COoperation: The unique synergistic effect of metallic Co and encapsulating coordinatively unsaturated CoO species with N-dopant in Co@CoO-N can achieve the high performance for clean generation of CO from CO2 reduction.
      PubDate: 2018-01-16T09:56:10.14663-05:0
      DOI: 10.1002/chem.201704596
       
  • Reactions of an Al/P Frustrated Lewis Pair with α,β-Unsaturated Carbonyl
           Compounds - FLPs as Efficient 2e Reductants with the Formation of
           Enolates, a cis-Enediolate and an Allene
    • Authors: Werner Uhl; Merten Lange, Jonas C. Tendyck, Philipp Wegener, Alexander Hepp, Ernst Ulrich Würthwein
      Abstract: The Al/P based FLP Mes2P-C(AltBu)2=C(H)Ph (1) reacted as an efficient 2e reductant with benzil to afford a cis-enediolate which is coordinated to the FLP via P-O and Al-O bonds and formation of a seven-membered heterocycle (2). The P atom is oxidised from +III to +V. Similar heterocycles (3a to 3f) were formed when 1 was treated with various enones (acroleine, acrylate, acrylamide). The resulting enolates are bound to the FLP via P-C and Al-O bonds. Cyclopropenone gave an adduct (4) with the C=O bond coordinated by P and Al. Ynones gave a fascinating variety of different structures. 1,3-Diphenylprop-2-yn-1-one afforded a remarkable allene type moiety with two cumulated C=C bonds (5), 3-hexyn-2-one yielded a ligand with two conjugated C=C bonds by C-H bond activation at the carbonyl methyl group (7), and 4-(trimethylsilyl)-3-butyn-2-one reacted by C-H bond cleavage, formation of an enolate group with a terminal C=C bond and shift of the proton to the P atom (8). The C≡C bond was not affected. The allene compound 5 rearranged at elevated temperature and day-light by formation of a tricyclic compound via C-H bond activation and C-C bond formation. DFT calculations on this unusual rearrangement suggest insertion of the central allene C atom into the C-H bond of a methyl group and the intermediate formation of a three-membered C3 ring.
      PubDate: 2018-01-16T07:55:28.993377-05:
      DOI: 10.1002/chem.201706089
       
  • A Combined Photochemical and Multi-Component Reaction Approach to
           Precision Oligomers
    • Authors: Waldemar Konrad; Fabian Raphael Blößer, Katharina Wetzel, Andreas Boukis, Michael Meier, Christopher Barner-Kowollik
      Abstract: We introduce an avenue for the convergent synthesis of linear monodisperse sequence-defined oligomers via a unique approach, combining the Passerini three-component reaction (P 3CR) and a Diels-Alder reaction based on photo-caged dienes. Based on a Passerini linker unit carrying an isocyano group for chain extension via P 3CR and a maleimide moiety for photo-enol conjugation enabling a modular approach for chain extension. Monodisperse oligomers are accessible in a stepwise fashion by switching between both reaction types. Employing sebacic acid as a core unit allows for the synthesis of a library of symmetric sequence-defined oligomers. Consisting of alternating P-3CR and photo-blocks with molecular weights up to 3532.16 g mol-1, the oligomers demonstrate the successful switching from P-3CR to photo-enol conjugation. In depth characterization is carried out including SEC, high resolution mass spectrometry (ESI-MS) and NMR, evidencing the monodisperse nature of the precision oligomers.
      PubDate: 2018-01-16T07:51:25.366199-05:
      DOI: 10.1002/chem.201705939
       
  • 9,9'-Bifluorenylidene Cored Perylene Diimide Acceptors for As-cast
           Non-fullerene Organic Solar Cells: the Isomeric Effect on Optoelectronic
           Properties
    • Authors: Yuan Zhao; Huan Wang, Shengpeng Xia, Feng Zhou, Zhenghui Luo, Jiajia Luo, Feng He, Chuluo Yang
      Abstract: Two different non-fullerene small molecule acceptors, named m-PIB and p-PIB based on 9,9'-bifluorenylidene (BF) and perylene diimide (PDI) were designed and synthesized. Four β-substituted PDIs were linked to 9,9'-bifluorenylidene in different positions. Based on the analysis of density function theory (DFT), p-PIB exhibited reduced intramolecular twisting between the perylene diimide moieties, more delocalized wave function and sufficiently wider π-electron delocalization compared to m-PIB. The absorption ability of p-PIB was enhanced due to the increased intermolecular interaction. By blending p-PIB with PTB7-Th, organic solar cells (OSCs) based on p-PIB obtained a maximum PCE of 5.95% without any treatments. Due to the improved and balanced hole and electron mobilities, the short-circuit current and fill factor of OSCs based on PTB7-Th and p-PIB were significantly increased. The AFM and TEM results revealed that the PTB7-Th: p-PIB film had favorable nanoscale phase separation and formed bicontinuous interpenetrating network.
      PubDate: 2018-01-16T05:51:23.76898-05:0
      DOI: 10.1002/chem.201705480
       
  • N-terminal Cu Binding Motifs Xxx-Zzz-His (ATCUN) and Xxx-His and their
           derivatives: Chemistry, Biology and Medicinal Applications.
    • Authors: Peter Faller; Paulina Gonzalez, Karolina Bossak, Ewelina Stefaniak, Christelle Hureau, Laurent Raibaut, Wojciech Bal
      Abstract: Peptides and proteins with N-terminal amino acid sequences NH2-Xxx-His (XH) and NH2-Xxx-Zzz-His (XZH) form well established high affinity CuII-complexes. Key examples are Asp-Ala-His (in serum albumin) and Gly-His-Lys, the wound healing factor. This opens a straightforward way to add a high affinity CuII-binding site to almost any peptide or protein, by chemical or recombinant approaches. Thus, these motifs, NH2-Xxx-Zzz-His in particular, have been used to equip peptides and proteins with a multitude of functions based on the redox activity of Cu, including nuclease, protease, glycosidase, or oxygen activation, useful in anticancer or antimicrobial drugs. More recent research suggest novel biological function, mainly based on the redox inertness of CuII in XZH, like PET imaging (with 64Cu), chelation therapies (for instance in Alzheimer's disease and other types of neurodegeneration), antioxidant units, Cu transporters and activation of biological functions by strong CuII binding. This review gives an overview on the chemical properties of Cu-XH and -XZH motifs and discusses the pros and cons for the vast and different biological applications, and how they could be improved depending on the application.
      PubDate: 2018-01-16T05:51:06.255369-05:
      DOI: 10.1002/chem.201705398
       
  • Hierarchy of Asymmetry at Work: Chain-Dependent Helix-to-Helix
           Interactions in Supramolecular Polymers
    • Authors: Sandra Díaz-Cabrera; Yeray Dorca, Joaquín Calbo, Juan Aragó, Rafael Gómez, Enrique Ortí, Luis - Sanchez
      Abstract: A detailed investigation of the hierarchy of asymmetry operating in the self-assembly of achiral (1) and chiral ((S)-2 and (R)-3) 1,3,5-triphenylbenzenetricarboxamides (TPBAs) is reported. The aggregation of these TPBAs is conditioned by the point chirality at the peripheral side chains for (S)-2 and (R)-3. An efficient helix-to-helix interaction that goes further in the organization of fibrillar bundles has been experimentally detected and theoretically supported only for the achiral TPBA 1. The effective interdigitation of the achiral aliphatic side chains produces a social self-sorting to form preferentially heterochiral macromolecular aggregates
      PubDate: 2018-01-16T05:50:36.87622-05:0
      DOI: 10.1002/chem.201706070
       
  • Brønsted Acid-Catalyzed Tandem Cyclizations of Tryptamine-Ynamides
           Yielding 1H-Pyrrolo[2,3-d]carbazole Derivatives
    • Authors: Yanshi Wang; Jingsheng Lin, Xiaoyu Wang, Guanghui Wang, Xinhang Zhang, Bo Yao, Yuandong Zhao, Pengfei Yu, Bin Lin, Yongxiang Liu, Maosheng Cheng
      Abstract: Invited for the cover of this issue are the groups of Yongxiang Liu and Maosheng Cheng at Shenyang Pharmaceutical University. The image depicts a tetracyclic indoline, a core scaffold in a series of indole alkaloids. Read the full text of the article at 10.1002/chem.201705189.“…the inherent tendency of C−C bond migration through Wagner–Meerwein rearrangement to generate a tricyclic fused ring system was circumvented by an instantaneous intramolecular nucleophilic trap to indoleninium.” Read more about the story behind the cover in the Cover Profile and about the research itself on page ▪▪ ff. (
      DOI : 10.1002/chem.201705189).
      PubDate: 2018-01-16T03:51:13.213905-05:
       
  • Asymmetric Total Synthesis of (−)-Stemonamine and Its Stereochemical
           Stability
    • Authors: Satoshi Fujita; Keisuke Nishikawa, Takayuki Iwata, Taishi Tomiyama, Hiroshi Ikenaga, Kenji Matsumoto, Mitsuru Shindo
      Abstract: The first asymmetric total synthesis of (−)-stemonamine is described. The key reactions included intramolecular acylation to construct the seven-membered ring and a tandem [2+2] cycloaddition-Dieckmann condensation reaction using an ynolate to form the fully substituted cyclopentenone moiety. Racemization and epimerization of the natural product were first experimentally demonstrated.A pioneering synthesis: The first total synthesis of nonracemic (−)-stemonamine is achieved in 17 steps from known compounds. Key reactions include intramolecular acylation and ynolate-initiated tandem [2+2] cycloaddition-Dieckmann condensation.
      PubDate: 2018-01-16T03:51:05.482165-05:
      DOI: 10.1002/chem.201706057
       
  • From Carboxytelomerization of 1,3-Butadiene to Linear α,ω-C10-Diester
           Combinatoric Approaches for an Efficient Synthetic Route
    • Authors: Dennis Vogelsang; Björn A. Raumann, Kevin Hares, Andreas J. Vorholt
      Abstract: Two novel reaction pathways were tested to synthesize the linear α,ω-C10-diester exclusively from three basic reagents: 1,3-butadiene, carbon monoxide and methanol. Therefore, carboxytelomerization of 1,3-butadiene and methanol was merged with methoxycarbonylation in two different ways to obtain highly linear C10-diester. Through a palladium-based and -assisted tandem catalytic system, 22 % yield of the desired C10-diester was obtained without isolating the intermediates. Subsequently, the limitations of the novel assisted tandem catalytic concept were uncovered and based on that, a two-step reaction regime was established. By optimization of the carboxytelomerization, the C9-monoester as intermediate could be formed in nearly quantitative yields and excellent linearity. In a second reaction step, the isolated monoester was successfully converted by methoxycarbonylation into the desired linear C10-diester in overall yields up to 84 %.A linear approach: Two novel efficient reaction pathways for the synthesis of linear C10-diester directly based on 1,3-butadiene, carbon monoxide and methanol by palladium-catalysed carboxytelomerization and methoxycarbonylation are presented.
      PubDate: 2018-01-16T03:31:06.350846-05:
      DOI: 10.1002/chem.201705381
       
  • Efficient Buchwald–Hartwig–Migita Cross-Coupling for DNA
           Thioglycoconjugation
    • Authors: Nicolas Probst; Rémy Lartia, Océane Théry, Mouâd Alami, Eric Defrancq, Samir Messaoudi
      Abstract: An efficient method for the thioglycoconjugation of iodinated oligonucleotides by Buchwald–Hartwig–Migita cross-coupling under mild conditions is reported. The method enables divergent synthesis of many different functionalized thioglycosylated ODNs in good yields, without affecting the integrity of the other A, C, and G nucleobases.Sweet ODNs: A new strategy for the post functionalization of ODNs is presented. Using Pd-catalysis, the strategy enabled the synthesis of various thioglycosylated ODNs.
      PubDate: 2018-01-16T03:31:01.076545-05:
      DOI: 10.1002/chem.201705371
       
  • Tetraphenylethylene Foldamers with Double Hairpin-Turn Linkers,
           TNT-Binding Mode and Detection of Highly Diluted TNT Vapor
    • Authors: Jia-Bin Xiong; Hai-Tao Feng, Jin-Hua Wang, Chun Zhang, Bao Li, Yan-Song Zheng
      Abstract: Tetraphenylethylene (TPE) foldamers with double hairpin-turn linkers showing an aggregation-induced emission (AIE) effect have been synthesized for the first time. A crystal structure of a foldamer–TNT complex has been obtained, enabling unprecedented direct observation of the interactions between TNT molecules and the chromophores of the foldamer. Instead of π–π stacking interactions, which have often been considered to be the key mechanism in the binding of TNT by chromophoric receptors, strong n–π interactions between the nitro groups of TNT and the aromatic rings of the foldamer have been found. Exceptionally, by addition of 1 % NaF to a suspension of the foldamer in H2O/THF (95:5), the fluorescence quenching efficiency by TNT vapor significantly increased from about 20 % to more than 90 %. Even after diluting TNT-saturated air at 25 °C by a factor of 2×104, an obvious quenching response was observed, indicating that ultratrace TNT vapor (down to 3.4 fg per mL of air) could be detected.A good nose: Novel tetraphenylethylene (TPE) foldamers with double hairpin-turn linkers showing an aggregation-induced emission (AIE) effect have been synthesized. Such a foldamer can form a complex with a molecule of the explosive TNT (see graphic), and the resulting AIE allows the detection of ultratrace TNT vapor at levels as low as 3.4 fg per mL of air.
      PubDate: 2018-01-16T03:30:49.995414-05:
      DOI: 10.1002/chem.201705346
       
  • Isomerization of Allylic Alcohols to Ketones Catalyzed by Well-Defined
           Iron PNP Pincer Catalysts
    • Authors: Tian Xia; Zhihong Wei, Brian Spiegelberg, Haijun Jiao, Sandra Hinze, Johannes G. de Vries
      Abstract: [Fe(PNP)(CO)HCl] (PNP=di-(2-diisopropylphosphanyl-ethyl)amine), activated in situ with KOtBu, is a highly active catalyst for the isomerization of allylic alcohols to ketones without an external hydrogen supply. High reaction rates were obtained at 80 °C, but the catalyst is also sufficiently active at room temperature with most substrates. The reaction follows a self-hydrogen-borrowing mechanism, as verified by DFT calculations. An alternative isomerization through alkene insertion and β-hydride elimination could be excluded on the basis of a much higher barrier. In alcoholic solvents, the ketone product is further reduced to the saturated alcohol.A borrowing pincer: The isomerization of non-activated allylic alcohols to ketones catalyzed by an iron(II) PNP pincer complex (see graphic) is reported. High reaction rates have been achieved, even at room temperature. A self-borrowing hydrogen mechanism has been established on the basis of DFT calculations.
      PubDate: 2018-01-16T03:25:40.082194-05:
      DOI: 10.1002/chem.201705454
       
  • Room-Temperature Phosphorescence in Pure Organic Materials: Halogen
           Bonding Switching Effects
    • Authors: Lu Xiao; Yishi Wu, Zhenyi Yu, Zhenzhen Xu, Jinbiao Li, Yanping Liu, Jiannian Yao, Hongbing Fu
      Abstract: Organic room-temperature phosphorescence (ORTP), when combined with external stimuli-responsive capability, is very attractive for sensors and bio-imaging devices, but remains challenging. Herein, by doping two β-iminoenamine-BF2 derivatives (S-2CN and S-2I) into a 4-iodoaniline (I−Ph−NH2) crystalline matrix, the formation of S-2CN⋅⋅⋅I−Ph−NH2 and S-2I⋅⋅⋅I−Ph−NH2 halogen bonds leads to bright-red RTP emissions from these two host–guest doped crystals (hgDCs) with quantum efficiencies up to 13.43 % and 15.96 %, respectively. Upon treatment with HCl, the competition of I−Ph−NH2⋅HCl formation against S-2I⋅⋅⋅I−Ph−NH2 halogen bonding switches off the red RTP from S-2I/I−Ph−NH2 hgDCs, whereas the stable halogen-bonded S-2CN⋅⋅⋅I−Ph−NH2 ensures red RTP from S-2CN/I−Ph−NH2 hgDCs remains unchanged. A security protection luminescence pattern by using these different HCl-responsive RTP behaviors was designed.I see red: Stimuli-responsive bright-red room-temperature phosphorescence emissions are realized upon incorporating β-iminoenamine-BF2 derivatives into an iodoaniline crystalline matrix. Different HCl-responsive behaviors are recorded through switching halogen-bonding in these doped crystals.
      PubDate: 2018-01-16T03:25:27.998673-05:
      DOI: 10.1002/chem.201705391
       
  • Microsphere Assemblies via Phosphonate Monoester Coordination Chemistry
    • Authors: Kamila J. Bladek; Margaret E. Reid, Hirotomo Nishihara, Farid Akhtar, Benjamin S. Gelfand, George K. H. Shimizu
      Abstract: By complexing a bent phosphonate monoester ligand with cobalt(II), coupled with in situ ester hydrolysis, coordination microspheres (CALS=CALgary Sphere) are formed whereas the use of the phosphonic acid directly resulted in a sheet-like structure. Manipulation of the synthetic conditions gave spheres with different sizes, mechanical stabilities, and porosities. Time-dependent studies determined that the sphere formation likely occurred through the formation of a Co2+ and ligand chain that propagates in three dimensions through different sets of interactions. The relative rates of these assembly processes versus annealing by ester hydrolysis and metal dehydration determine the growth of the microspheres. Hardness testing by nanoindentation is carried out on the spheres and sheets. Notably, no templates or capping agents are employed, the growth of the spheres is intrinsic to the ligand geometry and the coordination chemistry of cobalt(II) and the phosphonate monoester.Micron-scale coordination spheres are formed without any templates or capping agents by using phosphonate monoester linkers with a bent geometry.
      PubDate: 2018-01-16T03:21:40.794247-05:
      DOI: 10.1002/chem.201705985
       
  • Biomass-Derived N-Doped Carbons with Silica Supported Ultrasmall ZnO
           
    • Authors: Bo Chen; Chan Zhang, Libo Niu, Xiaozhen Shi, Huiling Zhang, Xingwang Lan, Guoyi Bai
      Abstract: Chitosan is a sustainable, biodegradable, non-toxic, and inexpensive material most often obtained from chitin as a by-product of seafood processing. This cover feature depicts the sea including the combination of chitosan (blue) entwined around silica gel (pink). Upon calcination, the chitosan transforms into nitrogen-doped carbon materials (grey tubular structures) incorporating ZnO nanoparticles (red balls). A model reaction demonstrating the synthesis of 2-arylbenzimidazoles from benzaldehyde and o-phenylenediamine catalyzed by the hybrid structure is shown. More information can be found in the Full Paper by X. Lan, G. Bai et al. (
      DOI : 10.1002/chem.201704823).
      PubDate: 2018-01-16T03:21:09.576213-05:
       
  • Shape-Persistent [4+4] Imine Cages with a Truncated Tetrahedral Geometry
    • Authors: Jochen C. Lauer; Wen-Shan Zhang, Frank Rominger, Rasmus R. Schröder, Michael Mastalerz
      Abstract: The synthesis of shape-persistent organic cage compounds is often based on the usage of multiple dynamic covalent bond formation (such as imines) of readily available precursors. By careful choice of the precursors geometry, the geometry and size of the resulting cage can be accurately designed and indeed a number of different geometries and sizes have been realized to date. Despite of this fact, little is known about the precursors conformational rigidity and steric preorganization of reacting functional groups on the outcome of the reaction. Herein, the influence of conformational rigidity in the precursors on the formation of a [4+4] imine cage with truncated tetrahedral geometry is discussed.No freedom! The influence of rotational restrictions of reacting groups that enhances the formation of shape-persistent imine cages is discussed. This should suppress the competing generation of nonporous three-dimensional imine-polymers.
      PubDate: 2018-01-16T03:20:58.061794-05:
      DOI: 10.1002/chem.201705713
       
  • Gold(II) Trihalide Complexes from Organogold(III) Precursors
    • Authors: Miguel Baya; Alberto Pérez-Bitrián, Sonia Martínez-Salvador, Antonio Martín, José M. Casas, Babil Menjón, Jesús Orduna
      Abstract: The mononuclear gold(II) halide complexes [AuCl3]− and [AuBr3]− are formed in the gas phase by collision-induced homolytic splitting of the only Au−C bond in the monoalkylgold(III) precursors [CF3AuX3]−. The geometries of the whole series of [AuX3]− complexes (X=F, Cl, Br, I) have been calculated by DFT methods. It has also been found that the neutral AuX2 molecules behave as unsaturated species, showing significant affinity for an additional X− ligand. Moreover, in the open-shell [AuX3]− anions, homolytic splitting of one of the Au−X bonds and formation of the lower-valent [AuX2]− anions is favored over non-reducing halide dissociation. They should therefore be prone to disproportionation.Golden Countdown: Cascaded one-electron reductions are observed in the gas phase for monoalkylgold(III) [CF3AuX3]− complexes (X=Cl, Br) that result from the stepwise homolytic cleavage of Au−C and Au−X bonds. The processes were also studied using DFT methods.
      PubDate: 2018-01-16T03:20:42.74536-05:0
      DOI: 10.1002/chem.201705509
       
  • Selective Transformation of Well-defined Alkenyllithiums to
           Alkenylmagnesiums via Transmetalation
    • Authors: Miaomiao Zhu; Liang Liu, Yongliang Zhang, Hai-Tao Yu, Wen-Xiong Zhang, Zhenfeng Xi
      Abstract: Selective transformation of alkenyllithiums to alkenylmagnesiums via simple transmetalation has been achieved. The synthesis, structure, and mutual transformation of three different organomagnesiums by adding Grignard reagent and/or MgCl2 to dilithio reagents are described. These magical transformations triggered by Grignard reagent and/or MgCl2 are similar to the traditional Face-changing art originating from the Sichuan province of China. More information can be found in the Full Paper by W.-X. Zhang, Z. Xi et al. (
      DOI : 10.1002/chem.201704611).
      PubDate: 2018-01-16T03:20:29.183283-05:
       
  • New stretching method for aligning gels. Its application to the
           measurement Residual Chemical Shift Anisotropies (RCSAs) without the need
           for isotropic shift correction
    • Authors: Roberto Ricardo Gil; Erich Hellemann
      Abstract: An existing gel stretching device is modified, permitting the use of organic solvents for the study of small molecules. Different from the original device, gels are stretched into 4-mm open-ended NMR tubes and then inserted into regular 5-mm NMR tubes. No open-ended tubes are inserted in the NMR probe avoiding the risk of sample leaking. It is also shown that Residual Chemical Shift Anisotropies (RCSAs) measured with the device are free of isotropic shift interferences and corrections for them are not needed during the post-acquisition data analysis. Three internal references for chemical shift were evaluated (CCl4, CBr4 and TMS), being CCl4 the most convenient one to measure RCSAs in CDCl3. RCSAs measured with the modified stretching device using CCl4 as the internal chemical shift reference were enough to determine the relative configuration of three small molecules with an excellent degree of configuration discrimination.
      PubDate: 2018-01-16T01:50:32.534093-05:
      DOI: 10.1002/chem.201704541
       
  • Hierarchical N-Rich Carbon Sponge with Excellent Cycling Performance for
           Lithium-Sulfur Battery at High Rates
    • Authors: Cheng Wang; Mengmeng Zhen, Juan Wang, Xin Wang
      Abstract: Lithium-sulfur batteries (LSBs) are receiving extensive attention because of their high theoretical energy density. However, practical applications of LSBs are still hindered by the rapid capacity decay and short cycle life, especially at high rates. Herein, a highly N-doped (~13.42 at%) hierarchical carbon sponge (HNCS) having strong chemical adsorptions toward lithium polysulfide was fabricated by a simple sol-gel route followed with carbonization. When using the HCNS as the sulfur host material in cathode and HNCS-coated separator as separator, the battery delivers an excellent cycling stability with high specific capacities of 424/326 mAh g−1, low capacity fading rates of 0.033%/0.030% per cycle after 1000 cycles under high rates of 5 and 10 C, respectively, which are superior to other reported carbonaceous materials. These impressive cycling performances indicate that such battery could promote the practical application prospect of LSBs.
      PubDate: 2018-01-15T21:50:45.677528-05:
      DOI: 10.1002/chem.201705515
       
  • Molecular Wire Effects in Phenyleneethynylene Oligomers: Surprising
           Insights
    • Authors: Uwe Heiko Bunz; Marcel Hergert, Markus Bender, Kai Seehafer
      Abstract: We report the synthesis and quenching behavior of a series of water soluble, carboxylate-carrying phenyleneethynylene oligomers - monomer to tetramer - and their polymers and investigate their quenching behavior with different test analytes (paraquat, lead salts, mercury salts, picric acid, methylpyridinium iodide) in water and compare the results to that of the conjugated polymer. We find significant but analyte-dependent enhancement effects. For monovalent quenchers only the molecular wire effect applies but for divalent quenchers multivalency effects are also important.
      PubDate: 2018-01-15T14:20:31.594024-05:
      DOI: 10.1002/chem.201705604
       
  • A metallo pro-drug to target Cu(II) in the context of Alzheimer's disease
    • Authors: Amandine Conte-Daban; Vinita Ambike, Régis Guillot, Nicolas Delsuc, Clotilde Policar, Christelle Hureau
      Abstract: Alzheimer's disease and oxidative stress are connected. In the present communication, we report the use of a Mn(II)-based superoxide dismutase mimic ([MnII(L)]+, 1+) as a pro-drug candidate to target Cu(II) associated events, i.e. Cu(II)-induced formation of reactive oxygen species (ROS) and modulation of the amyloid-beta (Abeta) peptide aggregation. Complex 1+ is able to remove Cu(II) from Abeta, stop ROS and prevent alteration of Abeta aggregation as would do the corresponding free ligand LH. Using 1+ instead of LH in further biological applications would have the double advantage to avoid the cell toxicity of LH and to benefit from its proved SOD-like activity.
      PubDate: 2018-01-15T11:50:24.18227-05:0
      DOI: 10.1002/chem.201706049
       
  • Selective Binding and Precipitation of Cesium Ions from Aqueous Solutions:
           A Size-Driven Supramolecular Reaction
    • Authors: Ravell Bengiat; Benny Bogoslavsky, Daniel Mandler, Joseph Almog
      Abstract: The nuclear disasters of Chernobyl and Fukushima presented an urgent need for finding solutions to treatment of radioactive wastes. Among the by-products of nuclear fission is the radioactive 137Cs, which evokes an environmental hazard due to its long half-life (>30 years) and high solubility in water. In this work, a water-soluble organic ligand, readily obtained from alloxan and 1,3,5-benzenetriol, has been found to selectively bind and precipitate Cs+ ions from aqueous solutions. The special rigid structure of the ligand, which consists of a "tripodal" carbonyl base above and below an aromatic plane, contributes to the size-driven selectivity towards the large Cs+ ions and the formation of a giant, insoluble supramolecular complex. In addition to the ligand's low costs, high yields and effectiveness in precipitating Cs+ ions, the Cs-complex revealed a high endurance to continuous doses of gamma-radiation, increasing its potential to act as a precipitating agent for 137Cs.
      PubDate: 2018-01-15T09:45:22.580758-05:
      DOI: 10.1002/chem.201706181
       
  • Features of Auxiliaries that Enable Native Chemical Ligation beyond
           Glycine and Cleavage via Radical Fragmentation
    • Authors: Simon Ferdinand Loibl; Andre Dallmann, Kathleen Hennig, Carmen Juds, Oliver Seitz
      Abstract: The native chemical ligation (NCL) is an invaluable tool in the total chemical synthesis of proteins. Ligation auxiliaries overcome the requirement for cysteine. However, the reported auxiliaries remained limited to glycine-containing ligation sites and the acidic conditions applied for cleavage of the typically applied N-benzyl-type linkages promote side reactions. With the aim to improve upon both ligation and cleavage, we systematically investigated alternative ligation scaffolds that challenge the N-benzyl dogma. The study revealed that auxiliary-mediated peptide couplings are fastest when the ligation proceeds via 5-membered rather than 6-membered rings. Substituents in α-position of the amine shall be avoided. We observed, perhaps surprisingly, that additional β-substituents accelerated the ligation conferred by the β-mercaptoethyl scaffold. We also describe a potentially general means to remove ligation auxiliaries by treatment with an aqueous solution of triscarboxyethylphosphine (TCEP) and morpholine at pH 8.5. NMR analysis of a 13C-labeled auxiliary showed that cleavage most likely proceeds through a radical-triggered oxidative fragmentation. High ligation rates provided by β-substituted 2-mercaptoethyl scaffolds, their facile introduction as well as the mildness of the cleavage reaction are attractive features for protein synthesis beyond cysteine and glycine ligation sites.
      PubDate: 2018-01-15T09:25:26.025708-05:
      DOI: 10.1002/chem.201705927
       
  • Copper-catalyzed regioselective cleavage of C-X bond and C-H bond: A
           strategy for sulfur dioxide fixation
    • Authors: Daoshan Yang; Pengfei Sun, Wei Wei, Fengjuan Liu, Hui Zhang, Hua Wang
      Abstract: The first example of direct fixation of sulfur dioxide between heteroaryls and aryl halides has been developed via copper-catalyzed regioselective cleavage of C-X and C-H bonds under base-free and ligand-free conditions by using DABSO as a solid and bench-stable sulfur dioxide surrogate. This mild protocol results in double C-S bond-forming reactions from simple precursors in the absence of prefunctionalized organometallic reagents, arenediazonium salts, and iodonium salts which extends the still limited number of sulfur dioxide fixation strategies.
      PubDate: 2018-01-15T08:50:38.136892-05:
      DOI: 10.1002/chem.201705866
       
  • Nickel-Catalyzed C-S Bond Formation via Decarbonylative Thioetherification
           of Esters, Amides and Intramolecular Recombination Fragment Coupling of
           Thioesters
    • Authors: Shao-Chi Lee; Hsuan-Hung Liao, Adisak Chatupheeraphat, Magnus Rueping
      Abstract: A nickel catalyzed cross-coupling protocol for the straightforward C-S bond formation has been developed. Various mercaptans and a wide range of ester and amide substrates bearing various substituents were tolerated in this process which afforded products in good to excellent yields. Furthermore, an intramolecular protocol for the synthesis of thioethers starting from thioesters has been developed. The utility of this protocol has been demonstrated in the synthesis of benzothiophene on the bench top.
      PubDate: 2018-01-15T08:50:28.2821-05:00
      DOI: 10.1002/chem.201705842
       
  • A gold(III) pincer ligand scaffold for the synthesis of binuclear and
           bioconjugated complexes: synthesis and anticancer potential.
    • Authors: Bertrand Benoît; Maria A. O'Connell, Zöe A. E. Waller, Manfred Bochmann
      Abstract: Cyclometalated (C^N^C)Au(III) complexes bearing functionalized N-heterocyclic carbene (NHC) ligands provide a high-yielding, modular route to bioconjugated and binuclear complexes. That methodology has been applied to the synthesis of bioconjugated complexes presenting biotin and 17α-ethynylestradiol vectors, as well as to the synthesis of bimetallic Au(III)/Au(I) complexes. The in vitro antiproliferative activities of these compounds against various cancer cells lines depend on the linker length, with the longer linker being the most potent. The estradiol conjugate AuC6Estra proved to be more toxic against the estrogen receptors positive (ER+) cancer cells than against the ER- cancer cells and non-cancer cells. The bimetallic complex AuC6Au was more selective for breast cancer cells with respect to a healthy cell standard than the monometallic complex AuNHC. The metal uptake study on cells expressing or not biotin and estrogen receptors revealed an improved and targeted delivery of gold for both the bioconjugated complexes AuC6Biot and AuC6Estra compared to the non-vectorised analogue AuNHC. The investigations of the interaction of the bioconjugates and bimetallic complexes with human telomeric G-quadruplex DNA using FRET-melting techniques revealed a reduced ability to stabilize this DNA structure with respect to the non-vectorised analogue AuNHC.
      PubDate: 2018-01-15T08:20:30.029362-05:
      DOI: 10.1002/chem.201705902
       
  • Heterobimetallic complexes for theranostic applications
    • Authors: M. Concepción Gimeno; Vanesa Fernández-Moreira
      Abstract: The design of more efficient anticancer drugs requires a deeper understanding of their biodistribution and mechanism of action. Cell imaging agents could help to gain insight into biological processes and, consequently, the best strategy for attaining suitable scaffolds in which both, biological and imaging properties are maximized. A new concept arises in this field which is the combination of two metal fragments as collaborative partners to provide the precise emissive properties to visualize the cell as well as the optimum cytotoxic activity to build more potent and selective chemotherapeutic agents.
      PubDate: 2018-01-15T07:50:43.696582-05:
      DOI: 10.1002/chem.201705335
       
  • Isomerically Pure Star-Shaped Triphenylene-Perylene Hybrids Involving
           Highly Extended π Conjugation
    • Authors: Edurne Nuin; Vicent Lloret, Konstantin Amsharov, Frank Hauke, Gonzalo Abellán, Andreas Hirsch
      Abstract: The synthesis and characterization of a new type of a highly conjugated heterocyclic π-chromophore, consisting of a central triphenylene core fused with three perylene-monoimide units (star-shaped molecule) is described. By judicious bay-functionalization with tert-butylphenoxy substituents, aggregation was completely prevented in common organic solvents, allowing for a straightforward purification and, for the very first time, the complete separation of the constitutional isomers by HPLC. Both isomers can be easily distinguished by means of several conventional spectroscopic techniques. Furthermore, we have illustrated the absence of supramolecular aggregates and enhanced processability by noncovalent functionalization of graphene substrates, showing an outstanding homogeneity and observing a different doping behavior in both isomers, being possible to distinguished by Raman spectroscopy.
      PubDate: 2018-01-15T07:50:40.758384-05:
      DOI: 10.1002/chem.201705872
       
  • K3Li3Gd7(BO3)9: A New Gadolinium-Rich Orthoborate for Cryogenic Magnetic
           Cooling
    • Authors: Mingjun Xia; Shipeng Shen, Jun Lu, Young Sun, R.K. Li
      Abstract: Magnetic cooling technology based on magnetocaloric effect (MCE) has attracted great interest in obtaining extreme low temperature, e. g. for space exploration. Here we grew a new gadolinium-rich orthoborate K3Li3Gd7(BO3)9 (1) as a promising cryogenic magnetic coolant. It exhibits complicated three dimensional framework constructed from BO3 groups and gadolinium-oxygen chains. The Gd-O chain consists of two types of clusters of Gd3O20 and Gd3O19 interconncetion by Gd(4)O8 polyhydron. Thanks to its high gadolinium concentration, a large -Sm for 1 was obtained as 56.6 J kg-1 K-1 at 2 K and H = 7 T, much larger than that of commercial benchmark Gd3Ga5O12 (GGG) crystal (38.4 J kg-1 K-1), suggesting it to be an excellent MCE material.
      PubDate: 2018-01-15T03:21:17.965593-05:
      DOI: 10.1002/chem.201705669
       
  • Re(bpy)(CO)3Cl Immobilized on Bipyridine-Periodic Mesoporous Organosilica
           for Photocatalytic CO2 reduction
    • Authors: Minoru Waki; Ken-ichi Yamanaka, Soichi Shirai, Yoshifumi Maegawa, Yasutomo Goto, Yuri Yamada, Shinji Inagaki
      Abstract: This paper describes the physicochemical properties of a rhenium (Re) complex [Re(bpy)(CO)3Cl] immobilized on a bipyridine-periodic mesoporous organosilica (BPy-PMO) acting as a solid support. The immobilized Re complex generated a metal-to-ligand charge transfer absorption band at 400 nm. This wavelength is longer than that exhibited by Re(bpy)(CO)3Cl in the polar solvent acetonitrile (371 nm) and is almost equal to that in nonpolar toluene (403 nm). The photocatalytic activity of this heterogeneous Re complex was lower than that of a homogeneous Re complex due to the reduced phosphorescence lifetime resulting from immobilization. However, the catalytic activity was enhanced by the co-immobilization of the ruthenium (Ru) photosensitizer [Ru(bpy)3]2+ on the PMO pore surfaces. Quantum chemical calculations suggest that electron transfer between the Ru and Re complexes occurs via interactions between the molecular orbitals in the pore walls. These results should have applications to the design of efficient heterogeneous CO2 reduction photocatalysis systems.
      PubDate: 2018-01-14T22:15:22.839706-05:
      DOI: 10.1002/chem.201705792
       
  • Identification of the minimal glycotope of Streptococcus pneumoniae 7F
           capsular polysaccharide using synthetic oligosaccharides
    • Authors: Petra Menova; Mauro Sella, Katrin Sellrie, Claney Pereira, Peter H. Seeberger
      Abstract: Streptococcus pneumoniae causes life-threatening diseases including meningitis, pneumonia and sepsis. Existing glycoconjugate vaccines based on purified capsular polysaccharides are widely used and help to prevent millions of deaths every year. Here, we report total synthesis of oligosaccharides resembling portions of the S. pneumoniae serotype 7F (ST7F) capsular polysaccharide repeating unit. To define minimal glycan epitopes, glycan microarrays containing the synthetic oligosaccharides were used to screen human reference serum and revealed that both side chains of the ST7F play a key role in antigen recognition. The identification of protective minimal epitopes is vital to design efficient semi- and fully-synthetic glycoconjugate vaccines.
      PubDate: 2018-01-14T21:50:46.072287-05:
      DOI: 10.1002/chem.201705379
       
  • Cobaltocenylidene, a mesoionic metalloceno carbene, stabilized in a
           gold(III) complex
    • Authors: Benno Bildstein; Stefan Vanicek, Maren Podewitz, Christopher Hassenrück, Michael Pittracher, Holger Kopacka, Klaus Wurst, Thomas Müller, Klaus R. Liedl, Rainer F. Winter
      Abstract: Oxidative addition of cobaltoceniumdiazonium bis(hexafluoridophosphate) with (pseudo)halide aurates afforded gold(III) complexes containing zwitterionic cobaltoceniumide as a ligand. Its selenium derivative, cobaltoceniumselenolate, was obtained by an electrophilic aromatic substitution reaction of iodocobaltocenium iodide with Na2Se. Spectroscopic and structural data in combination with DFT calculations show that this cobaltocenylidene species is a mesoionic carbene quite different from common N-heterocyclic carbenes. Its ligand properties (TEP, singlet-triplet gap, nucleophilicity, π-acidity, Brønsted basicity) are in part comparable to those of cyclic (amino)(alkyl/aryl)carbenes. Electrochemistry shows that the mesoionic cobaltoceniumides are more electron-rich than their parent ferrocenes. The reversible reduction of the tricyanido gold complex appears 50 mV negative of the cobaltocenium/cobaltocene couple while that of the selenide derivative is shifted cathodically by 550 mV.
      PubDate: 2018-01-12T09:52:11.686889-05:
      DOI: 10.1002/chem.201800147
       
  • Fusing Planar Group to a pi-Bowl: Electronic and Molecular Structure,
           Aromaticity and Solid State Packing of Naphthocorannulene and its Anions
    • Authors: Zheng Zhou; Sarah Spisak, Qi Xu, Andrey Rogachev, Zheng Wei, Massimo Marcaccio, Marina A. Petrukhina
      Abstract: Molecular and electronic structure, reduction and coordination abilities of a PAH having a planar naphtho-group fused to the corannulene bowl have been investigated for the first time using a combination of theoretical and experimental tools. A direct comparison of naphtho[2,3-a]corannulene (C28H14, 1) with parent corannulene (C20H10, 2) revealed the effect of framework topology change on electronic properties and aromaticity of 1. Two reversible one-electron reduction processes with the formal reduction potentials at -2.30 V and -2.77 V vs. Fc+/0 were detected by CV measurements, demonstrating accessibility of the corresponding mono- and dianionic states of 1. The products of the mono- and doubly-reduced napththocorannulene were prepared using chemical reduction with Group 1 metals and isolated as sodium and rubidium salts. Their X-ray diffraction study revealed the formation of "naked" mono- and dianions crystallized as solvent-separated ion products with one or two sodium ions as [Na+(18-crown-6)(THF)2][C28H14-] and [Na+(18-crown-6)(THF)2]2[C28H142-] (3·THF and 4·THF, respectively). The dianion of 1 was also isolated as a contact-ion complex with two rubidium countercations, [{Rb+(18-crown-6)}2(C28H142-)] (5·THF). The structural consequences of adding one and two electrons to the carbon framework of 1 are compared for 3, 4 and 5. Changes in aromaticity and charge distribution stemming from the stepwise electron acquisition are discussed based on DFT computational study.
      PubDate: 2018-01-12T09:52:07.146755-05:
      DOI: 10.1002/chem.201705814
       
  • Deracemization of a Racemic Compound Using Tailor-Made Additives
    • Authors: Ton Engwerda; Pim van Schayik, Henjo Jagtenberg, Hugo Meekes, Floris P. J. T. Rutjes, Elias Vlieg
      Abstract: Viedma ripening is a process that combines abrasive grinding of a slurry of crystals with solution phase racemization, resulting in solid phase deracemization. One of the major disadvantages of Viedma ripening is that the desired compound needs to crystallize as a racemic conglomerate, accounting for only 5-10% of all chiral molecules. In this work, we show that use of a chiral additive causes deracemization under conditions in which the compound normally crystallizes as a racemic compound. Although this concerns a single example, it is envisioned that through this new approach the scope of Viedma ripening can be significantly expanded.
      PubDate: 2018-01-12T09:20:21.384196-05:
      DOI: 10.1002/chem.201706088
       
  • Electrophile-Directed Diastereoselective Oxonitrile Alkylations
    • Authors: Fraser Fergusson Fleming; Sergiy Chepyshev, Bhaskar Reddy Pitta, Saidi Reddy Vangala, J. Armando Lujan-Montelongo, Omar Steward
      Abstract: Diastereoselective alkylation of prochiral oxonitrile dianions with secondary alkyl halides efficiently installs two contiguous stereogenic centers. The confluence of nucleophilic trajectory and the electrophile chirality causes distinct steric differences that allow efficient discrimination for one of the six possible conformers. Numerous oxonitrile-derived dianions efficiently displace secondary alkyl halides propagating the electrophile chirality to efficiently install two contiguous tertiary centers. The prevalence of chiral, secondary electrophiles makes the interdigitated alkylation of chiral electrophiles a particularly attractive route because the resulting oxonitriles are readily transformed into bioactive heterocycles.
      PubDate: 2018-01-12T06:50:24.488762-05:
      DOI: 10.1002/chem.201705791
       
  • Self-Assembled 2D Nanoparticles Arrays of interfacial self-assembled
           large-scale densely packed monolayer film with ligand exchanged Au
           nanorods for in situ SERS drugs detection
    • Authors: Liangbao Yang; mei mao, Binbin Zhou, Xianghu Tang, Cheng chen, Meihong Ge, Pan Li, Xingjiu Huang, jinhuai liu
      Abstract: Construction of large area ordered anisotropic nanoparticles monolayer and acquisition of self-assembled interface film are still significant challenges. In this work, we have developed a rapid and valid method to fabricate large-scale close packed nanomaterials at the cyclohexane/water interface in which hydrophilic cetyltrimethylammonium bromide (CTAB) coated nanoparticles, Au nanorods (AuNRs), self-assembled into densely packed two dimensional (2D) arrays by regulating the surface ligand and suitable inducer. Employing PVP to functionalize the AuNRs not only extensively decrease the charge of AuNRs but also diminish the repulsive force. More importantly, we exhibit a general and facile novel technique to transfer interfacial monolayer which through a designed situ cell linked a microfluidic chip, the self-assembled nanofilm could automatically settle on the substrate and directly detected on the situ cell by portable Raman spectrometer. Moreover, close-packed monolayer of self-assembled AuNRs provided massive efficient hotspots to create great surface-enhanced Raman scattering (SERS) enhancement, ensuring the sensitivity and reproducibility as the SERS-active substrate. Furthermore, this strategy was exploited to detect drug molecules in human urine for cyclohexane extracted targets acting as oil phase to form oil/water interface. Portable Raman spectrometer was employed to detect methamphetamine down to 100 ppb levels in human urine, exhibiting excellent practicability.
      PubDate: 2018-01-11T21:56:02.726726-05:
      DOI: 10.1002/chem.201705700
       
  • Ru-Catalyzed Completely Deoxygenative Coupling of 2-Arylethanols through
           Base-Induced Net Decarbonylation
    • Authors: Seetharaman Manojveer; Sebastian J. K. Forrest, Magnus T. Johnson
      Pages: 803 - 807
      Abstract: Substituted arylethanols can be coupled by using a readily available Ru catalyst in a fully deoxygenative manner to produce hydrocarbon chains in one step. Control experiments indicate that the first deoxygenation occurs through an aldol condensation, whereas the second occurs through a base-induced net decarbonylation. This double deoxygenation enables further development in the use of alcohols as versatile and green alkylating reagents, as well as in other fields, such as deoxygenation and upgrading of overfunctionalized biomass to produce hydrocarbons.Double deoxygenation: A fully deoxygenative coupling of primary 2-arylethanols was achieved by combining aldol condensation with a net decarbonylation. Control experiments indicate that the base and its loading have an important cooperative role in the second deoxygenation. The reaction was achieved by using cheap and commercially available [RuCl2(PPh3)3] as a precatalyst.
      PubDate: 2018-01-08T08:35:25.560579-05:
      DOI: 10.1002/chem.201705208
       
  • Front Cover: Quantitative Analysis of the Self-Assembly Process of
           Hexagonal PtII Macrocyclic Complexes: Effect of the Solvent and the
           Components (Chem. Eur. J. 4/2018)
    • Authors: Ayako Baba; Tatsuo Kojima, Shuichi Hiraoka
      Pages: 750 - 750
      Abstract: The self-assembly process of supramolecular coordination rings composed of dinuclear PtII complexes and organic ligands was investigated by an NMR-based quantitative approach (QASAP: quantitative analysis of the self-assembly process), which enabled the monitoring of the growth of oligomers during the self-assembly. Even though the oligomers could adopt various conformations, the macrocycles were assembled without the generation of the oligomers containing more components than the macrocycles. More information can be found in the Full Paper by S. Hiraoka et al. on page 838.
      PubDate: 2017-11-13T04:58:14.270655-05:
      DOI: 10.1002/chem.201704735
       
  • Cover Feature: A One-Step Germole to Silole Transformation and a Stable
           Isomer of a Disilabenzene (Chem. Eur. J. 4/2018)
    • Authors: Crispin R. W. Reinhold; Zhaowen Dong, Jan M. Winkler, Henning Steinert, Marc Schmidtmann, Thomas Müller
      Pages: 751 - 751
      Abstract: An unprecedented germole to silole transformation opened the way for the synthesis of novel silylenes based on a bicyclohexene skeleton, so-called BCH silylenes. The astonishing stability of BCH silylenes results from homoconjugation between the dicoordinated Si atom and a remote C=C bond. This stabilization is more efficient than conventional electron delocalization, indicated by the fact that BCH silylenes are stable derivatives of the global minimum of the C4Si2H6 potential energy surface. More information can be found in the Full Paper by T. Müller et al. on page 848.
      PubDate: 2017-11-02T08:21:28.460458-05:
      DOI: 10.1002/chem.201704980
       
  • Cover Feature: Iron-Catalyzed Hydroborylative Cyclization of 1,6-Enynes
           (Chem. Eur. J. 4/2018)
    • Authors: Natalia Cabrera-Lobera; Patricia Rodríguez-Salamanca, Juan C. Nieto-Carmona, Elena Buñuel, Diego J. Cárdenas
      Pages: 752 - 752
      Abstract: 21st century synthetic methods have to be both inexpensive and environmentally benign. The borylative cyclization herein reported employs a cheap Fe-based catalyst, and allows the use of halogen-free starting materials to provide alkylboronates with complete atom economy. These derivatives are important versatile non-toxic reagents for synthetic applications in different areas. More information can be found in Communication by D. J. Cárdenas et al. on page 784.
      PubDate: 2017-12-19T12:17:28.192416-05:
      DOI: 10.1002/chem.201705800
       
  • Cover Feature: Direct Arylation of Dipyrrolonaphthyridinediones Leads to
           Red-Emitting Dyes with Conformational Freedom (Chem. Eur. J. 4/2018)
    • Authors: Bartłomiej Sadowski; Michał F. Rode, Daniel T. Gryko
      Pages: 753 - 753
      Abstract: Dipyrrolonaphthyridinediones that possess two aryl substituents at positions 3 and 9 can be prepared directly from parent heterocycle by direct arylation. Although benzene rings in the new dyes are only weakly coupled with the key chromophore, the dihedral angles are much smaller in the excited state. As a result, fluorescence is shifted from green–yellow to the far-red/NIR region. The photophysical properties can be controlled by altering the steric and electronic character of the peripheral group. More information can be found in the Full Paper by M. F. Rode, D. T. Gryko et al. on page 855.
      PubDate: 2017-11-13T04:58:01.44803-05:0
      DOI: 10.1002/chem.201704984
       
  • Quantitative Analysis of the Self-Assembly Process of Hexagonal PtII
           Macrocyclic Complexes: Effect of the Solvent and the Components
    • Authors: Ayako Baba; Tatsuo Kojima, Shuichi Hiraoka
      Pages: 754 - 754
      Abstract: Invited for the cover of this issue is the group of Shuichi Hiraoka at the University of Tokyo. The image depicts a stylized view of a hexagonal platinum macrocyclic complex. Read the full text of the article at 10.1002/chem.201702955.“We see many self-assembled architectures in nature and know that self-assembly is one of important phenomena to organize life system.” Read more about the story behind the cover in the Cover Profile and about the research itself on page 838 ff. (
      DOI : 10.1002/chem.201702955).
      PubDate: 2017-11-13T04:58:17.531319-05:
       
  • Amino Acid Coordinated Self-Assembly
    • Authors: Qianli Zou; Xuehai Yan
      Pages: 755 - 761
      Abstract: Self-assembly of highly important biomolecules, such as proteins and peptides, has attracted tremendous interest in supramolecular construction of functional materials. However, as proteins and peptides are often immunogenic and their structures are complex, there is a strong demand to use amino acids as simpler building blocks. Still, mimicking the sophisticated structures and functions of natural materials by self-assembly of simpler and more basic units of biomolecules, such as amino acids, remains a formidable challenge. Inspired by metal-ion-associated crystallization of l-cystine in the urinary system, amino acid coordinated self-assembly is discussed as an original strategy for supramolecular construction of biomimetic materials. The resulting materials possess the features of uniform size, hierarchical architecture, and structural resemblance to biological structures. In addition, the self-assembly process can readily be adapted to simultaneous integration of various functional modules, providing materials with promising properties for biomimetic and biomedical applications.A simple but versatile strategy for supramolecular construction of hierarchical materials is proposed. This novel strategy, namely amino acid coordinated self-assembly, is based on the combination of coordination and other non-covalent interactions by using amino acids and metal ions as the building blocks. The resulting materials show the advantages of uniform and controllable morphology, high stability, structural resemblance to biological structures, and tailored functionality.
      PubDate: 2017-11-28T07:36:28.614176-05:
      DOI: 10.1002/chem.201704032
       
  • Low Molecular Weight Supramolecular Gels Under Shear: Rheology as the Tool
           for Elucidating Structure–Function Correlation
    • Authors: Arnab Dawn; Harshita Kumari
      Pages: 762 - 776
      Abstract: Self-healing low molecular weight supramolecular gels (SMGs) represent an emerging class of smart materials, which can closely mimic the complex biological healing process, such as blood clotting, bone repair or wound healing. However, a lack of understanding of the structure–function correlation in the self-assembly process limits their molecular design and subsequent property tuning. The indispensability of a rheological study on supramolecular gels lies in direct transcription of the assembly property to the viscoelastic behavior of the material. This is similarly relevant to healable and non-healable systems. Thus, using rheology as a tool for elucidating structure–function relationships in self-assembled systems has huge potential. This review article will depict a general introduction of rheology in the field of soft matter including SMGs, followed by representative studies with interpretations, and discussion on future challenges. Altogether, this would be an effort, where an in-depth rheological study complemented with a real-time visualization with the help of microscopy, and introduction of other sophisticated real-time experiments, could be a step forward to capture the mystery of self-assembly process.Under shear: The structure–function relationship in a mechanoresponsive supramolecular gel phase materials is a complex phenomenon to address. An in-depth rheological analysis complemented with a real-time study with the help of sophisticated technique like microscopy could be a step forward to capture the mystery of self-assembly process.
      PubDate: 2017-10-25T10:01:34.600337-05:
      DOI: 10.1002/chem.201703374
       
  • Pillar[5]arene-Based Supramolecular Organic Framework with Multi-Guest
           Detection and Recyclable Separation Properties
    • Authors: Qi Lin; Yan-Qing Fan, Peng-Peng Mao, Lu Liu, Juan Liu, You-Ming Zhang, Hong Yao, Tai-Bao Wei
      Pages: 777 - 783
      Abstract: The selective detection and separation of target ions or molecules is an intriguing issue. Herein, a novel supramolecular organic framework (SOF-THBP) was constructed by bis-thioacetylhydrazine functionalized pillar[5]arenes. The SOF-THBP shows a fluorescent response for Fe3+, Cr3+, Hg2+ and Cu2+ ions. The xerogel of SOF-THBP shows excellent recyclable separation properties for these metal ions and the absorption rates were up to 99.29 %. More interestingly, by rationally introducing these metal ions into the SOF-THBP, a series of metal-ion-coordinated SOFs (MSOFs) such as MSOF-Fe, MSOF-Hg and MSOF-Cu were constructed. These metal ions coordinated MSOFs could selectively sense F−, Br−, and l-Cys, respectively. The detection limits of these MSOFs for F−, Br− and l-Cys were about 10−8 m.Multi-Functional SOFs: A novel supramolecular organic framework (SOF-THBP) was constructed by functionalized pillar[5]arenes. By rationally introducing metal ions into the SOF-THBP, a series of metal-ion-coordinated SOFs (MSOFs) were constructed. The SOF-THBP shows excellent recyclable separation properties for Cr3+, Hg2+, etc. The MSOFs could selectively and sensitively sense F−, Br−, and l-Cys, respectively.
      PubDate: 2017-12-13T04:35:46.038235-05:
      DOI: 10.1002/chem.201705107
       
  • Iron-Catalyzed Hydroborylative Cyclization of 1,6-Enynes
    • Authors: Natalia Cabrera-Lobera; Patricia Rodríguez-Salamanca, Juan C. Nieto-Carmona, Elena Buñuel, Diego J. Cárdenas
      Pages: 784 - 788
      Abstract: We report first Fe-catalyzed hydroborylative cyclization reaction. The process provides one C−C and one C−B bond in a single operation and shows a wide scope, allowing the formation of carbo- and heterocycles containing a homoallylic boryl unit that can be further functionalized. The reaction takes place in smooth conditions, with inexpensive catalytic system and full atom economy since HBpin is the borylation agent, in contrast to our previously reported Pd-catalyzed reaction. Both aryl and alkyl substituted alkynes are reactive, revealing a wide reaction scope. Mechanistic studies suggest the intermediacy of FeII-hydride active catalyst capable to react with the alkyne group prior to alkene insertion, and computational studies suggest the occurrence of barrierless σ-bond metathesis involving HBpin and Fe−C bonds along the catalytic cycle.Making rings with iron: We report the first Fe-catalyzed borylative cyclization reaction, which affords one C−C and one C−B bond allowing the formation of carbo- and heterocycles containing a boryl unit that can be further functionalized. The reaction takes place under mild conditions, with inexpensive catalytic system and full atom economy. Mechanistic studies suggest the intermediacy of FeII-hydride active catalyst capable to react with the alkyne group prior to alkene insertion, and computational studies suggest the occurrence of barrierless σ-bond metathesis involving HBpin and Fe−C bonds along the catalytic cycle.
      PubDate: 2017-11-23T09:26:52.634808-05:
      DOI: 10.1002/chem.201704401
       
  • A Versatile Strategy to Main Chain Sulfur/Selenium-Functionalized
           Polycarbonates by Macro-Ring Closure of Diols and Subsequent Ring-Opening
           Polymerization
    • Authors: Chao Wei; Yan Zhang, Bingkun Yan, Zhengzhen Du, Meidong Lang
      Pages: 789 - 792
      Abstract: Herein, a new class of main chain functionalized aliphatic polycarbonates with sulfur/selenium functional groups on the backbone is reported. Sulfur/selenium-containing cyclic carbonate monomers (MR) are designed and synthesized by enzyme-catalyzed intermolecular macro-ring closure of related diols. The proposed synthetic strategy is tolerant of other functionalities such as N-substituted groups. The ring opening polymerization (ROP) of MR occurs readily as a versatile route to generate a new family of main chain sulfur/selenium substituted aliphatic polycarbonates (PR) with predictable molecular weights (MW), narrow molecular-weight distribution and controlled copolymer composition. The resultant polymers can be oxidized and/or reduced by treatment with hydrogen peroxide (H2O2) or dithiothreitol (DTT), highlighting their potential for applications in the stimuli-responsive field and inflammation/cancer targeting. With these desirable results, it is revealed that this versatile technique can provide a broad-reaching method to the next generation of innovative materials, especially, well-defined biodegradable chalcogen-based main chain functional biomaterials.A versatile and facile synthetic strategy is reported for the preparation of well-defined main-chain-functionalized degradable polymers by the enzyme-catalyzed macro-ring closure of functional diol and subsequent ring-opening polymerization. Using this method, main chain sulfur/selenium-substituted polycarbonates are synthesized for the first time with excellent redox responsiveness. Moreover, this approach could be broadened to other functional diols, effectively expanding the range of accessible main chain functional polymers.
      PubDate: 2017-12-27T10:16:09.850547-05:
      DOI: 10.1002/chem.201704301
       
  • Humidity-Responsive ON/OFF Switching of Gas Inclusion by Using Cooperative
           Opening/Closing of Heterogeneous Crystalline Cavities in a Peptide NiII
           Macrocycle
    • Authors: Ryosuke Miyake; Chika Kuwata, Manami Ueno, Teppei Yamada
      Pages: 793 - 797
      Abstract: Humidity-responsive ON/OFF switching of CO2 inclusion, associated with cooperative structural changes of heterogeneous cavities in crystalline peptide NiII macrocycles, 1⋅NO3, is demonstrated. The structural transformation between an “open form” and a “closed form” was caused by reversible water uptake into one of the cavities. The adsorption behavior of CO2 was studied with and without water vapor, combined with gas-composition analysis by using gas chromatography. The studies revealed that the open form of 1⋅NO3 adsorbs CO2 gas up to 34 g mol−1, whereas the closed form adsorbs only a negligible amount of CO2 gas. Also, structural studies (X-ray and IR spectroscopies) and investigation of water-content dependence of CO2 adsorption revealed that the switching of gas inclusion occurred abruptly over a narrow range of water-vapor pressure and was caused by the cooperative opening of vacant space to give the open form due to the structural transformation by water uptake.Let's cooperate! Humidity-responsive ON/OFF switching of CO2 inclusion by using cooperative structural changes of heterogeneous cavities in crystalline peptide NiII macrocycles is demonstrated. The opening/closing of vacant cavities triggered by water uptake/release into the other cavities caused the switching of CO2 inclusion (see scheme).
      PubDate: 2017-12-15T04:47:19.008587-05:
      DOI: 10.1002/chem.201704809
       
  • Lipid-DNAs as Solubilizers of mTHPC
    • Authors: Yun Liu; Jan Willem de Vries, Qing Liu, Alwin M. Hartman, Gerhard D. Wieland, Sebastian Wieczorek, Hans G. Börner, Arno Wiehe, Eric Buhler, Marc C. A. Stuart, Wesley R. Browne, Andreas Herrmann, Anna K. H. Hirsch
      Pages: 798 - 802
      Abstract: Hydrophobic drug candidates require innovative formulation agents. We designed and synthesized lipid-DNA polymers containing varying numbers of hydrophobic alkyl chains. The hydrophobicity of these amphiphiles is easily tunable by introducing a defined number of alkyl chain-modified nucleotides during standard solid-phase synthesis of DNA using an automated DNA synthesizer. We observed that the resulting self-assembled micelles solubilize the poorly water-soluble drug, meta-tetra-hydroxyphenyl-chlorin (mTHPC) used in photodynamic therapy (PDT) with high loading concentrations and loading capacities. A cell viability study showed that mTHPC-loaded micelles exhibit good biocompatibility without irradiation, and high PDT efficacy upon irradiation. Lipid-DNAs provide a novel class of drug-delivery vehicle, and hybridization of DNA offers a potentially facile route for further functionalization of the drug-delivery system with, for instance, targeting or imaging moieties.Lipid-DNA micellar drug-delivery systems: Lipid-DNA amphiphiles bearing different numbers of hyrophobic alkyl chains are prepared by using standard solid-phase synthesis. Their self-assembled micelles efficiently render the hydrophobic drug, meta-tetra-hydroxyphenyl-chlorin (mTHPC) for photodynamic therapy (PDT) water-soluble with high loading capacities, good biocompatibility and stability without irradiation and a high PDT efficacy upon irradiation in various cell lines.
      PubDate: 2017-12-18T07:16:59.67581-05:0
      DOI: 10.1002/chem.201705206
       
  • Synthesis of New Microporous Zincosilicates with CHA Zeolite Topology as
           Efficient Platforms for Ion-Exchange of Divalent Cations
    • Authors: Natsume Koike; Kenta Iyoki, Sye Hoe Keoh, Watcharop Chaikittisilp, Tatsuya Okubo
      Pages: 808 - 812
      Abstract: There is growing interest to develop zeolite materials capable of stabilizing divalent cations such as Cu2+, Fe2+, and Ni2+ for catalytic applications. Herein the synthesis of a new microporous zincosilicate with CHA zeolite topology is reported for the first time, by particularly focusing on the mixing procedures of the raw materials to prevent the precipitation of zinc oxides/hydroxides and the formation of impurity phases. The obtained zincosilicate CHA products possess remarkably higher ion-exchange ability for catalytically useful, divalent cations, demonstrated here using Ni2+ as an example, compared to that of aluminosilicate and zincoaluminosilicate analogs. It is anticipated that these zincosilicate CHA materials can be an efficient platform for several important catalytic reactions. In addition, the present finding would provide a general guideline for effective substitution of other heteroatoms into the zeolite frameworks.Catching Two Charges: Microporous zincosilicates with CHA topology are synthesized for the first time, with a particular focus on the mixing procedures of the raw materials. The resulting zincosilicate materials show remarkably high ion-exchange ability for divalent cations, compared to their aluminosilicate and zincoaluminosilicate analogs.
      PubDate: 2017-12-21T10:55:42.052913-05:
      DOI: 10.1002/chem.201705277
       
  • Photo-responsive Bioactive Surfaces Based on Cucurbit[8]uril-Mediated
           Host–Guest Interactions of Arylazopyrazoles
    • Authors: Maike Wiemann; Rebecca Niebuhr, Alberto Juan, Emanuela Cavatorta, Bart Jan Ravoo, Pascal Jonkheijm
      Pages: 813 - 817
      Abstract: A photoswitchable arylazopyrazole (AAP) derivative binds with cucurbit[8]uril (CB[8]) and methylviologen (MV2+) to form a 1:1:1 heteroternary host–guest complex with a binding constant of Ka=2×103 m−1. The excellent photoswitching properties of AAP are preserved in the inclusion complex. Irradiation with light of a wavelength of 365 and 520 nm leads to quantitative E- to Z- isomerization and vice versa, respectively. Formation of the Z-isomer leads to dissociation of the complex as evidenced using 1H NMR spectroscopy. AAP derivatives are then used to immobilize bioactive molecules and photorelease them on demand. When Arg-Gly-Asp-AAP (AAP–RGD) peptides are attached to surface bound CB[8]/MV2+ complexes, cells adhere and can be released upon irradiation. The heteroternary host–guest system offers highly reversible binding properties due to efficient photoswitching and these properties are attractive for designing smart surfaces.Novel photo-responsive CB[8]-mediated complexes to direct cell adhesion: Arylazopyrazoles form moderately stable, light-responsive ternary complexes with CB[8] and methyl viologen. The heteroternary complex can be used for the photo-controlled release of cells.
      PubDate: 2017-12-28T07:00:40.135737-05:
      DOI: 10.1002/chem.201705426
       
  • Lithium-Catalyzed Thiol Alkylation with Tertiary and Secondary Alcohols:
           Synthesis of 3-Sulfanyl-Oxetanes as Bioisosteres
    • Authors: Rosemary A. Croft; James J. Mousseau, Chulho Choi, James A. Bull
      Pages: 818 - 821
      Abstract: 3-Sulfanyl-oxetanes are presented as promising novel bioisosteric replacements for thioesters or benzyl sulfides. From oxetan-3-ols, a mild and inexpensive Li catalyst enables chemoselective C−OH activation and thiol alkylation. Oxetane sulfides are formed from various thiols providing novel motifs in new chemical space and specifically as bioisosteres for thioesters due to their similar shape and electronic properties. Under the same conditions, various π-activated secondary and tertiary alcohols are also successful. Derivatization of the oxetane sulfide linker provides further novel oxetane classes and building blocks. Comparisons of key physicochemical properties of the oxetane compounds to selected carbonyl and methylene analogues indicate that these motifs are suitable for incorporation into drug discovery efforts.Oxetane sulfides as bioisosteres: New classes of sulfur-functionalized oxetanes as promising bioisosteres have been prepared through a chemoselective thiol alkylation with oxetan-3-ols. Use of an inexpensive Li catalyst delivers 3-sulfanyloxetanes in high yields without a competing oxetane ring opening. Comparison of key physicochemical parameters confirms these structures as suitable for medicinal chemistry applications.
      PubDate: 2017-12-20T04:36:00.238331-05:
      DOI: 10.1002/chem.201705576
       
  • Synthesis, Structure, and Acidity Constants of Ligated α-Boryl Acetic
           Acids
    • Authors: Thomas H. Allen; Anthony R. Horner, Steven J. Geib, Stephen G. Weber, Dennis P. Curran
      Pages: 822 - 825
      Abstract: Basic hydrolyses of various ligated α-boryl acetic acid esters provided the first ligated derivatives of the unknown compound boroacetic acid (BH2CH2CO2H). Four monoacids (L-BH2CH2CO2H) and one diacid (L-BH(CH2CO2H)2) were prepared with N-heterocyclic carbene, amine, and pyridine ligands (L). The stable acids were characterized by X-ray crystallography and acidity constant (pKa) measurements. They rank among the least acidic of all known carboxylic acids. In turn, their conjugate bases are among the strongest of all carboxylates.Acids that aren't (so) acidic: The first ligated derivatives of the unknown compound boroacetic acid (BH2CH2CO2H) are described. Four monoacids (L-BH2CH2CO2H) and one diacid (L-BH(CH2CO2H)2) were prepared with N-heterocyclic carbene, amine, and pyridine ligands (L). They rank among the least acidic of all known carboxylic acids (see scheme).
      PubDate: 2017-12-27T10:17:03.031953-05:
      DOI: 10.1002/chem.201705754
       
  • Reduction of Carbonyl Groups by Uranium(III) and Formation of a Stable
           Amide Radical Anion
    • Authors: Kimberly C. Mullane; Thibault Cheisson, Eiko Nakamaru-Ogiso, Brian C. Manor, Patrick J. Carroll, Eric J. Schelter
      Pages: 826 - 837
      Abstract: Methyl benzoate, N,N-dimethylbenzamide, and benzophenone were reduced by UIII[N(SiMe3)2]3 resulting in uranium(IV) products. Reduction of benzophenone lead to UIV[OC⋅Ph2)][N(SiMe3)2]3, (1.1) which forms the dinuclear complex, [N(SiMe3)2]3UIV(OCPhPh-CPh2O)UIV[N(SiMe3)2]3 (1.2), through coupling of the ketyl radical species upon crystallization. Reaction of N,N-dimethylbenzamide with UIII[N(SiMe3)2]3 resulted in UIV[OC⋅(Ph)(NMe2)][N(SiMe3)2]3 (2), a uranium(IV) compound and the first example of a charge-separated amide radical. In the case of methyl benzoate, the reduction resulted in UIV(OMe)[N(SiMe3)2]3 (3) and benzaldehyde as the reduced organic fragment. Compound 2 showed the ability to act as a uranium(III) synthon in its reactivity with trimethylsilyl azide, a reaction that yielded UV(=NSiMe3)[N(SiMe3)2]3. Additionally, 2 was reduced with potassium graphite resulting in [U(μ-O)[O=C(NMe2)(Ph)][N(SiMe3)2]2]2 (4), a dinuclear uranium compound bridged by oxo ligands. Reduction of 2 in the presence of 15-crown-5 afforded isolation of the mono-oxo compound, [(15-crown-5)2K][UO[N(SiMe3)2]3] (5). The results expand the reduction capabilities of UIII complexes and demonstrate a strategy for isolating novel metal-stabilized radicals.U what' Methyl benzoate, N,N-dimethylbenzamide, and benzophenone were reduced by UIII[N(SiMe3)2]3 resulting in uranium(IV) products. The results expand the reduction capabilities of UIII complexes and demonstrate a strategy for isolating novel metal-stabilized radicals.
      PubDate: 2017-12-06T07:56:37.23509-05:0
      DOI: 10.1002/chem.201703396
       
  • Quantitative Analysis of the Self-Assembly Process of Hexagonal PtII
           Macrocyclic Complexes: Effect of the Solvent and the Components
    • Authors: Ayako Baba; Tatsuo Kojima, Shuichi Hiraoka
      Pages: 838 - 847
      Abstract: The self-assembly process of three PtII-linked hexagonal macrocycles consisting of dinuclear PtII complexes and organic ditopic ligands was investigated in polar and less polar solvents by a recently developed approach: quantitative analysis of the self-assembly process (QASAP). In polar CD3NO2, for all the three macrocycles, an ML2 complex was the dominant intermediate during self-assembly, as a result of high positive allosteric cooperativity for the ligand exchange on the PtII centers of the dinuclear PtII complexes. On the other hand, in less polar CD2Cl2, the self-assembly process was affected by the components. For two of the three macrocycles, the chainlike oligomers that contain fewer metals and ligands than the corresponding macrocycles grew with time and the type of the chainlike intermediates formed correlated with the allostericity of the two binding sites in the organic ditopic ligands. In every case, no long oligomers containing more components than the macrocycles themselves were produced during the self-assembly even though free rotation around single bonds in the chainlike oligomers allows them to adopt various conformations that do not facilitate the cyclization. This result suggests that electrostatic and/or steric factors besides rigidity of the components make the cyclization advantageous not only thermodynamically but also kinetically.To cyclize or not to cyclize' That is the question: The self-assembly process of PtII-linked macrocycles was affected by the cooperativity of the two biding sites in the components and the polarity of solvent. In polar solvent, a small fragment, ML2, is the dominant intermediate, whereas in less polar solvent, the growth of chainlike intermediates containing fewer components than the macrocycle was observed. The type of chainlike intermediates is dependent on the cooperativity of the two binding sites in the ditopic ligand.
      PubDate: 2017-11-07T05:18:01.438763-05:
      DOI: 10.1002/chem.201702955
       
  • A One-Step Germole to Silole Transformation and a Stable Isomer of a
           Disilabenzene
    • Authors: Crispin R. W. Reinhold; Zhaowen Dong, Jan M. Winkler, Henning Steinert, Marc Schmidtmann, Thomas Müller
      Pages: 848 - 854
      Abstract: An unusual germole-to-silole transformation is described. As key intermediates hetero-fulvenes are formed which rearrange to more stable bicyclic carbene analogues. The so-formed germylenes undergo a reductive elimination yielding elemental germanium and siloles. In contrast, the analogous silylenes are stable at ambient conditions and were identified by MS spectrometry and NMR spectroscopy supported by the results of quantum mechanical calculations. These bicyclic silylenes are stable derivatives of the global minimum of the C4Si2H6 potential energy surface.Always expect the unexpected: An unprecedented germole to silole transformation opened the way for the synthesis of novel bicyclic silylenes that are stable derivatives of the global minimum on the C4Si2H6 potential energy surface.
      PubDate: 2017-10-20T04:35:34.80845-05:0
      DOI: 10.1002/chem.201703955
       
  • Direct Arylation of Dipyrrolonaphthyridinediones Leads to Red-Emitting
           Dyes with Conformational Freedom
    • Authors: Bartłomiej Sadowski; Michał F. Rode, Daniel T. Gryko
      Pages: 855 - 864
      Abstract: A series of bis-aryl dipyrrolonaphthyridinediones (DPNDs) with various substitution patterns have been designed and synthesized by direct arylation. This reaction occurs regioselectively at positions 3 and 9, which gives a straightforward entry to unique dyes that absorb in the red/far-red region and emit in the far-red/NIR region. The photophysical properties (absorption and fluorescence wavelength) can be controlled by altering the steric hindrance and electronic character of the peripheral aryl group. The fluorescence quantum yields are moderate in the majority of cases and almost independent of changes in the solvent polarity. DPNDs bearing substituents at the ortho position that prevent free rotation of the phenyl ring emit stronger fluorescence relative to the unhindered para analogues and, at the same time their absorption and emission bands are blueshifted. We have used computational methods to explain why electron-donating substituents have significantly stronger effects than electron-withdrawing substituents on the optical properties by invoking the electron-accepting character of the DPND. Electrochemical measurements revealed that the HOMO and LUMO, as well as the electrochemical band gap, also depend strongly on the electronic character of the peripheral group.Z-Shaped, π-expanded chromophores with a dipyrrolonaphthyridinedione core can be obtained by direct arylation. Despite having significant dihedral angles, the groups located on the aryl substituents have a profound effect on the optoelectronic properties of newly obtained dyes (see figure), which is revealed both experimentally and by computational studies.
      PubDate: 2017-11-14T03:05:54.46502-05:0
      DOI: 10.1002/chem.201702306
       
  • An Uncommon Carboxyl-Decorated Metal–Organic Framework with Selective
           Gas Adsorption and Catalytic Conversion of CO2
    • Authors: Yong-Zhi Li; Hai-Hua Wang, Hong-Yun Yang, Lei Hou, Yao-Yu Wang, Zhonghua Zhu
      Pages: 865 - 871
      Abstract: A new three-dimensional (3D) framework, [Ni(btzip)(H2btzip)]⋅2 DMF⋅2 H2O (1) (H2btzip=4,6-bis(triazol-1-yl)isophthalic acid) as an acidic heterogeneous catalyst was constructed by the reaction of nickel wire and a triazolyl-carboxyl linker. Framework 1 possesses intersected 2D channels decorated by free COOH groups and uncoordinated triazolyl N atoms, leading to not only high CO2 and C2H6 adsorption capacity but also significant selective capture for CO2 and C2H6 over CH4 and CO in 273–333 K. Moreover, 1 reveals chemical stability toward water. Grand Canonical Monte Carlo simulations confirmed the multiple CO2- and C2H6-philic sites. As a result of the presence of accessible Brønsted acidic COOH groups in the channels, the activated framework demonstrates highly efficient catalytic activity in the cycloaddition reaction of CO2 with propylene oxide/4-chloromethyl-1,3-dioxolan-2-one/3-butoxy-1,2-epoxypropane into cyclic carbonates.Through employing a triazolyl-carboxyl linker, a stable porous Ni metal–organic framework (MOF) was constructed, which contains free carboxyl groups in channels and reveals not only high CO2 and C2H6 loadings but also significant selective capture for CO2 and C2H6 over CH4 and CO, as well as highly efficient catalytic activity in the cycloaddition reaction of CO2 with epoxides. The multi-point framework–CO2/C2H6 interactions were confirmed by Grand Canonical Monte Carlo simulations (see scheme).
      PubDate: 2017-12-13T08:10:32.86788-05:0
      DOI: 10.1002/chem.201704027
       
  • Achieving Amphibious Superprotonic Conductivity in a CuI Metal–Organic
           Framework by Strategic Pyrazinium Salt Impregnation
    • Authors: Sajal Khatua; Arun Kumar Bar, Javeed Ahmad Sheikh, Abraham Clearfield, Sanjit Konar
      Pages: 872 - 880
      Abstract: Treatment of a pyrazine (pz)-impregnated CuI metal–organic framework (MOF) ([1⊃pz]) with HCl vapor renders an interstitial pyrazinium chloride salt-hybridized MOF ([1⊃pz⋅6 HCl]) that exhibits proton conductivity over 10−2 S cm−1 both in anhydrous and under humid conditions. Framework [1⊃pz⋅6 HCl] features the highest anhydrous proton conductivity among the lesser-known examples of MOF-based materials exhibiting proton conductivity under both anhydrous and humid conditions. Moreover, [1⊃pz] and corresponding pyrazinium sulfate- and pyrazinium phosphate-hybridized MOFs also exhibit superprotonic conductivity over 10−2 S cm−1 under humid conditions. The impregnated pyrazinium ions play a crucial role in protonic conductivity, which occurs through a Grotthuss mechanism.Strategic single crystal to single crystal (SC–SC) transformation of a porous CuI metal–organic framework (MOF) resulted in a pyrazinium salt-impregnated hybridized MOF featuring the first example of superprotonic conductivity both in anhydrous and under humid conditions.
      PubDate: 2017-12-13T07:41:52.121692-05:
      DOI: 10.1002/chem.201704088
       
  • Electron-Proton Transfer Mechanism of Excited-State Hydrogen Transfer in
           Phenol-(NH3)n (n=3 and 5)
    • Authors: Mitsuhiko Miyazaki; Ryuhei Ohara, Claude Dedonder, Christophe Jouvet, Masaaki Fujii
      Pages: 881 - 890
      Abstract: Excited-state hydrogen transfer (ESHT) is responsible for various photochemical processes of aromatics, including photoprotection of nuclear basis. Its mechanism is explained by internal conversion from the aromatic ππ* to πσ* states via conical intersection. This means that the electron is transferred to a diffuse Rydberg-like σ* orbital apart from proton migration. This picture means the electron and the proton do not move together and the dynamics are different in principle. Here, we have applied picosecond time-resolved near-infrared (NIR) and infrared (IR) spectroscopy to the phenol-(NH3)5 cluster, the benchmark system of ESHT, and monitored the electron transfer and proton motion independently. The electron transfer monitored by the NIR transition rises within 3 ps, while the overall H transfer detected by the IR absorption of NH vibration appears with a lifetime of about 20 ps. This clearly proves that the electron motion and proton migration are decoupled. Such a difference of the time-evolutions between the NIR absorption and the IR transition has not been detected in a cluster with three ammonia molecules. We will report our full observation together with theoretical calculations of the potential energy surfaces of the ππ* and πσ* states, and will discuss the ESHT mechanism and its cluster size-dependence between n=3 and 5. It is suggested that the presence and absence of a barrier in the proton transfer coordinate cause the different dynamics.Going different ways: Time-resolved NIR and IR spectroscopy coupled with ab initio calculations on solvated clusters of phenol by ammonia established that the initial ultrafast delocalization of an electron over the solvents by photoexcitation next eliminates the proton from phenol to retrieve the hydrogen atom in the solvents moiety (see graphic). The results support the conclusion that decoupling of the electron and proton of a hydrogen atom occurs in the excited state hydrogen transfer (ESHT).
      PubDate: 2017-12-13T04:41:24.219676-05:
      DOI: 10.1002/chem.201704129
       
  • Well-Defined Chiral Copper NHC Complex in the Asymmetric Conjugated
           β-Borylation and One-Pot Metathesis-Asymmetric β-Borylation Reactions
    • Authors: Anupam Jana; Damian Trzybiński, Krzysztof Woźniak, Karol Grela
      Pages: 891 - 897
      Abstract: Highly stereoselective conjugate β-borylation, using a new chiral NHC-based copper catalyst, has been achieved. The chiral NHC copper complex was prepared in gram scale and showed high enantioselectivity and activity (up to 10 000 turnovers at 100 ppm of catalyst loading). This method was employed in the synthesis of a chiral β-borylated ester from simple unconjugated alkenes though an unprecedented one-pot cross metathesis-asymmetric borylation sequence.Proper copper: Gram scale synthesis of a new chiral copper complex is described. This NHC-copper complex showed excellent activity (up to 1000 TON) and was stereoselective towards conjugate β-borylation. Unprecedented one-pot cross metathesis-asymmetric borylation is also demonstrated.
      PubDate: 2017-12-12T04:11:52.728006-05:
      DOI: 10.1002/chem.201704335
       
  • Controlled Pyrolysis of Ni-MOF-74 as a Promising Precursor for the
           Creation of Highly Active Ni Nanocatalysts in Size-Selective Hydrogenation
           
    • Authors: Kazuki Nakatsuka; Takeharu Yoshii, Yasutaka Kuwahara, Kohsuke Mori, Hiromi Yamashita
      Pages: 898 - 905
      Abstract: Metal organic frameworks (MOFs) are a class of porous organic-inorganic crystalline materials that have attracted much attention as H2 storage devices and catalytic supports. In this paper, the synthesis of highly-dispersed Ni nanoparticles (NPs) for the hydrogenation of olefins was achieved by employing Ni-MOF-74 as a precursor. Investigations of the structural transformation of Ni species derived from Ni-MOF-74 during heat treatment were conducted. The transformation was monitored in detail by a combination of XRD, in situ XAFS, and XPS measurements. Ni NPs prepared from Ni-MOF-74 were easily reduced by the generation of reducing gases accompanied by the decomposition of Ni-MOF-74 structures during heat treatment at over 300 °C under N2 flow. Ni-MOF-74-300 exhibited the highest activity for the hydrogenation of 1-octene due to efficient suppression of excess agglomerated Ni species during heat treatment. Moreover, Ni-MOF-74-300 showed not only high activity for the hydrogenation of olefins but also high size-selectivity because of the selective formation of Ni NPs covered by MOFs and the MOF-derived carbonaceous layer.The knights who say Ni: Ni-MOF-74 heat-treated at 300 °C showed high activity and size-selectivity, due to selective formation of Ni NPs covered by MOFs and a MOF-derived carbonaceous layer.
      PubDate: 2017-12-12T08:01:39.122351-05:
      DOI: 10.1002/chem.201704341
       
  • Photophysical and Photoacoustic Properties of Quadrupolar Borondifluoride
           Curcuminoid Dyes
    • Authors: Stephanie Bellinger; Maryam Hatamimoslehabadi, Seema Bag, Farha Mithila, Jeffrey La, Mathieu Frenette, Samir Laoui, David J. Szalda, Chandra Yelleswarapu, Jonathan Rochford
      Pages: 906 - 917
      Abstract: The synthesis and characterization of a series of donor-π-acceptor-π-donor (D-A-D) curcuminoid molecules is presented herein that incorporates π-extended aryl and electron-donating amino terminal functionalization. Computational evaluation shows these molecules possess quadrupolar character with the lowest energy transitions displaying high molar extinction coefficients with broad tunability through manipulation of terminal donating groups. Consistent with their quadrupolar nature, these molecules show varying degrees of solvatochromic behavior in both their absorption and emission spectra, which has been analyzed by Lippert–Mataga and Kamlet–Taft analysis. Photophysical and photoacoustic (PA) properties of these molecules have been investigated by the optical photoacoustic z-scan (OPAZ) method. Selected curcuminoid molecules display nonlinear behavior at a high laser fluence through excited state absorption that translates to the production of an enhanced photoacoustic emission. A relative comparison of “molar PA emission” is also presented with the crystal violet linear optical absorbing/linear PA emitting system being utilized as a standard reference material for OPAZ experiments. Furthermore, PA tomography experiments are presented to illustrate the enhanced PA contrast obtainable via an excited state absorption.A series of donor-π-acceptor-π-donor (D-A-D) curcuminoid molecules is presented that incorporates π-extended aryl and electron-donating amino terminal functionalization.
      PubDate: 2017-12-14T04:16:28.963774-05:
      DOI: 10.1002/chem.201704423
       
  • Synthesis, Characterisation and Reactions of Truly Cationic
           NiI–Phosphine Complexes
    • Authors: Miriam Mareen Schwab; Daniel Himmel, Sylwia Kacprzak, Valentin Radtke, Daniel Kratzert, Philippe Weis, Melanie Wernet, Andreas Peter, Zeinab Yassine, Dominik Schmitz, Ernst-Wilhelm Scheidt, Wolfgang Scherer, Stefan Weber, Wolfram Feuerstein, Frank Breher, Alexander Higelin, Ingo Krossing
      Pages: 918 - 927
      Abstract: The recently published purely metallo-organic NiI salt [Ni(cod)2][Al(ORF)4] (1, cod=1,5-cyclooctadiene, RF=C(CF3)3) provides a starting point for a new synthesis strategy leading to NiI phosphine complexes, replacing cod ligands by phosphines. Clearly visible colour changes indicate reactions within minutes, while quantum chemical calculations (PBE0-D3(BJ)/def2-TZVPP) approve exergonic reaction enthalpies in all performed ligand exchange reactions. Hence, [Ni(dppp)2][Al(ORF)4] (2, dppp=1,3-bis(diphenylphosphino)propane), [Ni(dppe)2][Al(ORF)4] (3, dppe=1,3-bis(diphenyl-phosphino)ethane), three-coordinate [Ni(PPh3)3][Al(ORF)4] (4) and a remarkable two-coordinate NiI phosphine complex [Ni(PtBu3)2][Al(ORF)4] (5) were characterised by single crystal X-ray structure analysis. EPR studies were performed, confirming a nickel d9-configuration in complexes 2, 4 and 5. This result is supported by additional magnetization measurements of 4 and 5. Further investigations by cyclic voltammetry indicate relatively high oxidation potentials for these NiI compounds between 0.7 and 1.7 V versus Fc/Fc+. Screening reactions with O2 and CO gave first insights on the reaction behaviour of the NiI phosphine complexes towards small molecules with formation of mixed phosphine-CO-NiI complexes and oxidation processes yielding new NiI and/or NiII derivatives. Moreover, 4 reacted with CH2Cl2 at RT to give a dimeric NiII ylide complex (4 c). As CH2Cl2 is a rather stable alkyl halide with relatively high C−Cl bond energies, 4 appears to be a suitable reagent for more general C−Cl bond activation reactions.Looking for NiI complexes…' A facile route to cationic NiI phosphine complexes starting from recently reported [Ni(cod)2][Al(ORF)4] (1, with RF=C(CF3)3) is described. [Ni(dppp)2][Al(ORF)4] (2), [Ni(dppe)2][Al(ORF)4] (3), three-coordinate [Ni(PPh3)3][Al(ORF)4] (4) and a remarkable two-coordinate NiI phosphine complex [Ni(PtBu3)2][Al(ORF)4] (5) were investigated.
      PubDate: 2017-12-13T08:00:50.991638-05:
      DOI: 10.1002/chem.201704436
       
  • One-Step Synthesis of B/N Co-doped Graphene as Highly Efficient
           Electrocatalyst for the Oxygen Reduction Reaction: Synergistic Effect of
           Impurities
    • Authors: Vlastimil Mazánek; Stanislava Matějková, David Sedmidubský, Martin Pumera, Zdeněk Sofer
      Pages: 928 - 936
      Abstract: In the last decade, numerous studies of graphene doping by various metal and nonmetal elements have been done in order to obtain tailored properties, such as non-zero band gap, electrocatalytic activity, or controlled optical properties. From nonmetal elements, boron and nitrogen were the most studied dopants. Recently, it has been shown that in some cases the enhanced electrocatalytic activity of graphene and its derivatives can be attributed to metal impurities rather than to nonmetal elements. In this paper, we investigated the electrocatalytical properties of B/N co-doped graphene with respect to the content of metallic impurities introduced by the synthesis procedures. For this purpose, a permanganate (Hummers) and a chlorate (Hofmann) route were used for the preparation of the starting graphene oxides (GO). The GO used for the synthesis of B/N co-doped graphene had significantly difference compositions of oxygen functionalities as well as metallic impurities introduced by the different synthetic procedures. We performed a detailed structural and chemical analysis of the doped graphene samples to correlate their electrocatalytic activity with the concentration of incorporated boron and nitrogen as well as metallic impurities.Permitted doping: B/N co-doped graphene samples were synthesized by using differently generated graphene oxide and various B/N precursors. The final composition highly depends on both factors. The electrochemical behavior of all samples with respect to the oxygen reduction reaction was also investigated and correlated with the presence of metallic impurities.
      PubDate: 2017-12-13T08:16:15.090009-05:
      DOI: 10.1002/chem.201704515
       
  • Rapid Iododeboronation with and without Gold Catalysis: Application to
           Radiolabelling of Arenes
    • Authors: Stacey Webster; Kerry M. O'Rourke, Conor Fletcher, Sally L. Pimlott, Andrew Sutherland, Ai-Lan Lee
      Pages: 937 - 943
      Abstract: Radiopharmaceuticals that incorporate radioactive iodine in combination with single-photon emission computed tomography imaging play a key role in nuclear medicine, with applications in drug development and disease diagnosis. Despite this importance, there are relatively few general methods for the incorporation of radioiodine into small molecules. This work reports a rapid air- and moisture-stable ipso-iododeboronation procedure that uses NIS in the non-toxic, green solvent dimethyl carbonate. The fast reaction and mild conditions of the gold-catalysed method led to the development of a highly efficient process for the radiolabelling of arenes, which constitutes the first example of an application of homogenous gold catalysis to selective radiosynthesis. This was exemplified by the efficient synthesis of radiolabelled meta-[125I]iodobenzylguanidine, a radiopharmaceutical that is used for the imaging and therapy of human norepinephrine transporter-expressing tumours.To catalyse or not to catalyse: A rapid air- and moisture-stable ipso-iododeboronation procedure using NIS has been developed in the non-toxic, green solvent dimethyl carbonate (see scheme). The procedure was utilised for the rapid and highly efficient gold-catalysed radioiododeboronation of arenes.
      PubDate: 2017-12-14T03:20:36.971067-05:
      DOI: 10.1002/chem.201704534
       
  • 2-(Trimethylsilyl)-λ3-Phosphinine: Synthesis, Coordination Chemistry,
           and Reactivity
    • Authors: Marija H. Habicht; Friedrich Wossidlo, Tobias Bens, Evgeny A. Pidko, Christian Müller
      Pages: 944 - 952
      Abstract: The [4+2] cycloaddition reaction between 2-pyrone and Me3Si−C≡P gives the corresponding 2-(trimethylsilyl)-λ3-phosphinine in good yields as a rather air and moisture stable, colorless oil. Insight into the regioselectivity of the pericyclic reaction was obtained with the help of deuterium-labeling experiments. The silyl-phosphinine acts as a ligand for the preparation of a Cu(I) and the first crystallographically characterized phosphinine-Ag(I) complex. The title compound was further used as a starting material for an alternative preparation of the parent phosphinine C5H5P by means of protodesilylation with HCl. C5H5P reacts with CuBr⋅S(CH3)2 to give an infinite Cu(I)Br coordination polymer. DFT calculations shed light on the influence of the -Si(CH3)3 group on the electronic properties of the aromatic phosphorus heterocycle.Phospha-benzene analogues: 2-(Trimethylsilyl)-λ3-phosphinine can easily be prepared by a [4+2] cycloaddition between 2-pyrone and (CH3)3Si−C≡P. Protodesilylation yields the parent phosphine C5H5P. The coordination chemistry was investigated, and DFT calculations give insight into the electronic properties of the phosphorus heterocycles.
      PubDate: 2017-12-11T04:44:52.222609-05:
      DOI: 10.1002/chem.201704539
       
  • 1,5-Disubstituted 1,2,3-Triazole-Containing Peptidotriazolamers: Design
           Principles for a Class of Versatile Peptidomimetics
    • Authors: Oliver Kracker; Jerzy Góra, Joanna Krzciuk-Gula, Antoine Marion, Beate Neumann, Hans-Georg Stammler, Anke Nieß, Iris Antes, Rafał Latajka, Norbert Sewald
      Pages: 953 - 961
      Abstract: Peptidotriazolamers are hybrid foldamers combining features of peptides and triazolamers—repetitive peptidomimetic structures with triazoles replacing peptide bonds. We report on the synthesis of a new class of peptidomimetics, containing 1,5-disubstituted 1,2,3-triazoles in an alternating fashion with amide bonds and the analysis of their conformation in solid state and solution. Homo- or heterochiral peptidotriazolamers were obtained from enantiomerically pure propargylamines with stereogenic centers in the propargylic position and α-azido esters by ruthenium-catalyzed azide–alkyne cycloaddition (RuAAC) under microwave conditions in high yields. With such building blocks the peptidotriazolamers are readily available by solution phase synthesis. While the conformation of the homochiral peptidotriazolamer Boc-Ala[5Tz]Phe-Val[5Tz]Ala-Leu[5Tz]Val-OBzl resembles that of a β VIa1 turn, the heterochiral peptidotriazolamer Boc-d-Ala[5Tz]Phe-d-Val[5Tz]Ala-d-Leu[5Tz]Val-OBzl adopts a polyproline-like repetitive structure.Stereochemistry matters: While the conformation of the homochiral peptidotriazolamer Boc-Ala[5Tz]Phe-Val[5Tz]Ala-Leu[5Tz]Val-OBzl resembles that of a βVIa1 turn, the heterochiral peptidotriazolamer Boc-d-Ala[5Tz]Phe-d-Val[5Tz]Ala-d-Leu[5Tz]Val-OBzl adopts a polyproline-like repetitive structure.
      PubDate: 2017-12-13T07:56:22.796556-05:
      DOI: 10.1002/chem.201704583
       
  • Mutagenesis of Sequence Determinants of Truncated Porcine ALOX15 Induces
           Changes in the Reaction Specificity by Altering the Catalytic Mechanism of
           Initial Hydrogen Abstraction
    • Authors: Patricia Saura; Ilya Kaganer, Dagmar Heydeck, José M. Lluch, Hartmut Kühn, Àngels González-Lafont
      Pages: 962 - 973
      Abstract: The reaction specificity of lipoxygenases is of physiological relevance since the various oxygenation products exhibit different biological activities. Among mammalian ALOX15 orthologs there are arachidonic acid 12- and 15-lipoxygenating enzymes and recent studies suggested an evolutionary switch in that reaction specificity during late primate development. Previous reports showed that 12-lipoxygenating ALOX15 orthologs can be converted to 15-lipoxygenating enzymes by site-directed mutagenesis of some sequence determinants. Unfortunately, the molecular basis for those alterations are not well understood. Here, the arachidonic acid 12-lipoxygenating N-terminal truncation variant of pig ALOX15, for which a crystal structure is available, was used to explore the catalytic mechanism of the specificity switch induced by mutagenesis of Val418 and Val419 sequence determinants. We found that Val418Ile+Val419Met double mutant is dominantly 15-lipoxygenating. Docking and MD simulations, and quantum mechanics/molecular mechanics calculations indicated that the wildtype energy barrier for arachidonic acid 15-lipoxygenation is 3.4 kcal mol−1 higher than for 12-lipoxygenation. In contrast, for the Val418Ile+Val419Met double mutant the energy barrier for 12-lipoxygenation is 6.0 kcal mol−1 higher than for 15-lipoxygenation. Our data suggest that enzyme–substrate complex geometries determine the value of these energy barriers and, as a consequence, the reaction specificity of ALOX15 orthologs.In vitro studies and in silico simulations indicate a strong preference of wildtype pig miniALOX15 for 12-lipoxygenation of arachidonic acid, but selective 15-lipoxygenation for the Val418Ile+Val419Met double mutant. These results provide a suitable explanation for the observed evolutionary switch in ALOX15 specificity, which has taken place during late primate development.
      PubDate: 2017-12-14T03:20:43.28868-05:0
      DOI: 10.1002/chem.201704672
       
  • Three-Component Synthesis and Photophysical Properties of Novel
           Coumarin-Based Merocyanines
    • Authors: Julian Papadopoulos; Kay Merkens, Thomas J. J. Müller
      Pages: 974 - 983
      Abstract: Novel E-configured coumarin-based merocyanines were efficiently synthesized by a one-pot, three-component Sonogashira coupling–Michael addition starting from triflyl coumarins, terminal alkynes and secondary amines. The photophysical properties of the synthesized yellow to orange merocyanines were studied by UV/Vis and fluorescence spectroscopy and rationalized by Hammett–Taft correlations and DFT and TD-DFT calculations. Most compounds were only weakly fluorescent in solution; however, two compounds were investigated in more detail with respect to their aggregation behavior. The system for R2=H and NR23=pyrrolidinyl shows aggregation induced emission at a water content of 40–60 % in methanol, while the chromophore with R2=p-Me2NC6H4 and NR23=morpholinyl displays considerable aggregation induced emission enhancement with a concomitant redshift at increasing water contents in THF.Coloring in sequence: A Sonogashira coupling–Michael addition sequence furnishes coumaryl merocyanines in moderate to excellent yield in a consecutive three-component fashion. Besides tunable electronic properties (UV/Vis and fluorescence spectroscopy, and TD-DFT calculations) selected chromophores display aggregation induced emission (enhancement).
      PubDate: 2017-12-13T04:35:57.443208-05:
      DOI: 10.1002/chem.201704912
       
  • Protein Recognition by Functionalized Sulfonatocalix[4]arenes
    • Authors: Aishling M. Doolan; Martin L. Rennie, Peter B. Crowley
      Pages: 984 - 991
      Abstract: The interactions of two mono-functionalized sulfonatocalix[4]arenes with cytochrome c were investigated by structural and thermodynamic methods. The replacement of a single sulfonate with either a bromo or a phenyl substituent resulted in altered recognition of cytochrome c as evidenced by X-ray crystallography. The bromo-substituted ligand yielded a new binding mode in which a self-encapsulated calixarene dimer contributed to crystal packing. This ligand also formed a weak halogen bond with the protein. The phenyl-substituted ligand was bound to Lys4 of cytochrome c, in a 1.7 Å resolution crystal structure. A dimeric packing arrangement mediated by ligand–ligand contacts in the crystal suggested a possible assembly mechanism. The different protein recognition properties of these calixarenes are discussed.Calixarene capped cytochrome c: Altered binding sites and assemblies with mono-functionalized sulfonatocalix[4]arenes reveal altered binding sites and assemblies. The different protein recognition properties of these calixarenes are discussed.
      PubDate: 2017-12-13T08:25:47.855922-05:
      DOI: 10.1002/chem.201704931
       
  • Macrocyclic Triruthenium Complexes Having Electronically Coupled
           Mixed-Valent States
    • Authors: Daniel Fink; Michael Bodensteiner, Michael Linseis, Rainer F. Winter
      Pages: 992 - 996
      Abstract: 5-Ethynyl-2-furancarboxylic acid and 3-ethynylbenzoic acid self-assemble with [HRu(CO)Cl(PiPr3)2] to form macrocyclic C3-symmetric triangular triruthenium alkenyl complexes [{Ru(CO)(PiPr3)2(CH=CHArCOO)}3] (Ar=C6H4: 1-B, Ar=C4H2O: 1-F), which were characterized by multinuclear NMR spectroscopy, high-resolution ESI mass spectrometry, and, in the case of 1-B, by X-ray crystallography. Electrochemical studies indicate that the macrocycles are oxidized in three consecutive one-electron steps. The mixed-valent states obtained by electrochemical or chemical oxidation show signs of valence delocalization, which makes these complexes rare examples of molecule-based conductive loops with through-bond charge delocalization.Merry-go-round: Macrocyclic triruthenium complexes formed from 3-ethynyl benzoic acid or 5-ethynylfuran-2-carboxylic acid and the hydride complex [HRu(CO)Cl(PiPr3)2] are oxidized in three individually resolved one-electron steps (see figure). Their associated mixed-valent radical cations and dications show clear signs of through-bond charge delocalization, which makes these macrocycles conductive loops.
      PubDate: 2017-12-13T08:25:38.163481-05:
      DOI: 10.1002/chem.201705143
       
 
 
JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
 
Home (Search)
Subjects A-Z
Publishers A-Z
Customise
APIs
Your IP address: 54.226.179.247
 
About JournalTOCs
API
Help
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2016