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  Subjects -> CHEMISTRY (Total: 845 journals)
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    - CHEMISTRY (595 journals)
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CHEMISTRY (595 journals)                  1 2 3 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 8)
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: 34)
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: 246)
ACS Photonics     Full-text available via subscription   (Followers: 11)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 21)
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 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: 56)
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: 17)
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)
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: 67)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 14)
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: 40)
Angewandte Chemie     Hybrid Journal   (Followers: 199)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 218)
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: 15)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
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: 310)
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: 118)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 91)
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: 4)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 66)
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: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 14)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 72)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 24)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 20)
Chemical Reviews     Full-text available via subscription   (Followers: 181)
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: 58)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 26)
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: 44)
Chemistry of Materials     Full-text available via subscription   (Followers: 255)
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: 15)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 9)
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: 7)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 18)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 2)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 3)
Copernican Letters     Open Access   (Followers: 1)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
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: 17)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 61)
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  
Elements     Full-text available via subscription   (Followers: 3)
Environmental Chemistry     Hybrid Journal   (Followers: 7)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 4)
Environmental Science & Technology Letters     Full-text available via subscription   (Followers: 5)

        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  [1579 journals]
  • Synthesis of Electron-Rich, Planarized Silicon(IV) Species and a
           Theoretical Analysis of Dimerizing Aminosilanes
    • Authors: Nina Kramer; Christoph Jöst, Alexandra Mackenroth, Lutz Greb
      Abstract: Equipping silicon(IV) with electron-rich, geometrically constrained NNN- and ONO-tridentate substituents leads to aminosilanes with increased Lewis acidity—expressed through the formation of Si2N2 rings by head-to-tail dimerization. Depending on the substituents, the dimerization can be controlled for the first time, yielding monomeric, structurally reversible and dimeric states. The monomeric species display substantial distortions from tetrahedral towards planar geometry at silicon. The dimerization and the Lewis acidity of aminosilanes are rationalized by (conceptual) DFT, NBO, ETS-NOCV and QTAIM methods. The preorganization at silicon, London dispersion between the substituents and resonance phenomena inside the formed Si2N2 tetracycles are identified as driving forces for the dimerization. Comparison with selected aminosilanes permits general conclusions to be reached on the Lewis acidity of silicon species and on the aggregation of amphiphilic compounds.Shape up! Geometrically constrained, electron-rich aminosilanes have been synthesized that can impart control over a unique dimerization process (see figure). Quantum theoretical analyses of the process permit general conclusions to be drawn on the Lewis acidity of silicon compounds and on dimerizing amphiphilic species.
      PubDate: 2017-11-17T05:36:24.3076-05:00
      DOI: 10.1002/chem.201703649
  • Solvent Effect on the Photoinduced Structural Change of a Phosphorescent
           Molecular Butterfly
    • Authors: Ying-Zhong Ma; Chenkun Zhou, Benjamin Doughty, Davis C. Easley, Justin Deterding, Biwu Ma
      Abstract: Photoinduced structural changes (PSC) is one of the fundamental excited-state dynamic processes, and yet often very challenging to distinguish from competing electronic excited-state relaxation channels having similar or even comparable timescales. Here, we report a detailed study on the PSC of a pyrazolate bridged platinum(II) binuclear complex, BFPtPZ (C^NPt(μ-pz′)2PtC^N, C^N=2-(2,4-difluorophenyl)pyridine, pz′=pyrazolate), a molecular butterfly, using time-correlated single photon counting measurements at different wavelengths and sample temperatures. Analysis of the results obtained using dichloromethane (DCM) and ethylene carbonate (EC) as solvents enabled us to reveal an unexpected, strong solvent effect on the PSC processes. We show that a rapid PSC process with a characteristic timescale of 323 ps is observed in DCM, which leads to an excitation equilibrium between the ligand center/metal-to-ligand charge transfer (3LC/MLCT) and metal-metal-to-ligand charge transfer (3MMLCT) triplet states. The subsequent relaxation from these electronic states to the ground state takes place in several nanoseconds. In contrast, the corresponding PSC process in EC appears slow at all temperatures studied in our experiments and showed no sign of such excitation equilibrium. The observed solvent effect is found to arise from distinct solvent properties including their viscosities and polarities as well as the peculiar electronic excited-states of the butterfly-like molecules with charge transfer character.A butterfly-like phosphorescent platinum(II) binuclear complex that can undergo a molecular structure change is probed in real time using time-resolved photoluminescence spectroscopy. Analysis of the kinetics acquired at different wavelengths and temperatures enable us to reveal a pronounced solvent effect.
      PubDate: 2017-11-17T05:35:30.564311-05:
      DOI: 10.1002/chem.201703259
  • De Novo Synthesis of α-Hydroxy Ketones by Gallic Acid-Promoted Aerobic
           Coupling of Terminal Alkynes with Diazonium Salts
    • Authors: Benito Alcaide; Pedro Almendros, Israel Fernández, Fernando Herrera, Amparo Luna
      Abstract: An unprecedented metal-free direct preparation of unprotected α-hydroxy ketones from terminal alkynes under mild conditions with diazonium salts as the arene source and without the requirement of irradiation is described. The process is general and fully compatible with a wide variety of substitution in both reactants. Experimental and computational evidence strongly suggest the involvement of radical species in the transformation.Very mild indeed: An organo-promoted preparation of unprotected α-hydroxy ketones from terminal alkynes under mild aerobic conditions with diazonium salts as the arene source and without the requirement of irradiation has been achieved.
      PubDate: 2017-11-17T05:30:40.498176-05:
      DOI: 10.1002/chem.201705106
  • Self-Assembly of Novel Thiophene-Based BODIPY RuII Rectangles: Potential
           Antiproliferative Agents Selective Against Cancer Cells
    • Authors: Gajendra Gupta; Abhishek Das, Sourav Panja, Ji Yeon Ryu, Junseong Lee, Nripendranath Mandal, Chang Yeon Lee
      Abstract: Novel Ru (2+2) rectangles were designed and synthesized by self-assembly of a new thiophene-functionalized dipyridyl BODIPY ligand, BDPS, and ruthenium(II) precursors. The complexes exhibited dose-dependent antiproliferative activities against cancer cells, in which some compounds selectively kill cancer cells. The net fluorescence due to BODIPY allowed us to visualize their location inside cancer cells. Moreover, the metalla-rectangles displayed substantial propensity to bind with biomolecules.A new thiophene-based BODIPY ligand, BDPS, has been designed and utilized to successfully synthesize four new Ru (2+2) rectangles. The presence of thiophene group in these rectangles has significantly improved its biological activities.
      PubDate: 2017-11-17T04:35:51.451143-05:
      DOI: 10.1002/chem.201704368
  • Pd-Catalyzed β-C(sp3)-H Arylation of Propionic Acid and Related
           Aliphatic Acids
    • Authors: Kiron Kumar Ghosh; Manuel van Gemmeren
      Abstract: A generally applicable Pd-catalyzed protocol for the β-C(sp3)-H arylation of propionic acid and related α-branched aliphaticacids is reported. Enabled by the use of N-acetyl-β-alanine as ligandour protocol delivers a broad range of arylation products. Notably, thehighly challenging propionic acid, which lacks any accelerationthrough the Thorpe-Ingold effect, can be employed as substrate withsynthetically useful yields. Furthermore, the scalability and syntheticapplicability of the protocol are demonstrated.
      PubDate: 2017-11-17T04:32:36.174798-05:
      DOI: 10.1002/chem.201705449
  • Ce3+-Sensitized Tm3+/Mn2+-doped NaYF4 Colloidal Nanocrystals: Intense Cool
           White Light from Phosphor coated UV LED
    • Authors: Venkataramanan Mahalingam; Venkata N K B Adusumalli, Heramba V. S. R. M. Koppisetti
      Abstract: Intense white light emission is observed from colloidal single component NaYF4:Ce3+/Tm3+/Mn2+ nanocrystals. This combination is interesting as it uses Mn2+ ions instead of green and red emitting Ln3+ ions which are expensive and less abundant. The single band blue emission of Tm3+ ions was combined with the broadband greenish yellow emission of Mn2+ ions to produce strong white light emission using Ce3+ ions as excitation source. Interestingly, there is hardly any re-absorption of blue emission by Mn2+ ions and the spectrum matches the commercial Ce3+-doped YAG phosphor coated over blue LED. In addition, we have successfully incorporated the colloidal nanocrystals into a polymer matrix to make nanocomposite as well as transparent films without altering the optical properties of the nanocrystals. The colloidal nanocomposite was coated over UV LED to fabricate white LEDs. Finally, when the concentration of the dopant (Mn2+) ions was tuned the correlated color temperature (CCT) values varied between cool white light and daylight region.
      PubDate: 2017-11-17T04:04:08.272828-05:
      DOI: 10.1002/chem.201704156
  • The Investigation on Resorcinarenes towards either Inhibiting or Promoting
           Insulin Fibrillation
    • Authors: Xu Han; Chuan Tian, Ingrid Gandra, Valeria Eslava, Diana Galindres, Edgar Vargas, Roger Leblanc
      Abstract: Different tail enigneered resorcinarenes have been examined towards the insulin fibrillation via experimental and computational studies. The resorcinarene showed a promising effect on the inhibition of insulin fibrillalition via ThT assay, CD spectra, and AFM images. Both ThT assay and computational results indicate the tail from the resorcinarene has an impact on insulin fibrillation by either inhibition or promotion because of the resident position on insulin. These observations have significant biological implications in the design of lead drug molecules as well as the development of potential therapeutic strategies.
      PubDate: 2017-11-16T12:55:20.942796-05:
      DOI: 10.1002/chem.201704932
  • Large Proton Affinity Enhancements Triggered by Non-Covalent Interactions
    • Authors: Carlos Martín-Fernández; M. Merced Montero-Campillo, Ibon Alkorta, Manuel Yáñez, Otilia Mó, José Elguero
      Abstract: The proton affinity of the hydroxyl group of a series of compounds YHxOH (x=0-3, Y = Li, Na, Be, Mg, B, Al, Si, P, S, Cl, H) always increases upon interaction with Lewis bases LB = NH3, H2CNH, HCN, according to electronic structure calculations carried out at the G4 level of theory. The LB:YHxOH complexes experiment proton affinity enhancements from 24.8 to 304.8 kJ·mol-1 on its OH group with respect to the free compounds. This enhancement is related to the ability of these YHxOH compounds, acting as Lewis acids, to form non-covalent interactions of different kinds. Interestingly, weakly interacting systems can give place to proton affinity enhancements equal or even larger than strongly interacting systems, as observed in the halogen bond-containing complex H2CNH···ClOH, the free compound (PA = 624 kJ·mol-1) being transformed into a base (PA = 947.2 kJ·mol-1) stronger than pyridine.
      PubDate: 2017-11-16T11:25:23.317785-05:
      DOI: 10.1002/chem.201705047
  • Rotating iron and titanium sandwich complexes
    • Authors: Filip Vlahovic; Maja Gruden, Marcel Swart
      Abstract: The origin for the rotational barrier of organometallic vsinorganic sandwich complexes has remained enigmatic for the pastdecades. Here, we investigate in detail what causes the substantialbarrier for titanodecaphosphacene through spin-state consistentdensity functional theory. Orbital interactions are shown to be thedetermining factor.
      PubDate: 2017-11-16T09:55:26.258999-05:
      DOI: 10.1002/chem.201704829
  • First Structure of a Designed Minor Groove Binding Heterocyclic Cation
           that Specifically Recognizes Mixed DNA Base Pair Sequences
    • Authors: Narinder K. Harika; Markus W. Germann, W. David Wilson
      Abstract: The high-resolution NMR structure of the first heterocyclic, non-amide, organic cation that strongly and selectively recognizes mixed AT/GC bp (bp=base pair) sequences of DNA in a 1:1 complex is described. Compound designs of this type provide essential methods for control of functional, non-genomic DNA sequences and have broad cell uptake capability, based on studies from animals to humans. The high-resolution structural studies described in this report are essential for understanding the molecular basis for the sequence-specific binding as well as for new ideas for additional compound designs for sequence-specific recognition. The molecular features, in this report, explain the mechanism of recognition of both A⋅T and G⋅C bps and are an interesting molecular recognition story. Examination of the experimental structure and the NMR restrained molecular dynamics model suggests that recognition of the G⋅C base pair involves two specific H-bonds. The structure illustrates a wealth of information on different DNA interactions and illustrates an interfacial water molecule that is a key component of the complex.One dication in the minor groove: The high-resolution NMR structure of the first heterocyclic, non-amide, organic cation that strongly and selectively recognizes mixed AT/GC bp sequences of DNA in a 1:1 complex is described. The structure illustrates a wealth of information on different DNA interactions and illustrates an interfacial water molecule that is a key component of the complex.
      PubDate: 2017-11-16T09:01:41.844574-05:
      DOI: 10.1002/chem.201704563
  • Sulfonylative and Azidosulfonylative Cyclizations by
           Visible-Light-Photosensitization of Sulfonyl Azides in THF
    • Authors: Shaoqun Zhu; Atchutarao Pathigoolla, Grace Lowe, Darren A. Walsh, Mick Cooper, William Lewis, Hon Wai Lam
      Abstract: The generation of sulfonyl radicals from sulfonyl azides using visible light and a photoactive iridium complex in THF is described. This process was used to promote sulfonylative and azidosulfonylative cyclizations of enynes to give several classes of highly functionalized heterocycles. The use of THF as the solvent is critical for successful reactions. The proposed mechanism of radical initiation involves the photosensitized formation of a triplet sulfonyl nitrene, which abstracts a hydrogen atom from THF to give a tetrahydrofuran-2-yl radical, which then reacts with the sulfonyl azide to generate the sulfonyl radical.The generation of sulfonyl radicals from sulfonyl azides using visible light photocatalysis is described. This process was used to promote azidosulfonylative and sulfonylative cyclizations of various enynes to give several classes of highly functionalized heterocycles. The use of THF as the solvent is critical for successful reactions.
      PubDate: 2017-11-16T09:01:18.368967-05:
      DOI: 10.1002/chem.201704380
  • Gold-Doping of Double-Crown Pd Nanoclusters
    • Authors: Jishi Chen; Liren Liu, Xu Liu, Lingwen Liao, Shengli Zhuang, Shiming Zhou, Jinlong Yang, Zhikun Wu
      Abstract: Double-crown Ni, Pd, or Pt nanoclusters have attracted extensive interests due to their aesthetic structure and intriguing properties. However, their doping by other metals remains unknown until now. Herein, Pd4(PET)8 and Pd5(PET)10 (PET: SCH2CH2Ph) were successfully doped with gold and the doped nanoclusters were characterized by using multiple techniques such as mass spectrometry and X-ray crystallography. It is revealed that in the doping not one but two gold atoms replace one Pd with the other double-crown structure essentially unchanged, and the gold-doping results in the blue-shift of the maximum visible absorption, the increase of optical energy gap and the reduction of anti-aromaticity of monometal Pd nanoclusters. Importantly, it is found that Au4Pd2(PET)8 nanocluster bears chirality originating from not only the helixed Au4Pd2S8 framework, but also unanimous R or S configuration of sulfur atoms in the enantiomer. For the latter chirality origin, it was not previously reported or proposed. Au4Pd2(PET)8 reported here also represents the smallest chiral bimetal nanocluster so far to the best of our knowledge. This work advances one step toward both the tailoring of group 10 metal nanoclusters by doping and the understanding of chirality origin for metal nanoclusters.Double-crown Pd4(PET)8 and Pd5(PET)10 were successfully doped with gold through two Au atoms replacing one Pd atom with the other double-crown structure essentially unchanged. Au4Pd2(PET)8 is the smallest chiral bimetal nanoclusters so far and it bears chirality originating from not only the helixed Au4Pd2S8 framework but also unanimous R or S configuration of sulfur atoms in the enantiomer.
      PubDate: 2017-11-16T09:00:28.84115-05:0
      DOI: 10.1002/chem.201704413
  • Characterization of Carbenes via Hydrogenation Energies, Stability, and
           Reactivity: What's in a Name'
    • Authors: Monica Vasiliu; Kirk A. Peterson, Anthony J. Arduengo, David A. Dixon
      Abstract: The hydrogenation energies and singlet–triplet (S–T) splittings at the G3MP2 level of theory have been calculated for a wide range of carbenes. The carbene, :CXY with different substituents (X, Y=H, CN, NC, F, Cl, OH, OCH3, CH3, CF3, SiH3, SiMe3, phenyl, CH=O, PH2, and NH2) at the carbenic carbon center, immidazole-based carbenes, Bertrand's carbenes, and Seppelt's CF3CSF3 were studied. The stable carbenes are singlets with large S–T splittings and with the least exothermic hydrogenation energies. The singlet ground state immidazole-based carbenes are calculated to have the least exothermic hydrogenation energies (−15 to −30 kcal mol−1) and the largest S–T gaps. The singlet ground states of the Bertrand carbenes have more exothermic hydrogenation (ca. −67 kcal mol−1) energies and much smaller S–T gaps. The more exothermic reaction energies arise due to the need to make the phosphorus planar in the carbene so that it can donate into the empty p-orbital at the carbene carbon center. The bending potential at the carbene carbon center in the Bertrand compounds is very flat with a large XC:Y angle. Seppelt's CF3CSF3 appears to be energetically similar to the Bertrand system, probably due to the required adjustments for geometric distortions at the sulfur center.Hydrogenation energies are correlated with singlet–triplet (S–T) splittings at the G3MP2 level for a wide range of carbenes. A stable closed shell singlet nucleophilic carbene should have a large singlet–triplet gap and a valence angle at the carbene center less than an sp2 hybridized carbon (
      PubDate: 2017-11-16T08:42:02.600251-05:
      DOI: 10.1002/chem.201703539
  • Overcoming the Incompatibility Challenge in Chemoenzymatic and
           Multi-Catalytic Cascade Reactions
    • Authors: Sandy Schmidt; Kathrin Castiglione, Robert Kourist
      Abstract: Multi-catalytic cascade reactions bear a great potential to minimize downstream and purification steps, leading to a drastic reduction of the produced waste. In many examples, the compatibility of chemo- and biocatalytic steps could be easily achieved. Problems associated with the incompatibility of the catalysts and their reactions, however, are very frequent. Cascade-like reactions can hardly occur in this way. One possible solution to combine, in principle, incompatible chemo- and biocatalytic reactions is the defined control of the microenvironment by compartmentalization or scaffolding. Current methods for the control of the microenvironment of biocatalysts go far beyond classical enzyme immobilization and are thus believed to be very promising tools to overcome incompatibility issues and to facilitate the synthetic application of cascade reactions. In this Minireview, we will summarize recent synthetic examples of (chemo)enzymatic cascade reactions and outline promising methods for their spatial control either by using bio-derived or synthetic systems.Compartmentalize me! Compartmentalization is nature's successful strategy of controlling the microenvironment of catalysts in a defined way, thereby making the combination of different reactions feasible. This Minireview summarizes recent synthetic examples of (chemo)enzymatic cascade reactions and outlines promising methods for their spatial control either by using bio-derived or synthetic systems.
      PubDate: 2017-11-16T08:41:52.745627-05:
      DOI: 10.1002/chem.201703353
  • Template-Assisted Benzannulation Route to Pentacene and Tetracene
           Derivatives and its Application to Construct Amphiphilic Acenes That
           Self-Assemble into Helical Wires
    • Authors: Bikash Pal; Chun-Hsiung Chang, Cian-Jhe Zeng, Chih-Hsiu Lin
      Abstract: Pentacene is one of the most versatile organic semiconductors. New synthetic strategies to construct the pentacene skeleton are imperative to produce pentacene derivatives with appropriate solubility, stability, and optoelectronic properties for various applications. This paper describes a template-directed approach to pentacene derivatives. In the retrosynthesis, the acene skeleton is viewed as a laddered double strand polyene instead of the more intuitive linearly fused hexagons. Based on this vision, the template strand of polyene is constructed with Wittig olefination, whereas the second strand is accomplished with Knoevenagel condensation to produce pentacene and tetracene derivatives. The synthetic scheme is flexible enough to generate an array of acene derivatives with substitution patterns that were hitherto difficult to access. Amphiphilic pentacene and tetracene derivatives were also synthesized by the template strategy. One pentacene based amphiphilic rod-coil molecule undergoes self-assembly to form helical wire structures that were visualized with TEM.When the acene structure is viewed as a double strand polyene, a synthetic strategy based on template-assisted multiple benzannulation emerges. This efficient and versatile approach enables the synthesis of terminal-ring-substituted pentacene and tetracene derivatives with considerable structure diversity. With this protocol, the authors also revealed an amphiphilic pentacene derivative that self-assembles to form helical nanowires.
      PubDate: 2017-11-16T08:40:51.276333-05:
      DOI: 10.1002/chem.201703084
  • K-Region-Extended [c]-Heteroannulated Pyrenes
    • Authors: Kevin Baumgärtner; Tobias Kirschbaum, Fabian Krutzek, Andreas Dreuw, Frank Rominger, Michael Mastalerz
      Abstract: Extended fused aromatic compounds are promising materials for organic electronics. Among them, structures with five-membered annulated rings differ from those consisting only of six-membered carbocyclic rings. To date, fusion of five-membered rings has been realized mainly via the [b]-edge, and systems fused via the [c]-edge are of low stability. Whereas linearly double [b]-fused systems are stable, analogous [c]-fused systems have not been described to date. Comparable to the stabilization of longer acenes by peri-fusion, herein the synthesis of doubly [c]-annulated systems stabilized by double peri-fusion is described. The compounds were analyzed by X-ray crystallography, photophysical methods, and DFT calculations to gain deeper insight into the nature of conjugation in these new systems.[c]-Annulation stabilized by Clar's sextets: Pyrene-based extended π-systems with [c]-annulated five-membered heterocycles (see figure) have been synthesized and studied by X-ray structure analysis as well as photophysical investigations, which revealed significant stabilization by benzenoid substructures.
      PubDate: 2017-11-16T08:36:20.610651-05:
      DOI: 10.1002/chem.201703988
  • Photoredox Catalysis with Metal Complexes Made from Earth-Abundant
    • Authors: Christopher B. Larsen; Oliver S. Wenger
      Abstract: Photoredox chemistry with metal complexes as sensitizers and catalysts frequently relies on precious elements such as ruthenium or iridium. Over the past 5 years, important progress towards the use of complexes made from earth-abundant elements in photoredox catalysis has been made. This review summarizes the advances made with photoactive CrIII, FeII, CuI, ZnII, ZrIV, Mo0, and UVI complexes in the context of synthetic organic photoredox chemistry using visible light as an energy input. Mechanistic considerations are combined with discussions of reaction types and scopes. Perspectives for the future of the field are discussed against the background of recent significant developments of new photoactive metal complexes made from earth-abundant elements.Metals in a new light: This review summarizes the advances made to the field of photoactive earth-abundant complexes in the context of synthetic organic photoredox chemistry using visible light as an energy input. Mechanistic considerations are combined with discussions of reaction types and scopes.
      PubDate: 2017-11-16T08:36:08.891834-05:
      DOI: 10.1002/chem.201703602
  • Mechanistic Studies on the Role of [CuII(CO3)n]2−2n as a Water Oxidation
           Catalyst: Carbonate as a Non-Innocent Ligand
    • Authors: Amir Mizrahi; Eric Maimon, Haim Cohen, Haya Kornweitz, Israel Zilbermann, Dan Meyerstein
      Abstract: Recently it was reported that copper bicarbonate/carbonate complexes are good electro-catalysts for water oxidation. However, the results did not enable a decision whether the active oxidant is a CuIII or a CuIV complex. Kinetic analysis of pulse radiolysis measurements coupled with DFT calculations point out that CuIII(CO3)n3−2n complexes are the active intermediates in the electrolysis of CuII(CO3)n2−2n solution. The results enable the evaluation of E°[(CuIII/II(CO3)n)aq]≈1.42 V versus NHE at pH 8.4. This redox potential is in accord with the electrochemical report. As opposed to literature suggestions for water oxidation, the present results rule out single-electron transfer from CuIII(CO3)n3−2n to yield hydroxyl radicals. Significant charge transfer from the coordinated carbonate to CuIII results in the formation of C2O62− by means of a second-order reaction of CuIII(CO3)n3−2n. The results point out that carbonate stabilizes transition-metal cations at high oxidation states, not only as a good sigma donor, but also as a non-innocent ligand.Carbonate proven guilty: It is shown that CuIII(CO3)33− is the active species in the CuII(CO3)n2−2n electrocatalyzed water oxidation reaction. The results point out that carbonate stabilizes transition-metal cations at high oxidation states, not only as a good sigma donor, but also as a non-innocent ligand.
      PubDate: 2017-11-16T08:35:38.255821-05:
      DOI: 10.1002/chem.201703742
  • Synthesis and optical properties of phenanthroline-derived Schiff
           base-like dinuclear Ru(II)-Ni(II) complexes
    • Authors: Hannah Kurz; Charles Lochenie, Kristina G. Wagner, Sandra Schneider, Matthias Karg, Birgit Weber
      Abstract: Two phenanthroline-derived Schiff base-like ligands with a covalently-linked Ru(II) phosphorescent unit were synthesised and converted into bimetallic Ru(II)-Ni(II) complexes. The optical properties were studied to examine a possible photoluminescence quenching through a non-radiative energy transfer upon Coordination Induced Spin State Switch (CISSS) at the Ni(II) centre. Therefore the metalloligands and the Ni(II) complexes were studied by UV-Vis absorbance as well as steady-state and time-resolved emission spectroscopy in MeCN and pyridine solutions. It is demonstrated that the nature of the bridging ligand between the Ru(II) donor and the Ni(II) acceptor strongly influences the photophysical behaviour upon CISSS. For the complex with a phenazine bridge, photoluminescense quenching is observed in the presence of a paramagnetic Ni(II) centre.
      PubDate: 2017-11-16T08:25:56.216906-05:
      DOI: 10.1002/chem.201704632
  • Nitrite-Enhanced Charge Transfer to and from Single Polyaniline Nanotubes
    • Authors: Jianyun Liu; Xiuting Li, Christopher Batchelor-McAuley, Guodong Zhu, Richard G. Compton
      Abstract: As Liu et al. reported previously (Appl. Mater. Today 2017, 7, 239–245), the charge transfer to partially oxidized polyaniline (PANI) nanotubes in electrochemical reactions is heavily limited due to the non-conductivity of the reduction/oxidation products. In this paper, the doping level of individual PANI nanotubes was substantially enhanced using nitrite as an electron acceptor in sulfuric acid aqueous solution as recorded by the nano-impact method. The charge transferred to one single tube during reduction process is close to the theoretical value of 170±112 pC per tube (assuming 2-electron reduction for the PANI tubes studied), while the charge during PANI oxidation is dramatically decreased. Reaction processes are proposed based on the oxidative properties of nitrite in acid solution. UV–visible spectroscopy analysis further confirms an oxidation–reduction reaction between PANI and nitrite. In contrast the electrochemical reaction of ensembles (21 μg cm−1) of PANI tubes on glassy carbon electrodes simply show limited electrocatalytic activity.The doping level of individual polyaniline (PANI) nanotubes was substantially enhanced by using nitrite as an electron acceptor in sulfuric acid aqueous solution as recorded by the nano-impact method.
      PubDate: 2017-11-16T08:11:27.543835-05:
      DOI: 10.1002/chem.201704055
  • The Trifluoromethyl Sulfinyl and Oxathiyl Radicals
    • Authors: Zhuang Wu; Jian Xu, Guohai Deng, Xianxu Chu, Liubov Sokolenko, Tarek Trabelsi, Joseph S. Francisco, André K. Eckhardt, Peter R. Schreiner, Xiaoqing Zeng
      Abstract: Two hitherto unreported sulfur-centered radicals CF3SO. and CF3OS. were generated in the gas phase through high-vacuum flash pyrolyses of sulfoxide CF3S(O)X (X=CF3, Cl, PhO) precursors. The CF3OS. molecule is the first experimental example that constitutes an oxathiyl radical. It was isolated and characterized by combining matrix-isolation IR and UV/Vis spectroscopy with quantum chemical computations up to the UCCSD(T)-F12/cc-pVTZ-F12 level of theory. Upon UV light irradiation (254 or 266 nm), sulfinyl radical (CF3SO.) isomerizes to oxathiyl radical (CF3OS.) in cryogenic noble gas matrices (Ar and Ne). Natural population analyses at the BP86/def2-TZVPP//UCCSD(T)-F12/cc-pVTZ-F12 level suggest that the spin density in CF3OS. is mainly localized on the sulfur atom (0.86), whereas, in CF3SO. the spin density is almost equally distributed on the sulfur (0.55) and oxygen (0.43) atoms.The hitherto unknown oxathiyl radical CF3OS. was generated through either thermal or photolytic isomerization of the sulfinyl radical CF3SO.. Both radicals were characterized for the first time by combining matrix-isolation IR and UV/Vis spectroscopy with quantum chemical computations.
      PubDate: 2017-11-16T08:05:38.992726-05:
      DOI: 10.1002/chem.201705142
  • Dibenzohexacene: Stabilization Through Additional Clar Sextets
    • Authors: Elias C. Rüdiger; Matthias Müller, Silke Koser, Frank Rominger, Jan Freudenberg, Uwe H. F. Bunz
      Abstract: Interested in efficient charge transport materials and acene chemistry, we considered pushing the limits of established systems. The cover figure illustrates the idea of stabilizing hexacene by introduction of two additional Clar sextets. Phenanthrenylation of a dibromo-pentacene precursor furnishes a well-soluble and fairly stable bisbenzannulated hexacene with characteristic optoelectronic properties. Proof-of-concept field effect transistors show promising hole mobilities of up to 0.22 cm2 V−1 s−1. More information can be found in the Communication by H. Freudenberg, U. H. F. Bunz et al. (
      DOI : 10.1002/chem.201704103).
      PubDate: 2017-11-16T08:05:30.360545-05:
  • Catalytic Synthesis of Indolines via Hydrogen Atom Transfer to
           Cobalt(III)-Carbene Radicals
    • Authors: Alexander S. Karns; Monalisa Goswami, Bas de Bruin
      Abstract: We report a new method for the synthesis of indolines from o-aminobenzylidine N-tosylhydrazones proceeding through a cobalt(III)-carbene radical intermediate. This methodology employs the use of inexpensive commercially-available reagents and allows for the transformation of easily derivatized benzaldehyde-derived precursors to functionalized indoline products. This transformation takes advantage of the known propensity of radicals to undergo rapid intramolecular 1,5-hydrogen atom transfer (1,5-HAT) to form more stabilized radical intermediates. Computational investigations using density functional theory identify remarkably low barriers for 1,5-HAT and subsequent radical rebound displacement, providing support for the proposed mechanism. We explore the effect of a variety of nitrogen substituents, and highlight the importance of adequate resonance stabilization of radical intermediates to the success of the transformation. Furthermore, we evaluate the steric and electronic effects of substituents on the aniline ring. This transformation is the first reported example of the synthesis of nitrogen-containing heterocycles from cobalt(III)-carbene radical precursors.
      PubDate: 2017-11-16T06:56:00.865679-05:
      DOI: 10.1002/chem.201704626
  • Teaching old compounds new tricks: DDQ-Photocatalyzed C-H Amination of
           Arenes with Carbamates, Urea and N-Heterocycles
    • Authors: Somnath Das; Palani Natarajan, Burkhard König
      Abstract: The C-H amination of benzene derivatives was achieved using DDQ as photocatalyst and BocNH₂ as the amine source under aerobic conditions and visible light irradiation. Electron-deficient and electron-rich benzenes react as substrates with moderate to good product yields. The amine scope of the reaction comprises Boc-amine, carbamates, pyrazoles, sulfonimide and urea. Preliminary mechanistic investigations indicate a charge transfer complex between the amine and DDQ as essential intermediate of the reaction. The reactivity of amines and arenes in the photocatalytic reaction is therefore predictable from simple UV measurements.
      PubDate: 2017-11-16T06:55:23.724966-05:
      DOI: 10.1002/chem.201705442
  • Effect of second-order spin-orbit coupling on the interaction between spin
           states in spin crossover systems
    • Authors: Carmen Sousa; Alex Domingo, Coen de Graaf
      Abstract: The second-order spin-orbit coupling is evaluated in two transition metal complexes to establish the effect on the deactivation mechanism of the excited low-spin state in systems that undergo spin transitions under the influence of light. We compare the standard perturbational approach to calculate the second-order interaction with a variational strategy based on effective Hamiltonian theory and show that the former one can only be applied in some special cases and even then gives results that largely overestimate the interaction. The combined effect of geometry distortions and second-order spin-orbit coupling leads to sizeable interactions for states that are nearly uncoupled in the symmetric (average) structure of the complex. This opens the possibility of a direct deactivation from the singlet and triplet states in the metal-to-ligand charge-transfer manifold into the final high-spin state as suggested from the interpretation of experimental data but so far not supported by theoretical descriptions of the light-induced spin crossover.
      PubDate: 2017-11-16T06:25:25.064318-05:
      DOI: 10.1002/chem.201704854
  • Pacman Compounds: From Energy Transfer to Cooperative Catalysis
    • Authors: Philipp Lang; Matthias Schwalbe
      Abstract: In this Concept article we present the syntheses and application of homo and heterodinuclear “Pacman” compounds. This architecture implies that two metal coordination fragments are brought in close vicinity to each other via a covalent linkage to either support energy transfer between the two units or cooperative transformation of a substrate. Nature has shown that the combination of metal fragments, in particular two different metals, can dramatically improve the efficiency of small molecule activation. We exemplify this strategy for the activation of water, dioxygen and carbon dioxide. Furthermore, we present artificial systems in which a positive effect on the catalytic performance because of the combination of two (different) metal centers could be observed. Thus, Pacman-type compounds are very well suited as structural and functional models for their biological counterparts.High score! (Hetero-)Pacman architectures can be used to place two (different) metal coordination fragments in close vicinity to each other. This structural motif can either lead to energy or electron-transfer interactions. In latter case the cooperative activation of small molecules becomes possible that can lead to catalytic applications such as water oxidation and CO2 or O2 reduction.
      PubDate: 2017-11-16T05:05:55.928421-05:
      DOI: 10.1002/chem.201703675
  • Frontispiece: Magnetic Nanotransducers in Biomedicine
    • Authors: Agostina Grillone; Gianni Ciofani
      Abstract: Owing to their abilities to identify diseased conditions, to modulate biological processes, and to control cellular activities, magnetic nanoparticles have become one of the most popular nanomaterials in the biomedical field: targeted drug delivery, controlled drug release, hyperthermia treatment, imaging, and stimulation of several biological entities are just some of the several tasks that can be accomplished by taking advantage of magnetic nanoparticles in tandem with magnetic fields. For more details, see the Concept article by A. Grillone and G. Ciofani on page 16109 ff.
      PubDate: 2017-11-16T05:00:39.283814-05:
      DOI: 10.1002/chem.201786461
  • Frontispiece: Regioselective Direct C-Alkenylation of Indoles
    • Authors: Marino Petrini
      Abstract: The regioselective introduction of an alkenyl moiety on indoles can be achieved by exploiting the intrinsic reactivity of this heterocycle toward C-3 substitution. Conversely, the appropriate functionalization of the indole nitrogen atom allows to direct the alkenylation at C-2. Metal-catalyzed C−H activation and reaction with alkenes, hydroindolation of alkynes and condensation reactions with carbonyl derivatives are the main procedures adopted for the alkenylation of indoles. For more information see the Review article by M. Petrini on page 16115 ff.
      PubDate: 2017-11-16T05:00:39.242126-05:
      DOI: 10.1002/chem.201786462
  • Frontispiece: Tuning Electron Flux through Nitrogenase with Methanogen
           Iron Protein Homologues
    • Authors: Caleb J. Hiller; Martin T. Stiebritz, Chi Chung Lee, Jasper Liedtke, Yilin Hu
      Abstract: A homologue-based approach facilitates capture of multiple CO molecules at the nitrogenase cofactor site via reduction of the electron flow through a nitrogenase hybrid between homologous component proteins, suggesting the utility of this approach in tuning electron fluxes to enable trapping of substrates and relevant intermediates for mechanistic investigations of this enzyme. For more information, see the Communication by Y. Hu et al. on page 16152 ff.
      PubDate: 2017-11-16T05:00:36.518053-05:
      DOI: 10.1002/chem.201786463
  • Frontispiece: Rational Design of a Bifunctional, Two-Fold Interpenetrated
           ZnII-Metal–Organic Framework for Selective Adsorption of CO2 and
           Efficient Aqueous Phase Sensing of 2,4,6-Trinitrophenol
    • Authors: Sandeep Singh Dhankhar; Nayuesh Sharma, Sandeep Kumar, T. J. Dhilip Kumar, C. M. Nagaraja
      Abstract: A bifunctional MOF for selective CO2 capture and efficient aqueous-phase sensing of 2,4,6-trinitrophenol (TNP) has been rationally designed and synthesized. Owing to the presence of basic (−NH2) functionalized pore surface, the MOF exhibits selective adsorption of CO2 with a high value of heat of adsorption (Qst = 46.5 kJ mol−1) which is about 10 kJ mol−1 higher than that of the analogues MOF without −NH2 functionality. Further, the MOF shows highly selective, aqueous-phase sensing of TNP over other competing NACs. The observed selectivity of MOF for CO2 capture and sensing of TNP has been correlated to the stronger interaction of the guest molecules with the basic −NH2 groups in the 1D channels, unveiled from the DFT calculations. For more information see the Full Paper by C. M. Nagaraja et al. on page 16204 ff.
      PubDate: 2017-11-16T05:00:32.749897-05:
      DOI: 10.1002/chem.201786464
  • Cubane Cross-Coupling and Cubane–Porphyrin Arrays
    • Authors: Stefan S. R. Bernhard; Gemma M. Locke, Shane Plunkett, Alina Meindl, Keith J. Flanagan, Mathias O. Senge
      Abstract: Invited for the cover of this issue is the group of Mathias O. Senge at Trinity College Dublin. The image depicts cubanes and new methods to attach functionalities onto the cubane core. Read the full text of the article at 10.1002/chem.201704344.“Our interest in cubane arose not only from its aesthetic beauty, but also from its interesting properties.” Read more about the story behind the cover in the Cover Profile and about the research itself on page ▪▪ ff. (
      DOI : 10.1002/chem.201704344).
      PubDate: 2017-11-16T04:56:15.315197-05:
  • Cubane Cross-Coupling and Cubane–Porphyrin Arrays
    • Authors: Stefan S. R. Bernhard; Gemma M. Locke, Shane Plunkett, Alina Meindl, Keith J. Flanagan, Mathias O. Senge
      Abstract: Cubane–aryl systems can now be achieved by using an improved nickel-catalyzed redox-active ester coupling strategy. After systematic investigations, the key obstacle of cubane cross-coupling was identified and circumvented by altering the electron density of the transition metal through an adjusted choice of ligand. Furthermore, Sonogashira coupling of alkynyl-arm-extended cubanes was demonstrated by the synthesis of cubane–porphyrin arrays, proving the general compatibility of cubanes and Pd-catalyzed cross-coupling reactions. More information can be found in the Communication by M. O. Senge et al. (
      DOI : 10.1002/chem.201704344).
      PubDate: 2017-11-16T04:55:29.580724-05:
  • Regio- and Stereoselective Iron-Catalyzed Oxyazidation of Enamides using
           Hypervalent Iodine Reagent
    • Authors: Isabelle Gillaizeau; sylvain bertho, Romain Rey-Rodriguez, Pascal retailleau, Cyril Colas
      Abstract: A novel regio- and diastereoselective iron-catalyzed intermolecular oxyazidation of enamides using various azidobenziodoxolone (ABX) derivatives is presented. A variety of alpha-N3 amino derivatives and of alpha-N3 piperidines is nicely synthesized in good yields and under mild reaction conditions. The reaction involves a radical process using cheap FeCl2 as the initiator.
      PubDate: 2017-11-16T04:25:30.50153-05:0
      DOI: 10.1002/chem.201704499
  • Three-Component Synthesis and Photophysical Properties of Novel
           Coumarin-based Merocyanines
    • Authors: Julian Papadopoulos; Kay Merkens, Thomas J. J. Müller
      Abstract: Novel E-configurated 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 red shift at increasing water contents in THF.
      PubDate: 2017-11-15T15:55:30.514782-05:
      DOI: 10.1002/chem.201704912
  • A versatile strategy to main chain sulfur/selenium functionalized
           polycarbonates via macro-ring closure of diols and subsequent ring-opening
    • Authors: Chao Wei; Yan Zhang, Bingkun Yan, Yue Xu, Zhengzhen Du, Meidong Lang
      Abstract: 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 applications in stimuli responsive field and inflammation/cancer targeting. With these desirable results, it is revealed that this versatile technique will provide a broad-reaching method to the next generation of innovative materials, especially, well-defined biodegradable chalcogen-based main chain functional biomaterials.
      PubDate: 2017-11-15T09:55:24.792295-05:
      DOI: 10.1002/chem.201704301
  • Structure-Property Relationships in CuII-binding Tetramolecular
           G-Quadruplex DNA
    • Authors: David M. Engelhard; Lukas M. Stratmann, Guido H. Clever
      Abstract: A series of artificial metal-base tetrads composed of a CuII cation coordinating to four pyridines, covalently attached to the ends of tetramolecular G-quadruplex DNA strands [LA-Dd(G4)]4 (LA-D = ligand derivatives), was systematically studied. Structurally, the square-planar [Cu(pyridine)4] complex behaves analogous to the canonical guanine quartet. Copper coordination to all studied ligand derivatives was found to increase G-quadruplex thermodynamic stability, tolerating a great variety of ligand linker lengths (1 - 5 atoms) and thus demonstrating the robustness of the chosen ligand design. Only at high linker lengths, the stabilizing effect of copper binding is compensated by the loss of conformational freedom. A previously reported ligand LE with chiral backbone enables incorporation at any oligonucleotide position. We show that ligand chirality distinctly steers CuII-induced G-quadruplex stabilization. 5′-End formation of two metal-base tetrads by tetramolecular G-quadruplex [LE2d(G)4]4 shows that stabilization in the presence of CuII is not additive. All results are based on UV-VIS thermal denaturation, thermal difference, Circular Dichroism experiments and molecular dynamics simulations.
      PubDate: 2017-11-15T08:21:25.251595-05:
      DOI: 10.1002/chem.201703409
  • C9/12 Ribbon-Like Structures in Hybrid Peptides Alternating α- and
           Thiazole-Based γ-Amino Acids
    • Authors: Clément Bonnel; Baptiste Legrand, Matthieu Simon, Jean Martinez, Jean-Louis Bantignies, Young Kee Kang, Emmanuel Wenger, Francois Hoh, Nicolas Masurier, Ludovic T. Maillard
      Abstract: According to their restricted conformational freedom, heterocyclic γ-amino acids are usually considered to be related to Z-vinylogous γ-amino acids. In this context, oligomers alternating α-amino acids and thiazole-based γ-amino acids (ATCs) were expected to fold into a canonical 12-helical shape as described for α/γ-hybrid peptides composed of cis-α/β-unsaturated γ-amino acids. However, through a combination of X-ray crystallography, NMR spectroscopy, FTIR experiments, and DFT calculations, it was determined that the folding behavior of ATC-containing hybrid peptides is much more complex. The homochiral α/(S)-ATC sequences were unable to adopt a stable conformation, whereas the heterochiral α/(R)-ATC peptides displayed novel ribbon structures stabilized by unusual C9/12-bifurcated hydrogen bonds. These ribbon structures could be considered as a succession of pre-organized γ/α dipeptides and may provide the basis for designing original α-helix mimics.A ribbon structure, stabilized by C9/12-hydrogen bonds, was determined in heterochiral hybrid peptides alternating α- and thiazole-based γ-amino acids (see figure).
      PubDate: 2017-11-15T07:12:26.50917-05:0
      DOI: 10.1002/chem.201704001
  • Nanoscale Metal–Organic Frameworks Decorated with Graphene Oxide for
           Magnetic Resonance Imaging Guided Photothermal Therapy
    • Authors: Jing Meng; Xiujin Chen, Yang Tian, Zhongfeng Li, Qingfeng Zheng
      Abstract: Imaging-guided photothermal therapy (PTT) provides an attractive way to treat cancer. A composite material of a nanoscale metal–organic framework (NMOF) and graphene oxide (GO) has been prepared for potential use in tumor-guided PTT with magnetic resonance imaging (MRI). The NMOFs containing Fe3+ were prefabricated with an octahedral morphology through a solvothermal reaction to offer a strong T2-weighted contrast in MRI. Then the NMOFs were decorated with GO nanosheets, which had good photothermal properties. After decoration, zeta-potential characterization shows that the aqueous stability of the composite material is enhanced, UV/Vis and near-infrared (NIR) spectra confirm that NIR absorption is also increased, and photothermal experiments reveal that the composite materials express higher photothermal conversion effects and conversion stability. The fabricated NMOF/GO shows low cytotoxicity, effective T2-weighted contrast of MRI, and positive PTT behavior for a tumor model in vitro. The performance of the composite NMOF/GO for MRI and PTT was also tested upon injection into A549 tumor-bearing mice. The studies in vivo revealed that the fabricated NMOF/GO was efficient in T2-weighted imaging and ablation of the A549 tumor with low cytotoxicity, which implied that the prepared composite contrast agent was a potential multifunctional nanotheranostic agent.Inducing hotspots: A composite of a nanoscale metal–organic framework (NMOF) and graphene oxide (GO), NMOF/GO, integrates T2-weighted magnetic resonance imaging (MRI) contrast and photothermal therapy functions into one system. The composite is tested in vitro and in vivo for MRI-guided photothermal therapy to dispel tumors (see figure). The results indicate that the NMOF/GO composite can be considered a new class of imaging-guided therapy agent for antitumor applications.
      PubDate: 2017-11-15T06:46:38.582168-05:
      DOI: 10.1002/chem.201702573
  • Magnetic γ′-Fe4N/Fe3C, χ-Fe5C2, and θ-Fe3C by a Simple Route for
           Application as Electrochemical Catalysts
    • Authors: Xiang Lei; Zhantong Ye, Nan Zhao, Feifei Lei, Hua Yang
      Abstract: A new and simple method to fabricate magnetic Fe4N/Fe3C samples is reported. Meanwhile, pure phase iron carbides (θ-Fe3C and χ-Fe5C2) were obtained by controlling experimental conditions. The structures, magnetic properties, and morphology of the samples were investigated according to the generalized analysis of X-ray diffraction, X-ray photoelectron spectroscopy, as well as transmission electron microscopy and vibrating sample magnetometry. The magnetic properties measurement revealed the remarkable magnetic properties of the samples at 2 and 300 K. The application of the prepared samples as catalysts for oxygen evolution reaction was also investigated in alkaline solution. This simple and convenient route provides a new path to fabricate other metal nitrides and carbides.Iron man: The excellent magnetic properties and electrochemical catalytic performance of Fe4N/Fe3C was investigated. Careful control of reaction conditions gives rise to phase-pure carbides.
      PubDate: 2017-11-15T06:46:23.334225-05:
      DOI: 10.1002/chem.201704214
  • Mesoporous Silica Nanocarriers with Cyclic Peptide Gatekeeper: Specific
           Targeting of Aminopeptidase N and Triggered Drug Release by
           Stimuli-Responsive Conformational Transformation
    • Authors: Jeonghun Lee; Eun-Taex Oh, Yeji Han, Ha Gyeong Kim, Heon Joo Park, Chulhee Kim
      Abstract: Utilizing stimuli-responsive conformational transformation of a cyclic peptide as a gatekeeper for mesoporous nanocarriers has several advantages such as facile introduction of targeting capabilities, low enzymatic degradation during blood circulation and enhanced specific binding to selected cells. In this report, a Asn-Gly-Arg (NGR)-containing dual-functional cyclic peptide gatekeeper on the surface of mesoporous nanocarrier is prepared not only for active targeting of the aminopeptidase N (APN) expressed on cancer cells but also stimuli-responsive intracellular drug release triggered by a glutathione (GSH)-induced conformational transformation of the peptide gatekeeper. The peptide gatekeeper on the surface of nanocarriers exhibits on–off gatekeeping by conformational transformation triggered by intracellular glutathione of the cancer cells. H1299 cells (high APN expression) showed greater uptake of the nanocarrier by endocytosis and higher apoptosis than A549 cells (low APN expression).Watch out for the gatekeeper: A NGR-containing dual-functional cyclic peptide gatekeeper on the surface of mesoporous nanocarrier is prepared not only for active targeting of the aminopeptidase N expressed on cancer cells but also stimuli-responsive intracellular drug release triggered by a glutathione-induced conformational transformation of the peptide gatekeeper.
      PubDate: 2017-11-15T06:46:15.247625-05:
      DOI: 10.1002/chem.201704309
  • Immobilised Electrocatalysts: Nafion Particles Doped with Ruthenium(II)
    • Authors: Haiying Yang; Xiuting Li, Christopher Batchelor-McAuley, Stanislav V. Sokolov, Enno Kätelhön, Richard G. Compton
      Abstract: Nafion particles doped with ruthenium(II) tris(2,2′-bipyridyl) are synthesized by using a re-precipitation method. Characterization including SEM sizing and quantification of Ru(bpy)32+ in the Nafion particles using UV/Vis spectroscopy was conducted. The synthesized Ru-Nafion particles were investigated electrochemically at both ensemble and single particle levels. Voltammetry of the drop-cast Ru-Nafion particles evidences the successful incorporation of Ru(bpy)32+ into the Nafion particle but only a small fraction of the incorporated Ru(bpy)32+ was detected due at least in part to the formation of the likely agglomerated and irregular “mat” associated with the dropcast technique. In contrast, nano-impact experiments provided a quantitative determination of the amount of Ru(bpy)32+ in single Ru-Nafion particles. Finally, oxidation of solution-phase oxalate mediated by Ru(bpy)32+ within individual Nafion particles was observed, showing the electrocatalytic properties of the Ru-Nafion particles.Nafion particles doped with ruthenium(II) tris(2,2’-bipyridyl) were synthesized by using the re-precipitation method. A quantitative determination of the amount of Ru(bpy)32+ in single Ru-Nafion particles was achieved via the nanoimpact method and the electrocatalytic performance of the Ru-Nafion particles towards oxidation of oxalate was further demonstrated.
      PubDate: 2017-11-15T06:45:34.01196-05:0
      DOI: 10.1002/chem.201704418
  • An On-Surface Reaction Confined within a Porous Molecular Template
    • Authors: Chris J. Judd; Neil R. Champness, Alex Saywell
      Abstract: On-surface reactions based on metal-catalysed Ullmann coupling have been successfully employed to synthesise a wide variety of covalently coupled structures. Substrate chemistry and topology are both known to effect the progression of an on-surface reaction; offering routes to control efficiency and selectivity. Here, we detail ultra-high vacuum scanning probe microscopy experiments showing that templating a catalytically active surface, via a supramolecular template, influences the reaction pathway of an on-surface Ullmann-type coupling reaction by inhibiting one potential intermediate structure and stabilising another.Tiny Templates: On-surface reactions can be performed on catalytic metal surfaces to combine molecular units into extended arrays. The structure of the catalyst, as well as its chemistry, is known to influence the shape of the product. Templating the catalyst with a porous self-assembled network gives rise to nanometer sized pores in which a chemical reaction can occur; leading to a different product to that formed on a non-templated surface.
      PubDate: 2017-11-15T03:22:31.355067-05:
      DOI: 10.1002/chem.201704693
  • C−H Insertions by Iron Porphyrin Carbene: Basic Mechanism and Origin
           of Substrate Selectivity
    • Authors: Rahul L. Khade; Yong Zhang
      Abstract: Recent experimental reports of heme carbene C−H insertions show promising results for sustainable chemistry due to good yield and selectivity, low cost of iron, and low/no toxicity of hemes. But mechanistic details are mostly unknown. Despite structural similarity and isoelectronic nature between heme carbene and the FeIV=O intermediate, our quantum chemical studies with detailed geometric and electronic information for the first time reveal an FeII-based, concerted, hydride-transfer mechanism, which is different from the FeIV-based stepwise hydrogen atom transfer mechanism for C−H functionalization by native heme enzymes. A trend of broad range experimental C−H insertion yields (0–88 %) of five different C−H bonds, including mostly non-functionalized moieties, was well reproduced. Results suggest that the substrate selectivity originates from the hydride formation capability. The predicted kinetic isotope effects were also in excellent agreement with experiment. Useful geometry, charge, and energy parameters well correlated with barriers were reported. These results provide the first theoretical evidence that carbene formation is the overall rate-limiting step, and suggest a key role of the formation of strong electrophilic heme carbene in developing heme-based C−H insertion catalysts and biocatalysts.Dank hemes: Heme carbene C−H insertion is good for sustainable chemistry. Our results for the first time show: 1) the FeII-based hydride transfer, early TS; 2) the conformation and spin-state effects on TS; 3) the useful geometry, charge, and energy parameters to well correlate with ΔG≠; 4) the theoretical explanation of a broad range experimental C−H insertion yields; and 5) the significance of strong electrophilic heme carbene with low formation barrier for catalyst development.
      PubDate: 2017-11-15T03:22:21.977032-05:
      DOI: 10.1002/chem.201704631
  • Zn2+ Interrupts R4-R3 Association Leading to Accelerated Aggregation of
           Tau Protein
    • Authors: A. C. Jiji; A. Arshad, S. R. Dhanya, P. S. Shabana, C. K. Mehjubin, Vinesh Vijayan
      Abstract: Direct binding of divalent metal ion, especially Zn2+, have been shown to increase the rate of tau aggregation and enhance tau toxicity in cells. Hence, understanding the molecular basis of the Zn2+-accelerated tau aggregation can potentially determine the molecular interactions modulating tau aggregation. Herein, we show that Zn2+ coordinates through the cysteine in R3 repeat and significantly accelerates the aggregation rate of the three repeat tau constructs (K19) but that the coordination is incapable of increasing the aggregation rate of the 20 amino acid peptide derived from the R3 repeat (R3) of tau. The NMR characterization of the binding of Zn2+ to K19, together with the aggregation studies with K19, R3 and R4 peptides, reveal the presence of an aggregation-inhibitory interaction between the R3 and R4 repeat of K19. Our data show that binding of Zn2+ to R3 repeat of tau, weaken the aggregation-inhibiting influence between R3 and R4 repeats, leading to faster aggregation of tau protein.Blocking their neighbour: The three repeat tau exist in an aggregation-inhibitory conformation with residues in R4 repeat preventing the R3 repeat from aggregation. The binding of ZnII to the R3 repeat weakens the inhibitory effect of R4 and accelerate the aggregation of tau protein.
      PubDate: 2017-11-15T03:21:54.281518-05:
      DOI: 10.1002/chem.201704555
  • A Novel Approach to Synthesise a Dual-Mode Luminescent Composite Pigment
           for Uncloneable High-Security Codes to Combat Counterfeiting
    • Authors: Kanika; Pawan Kumar, Satbir Singh, Bipin Kumar Gupta
      Abstract: A strategy is demonstrated to protect valuable items, such as currency, pharmaceuticals, important documents, etc. against counterfeiting, by marking them with luminescent security codes. These luminescent security codes were printed by employing luminescent ink formulated from a cost effective dual-mode luminescent composite pigment of Gd1.7Yb0.2Er0.1O3 and Zn0.98Mn0.02S phosphors using commercially available PVC Gold medium. In the composite, Gd1.7Yb0.2Er0.1O3 and Zn0.98Mn0.02S account for upconversion and downconversion processes, respectively. The synthesis procedure of the composite involves the admixing of Gd1.7Yb0.2Er0.1O3 nanorods and Zn0.98Mn0.02S phosphor, synthesised by hydrothermal and facile solid-state reaction methods, respectively. The structural, morphological, microstructural, and photoluminescent features of Gd1.7Yb0.2Er0.1O3 nanorods, Zn0.98Mn0.02S phosphor and composite were characterised by using XRD, SEM, TEM, and photoluminescence (PL) techniques, respectively. The distribution of PL intensity of the printed pattern was examined by using confocal PL mapping microscopy. The obtained results reveal that security codes printed using ink formulated from this bi-luminescent composite pigment provide dual-stage security against counterfeiting.Stop fraud! Demonstration of uncloneable security code of a new emerging cost effective dual-mode luminescent pigment for anti-counterfeiting applications
      PubDate: 2017-11-15T03:21:46.604373-05:
      DOI: 10.1002/chem.201704076
  • Synthesis of Tetranuclear Palladium(II) Complexes and Their Catalytic
           Activity for Cross-Coupling Reactions
    • Authors: Florian Puls; Nils Richter, Olga Kataeva, Hans-Joachim Knölker
      Abstract: We have developed a short and simple synthesis of tetranuclear palladium(II) complexes that have been structurally confirmed by X-ray analysis. These complexes were formed in about 30 % overall yield by spontaneous metalation of dimethylaminoarene derivatives and exhibit a high stability. We have studied the utility of the tetranuclear palladium(II) complexes as precatalysts for Mizoroki–Heck and Suzuki–Miyaura cross-coupling reactions. Our novel complexes show excellent catalytic activities with high turnover numbers (TON) and high turnover frequencies (TOF) (e.g., for the Suzuki–Miyaura reaction: TON up to 538000 and TOF up to 23400 h−1 at room temperature).High catalytic activity by multiple palladium centers: Reaction of substituted diaryl ethers and diarylamines with two equivalents of palladium(II) acetate afforded tetranuclear palladium(II) complexes. These complexes showed excellent catalytic activity for Mizoroki–Heck and Suzuki–Miyaura cross-coupling reactions with high TON and TOF values.
      PubDate: 2017-11-15T03:21:36.631992-05:
      DOI: 10.1002/chem.201703926
  • A Four-Step Synthesis of Substituted 5,11-Dicyano-6,12-diaryltetracenes
           with Enhanced Stability and High Fluorescence Emission
    • Authors: Nicolas Kerisit; Przemyslaw Gawel, Brian Levandowski, Yun-Fang Yang, Víctor García-López, Nils Trapp, Laurent Ruhlmann, Corinne Boudon, Kendall N. Houk, François Diederich
      Abstract: A four-step synthesis of substituted 5,11-dicyano-6,12-diaryltetracenes was developed, starting from readily available para-substituted benzophenones. The key step of this straightforward route is the complex cascade reaction between tetraaryl[3]cumulenes and tetracyanoethene (TCNE) resulting in 5,5,11,11-tetracyano-5,11-dihydrotetracenes. The mechanism of this transformation was reinvestigated by means of theoretical calculations. The target tetracenes were obtained by a newly developed decyanation/aromatization reaction catalyzed by CuI or CuII complexes in solution, conditions compatible with a broad range of functional groups. A computational mechanistic study sheds light on this transformation. Structures of all tetracene derivatives were confirmed by X-ray crystallography. The presented dicyanotetracene derivatives exhibit outstanding optoelectronic properties and enhanced photostability, significantly surpassing the reference rubrene (5,6,11,12-tetraphenyltetracene).From tetra steps to tetracenes: The presented substituted 5,11-dicyano-6,12-diaryltetracenes are synthesized from 5,5,11,11-tetracyano-5,11-dihydrotetracenes, using a newly developed decyanation/aromatization reaction catalyzed by CuI or CuII complexes in solution. The mechanism of this transformation is explored by theoretical calculations. The obtained tetracene derivatives exhibit outstanding optoelectronic properties and enhanced photostability.
      PubDate: 2017-11-15T03:21:28.648781-05:
      DOI: 10.1002/chem.201703903
  • The Nature of Hydrated Protons on Platinum Surfaces
    • Authors: Youngsoon Kim; Chanwoo Noh, YounJoon Jung, Heon Kang
      Abstract: The nature of hydrated protons formed at water/metal interfaces is one of the most intriguing research questions in the field of interfacial chemistry. We prepared coadsorption layers of hydrogen and water on a Pt(111) surface in ultrahigh vacuum and studied the ionization of adsorbed hydrogen atoms to H+ ions by employing a combined experimental and theoretical approach. Spectroscopic evidence obtained by mass spectrometry and reflection absorption infrared spectroscopy as well as corresponding density functional theory calculations consistently show that adsorbed hydrogen atoms ionize into multiply hydrated proton species (H5O2+, H7O3+, and H9O4+) on the surface, rather than H3O+. Then, upon addition of a water overlayer, the metal-bound hydrated protons spontaneously evolve into three-dimensional fully hydrated proton structures through proton transfer along the water overlayer. The stability of hydrated protons on the Pt surface and their bulk dissolution behavior suggest the possibility that surface hydrated protons are a key intermediate in electrochemical interconversion between adsorbed H atoms and H+(aq) in water electrolysis and hydrogen evolution reactions.Intermediates in Volmer reactions: Adsorbed hydrogen atoms ionize into multiply hydrated protons (H5O2+, H7O3+, and H9O4+) on a Pt surface assisted by water layers. These hydrated protons spontaneously evolve into fully hydrated structures along the water overlayer. Surface hydrated protons may be important intermediates in the electrochemical Volmer reaction on a Pt electrode.
      PubDate: 2017-11-15T03:21:14.970838-05:
      DOI: 10.1002/chem.201703882
  • Perfluoroalkyltricyanoborate and Perfluoroalkylcyanofluoroborate Anions:
           Building Blocks for Low-Viscosity Ionic Liquids
    • Authors: Johannes Landmann; Jan A. P. Sprenger, Philipp T. Hennig, Rüdiger Bertermann, Matthias Grüne, Frank Würthner, Nikolai V. Ignat'ev, Maik Finze
      Abstract: The potassium perfluoroalkyltricyanoborates K[CnF2 n+1B(CN)3] [n=1 (1 d), 2 (2 d)] and the potassium mono(perfluoroalkyl)cyanofluoroborates K[CnF2 n+1BF(CN)2] [n=1 (1 c), 2 (2 c)] and [CnF2 n+1BF2(CN)]− [n=1 (1 b), 2 (2 b), 3 (3 b), 4 (4 b)] are accessible with perfect selectivities on multi-gram scales starting from K[CnF2 n+1BF3] and Me3SiCN. The K+ salts are starting materials for the preparation of salts with organic cations, for example, [EMIm]+ (EMIm=1-ethyl-3-methylimidazolium). These [EMIm]+ salts are hydrophobic room-temperature ionic liquids (RTILs) that are thermally, chemically and electrochemically very robust, offering electrochemical windows up to 5.8 V. The RTILs described herein, exhibit very low viscosities with a minimum of 14.0 mPa s at 20 °C for [EMIm]1 c, low melting points down to −57 °C for [EMIm]2 b and extraordinary high conductivities up to 17.6 mS cm−1 at 20 °C for [EMIm]1 c. The combination of these properties makes these ILs promising materials for electrochemical devices as exemplified by the application of selected RTILs as component of electrolytes in dye-sensitised solar cells (DSSCs, Grätzel cells). The efficiency of the DSSCs was found to increase with a decreasing viscosity of the neat ionic liquid. In addition to the spectroscopic characterisation, single crystals of the potassium salts of the anions 1 b–d, 2 d, 3 b and 4 c as well as of [nBu4N]2 c have been studied by X-ray diffraction.Ionic liquids: Unique perfluoroalkylcyanoborate ionic liquids exhibiting high thermal, chemical and electrochemical stabilities and providing low viscosities and high conductivities were developed (see figure).
      PubDate: 2017-11-15T03:21:02.123915-05:
      DOI: 10.1002/chem.201703685
  • Shape-Controlled Synthesis of Au–Polypyrrole Composites Using
           Poly(4-vinylpyridine) Brush Grafted on Graphene Oxide as a Reaction
    • Authors: Guoke Xing; Wenqin Wang, Ke Wang, Ping Li, Tao Chen
      Abstract: Controlling the shape of the conducting polymer-noble metal composites is a key factor in determining their properties and applications. In this paper, we demonstrate a novel strategy to fabricate Au–polypyrrole (PPy) composites with unusual morphology using poly(4-vinylpyridine) (P4VP) brush grafted on graphene oxide (GO) as a reaction chamber. When the GO/P4VP brush bearing AuCl4− ions is exposed to pyrrole vapor or directly immersed into pyrrole solution, novel Au−PPy nanotubules and flower-like Au mesoparticles–PPy composites are formed on the surface of GO/P4VP brush, respectively. The application of the as-prepared GO/P4VP/Au−PPy composites in catalysis and surface-enhanced Raman scattering (SERS) are investigated. The relevant results exhibit that the GO/P4VP/Au−PPy nanotubules can act as an efficient catalyst for reduction of 4-nitrophenol, and the GO/P4VP/flower-like Au mesoparticles–PPy composites can be used as a sensor platform for the detection of organic molecules by SERS.A chemical garden: A novel strategy is employed to fabricate Au–polypyrrole composites with unusual morphology: Au−PPy nanotubules and flower-like Au mesoparticles–PPy composites are obtained by changing reaction process between AuCl4− ions loaded poly(4-vinylpyridine) brush grafted on graphene oxide and pyrrole monomer.
      PubDate: 2017-11-15T03:20:29.949169-05:
      DOI: 10.1002/chem.201703183
  • Enantioselective Hydrogenation of Imidazo[1,2-a]pyridines
    • Authors: Christoph Schlepphorst; Mario Wiesenfeldt, Frank Glorius
      Abstract: The first enantioselective synthesis of imidazo[1,2-a]pyridines via direct hydrogenation was achieved using a ruthenium/N-heterocyclic carbene (NHC) catalyst. The reaction forgoes the need for protecting or activating groups, proceeds with complete regioselectivity, good to excellent yields, enantiomeric ratios of up to 98:2, and tolerates a broad range of functional groups. 5,6,7,8-Tetrahydroimidazo[1,2-a]pyridines, which are found in numerous bioactive molecules, are directly obtained by this method and its applicability was demonstrated by the (formal) synthesis of several functional molecules.
      PubDate: 2017-11-15T01:50:36.436658-05:
      DOI: 10.1002/chem.201705370
  • Additive Enhanced Crystallization of Solution-Process for Planar
           Perovskite Solar Cells with Efficiency Exceeding 19%
    • Authors: Shuai You; Shiqing Bi, Jing Huang, Qiushuang Jia, Yuhe Yuan, Yanjie Xia, Zhenyu Xiao, Zhuzhu Sun, Jiangfeng Liu, Shujie Sun, Zhiqiang Zhao
      Abstract: To reduce intrinsic defect density in perovskite films, various additives are often added into the precursor solution. In this paper, a novel solution approach where isopropanol (IPA) was added into the precursor solution was developed for the preparation of normal planar perovskite solar cells (PSCs). A champion power conversion efficiency (PCE) of 19.70% was achieved with this approach. By adding IPA into the precursor solution, CH3NH3PbI3 perovskite showed better crystallization and stability, indicating improved film quality. Because of the improved morphology of perovskite crystal, the PCE of PSCs increased. In addition, the unencapsulated PSCs retained high output for up to 40 days in air at room temperature, indicating the stability of PSCs. These results might provide a new avenue for manufacturing high efficiency and high stability PSCs.
      PubDate: 2017-11-14T22:20:36.127804-05:
      DOI: 10.1002/chem.201704181
  • Assessing the Ligand Properties of NHC-Stabilized Phosphorus(I) Cations
    • Authors: Justin F Binder; Stephanie C Kosnik, Charles Lloyd Bergstrom Macdonald
      Abstract: The isolation and full characterization of a series of cationic metal carbonyl complexes bearing an N-heterocyclic carbene-stabilized phosphorus(I) ligand are reported. Specifically, the mononuclear coordination complexes [LM(CO)₅][BPh₄] (M = Cr, Mo, W), [LFe(CO)₄][BPh₄] and the dinuclear complexes [LMn₂(CO)₈][BPh₄] and [LCo₂(CO)₆][BPh₄], where L = [bis(1,3,4,5-tetramethylimidazol-2-ylidene)phosphanide]+, have all been isolated in the solid state and structurally confirmed by single crystal X-ray diffraction. The dicationic platinum complex [L₂PtCl₂][BPh₄] is also reported and fully characterized. The donor ability of [L]+ has been assessed using IR spectroscopy of its metal carbonyl complexes and using DFT calculations. The results suggest that [L]+ is a weak π-acceptor with moderate donor strength and thus it bridges the gap that exists between phosphines and amines in terms of ligand ability. Collectively, these molecules represent the first crystallographically characterized cationic metal carbonyl derivatives of a P(I) centered ligand and are a rare collection of cationic metal carbonyl complexes.
      PubDate: 2017-11-14T21:55:59.711555-05:
      DOI: 10.1002/chem.201705224
  • Highly Strained Organogold Complexes and Their Gold- or Rhodium-Catalyzed
    • Authors: Florian F. Mulks; Shirin Faraji, Frank Rominger, Andreas Dreuw, A. Stephen K. Hashmi
      Abstract: The synthesis and characterization of (NHC)(tricyclo[,7]hept-1-yl)gold(I) compounds is reported. Several of these organometallic compounds could be obtained by transmetalation from the organolithium precursor to the corresponding (NHC)gold(I) chlorides. These are by far the most strained stable organogold compounds reported so far. With these new compounds we were able to efficiently and selectively accomplish the first gold-catalyzed rearrangement of organogold compounds, even better yields were obtained by the first rhodium-catalyzed rearrangement of these organogold species. (E/Z)-Mixtures of (NHC)(cyclohex-2-en-1-ylidenemethyl)gold(I) were obtained, none of the other known rearrangement products of tricycloheptanes. Additional insight into the chemical and physical properties of the strained compounds was obtained by spectroscopic and computational studies.The most strained organogold complexes reported so far were synthesized and investigated by experiment, spectroscopy and theory regarding their reactivity, and their chemical and physical properties. This interesting insight into the chemistry of strained organogold complexes may open up new points of view concerning a variety of modern gold-mediated reactions, often involving strained alkyls.
      PubDate: 2017-11-14T12:41:43.130178-05:
      DOI: 10.1002/chem.201704652
  • Exploiting the σ-Hole Concept: An Infrared and Raman-Based
           Characterization of the S⋅⋅⋅O Chalcogen Bond between
           2,2,4,4-Tetrafluoro-1,3-dithiethane and Dimethyl Ether
    • Authors: Yannick Geboes; Freija De Vleeschouwer, Frank De Proft, Wouter A. Herrebout
      Abstract: In the last decade, halogen bonds, noncovalent interactions formed between positive regions in the electrostatic potential on halogen atoms, often referred to as σ-holes, and electron-rich sites, have gained a lot of interest. Recently, this interest has been expanded towards interactions with Group V and Group VI elements, giving rise to pnicogen and chalcogen bonds. Although chalcogen bonds have already shown some promising results for applications in crystallography and catalysis, experimental results characterising these noncovalent interactions remain scarce. In this combined experimental and theoretical study, original data allowing the characterization of S⋅⋅⋅O chalcogen bonds is obtained by studying the 1:1 molecular complexes between 2,2,4,4-tetrafluoro-1,3-dithiethane (C2F4S2) and dimethyl ether (DME). Ab initio calculations of the C2F4S2⋅DME dimer yield two stable chalcogen-bonded isomers, the difference being the presence or absence of secondary F⋅⋅⋅H interactions. Liquid-krypton solutions containing C2F4S2 and DME were studied using FTIR and Raman spectroscopy. Upon subtraction of rescaled monomer spectra, clear complex bands are observed. The observed complexation shifts agree favourably with the ab initio calculated shifts of the chalcogen-bonded complexes. The 1:1 stoichiometry of the complex is confirmed and a complexation enthalpy of −13.5(1) kJ mol−1 is found, which is in good agreement with the calculated values. A Ziegler–Rauk energy decomposition analysis revealed that electrostatic interactions prominently dominate over orbital interactions. Nevertheless, significant charge transfer occurs from the oxygen in DME to one of the sulfur atoms in C2F4S2 and the carbon along the extension of the chalcogen bond.Holey halogens: The electrostatic potential on the molecular surface of 2,2,4,4-tetrafluoro-1,3-dithiethane shows two positive regions (shown in blue; see figure), so called σ-holes, on either sulfur atom. Through these regions a noncovalent interaction with an electron-rich site can be formed, giving rise to chalcogen-bonded complexes. For the dimer with dimethyl ether, ab initio calculations yield a chalcogen-bonded complex with and without secondary F⋅⋅⋅H interactions.
      PubDate: 2017-11-14T12:41:30.877985-05:
      DOI: 10.1002/chem.201704406
  • Cubane Cross-Coupling and Cubane–Porphyrin Arrays
    • Authors: Stefan S. R. Bernhard; Gemma M. Locke, Shane Plunkett, Alina Meindl, Keith J. Flanagan, Mathias O. Senge
      Abstract: Herein, an improved methodology for aryl-cubane cross-coupling is reported. The peculiarities of the cubane core and its behavior during cross-coupling conditions were analyzed, while the versatility of this adapted Baran cross-coupling methodology was demonstrated by the synthesis of various aryl-cubane systems, including coupling products of cubanes and porphyrins. Furthermore, arm extension of alkynyl-cubanes by Sonogashira reactions is demonstrated, showcasing the first proof of the stability of the cubane core in the presence of palladium catalysts.Alea Iacta Est: The compatibility of cubanes and transition metals (Ni, Pd) was explored, and a direct arylation of cubanes via a Baran-type nickel-catalyzed radical cross-coupling and arm-extended Sonogashira coupling of alkynyl-cubanes is reported. Furthermore, the first series of cubane–porphyrins was prepared (see figure).
      PubDate: 2017-11-14T12:41:26.083637-05:
      DOI: 10.1002/chem.201704344
  • An {As4Cu4[Cu(H2O)]12} Cluster Incorporated within Four [Nb7O22]9−
    • Authors: Li Li; Kaili Dong, Pengtao Ma, Chao Zhang, Jingyang Niu, Jingping Wang
      Abstract: A gigantic 16-copper-containing 28-niobate cluster, Na14K7H5{As4Cu4[Cu(H2O)]12Nb28O109}⋅37.5 H2O (1), has been prepared by a one-pot reaction, which is the first example of arsenic copper clusters containing polyoxoniobate, and the first tetrahedral arrangement of both the Cu cluster and the [Nb7O22]9− subunits.AsCuNb POM: A gigantic 16-copper-containing 28-niobate cluster, Na14K7H5{As4Cu4[Cu(H2O)]12Nb28O109}⋅ 37.5 H2O (1), has been prepared by a one-pot reaction, which is the first example of arsenic copper clusters containing polyoxoniobate.
      PubDate: 2017-11-14T12:41:21.472711-05:
      DOI: 10.1002/chem.201704071
  • Substitution Reactions at DippBIAN Supported Fluoroantimony Cations
           Yielding Cyanoantimony and Azidoantimony Cations
    • Authors: Riccardo Suter; Christopher Frazee, Neil Burford, Robert McDonald, Michael J. Ferguson
      Abstract: This work presents new cationic coordination complexes of antimony with the 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (DippBIAN) ligand system. The fluoroantimony complexes [SbF(DippBIAN)][OTf]2 and [SbF2(DippBIAN)][OTf] have been successfully isolated and characterized. The fluorine substituent in the Lewis acidic complex [SbF(DippBIAN)][OTf]2 can be selectively replaced without degradation of the Sb-DippBIAN interaction to give the first dicationic azido and cyano derivatives, [Sb(CN)(DippBIAN)][OTf]2 and [Sb(N3)(DippBIAN)][OTf]2, which have been isolated and structurally characterized.Cationic cyano- and azido-antimony complexes: A facile synthetic method for the synthesis of functionalized cationic antimony complexes is presented. In the ligand scaffold of DippBIAN, the complexes [SbXDippBIAN][OTf]2 with X=F, CN, N3 were isolated and characterized and depict rare examples of cationic azide and cyanide complexes of antimony.
      PubDate: 2017-11-14T12:41:16.442633-05:
      DOI: 10.1002/chem.201703951
  • The Complex Solid-State Landscape of Sodium Diatrizoate Hydrates
    • Authors: Mohd Nadzri Mohd Najib; Kevin Back, Katharina Edkins
      Abstract: Pharmaceutical sodium salts are prone to incorporate water into their crystal structures. The model compound diatrizoic acid monosodium salt, an X-ray contrast agent, has been investigated in depth towards its interaction with water in the solid state. Five hydrates with water content ranging from 0.3 to 8 molar equivalents of water show a high degree of interconvertibility, stoichiometric and non-stoichiometric behaviour, and potential of amorphisation during release of water. A DMSO/water mixed solvate further highlights the high attraction of this salt to incorporate water. All incorporated solvent coordinates to the sodium cation and can further interact and stabilise the respective crystal forms by hydrogen bonding. DTS thus highlights the importance of an in-depth investigation of sodium salts used pharmaceutically to guarantee dose uniformity and stability of final formulation.The pharmaceutical X-ray contrast agent diatrizoic acid sodium salt can exist in at least five hydrated crystal forms containing between 0.3 and 8 molar equivalents of water. The hydrates interconvert depending on the relative humidity. Of the two found solvates, one contains water in addition to DMSO. This compound is a valuable model for water affinity of sodium salts in the solid state.
      PubDate: 2017-11-14T12:41:12.596971-05:
      DOI: 10.1002/chem.201703658
  • Functionalized Ultrasmall Fluorinated Graphene with High NIR Absorbance
           for Controlled Delivery of Mixed Anticancer Drugs
    • Authors: Peiwei Gong; Qiao Zhao, Dujuan Dai, Shumiao Zhang, Zhenzhen Tian, Lu Sun, Jiashuo Ren, Zhe Liu
      Abstract: Fluorinated graphene (FG) possess distinctively novel properties different from graphene and is suitable for many biomedical applications. However, the hydrophobic nature and inert properties of FG limit its further application as a biological material. Here we show the preparation of nano-sized FG (ca. 60 nm) that exhibits high NIR absorbance for photothermal therapy. In order to make it stable in physiological solutions, the FG is enriched with oxygen and followed by covalent binding with chitosan as a novel pH-responsive nanocarrier. Furthermore, controlled loading of two anticancer drugs, doxorubicin (DOX) and camptothecin (CPT) has been realized and the functionalized ultrasmall FG shows remarkably high cytotoxicity toward Hela cancer cells compared to that loaded with either CPT or DOX only. This work established nano-sized FG as a novel photothermal agent due to its small size and can be used a stimulus-responsive nanocarrier for mixed drug delivery and combined therapy.Stimuli-responsive ultrasmall fluorinated graphene with high NIR absorbance for controlled delivery of mixed anticancer drugs was constructed, and its first application as a synergistic chemo-photothermal system that exhibits good therapeutic efficacy is reported (see scheme).
      PubDate: 2017-11-14T12:41:03.915541-05:
      DOI: 10.1002/chem.201702917
  • [(CH3)3NH]3Bi2I9: A Polar Lead-Free Hybrid Perovskite-Like Material as a
           Potential Semiconducting Absorber
    • Authors: Jing Zhang; Shiguo Han, Chengmin Ji, Weichuan Zhang, Yuyin Wang, Kewen Tao, Zhihua Sun, Junhua Luo
      Abstract: Perovskite hybrids of lead organometal halides, most notably CH3NH3PbI3, have shown extremely promising applications in the field of optoelectronics, because of their remarkable semiconducting and light-absorbing properties. However, two key issues—the toxicity of lead and the poor ambient instabilities—have restrained their further commercialization. Herein, we have designed a new stable polar lead-free hybrid material by utilizing the strategy of cation substitution, [(CH3)3N]3Bi2I9 (1), which adopts the 0D inorganic perovskite-like architecture by face-sharing BiI6 octahedra. It is interesting that 1 displays excellent absorbing properties with a narrow optical band gap of ≈2.0 eV, and positive temperature-dependent conductivity confirms its semiconducting behaviors. In addition, 1 has good phase stability against decomposition under ambient conditions, much superior to that of CH3NH3PbI3. This work suggests the potential of 1 as a lead-free semiconducting absorber with high phase stability for photoelectric applications.Semiconductors: A new stable polar lead-free hybrid material has been designed by utilizing the strategy of cation substitution, [(CH3)3N]3Bi2I9 (1), which displays excellent absorbing properties with an optical band gap of ≈2.0 eV and positive temperature-dependent conductivity (see figure).
      PubDate: 2017-11-14T12:40:52.102812-05:
      DOI: 10.1002/chem.201703346
  • Tuning the Förster Resonance Energy Transfer through Self-assembly
           Approach for Efficient White-light Emission in Aqueous Medium
    • Authors: Pragyan Pallavi; Bahadur Sk, Palak Ahir, Abhijit Patra
      Abstract: A simple and cost-effective methodology employing environmentally benign substances for the fabrication of white-light emitting materials is important for practical applications in the field of lighting and display devices. Designing of purely organic-based white-light emitting system with high quantum efficiency in the aqueous medium is an unmet challenge. With this objective, a new class of pyridoindole based hydrophobic fluorophore 6,7,8,9-tetrapropylpyrido[1,2-a]indole-10-carbaldehye (TPIC) was introduced. A strategy of self-organized assembly using nonionic surfactants was employed to enhance the fluorescence of TPIC in an aqueous medium and was exploited as energy donor. The steady-state and time-resolved emission spectra analysis revealed the micelle-mediated energy transfer from TPIC to Nile red (energy acceptor) leading to tunable fluorescence along with white-light emission. The white-light emitting aqueous solution was obtained with the Commission Internationale de lEclairage (CIE) chromaticity coordinates of (0.33, 0.36) and significantly high quantum yield of 37%. Solid-state white-light emission was achieved retaining the assembly of fluorophores in the form of a gel having the high quantum efficiency of 33% with CIE (0.32, 0.36) close to that of pure white light. The bright white luminescence of the inscription prepared using white-light emitting gel on a solid substrate offers promising applications for full-color flat panel displays.
      PubDate: 2017-11-14T09:51:06.846581-05:
      DOI: 10.1002/chem.201704437
  • Reversible Polymerization of Adamantane-type [P4N10]10− Anions to
           Honeycomb-type [P2N5]5− Layers under High-Pressure
    • Authors: Eva-Maria Bertschler; Robin Niklaus, Wolfgang Schnick
      Abstract: The high-pressure polymorph Li5P2N5 of Li10P4N10 (= "2 Li5P2N5") was synthesized by high-pressure/high-temperature reaction of LiPN2 and Li7PN4 or beta-Li10P4N10 at 9 GPa, using the Li3N self-flux method in a Walker-type multianvil assembly. Li5P2N5 is the first lithium nitridophosphate with a layered structure and is made up of corner sharing PN4 tetrahedra forming a corrugated honeycomb-type layer of linked sechser-rings in chair conformation. The arrangement of the P atoms is analogous to that of black phosphorus. The structure was elucidated from single-crystal X-ray data. To confirm the structure Rietveld refinement, 6Li, 7Li and 31P solid-state NMR spectroscopy were conducted. To corroborate Li5P2N5 as the corresponding high-pressure polymorph of beta-Li10P4N10 DFT calculations and temperature dependent X-ray powder diffraction were carried out. DFT calculations estimated the transition pressure to 6.5 GPa (without accounting for temperature), which is in line with the synthesis pressure.
      PubDate: 2017-11-14T09:50:49.729138-05:
      DOI: 10.1002/chem.201704975
  • An Alkynyl-stabilized Pt₅Ag₂₂ Cluster Featuring Two-Dimensional
           Alkynyl-Platinum "Crucifix Motif"
    • Authors: Hui Shen; Tsutomu Mizuta
      Abstract: The "staple motif" has been widely applied to depict and predict the structures of thiolate or alkynyl-protected gold nanoclusters. By contrast, the composition, dimensions, configuration, and functionality of the platinum-ligand motif has remained completely unknown. Herein, we report the synthesis and crystal structure of a novel luminescent Pt₅Ag₂₂(C≡CPh)₃₂ (1) cluster, in which two-dimensional and two-functional alkynyl-platinum "crucifix motif" was observed. Such a crucifix motif with one Pt center and four alkynyl groups in the same plane acts as a two-dimensional unit in the cluster and functions as both a protective cover and an intermediate joint.
      PubDate: 2017-11-14T07:20:54.430921-05:
      DOI: 10.1002/chem.201704643
  • Direct Arylation of Dipyrrolonaphthyridinediones Leads to Red-Emitting
           Dyes with Conformational Freedom
    • Authors: Bartłomiej Sadowski; Michał F. Rode, Daniel T. Gryko
      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
  • Metal-Containing Polymers as Light-Emitting and Light-Responsive Materials
           and Beyond
    • Authors: Matteo Mauro; Stéphane Bellemin-Laponnaz, Cristina Cebrián
      Abstract: Functional materials that respond to external stimuli are of major current interest. In particular, supramolecular systems that can interact with their surroundings, adapt to environmental changes and evolve with are even more fascinating, yet challenging. Combining the rich physico-chemical properties featured by metal centres with characteristics typical of classical organic polymers, metallopolymers or metallo-supramolecular polymers can be prepared, depending on their static versus dynamic structural features. Additionally, multiple and orthogonal functionalities can be encoded in their chemical structure affording materials with widespread potential applications to be employed as “smart” materials for advanced technologies. In this Concept article, selected examples of metal-containing polymers will be described demonstrating large potentialities of such systems for creating stimuli-responsive materials with special emphasis for those showing optical applications.Functional materials that respond to external stimuli are of major current interest. Supramolecular systems that can interact with their surroundings, adapt to the environmental changes and evolve with are even more fascinating, yet challenging. A judicious combination of multi-topic organic ligands with metal centres affords functional and light-responsive metal-containing polymers that possess widespread potential application.
      PubDate: 2017-11-14T03:05:44.678734-05:
      DOI: 10.1002/chem.201702936
  • Achieving High 1H Nuclear Hyperpolarization Levels with Long Lifetimes in
           a Range of Tuberculosis Drug Scaffolds
    • Authors: Philip Norcott; Peter J. Rayner, Gary G. R. Green, Simon B. Duckett
      Abstract: Despite the successful use of isoniazid, rifampicin, pyrazinamide and ethambutol in the treatment of tuberculosis (TB), it is a disease of growing global concern. We illustrate here a series of methods that will dramatically improve the magnetic resonance imaging (MRI) detectability of nineteen TB-relevant agents. We note that the future probing of their uptake and distribution in vivo would be expected to significantly enhance their efficacy in disease treatment. This improvement in detectability is achieved by use of the parahydrogen based SABRE protocol in conjunction with the 2H-labelling of key sites within their molecular structures and the 2H-labelling of the magnetization transfer catalyst. The T1 relaxation times and polarization levels of these agents are quantified under test conditions to produce a protocol to identify structurally optimized motifs for future detection. For example, deuteration of the 6-position of a pyrazinamide analogue leads to a structural form that exhibits T1 values of 144.5 s for 5-H with up to 20 % polarization. This represents a>7-fold extension in relaxation time and almost 10-fold improvement in polarization level when compared to its unoptimized structure.The tuberculosis drugs, pyrazinamide, isoniazid and their derivatives have been optimally hyperpolarized using SABRE. Through 2H-labelling the drugs and catalysts T1 lifetimes of over two minutes and ≈20 % polarization have been achieved which opens the door to in vivo assessment.
      PubDate: 2017-11-14T02:51:30.902976-05:
      DOI: 10.1002/chem.201703278
  • Synthesis of Size-Tunable Hollow Polypyrrole Nanostructures and Their
           Assembly into Folate-Targeting and pH-Responsive Anticancer Drug-Delivery
    • Authors: Jian Chen; Xiufang Li, Yanhua Sun, Yuwei Hu, Yulong Peng, Yimin Li, Gang Yin, Hui Liu, Jiangfeng Xu, Shian Zhong
      Abstract: Chemotherapeutic drugs currently used in clinical settings have high toxicity, low specificity, and short half-lives. Herein, polypyrrole-based anticancer drug nanocapsules were prepared by tailoring the size of the nanoparticles with a template method, controlling drug release by means of an aromatic imine, increasing nanoparticle stability through PEGylation, and improving tumor-cell selectivity by folate mediation. The nanoparticles were characterized by TEM and dynamic light scattering. α-Folate receptor expression levelsof tumor cells and normal cells were investigated by western blot and quantitative polymerase chain reaction analyses. Flow cytometry and fluorescence imaging were used to verify the cell uptake of the different-sized nanoparticles. From the different-sized polypyrrole nanoparticles, the optimally functionalized nanoparticles of 180 nm hydrodynamic diameter were chosen and further usedfor in vitroandin vivotests. The nanoparticles showed excellent biocompatibility and the drug-loaded nanoparticles exhibited effective inhibition of tumor cell growth in vitro. Moreover, the drug-loaded nanoparticles showed substantially enhanced accumulation in tumor regions and effectively inhibitedin vivotumor growth. Furthermore, the nanoparticles showed reduced doxorubicin-induced toxicity andno significant side effects in normal organs of tumor-bearing mice, as measured by body-weight shifts and evaluationof drug distribution. Overall, the functionalized nanoparticles are promising nanocarriers for tumor-targeting drug delivery.Anticancer nanocapsules: By using a template method, polypyrrole (PPy)@tetra-arm aldehyde (TAA)@polyethylene glycol (PEG)@folate (FA) nanoparticle drug carriers were synthesized (see figure). In vitro cytotoxicity assays showed that doxorubicin (Dox)-loaded PPy@TAA@PEG@FA nanoparticles induced death of Skov3 tumor cells, and in vivo studies demonstrated that Dox/PPy@TAA@PEG@FA nanoparticles exhibited higher antitumor activity than free Dox (see scheme).
      PubDate: 2017-11-14T02:51:21.33428-05:0
      DOI: 10.1002/chem.201702945
  • Radical Behavior of CO2 versus its Deoxygenation Promoted by Vanadium
           Aryloxide Complexes: How the Geometry of Intermediate CO2-Adducts
           Determines the Reactivity.
    • Authors: Camilo J. Viasus; Nicholas P. Alderman, Sebastiano Licciulli, Ilia Korobkov, Sandro Gambarotta
      Abstract: The reactivity of carbon dioxide with vanadium(III) aryloxo complexes has been investigated. The formation of either carbon monoxide or incorporation into the ligand system with the ultimate formation of organic ester was observed depending on the overall electron donor ability of the ligand field. DFT calculations were carried out to investigate the proposed mechanism for carbon dioxide coordination and reduction.It′s complex: The extent of charge transfer from vanadium to CO2 determines the type of coordination and ultimately the type of reactivity
      PubDate: 2017-11-14T02:50:44.98058-05:0
      DOI: 10.1002/chem.201702943
  • The Intermetalloid Cluster Cation (CuBi8)3+
    • Authors: Maximilian Knies; Martin Kaiser, Anna Isaeva, Ulrike Müller, Thomas Doert, Michael Ruck
      Abstract: Invited for the cover of this issue is the group of Michael Ruck at the Technical University in Dresden. The image depicts the intermetalloid cluster (CuBi8)3+, which features a hitherto unknown bonding mode between bismuth and copper, and crystallizes as an adduct with an [AlCl4]− ion of the applied ionic liquid. Read the full text of the article at 10.1002/chem.201703916.“We were curious whether the special solvent properties of ILs allow for combining two elements that do not form binary compounds.” Read more about the story behind the cover in the Cover Profile and about the research itself on page ▪▪ ff. (
      DOI : 10.1002/chem.201703916).
      PubDate: 2017-11-14T02:47:11.854734-05:
  • The Intermetalloid Cluster Cation (CuBi8)3+
    • Authors: Maximilian Knies; Martin Kaiser, Anna Isaeva, Ulrike Müller, Thomas Doert, Michael Ruck
      Abstract: The intermetalloid cluster (CuBi8)3+ combines two elements that usually avoid mutual bonding. It forms from bismuth, BiCl3, and CuCl under ionothermal conditions in a Lewis acidic ionic liquid that contains an excess of AlCl3. One of the [AlCl4]− counterions directly coordinates to the copper atom. The multicenter bonding in the (CuBi8)3+ cage, revealed by quantum-chemical analysis, matches its description as a heterometallic nido-Wade-cluster. More information can be found in the Full Paper by M. Ruck et al. (
      DOI : 10.1002/chem.201703916).
      PubDate: 2017-11-14T02:47:03.365007-05:
  • One-Step Assembly of Visible and Near-Infrared Emitting Metallacrown
           Dimers Using a Bifunctional Linker
    • Authors: Tu N. Nguyen; Chun Y. Chow, Svetlana V. Eliseeva, Evan R. Trivedi, Jeff W. Kampf, Ivana Martinić, Stéphane Petoud, Vincent L. Pecoraro
      Abstract: GaIII/LnIII metallacrown (MC) complexes with a dimeric structure have been designed, synthesized and characterized. The presence of the bridge in the [LnGa4]2 allows for a broad variety of functionalization with chemical groups of different nature through carboxylate substitution. Moreover, the MC scaffold in [LnGa4]2 is able to efficiently sensitize the characteristic emission of Nd, Pr, Sm, Tb, Dy, Ho, Er and Yb ions in the visible and/or NIR ranges in the solid state. More information can be found in the Communication by S. V. Eliseeva, S. Petoud, V. L Pecoraro et al. (
      DOI : 10.1002/chem.201703911).
      PubDate: 2017-11-14T02:46:52.608979-05:
  • New Architectures for Designed Catalysts: Selective Oxidation using AgAu
           Nanoparticles on Colloid-Templated Silica
    • Authors: Tanya Shirman; Judith Lattimer, Mathilde Luneau, Elijah Shirman, Christian Reece, Michael Aizenberg, Robert J. Madix, Joanna Aizenberg, Cynthia M. Friend
      Abstract: A highly modular synthesis of designed catalysts with controlled bimetallic nanoparticle size and composition and a well-defined structural hierarchy is demonstrated. Exemplary catalysts—bimetallic dilute Ag-in-Au nanoparticles partially embedded in a porous SiO2 matrix (SiO2–AgxAuy)—were synthesized by the decoration of polymeric colloids with the bimetallic nanoparticles followed by assembly into a colloidal crystal backfilled with the matrix precursor and subsequent removal of the polymeric template. This work reports that these new catalyst architectures are significantly better than nanoporous dilute AgAu alloy catalysts (nanoporous Ag3Au97) while retaining a clear predictive relationship between their surface reactivity with that of single-crystal Au surfaces. This paves the way for broadening the range of new catalyst architectures required for translating the designed principles developed under controlled conditions to designed catalysts under operating conditions for highly selective coupling of alcohols to form esters. Excellent catalytic performance of the porous SiO2–AgxAuy structure for selective oxidation of both methanol and ethanol to produce esters with high conversion efficiency, selectivity, and stability was demonstrated, illustrating the ability to translate design principles developed for support-free materials to the colloid-templated structures. The synthetic methodology reported is customizable for the design of a wide range of robust catalytic systems inspired by design principles derived from model studies. Fine control over the composition, morphology, size, distribution, and availability of the supported nanoparticles was demonstrated.Colloid-templated porous silica embedded with AgAu bimetallic nanoparticles was utilized for the selective oxidation of methanol to methyl formate. This system demonstrated high conversion efficiency, selectivity, stability, and reproducibility. The modularity of the synthesis establishes a platform for making and testing rationally designed catalysts.
      PubDate: 2017-11-14T02:46:46.126034-05:
      DOI: 10.1002/chem.201704552
  • Catalytic Carbon–Chlorine Bond Activation by Selenium-Based
           Chalcogen Bond Donors
    • Authors: Patrick Wonner; Lukas Vogel, Florian Kniep, Stefan M. Huber
      Abstract: Chalcogen bonding is a noncovalent interaction based on electrophilic chalcogen substituents, which shares many similarities with the more well-known hydrogen and halogen bonding. Herein, the first application of selenium-based chalcogen bond donors in organocatalysis is described. Cationic bifunctionalized organoselenium compounds activate the carbon–chlorine bond of 1-chloroisochroman in a benchmark reaction. While imidazolium-based derivatives showed no noticeable activation, benzimidazolium backbones yielded potent catalysts. In all cases, syn-isomers were markedly more active, presumably due to bidentate coordination, which was confirmed by DFT calculations. Comparison experiments with the corresponding non-selenated as well as the non-cationic reference compounds clearly indicate that the catalytic activity can be ascribed to chalcogen bonding. The rate acceleration by the catalyst—compared to the non-selenated derivative—was about 10 fold.The first application of selenium-based chalcogen bond donors in organocatalysis is described. Cationic bifunctionalized organoselenium compounds activate the carbon–chlorine bond of 1-chloroisochroman in a benchmark reaction. Several comparison experiments clearly indicate that the catalytic activity can be ascribed to chalcogen bonding.
      PubDate: 2017-11-14T02:46:39.221477-05:
      DOI: 10.1002/chem.201704502
  • Enzyme-Free Colorimetric Detection of Cu2+ by Utilizing Target-Triggered
           DNAzymes and Toehold-Mediated DNA Strand Displacement Events
    • Authors: Yeonkyung Park; Chang Yeol Lee, Ki Soo Park, Hyun Gyu Park
      Abstract: A new enzyme-free system for colorimetric Cu2+ detection, which relies on target-triggered DNAzymes and toehold-mediated DNA strand-displacement circuits, is described. The system employs a DNAzyme designed to undergo self-cleavage in the presence of Cu2+ and release a catalyst strand that triggers a sequential toehold-mediated strand displacement reaction. This event leads to the release of a split G-quadruplex DNAzyme strand that is initially caged and inactivated by a blocker strand. A fuel strand is further incorporated for the recycling of the catalyst strand to promote another toehold-mediated strand displacement event, which consequently produces a large number of active split G-quadruplex DNAzymes. By employing this design principle, target Cu2+ was very successfully identified with a detection limit of 1.31 nm based on the distinct colorimetric signal developed by the oxidation of 2,2′-azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid promoted by the peroxidase mimicking activity of the released G-quadruplex DNAzymes. Finally, the practical capability of this sensing system was very successfully demonstrated by its use to reliably determine Cu2+ in tap water.Copper-induced cleavage: A new enzyme-free system for colorimetric Cu2+ detection, which relies on target-triggered DNAzymes and a toehold-mediated DNA strand displacement circuit, is described (see figure). With this system, Cu2+ is successfully identified in tap water with a detection limit of 1.31 nm.
      PubDate: 2017-11-14T02:46:34.448784-05:
      DOI: 10.1002/chem.201704346
  • CaB2S4O16: A Borosulfate Exhibiting a New Structure Type with
           Phyllosilicate Analogue Topology
    • Authors: Jörn Bruns; Maren Podewitz, Michael Schauperl, Bastian Joachim, Klaus R. Liedl, Hubert Huppertz
      Abstract: The reaction of Ca(CO3) with H3BO3 in oleum (20 % SO3) yielded colorless single-crystals of CaB2S4O16 (monoclinic, P21/c, a=5.5188(2), b=15.1288(6), c=13.2660(6) Å, β=92.88(1)°, V=1106.22(8) Å3). X-ray single-crystal structure analysis revealed a phyllosilicate-analogue anionic sub-structure, forming 2D infinite anionic layers, which exhibit an unprecedented arrangement of condensed twelve-membered (zwölfer) and four-membered (vierer) rings of corner-shared (SO4) and (BO4) tetrahedra. Charge compensation is achieved by Ca2+ cations, residing exclusively above the centers of the twelve-membered rings. DFT investigations on the solid-state structure corroborate the experimental findings and allow for a detailed valuation of charge distribution within the anionic network and an assignment of vibrational frequencies.Ring up: The reaction of calcium carbonate with oleum (20 % SO3) leads to colorless crystals of CaB2S4O16. The crystal structure reveals a network of corner linked (SO4) and (BO4) tetrahedra with an unprecedented phyllosilicate analogue structure with directly adjacent zwölfer and vierer rings. DFT investigations on the solid-state structure allow for a detailed evaluation of charge distribution within the anionic network, and an assignment of experimental vibrational frequencies.
      PubDate: 2017-11-14T02:46:30.335286-05:
      DOI: 10.1002/chem.201704228
  • Copper-Mediated Introduction of the CF2PO(OEt)2 Motif: Scope and
    • Authors: Maria V. Ivanova; Alexandre Bayle, Tatiana Besset, Xavier Pannecoucke, Thomas Poisson
      Abstract: Herein, a general procedure to access CF2PO(OEt)2-containing molecules is reported. The reagent CuCF2PO(OEt)2 is accessible by a simple protocol and a broad range of substrates can be functionalised. The procedure allows the conversion of aryl diazonium salts, as well as aryl, heteroaryl, vinyl and alkynyl iodonium salts, into the corresponding fluorinated molecules at room temperature. Mechanistic studies were performed to gain a better understanding of the reaction pathway. Under similar conditions, vinyl and aryl iodides, allyl halides, and benzyl bromides were also functionalised, and the scope and limitations of the reaction were studied. Finally, the procedure was extended to disulfides to offer new access to SCF2PO(OEt)2-containing molecules.Upgrading reagents: A straightforward procedure to prepare the CuCF2PO(OEt)2 reagent from a readily available silylated precursor is reported. This reagent is used to functionalise aryl diazonium salts, aryl, heteroaryl, vinyl and alkynyl iodoniums salts (see scheme). The protocol was applied to the synthesis of bio-relevant molecules.
      PubDate: 2017-11-14T02:46:21.263618-05:
      DOI: 10.1002/chem.201703542
  • A Reusable N-Doped-Carbon-Coated Mo2C Composite Counter Electrode for
           High-Efficiency Dye-Sensitized Solar Cells
    • Authors: Ting Wang; Jiabo Wang, Weilin Chen, Xiaotao Zheng, Enbo Wang
      Abstract: The design and development of efficient and stable nonprecious-metal-based catalysts for counter electrodes (CEs) in dye-sensitized solar cells (DSSCs) has received a great deal of attention. In this work, molybdenum carbide nanoparticles homogeneously distributed in a nitrogen-rich carbon matrix (Mo2C@NC) have been synthesized from inexpensive raw materials (polyoxometalate and dicyandiamide) by a facile one-step solid-phase synthesis method. The novel Mo2C@NC hybrid was not only used as a CE in a DSSC, but also showed superior catalytic activity towards I3−/I− as a redox electrolyte. The power conversion efficiency of a DSSC with Mo2C@NC as the CE was as high as 6.49 %, comparable to that with Pt (6.38 %). The CE was prepared by a drop-coating method, without the addition of another conductive polymer. Most importantly, the method circumvents the problem of the sample falling off from the fluorine-doped tin oxide (FTO), and the CE could be repeatedly reused with unchanged efficiency. Therefore, it opens the way for the development of platinum-free catalysts with low cost, simple processing, good stability, and high efficiency.Pt-free electrode material: A polyoxometalate and dicyandiamide have been heated at high temperature to obtain highly dispersed Mo2C nanoparticles. The obtained material can serve as an alternative to Pt to assemble a reusable counter electrode for high-efficiency dye-sensitized solar cells (see figure).
      PubDate: 2017-11-14T02:46:00.677095-05:
      DOI: 10.1002/chem.201703519
  • Modulating the Physical and Electronic Properties over Positional
           Isomerism: The Dispirofluorene–Dihydroindacenodithiophene (DSF-IDT)
    • Authors: Jean-David Peltier; Benoît Heinrich, Bertrand Donnio, Olivier Jeannin, Joëlle Rault-Berthelot, Cyril Poriel
      Abstract: We report the first studies on the intrinsic properties of a meta-substituted dihydroindacenodithienyl fragment and more generally the strong impact of positional isomerism on dihydroindacenodithiophene derivatives. The influence of the para and meta linkages has notably been highlighted not only for the electronic properties in solution (electrochemical properties, anodic polymerization, HOMO/LUMO energy levels, optical transitions, fluorescence spectra) but also on the physical properties in the solid state (molecular organization, crystallinity, and phase transitions). The positional isomerism hence appears to be a very efficient tool to drastically tune the properties of dihydroindacenodithiophene derivatives.What's the best position' The intrinsic properties of a meta-substituted dihydroindacenodithienyl fragment and more generally the strong impact of positional isomerism on dihydroindacenodithiophene derivatives is reported. The influence of the para and meta linkages has notably been highlighted not only on the electronic properties in solution, but also on the physical properties in the solid state. The positional isomerism hence appears as a very efficient tool to drastically tune the properties of dihydroindacenodithiophene derivatives.
      PubDate: 2017-11-14T02:45:54.250954-05:
      DOI: 10.1002/chem.201703320
  • Diastereomeric Right- and Left-Handed Helical Structures with Fourteen
           (R)-Chiral Centers
    • Authors: Ryo Eto; Makoto Oba, Atsushi Ueda, Tsubasa Uku, Mitsunobu Doi, Yosuke Matsuo, Takashi Tanaka, Yosuke Demizu, Masaaki Kurihara, Masakazu Tanaka
      Abstract: The relationship between chiral centers and the helical-screw control of their peptides has already been reported, but it has yet to be elucidated in detail. A chiral four-membered ring α,α-disubstituted α-amino acid with a (R,R)-butane-2,3-diol acetal moiety at the γ-position, but no α-chiral carbon, was synthesized. X-ray crystallographic analysis unambiguously revealed that its homo-chiral heptapeptide formed right-handed (P) and left-handed (M) 310-helical structures at a ratio of 1 to 1. They appeared to be enantiomeric at the peptide backbone, but diastereomeric with fourteen (R)-configuration chiral centers. Conformational analyses of homopeptides in solution also indicated that diastereomeric (P) and (M) helices existed at approximately equal amounts, with a slight preference toward right-handedness, and they quickly interchanged at room temperature. The circumstances of chiral centers are important for the control of their helical-screw direction.
      PubDate: 2017-11-13T23:51:09.062284-05:
      DOI: 10.1002/chem.201705306
  • Directed Rh(I)-Catalyzed Asymmetric Hydroboration of Prochiral
           1-Arylcycloprop-2-ene-1-carboxylic Acid Derivatives
    • Authors: Andrew Edwards; Michael Rubin, Marina Rubina
      Abstract: A full account on rhodium-catalyzed asymmetric, directed hydroboration of functionalized prochiral cyclopropenes affording enantiomerically enriched cyclopropylboronates is reported. The scope and limitations of two alternate directing groups, ester and carboxamide, are evaluated. It was found that hydroboration of esters appeared to be more sensitive to substitution in the aromatic ring of the substrates. Specifically, ortho-halogens were detrimental for diastereo- and enantioselectivity, potentially, due to additional coordination with rhodium. In contrast, more Lewis-basic amide directing groups allowed for stronger chelation to the transition metal, leading to consistently high diastereo- and enantioselectivity in hydroboration across a broader range of substrates.
      PubDate: 2017-11-13T21:56:04.962837-05:
      DOI: 10.1002/chem.201704443
  • Imprinted naked Pt nanoparticles on N-doped carbon supports: A synergistic
           effect between catalyst and support
    • Authors: Jairton Dupont; Gustavo R. Bolzan, Gabriel Abarca, Wellington D. G. Gonçalves, Carolona F. Matos, Marcos J. L. Santos
      Abstract: A synergistic effect resulting from the interaction of small (2.4-3.1 nm) naked Pt nanoparticles (NPs) imprinted on N-doped carbon supports is evidenced by structural, electronic and electrochemical characterization. The size and distribution of the sputtered Pt NPs are found to be related to the nature of the support, as Pt NPs are preferentially located at Ngraphitic sites. In addition, Rutherford backscattering shows that a deeper penetration of the Pt NPs is obtained in the N-doped carbon support with larger pore diameters. The ligand effect of the N-doped carbon supports is found to occur by electron donation from Npyrrolic and Ngraphitic sites to the Pt NPs and the electron acceptor behaviour of the C=Npyridinic sites. The carbon matrix acquires a basic characteristic (electron-richer, metallic behaviour) capable of interacting with metallic NPs akin to a bimetallic-like system. The imprinted Pt NPs are active catalysts for oxidation, while displaying poor catalytic activity for reduction reactions. The catalyst N-doped carbon supports play an important role in the overall catalytic process, rather than only acting as a simple active phase carrier.
      PubDate: 2017-11-13T14:34:22.332663-05:
      DOI: 10.1002/chem.201704094
  • Redox-dependent metal-metal bonding in trinuclear metal chains: probing
           the transition from covalent bonding to exchange coupling.
    • Authors: John Ewart McGrady; Nicholas Perkins, Mohammed Obies, Graham Heath, Alison Edwards, Vaida Arcisauskaite
      Abstract: We report here the synthesis and physical properties of two new cationic tri-metallic chains, [(PEt3)3RuCl3M'Cl3Ru(PEt3)3]1+, M' = Rh and Ir. These are isostructural with a previously reported 17-electron all-ruthenium analogue, but the switch from an open-shell d5 Ru3+ ion to d6 Rh3+/Ir3+ in the central position has profound impact on the nature of the metal-metal bonding. X-ray crystallography and spectro-electrochemistry, complemented by electronic structure analysis at the DFT and CASSCF levels, indicate that whilst the presence of a Ru3+ ion in the center of the chain allows multi-center covalent bonding to develop, a closed-shell Rh3+/Ir3+ ion pushes the system towards the exchange-coupled limit, where the terminal Ru centers are only weakly interacting. This family of three isostructural compounds highlights how subtle changes in composition can have subtle effects on physical properties of systems that lie closed to the localized/delocalized borderline.
      PubDate: 2017-11-13T12:50:24.061216-05:
      DOI: 10.1002/chem.201704727
  • 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 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 pHs) 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 bisgold complex is a key reaction intermediate. Furthermore, both experimental and computational studies confirmed that the σ,π-bisgold complexes are not active intermediate toward nucleophilic addition. Instead, formation of geminally diaurated complex C is crucial for this catalytic process.
      PubDate: 2017-11-13T12:20:37.09768-05:0
      DOI: 10.1002/chem.201703666
  • Oxidation of Polynuclear Aromatic Hydrocarbons using Ruthenium Ion
           Catalyzed Oxidation: The role of aromatic ring number in reaction kinetics
           and product distribution
    • Authors: Stuart H. Taylor; Ewa Nowicka, Tomos Clarke, Meenakshisundaram Sankar, Robert Jenkins, David Knight, Stanislaw Golunski, Graham Hutchings, David Willock, Manuel Francisco
      Abstract: Oxidation of aromatic hydrocarbons with differing numbers of fused aromatic rings (2-5), have been studied in two solvents environments (monophasic and biphasic) using ruthenium ion catalyzed oxidation (RICO). RICO reduces the aromaticity of the polyaromatic core of the molecule in a controlled manner by selective oxidative ring opening. Moreover, the nature of the solvent system determines the product type and distribution, for molecules with more than 2 aromatic rings. Competitive oxidation between substrates with different numbers of aromatic rings has been studied in detail. It was found that the rate of polyaromatic hydrocarbon oxidation increases with the number of fused aromatic rings. A similar trend was also identified for alkylated aromatic hydrocarbons. The proof-of-concept investigation provides new insight into selective oxidation chemistry for upgrading of polyaromatic molecules.
      PubDate: 2017-11-13T11:15:31.581912-05:
      DOI: 10.1002/chem.201704133
  • Synthesis of fucosylated chondroitin sulfate glycoclusters: a robust route
           to novel anticoagulant agents
    • Authors: Xiao Zhang; Wang Yao, Xiaojiang Xu, Huifang Sun, Jinhua Zhao, Xiangbao Meng, Mingyi Wu, Zhongjun Li
      Abstract: Fucosylated chondroitin sulfate (FuCS) is a structurally distinct glycosaminoglycan with excellent anticoagulant activity. Studies show that FuCS and its depolymerized fragments exhibit different anticoagulant mechanism from heparin derivatives, with decreased risks of adverse effects and bleeding. However, further exploitation has been hindered by the scarcity of structurally defined oligosaccharides. Herein we report a facile method to synthesize the repeating trisaccharide unit of FuCS based on the degradation of chondroitin sulfate polymers. A series of simplified FuCS glycomimetics that have highly tunable structures, controllable branches, and defined sulfation motifs were generated by CuAAC. Remarkable improvement in APTT assay activities was observed as the branches increased, while no significant influences were observed for PT and TT assay activities. Further FXase inhibition tests suggested glycoclusters 33b~40b selectively inhibited intrinsic anticoagulant activities while showed little effect on the extrinsic and common coagulation pathways. Notably, glycoclusters bearing 2,4-di-O-sulfated Fuc residue displayed the most potency, which was in consistent with natural polysaccharides. These FuCS clusters demonstrated potency to mimic linear glycosaminoglycans and offer a new framework for the development of novel anticoagulant agents.
      PubDate: 2017-11-13T07:15:30.300982-05:
      DOI: 10.1002/chem.201705177
  • Rh-catalyzed Denitrogenative Reaction of N-Sulfonyl-1,2,3-triazoles with
           Isatoic Anhydrides and Oxadiazolones
    • Authors: Chandra M.R Volla; Kuntal Pal, Abdul Hoque
      Abstract: A convenient and simple, Rh(II)-catalyzed denitrogenative methodology for the synthesis of biologically interesting 2-amino-benzoxazinones and 5-amino-oxadiazoles from readily available isatoic anhydrides and oxadiazolones has been developed. These reactions proceed via an O-H insertion onto α-imino Rh(II)-carbenoid species followed by a rearrangement. The scope of the reaction can also be extended to benzoxazinones to access amino-substituted benzoxazines.
      PubDate: 2017-11-13T06:50:46.085923-05:
      DOI: 10.1002/chem.201705036
  • Dichromatic Photocatalytic Substitutions of Aryl Halides with a Small
           Organic Dye
    • Authors: Axel Jacobi von Wangelin; Michael Neumeier, Raul Perez, Michal Majek, Diego Sampedro, Victor de la Pena O'Shea
      Abstract: Photocatalytic bond activations are generally limited by the photon energy and the efficiency of energy and electron transfer processes. Direct two-photon processes provide sufficient energy but the ultra-short lifetimes of the excited states prohibit chemical reactions. The commercial dye 9,10-dicyanoanthracene enabled photocatalytic aromatic substitutions of non-activated aryl halides. This reaction operates under VIS irradiation via sequential photonic, electronic, and photonic activation of the simple organic dye. The resultant highly reducing excited photocatalyst anion readily effected C-H, C-C, C-P, C-S, and C-B bond formations. Detailed synthetic, spectroscopic, and theoretical studies support a biphotonic catalytic mechanism.
      PubDate: 2017-11-13T05:50:43.361156-05:
      DOI: 10.1002/chem.201705326
  • Control of enantioselectivity in rhodium(I)-catalysis by planar chiral
    • Authors: Michaela Christina Melcher; Trpimir Ivšić, Charlotte Olagnon, Christina Tenten, Arne Lützen, Daniel Strand
      Abstract: Planar chiral 5,11-disubstiuted dibenzo[a,e]cyclo-octatetraenes (dbCOTs) have been developed as the first useful chiral homologs to dbCOT-ligands for asymmetric applications. Methods enabling preparation of such compounds on a gram-scale in enantiomerically pure form are described. Evaluated as ligands in rhodium(I) catalyzed 1,4- and 1,2-arylation reactions, tertiary and quarternary stereogenic centers were formed with excellent yields and selectivities of up to>99% ee. A catalytic asymmetric synthesis of a key cyclization precursor to (-)-penifulvin A highlights the system in an applied context.
      PubDate: 2017-11-13T05:15:30.402537-05:
      DOI: 10.1002/chem.201704816
  • Hybridized 1T/2H MoS2 Having Controlled 1T Concentrations and its use in
    • Authors: Nguyen Thi Xuyen; Jyh-Ming Ting
      Abstract: Molybdenum disulfide (MoS2) nanoflowers consisting of hybridized 1T/2H phases have been synthesized by using a microwave-assisted hydrothermal (MTH) method. The concentration of the 1T phase, ranging from 40 % to 73 %, is controlled by simply adjusting the ratio of the Mo and S precursors. By using the hybridized 1T/2H MoS2 as an electrode material, it was demonstrated that the resulting supercapacitor performance is dominated by the 1T phase concentration. It was found that a supercapacitor with 73 % 1T phase exhibits excellent capacitance of 259 F g−1 and great cyclic stability after 1000 cycles. The formation mechanism of the MHT-synthesized hybridized 1T/2H MoS2 is also reported. More importantly, the mechanism also explains the observed relationship between the 1T phase concentration and the ratio of the Mo and S precursors.Molybdenum disulfide (MoS2) nanoflowers consisting of hybridized 1T/2H phases have been synthesized by using a microwave-assisted hydrothermal (MTH) method. The concentration of the 1T phase, ranging from 40 % to 73 %, is controlled by simply adjusting the ratio of the Mo and S precursors. The resulting supercapacitor performance using the hybridized 1T/2H MoS2 as an electrode material is dominated by the 1T phase concentration.
      PubDate: 2017-11-13T04:58:43.765349-05:
      DOI: 10.1002/chem.201703690
  • 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
      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 ▪▪ ff. (
      DOI : 10.1002/chem.201702955).
      PubDate: 2017-11-13T04:58:17.531319-05:
  • 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
      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. (
      DOI : 10.1002/chem.201702955).
      PubDate: 2017-11-13T04:58:14.270655-05:
  • Direct Arylation of Dipyrrolonaphthyridinediones Leads to Red-Emitting
           Dyes with Conformational Freedom
    • Authors: Bartłomiej Sadowski; Michał F. Rode, Daniel T. Gryko
      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. (
      DOI : 10.1002/chem.201702306).
      PubDate: 2017-11-13T04:58:01.44803-05:0
  • Stereoselective nanozyme based on ceria nanoparticles engineered with
           amino acids
    • Authors: Xiaogang Qu; Yuhuan Sun, Chuanqi Zhao, Nan Gao, Jinsong Ren
      Abstract: Stereoselectivity towards substrate is one of the most important characteristics of enzymes. Amino acids, as cofactors of many enzymes, play important roles in stereochemistry. Herein, chiral nanozymes were constructed by grafting a series of D- or L-amino acids on surfaces of ceria (cerium oxide) nanoparticles. We selected the most commonly used drug for combating Parkinson's disease 3, 4-dihydroxyphenylalanine (DOPA) enantiomers as examples for chiral catalysis. Through detailed kinetic studies of eight amino acids modified cerium oxide nanoparticles (CeNP), we found that phenylalanine-modified CeNP was optimal for the DOPA oxidation reaction and showed excellent stereoselectivity towards its enantiomers. L-phenylalanine-modified CeNP showed higher catalytic ability for oxidation of D-DOPA while D-phenylalanine-modified CeNP were more effective to L-DOPA. Taken together, the results indicated that stereoselective nanozyme can be constructed by grafting nanozyme with chiral molecules. This work may inspire better design of chiral nanozymes.
      PubDate: 2017-11-12T21:56:34.903719-05:
      DOI: 10.1002/chem.201704579
  • Heterogeneous Acid-Catalyzed Racemization of Tertiary Alcohols
    • Authors: Jan-E. Bäckvall; Tamas Gorbe, Richard Lihammar
      Abstract: Tertiary alcohols are important structural motifs in natural products and building blocks in organic synthesis but only few methods are known for their enantioselective preparation. Chiral resolution is one of these approaches which leaves one enantiomer (50% of the material) unaffected. An attractive method to increase the efficiency of those resolutions is to racemize the unaffected enantiomer. In the present work we have developed a practical racemization protocol for tertiary alcohols. Five different acidic resin materials were tested. The Dowex 50WX8 was the resin of choice since it was capable of racemizing tertiary alcohols without any byproduct formation. Suitable solvents and a biphasic system were investigated, and the optimized system was capable of racemizing differently substituted tertiary alcohols.
      PubDate: 2017-11-12T21:56:03.492069-05:
      DOI: 10.1002/chem.201704691
  • Mechanistic insights on human phosphoglucomutase revealed by transition
           path sampling and molecular dynamics calculations
    • Authors: Natercia Bras; Pedro Fernandes, Maria Ramos, Steven Schwartz
      Abstract: Human -phosphoglucomutase 1 (-PGM) catalyzes the isomerization of glucose-1-phosphate into glucose-6-phosphate (G6P) via two sequential phosphoryl transfer steps with a glucose-1,6-bisphosphate (G16P) intermediate. Given that the release of G6P in gluconeogenesis raises glucose output levels, -PGM represents a tempting pharmacological target for type 2 diabetes. Here, we provide the first theoretical study of the catalytic mechanism of human -PGM. We performed transition path sampling simulations to unveil the atomic details of the two catalytic chemical steps, which could be key for developing transition state (TS) analogue molecules with inhibitory properties. Our calculations revealed that both steps proceed via a concerted SN2-like mechanism, with a loose metaphosphate-like TS. Even though experimental data suggests that the two steps are identical, we observed noticeable differences: i) the transition state ensemble has a well-defined TS region and a late TS for the second step; and ii) larger coordinated protein motions are required to reach the TS of the second step. We have identified key residues (Arg23, Ser117, His118, Lys389 and the Mg2+ ion) that contribute in different ways to the reaction coordinate. Accelerated molecular dynamics simulations suggest that the G16P intermediate may reorient without leaving the enzymatic binding pocket, through significant conformational rearrangements on G16P and on specific loop regions of human -PGM.
      PubDate: 2017-11-12T21:55:59.837018-05:
      DOI: 10.1002/chem.201705090
  • Potential therapeutic applications of MnSODs and SOD-mimetics
    • Authors: Rosalin Bonetta
      Abstract: Natural as well as synthetic antioxidants are constantly being investigated for their efficiency in combatting the effects of oxidative stress, which appears to be the responsible cause of several diseases, which include cancer, central nervous system disorders, ischaemia-reperfusion disorders, cardiovascular conditions and diabetes. Superoxide dismutases (SODs) constitute the ubiquitous antioxidant defenses against oxidative stress that underlies numerous pathological conditions. Therefore, the development of therapeutics aimed at either delivering MnSOD more effectively to target tissues in the body in the form of MnSOD gene therapy, or the synthesis of molecules that mimic the activity of superoxide dismutase is constantly being explored. Such classes that have been developed as SOD mimics include the Mn metalloporphyrins, Mn cyclic polyamines, Mn salen complexes, MnPLED derivatives as well as the nitroxides. Thus far, SOD mimics have shown remarkable efficacy in several animal models suffering from oxidative stress injuries. A promising approach for the future of SOD and SOD mimic therapeutics appears to involve combination treatment of the antioxidants with radiotherapy or chemotherapy.
      PubDate: 2017-11-12T21:55:27.110818-05:
      DOI: 10.1002/chem.201704561
  • Lewis Acid-Assisted Photo-Induced Intermolecular Coupling Between
           Acylsilanes and Aldehydes: A Formal Cross Benzoin-Type Condensation
    • Authors: Kento Ishida; Fumiya Tobita, Hiroyuki Kusama
      Abstract: Intermolecular carbon-carbon bond forming reaction between readily available acylsilanes and aldehydes was achieved under photo-irradiation conditions with assistance of a catalytic amount of Lewis acid. Nucleophilic addition of photochemically-generated siloxycarbenes to aldehydes followed by 1,4-silyl migration afforded synthetically useful α-siloxyketones. Electrophilic activation of aldehydes by Lewis acid is highly important to realize this reaction efficiently, otherwise the yield of the desired coupling products were significantly decreased. Noteworthy is that a formal cross benzoin-type reaction using acylsilanes was achieved under Lewis acidic conditions. To our knowledge, this is the first example of Lewis acid-catalyzed reaction of photochemically-generated siloxycarbenes with electrophiles.
      PubDate: 2017-11-10T12:25:25.463835-05:
      DOI: 10.1002/chem.201704776
  • Synthesis and characterization of a paramagnetic [2]rotaxane based on a
           crown ether-like wheel incorporating a nitroxide motif
    • Authors: Valentina Bleve; Paola Franchi, Evangelia Konstanteli, Lorenzo Gualandi, Stephen M Goldup, Elisabetta Mezzina, Marco Lucarini
      Abstract: The synthesis of a new nitroxide crown ether (8) and its use as the wheel in a bistable [2]rotaxane containing dialkylammonium and 4,4`-bipyridinium recognition sites, is reported. The synthesis of 8 was achieved by the sequential addition of substituted phenyl groups to nitrone derivatives leading to the preferential formation of the cis stereoisomer. Due to charge-dipolar interactions between the nitroxide unit and bipyridinium moiety, it was possible to probe the movement of the macrocycle between the two molecular stations of the [2]rotaxane after addition of a base by measuring the nitrogen hyperfine splittings in the corresponding EPR spectra. The equilibrium constant for the complexation of dibenzyl viologen by macrocycle 8 was also determined by EPR titration.
      PubDate: 2017-11-10T10:02:58.903704-05:
      DOI: 10.1002/chem.201704969
  • Regio- and Enantioselective Allylic Amination of Aliphatic MBH Adducts
           with N-Heteroaromatics
    • Authors: Haiming Guo; Kuiling Ding, Haixia Wang, Lulu Yu, Mingsheng Xie, Jiang Wu, Guirong Qu
      Abstract: Palladium-catalyzed regio- and enantioselective allylic amination of aliphatic Morita-Baylis-Hillman (MBH) adducts with N-heteroaromatics, including benzimidazole, 4,5-diphenylimidazole, benzotriazole, and purine nucleophiles, have been developed using a spiroketal-based diphosphine (SKP) as ligand, affording a range of chiral branched N-allylation products in high selectivities.
      PubDate: 2017-11-10T09:30:57.057217-05:
      DOI: 10.1002/chem.201704772
  • Catalyst- and Supporting Electrolyte-Free Electrosynthesis of
           Benzothiazoles and Thiazolopyridines in Continuous Flow
    • Authors: Ana A. Folgueiras-Amador; Xiang-Yang Qian, Haichao Xu, Thomas Wirth
      Abstract: A catalyst- and supporting electrolyte-free method for electrochemical dehydrogenative C-S bond formation in continuous flow has been developed. A broad range of N-arylthioamides have been converted to the corresponding benzothiazoles in good to excellent yields and with high current efficiencies. This transformation is achieved using only electricity and laboratory grade solvent, avoiding degassing or the use of inert atmosphere. This work highlights three advantages of electrochemistry in flow, which is (i) a supporting electrolyte-free reaction, (ii) an easy scale-up of the reaction without the need for a larger reactor and, (iii) the important and effective impact of having a good mixing of the reaction mixture, which can be achieved effectively with the use of flow systems. This clearly improves the reported methods for the synthesis of benzothiazoles.
      PubDate: 2017-11-10T07:25:37.237374-05:
      DOI: 10.1002/chem.201705016
  • Redox-Active Ligand Assisted Two-Electron Oxidative Addition to
    • Authors: Igor L. Fedushkin; Vladimir Dodonov, Alexandra Skatova, Vladimir Sokolov, Alexander Piskunov, Georgii Fukin
      Abstract: The reaction of digallane (dpp-bian)Ga-Ga(dpp-bian) (2) (dpp-bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with allylchloride (AllCl) proceeds as the two-electron oxidative addition and affords paramagnetic complexes (dpp-bian)Ga(1-All)Cl (3) and (dpp-bian)(Cl)Ga-Ga(Cl)(dpp-bian) (4). Treatment of complex 4 with pyridine induces intramolecular redox-process resulting diamagnetic (dpp-bian)Ga(Py)Cl (5). With allylbromide complex 2 gives metal- and ligand-centered addition products, (dpp-bian)Ga(1-All)Br (6) and (dpp-bian-All)(Br)Ga-Ga(Br)(dpp-bian-All) (7). The reaction of digallane 2 with Ph3SnNCO affords (dpp-bian)Ga(SnPh3)2 (8) and (dpp-bian)(NCO)Ga-Ga(NCO)(dpp-bian) (9). Treatment of GaCl3 with (dpp-bian)Na (in situ from Na and dpp-bian) in diethyl ether results 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(1-All)R (R = nBu, 12; Cp, 13) were synthesized starting from 3, 10, Bn2GaCl and tBu2GaCl by the salt metathesis. The salt elimination reaction between (dpp-bian)GaI2 (17) and tBuLi is accompanied with the reduction of the metal and of the dpp-bian ligand resulting in digallane 2 as the final product. Similarly, the reaction of 10 with MentMgCl (Ment = menthyl) proceeds with reduction of dpp-bian ligand and results in diamagnetic complex [(dpp-bian)GaCl2][Mg2Cl3(thf)6] (18). Compound 14 decomposes in toluene at reflux to complex (dpp-bian-tBu)Ga(tBu)2 (19).
      PubDate: 2017-11-10T06:25:32.503005-05:
      DOI: 10.1002/chem.201704128
  • Refreshing Rubbers as Customized Photothermal Conversion Materials through
           Post-Darkening Modeling Production
    • Authors: Ruiting Li; Zhen Wang, Peng Han, Yonglin He, Xiaohong Zhang, Yapei Wang
      Abstract: Organic conjugated polymers with low energy bandgap are rising as a particular class of NIR photothermal conversion materials. Yet these polymers routinely possess high phase transition temperature due to the rigid skeleton and strong intermolecular interaction. Rarely conjugated polymers can be thermally processed at low temperature, especially below 100°C. This work formulates a concept of post-darkening modeling production (p-DMP) by which the thermoplastic non-conjugated trans-polyisoprene (TPI) is refreshed into a photo-thermal conversion material with high light use efficiency. Two steps including the customizable shaping at low temperature and iodine vapor-tailored "darkening" ensure the ease of pre-paring photothermal conversion devices with desirable topol-ogies. In particular, the p-DMP is successfully extended to three-dimension (3D) printing, opening an avenue to fabricate per-sonalized photothermal products.
      PubDate: 2017-11-10T05:55:27.722029-05:
      DOI: 10.1002/chem.201704715
  • Protein Recognition by Functionalized Sulfonatocalix[4]arenes
    • Authors: Aishling Doolan; Martin Rennie, Peter B Crowley
      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 specifically to Lys4 of cytochrome c, as revealed by X-ray crystallography. A dimeric packing arrangement mediated by ligand-ligand contacts in the crystal suggested a possible assembly mechanism. The different functions of these calixarenes in protein recognition are discussed.
      PubDate: 2017-11-10T05:25:41.206143-05:
      DOI: 10.1002/chem.201704931
  • Why the flavin dinucleotide cofactor needs to be covalently linked to
    • Authors: Daniel F.A.R. Dourado; Marcel Swart, Alexandra Teresa Pires Carvalho
      Abstract: A covalently bound flavin cofactor is predominant in the succinate:ubiquinone oxidoreductase (SQR, Complex II), an essential component of the aerobic electron transport, and in the menaquinol:fumarate oxidoreductase (QFR), the anaerobic counterpart, albeit being only present in ~10% of the known flavoenzymes. Here, we investigated the role of this 8α-N(3)-histidyl linkage between the flavin dinucleotide (FAD) cofactor and the respiratory Complex II. After parameterization with DFT we performed classical molecular dynamics simulations and quantum mechanics calculations of Complex II:FAD and Complex II:FADH2, covalently bound and unbound to His-A57. We observed that the covalent bond is essential for the active center arrangement of the FADH2/FAD cofactor. Removal of this bond causes a displacement of the isoalloxazine group which influences the interactions with the protein, flavin solvation and the possible proton transfer pathways. Specifically, for the non-covalently bound FADH2 cofactor the N1 atom moves away from the His-A365 and His-A254 and the N5 atom moves away from glutamine 62A. Both histidines and the glutamine interact with a chain of water molecules that cross the enzyme which is most likely involved in proton transfer. Breaking this chain of water molecules could thereby compromise proton transfer across the two active sites of Complex II.
      PubDate: 2017-11-10T04:55:33.796105-05:
      DOI: 10.1002/chem.201704622
  • Ring-chain morphology control in overall-neutral, internally ion-paired
           supramolecular polymers
    • Authors: Nadia Manganaro; Ilenia Pisagatti, Anna Notti, Andrea Pappalardo, Salvatore Patanè, Norberto Micali, Valentina Villari, Melchiorre F. Parisi, Giuseppe Gattuso
      Abstract: The self-assembly of internally-ion-paired neutral AA/BB-type supramolecular polymers composed of complementary di-ionizable homoditopic pairs of monomers is reported. Host-to-guest double proton transfer mediates the recognition between bis-calix[5]arene-dicarboxylic acids and α,ω-diaminoalkanes, yielding cyclic, doughnut-shaped assemblies whose morphology (i.e., cyclic vs. linear) can be controlled by means of external chemical stimuli. The behavior of these intriguing aggregates both in solution and on surface was investigated by a combination of 1H and DOSY NMR, light scattering and AFM techniques.
      PubDate: 2017-11-10T04:07:44.721823-05:
      DOI: 10.1002/chem.201703342
  • Nitromethane Bridged Bis(1,3,4-oxadiazoles): Trianionic Energetic Salts
           with Low sensitivities
    • Authors: Jean'ne M. Shreeve; Qiong Yu, Gregory H. Imler, Damon Parrish
      Abstract: Trianionic energetic salts based on one nitromethylene and two dinitromethyl anions were designed and synthesized. Interestingly, the unstable dinitromethylene group of 2 was changed to a mononitromethylene group via an aminolysis reaction to form 3 while in 8 it was hydrolyzed to a carbonyl group resulting in 9. All the new compounds were fully characterized by infrared, multinuclear NMR spectra, and elemental analysis. The structures of triammonium ((nitromethanidylene)bis(1,3,4-oxadiazole-5,2-diyl))bis(dinitromethan -ide) dihydrate (3·2H2O) and bis(2-dinitromethyl-1,3,4-oxadiazole-5-yl)methanone (9) were further confirmed with single-crystal X-ray analysis. Based on their different physical and detonation properties, some of the energetic salts are found to exhibit good energetic performance and low sensitivity.
      PubDate: 2017-11-10T01:55:21.045891-05:
      DOI: 10.1002/chem.201704939
  • Extraordinarily Large Ferromagnetic Coupling (J ≥ 150 cm-1) via Electron
           Delocalization in a Heterometallic Mo-Mo-Ni Chain Complex
    • Authors: Jill Ann Chipman; John F. Berry
      Abstract: The new heterometallic chain compounds Mo2Ni(dpa)4Cl2 (1) and [Mo2Ni(dpa)4Cl2]OTf (2) (dpa = 2,2'-dipyridylamine) have been prepared and studied by crystallography and magnetic susceptibility, among other methods. Oxidation of 1 to 2 removes an electron from the multiply-bonded Mo2 unit, consistent with the formulation of 2 as containing a (Mo2)5+‧‧‧(Ni)2+ core. While 1 contains an S = 1, pseudo-octahedral Ni(II) ion, 2 has an S = 3/2 ground state in which the two Ni(II) unpaired electrons are joined by an unpaired electron in a Mo—Mo δ orbital. The S = 3/2 ground state is persistent to 300 K, evidencing strong ferromagnetic coupling of the Mo2 and Ni spins with J ≥ 150 cm-1. This ferromagnetic interaction occurs via delocalization of a σnb electron across all three metal atoms, forcing ferromagnetic alignment of electrons in orthogonal Ni and Mo2 δ-symmetry orbitals. We anticipate that this new means of coupling spins can be used as a design principle for the preparation of new compounds with high spin ground states.
      PubDate: 2017-11-09T21:55:54.088871-05:
      DOI: 10.1002/chem.201704588
  • Phosphorescence Tuning via Heavy Atom Placement in Unsymmetrical
           Difluoroboron b-Diketonate Materials
    • Authors: Tiandong Liu; Guoqing Zhang, Ruffin Evans, Carl Trindle, Zikri Altun, Christopher DeRosa, Fang Wang, Meng Zhuang, Cassandra L. Fraser
      Abstract: Difluoroboron ß-diketonates show both fluorescence and room-temperature phosphorescence when confined to a rigid matrix such as poly(lactic acid). These materials have been utilized as optical oxygen sensors (e.g. tumors, wounds and cells). A series of naphthyl-phenyl dyes (BF₂nbm) (1-6) were prepared to test heavy-atom placement effects. The BF₂nbm dye (1) was substituted with bromides on naphthyl (2), phenyl (3), or both rings (4) to tailor the fluorescence-to-phosphorescence ratio and phosphorescence lifetime—important features for designing oxygen-sensing dyes via the heavy atom effect. According to computational studies, the naphthyl ring is the major donor. Thus, Br substitution on the naphthyl ring produced greater effects on the optical properties such as increased phosphorescence intensity and decreased phosphorescence lifetime compared to phenyl substitution. However, for electron-donating piperidyl-phenyl dyes (5), the phenyl aromatic is the major donor. As a result, bromide substitution on the naphthyl ring (6) did not alter the optical properties significantly. Experimental data and computational modeling show the importance of Br position. The S1 and T1 states are described by two singly occupied MOs (SOMOs). When both of these SOMOs have substantial amplitude on the heavy atom, passage from S1 to T1 and emission from T1 to S0 are both favored. This shortens the excited state lifetimes and enhances phosphorescence.
      PubDate: 2017-11-09T13:25:21.908489-05:
      DOI: 10.1002/chem.201703513
  • Efficient Endo Cycloisomerization of Terminal Alkynols Catalyzed by a New
           Ruthenium Complex with 8-(Diphenylphosphino)-quinoline Ligand and
           Mechanism Investigation
    • Authors: Tao Cai; Yu Yang, Wei-Wei Li, Wen-Bing Qin, Ting-Bin Wen
      Abstract: Several new ruthenium complexes supported by the P,N-donor ligand 8-(diphenylphosphino)quinoline (DPPQ) were synthesized, including RuCl2(DPPQ)2 (1), [Ru(-Cl)(DPPQ)2]2(BPh4)2 (2) and [RuCl(DPPQ)2Py](BF4) (3). Complex 2, with only 1 mol% loading, was found to be catalytically active for the endo cycloisomerization of various terminal alkynols to endo-cyclic enol ethers in moderate to excellent yields. In particular, the 7- and 8-endo heterocyclization can be achieved efficiently to give the seven-membered 3-benzoxepine and eight-membered 3-benzo[d]oxocine derivatives. The stoichiometric reactions of 2 with various alkynol substrates have been carried out to investigate the mechanism, which led to a series of seven-, six-, and five-membered oxacyclocarbene ruthenium complexes including [RuCl(DPPQ)2{=CCH2C6H4CH2CH2O}](BPh4) (12) and [RuCl(DPPQ)2{=CCH2(CH2)nCH2O}](BPh4) (n = 3, 12'; n = 2, 13; n = 1, 14). The quantitative transformation of oxacyclocarbene 12 into catalyst 2 and 3-benzoxepine 5a as well as the efficient catalytic activity of 12 for the endo-cyclization of 4a demonstrated that 12 is a key intermediate involved in the catalytic cycle. Moreover, comparative studies on the modeling reactions and catalytic activity of the series of oxacyclocarbene complexes indicated that the different catalytic activity of 2 for the endo-cycloisomerization of different types of alknynols can be related to the reactivity of the respective ruthenium oxacyclocarbene intemediates.
      PubDate: 2017-11-09T11:56:32.563858-05:
      DOI: 10.1002/chem.201703971
  • Large changes in both fluorescent color and intensity of symmetrically
           substituted arylmaleimides caused by subtle structure modification
    • Authors: Jingwei Wang; Zhengde Liu, Shuming Yang, Youzhi Lin, Zhenghuan Lin, Qidan Ling
      Abstract: Herein, we report four diarylmaleimides based on 3 or 2-substituted benzothiophene (M3S or M2S) and benzofuran (M3O or M2O), showing totally different emission properties: ACQ, AIE, and dual-state strong emission (DSE) in both solution and solid states. Their emitting color in solids can be adjusted from green yellow into red. Thereinto, M2O displays strong red solid-stated emission at 630 nm with 46.3% of quantum yield. Single-crystal X-ray diffraction analysis confirms that their large distinction in solid-stated emission is originated from their totally different packing structure: hydrogen-bonded organic frameworks (HOFs) for M3S, stagger structure for M3O, J-aggregation for M2S, and weak H-aggregation for M2O. HOF of M3S and weak H-aggregation of M2O make them produce inverse-type piezochromic fluorescence: blue-shifted "turn-on" and red shifted "turn-off" emission, respectively. These results provide new insight in fluorescence manipulated by subtle structure modification.
      PubDate: 2017-11-09T11:56:09.376574-05:
      DOI: 10.1002/chem.201703652
  • Well-Defined Chiral Copper NHC Complex in Asymmetric Conjugated
           β-Borylation and One-Pot Metathesis-Asymmetric β-Borylation
    • Authors: Karol Grela; Anupam Jana, Krzysztof Woźniak, Damian Trzybiński
      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 chiral β-borylated ester from simple unconjugated alkenes though unprecedented one-pot cross metathesis-asymmetric borylation sequence.
      PubDate: 2017-11-09T11:25:36.933178-05:
      DOI: 10.1002/chem.201704335
  • A Magic Ratio Rule for Beginners: a Chemist's Guide to Quantum
           Interference in Molecules
    • Authors: Colin J Lambert; Shi-Xia Liu
      Abstract: This overview will give a glimpse into chemical design principles for gating quantum interference (QI) effects in molecular-scale devices. Direct observation of room temperature QI in single-molecule junctions has stimulated growing interest in fabrication of tailor-made molecular electronic devices. Herein, we outline a new conceptual advance in the scientific understanding and technological know-how necessary to control QI effects in single molecules by chemical modification. We start by discussing QI from a chemical viewpoint and then describe a new magic ratio rule (MRR), which captures a minimal description of connectivity-driven charge transport and provides a useful starting point for chemists to design appropriate molecules for molecular electronics with desired functions. The MRR predicts conductance ratios, which are solely determined by QI within the core of polycyclic aromatic hydrocarbons (PAHs). The manifestations of QI and related quantum circuit rules for materials discovery are direct consequences of the key concepts of weak coupling, locality, connectivity, mid-gap transport and phase coherence in single-molecule junctions.
      PubDate: 2017-11-09T09:25:34.751351-05:
      DOI: 10.1002/chem.201704488
  • Cobalt-Catalyzed Asymmetric Allylation of Cyclic Ketimines
    • Authors: Liang Wu; Qihang Shao, Guoqiang Yang, Wanbin Zhang
      Abstract: A Co(II)/Box-catalyzed enantioselective addition of potassium allyltrifluoroborate to cyclic ketimines was developed, providing the corresponding chiral α-tertiary amines in high yields and with good enantioselectivities. Alkoxycarbonyl and alkyl substituted saccharin-derived ketimines are suitable substrates for this allylation reaction. The product can be converted to complex molecules over several simple steps, including a precursor of MK-0371, which is a kinesin spindle protein inhibitor. In addition, this catalytic system showed a strong positive non-linear effect.
      PubDate: 2017-11-09T06:56:23.854557-05:
      DOI: 10.1002/chem.201704760
  • Self-assembled nanomicelles as MRI blood-pool contrast agent
    • Authors: Andrej Babic; Vassily Vorobiev, Celine Xayaphoummine, Gaelle Lapicorey, Anne-Sophie Chauvin, Lothar Helm, Eric Allémann
      Abstract: Gadolinium-loaded nanomicelles show promise as future magnetic resonance imaging (MRI) contrast agents (CAs). Their increased size and high gadolinium (Gd) loading gives them an edge in proton relaxivity over smaller molecular Gd-complexes. Their size and stealth properties are fundamental for their long blood residence time opening the possibility for use as blood-pool contrast agents. Using L-tyrosine as a three-functional scaffold we synthesized a nanostructure building block 8. The double C18 aliphatic chain on one side, Gd-DO3A with access to bulk water in the center and 2 kDa PEG on the hydrophilic side gave the amphiphilic properties required for the core-shell nanomicellar architecture. The self-assembly into Gd-loaded monodispersed 10-20 nm nanomicelles occurred spontaneously in water. Tyr-MRI nanomicelles display very high relaxivity at 29 mM-1s- 1 at low field strength and low cytotoxicity. Good contrast enhancement of the blood vessels and the heart together with prolonged circulation time in vivo, makes Tyr-MRI an excellent candidate for a new supramolecular blood-pool MRI CA.
      PubDate: 2017-11-09T05:25:29.372321-05:
      DOI: 10.1002/chem.201703962
  • Preparation and characterization of P2BCh ring systems (Ch = S, Se) and
           their reactivity with N-heterocyclic carbenes
    • Authors: Paul J. Ragogna; Cameron Graham, Clement Millet, Amy N Price, Juuso Valijus, Michael J Cowley, Heikki Tuononen
      Abstract: Four-membered rings with a P2BCh core (Ch = S, Se) have been synthesized via reaction of phosphinidene chalcogenide (Ar*P=Ch) and phosphaborene (Mes*P=BNR2). The mechanistic pathways towards these rings are explained by detailed computational work that confirmed the preference for the formation of P-P, not P-B, bonded systems, which seems counterintuitive given that both phosphorus atoms contain bulky ligands. The reactivity of the newly synthesized heterocycles, as well as that of the known (RPCh)n rings (n = 2, 3), was probed by the addition of N-heterocyclic carbenes, which revealed that all investigated compounds can act as sources of low-coordinate phosphorus species.
      PubDate: 2017-11-09T03:55:43.525071-05:
      DOI: 10.1002/chem.201704337
  • Conformational Bias by a Removable Silyl Group: Construction of
           Bicyclo[n.3.1]alkenes via Ring Closing Metathesis
    • Authors: Minggui Lin; Pei-Jun Cai, Zhixiong Zeng, Na Lin, Yang Shen, Bin Tang, Fan Li, Chen Chen, Zhi-Xiang Yu, Yandong Zhang
      Abstract: We herein report a novel strategy based on a conformationally controlled RCM by a removable silyl group, which allows the facile synthesis of various bicyclo[n.3.1]alkenes, especially a set of highly strained bicyclo[5.3.1]alkenes. Further derivatizations of the silyl group and the resultant double bond of bicyclo[5.3.1]undecene 2f enabled a concise synthesis of A-B-C ring skeleton of taxol. Density functional theory (DFT) calculations suggest that the introduction of a bulky silyl group at C-5 position of the 1,3-dialkenylcyclohexanol substrates dramatically lowers the energy bias gap between diaxial conformers (to RCM) and diequatorial conformers (to cross metathesis), thereby favoring the expected RCM reaction to give the challenging bridged molecules.
      PubDate: 2017-11-09T03:25:46.880166-05:
      DOI: 10.1002/chem.201705275
  • Exponential activation of Carbonic Anhydrase by encapsulation in dynameric
           host-matrices with chiral discrimination
    • Authors: Mihail Barboiu; Yan Zhang, Claudiu Supuran
      Abstract: This paper reports an unexpected exponential activation of bovine carbonic anhydrase (bCA) in aqueous solutions in the presence of dynameric host matrices. Successive experiments confirmed the important role of the dynamic imine-exchanges within the dynameric host structures for the direct enzyme activation. It allows the optimal encapsulation of guest enzyme, while the presence of external proton-sponge amino groups is less important. We note that the no-exchanging polymeric sec-amine congeners resulted from imine reduction of dynameric structures, show no obvious activation on bCA. Although the dynamers synthesized from diamino chiral-pair precursors showed similar activation constants toward bCA, different activation delay time was observed from these two dynamers of opposite optical activity. The circular dichroism (CD) spectra demonstrate selective structural changes in the secondary structure of bCA, upon dynameric encapsulation in aqueous solution. The different interaction molds observed in CD spectra for the dynamers with opposite chirality, explains the required longer activation time for one of the dynamers.
      PubDate: 2017-11-09T01:56:01.562555-05:
      DOI: 10.1002/chem.201704605
  • Deltamides and croconamides: expanding the range of dual H-bond donors for
           selective anion recognition
    • Authors: vincent zwicker; karen yuen, david smith, junming ho, lei qin, peter turner, Katrina Jolliffe
      Abstract: Dual H-bond donors are widely used as recognition motifs in anion receptors. We report the synthesis of a library of dual H-bond receptors, incorporating the deltic and croconic acid derivatives, termed deltamides and croconamides, and a comparison of their anion binding affinities (for monovalent species) and Brønsted acidities to those of the well-established urea and squaramide dual H-bond donor motifs. For dual H-bond cores with identical substituents, the trend in Brønsted acidity is croconamides> squaramides>deltamides> ureas, with the croconamides found to be 10-15 pKa units more acidic than the corresponding ureas. In contrast to the trends displayed by ureas, deltamides and squaramides, N,N'-dialkyl croconamides displayed higher binding affinity to chloride than the N,N'-diaryl derivatives, which was attributed to partial deprotonation of the N,N'-diaryl derivatives at neutral pH. A number of differences in anion binding selectivity were observed upon comparison of the dual H-bond cores. Whereas the squaramides display similar affinity for both chloride and acetate ions, the ureas have significantly higher affinity for acetate than chloride ions and the deltamides display higher affinity for dihydrogenphosphate ions than other oxoanions or halides. These inherent differences in binding affinity could be exploited in the design of anion receptors with improved ability to discriminate between monovalent anions.
      PubDate: 2017-11-09T01:55:37.182319-05:
      DOI: 10.1002/chem.201704388
  • PKU-21: A Novel Layered Germanate Built from Ge₇ and Ge₁₀ Clusters
           for CO₂ Separation
    • Authors: Jie Liang; Jie Su, Fei Peng, Yongfei Zeng, Junliang Sun
      Abstract: The attractive properties of layered inorganic materials, which make them suitable for numerous applications in chemical industries and life sciences, originated from their crystalline framework structures. Here we report a new layered germanate PKU-21, which was prepared by the hydrothermal synthesis method using 2-propanolamine (MIPA) as the structure-directing agent. The structure of PKU-21 was determined from synchrotron single crystal X-ray diffraction and synchrotron powder X-ray diffraction data. It reveals a complicated framework structure containing 18 unique Ge atoms in the asymmetric unit. PKU-21 is the first layered germanate built from both Ge₇ and Ge₁₀ clusters, following the 3-dimensional germanate PKU-17. The preparation and structure of PKU-21 are discussed in comparison with PKU-17, which provides new insight into the formation mechanism of germanates. Gas sorption experiments indicate that the layered PKU-21 sample exhibits a better CO₂ sorption selectivity over N₂ and CH₄ at 298 K than at 273 K, making it a promising candidate for CO₂ separation.
      PubDate: 2017-11-09T00:25:56.95533-05:0
      DOI: 10.1002/chem.201704573
  • Construction of Zeolite-Like Cluster Organic Frameworks from 3d-4d/3d-3d
           Heterometallic Superterahedral Secondary Building Units: Syntheses,
           Structures and properties
    • Authors: Xixiong Li; Shou-Tian Zheng, Li-Dan Lin, Chu-Chu Deng, Dan Zhao
      Abstract: Two zeolite-like cluster organic frameworks based on Cd-Cu/Mn-Cu heterometallic supertetrahedral secondary building units have been successfully constructed under solvothermal conditions, namely, Cu[Cd4Cu6(L)4(H2O)18](Ac)9*DMA*3H2O (1), and Cu[Mn4Cu6(L)4(Ac)3(H2O)12](Ac)6*CH3CN*13H2O (2), where H3L= 2-(hydroxymethyl)-2-(pyridin-4-yl)-1,3-propanediol, Ac = CH3COO-, DMA= N,N'-Dimethylacetamide. Single-crystal X-ray structural analysis reveal that both 1 and 2 exhibit 3-dimensional zeolite-like architectures with similar 4-connected conponents but possess definitely different topologies of diamondoid (Dia) and uncommon Ionsdaleite (Ion), respectively. 1 and 2 represent the first cases of zeolite-like cluster organic frameworks containing Cd-Cu/Mn-Cu heterometallic superterahedral secondary building units. Furthermore, the magnetic properties and porous nature of 1 and 2 were also been studied.
      PubDate: 2017-11-08T21:56:04.942784-05:
      DOI: 10.1002/chem.201704511
  • Magnetostructural analysis of orthogonal
           1-aryl-3-phenyl-1,4-dihydrobenzo[e][1,2,4]triazin-4-yl derivatives
    • Authors: Piotr Kaszynski; Anita Gardias, Jacek Szczytko, Emilia Obijalska, Damian Trzybinski, Slawomir Domagala, Krzysztof Wozniak
      Abstract: 3-Phenyl-1,4-dihydrobenzo[e][1,2,4]triazinyl radicals with the N(1) position substituted with naphth-2-yl (1b), naphth-1-yl (1c), pyren-1-yl (1d), anthracen-9-yl (1e), 2-trifluoromethylphenyl (1f), 3-trifluoromethylphenyl (1g), and 2-iodophenyl (1h) were characterized by using single-crystal X-ray diffraction, variable temperature magnetic susceptibility, and DFT computational methods. The substituent at the N(1) is essentially orthogonal to the heterocycle plane in 1f and 1h, and with a high torsion angle in 1c and 1d. Radicals 1c and 1h form unusual infinite chains with crisscrossing hetero-co-facial π-π interactions, while radical 1d forms analogous homo-co-facial arrangements. Infinite chains of homo-co-facial π-π dimers are found in 1b and 1f and 1g; in the latter the position of the CF3 group controls the slippage of the dimers in the chain. No π-π parallel arrangements were found in 1e. Magnetic susceptibility measurements demonstrated strong antiferromagnetic interactions in 1b (J = -264±4 cm-1) and 1f (J = -134±1 cm-1), while weak intradimer ferromagnetic interactions were found in 1g (J2 = +21±1 cm-1 and J1 = -15±1 cm-1). Other derivatives exhibit typical weak antiferromagnetic exchange interactions in a range of -5 to -10 cm-1
      PubDate: 2017-11-08T21:56:01.083279-05:
      DOI: 10.1002/chem.201703576
  • Striking an access to the bacteria via (reversible) control of
    • Authors: Anzhela Galstyan; Johannes Putze, Ulrich Dobrindt
      Abstract: Development of antimicrobial photodynamic therapy (aPDT) is highly dependent on the development of suitable photosensitizers (PS): ideally affinity of PS towards bacterial cells should be much higher than towards mammalian cells. Cationic charge of PS may lead to selective binding of PS to bacteria mediated by electrostatic interaction; however, the photodynamic outcome is highly dependent on the lipophilicity of PS. Herein we report the aPDT effect of silicon(IV)phthalocyanine derivatives bearing four positive charges and methyl, phenyl or naphthyl substituents on the periphery of the macrocycle. We show that via modulation of lipophilicity it is possible to find a therapeutic window where bacteria but not mammalian cells are effectively killed. The photobiological activity of these PSs dropped significantly when host-guest complexes of PSs with cucurbit[7]uril (CB[7]) were used. CB[7] blocks the hydrophobic part of the molecule and reduces lipophilicity of the PS, indicating that a hydrophobic interaction with the outer membrane of bacterial cells is essential for aPDT activity. Efficiencies of obtained PSs were evaluated using different uropathogenic E. coli isolates and human kidney epithelial carcinoma cells.
      PubDate: 2017-11-08T13:25:24.352873-05:
      DOI: 10.1002/chem.201704562
  • Front Cover: Robust Macroscopic 3D Sponges of Manganese Oxide Molecular
           Sieves (Chem. Eur. J. 64/2017)
    • Authors: Zhenxin Liu; Depeng Wu, Xuehui Guo, Shaoming Fang, Lizhen Wang, Yu Xing, Steven L. Suib
      Pages: 16104 - 16104
      Abstract: Free-standing 3D OMS-2 sponges with controlled densities are presented. The 3D OMS-2 sponges possess a combination of outstanding physical, mechanical, and electrical properties. Moreover, some of these properties have systematic trends with various densities. This study sheds new light on manipulating properties of such sponges through controlling sponge densities. These new materials are promising for various applications such as catalysis, sensing, energy storage, and environmental materials. More information can be found in the Full Paper by Z. Liu, Y. Xing et al. on page 16213.
      PubDate: 2017-09-21T09:00:35.12062-05:0
      DOI: 10.1002/chem.201704230
  • Cover Feature: Increased Conformational Flexibility of a
           Macrocycle–Receptor Complex Contributes to Reduced Dissociation Rates
           (Chem. Eur. J. 64/2017)
    • Authors: Adrian Glas; Eike-Christian Wamhoff, Dennis M. Krüger, Christoph Rademacher, Tom N. Grossmann
      Pages: 16105 - 16105
      Abstract: State-of-the-art isothermal titration calorimetry, 19F NMR spectroscopy and molecular dynamics simulations reveal unexpected differences in the binding kinetics of closely related macrocycles. Most strikingly, increased flexibility of the bound macrocycle correlates with elongated receptor residence time. These findings highlight the potential of loop-like peptide epitopes as starting point for macrocyclic peptidomimetics. More information can be found in the Communication by C. Rademacher, T. N. Grossmann et al. on page 16157.
      PubDate: 2017-09-12T02:46:18.383429-05:
      DOI: 10.1002/chem.201704109
  • Cover Feature: Laying Waste to Mercury: Inexpensive Sorbents Made from
           Sulfur and Recycled Cooking Oils (Chem. Eur. J. 64/2017)
    • Authors: Max J. H. Worthington; Renata L. Kucera, Inês S. Albuquerque, Christopher T. Gibson, Alexander Sibley, Ashley D. Slattery, Jonathan A. Campbell, Salah F. K. Alboaiji, Katherine A. Muller, Jason Young, Nick Adamson, Jason R. Gascooke, Deshetti Jampaiah, Ylias M. Sabri, Suresh K. Bhargava, Samuel J. Ippolito, David A. Lewis, Jamie S. Quinton, Amanda V. Ellis, Alexander Johs, Gonçalo J. L. Bernardes, Justin M. Chalker
      Pages: 16106 - 16106
      Abstract: With the Minamata Convention coming into force this year, there is a growing requirement for low-cost sorbents for mercury pollution. Thus, a polysulfide was prepared by the co-polymerization of sulfur and canola oil. As sulfur is a byproduct of the petroleum industry and used cooking oils are suitable starting materials, the resulting sorbent can be prepared entirely from waste. This high-sulfur rubber was effective in trapping diverse forms of mercury including mercury metal, inorganic mercury, and organomercury compounds. More information can be found in the Full Paper by J. M. Chalker et al. on page 16219.
      PubDate: 2017-09-12T02:46:14.527165-05:
      DOI: 10.1002/chem.201704108
  • Cover Feature: Control of Reversible Activation Dynamics of
           [Ru{η6:κ1-C6H5(C6H4)NH2}(XY)]n+ and the Effect of Chelating-Ligand
           Variation (Chem. Eur. J. 64/2017)
    • Authors: Francisco Martínez-Peña; Ana M. Pizarro
      Pages: 16107 - 16107
      Abstract: The design of organometallic pH-dependent switches to control in-tumor drug activation is presented. In this picture, the middle and background show that inactive ruthenium(II) arene complexes are innocuous (represented in blue), locked away inside boxes, unable to interact with their molecular target. It is shown, however, that protons (represented by the keys) can open the boxes and release the active form of the ruthenium drug (in red, with Ru in metallic grey), which can bind to DNA. The potential of a series of ruthenium(II) complexes to become pH-responsive anticancer drugs is thus demonstrated. More information can be found in the Full Paper by A. M. Pizarro and F. Martínez-Peña on page 16231.
      PubDate: 2017-09-21T09:02:32.417531-05:
      DOI: 10.1002/chem.201703853
  • Robust Macroscopic 3D Sponges of Manganese Oxide Molecular Sieves
    • Authors: Zhenxin Liu; Depeng Wu, Xuehui Guo, Shaoming Fang, Lizhen Wang, Yu Xing, Steven L. Suib
      Pages: 16108 - 16108
      Abstract: Invited for the cover of this issue is Zhenxin Liu, Yu Xing and co-workers at the Zhengzhou University of Light Industry and the University of Connecticut. The image depicts robust macroscopic 3D sponges composed of pure phase manganese oxide molecular sieve nanowires. Read the full text of the article at 10.1002/chem.201702787.“This study sheds new light on manipulating properties of such sponges” Read more about the story behind the cover in the Cover Profile and about the research itself on page 16213 ff. (
      DOI : 10.1002/chem.201702787).
      PubDate: 2017-09-25T05:25:42.853877-05:
  • Magnetic Nanotransducers in Biomedicine
    • Authors: Agostina Grillone; Gianni Ciofani
      Pages: 16109 - 16114
      Abstract: Owing to their abilities to identify diseased conditions, to modulate biological processes, and to control cellular activities, magnetic nanoparticles have become one of the most popular nanomaterials in the biomedical field. Targeted drug delivery, controlled drug release, hyperthermia treatment, imaging, and stimulation of several biological entities are just some of the several tasks that can be accomplished by taking advantage of magnetic nanoparticles in tandem with magnetic fields. The huge interest towards this class of nanomaterials arises from the possibility to physically drive their spatiotemporal localization inside the body, and to deliver an externally applied stimulation at a target site. They in fact behave as actual nanotransducers, converting energy stemming from the external magnetic field into heat and mechanical forces, which act as signals for therapeutic processes such as hyperthermia and controlled drug release. Magnetic nanoparticles are a noninvasive tool that enables the remote activation of biological processes, besides behaving as formidable tracers for different imaging modalities, thus allowing to simultaneously carry out diagnosis and therapy. In view of all this, owing to their multifunctional and multitasking nature, magnetic nanoparticles are already one of the most important nanotechnological protagonists in medicine and biology, enabling an actual theranostic approach in many pathological conditions. In this Concept, we first provide a brief introduction on some physical properties of magnetic materials and on important features that determine the physical properties of magnetic nanoparticles. Thereafter, we will consider some major biomedical applications: hyperthermia, drug delivery/release, and nanoparticle-mediated control of biological processes, even at subcellular level.Magnetic nanoparticles are among the most popular nanomaterials used in the biomedical field. This Concept provides a brief introduction on important features that determine the physical properties of magnetic nanoparticles and summarizes their application in hyperthermia, drug delivery/release, and for nanoparticle-mediated control of biological processes.
      PubDate: 2017-10-16T06:40:27.511282-05:
      DOI: 10.1002/chem.201703660
  • Regioselective Direct C-Alkenylation of Indoles
    • Authors: Marino Petrini
      Pages: 16115 - 16151
      Abstract: The direct introduction of alkenyl groups into the indole framework avoiding its preliminary functionalization can be carried out using different synthetic strategies. Transition-metal complexes facilitate the C−H activation of indoles or alkenes allowing an efficient Csp2- Csp2 bond formation. The hydroindolation of alkynes catalyzed by the same metal complexes or various acidic promoters can also be pursued for the alkenylation process. Conjugate addition of electron-poor alkenes and direct condensation of carbonyl derivatives with indoles are also of interest for this purpose. The regiochemical control can be exploited using the intrinsic C-3 reactivity of the indole ring. The introduction of a suitable directing group at the nitrogen atom allows the preparation of C-2 alkenylated derivatives by transition metal catalyzed reactions. This review collects the fundamental contributions in this field reported in literature during the last fifteen years.Regioselectivity à la carte: The alkenylation of indoles can be efficiently addressed by a suitable choice of the substituent at the nitrogen atom. Hydrogen and simple alkyl groups drive the alkenylation at C-3. Conversely, acyl groups and nitrogen-containing heteroaromatic substituents favor the C-2 alkenylated derivatives in metal-catalyzed reactions. The nature of the metal complex employed also plays a crucial role in the regioselectivity.
      PubDate: 2017-09-06T09:31:29.098707-05:
      DOI: 10.1002/chem.201702124
  • Tuning Electron Flux through Nitrogenase with Methanogen Iron Protein
    • Authors: Caleb J. Hiller; Martin T. Stiebritz, Chi Chung Lee, Jasper Liedtke, Yilin Hu
      Pages: 16152 - 16156
      Abstract: Nitrogenase uses a reductase component called Fe protein to deliver electrons to its catalytic partner for substrate reduction. The essential role of Fe protein in catalysis makes it an ideal target for regulating the electron flux and enzymatic activity of nitrogenase without perturbing the cofactor site. This work reports that hybrids between the Fe protein homologs of Methanosarcina acetivorans and the catalytic components of Azotobacter vinelandii can trap substrate CO through reduced electron fluxes. In addition, homology modeling/in silico docking is used to define markers for binding energy and specificity between the component proteins that correlate with the experimentally determined activities. This homologue-based approach could be further developed to allow identification or design of hybrids between homologous nitrogenase components for mechanistic investigations of nitrogenase through capture of substrates/ intermediates or for transgenic expression of nitrogenase through synthetic biology.A homologue-based approach facilitates capture of multiple CO molecules at the nitrogenase cofactor site through reduction of the electron flow through a nitrogenase hybrid between homologous component proteins, suggesting the utility of this approach in tuning electron fluxes to enable trapping of substrates and relevant intermediates for mechanistic investigations of this enzyme.
      PubDate: 2017-10-06T05:40:38.665356-05:
      DOI: 10.1002/chem.201704378
  • Increased Conformational Flexibility of a Macrocycle–Receptor Complex
           Contributes to Reduced Dissociation Rates
    • Authors: Adrian Glas; Eike-Christian Wamhoff, Dennis M. Krüger, Christoph Rademacher, Tom N. Grossmann
      Pages: 16157 - 16161
      Abstract: Constraining a peptide in its bioactive conformation by macrocyclization represents a powerful strategy to design modulators of challenging biomolecular targets. This holds particularly true for the development of inhibitors of protein-protein interactions which often involve interfaces lacking defined binding pockets. Such flat surfaces are demanding targets for traditional small molecules rendering macrocyclic peptides promising scaffolds for novel therapeutics. However, the contribution of peptide dynamics to binding kinetics is barely understood which impedes the design process. Herein, we report unexpected trends in the binding kinetics of two closely related macrocyclic peptides that bind their receptor protein with high affinity. Isothermal titration calorimetry, 19F NMR experiments and molecular dynamics simulations reveal that increased conformational flexibility of the macrocycle–receptor complex reduces dissociation rates and contributes to complex stability. This observation has impact on macrocycle design strategies that have so far mainly focused on the stabilization of bioactive ligand conformations.More flexible, more stable: Unexpected trends in the binding kinetics of two closely related macrocyclic peptides are reported. Isothermal titration calorimetry, 19F NMR experiments and molecular dynamics simulations reveal that increased conformational flexibility of the macrocycle–receptor complex reduces dissociation rates and contributes to complex stability.
      PubDate: 2017-08-30T11:10:30.631246-05:
      DOI: 10.1002/chem.201702776
  • Saccharide-Containing Dynamic Proteoids
    • Authors: Yun Liu; Marc C. A. Stuart, Martin D. Witte, Eric Buhler, Anna K. H. Hirsch
      Pages: 16162 - 16166
      Abstract: Dynamic proteoids are dynamic covalent analogues of proteins, which can be used as new adaptive biomaterials. We designed and synthesized a range of sugar-containing dynamic proteoid biodynamers based on the polycondensation of different types of amino acid and dipeptide hydrazides with a biological aliphatic dialdehyde and a nonbiological aromatic dialdehyde. By using the saccharide-based dialdehyde, the biocompatibility of biodynamers should be enhanced compared to previously reported biodynamers.Hybrids of dynamic proteoids and glycodynamers: A series of sugar-containing dynamic proteoid biodynamers were designed and prepared through the polycondensation of different types of amino acid and dipeptide hydrazides with a biological aliphatic dialdehyde in aqueous medium under mild acid conditions (see Scheme).
      PubDate: 2017-10-25T10:01:16.538926-05:
      DOI: 10.1002/chem.201703584
  • Abnormal Tin–Boron Exchange in the Attempted Synthesis of a
           Borylated Borole
    • Authors: Holger Braunschweig; Michael Dömling, Stephanie Kachel, Hauke Kelch, Thomas Kramer, Ivo Krummenacher, Carsten Lenczyk, Shujuan Lin, Zhenyang Lin, Christian Possiel, Krzysztof Radacki
      Pages: 16167 - 16170
      Abstract: Boroles are important motifs within functional materials. With the aim to prepare a pinacolboryl-substituted derivative, the metallacycle transfer from corresponding zirconium and tin precursors has been explored. We show that the reaction of 1,1-dimethyl-2,3,4,5-tetrapinacolborylstannole with dichloro(phenyl)borane does not provide the desired borole, but instead a stannyl-substituted 1-chloroboracyclopent-3-ene. Spectroscopic and structural details of this highly functionalized boracycle indicate that intramolecular interactions between the tin and oxygen atoms of the boryl substituents may account for the unexpected outcome of the tin-boron exchange reaction.Don′t be a stannole! The tin–boron exchange reaction of 1,1-dimethyl-2,3,4,5-tetrapinacolborylstannole with dichloro(phenyl)borane was shown to give a stannyl-substituted 1-chloroboracyclopent-3-ene instead of the desired borole (see graphic). Spectroscopic and structural properties of this highly functionalized boracycle are presented together with initial results of its reactivity.
      PubDate: 2017-10-25T09:57:00.774906-05:
      DOI: 10.1002/chem.201703810
  • A Solid Iridium Catalyst for Diastereoselective Hydrogenation
    • Authors: Iuliia Romanenko; Louis Jaffeux, Laurent Veyre, Emmanuel Lacôte, Valérie Meille, Chloé Thieuleux
      Pages: 16171 - 16173
      Abstract: An Ir(NHC) supported catalyst is used in the selective hydrogenation of terpinen-4-ol to cis p-menthan-4-ol. Its activity, selectivity and stability are compared to those of a homogeneous homologue [IrCl(COD)MesImPr] and to a commercial Pd/C. The solid Ir catalyst is much more selective than the Pd catalyst (92 vs. 42 % at 80 °C) but also more active, more selective and more stable than the iridium complex in solution. For the first time, a supported catalyst shows an enhanced activity with respect to a complex in a diastereoselective hydrogenation reaction.Cool cat: An Ir(NHC)-based hybrid material is used in a diastereoselective hydrogenation. It selectively hydrogenates terpinen-4-ol to cis p-menthan-4-ol. It is much more selective than a commercial Pd/C catalyst. It is more active, selective and stable than the homogeneous homologue in solution.
      PubDate: 2017-10-25T09:56:28.034833-05:
      DOI: 10.1002/chem.201703872
  • Microwave-Assisted Rapid One-Pot Synthesis of Fused and Non-Fused Indoles
           and 5-[18F]Fluoroindoles from Phenylazocarboxylates
    • Authors: Jasmin Krüll; Anja Hubert, Natascha Nebel, Olaf Prante, Markus R. Heinrich
      Pages: 16174 - 16178
      Abstract: Substituted indoles can be prepared from phenylazocarboxylates through a rapid one-pot sequence featuring a microwave-assisted Fischer indole synthesis as a key step. Considering that the phenylazocarboxylates may beforehand be modified by mild nucleophilic aromatic substitution, including the introduction of [18F]fluoride, the overall strategy offers an attractive new access to 5-[18F]fluoroindoles.On the fast track: Phenylazocarboxylates can be converted to indoles via a rapid one-pot reaction comprising a microwave-assisted Fischer indole synthesis. The advantage that phenylazocarboxylates can beforehand be modified by mild nucleophilic aromatic substitution also enables an application of the strategy for the preparation of 5-[18F]fluoroindoles.
      PubDate: 2017-10-23T07:46:33.767141-05:
      DOI: 10.1002/chem.201703890
  • High-Performance Non-Enzyme Hydrogen Peroxide Detection in Neutral
           Solution: Using a Nickel Borate Nanoarray as a 3D Electrochemical Sensor
    • Authors: Zao Wang; Fengyu Xie, Zhiang Liu, Gu Du, Abdullah M. Asiri, Xuping Sun
      Pages: 16179 - 16183
      Abstract: It is highly attractive to construct natural enzyme-free nanoarray architecture as a 3D catalyst for hydrogen peroxide detection due to its great specific surface area and easy accessibility to target molecules. In this communication, we demonstrate that nickel borate nanoarray supported on carbon cloth (Ni−Bi/CC) behaves as an efficient catalyst electrode for H2O2 electro-reduction in neutral media. As a non-enzymatic electrochemical H2O2 sensor, such Ni−Bi/CC shows superior sensing performances with a fast response time (less than 3 s), a low detection limit (0.85 nm, S/N=3), and a high sensitivity (18320 μA mm cm−2). Importantly, it also demonstrates favourable reproducibility and long-term stability.A nickel borate nanoarray on carbon cloth (Ni−Bi/CC) behaves as an efficient catalyst electrode for H2O2 electroreduction in neutral media. As a non-enzymatic electrochemical H2O2 sensor, such Ni−Bi/CC shows superior sensing performances with a fast response time (less than 3 s), a low detection limit (0.85 nm, S/N=3), and a high sensitivity (18320 μA mm cm−2).
      PubDate: 2017-10-23T07:46:43.073001-05:
      DOI: 10.1002/chem.201704038
  • Novel Fluorophores based on Regioselective Intramolecular Friedel–Crafts
           Acylation of the Pyrene Ring Using Triflic Acid
    • Authors: Tanguy Jousselin-Oba; Kamal Sbargoud, Gianfranco Vaccaro, Francesco Meinardi, Abderrahim Yassar, Michel Frigoli
      Pages: 16184 - 16188
      Abstract: The extension of the pyrene ring from dimethyl 2,2′-(pyrene-1,6-diyl)dibenzoate derivatives by an intramolecular Friedel–Crafts acylation can be realized in an efficient and regioselective manner using triflic acid as proton source. Naphtho-tetracenone derivatives are obtained in high yields at room temperature while Bis-tetracene-diones are prepared upon heating. Both products display interesting fluorescence properties in the visible range with quantum yields varying from 50 to 60 %.Thanks to TfOH: The extension of the pyrene ring from dimethyl 2,2′-(pyrene-1,6-diyl)dibenzoate derivatives by an intramolecular Friedel–Crafts acylation can be realized in an efficient and regioselective manner using triflic acid as proton source. Naphtho-tetracenone derivatives are obtained in high yields at room temperature while Bis-tetracene-diones are prepared upon heating. Both products display interesting fluorescence properties in the visible range with quantum yields varying from 50 to 60 %.
      PubDate: 2017-10-24T11:37:41.586341-05:
      DOI: 10.1002/chem.201704116
  • Total Synthesis of Strychnine
    • Authors: Geun Seok Lee; Gil Namkoong, Jisook Park, David Y.-K. Chen
      Pages: 16189 - 16193
      Abstract: The total synthesis of the flagship Strychnos indole alkaloid, strychnine, has been accomplished. The developed synthetic sequence features a novel vinylogous 1,4-addition, a challenging iodinium salt mediated silyl enol ether arylation, a palladium-catalyzed Heck reaction, and a streamlined late-stage conversion to strychnine. Furthermore, an application of asymmetric counterion-directed catalysis (ACDC) in the context of target-oriented organic synthesis has been rendered access to an optically active material. The synthetic sequence described herein represents the most concise entry to optically active strychnine to date.What′s your poison' An expedient total synthesis of strychnine has been accomplished through a newly developed reaction sequence involving a catalytic asymmetric counteranion-directed vinylogous 1,4-addition, a silyl enol ether quaternary arylation, and an intramolecular Heck reaction.
      PubDate: 2017-10-25T09:56:15.768333-05:
      DOI: 10.1002/chem.201704455
  • Thieno-Fused Subporphyrazines: A New Class of Light Harvesters
    • Authors: Henrik Gotfredsen; Freja Eilsø Storm, Alberto Viñas Muñoz, Marco Santella, Anders Kadziola, Ole Hammerich, Kurt V. Mikkelsen, Mogens Brøndsted Nielsen
      Pages: 16194 - 16198
      Abstract: Boron subphthalocyanines comprised of three isoindole units bridged by aza-linkages are attractive light harvesters on account of their intense low-energy absorptions. Herein, we present a class of related compounds, in which one or two isoindole units are substituted for thieno[3,4-c]pyrrole units – thieno-fused subporphyrazines. Such changes have remarkable consequences for the optical properties, as was revealed by combined experimental and theoretical studies. Thus, we find that the lowest-energy absorptions cover a much broader region with a significantly redshifted end-absorption and without compromising the absorption intensities. Thieno-fused subporphyrazines also underwent more readily oxidation and reduction, indicating an increased HOMO energy and decreased LUMO energy. In addition, they were found to readily co-crystallize with Buckminsterfullerene, C60. Altogether, these findings render this new class of chromophores attractive candidates for light-harvesting applications.Light harvesting: A class of related compounds, in which one or two isoindole units are substituted for thieno[3,4-c]pyrrole units – thieno-fused subporphyrazines, is presented. Such changes have remarkable consequences for the optical properties, as was revealed by combined experimental and theoretical studies (see scheme).
      PubDate: 2017-10-23T07:51:58.126027-05:
      DOI: 10.1002/chem.201704551
  • Preorganized AgI Bimetallic Precursor with Labile Diphosphorus Ligands for
           a Programmed Synthesis of Organometallic–Organic Hybrid Polymers
    • Authors: Mehdi Elsayed Moussa; Michael Seidl, Gábor Balázs, Manfred Zabel, Alexander V. Virovets, Bianca Attenberger, Andrea Schreiner, Manfred Scheer
      Pages: 16199 - 16203
      Abstract: An AgI dimer capped with labile organometallic diphosphorus ligands [Cp2Mo2(CO)4(η2-P2)] (Cp=C5H5) acts as a highly pre-organized molecular precursor to direct the construction of 1D or 2D, and 3D organometallic–organic hybrid coordination polymers upon reaction with ditopic pyridine-based linkers. The formation of the supramolecular aggregates can be controlled by the stoichiometry of the organic molecules, and the mechanism is supported by DFT calculations.Hybrid Coordinates: An AgI dimer capped with labile η2-coordinated organometallic diphosphorus ligands [Cp2Mo2(CO)4(η2-P2)] acts as a “preprogrammed” molecular precursor to direct a selective construction of one- and multi-dimensional organometallic–organic hybrid polymers, respectively, upon reaction with ditopic pyridine-based linkers.
      PubDate: 2017-10-25T09:56:07.532244-05:
      DOI: 10.1002/chem.201704582
  • Rational Design of a Bifunctional, Two-Fold Interpenetrated
           ZnII-Metal–Organic Framework for Selective Adsorption of CO2 and
           Efficient Aqueous Phase Sensing of 2,4,6-Trinitrophenol
    • Authors: Sandeep Singh Dhankhar; Nayuesh Sharma, Sandeep Kumar, T. J. Dhilip Kumar, C. M. Nagaraja
      Pages: 16204 - 16212
      Abstract: A bifunctional, microporous ZnII metal–organic framework, [Zn2(NH2BDC)2(dpNDI)]n (MOF1) (where, NH2BDC=2-aminoterephthalic acid, dpNDI=N,N′-di(4-pyridyl)-1,4,5,8-naphthalenediimide) has been synthesized solvothermally. MOF1 shows an interesting two-fold interpenetrated, 3D pillar-layered framework structure composed of two types of 1D channels with dimensions of approximately 2.99×3.58 Å and 4.58×5.38 Å decorated with pendent −NH2 groups. Owing to the presence of a basic functionalized pore surface, MOF1 exhibits selective adsorption of CO2 with high value of heat of adsorption (Qst=46.5 kJ mol−1) which is further supported by theoretically calculated binding energy of 48.4 kJ mol−1. Interestingly, the value of Qst observed for MOF1 is about 10 kJ mol−1 higher than that of analogues MOF with the benzene-1,4-dicarboxylic acid (BDC) ligand, which establishes the critical role of the −NH2 group for CO2 capture. Moreover, MOF1 exhibits highly selective and sensitive sensing of the nitroaromatic compound (NAC), 2,4,6-trinitrophenol (TNP) over other competing NACs through a luminescence quenching mechanism. The observed selectivity for TNP over other nitrophenols has been correlated to stronger hydrogen bonding interaction of TNP with the basic −NH2 group of MOF1, which is revealed from DFT calculations. To the best of our knowledge, MOF1 is the first example of an interpenetrated ZnII-MOF exhibiting selective adsorption of CO2 as well as efficient aqueous-phase sensing of TNP; investigated through combined experimental and theoretical studies.Separate and sense: Construction of a microporous ZnII-based metal–organic framework, [Zn2(NH2BDC)2(dpNDI)]n (MOF1) exhibiting two-fold interpenetrated, 3D pillar-layered framework structure composed of two types of 1D channels decorated with pendent −NH2 group is demonstrated. MOF1 represents a rare example of an interpenetrated ZnII-MOF exhibiting selective adsorption of CO2 as well as efficient aqueous-phase sensing of 2,4,6-trinitrophenol investigated through combined experimental and theoretical studies.
      PubDate: 2017-10-23T07:51:50.629116-05:
      DOI: 10.1002/chem.201703384
  • Robust Macroscopic 3D Sponges of Manganese Oxide Molecular Sieves
    • Authors: Zhenxin Liu; Depeng Wu, Xuehui Guo, Shaoming Fang, Lizhen Wang, Yu Xing, Steven L. Suib
      Pages: 16213 - 16218
      Abstract: The construction of macroscopic 3D sponges is of great technological importance for various applications. An outstanding challenge is the facile fabrication of sponges with the desirable combination of good stability, high electrical conductivity, and absorption ability. Here free-standing 3D OMS-2 sponges are demonstrated, with various densities, which possess a combination of desirable physical properties including high porosity, robustness, permeability, recyclability, high electrical conductivity, and selective water absorption in preference to oil. Some of these properties have systematic trends with various densities. The stress of the OMS-2 sponge, made by nanowire-based freeze-drying process, is four orders of magnitude higher than that made by calcination-related process. These new materials should find practical applications in environmental, catalysis, sensing, absorption, and energy storage, particularly in the removal of water spill cleanup, and beyond.Suck it up: Free-standing 3D OMS-2 sponges with various densities were developed and demonstrated outstanding features, including good mechanical properties, facile preparation, high electrical conductivity, high porosity, permeability, recyclability, as well as selective water absorption in preference to oil. Some of these properties exhibit systematic trends with various densities.
      PubDate: 2017-09-18T11:27:27.55687-05:0
      DOI: 10.1002/chem.201702787
  • Laying Waste to Mercury: Inexpensive Sorbents Made from Sulfur and
           Recycled Cooking Oils
    • Authors: Max J. H. Worthington; Renata L. Kucera, Inês S. Albuquerque, Christopher T. Gibson, Alexander Sibley, Ashley D. Slattery, Jonathan A. Campbell, Salah F. K. Alboaiji, Katherine A. Muller, Jason Young, Nick Adamson, Jason R. Gascooke, Deshetti Jampaiah, Ylias M. Sabri, Suresh K. Bhargava, Samuel J. Ippolito, David A. Lewis, Jamie S. Quinton, Amanda V. Ellis, Alexander Johs, Gonçalo J. L. Bernardes, Justin M. Chalker
      Pages: 16219 - 16230
      Abstract: Mercury pollution threatens the environment and human health across the globe. This neurotoxic substance is encountered in artisanal gold mining, coal combustion, oil and gas refining, waste incineration, chloralkali plant operation, metallurgy, and areas of agriculture in which mercury-rich fungicides are used. Thousands of tonnes of mercury are emitted annually through these activities. With the Minamata Convention on Mercury entering force this year, increasing regulation of mercury pollution is imminent. It is therefore critical to provide inexpensive and scalable mercury sorbents. The research herein addresses this need by introducing low-cost mercury sorbents made solely from sulfur and unsaturated cooking oils. A porous version of the polymer was prepared by simply synthesising the polymer in the presence of a sodium chloride porogen. The resulting material is a rubber that captures liquid mercury metal, mercury vapour, inorganic mercury bound to organic matter, and highly toxic alkylmercury compounds. Mercury removal from air, water and soil was demonstrated. Because sulfur is a by-product of petroleum refining and spent cooking oils from the food industry are suitable starting materials, these mercury-capturing polymers can be synthesised entirely from waste and supplied on multi-kilogram scales. This study is therefore an advance in waste valorisation and environmental chemistry.Laying waste to mercury pollution: A sustainable rubber made from sulfur and recycled cooking oil is a general sorbent for diverse forms of mercury pollution.
      PubDate: 2017-08-30T11:22:00.953507-05:
      DOI: 10.1002/chem.201702871
  • Control of Reversible Activation Dynamics of
           [Ru{η6:κ1-C6H5(C6H4)NH2}(XY)]n+ and the Effect of Chelating-Ligand
    • Authors: Francisco Martínez-Peña; Ana M. Pizarro
      Pages: 16231 - 16241
      Abstract: The potential use of organoruthenium complexes as anticancer drugs is well known. Herein, a family of activatable tethered ruthenium(II) arene complexes of general formula [Ru{η6:κ1-C6H5(C6H4)NH2}(XY)]n+ (closed tether ring) bearing different chelating XY ligands (XY=aliphatic diamine, phenylenediamine, oxalato, bis(phosphino)ethane) is reported. The activation of these complexes (closed- to open-tether conversion) occurs in methanol and DMSO at different rates and to different reaction extents at equilibrium. Most importantly, RuII-complex activation (cleavage of the Ru−Ntether bond) occurs in aqueous solution at high proton concentration (upon Ntether protonation). The activation dynamics can be modulated by rational variation of the XY chelating ligand. The electron-donating capability and steric hindrance of XY have a direct impact on the reactivity of the Ru−N bond, and XY=N,N′-dimethyl-, N,N′-diethyl-, and N,N,N′,N′-tetramethylethylenediamine afford complexes that are more prone to activation. Such activation in acidic media is fully reversible, and proton concentration also governs the deactivation rate, that is, tether-ring closure slows down with decreasing pH. Interaction of a closed-tether complex and its open-tether counterpart with 5′-guanosine monophosphate revealed selectivity of the active (open) complex towards interaction with nucleobases. This work presents ruthenium tether complexes as exceptional pH-dependent switches with potential applications in cancer research.End of the tether: A new family of activatable ruthenium tethered arene complexes was synthesized and characterized. These metal complexes can reversibly open and close a vacant position for interaction with biomolecules. Both the activation and inactivation processes are pH-dependent. This class of RuII tether complexes represent a first step towards rational design of pH-responsive organometallic switches with promising applications in cancer research.
      PubDate: 2017-09-12T02:03:29.776533-05:
      DOI: 10.1002/chem.201701681
  • Component-Customizable Porous Rare-Earth-Based Colloidal Spheres towards
           Highly Effective Catalysts and Bioimaging Applications
    • Authors: Cheng Chao Li; Xianhong Rui, Weifeng Wei, Libao Chen, Yan Yu
      Pages: 16242 - 16248
      Abstract: Multicomponent porous colloidal spheres are of interest because they not only show a combination of the properties associated with all different components, but also usually present synergy effects. However, a combination of different components in a single porous sphere is still greatly challenged due to the different precipitation behaviors of each component. In this work, we have developed a general synthetic route to prepare several categories of porous monodisperse rare-earth (RE)-based colloidal spheres with customizable elemental compositions and a uniform element distribution. The two-step synthetic strategy is based on the integration of coordination chemistry precipitation of RE ions and a subsequent ion-exchange process, which steers clear of obstacles, such as differences in solubility product constant, that are to be found in traditional co-precipitation methods. Our approach provides a new mixing mechanism to realize homogeneous distribution of each element within the porous spheres. An array of binary, ternary, and even senary RE colloidal porous spheres with diameters of 500 nm to 700 nm has been successfully synthesized. Taking advantage of their good dispersibility, porosity, and customizable components, these porous RE oxide spheres show excellent catalytic activity for the reduction of 4-nitrophenol, and promising application in single-phase multifunctional bioprobes.Doing a two-step with rare earths! A general synthetic route to prepare several categories of porous monodisperse rare-earth (RE)-based colloidal spheres was developed. The two-step synthetic strategy is based on the integration of coordination chemistry precipitation of RE ions and subsequent ion-exchange process, which steers clear of obstacle from differences in solubility product constant in traditional co-precipitation methods.
      PubDate: 2017-10-26T08:31:36.311661-05:
      DOI: 10.1002/chem.201702161
  • Dual-Pore Carbon Shells for Efficient Removal of Humic Acid from Water
    • Authors: Hongxia Yu; Qiao Zhang, Michael Dahl, Ji Bong Joo, Xin Wang, Lianjun Wang, Yadong Yin
      Pages: 16249 - 16256
      Abstract: A template-mediated process for the preparation of mesoporous carbon shells with high surface area, dual-pore structure, and excellent performance in the adsorption of humic acid is reported. Their synthesis involves templating phenolic resin against wrinkled silica nanospheres, subsequent carbonization under Ar atmosphere, and final release of dual-pore mesoporous carbon shells by etching the silica templates. An additional silica layer was used to protect the phenolic resin from aggregation during carbonization, and its subsequent removal gives the carbon shells a hydrophilic surface, which significantly improves their dispersity in aqueous media. When used as adsorbents for humic acid removal, the as-prepared dual-pore mesoporous carbon shells show superior adsorption performance to activated carbon.Mesoporous carbon adsorbents: A template-mediated process for the preparation of mesoporous carbon shells with high surface area, dual-pore structure, and excellent performance in the adsorption of humic acid was developed (see figure). The as-prepared dual-pore mesoporous carbon shells show superior adsorption performance to activated carbon in the removal of humic acid from water.
      PubDate: 2017-10-25T10:01:52.795104-05:
      DOI: 10.1002/chem.201702318
  • Bead-Level Characterization of Early-Stage Amyloid β42 Aggregates:
           Nuclei and Ionic Concentration Effects
    • Authors: Dingkun Hu; Wei Zhao, Yong Zhu, Hongqi Ai, Baotao Kang
      Pages: 16257 - 16273
      Abstract: A growing body of evidence shows that soluble β-amyloid (Aβ) aggregates, oligomers, and even protofibrils, may be more neurotoxic than fibrils. Here, we employ a coarse grain model to investigate the aggregation of 75mer Aβ42 oligomers and the salt effect, the cornerstone of fibril evolution. We find that the oligomer morphologies generated by seventy-five monomers or mixed by both fifty monomers and five preset pentameric nuclei are different (spherical vs. bar-/disk-shaped) and are characterize by a full of coil content (former) and >70 % β-turn content (latter), indicating a novel role of the nuclei played in the early aggregation stage. The aggregation for the former oligomer adopts a master-nucleus mechanism, whereas for the latter combination of monomers and pentamers a multi-nuclei one is found. The random salt ions will distribute around the aggregates to form several ion shells as the aggregation develops. A unique two-fold gap between the shells is observed in the system containing 100 mm NaCl, endowing the physiological salt concentration with special implications. Meanwhile, an accurate ion–solute cutoff distance (0.66 nm) is predicted, and recommended to apply to many other aggregated biomolecular systems. The present distribution scenario of ions can be generalized to other aggregated systems, although it is strictly dependent on the identity of a specific aggregate, such as its charge and composition.Everything changes: The nuclei and salt ions play different roles in the β-amyloid (Aβ) aggregation process. The aggregation mechanism can change from a master-nucleus to a multi-nuclei mechanism, whereas the salt ions alter the composition of the secondary structure and the oligomer morphology by covering the aggregate surface with several shells formed (see figure).
      PubDate: 2017-10-24T06:26:47.169764-05:
      DOI: 10.1002/chem.201702388
  • In-Situ and Real-time Monitoring of Mechanochemical Preparation of
           Li2Mg(NH2BH3)4 and Na2Mg(NH2BH3)4 and Their Thermal Dehydrogenation
    • Authors: Nikola Biliškov; Andreas Borgschulte, Krunoslav Užarević, Ivan Halasz, Stipe Lukin, Sanja Milošević, Igor Milanović, Jasmina Grbović Novaković
      Pages: 16274 - 16282
      Abstract: For the first time, in situ monitoring of uninterrupted mechanochemical synthesis of two bimetallic amidoboranes, M2Mg(NH2BH3)4 (M=Li, Na), by means of Raman spectroscopy, has been applied. This approach allowed real-time observation of key intermediate phases, and a straightforward follow-up of the reaction course. Detailed analysis of time-dependent spectra revealed a two-step mechanism through MNH2BH3⋅NH3BH3 adducts as key intermediate phases which further reacted with MgH2, giving M2Mg(NH2BH3)4 as final products. The intermediates partially take a competitive pathway toward the oligomeric M(BH3NH2BH2NH2BH3) phases. The crystal structure of the novel bimetallic amidoborane Li2Mg(NH2BH3)4 was solved from high-resolution powder diffraction data and showed an analogous metal coordination to Na2Mg(NH2BH3)4, but a significantly different crystal packing. Li2Mg(NH2BH3)4 thermally dehydrogenates releasing highly pure H2 in the amount of 7 wt.%, and at a lower temperature then its sodium analogue, making it significantly more viable for practical applications.Have a ball: In situ monitoring of the mechanochemical synthesis of bimetallic amidoboranes allowed real-time observation of key intermediate phases, and a straightforward follow-up of the reaction course. The crystal structure of the novel bimetallic amidoborane Li2Mg(NH2BH3)4 was solved from powder diffraction data and showed an analogous metal coordination to Na2Mg(NH2BH3)4, but a significantly different crystal packing.
      PubDate: 2017-10-23T08:25:52.907132-05:
      DOI: 10.1002/chem.201702665
  • Heterovalent Glycodendrimers as Epitope Carriers for Antitumor Synthetic
    • Authors: Carlo Pifferi; Baptiste Thomas, David Goyard, Nathalie Berthet, Olivier Renaudet
      Pages: 16283 - 16296
      Abstract: The large majority of TACA-based (TACA=Tumor-Associated Carbohydrate Antigens) antitumor vaccines target only one carbohydrate antigen, thereby often resulting in the incomplete destruction of cancer cells. However, the morphological heterogeneity of the tumor glycocalix, which is in constant evolution during malignant transformation, is a crucial point to consider in the design of vaccine candidates. In this paper, an efficient synthetic strategy based on orthogonal chemoselective ligations to prepare fully synthetic glycosylated cyclopeptide scaffolds grafted with both Tn and TF antigen analogues is reported. To evaluate their ability to be recognized as tumor antigens, direct interaction ELISA assays have been performed with the anti-Tn monoclonal antibody 9A7. Although both heterovalent structures showed binding capacities with 9A7, the presence of the second TF epitope did not interfere with the recognition of Tn except in one epitope arrangement. This heterovalent glycosylated structure thus represents an attractive epitope carrier to be further functionalized with T-cell peptide epitopes.An efficient synthetic strategy based on orthogonal chemoselective ligations to prepare fully synthetic glycosylated cyclopeptide scaffolds grafted with both Tn and TF antigen analogues is reported. To evaluate their ability to be recognized as tumor antigens, direct interaction ELISA assays have been performed with the anti-Tn monoclonal antibody 9A7 (see figure).
      PubDate: 2017-10-25T10:01:04.944436-05:
      DOI: 10.1002/chem.201702708
  • Supramolecular Hydro- and Ionogels: A Study of Their Properties and
           Antibacterial Activity
    • Authors: Carla Rizzo; Rossella Arrigo, Nadka Tz. Dintcheva, Giuseppe Gallo, Francesco Giannici, Renato Noto, Alberto Sutera, Paola Vitale, Francesca D'Anna
      Pages: 16297 - 16311
      Abstract: Diimidazolium-based organic salts, bearing peptides or amino acids as anions have been synthesised and tested for their gelling ability in biocompatible solvents. These low molecular weight salts were successfully used as gelators in phosphate buffered saline (PBS) solution and ionic liquids. Then, the properties of the obtained soft materials were analysed in terms of melting temperature and gel strength as accounted for by rheological investigations. The gel-phase formation was studied by using UV/Vis and resonance light scattering measurements, whereas the morphology of the soft materials was analysed by using polarised optical microscopy and scanning electron microscopy. To get information about the organisation of the gelator in the gelatinous matrix, X-ray diffraction measurements were performed both on the neat gelators and their gels. The results collected show that the properties of the gel phases, like the thermal stability, the self-repairing ability, the resistance to flow as well as the morphology, are dependent on the nature of the anion. Furthermore, bioassays revealed that the obtained diimidazolium organic salts possessed antimicrobial activity, against gram-negative and gram-positive tester strains. In particular and noteworthy, the diimidazolium organic salts exert a bactericidal capability, which was retained even if they are included in the gel phase. Thus, a novel kind of bioactive soft material was obtained that could be fruitfully employed as a non-covalent coating exerting antibacterial capability.Antibacterial gels: The gels presented have excellent properties in terms of their mechanical strength, thermal stability and response to external stimuli in relation to the gelation solvent and the anion of the gelator. The gelators and gels exert antibacterial activity against gram-positive and gram-negative strains (see figure). These new supramolecular gels could represent a great potential as coating materials.
      PubDate: 2017-10-26T08:32:38.387956-05:
      DOI: 10.1002/chem.201702937
  • Rutile TiO2 Mesocrystals as Sulfur Host for High-Performance
           Lithium–Sulfur Batteries
    • Authors: Qingqing Sun; Kaixiang Chen, Yubin Liu, Yafeng Li, Mingdeng Wei
      Pages: 16312 - 16318
      Abstract: Although lithium–sulfur (Li–S) batteries are among the most promising rechargeable batteries in the field of energy-storage devices, their poor cycling performance restricts their potential applications. Polar materials can improve the cycling stability owing to their inherent strong chemical interaction with polysulfides. Herein, novel rutile TiO2 mesocrystals (RTMs) are employed as the host for sulfur in Li–S batteries; the RTMs display a stable cycling performance with a capacity retention of 64 % and a small average capacity decay rate of 0.12 % per cycle over 300 cycles at 1 C rate. The good electrochemical properties are attributed to the interior ordered nanopores of the RTMs, which can effectively limit the dissolution of polysulfides, and the ultrafine nanowires in RTMs, which shorten the path for lithium-ion transport effectively.Lithium–sulfur batteries: Rutile TiO2 mesocrystals are employed as an effective host in Li–S batteries. The material displays a stable cycling performance owing to its unique nanostructure and the reduced dissolution of polysulfides (see figure).
      PubDate: 2017-10-30T07:50:19.650811-05:
      DOI: 10.1002/chem.201703130
  • Unexpected Rotamerism at the Origin of a Chessboard Supramolecular
           Assembly of Ruthenium Phthalocyanine
    • Authors: Giuseppe Mattioli; Rosanna Larciprete, Paola Alippi, Aldo Amore Bonapasta, Francesco Filippone, Paolo Lacovig, Silvano Lizzit, Anna Maria Paoletti, Giovanna Pennesi, Fabio Ronci, Gloria Zanotti, Stefano Colonna
      Pages: 16319 - 16327
      Abstract: We have investigated the formation and the properties of ultrathin films of ruthenium phthalocyanine (RuPc)2 vacuum deposited on graphite by scanning tunneling microscopy and synchrotron photoemission spectroscopy measurements, interpreted in close conjunction with ab initio simulations. Thanks to its unique dimeric structure connected by a direct Ru−Ru bond, (RuPc)2 can be found in two stable rotameric forms separated by a low-energy barrier. Such isomerism leads to a peculiar organization of the molecules in flat, horizontal layers on the graphite surface, characterized by a chessboard-like alternation of the two rotamers. Moreover, the molecules are vertically connected to form π-stacked columnar pillars of akin rotamers, compatible with the high conductivity measured in (RuPc)2 powders. Such features yield an unprecedented supramolecular assembly of phthalocyanine films, which could open interesting perspectives toward the realization of new architectures of organic electronic devices.An unexpected chessboard-like pattern appears in ultrathin films of ruthenium phthalocyanine deposited on graphite. The comparison between STM and PES measurements, interpreted in close conjunction with DFT simulations, unveils the properties of a peculiar supramolecular assembly: two stable isomers concur in the formation of the organic film, driven by strong non-covalent intermolecular interactions that act within a single molecular layer and are extended to the assembly of multilayered structures.
      PubDate: 2017-11-02T04:57:01.744857-05:
      DOI: 10.1002/chem.201703255
  • Role of the Bridging Group in Bis-Pyridyl Ligands: Enhancing Both the
           Photo- and Electroluminescent Features of Cationic (IPr)CuI Complexes
    • Authors: Margaux Elie; Michael D. Weber, Florent Di Meo, Fabien Sguerra, Jean-François Lohier, Robert B. Pansu, Jean-Luc Renaud, Matthieu Hamel, Mathieu Linares, Rubén D. Costa, Sylvain Gaillard
      Pages: 16328 - 16337
      Abstract: We report on the benefits of changing the bridging group X of bis-pyridyl ligands, that is, Py-X-Py where X is NH, CH2, C(CH3)2, or PPh, on the photo- and electroluminescent properties of a new family of luminescent cationic H-heterocyclic carbene (NHC) copper(I) complexes. A joint experimental and theoretical study demonstrates that the bridging group affects the molecular conformation from a planar-like structure (X is NH and CH2) to a boat-like structure (X is C(CH3)2 and PPh), leading to i) four-fold enhancement of the photoluminescence quantum yield (ϕem) without affecting the thermally activated delayed fluorescence mechanism, and ii) one order of magnitude reduction of the ionic conductivity (σ) of thin films. This leads to an overall enhancement of the device efficacy and luminance owing to the increased ϕem and the use of low applied driving currents.Building bridges: The structural and electronic features of bis-pyridyl ligands on cationic copper(I) complexes of general formula [Cu(IPr)(N^N)][PF6] are reported. This study led to novel guidelines for enhancing the photo- and electroluminescence features of this emerging family of copper(I) complexes.
      PubDate: 2017-10-25T10:00:40.93668-05:0
      DOI: 10.1002/chem.201703270
  • Optimization of Rate Capability and Cyclability Performance in Li3VO4
           Anode Material through Ca Doping
    • Authors: Jiafeng Zhou; Bangchuan Zhao, Jiyue Song, Bozhou Chen, Xiaohang Ma, Jianming Dai, Xuebin Zhu, Yuping Sun
      Pages: 16338 - 16345
      Abstract: A series of Ca-doped lithium vanadates Li3−xCaxVO4 (x=0, 0.01, 0.03, and 0.05) are synthesized successfully through a simple sol-gel method. XRD patterns and energy-dispersive X-ray spectroscopy (EDS) mappings reveal that the doped Ca2+ ions enter into the lattice successfully and are distributed uniformly throughout the Li3VO4 (LVO) grains. XRD spectra and SEM images show that Ca doping can lead to an enlarged lattice and refined Li3VO4 particles. A small quantity of V ions will transfer from V5+ to V4+ in the Ca-doped samples, as demonstrated by the X-ray photoelectron spectroscopy (XPS) analysis, which leads to an increase of an order of magnitude in the electronic conductivity. Improved rate capability and cycling stability are observed for the Ca-doped samples, and Li2.97Ca0.03VO4 exhibits the best electrochemical performance among the studied materials. The initial charge/discharge capacities at 0.1 C increase from 480/645 to 527/702 mA h g−1 as x varies from 0 to 0.03. The charge capacity of Li2.97Ca0.03VO4 at 1 C retains 95.3 % of its initial value after 180 cycles, whereas the capacity retention is only 40 % for the pristine sample. Moreover, Li2.97Ca0.03VO4 maintains a high discharge capacity of 301.7 mA h g−1 at a high discharge rate (4 C), whereas the corresponding value is only 95.2 mA h g−1 for the pristine LVO sample. The enhanced cycling and rate performances are ascribed to the increased lithium ion diffusivity and electrical conductivity induced by Ca doping.Ca-doped anodes: A series of Ca-doped lithium vanadates Li3−xCaxVO4 (x=0, 0.01, 0.03, and 0.05) are synthesized through a sol-gel method. The Ca-doped samples show improved rate capability and cycling stability, with Li2.97Ca0.03VO4 exhibiting a high discharge capacity of 301.7 mA h g−1 at a discharge rate of 4 C (corresponding value of 95.2 mA h g−1 for pristine LVO). The enhanced performance is attributed to the increased lithium ion diffusivity and electrical conductivity induced by the Ca doping.
      PubDate: 2017-10-23T07:46:23.566761-05:
      DOI: 10.1002/chem.201703405
  • Functionalization of 3-Iridacyclopentenes
    • Authors: Margarita Gómez; Nuria Rendón, Eleuterio Álvarez, Kurt Mereiter, Manuel L. Poveda, Margarita Paneque
      Pages: 16346 - 16356
      Abstract: Members of a series of iridacyclopentenes of composition [TpMe2Ir(k2-C,C-CH2CR′=CRCH2)(CO)] (TpMe2=hydrotris(3,5-dimethylpyrazolyl)borate; R=R′=H, 1; R=Me, R′=H, 2; R=R′=Me, 3) have been subjected to common organic chemistry procedures for hydrogenation, cyclopropanation, epoxidation, water addition through hydroboration, cis-dihydroxylation, and ozonolysis. The stability of metallacycles 1–3, imparted by the presence of the co-ligands TpMe2 and CO, directs the reactivity towards the C=C double bonds, and furthermore the stereochemistry of the products formed is strongly dictated by the steric demands of the TpMe2 ligand. While the products obtained in some of the above-mentioned reactions are the expected ones from an organic chemistry point of view, in other cases the results differ from the outcomes of similar reactions carried out with the all-carbon counterparts.Iridium surprise: Using methods commonly applied in organic chemistry, the 3-iridacyclopentenes of complexes [TpMe2Ir(κ2-C,C-CH2CR′=CRCH2)(CO)] (TpMe2=hydrotris(3,5-dimethylpyrazolyl)borate; R=R′=H, 1; R=Me, R′=H, 2; R=R′=Me, 3) have been functionalized, in some cases with unexpected outcomes, to give organometallic species with new structural motifs, as in the example shown in the scheme.
      PubDate: 2017-10-24T06:35:23.403071-05:
      DOI: 10.1002/chem.201703535
  • Selective Stabilization of the Spin States of a Magnetically Anisotropic
           Dysprosium Ion Induced by Photo-Excitation of the Associated Cyclic
           π-Conjugated System
    • Authors: Takamitsu Fukuda; Hideaki Ozawa, Yutaro Sakaguchi, Kazuro Kizaki, Toshiya Kobayashi, Akira Fuyuhiro, Naoto Ishikawa
      Pages: 16357 - 16363
      Abstract: The presence of a new electronic interaction, which couples a 4 f-electronic system with a total angular momentum J and a photoexcited cyclic π-conjugated system with an orbital angular momentum L, in the bis(phthalocyaninato)dysprosium single-molecule magnet ([DyPc2]−) is reported. Two π–π* excited states in the visible spectral region of the [DyPc2]− complex, which are denoted here as QL and QH, showed significantly different temperature and field dependences of the magnetic circular dichroism (MCD) A-term intensity. This phenomenon not only indicates the presence of a “J–L” interaction, but also that the interaction generates two different preferred orientations of the J–L pair, either parallel (for the QH band) or antiparallel (for the QL band), depending on the excitation energy. We have constructed a theoretical model that reproduces the temperature and field dependences, and quantitatively evaluated the J–L interaction.Parallel or antiparallel' A newly found electronic interaction (i.e., J–L interaction), which couples the total angular momentum J of a 4 f-electronic system and the photogenerated orbital angular momentum L in an excited cyclic π system, generates two different preferred orientations of the J–L pair in a lanthanide single-molecule magnet, that is, either parallel or antiparallel, depending on the excitation wavelength (see figure, Pc2−=phthalocyaninato).
      PubDate: 2017-10-26T08:32:46.517115-05:
      DOI: 10.1002/chem.201703588
  • Syntheses, Properties, and Catalytic Activities of Metal(II) Complexes and
           Free Bases of Redox-Switchable 20π, 19π, and 18π
    • Authors: Keisuke Sudoh; Takaharu Satoh, Toru Amaya, Ko Furukawa, Mao Minoura, Haruyuki Nakano, Yoshihiro Matano
      Pages: 16364 - 16373
      Abstract: In spite of significant advances in redox-active porphyrin-based materials and catalysts, little attention has been paid to 20π and 19π porphyrins because of their instability in air. Here we report the meso-modification of 5,10,15,20-tetraarylporphyrin with two nitrogen atoms, which led to redox-switchable 20π, 19π, and 18π 5,10,15,20-tetraaryl-5,15-diazaporphyrinoids (TADAPs). Three kinds of metal(II) complexes and free bases of TADAP were prepared by the metal-templated annulation of the corresponding metal-bis(dipyrrin) complexes. The inductive and resonance effects of the meso-nitrogen atoms on the aromatic, optical, electrochemical, and magnetic properties of the entire TADAP π-systems were assessed by using various spectroscopic measurements and density functional theory calculations. The aromaticity and π–π* electronic transition energies of the TADAPs varied considerably, and were shown to be dependent on the oxidation states of the π-systems. In contrast to the isoelectronic 5,10,15,20-tetraarylporphyrin derivatives, the 20π and 19π TADAPs were chemically stable under air. In particular, the 19π TADAP radical cations were extremely stable towards dioxygen, moisture, and silica gel. This reflected the low-lying singly occupied molecular orbitals of their π-systems and the efficient delocalization of their unshared electron spin. The capability of MgTADAP to catalyze aerobic biaryl formation from aryl Grignard reagents was demonstrated, which presumably involved a 19π/20π redox cycle.Redox-active macrocycles: A series of redox-switchable 20π, 19π, and 18π 5,10,15,20-tetraaryl-5,15-diazaporphyrinoids (TADAPs) are prepared (see scheme). The aromatic, optical, electrochemical, and magnetic properties of these TADAPs are shown to be strongly dependent on the oxidation states of their π-systems. MgTADAP behaves as the redox-active catalyst in a C−C bond-forming reaction of organometallic reagents.
      PubDate: 2017-10-26T08:33:43.610848-05:
      DOI: 10.1002/chem.201703664
  • Understanding the Catalytic Mechanism and the Nature of the Transition
           State of an Attractive Drug-Target Enzyme (Shikimate Kinase) by Quantum
           Mechanical/Molecular Mechanical (QM/MM) Studies
    • Authors: Jianzhuang Yao; Xia Wang, Haixia Luo, Pengfei Gu
      Pages: 16380 - 16387
      Abstract: Shikimate kinase (SK) is the fifth bacterial enzyme involved in the shikimate pathway for biosynthesis of life-indispensable components, such as aromatic amino acids. The absence of the shikimate pathway in humans makes SK an attractive target for the rational design of drugs aimed at pathogenesis bacteria, such as Mycobacterium tuberculosis and Helicobacter pylori. However, an effective inhibitor of SK (e.g., a transition-state analogue) is still not available on the market due, at least in part, to a lack of knowledge on the catalytic mechanism and the nature of the rate-limiting transition state. Herein, quantum mechanical/molecular mechanical (QM/MM) reaction coordinate, molecular dynamics (MD), and free-energy simulations have been performed to answer these questions. The results presented herein demonstrate that the phosphoryl-transfer process, which is the rate-limiting step of SK-catalyzed phosphorylation of shikimic acid (SKM), is a concerted one-step reaction proceeding through a loose transition state. The computational results agree well with those of experimental studies, specifically NMR results, X-ray crystal structure observation, and activation free-energy barrier.Enzyme in action: The reaction pathway and the nature of transition state of the phosphoryl-transfer process in the phosphorylation of shikimic acid catalyzed by shikimate kinase have been studied computationally (see figure).
      PubDate: 2017-10-23T07:46:02.143426-05:
      DOI: 10.1002/chem.201703867
  • Contraction of π-Conjugated Rings upon Oxidation from Cyclooctatetraene
           to Benzene via the Tropylium Cation
    • Authors: Akira Tamoto; Naoki Aratani, Hiroko Yamada
      Pages: 16388 - 16392
      Abstract: We have serendipitously discovered a unique transformation of a cyclooctatetraene derivative 1 into a cycloheptatriene spirolactone 3 upon oxidation, which is the first such transformation reported in 60 years. Product 3 could be reversibly interconverted into the aromatic tropylium cation 3H+ by acid/base treatment, which was accompanied by drastic spectroscopic changes. The resultant cycloheptatriene could be further converted into benzene upon oxidation. We characterized all the key structures by X-ray studies. Eventually, the π-conjugated ring size shrinks from 8 to 7, then finally to 6 upon oxidation, in the direction of the stronger aromatization.Unique skeletal shrinking: A modified cyclooctatetraene unit transforms into a cycloheptatriene spirolactone upon oxidation, which could be converted into benzene upon further oxidation. Consequently, the π-conjugated ring size shrinks from 8 to 7 and then to 6, therefore in the direction of the stronger aromatization (see figure).
      PubDate: 2017-10-25T09:56:23.538011-05:
      DOI: 10.1002/chem.201704008
  • Better Organic Ternary Memory Performance through Self-Assembled
           Alkyltrichlorosilane Monolayers on Indium Tin Oxide (ITO) Surfaces
    • Authors: Xiang Hou; Xue-Feng Cheng, Jin Zhou, Jing-Hui He, Qing-Feng Xu, Hua Li, Na-Jun Li, Dong-Yun Chen, Jian-Mei Lu
      Pages: 16393 - 16400
      Abstract: Recently, surface engineering of the indium tin oxide (ITO) electrode of sandwich-like organic electric memory devices was found to effectively improve their memory performances. However, there are few methods to modify the ITO substrates. In this paper, we have successfully prepared alkyltrichlorosilane self-assembled monolayers (SAMs) on ITO substrates, and resistive random access memory devices are fabricated on these surfaces. Compared to the unmodified ITO substrates, organic molecules (i.e., 2-((4-butylphenyl)amino)-4-((4-butylphenyl)iminio)-3-oxocyclobut-1-en-1-olate, SA-Bu) grown on these SAM-modified ITO substrates have rougher surface morphologies but a smaller mosaicity. The organic layer on the SAM-modified ITO further aged to eliminate the crystalline phase diversity. In consequence, the ternary memory yields are effectively improved to approximately 40–47 %. Our results suggest that the insertion of alkyltrichlorosilane self-assembled monolayers could be an efficient method to improve the performance of organic memory devices.Keep in mind: Memory devices with organic molecules on alkyltrichlorosilane-modified indium tin oxide (ITO) surfaces were fabricated. After modification with alkyltrichlorosilanes, the intermolecular stacking interactions as well as the mosaicity of the crystallites were greatly improved, the mobility of the carrier and the ternary device yield were enhanced.
      PubDate: 2017-10-24T06:24:57.436804-05:
      DOI: 10.1002/chem.201704059
  • Dinitromethyl-3(5)-1,2,4-oxadiazole Derivatives from Controllable
           Cyclization Strategies
    • Authors: Yongxing Tang; Chunlin He, Gregory H. Imler, Damon A. Parrish, Jean'ne M. Shreeve
      Pages: 16401 - 16407
      Abstract: N-Cyanoimidate (1) with hydroxylamine hydrochloride in the presence of triethylamine gives different products (2 a or 2 b) as a function of the sequence of reactant addition. Further oxidation/nitration/decarboxylation/acidification reactions of 2 a/2 b generate dinitromethyl-3(5)-1,2,4-oxadiazole derivatives, including a surprising energetic compound with high oxygen balance, 3-(dinitromethyl)-1,2,4-oxadiazol-5-one (5) as well as 5,5′-dinitromethyl-3,3′-azo-1,2,4-oxadiazole (9). Some salts of 5 and 9 as precursors were also prepared. All were fully characterized using multinuclear NMR and IR spectroscopy, and elemental analyses as well as low-temperature single-crystal X-ray diffraction for 4, 5, 7 and 8. In addition, their properties (thermal stability, detonation performance and sensitivity to impact and friction) were investigated. Among them, 5 and 8 show promising detonation performance as energetic materials.BOLD: Reaction of N-cyanoimidate (1) with hydroxylamine by different sequences of reactant addition led to two different oxadiazole rings, which go through several steps to generate dinitromethyl-3(5)-1,2,4-oxadiazoles and their derivatives.
      PubDate: 2017-10-25T09:55:55.637714-05:
      DOI: 10.1002/chem.201704446
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