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Journal Cover Chemistry - A European Journal
  [SJR: 2.323]   [H-I: 188]   [140 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]
  • Hybrid Surfactants with N-Heterocyclic Carbene Heads as a Multifunctional
           Platform for Interfacial Catalysis
    • Authors: Adrian Donner; Kay Hagedorn, Lorenz Mattes, Markus Drechsler, Sebastian Polarz
      Abstract: In daily life, surfactants are well known as detergents in the household. The cover image depicts the reported palladium-containing amphiphile using common household elements. The central part is a washing machine in which the micellar catalysis takes place. As an example, the catalytic cycle of a C−C cross-coupling reaction is implied. The machine (i.e., the catalytic reaction) is fed with our reported “soapy catalyst”, which is illustrated by the bottle of detergent and the rising soap bubbles. More information can be found in the Communication by S. Polarz et al. (
      DOI : 10.1002/chem.201703902).
      PubDate: 2017-10-20T04:36:19.711099-05:
       
  • Organocatalytic Asymmetric Synthesis of Spiro-Tetrahydrothiophene
           Oxindoles Bearing Four Contiguous Stereocenters by One-Pot
           Michael–Henry-Cascade–Rearrangement Reactions
    • Authors: Shengzheng Wang; Zhongjie Guo, Shuqiang Chen, Yan Jiang, Fan Zhang, Xueying Liu, Weiping Chen, Chunquan Sheng
      Abstract: Tetrahydrothiophenes with four contiguous stereocenters were constructed by an unprecedented organocatalytic asymmetric one-pot Michael–Henry-cascade−-rearrangement reaction. The new reaction assembled highly functionalized chiral spiro-tetrahydrothiophene and spiro-tetrahydrothiopyran scaffolds in good yields and with excellent stereocontrol. More information can be found in the Communication by S. Wang, C. Sheng et al. (
      DOI : 10.1002/chem.201703837).
      PubDate: 2017-10-20T04:36:02.276335-05:
       
  • Accessing Two-Coordinate ZnII Organocations by NHC Coordination:
           Synthesis, Structure, and Use as π-Lewis Acids in Alkene, Alkyne, and CO2
           Hydrosilylation
    • Authors: David Specklin; Frédéric Hild, Christophe Fliedel, Christophe Gourlaouen, Luis F. Veiros, Samuel Dagorne
      Abstract: Discrete two-coordinate ZnII organocations of the type (NHC)Zn−R+ are reported, thanks to NHC stabilization. In preliminary reactivity studies, such entities, which are direct cationic analogues of long-known ZnR2 species, act as effective and tunable π-Lewis acid catalysts in alkene, alkyne, and CO2 hydrosilylation.A welcome donation: Discrete two-coordinate ZnII organocations of the type (NHC)Zn−R+ are structurally characterized, thanks to NHC stabilization. Such entities, which are direct cationic analogues of long-known ZnR2 species, act as effective and tunable π-Lewis acid catalysts in alkene, alkyne, and CO2 hydrosilylation.
      PubDate: 2017-10-20T04:35:51.100504-05:
      DOI: 10.1002/chem.201704382
       
  • A One-Step Germole to Silole Transformation and a Stable Isomer of a
           Disilabenzene
    • Authors: Crispin R. W. Reinhold; Zhaowen Dong, Jan M. Winkler, Henning Steinert, Marc Schmidtmann, Thomas Müller
      Abstract: An unusual germole-to-silole transformation is described. As key intermediates hetero-fulvenes are formed which rearrange to more stable bicyclic carbene analogues. The so-formed germylenes undergo a reductive elimination yielding elemental germanium and siloles. In contrast, the analogous silylenes are stable at ambient conditions and were identified by MS spectrometry and NMR spectroscopy supported by the results of quantum mechanical calculations. These bicyclic silylenes are stable derivatives of the global minimum of the C4Si2H6 potential energy surface.Always expect the unexpected: An unprecedented germole to silole transformation opened the way for the synthesis of novel bicyclic silylenes that are stable derivatives of the global minimum on the C4Si2H6 potential energy surface.
      PubDate: 2017-10-20T04:35:34.80845-05:0
      DOI: 10.1002/chem.201703955
       
  • Structure and Function of Human Tyrosinase and Tyrosinase-related Proteins
    • Authors: Xuelei Lai; Harry J. Wichers, Montserrat Soler-Lopez, Bauke W. Dijkstra
      Abstract: Melanin is the main pigment responsible for the colour of human skin, hair and eye. Its biosynthesis requires three melanogenic enzymes, tyrosinase (TYR), and the tyrosinase-related proteins TYRP1 and TYRP2. The difficulty of isolating pure and homogeneous proteins from endogenous sources has hampered their study, and resulted in many contradictory findings regarding their physiological functions. In this review, we summarize recent advances on the structure and function of TYR and TYRPs by virtue of the crystal structure of human TYRP1, which is the first available structure of a mammalian melanogenic enzyme. This structure, combined with tyrosinase structures from other lower eukaryotes and mutagenesis studies of key active site residues, sheds light on the mechanism of TYR and TYRPs. Furthermore, a TYRP1-based homology model of TYR provides a high-quality platform to map and analyze albinism-related mutations, as well as the design of specific anti-melanogenic compounds. Finally, we provide perspectives for future structure/function studies of TYR and TYRPs.
      PubDate: 2017-10-20T03:45:59.600704-05:
      DOI: 10.1002/chem.201704410
       
  • Photoresponsive electrodes modified with DNA duplexes possessing a
           porphyrin dimer
    • Authors: Tadao Takada; Toshihiro Iwaki, Mitsunobu Nakamura, Kazushige Yamana
      Abstract: We describe here the formation of a porphyrin (Por) dimer using a DNA duplex as a scaffold and photocurrent generation from electrodes modified with a monolayer of Por-DNA conjugates. The solid-phase click reaction between an azide-porphyrin and oligonucleotide labeled with an ethynyl group on CPG supports was utilized for the conjugation of the Por to the DNA. UV/vis absorption and circular dichroism (CD) spectral studies revealed that the Por dimer can be formed via DNA hybridization and the through-space electronic interactions characterized from the exciton-coupled absorption and the bisignate CD can occur between the two Por molecules. Photoelectrochemical experiments were performed for the electrodes functionalized with a monolayer composed of the Por-DNA conjugates. We found that the Por dimer on the electrode, which was designed to resemble the special pair in natural photosynthesis, shows an efficient photocurrent generation in the presence of electron acceptor reagents compared to the Por monomer. Our findings strongly support the idea that the DNA structures could be useful to construct the Por arrays, which is essential for the design of photo- and bio-electronic devices.
      PubDate: 2017-10-20T02:45:25.101742-05:
      DOI: 10.1002/chem.201704281
       
  • Frontispiece: Recent Advances in Conjugated Furans
    • Authors: Hongda Cao; Paul A. Rupar
      Abstract: Furan and its derivatives have received little attention relative to thiophenes because of poor stabilities. However, furan's intrinsically chemical properties (reduced aromaticity, smaller size, increased electron richness) have motivated researchers to begin exploring the use of furan in conjugated materials. For more information see the Concept article by H. Cao and P. A. Rupar on page 14670 ff.
      PubDate: 2017-10-20T02:29:00.973925-05:
      DOI: 10.1002/chem.201785961
       
  • Frontispiece: Difluoromethylation Reactions of Organic Compounds
    • Authors: Damian E. Yerien; Sebastian Barata-Vallejo, Al Postigo
      Abstract: The difluoromethylation reactions of diverse families of organic substrates such as (hetero)aromatic compounds, olefins, isocyanides, alkynes, carbonyl compounds and hydrazones, alcohols, and tertiary amines will be presented. The methodology described for such reactions will include metal-mediated photocatalytic and thermal processes, as well as metal-free methodologies. For more details see the Review article by A. Postigo et al. on page 14676 ff.
      PubDate: 2017-10-20T02:28:52.772062-05:
      DOI: 10.1002/chem.201785962
       
  • Frontispiece: Indole- and Pyrrole-BX: Bench-Stable Hypervalent Iodine
           Reagents for Heterocycle Umpolung
    • Authors: Paola Caramenti; Stefano Nicolai, Jerome Waser
      Abstract: Electrophilic Indoles/Pyrroles: The first synthesis of indole- and pyrrole-derived benziodoxole reagents is reported in one step from the heterocycles. The new Indole- and Pyrrole-BX reagents are stable up to 150 °C. They can be used as electrophilic partners for selective heterocycle transfer onto the C−H bonds of arenes ortho to directing groups with rhodium or ruthenium catalysts. For more information see the Communication by J. Waser et al. on page 14702 ff.
      PubDate: 2017-10-20T02:28:49.060737-05:
      DOI: 10.1002/chem.201785963
       
  • Frontispiece: Structure–Property Relationship Study of Donor and
           Acceptor 2,6-Disubstituted BODIPY Derivatives for High Performance
           Dye-Sensitized Solar Cells
    • Authors: Shih-Chieh Yeh; Li-Jing Wang, Hong-Ming Yang, Yu-Huei Dai, Chao-Wen Lin, Chin-Ti Chen, Ru-Jong Jeng
      Abstract: BODIPY dyes as photosensitizers The electronic local excited (LE) state of prominent BODIPY dyes limits the efficiency in their application for dye sensitized solar cells (DSCs). To overcome such issues, C.-T. Chen, R.-J. Jeng et al. on page 14747 ff., present an insightful study about the structure-property relationship of a series of donor and acceptor 2,6-disubstituted BODIPY dyes; having a structural variation on donor, donor π-spacer, substituent on boron, acceptor π-spacer, and acceptor. A combination of spectroscopic experiment and theoretical calculation has demonstrated that the LE characteristics of the BODIPY dyes has been largely transformed to charge transfer (CT), which is a more favorable electronic feature of a photosensitizer used in DSCs. DSCs fabricated with MPBTTCA (shown in the picture) exhibit power conversion efficiency as high as 6.4%, one of the highest among DSCs having similar BODIPY dyes.
      PubDate: 2017-10-20T02:28:46.637515-05:
      DOI: 10.1002/chem.201785964
       
  • Synthesis of RNA Containing 5-Hydroxymethyl-, 5-Formyl-, and
           5-Carboxycytidine
    • Authors: Iacovos N. Michaelides; Nobuhiro Tago, Bastien Viverge, Thomas Carell
      Abstract: 5-Hydroxymethyl-, 5-formyl-, and 5-carboxy-2′-deoxycytidine are new epigenetic bases (hmdC, fdC, cadC) that were recently discovered in the DNA of higher eukaryotes. The same bases (5-hydroxymethyl-, 5-formyl-, and 5-carboxycytidine; hmC, fC, and caC) have now also been detected in mammalian RNA with a high abundance in mRNA. While DNA phosphoramidites (PAs) that allow the synthesis of xdC-containing oligonucleotides for deeper biological studies are available, the corresponding silyl-protected RNA PAs for fC and caC have not yet been disclosed. Here, we report novel RNA PAs for hmC, fC, and caC that can be used in routine RNA synthesis. The new building blocks are compatible with the canonical PAs and also with themselves, which enables even the synthesis of RNA strands containing all three of these bases. The study will pave the way for detailed physical, biochemical, and biological studies to unravel the function of these non-canonical modifications in RNA.New building blocks for synthetic RNA: The development of phosphoramidites and a solid-phase synthesis protocol for the convenient preparation of hmC-, fC-, and caC-containing (5-hydroxymethyl-, 5-formyl-, and 5-carboxycytidine) RNA is reported.
      PubDate: 2017-10-20T02:02:28.645862-05:
      DOI: 10.1002/chem.201704216
       
  • Intermolecular C−C Coupling between 1-Methyl-1,2,3-Triazole and
           2,2′-Bipyridine or 1,10-Phenanthroline in MoII Complexes
    • Authors: Sergio Fombona; Julio Pérez, Jesús Díaz, Lucía Riera
      Abstract: Unsupported 1-methyl-1,2,3-triazole has been coordinated to {Mo(η3-methallyl)(CO)2(N-N)} (N-N=2,2′-bipyridine, bipy; or 1,10-phenanthroline, phen) fragments, yielding cationic complexes that can be regarded as metalated triazolium salts. Their reactivity towards a strong base led to the deprotonation of the C5−H group of the triazole moiety, followed by an intermolecular nucleophilic attack to the ortho CH group of a bipy or phen ligand affording cyclic, bimetallic dearomatized C−C coupling products. The reaction of the neutral bipy derivative with an acid led to the formation of dihydropyridyl units by protonation of a CH group of the dearomatized rings, the dimeric nature of complexes being mantained upon protonation.Talkin′ ′bout deprotonation: The deprotonation of the C5−H group of a 1-methyl-1,2,3-triazole ligand leads to intermolecular nucleophilic attack of the ortho CH group of a bipy or phen ligand affording bimetallic dearomatized C−C coupling products (see figure).
      PubDate: 2017-10-20T02:01:57.822051-05:
      DOI: 10.1002/chem.201703524
       
  • Molecular Switches for any pH: A Systematic Study of the Versatile
           Coordination Behaviour of Cyclam Scorpionands
    • Authors: Yu Heng Lau; Jack K Clegg, Jason R Price, Rene B Marquart, Matthew H Todd, Peter J. Rutledge
      Abstract: Molecular switches have many potential applications in nanoscience and biomedicine. Transition metal complexes that can be switched from an unreactive state to an active one by a simple change in conditions (e.g. pH shift) or by binding to a specific biomolecular target - so-called target-activated metal complexes (TAMCs) - hold particular allure as a means of harnessing the potent but at times indiscriminate reactivity of metal-based drugs. We have prepared a series of ten structurally related ligands each of which bears a different pendant side-arm functional group off a common macrocyclic core. Copper(II) and nickel(II) complexes of these cyclam-based 'molecular scorpionands' have been prepared and characterised. X-ray crystal structures reveal a variety of binding modes between pendant side-arm and metal centre. To investigate the switchability of side-arm coordination in solution, spectrophotometric pH titrations were carried out for all 20 metal complexes. Where pH changes trigger a change in the spectroscopic behaviour, pKa values have been calculated. Of the 20 complexes investigated, the majority undergo spectroscopic changes that are consistent with a switch in pendant coordination state at a specific pH. This 'coordination switching' is seen across a wide pH range with the different side-arm functionalities. This ligand series represents a comprehensive model platform from which to build pH-switchable metal complexes for applications in nanoscience and biomedicine.
      PubDate: 2017-10-19T22:45:52.410967-05:
      DOI: 10.1002/chem.201703488
       
  • Facile and green route for the synthesis of SFE borosilicate zeolite and
           
    • Authors: Yi Luo; Zhendong Wang, Junliang Sun, Yingying Wang, Shaoqing Jin, Bin Zhang, Hongmin Sun, Weimin Yang
      Abstract: Synthesis of SFE type borosilciate zeolite was successfully carried out using a commercially available low-cost organic structure directing agent (OSDA) with ultra-low OSDA and water contents within a short crystallization time. Heteroatom (Al, Ti, V, or Fe) substituted SFE type zeolite analogues were also directly synthesized for the first time. The obtained Al containing zeolites exhibited promising catalytic performances in the disproportionation of isopropylnaphthalene.
      PubDate: 2017-10-19T22:45:44.548303-05:
      DOI: 10.1002/chem.201704668
       
  • The Development of Functional Mesocrystals for Energy Harvesting, Storage,
           and Conversion
    • Authors: Peng Zhang; Takashi Tachikawa, Mamoru Fujitsuka, Tetsuro Majima
      Abstract: Higher-ordered semiconductors have attracted extensive research interest as an adopted engineering for active solar energy harvesting, storage, and conversion. It is well-known that the effective separation and anisotropic migration of photogenerated charges are the basic driven force required for superior efficiency. However, the morphology and stoichiometric variation of these semiconductors play essential roles in their physicochemical properties of bulk and surface, especially for efficient interparticle or interfacial charge transfer. To this point, the strategy of controlling the topotactic transformation toward superstructures with optimized functionality is preferable for a wide range of optoelectronic and catalytic engineering applications. In this review, we provide an overview of the crystal orientation, synthetic engineering, functional applications, and spatial and temporal charge dynamics in TiO₂ mesocrystals and others. The viewpoint of in-depth understanding of the structure-related kinetics would offer an opportunity for design of versatile mesocrystal semiconductors sought-after for potential applications.
      PubDate: 2017-10-19T22:15:30.40846-05:0
      DOI: 10.1002/chem.201704680
       
  • Metal-free, Site-Selective Peptide Modification by Conversion of
           "Customizable" Units into beta-Substituted Dehydroamino Acids
    • Authors: Alicia Boto; Carlos Javier Saavedra, Dacil Hernández
      Abstract: This site-selective modification of serine or threonine units in peptides allows the generation of beta-substituted dehydro amino acids, which increase peptide resistance to hydrolysis and may improve their biological properties. Both terminal and internal positions can be modified, and different customizable units can be activated separately. Remarkably, high Z selectivity is achieved, even with internal positions. The conversion involves a one-pot scission-phosphorylation process, and the resulting amino phosphonates undergo a Horner-Wadsworth-Emmons reaction to produce the dehydroamino acid derivatives (usually Z:E>98:2) under mild and metal-free conditions.
      PubDate: 2017-10-19T09:15:27.385081-05:
      DOI: 10.1002/chem.201703758
       
  • Supramolecular storage and controlled photorelease of an oxidizing agent
           using a bambusuril macrocycle
    • Authors: Edoardo Torti; Vaclav Havel, Mirza Yawer, Lucie Ludvíkova, Michal Babiak, Petr Klan, Vladimir Sindelar
      Abstract: Bambusuril inhibits oxidizing ability of peroxodisulfate by its complexation inside the macrocycle cavity. This dianionic agent can be released on demand from its stable 1 : 1 complex in water (log Ka = 6.9 M −1) by addition of a more strongly bound anion, such as iodide (log Ka = 7.1 M−1), which can also be delivered upon irradiation in situ from a 4-hydroxyphenacyl iodide derivative with a spatial and temporal precision. The peroxodisulfate ion liberated from the complex recovers its oxidizing properties and can be involved in subsequent chemical transformations.
      PubDate: 2017-10-19T08:45:38.212915-05:
      DOI: 10.1002/chem.201704948
       
  • Cubane Cross-Coupling and Cubane-Porphyrin Arrays
    • Authors: Stefan Bernhard; Gemma Locke, Shane Plunkett, Alina Meindl, Keith Flanagan, Mathias O. Senge
      Abstract: The (im)possible Cube - Herein an improved methodology for aryl-cubane cross-coupling is reported. The peculiarities of the cubane core and its behavior during cross-coupling conditions are analyzed, while the versatility of this adapted Baran cross-coupling methodology is demonstrated by the synthesis of various aryl-cubane systems, among them coupling products of cubanes and porphyrins. Furthermore arm extension of alkynyl-cubanes via Sonogashira reactions is demonstrated, showcasing the first proof of the stability of the cubane core in the presence of palladium-catalysts.
      PubDate: 2017-10-19T07:45:22.011373-05:
      DOI: 10.1002/chem.201704344
       
  • One-Dimensional Phosphorus Nanostructures: from Nanorings to Nanohelices
    • Authors: Giuseppe Sansone; Lorenzo Maschio, Antti J. Karttunen
      Abstract: Phosphorus nanorings and nanohelices—speculated to exist over 20 years ago—have been systematically derived from one parent structure and studied with quantum chemical methods. The (P8P2)n nanorings have been recently synthetized inside carbon nanotube templates, and our comprehensive analysis of possible structural arrangements strongly supports the possibility to experimentally determine the closely related (P8P2)n nanohelices. The nanohelices possess very low stiffness, suggesting interesting mechanical properties with nano-spring-like behavior.Phosphorus nanohelices: We present a family tree of curved red phosphorus modifications and introduce novel phosphorus nanohelices with exciting mechanical properties.
      PubDate: 2017-10-19T06:55:45.91121-05:0
      DOI: 10.1002/chem.201703876
       
  • C(sp3)−H Bond Activation by Vinylidene Gold(I) Complexes: A Concerted
           Asynchronous or Stepwise Process'
    • Authors: Johannes E. M. N. Klein; Gerald Knizia, Laura Nunes dos Santos Comprido, Johannes Kästner, A. Stephen K. Hashmi
      Abstract: A detailed analysis of the C(sp3)−H activation process by vinylidene AuI complexes is described based on an intrinsic bond orbital analysis. Based on our analysis this event can be divided into three phases: (i) hydride transfer, (ii) C−C bond formation, and (iii) σ to π rearrangement of the lone pair coordinated to Au. Small perturbations of the system lead to either a concerted asynchronous reaction, or a stepwise reaction featuring an intermediate with a C-H-C three-centre two-electron (3c–2e) bond. The role of π-donating substituents is highlighted and provides a way of controlling reactions of this type in future experimental studies.Detailed theoretical investigations reveal that C(sp3)-H activation by vinylidene AuI complexes proceed either by a concerted asynchronous or a stepwise reaction featuring a C-H-C three-centre two-electron (3c-2e) bond. Intrinsic bond orbital analysis uncovers that this type of reaction is greatly facilitated by π-donating substituents.
      PubDate: 2017-10-19T06:55:31.940094-05:
      DOI: 10.1002/chem.201703815
       
  • Controllable Hierarchical Surface Patterns of Supramolecular Hydrogel via
           Harnessing Buckling Instability by Confinement
    • Authors: Zhijun Hu; Xiaohui Li, Mingyu Guo, Fang Wang, Xuezhen Shen, Yuyan Weng
      Abstract: Patterned surfaces of responsive polymers are often found applications in diverse fields. However, it is still a great challenge to fabricate hierarchical patterns with long-range orders. Here we demonstrate that controllable hierarchical surface patterns can be fabricated by combining nanoembossing techniques and surface instability of supramolecular hydrogel. Nanostripes arrays of polyethylene glycol (PEG)-based polyurethane-urea supramolecular hydrogel are firstly fabricated by nanoembossing techniques. Upon exposing to water, the lateral expansion of nanostripes is confined, leading to the formation of in or out of plane folded patterns depending on the aspect ratios. The direction of folds is perpendicular to the nanostripes. In addition, both the amplitude and the wavelength of out-of-plane folds are proportional to the thickness of nanostripes. Therefore, hierarchical structures, in which one periodicity is defined by the nanoembossing processes and the other one is determined by the surface buckling, can be quickly fabricated in thin films of supramolecular hydrogel.
      PubDate: 2017-10-19T06:46:24.852823-05:
      DOI: 10.1002/chem.201703155
       
  • Oligonucleotides with Cationic Backbone and Their Hybridization with DNA:
           Interplay of Base Pairing and Electrostatic Attraction
    • Authors: Boris Schmidtgall; Arne Kuepper, Melissa Meng, Tom Grossmann, Christian Ducho
      Abstract: Non-natural oligonucleotides represent important (bio)chemical tools and potential therapeutic agents. Backbone modifications altering hybridization properties and biostability can provide useful analogues. Here, we employ an artificial nucleosyl amino acid (NAA) motif for the synthesis of oligonucleotides containing a backbone decorated with primary amines. An oligo-T sequence of this cationic DNA analogue shows significantly increased affinity for complementary DNA. Notably, hybridization with DNA is still governed by Watson-Crick base pairing. However, single base pair mismatches are tolerated and some degree of sequence-independent interactions between the cationic NAA backbone and fully mismatched DNA are observed. These findings demonstrate that a high density of positive charges directly connected to the oligonucleotide backbone can affect Watson-Crick base paring. This provides a paradigm for the design of therapeutic oligonucleotides with altered backbone charge patterns.
      PubDate: 2017-10-19T06:45:23.647907-05:
      DOI: 10.1002/chem.201704338
       
  • Highly Spin-Frustrated Magnetism in the Topochemically Prepared Triangular
           Lattice Cluster Magnets Na3A2(MoO4)2Mo3O8 (A=In, Sc)
    • Authors: Yuya Haraguchi; Chishiro Michioka, Hiroaki Ueda, Kazuyoshi Yoshimura
      Abstract: The physical properties of novel cluster-based triangular lattice antiferromagnets Na3A2(MoO4)2Mo3O8 (A=In, Sc), synthesized through a topochemical Na-intercalation to nonmagnetic Na2A2(MoO4)2Mo3O8, are reported. The S=1/2 [Mo3]11+ clusters form a regular triangular lattice, which gives the magnetic system a strong geometrical spin frustration effect. Despite the strong antiferromagnetic couplings among [Mo3]11+ clusters, they show no long-range magnetic orderings down to 0.5 K with the finite residual magnetic entropy. The ground states of Na3A2(MoO4)2Mo3O8 have been characterized as a quantum spin liquid, owing to the strong spin frustration of cluster spins on the triangular lattice.Give it a spin: Topochemical intercalation of Na into Na2A2(MoO4)2Mo3O8 leads to novel cluster-based triangular lattice antiferromagnets Na3A2(MoO4)2Mo3O8 (A=In, Sc). The magnetic system shows a strong geometrical spin frustration effect. Despite the strong antiferromagnetic couplings among clusters, they show no long-range magnetic orderings down to 0.5 K.
      PubDate: 2017-10-19T06:26:35.791431-05:
      DOI: 10.1002/chem.201703597
       
  • Bio-Inspired Synthesis of an Ordered N/P Dual-Doped Porous Carbon and
           Application as an Anode for Sodium-Ion Batteries
    • Authors: Yun Qiao; Ruimin Han, Yang Liu, Mengyue Ma, Xiaoguang Cheng, Qingling Li, Hongyun Yue, Zhaoxia Cao, Huishuang Zhang, Shuting Yang
      Abstract: Carbonaceous materials are one of the most promising anode materials for sodium-ion batteries, because of their abundance, stability, and safe usage. However, the practical application of carbon materials is hindered by poor specific capacity and low initial Coulombic efficiency. The design of porous structure and doping with heteroatoms are two simple and effective methods to promote the sodium storage performance. Herein, the N, P co-doped porous carbon materials are fabricated using renewable and biodegradable gelatin as carbon and nitrogen resource, phosphoric acid as phosphorus precursor and polystyrene nanospheres as a template. The product can deliver a reversible capacity of 230 mA h g−1 at a current density of 0.2 A g−1, and even a high capacity of 113 mA h g−1 at 10 Ag−1. The enhanced sodium storage performance is attributed to the synergistic effect of the porosity and the dual-doping of nitrogen and phosphorus.I got the power: The porous and well-arranged 3D structure affords more open channels for electrolyte permeation and more active sites for the insertion/extraction of Na+. The synergistic effect of nitrogen and phosphorus dopants establishes a well-conductive network and enlarges the interlayer distance. The product can deliver a reversible capacity of 230 mA h g−1 at a current density of 0.2 A g−1 and even a high capacity of 113 mA h g−1 at 10 A g−1.
      PubDate: 2017-10-19T06:25:38.855841-05:
      DOI: 10.1002/chem.201703375
       
  • Individualization and Stabilization of Zinc Oxide Nanorods by Covalent
           Functionalization with Positively Charged Catechol Derivatives
    • Authors: Alexandra Burger; Rubitha Srikantharajah, Wolfgang Peukert, Andreas Hirsch
      Abstract: Nanoparticles feature fascinating properties, which render them interesting for broad fields of applications. However, nanoparticles strongly tend to aggregate when dispersed in liquids. One possibility to overcome this lies in their surface functionalization with suitable ligands. An effective way for the stabilization of zinc oxide nanorods by ligand exchange reactions is presented. Using positively charged catechol derivatives, the formation of stable suspensions is achieved, featuring individualized nanorods. More information can be found in the Full Paper by A. Hirsch et al. on page ▪▪ ff. (
      DOI : 10.1002/chem.201702109).
      PubDate: 2017-10-19T06:25:23.435155-05:
       
  • A Zinc Catalyzed C(sp3)−C(sp2) Suzuki–Miyaura Cross-Coupling Reaction
           Mediated by Aryl-Zincates
    • Authors: Richard J. Procter; Jay J. Dunsford, Philip J. Rushworth, David G. Hulcoop, Richard A. Layfield, Michael J. Ingleson
      Abstract: The Suzuki–Miyaura (SM) reaction is one of the most important methods for C−C bond formation in chemical synthesis. In this communication, we show for the first time that the low toxicity, inexpensive element zinc is able to catalyze SM reactions. The cross-coupling of benzyl bromides with aryl borates is catalyzed by ZnBr2, in a process that is free from added ligand, and is compatible with a range of functionalized benzyl bromides and arylboronic acid pinacol esters. Initial mechanistic investigations indicate that the selective in situ formation of triaryl zincates is crucial to promote selective cross-coupling reactivity, which is facilitated by employing an arylborate of optimal nucleophilicity.Old dog, new metal: The cross coupling of benzyl bromides with aryl borates is catalyzed by ZnBr2, in a process that is compatible with a range of functionalized benzyl bromides and arylboronic acid pinacol esters. Mechanistic investigations indicate that the in situ formation of triaryl zincates is crucial to promote selective cross-coupling reactivity.
      PubDate: 2017-10-19T06:16:48.49158-05:0
      DOI: 10.1002/chem.201704170
       
  • Organocatalytic Asymmetric Synthesis of Spiro-Tetrahydrothiophene
           Oxindoles Bearing Four Contiguous Stereocenters by One-Pot
           Michael–Henry-Cascade–Rearrangement Reactions
    • Authors: Shengzheng Wang; Zhongjie Guo, Shuqiang Chen, Yan Jiang, Fan Zhang, Xueying Liu, Weiping Chen, Chunquan Sheng
      Abstract: Asymmetric construction of tetrahydrothiophenes with four contiguous stereocenters remains a formidable challenge. Herein, the bottleneck was addressed by an unprecedented one-pot Michael–Henry-cascade–rearrangement reaction that could simultaneously create four consecutive stereogenic centers including two tetrasubstituted carbon stereocenters. The highly functionalized chiral spirotetrahydrothiophene scaffolds were assembled in moderate to good yields (≈54–79 %), excellent diastereo- (>20:1 d.r.) and enantio-selectivities (up to 93 % ee).Novel one-pot Michael–Henry-cascade–rearrangement reactions were used to efficiently construct tetrahydrothiophenes with four contiguous stereocenters.
      PubDate: 2017-10-19T06:16:42.003399-05:
      DOI: 10.1002/chem.201703837
       
  • Synergistic Configuration of Diols as Brønsted Bases
    • Authors: Ye-Jin Kim; Surajit Rakshit, Geun Young Jin, Prasun Ghosh, Young Min Lee, Won-Woo Park, Yung Sam Kim, Oh-Hoon Kwon
      Abstract: As viscous hydroxylic organic compounds, diols are of interest for their functional molecular conformation, which is based on inter- and intramolecular hydrogen (H)-bonds. By utilising steady-state electronic and vibrational spectroscopy, time-resolved fluorescence spectroscopy, and computational analyses, we report the association of the hydroxyl groups of diols via intra- or intermolecular H-bonds to enhance their reactivity as a base. Whereas the formation of an intermolecularly H-bonded dimer is requisite for diols of weak intramolecular H-bond to extract a proton from a model strong photoacid, a well-configured single diol molecule with an optimised intramolecular H-bond is revealed to serve as an effective Brønsted base with increased basicity. This observation highlights the collective role of H-bonding in acid–base reactions, and provides mechanistic backgrounds to understand the reactivity of polyols in the acid-catalysed dehydration for the synthesis of cyclic ethers at the molecular level.Sweet spot in diol hydrogen-bonding configuration: A well-configured single diol molecule, which has an optimised intramolecular hydrogen-bond length and angle between hydroxyl groups, is reported to operate as an effective Brønsted base. This leads to butanediol as an efficient precursor to produce tetrahydrofuran through acid-catalysed cyclic dehydration.
      PubDate: 2017-10-19T06:16:20.502282-05:
      DOI: 10.1002/chem.201703668
       
  • Subtle Steric Differences Impact the Structural and Conducting Properties
           of Radical Gold Bis(dithiolene) Complexes
    • Authors: Agathe Filatre-Furcate; Thierry Roisnel, Marc Fourmigué, Olivier Jeannin, Nathalie Bellec, Pascale Auban-Senzier, Dominique Lorcy
      Abstract: Among single component molecular conductors, neutral radical gold dithiolene complexes [(R-thiazdt)2Au]. derived from the N-alkyl-1,3-thiazoline-2-thione-4,5-dithiolate (R-thiazdt) ligand provide an extensive series of conducting, non-dimerized, half-filled band systems. Analogues of the known R=isopropyl (iPr) derivative were investigated here with R=NMe2, cyclopropyl (cPr) and n-propyl (nPr), aiming at rationalizing the different solid state structures adopted by these compounds despite very closely related substituents on the heterocyclic nitrogen atom. An original crisscross organization within dimerized chains is observed with R=NMe2, differing however from the analogous iPr derivative by a 180° rotation of the heterocyclic nitrogen substituent. On the other hand, the cyclopropyl and n-propyl substituents lead to robust, uniform, non-dimerized chains with a strongly 1 D electronic structure and a formal half-filled electronic structure. The semiconducting behaviour of these two radical complexes is characteristic of a Mott insulator, whose sensitivity to external pressure has been evaluated up to 2.5 GPa.An extensive series of conducting, non-dimerized, half-filled band systems has been provided with neutral radical gold dithiolene complexes [(R-thiazdt)2Au]. derived from the N-alkyl-1,3-thiazoline-2-thione-4,5-dithiolate (R-thiazdt) ligand as single component molecular conductors. Analogues of the known R=isopropyl (iPr) derivative were investigated here with R=NMe2, cyclopropyl (cPr) and n-propyl (nPr), aiming at rationalizing the different solid state structures adopted by these compounds despite very closely related substituents on the heterocyclic nitrogen atom.
      PubDate: 2017-10-19T06:16:02.220672-05:
      DOI: 10.1002/chem.201703172
       
  • Electrostatic Modification for Promotion of Flavin-Mediated Oxidation of a
           Probe for Flavin Detection
    • Authors: Dong-Nam Lee; Sohyeon Bae, Kyungja Han, Ik-Soo Shin, Seong Keun Kim, Jong-In Hong
      Abstract: Electrostatic effects on the redox photochemistry of synthetic probes (1, 2, and 1–Zn) are examined by adjusting the thermodynamic driving force of their oxidation reactions. The redox photochemistry was simply controlled by introducing a zinc binding site (2,2′-dipicolylamine (DPA)) on the coumarin moiety of probe 2. Zinc complexation produced a positively charged environment on the coumarin (1–Zn), which lowered the electron density of a nearby 9 H-xanthene ring, attenuating the auto-oxidation of 1–Zn by 45 % compared with that of probe 1 at 298 K. The positive net charge of 1–Zn also provided an attractive Coulombic force toward the phosphate of flavin mononucleotide and flavin adenine dinucleotide, which lowered the reduction potential of the electron acceptor (isoalloxazine) and improved intermolecular electron transfer from the 9 H-xanthene ring to isoalloxazine. The flavin-mediated oxidation rate of 1–Zn was increased to 1.5 times that of probe 2. Probe 1–Zn showed highly selective sensing behaviour toward flavins, producing an intense brightness (ϵΦF=2.80×103 m−1 cm−1) in the long-wavelength regions (λmax=588 nm) upon flavin-mediated oxidation. Furthermore, probes 1–Zn and 2 were successfully applied to eosinophil imaging and the differential diagnosis of eosinophilia; this demonstrates their use as diagnostic tools.Minimal auto-oxidation: Electrostatic effects on the redox photochemistry of synthetic probes was examined by adjusting the thermodynamic driving force of their oxidation reactions. The positively charged environment of 1–Zn attenuated its auto-oxidation and increased its flavin-mediated oxidation (see figure). This probe showed high selectivity for flavins and was applied to eosinophil imaging and the differential diagnosis of eosinophilia.
      PubDate: 2017-10-19T06:15:36.099302-05:
      DOI: 10.1002/chem.201703466
       
  • Nanoscale Metal-Organic Frames 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 provides an attractive way to eliminate the risk of cancer. In this paper, we prepared a composite material by nanoscale metal-organic frames (NMOFs) and graphene oxide (GO) for the potential use of photothermal therapy (PTT) of tumor guided with magnetic resonance imaging (MRI). The NMOFs containing Fe3+ were prefabricated with an octahedral morphology by a solvothermal reaction, offering strong T2-weighted contrast in MRI. Then the NMOFs were decorated with GO nanosheets, which were good at photothermal function. After the decorating, zeta-potential characterization shows the aqueous stability of the composite material is enhanced, ultraviolet-visible and near-infrared (UV-vis-NIR) spectra confirmed that NIR absorption is also increased, and photothermal experiments exhibited the composite materials expressed higher photothermal conversion effect and conversion stability. The fabricated NMOFs/GO shows low cytotoxicity, effective T2-weighted contrast of MRI and positive PTT behaviors for a tumor model in vitro. The performance of the composite NMOFs/GO for MRI and PTT was also carried out with injection into A549 tumor-bearing mice. The studies in vivo reveal that the fabricated NMOFs/GO was efficient in T2-weighted imaging and ablation of the A549 tumor with low cytotoxicity, implying the prepared composite contrast as a potential multifunctional nanotheranostic agent.
      PubDate: 2017-10-19T03:45:24.162465-05:
      DOI: 10.1002/chem.201702573
       
  • A Rotaxane Scaffold for the Construction of Multiporphyrinic Light
           Harvesting Devices
    • Authors: Jean-Francois Nierengarten; Béatrice Delavaux-Nicot, Haifa Ben Aziza, Iwona Nierengarten, Thi Minh Nguyet Trinh, Eric Meichsner, Matthieu Chessé, Michel Holler, Rym Abidi, Emmanuel Maisonhaute
      Abstract: A sophisticated photoactive molecular device has been prepared by combining recent concepts for the preparation of multifunctional nanomolecules (click chemistry on multifunctional scaffolds) with supramolecular chemistry (self-assembly to prepare rotaxanes). Specifically, a clickable [2]rotaxane scaffold incorporating a free-base porphyrin stopper has been prepared and functionalized with ten peripheral Zn(II)-porphyrin moieties. Electrochemical investigations of the final compound revealed a peculiar behavior resulting from the intramolecular coordination of the Zn(II) porphyrin moieties to 1,2,3-triazole units. Finally, steady state investigations of the compound combining Zn(II) and free-base porphyrin moieties have shown that this compound is a light-harvesting device capable of channeling the light energy from the peripheral Zn(II)-porphyrin subunits to the core by singlet-singlet energy transfer.
      PubDate: 2017-10-19T03:15:43.412568-05:
      DOI: 10.1002/chem.201704124
       
  • Preassembled Coumarin-Rhodamine Scaffold for Ratiometric Sensing of Nitric
           Oxide and Hypochlorite
    • Authors: Jun Xiang Ong; Victoria Yu Ting Pang, Li Min Tng, Wee Han Ang
      Abstract: A new preassembled ratiometric sensing platform was constructed from a coumarin donor and a rhodamine acceptor designed for through-bond energy transfer (TBET). A phenylacetylene linker was installed to disrupt the planarity of the extended conjugated system but retaining the efficient energy transfer between the donor and acceptor motifs. To demonstrate its versatility as a sensing platform, we conjugated recognition motifs through amide coupling reactions to yield two TBET chemosensors capable of sensing either endogenously produced NO and ClO-. Both probes possessed high selectivity for their analytes, exhibited good stability under physiological conditions, and performed well as bioimaging probes in living cells.
      PubDate: 2017-10-19T02:15:20.930979-05:
      DOI: 10.1002/chem.201703554
       
  • Ratiometric Fluorescence Detection of Phosphorylated Amino Acids Through
           Excited-State Proton Transfer by Using Molecularly Imprinted Polymer (MIP)
           Recognition Nanolayers
    • Authors: Wei Wan; Ana B. Descalzo, Sudhirkumar Shinde, Hardy Weißhoff, Guillermo Orellana, Börje Sellergren, Knut Rurack
      Abstract: A 2,3-diaminophenazine bis-urea fluorescent probe monomer (1) was developed. It responds to phenylphosphate and phosphorylated amino acids in a ratiometric fashion with enhanced fluorescence accompanied by the development of a redshifted emission band arising from an excited-state proton transfer (ESPT) process in the hydrogen-bonded probe/analyte complex. The two urea groups of 1 form a cleft-like binding pocket (Kb>1010 L2 mol−2 for 1:2 complex). Imprinting of 1 in presence of ethyl ester- and fluorenylmethyloxycarbonyl (Fmoc)-protected phosphorylated tyrosine (Fmoc-pTyr-OEt) as the template, methacrylamide as co-monomer, and ethyleneglycol dimethacrylate as cross-linker gave few-nanometer-thick molecularly imprinted polymer (MIP) shells on silica core microparticles with excellent selectivity for the template in a buffered biphasic assay. The supramolecular recognition features were established by spectroscopic and NMR studies. Rational screening of co-monomers and cross-linkers allowed to single out the best performing MIP components, giving significant imprinting factors (IF>3.5) while retaining ESPT emission and the ratiometric response in the thin polymer shell. Combination of the bead-based detection scheme with the phase-transfer assay dramatically improved the IF to 15.9, allowing sensitive determination of the analyte directly in aqueous media.Is it red or is it green' Not strictly STOP or GO like at a traffic lamp does, the ratio of both fluorescence colors of an excited-state proton transfer-active 2,3-diureaphenazine probe monomer co-polymerized into a thin MIP shell on a silica core particle tells whether the analyte, phosphorylated tyrosin, is present in the sample and at which concentration (see scheme).
      PubDate: 2017-10-19T00:45:42.731932-05:
      DOI: 10.1002/chem.201703041
       
  • Characterization of the RhI/dppe-Catalyzed Ring Expansion of
           2-Alkyl-Benzocyclobutenones by DFT Calculations
    • Authors: Hua-Li Qin; Chuang Zhao, Jing Leng, Eric Assen B. Kantchev
      Abstract: The [(dppe)RhCl]-catalysed ring expansion of 2-methylbenzocyclobutenone has been proposed to occur by C−C oxidative addition to rhodaindanone, β-hydride elimination, hydrorhodation and C−C reductive elimination. DFT calculations [IEFPCM(1,4-dioxane, 383.15 K)/PBE0/DGDZVP level of theory] here confirm this mechanism. As proposed, oxidative addition into CHMe−CO bond is preferred over the alternative CHMe-aryl insertion. The barriers of oxidative addition, β-hydride elimination hydrorhodation, and reductive elimination are 23.6 (rate-determining), 8.9, 10.4, and 13.1 kcal mol−1, respectively. Therefore, the β-hydride elimination/hydrorhodation steps to/from an octahedral RhIII-hydride serve as a fast equilibrating hydrogen shuffle flanking the two slower C−C bond breaking/making steps. This is consistent with the weak kinetic isotope effect observed experimentally when 2-CH3 and 2-CD3benzocyclobutenone react competitively in a 1:1 ratio. The reaction barriers calculated with more modern, dispersion interaction-corrected methods (SMD/M06 and IEFPCM/ωB97xD) follow identical trends.The proposed catalytic cycle of diphosphane/RhI-catalyzed ring expansion of 2-alkylbenzocyclobute-nones has been validated by DFT calculations (PCM/PBE0/DGDZVP level of theory).
      PubDate: 2017-10-19T00:45:35.198246-05:
      DOI: 10.1002/chem.201703096
       
  • Synthesis and Magnetic Properties of Trioxytriphenylamine Dimers in their
           Di(radical cationic) States
    • Authors: Shuichi Suzuki; Nobuaki Tanaka, Masatoshi Kozaki, Daisuke Shiomi, Kazunobu Sato, Takeji Takui, Keiji Okada
      Abstract: Three structural isomers of trioxytriphenylamine (TOT) dimers, 4,4′′′-bis(2,2′:6′,2“:6”,6-trioxytriphenylamine) (4), 3,3′′′-bis(2,2′:6′,2“:6”,6-trioxytriphenylamine) (5), and 3,4′′′-bis(2,2′:6′,2“:6”,6-trioxytriphenylamine) (6), have been prepared and their electronic and magnetic properties in their di(radical cationic) states have been investigated. These di(radical cationic) species can be handled under ambient conditions because of their high stability under aerated conditions even in solution. The X-ray crystal structure analysis demonstrated that the TOT moieties of all the di(radical cation)s have planar structures similar to that of the parent TOT radical cation 3+. The UV/Vis spectra of the di(radical cation)s show characteristic absorptions depending on the connecting pattern. Thus, in the long-wavelength region (600–900 nm), 42+ exhibits strong and broad characteristic absorptions, whereas compounds 52+ and 62+ exhibit weak absorptions. Notably, in the 450–600 nm region, 52+ displays very similar absorptions (with twice the intensity) to 3+, whereas small differences were observed for 62+. Finally, we investigated in detail the magnetic properties of the corresponding di(radical cation)s by electron spin resonance spectroscopy and magnetic susceptibility measurements, which indicated intramolecular exchange interactions with a singlet ground state and a large singlet–triplet (S–T) gap for 42+, a singlet ground state and a small S–T gap for 52+, and a triplet ground state for 62+.Not so tiny TOTs: The di(radical cation)s of three structural isomers of trioxytriphenylamine (TOT) dimers have been isolated as crystals that are stable in air and moisture. The para/para-, meta/meta-, and para/meta-linked TOT dimers were found to have the following electronic spin states: a singlet ground state with a large singlet–triplet (S–T) gap, a singlet ground state with a small S–T gap, and a triplet ground state, respectively (see figure).
      PubDate: 2017-10-19T00:45:26.609526-05:
      DOI: 10.1002/chem.201703220
       
  • Ultrathin Anionic Tungstophosphite Molecular Wire with Tunable
           Hydrophilicity and Catalytic Activity for Selective Epoxidation in Organic
           Media
    • Authors: Zhenxin Zhang; Masahiro Sadakane, Michikazu Hara, Wataru Ueda
      Abstract: Invited for the cover of this issue are the groups of Zhenxin Zhang and Wataru Ueda at Kanagawa University, Tokyo Institute of Technology, and Hiroshima University. The image depicts the development of a tungstophosphite molecular wire through the growth of a tree, in which the roots represent the triangular PIIIO3 units with tungstate that assemble into the trunk of building blocks and the final wire grows on the branches. Read the full text of the article at 10.1002/chem.201703856.“By combining porous properties and multi-redox properties of transition metal ions, we are producing novel unique porous materials.” Read more about the story behind the cover in the Cover Profile and about the research itself on page ▪▪ ff. (
      DOI : 10.1002/chem.201703856).
      PubDate: 2017-10-19T00:40:26.170145-05:
       
  • New Generation Agent Defeat Weapons: Energetic N, N'-Ethylene-Bridged
           Polyiodoazoles
    • Authors: Jean'ne M. Shreeve; Gang Zhao, Dheeraj Kumar, Chunlin He, Joseph P. Hooper, Gregory H. Imler, Damon A. Parrish
      Abstract: Sodium salts of iodine-rich pyrazole and imidazole with 1-(2-bromoethyl)-5-aminotetrazole are useful precursors for energetic N,N'-ethylene-bridged polyiodoazoles. Compounds 1 ̶ 3 were characterized with IR, and 1H and 13C NMR spectroscopy as well as elemental analyses. The molecular structures of 1 and 2 were confirmed by using single crystal X-ray diffraction. Heats of formation were calculated using Gaussian 03 and detonation properties and biocidal efficiency were calculated with CHEETAH 7. The decomposition products of 1 ̶ 3 destroy microbes more effectively than some previously reported biocides since the thermal decomposition occurs at below 400 oC without addition of oxidizer or combustion adjuvant.
      PubDate: 2017-10-18T20:45:53.078388-05:
      DOI: 10.1002/chem.201704798
       
  • Transuranic computational chemistry
    • Authors: Nikolas Kaltsoyannis
      Abstract: Recent developments in the chemistry of the transuranic elements are surveyed, with particular emphasis on computational contributions. Examples are drawn from molecular coordination and organometallic chemistry, and from the study of extended solid systems. The role of the metal valence orbitals in covalent bonding is a particular focus, especially the consequences of the stabilization of the 5f orbitals as the actinide series is traversed. The fledgling chemistry of transuranic elements in the +II oxidation state is highlighted. Throughout, the symbiotic interplay of experimental and computational studies is emphasized; the extraordinary challenges of experimental transuranic chemistry afford computational chemistry a particularly valuable role at the frontier of the periodic table.
      PubDate: 2017-10-18T14:15:20.957424-05:
      DOI: 10.1002/chem.201704445
       
  • Atomic/Molecular Layer Deposition of s-block Metal Carboxylate
           Coordination Network Thin Films
    • Authors: Jenna Penttinen; Mikko Nisula, Maarit Karppinen
      Abstract: We present novel atomic/molecular layer deposition (ALD/MLD) processes for the fabrication of crystalline inorganic-organic coordination network thin films with different s-block elements; terephthalic acid is employed as the organic precursor. Such thin films could enable e.g. next-generation battery, sensor and gas-storage technologies. The deposition processes fulfill the basic principles of ALD/MLD-type growth including the sequential self-saturated gas-surface reactions and atomic/molecular-level control for the film thickness, and yield crystalline thin films in a wide deposition temperature range. Structural characterization of the films is performed by GIXRD and FTIR; the data do not unambiguously prove but also do not rule out the crystal structures previously reported for the corresponding bulk samples. We moreover demonstrate the growth of crystalline thin films of a new terephthalate material with La as the metal component. Upon humidity treatments the Li, Na, K, Ba, and La terephthalate films remain unaffected while the Mg, Ca, and Sr terephthalate films reversibly absorb water molecules forming well-defined crystalline water-derivative phases.
      PubDate: 2017-10-18T12:15:24.177568-05:
      DOI: 10.1002/chem.201703704
       
  • First Structure of a Designed Minor Groove Binding Heterocyclic Cation
           that Specifically Recognizes Mixed DNA base pair Sequences
    • Authors: Narinder Kaur 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 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.
      PubDate: 2017-10-18T10:15:37.180471-05:
      DOI: 10.1002/chem.201704563
       
  • Solvent Effect on the Photoinduced Structural Change of a Phosphorescent
           Molecular Butterfly
    • Authors: Yingzhong Ma; Chenkun Zhou, Benjamin Doughty, Davis C. Easley, Justin Deterding, Biwu Ma
      Abstract: Photoinduced structural changes (PSC) is one of the fundamental excited-state dynamical 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, 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.
      PubDate: 2017-10-18T08:40:26.586405-05:
      DOI: 10.1002/chem.201703259
       
  • Mild Decarboxylative C−H Alkylation: Computational Insights for
           Solvent-Robust Ruthenium(II) Domino Manifold
    • Authors: N. Y. Phani Kumar; Torben Rogge, Santhivardhana Reddy Yetra, Alexander Bechtoldt, Eric Clot, Lutz Ackermann
      Abstract: Computational studies on decarboxylative C−H alkenylations provided key insights into the solvent-robust nature of C−H activation/decarboxylation domino reactions. These properties were exploited for ruthenium(II)-catalyzed C−H alkylations by a decarboxylative process with ample scope under copper-free and silver-free reaction conditions.Ex silico: Decarboxylative C−H alkylations were realized through key mechanistic insights, enabling ruthenium(II)-catalyzed domino C−H activation/decarboxylation under exceedingly mild conditions.
      PubDate: 2017-10-18T08:20:36.168802-05:
      DOI: 10.1002/chem.201703680
       
  • Terminal Alkyne Coupling on a Corrugated Noble Metal Surface: From
           Controlled Precursor Alignment to Selective Reactions
    • Authors: Tao Lin; Liding Zhang, Jonas Björk, Zhi Chen, Mario Ruben, Johannes V. Barth, Florian Klappenberger
      Abstract: Surface-templated covalent coupling of organic precursors currently emerges as a promising route to the atom-precise fabrication of low-dimensional carbon materials. Here, we investigate the adsorption and the coupling reactions of 4,4′′-diethynyl-1,1′:4′,1′′-terphenyl on Au(110) under ultra-high vacuum conditions by using scanning tunneling microscopy combined with density functional theory and kinetic Monte Carlo calculations. Temperature treatment induces both 1,2,4-asymmetric cyclotrimerization and homocoupling, resulting in various reaction products, including a previously unreported, surface-templated H-shaped pentamer. Our analysis of the temperature-dependent relative product abundances unravels that 1,2,4-trimerization and homocoupling proceed via identical intermediate species with the final products depending on the competition of coupling to a third monomer versus dehydrogenation. Our study sheds light on the control of coupling reactions by corrugated surfaces and annealing protocols.Templating of alkyne coupling by the corrugated Au(110) surface is investigated by abundance analysis of reaction products by STM, DFT, and kMC simulations. A unified reaction scenario is revealed in which cyclotrimerization and homocoupling proceed via the identical intermediate imposed by the templating and can be selected through the annealing recipe.
      PubDate: 2017-10-18T08:15:38.765004-05:
      DOI: 10.1002/chem.201701735
       
  • Silylene-Functionalized N-Heterocyclic Carbene (Si−NHC)
    • Authors: Dennis Rottschäfer; Sebastian Blomeyer, Beate Neumann, Hans-Georg Stammler, Rajendra S. Ghadwal
      Abstract: The incorporation of carbene (R2C:) and silylene (R2Si:) functionalities in the same molecule is a challenging task owing to their inherent reactivity. The synthesis of a stable compound (Si−NHC) featuring an unmasked carbene as well as a silylene is accomplished for the first time by installing a silylene functionality on the backbone of a 1,3-imidazolium-derived NHC. The Si−NHC compound offers significant potential as a ligand in the design of new catalysts, and as a building block for the preparation of new molecules and materials. More information can be found in the Full Paper by R. S. Ghadwal et al. (
      DOI : 10.1002/chem.201703530).
      PubDate: 2017-10-18T08:06:39.762288-05:
       
  • Di(hydroperoxy)alkane Adducts of Phosphine Oxides: Safe, Solid,
           Stoichiometric, and Soluble Oxidizing Agents
    • Authors: Shin Hye Ahn; Nattamai Bhuvanesh, Janet Blümel
      Abstract: Invited for the cover of this issue is the group of Janet Blümel at Texas A&M University. The image depicts the crystals and crystal structures of novel oxidizing agents: di(hydroperoxy)alkane adducts of phosphine oxides. Read the full text of the article at 10.1002/chem.201703676.“Besides classic reactions, all oxidation reactions that suffer from the presence of an excess of water can now be performed in an organic solvent.” Read more about the story behind the cover in the Cover Profile and about the research itself on page ▪▪ ff. (
      DOI : 10.1002/chem.201703676).
      PubDate: 2017-10-18T08:05:41.810705-05:
       
  • Structure, Electronics and Reactivity of Ce(PNP) Complexes
    • Authors: Alexander V. Zabula; Yusen Qiao, Alex J. Kosanovich, Thibault Cheisson, Brian C. Manor, Patrick J. Carroll, Oleg V. Ozerov, Eric J. Schelter
      Abstract: The coordination chemistry of complexes featuring a PNP ligand framework and the redox active lanthanide ion, cerium(III), was initiated. The cerium(III) ion induced the transformation of one of the phosphino donor arms at a parent PNP ligand into a new phosphido functionality. The Ce−PNP systems were also employed for C−C bond-forming reactions and the molecular structures of Ce−PNP complexes were studied both in solution and in the solid state. More information can be found in the Full Paper by O. V. Ozerov, E. J. Schelter et al. (
      DOI : 10.1002/chem.201703174).
      PubDate: 2017-10-18T08:05:24.585253-05:
       
  • Synthetic Talc and Talc-Like Structures: Preparation, Features and
           Applications
    • Authors: Marie Claverie; Angela Dumas, Christel Carême, Mathilde Poirier, Christophe Le Roux, Pierre Micoud, François Martin, Cyril Aymonier
      Abstract: This contribution gives a comprehensive review about the progress in preparation methods, properties and applications of the different synthetic talc types: i) crystalline nanotalc synthesized by hydrothermal treatment; ii) amorphous and/or short-range order nanotalc obtained by precipitation, and iii) organic–inorganic hybrid talc-like structures obtained through a sol–gel process or a chemical grafting. Several advantages of nanotalc such as high chemical purity, high surface area, tunable submicronic size, high thermal stability, and hydrophilic character (leading to be the first fluid mineral) are emphasized. Synthetic nanotalc applications are also considered including its use as nanofiller in composite materials, as absorbers of organic compounds, as anticorrosion coatings and as agents for cosmetic applications. Regarding their high industrial application potential, intensive research has been carried out to better understand their behavior and develop processes to produce them. To facilitate further research and development, scientific and technical challenges are discussed in this Review article.In the making: The growing interest in synthetic talc for polymer reinforcement and new cosmetic formulations has motivated research to propose novel synthesis routes based on the chemistry of materials. In this context, over the past 30 years, the synthesis process of talc has evolved noticeably leading to processes which could fulfill industrial requirements. In this Review, the different natures, the synthesis methods and the applications of synthetic nanotalc are enlightened with a focus on the crystalline nanotalc.
      PubDate: 2017-10-18T08:01:21.796111-05:
      DOI: 10.1002/chem.201702763
       
  • From Anilines to Quinolines: Iodide- and Silver-Mediated Aerobic Double
           C−H Oxidative Annulation–Aromatization
    • Authors: Jiwei Wu; Zhixiong Liao, Dong Liu, Chien-Wei Chiang, Zheng Li, Zhonghao Zhou, Hong Yi, Xu Zhang, Zixin Deng, Aiwen Lei
      Abstract: Quinoline synthesis from easily accessible raw materials such as anilines is a valuable and meaningful task. Herein, we communicate an iodide- and silver-mediated C−H/C−H oxidative annulation–aromatization between anilines and allyl alcohols. This protocol provides a direct route to the synthesis of quinoline derivatives from inexpensive commodities. Various kinds of anilines, even heterocyclic anilines, were shown to be workable substrates, generating the corresponding multi-substituted quinolines in good yields.Quinoline synthesis from simple substrates: An iodide- and silver-mediated C−H/C−H oxidative annulation–aromatization between anilines and allyl alcohols led to the formation of multi-substituted quinoline derivatives in good yields with a broad substrate scope.
      PubDate: 2017-10-18T08:01:00.68865-05:0
      DOI: 10.1002/chem.201703218
       
  • Role of Acid in Tailoring Prussian Blue as Cathode for High-Performance
           Sodium-Ion Battery
    • Authors: Yang Liu; Gangya Wei, Mengyue Ma, Yun Qiao
      Abstract: Prussian blue (PB) with concave centers is synthesized successfully through a hydrothermal method with the assistance of acid. In this study, the role of the acid is investigated systematically by adjusting the reaction temperature and time, using different kinds and amounts of acid, and changing the amount of PVP surfactant added. It is found that the acid can not only trigger the chemical reaction to form cubic PB, but also act as an etching reagent to tailor the morphology. The as-obtained cubic PB with concave centers demonstrates a superior cycle stability and rate performance, which can achieve a capacity of 107 mA h g−1 at 0.2 A g−1. The corresponding capacity retention is 74 % after 500 cycles relative to the second cycle. Even at a current density of 5 A g−1, the specific capacity remains at 82 mA h g−1. Furthermore, the full cell, using PB as the cathode and hard carbon as the anode, exhibits a high capacity of 70 mA h g−1 at 0.1 A g−1, and can power an LED light successfully. This work provides new insights into the role of acid in tailoring the morphology of PB, and opens a new avenue toward the design of unique structures to improve sodium storage.Tailored cathodes: Prussian blue (PB) samples are synthesized through a hydrothermal method with the assistance of acid. The acid not only triggers the chemical reaction to form cubic PB, but also acts as an etching reagent, tailoring the PB morphology. The as-obtained cubic PB with concave centers demonstrates superior cycle stability and rate performance, with good capacity retention (see scheme).
      PubDate: 2017-10-18T08:00:25.000224-05:
      DOI: 10.1002/chem.201703081
       
  • NCN-Coordinating Ligands based on Pyrene Structure with Potential
           Application in Organic Electronics
    • Authors: Dawid Zych; Aneta Kurpanik, Aneta Slodek, Anna Maroń, Michał Pająk, Grażyna Szafraniec-Gorol, Marek Matussek, Stanisław Krompiec, Ewa Schab-Balcerzak, Sonia Kotowicz, Mariola Siwy, Karolina Smolarek, Sebastian Maćkowski, Witold Danikiewicz
      Abstract: Five novel derivatives of pyrene, substituted at positions 1,3,6,8 with 4-(2,2-dimethylpropyloxy)pyridine (P1), 4-decyloxypyridine (P2), 4-pentylpyridine (P3), 1-decyl-1,2,3-triazole (P4), and 1-benzyl-1,2,3-triazole (P5), are obtained through a Suzuki–Miyaura cross-coupling reaction or CuI-catalyzed 1,3-dipolar cycloaddition reaction, respectively, and characterized thoroughly. TGA measurements reveal the high thermal stability of the compounds. Pyrene derivatives P1–P5 all show photoluminescence (PL) quantum yields (Φ) of approximately 75 % in solution. Solid-state photo- and electroluminescence characteristics of selected compounds as organic light-emitting diodes are tested. In the guest–host configuration, two matrixes, that is, poly(N-vinylcarbazole) (PVK) and a binary matrix consisting of PVK and 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PBD) (50:50 wt %), are applied. The diodes show red, green, or blue electroluminescence, depending on both the compound chemical structure and the actual device architecture. In addition, theoretical studies (DFT and TD-DFT) provide a deeper understanding of the experimental results.Pyrene derivative diodes: Novel 1,3,6,8-tetrasubstituted pyrene derivatives are developed, which show improved thermal stability and can act as efficient luminophores with high photoluminescence quantum yields (see figure). These compounds are promising for application in organic light-emitting diodes.
      PubDate: 2017-10-18T07:56:02.303129-05:
      DOI: 10.1002/chem.201703324
       
  • Solid-Phase Extraction of Hemoglobin from Human Whole Blood with a
           Coordination-Polymer-Derived Composite Material Based on ZnO and
           Mesoporous Carbon
    • Authors: Yuan Jia; Xinxin Xu, Jinzhao Ou, Xiaoxia Liu
      Abstract: A composite material, ZnO@MC, has been synthesized successfully by calcination using a one-dimensional zinc-based coordination polymer as the precursor. In ZnO@MC, ZnO particles with a size of about 5–8 nm are dispersed evenly in a mesoporous carbon matrix. Adsorption experiments at pH 6.8 with 2 mg ZnO@MC as adsorbent illustrated an adsorption efficiency of 92.3 % in 5 mL hemoglobin (Hb) solution with a concentration of 100 mg L−1. In contrast, the adsorption of bovine serum albumin can almost be ignored under the same conditions. The selectivity originates from a strong ZnII–histidine interaction between ZnO@MC and hemoglobin. The adsorption behavior of hemoglobin on ZnO@MC fits the Temkin model perfectly with a capacity as high as 11646 mg g−1. The hemoglobin adsorbed on the composite material can be eluted easily with sodium dodecyl sulfate stripping reagent with an extraction efficiency of 87.7 %. Circular dichroism spectra and protein activity studies suggest the structure and biological activity of hemoglobin is the same before and after the adsorption/desorption experiment. Finally, the ZnO@MC composite material was employed to extract hemoglobin from human whole blood without any pretreatment, and gave a very satisfactory result.Hemoglobin, selectively! A composite material has been synthesized successfully with a coordination polymer as the precursor by calcination. The composite selectively adsorbs hemoglobin from human whole blood extremely well. Furthermore, the adsorbed hemoglobin can be recovered easily with good retention of its structure and biological activity (see figure).
      PubDate: 2017-10-18T07:55:31.630042-05:
      DOI: 10.1002/chem.201703232
       
  • Hysteretic Two-Step Spin-Crossover Behavior in Two Two-Dimensional
           Hofmann-Type Coordination Polymers
    • Authors: Fu-Ling Liu; Jun Tao
      Abstract: The reaction of ferrous salts and square planar tetracyanometallates [MII(CN)4]2- (M = Pd, Pt) with ligand 4-(1H-pyrazol-3-yl)pyridine (Hppy) resulted in the formation of two two-dimensional (2D) Hofmann-like coordination polymers (CPs) with general formula of {FeII(Hppy)2[MII(CN)4]}·H2O (M = Pd for 1Pd, Pt for 1Pt). The two CPs have been studied by variable-temperature single-crystal X-ray crystallography, differential scanning calorimetry and magnetic measurements, respectively. 1Pd and 1Pt are isostructures, in which the Fe(II) atoms are equatorially coordinated with [MII(CN)4]2- to form 2D undulating layer and axially coordinated with Hppy ligands. Both compounds undergo cooperative, complete spin crossover (SCO) characteristic of abrupt and remarkable two equal steps, featuring hysteresis widths of 14 K and 19 K (1Pd) and 17 K and 23 K (1Pt) for the two steps, respectively. The SCO cooperativity may result from the hydrogen bonds and π···π interactions within and between such 2D layers, and the two-step SCO behaviors are accompanied with phase transitions.
      PubDate: 2017-10-18T06:45:35.900628-05:
      DOI: 10.1002/chem.201704276
       
  • Quantitative Analysis of Self-Assembly Process of a Pd2L4 Cage Consisting
           of Rigid Ditopic Ligands
    • Authors: Shumpei Kai; Vicente Marti-Centelles, Yui Sakuma, Takako Mashiko, Tatsuo Kojima, Umpei Nagashima, Masanori Tachikawa, Paul J. Lusby, Shuichi Hiraoka
      Abstract: The self-assembly process of a Pd2L4 cage complex consisting of rigid ditopic ligands, in which two 3-pyridyl groups are connected to a benzene ring through acetylene bonds, and Pd(II) ions was firstly revealed by a recently developed QASAP (quantitative analysis of self-assembly process), with which the self-assembly process of the coordination assemblies can be investigated by monitoring the time evolution of the average composition of all the intermediates. QASAP revealed that the rate-determining steps of the cage formation are the intramolecular ligand exchanges in the final stage of the self-assembly, [Pd2L4Py*2]4+ [Pd2L4Py*1]4+ + Py* and [Pd2L4Py*1]4+ [Pd2L4]4+ + Py* (Py*: 3-chloropyridine, which was used as a leaving ligand on the metal source). The energy barriers for the two reactions were determined to be 22.3 and 21.9 kcal mol-1, respectively. DFT calculation of the TS (transition state) structures for the two steps indicates that the distortion of the trigonal-bipyramidal Pd(II) center at the TS geometries increases the activation free energy of the two steps.
      PubDate: 2017-10-18T05:45:58.87113-05:0
      DOI: 10.1002/chem.201704285
       
  • Assembly of Coordination Polymers using Thioether-Functionalized
           Octasilsesquioxanes. Occurrence of (CuX)n Clusters (X = Br and I) within
           3D-POSS Networks
    • Authors: Abhinav Raghuvanshi; Carsten Strohmann, Jean-Baptiste Tissot, Sébastien Clément, Ahmad Mehdi, Sébastien Richeter, Lydie Viau, Michael Knorr
      Abstract: For the first time, POSS-based coordination polymers (CPs) have been structurally characterized. These CPs were obtained in high yield via self-assembly reactions of thioether-functionalized polysilsesquioxanes with Cu(I) salts under mild conditions. Single-crystal analyses revealed the formation of 3D networks incorporating different secondary building units (SBUs) as connection nodes. The nature of the -SAr function allows a fine-tuning of the cluster nuclearity, i.e. butterfly-shaped Cu2X2 or closed cubane-type Cu4I4 cores. As such, the resulting hybrid materials exhibit a combination of high thermal stability arising from the inorganic POSS core along with interesting luminescent properties conferred by the cubane cluster core. Furthermore, the occurrence of channels has been crystallographically evidenced in the case of the Cu4I4 cluster containing CP.
      PubDate: 2017-10-18T05:10:56.2237-05:00
      DOI: 10.1002/chem.201704911
       
  • Evidence for A [17] pi-Electronic Full-Fledged Non-Innocent
           Ga(III)-Corrole Radical
    • Authors: Biju Basumatary; Jyoti Rai, R V Ramana Reddy, Jeyaraman Sankar
      Abstract: One-electron oxidation of a Ga(III)-corrole with N(4-BrC6H4)3SbCl6 resulted in an air-stable non-innocent Ga(III)-corrole radical. Single crystal X-ray crystallography of 1,18-bisformyl[(TPFC)Ga(III)-Cl]* revealed delocalization of the unpaired electron, which was further confirmed by electron spin resonance (ESR) spectroscopy and spin density distribution plot. In addition, the nucleus-independent chemical shift (NICS), anisotropy induced-current density (AICD) and harmonic oscillator model of aromaticity (HOMA) supported a [17] pi-electron conjugated (or antiaromatic) radical.
      PubDate: 2017-10-18T02:10:45.397958-05:
      DOI: 10.1002/chem.201704457
       
  • Synthesis and Photophysical Characterization of
           2,3-Dihydroquinolin-4-imines: New Fluorophores with Color-Tailored
           Emission
    • Authors: Chih-Hung Chou; Basker Rajagopal, Chien-Fu Liang, Kuan-Lin Chen, Dun-Yuan Jin, Hsing-Yin Chen, Hsiu-Chung Tu, Yo-Ying Shen, Po-Chiao Lin
      Abstract: In this study, a series of variously substituted 2,3-dihydroquinolin-4-imines (DQIs) were synthesized from N-substituted propargylanilines by copper(I)-catalyzed annulation. The approach adopted in this study under mild, effective conditions exhibited broad substrate tolerance, particularly for functional groups substituted on anilines. Most of the DQI derivatives synthesized under optimal conditions were obtained in good isolated yields of 63-88%. 2,3-Dihydroquinolinimine thus obtained was easily converted to important structures like 2,3-dihydroquinolone and tetrahydrobenzodiazepin-5-one, confirming the importance of this strategy in constructing various heterocycles. Surprisingly, 2,3-dihydroquinolinimines thus obtained exhibited bright fluorescence with quantum yields up to 66%. The density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were performed for understanding the excited-state nature of DQI system. Accordingly, a tailored DQI derivative bearing methoxy group at C-6 position and acetoxy group at C-7 position was designed and synthesized to give emission at 559 nm with red-shift compared to the 7-methoxy substituted DQI. A detailed study of DQI structures with their photophysical properties was performed with five control molecules and consequently demonstrated the uniqueness of the chemical structures of DQIs.
      PubDate: 2017-10-18T01:15:32.667985-05:
      DOI: 10.1002/chem.201703998
       
  • An FeIII Azamacrocyclic Complex as a pH-Tunable Catholyte and Anolyte for
           Redox-Flow Battery Applications
    • Authors: Pavel B. Tsitovich; Anjula M. Kosswattaarachchi, Matthew R. Crawley, Timothy Y. Tittiris, Timothy R. Cook, Janet R. Morrow
      Abstract: A reversible Fe3+/Fe2+ redox couple of an azamacrocyclic complex is evaluated as an electrolyte with a pH-tunable potential range for aqueous redox-flow batteries (RFBs). The FeIII complex is formed by 1,4,7-triazacyclononane (TACN) appended with three 2-methyl-imidazole donors, denoted as Fe(Tim). This complex exhibits pH-sensitive redox couples that span E1/2(Fe3+/Fe2+)=317 to −270 mV vs. NHE at pH 3.3 and pH 12.8, respectively. The 590 mV shift in potential and kinetic inertness are driven by ionization of the imidazoles at various pH values. The Fe3+/Fe2+ redox is proton-coupled at alkaline conditions, and bulk electrolysis is non-destructive. The electrolyte demonstrates high charge/discharge capacities at both acidic and alkaline conditions throughout 100 cycles. Given its tunable redox, fast electrochemical kinetics, exceptional stability/cyclability, this complex is promising for the design of aqueous RFB catholytes and anolytes that utilize the earth-abundant element iron.Iron in energy storage: A reversible Fe3+/Fe2+ redox couple of an aza-macrocyclic complex has a pH-tunable 590 mV potential range useful for redox-flow battery (RFB) applications. Tunable redox, fast electrochemical kinetics, exceptional stability and cyclability of this complex is promising for the design of both aqueous catholytes and anolytes for RFBs that utilize the earth-abundant element, iron.
      PubDate: 2017-10-18T01:06:46.18259-05:0
      DOI: 10.1002/chem.201704381
       
  • Concise Total Synthesis of (−)-Affinisine Oxindole, (+)-Isoalstonisine,
           (+)-Alstofoline, (−)-Macrogentine, (+)-Na-Demethylalstonisine,
           (−)-Alstonoxine A, and (+)-Alstonisine
    • Authors: Michael Rajesh Stephen; M. Toufiqur Rahman, V. V. N. Phani Babu Tiruveedhula, German O. Fonseca, Jeffrey R. Deschamps, James M. Cook
      Abstract: A highly enantio- and diastereoselective strategy to access any member of the sarpagine/macroline family of oxindole alkaloids via internal asymmetric induction was developed from readily available d-(+)-tryptophan. At the center of this approach was the diastereospecific generation of the spiro[pyrrolidine-3,3′-oxindole] moiety at an early stage via a tert-butyl hypochlorite-promoted oxidative rearrangement of a chiral tetrahydro-β-carboline derivative. This key branching point determined the spatial configuration at the C-7 spiro center to be entirely 7R or 7S. Other key stereospecific processes were the asymmetric Pictet–Spengler reaction and Dieckmann cyclization, which were scalable to the 600 and 150 gram levels, respectively. Execution of this approach resulted in first enantiospecific total synthesis of (+)-isoalstonisine and (−)-macrogentine from the chitosenine series (7R), as well as (+)-alstonisine, (+)-alstofoline, (−)-alstonoxine A and (+)-Na-demethylalstonisine from the alstonisine series (7S).Enantioselective total synthesis: A highly enantio- and diastereoselective strategy to access any member of the sarpagine/macroline family of oxindole alkaloids by internal asymmetric induction was developed. The diastereospecific generation of the spiro[pyrrolidine-3,3′-oxindole] moiety at an early stage from a t-BuOCl-promoted oxidative rearrangement of a chiral tetrahydro-β-carboline derivative determined the C-7 spiro center to be either R or S. Execution of this approach resulted in first enantiospecific total synthesis of the shown alkaloids.
      PubDate: 2017-10-18T01:06:13.316553-05:
      DOI: 10.1002/chem.201703572
       
  • Hybrid Surfactants with N-Heterocyclic Carbene Heads as a Multifunctional
           Platform for Interfacial Catalysis
    • Authors: Adrian Donner; Kay Hagedorn, Lorenz Mattes, Markus Drechsler, Sebastian Polarz
      Abstract: Processing of substrates with different solvent compatibility is a persistent problem in homogeneous catalysis, in particular when one starting compound is water soluble and the other is not. A promising concept reported in the literature is micellar catalysis. However, the process of developing catalysts that are surfactants at the same time is still in its early stages. We report the synthesis of a new surfactant system with an N-heterocyclic carbene (NHC) moiety as a head group. Characteristic surfactant properties such as the formation of micelles or liquid crystals is documented. The new surfactant ligand forms coordination compounds with various metals, most importantly Pd2+, in square planar geometry. In addition, the Pd-NHC compound shows surfactant features, and can be used successfully for C−C cross-coupling reactions (Suzuki, Heck). The boost in catalytic activity by one order of magnitude compared to analogous but non-amphiphilic species is reported.Soapy catalyst in action: An organic–inorganic hybrid surfactant containing a carbene-Pd complex as a head is used for micellar catalysis bridging the gap for substrates with orthogonal solvent-compatibility (see figure).
      PubDate: 2017-10-18T01:05:34.732141-05:
      DOI: 10.1002/chem.201703902
       
  • Co3O4 Nanowire Arrays toward Superior Water Oxidation Electrocatalysis in
           Alkaline Media by Surface Amorphization
    • Authors: Dan Zhou; Liangbo He, Rong Zhang, Shuai Hao, Xiandeng Hou, Zhiang Liu, Gu Du, Abdullah M. Asiri, Chengbin Zheng, Xuping Sun
      Abstract: It is highly desirable to develop a simple, fast and straightforward method to boost the alkaline water oxidation of metal oxide catalysts. In this communication, we report our recent finding that the generation of amorphous Co-borate layer on Co3O4 nanowire arrays supported on Ti mesh (Co3O4@Co-Bi NA/TM) leads to significantly boosted OER activity. The as-prepared Co3O4@Co-Bi NA/TM demands overpotential of 304 mV to drive a geometrical current density of 20 mA cm-2 in 1.0 M KOH, which is 109 mV less than that for Co3O4 NA/TM, with its catalytic activity being preserved for at least 20 h. It suggests that the existence of amorphous Co-Bi layer promotes more CoOx(OH)y generation on Co3O4 surface.Co–Bi coated Co3O4 nanowire arrays supported on Ti mesh (Co3O4@Co–Bi NA/TM) behave as a high-performance and durable 3D catalyst electrode for alkaline water oxidation, with the need of overpotential of 304 mV to drive a geometrical current density of 20 mA cm−2 in 1.0 m KOH, 109 mV less than that for Co3O4 NA/TM. Such greatly boosted catalytic activity can be attributed to the introduction of an amorphous Co–Bi shell on Co3O4 that promotes the generation of more CoOx(OH)y as the active species.
      PubDate: 2017-10-18T01:00:45.030198-05:
      DOI: 10.1002/chem.201703565
       
  • Electro- and Photocatalytic Generation of H2 using a Distinctive Co(II)
           "PN3P" Pincer Supported Complex with Water or Saturated Saline as a
           Hydrogen Source
    • Authors: Gyandshwar Kumar Rao; Wendy Pell, Bulat Gabidullin, Ilia Korobkov, Darrin Richeson
      Abstract: Efficient electrocatalytic production of H2 from mixed water/acetonitrile solutions was achieved using three new Co(II) complexes supported by the neutral pincer ligand bis(diphenylphosphino)-2,6-di(methylamino)pyridine ("PN3P"). At 1.9 V vs Fc/Fc+, these catalysts showed 96% Faradaic efficiency with added water or saturated aqueous saline at rates of up to 316 L(mol cat)-1(cm2)-1h-1 using a glassy carbon working electrode. The complex [Co(3-2,6-{Ph2PNMe}2(NC5H3)Br2] (1) was also able to photocatalytically reduce water to hydrogen in the presence of a Ru(bpy)32+ photosensitizer and a reductant.
      PubDate: 2017-10-17T20:45:31.360301-05:
      DOI: 10.1002/chem.201704882
       
  • Metal-catalyzed Group-Transfer Polymerization: A versatile tool for
           tailor-made functional (co)polymers
    • Authors: Friederike Adams; Philipp Pahl, Bernhard Rieger
      Abstract: Accommodating the increasing demand for tailor-made polymers is a major goal in polymer chemistry. Therefore, the investigation of polymerization techniques, which allow the precise synthesis of macromolecules is of exceptional interest. Ionic or controlled radical polymerization are capable living-type methods for the generation of uniform polymers. However, even these approaches reach their limits in certain issues. In the last decades, group-transfer polymerization (GTP) and especially metal-catalyzed GTP have proven to give access to a plethora of tailor-made homo- and copolymers based on α,β-unsaturated monomers. Thereby, GTP has established its potential in the development of functional and smart polymers. This concept article highlights the most significant progress in metal-catalyzed GTP with a focus on functional (co)polymers including different polymeric architectures and microstructures.
      PubDate: 2017-10-17T11:13:00.617342-05:
      DOI: 10.1002/chem.201703965
       
  • Confinement of Water Pentamers within the Crystals of a Reduced
           Cyclotribenzoin
    • Authors: Maymounah Alrayyani; Xiqu Wang, Ognjen Miljanic
      Abstract: Reduction of cyclotribenzoin with sodium borohydride produces a cone-shaped hexaol. Crystals of this hexaol, obtained from wet tetrahydrofuran, encapsulate clusters of five water molecules in an idealized hydrogen-bonded arrangement. Water pentamer is stabilized by hydrogen bonding with the -OH groups of the hexaol, and [O-H···π] interactions with the benzene rings of the reduced cyclotribenzoin.
      PubDate: 2017-10-17T10:10:42.971902-05:
      DOI: 10.1002/chem.201704883
       
  • Breaking the concentration barrier for single molecule fluorescence
           measurements
    • Authors: Sijia Peng; Wenjuan Wang, Chunlai Chen
      Abstract: Fluorescence based single-molecule techniques have become widely used tools to reveal dynamic processes of biomolecules and elucidate their molecular mechanisms. However, the concentration upper limit of labeled species that can be used in single-molecule fluorescence measurements is at the low nM range, which is below the Michaelis constants of many enzymatic reactions and physiological concentrations of many biomolecules. Such discrepancy limits the application of single-molecule fluorescence tools. Several techniques have been developed to break the concentration barrier. In this concept, we focus on reviewing fundamental principles of these techniques and wish to inspire development of new and better tools to achieve this goal.
      PubDate: 2017-10-17T09:10:42.167897-05:
      DOI: 10.1002/chem.201704065
       
  • Octadentate Picolinic Acid-Based Bispidine Ligand for Radiometal Ions
    • Authors: Peter Comba; Una Jermilova, Chris Orvig, Brian O. Patrick, Caterina F. Ramogida, Katharina Rück, Christina Schneider, Miriam Starke
      Abstract: The synthesis of the octadentate bispidine ligand bearing two picolinic acid pendant arms (H2bispa2), and its coordination chemistry with radionuclides relevant for nuclear medicine, namely indium(III) (111In), lutetium(III) (177Lu), and lanthanum(III) (as surrogate for 225Ac), are reported. The non-radioactive metal complexes of the N6O2-type bispa ligand were characterized by 1H and 13C NMR spectroscopy, elemental analysis, mass spectrometry and single-crystal X-ray analysis. Experimental structural data, computational analysis, complex stabilities determined by potentiometric titration, and “radiostabilities” determined by competition studies in the presence of human serum reveal complex stabilities of H2bispa2 comparable to those of the macrocyclic “gold standard” DOTA. After an incubation time of 1 day, 86 and 87 % of [177Lu(bispa2)]+ and [177Lu(DOTA)]−, respectively, remain intact. Importantly, unlike DOTA, H2bispa2 is radiolabeled quantitatively with 111InIII and 225AcIII under ambient conditions, which is an essential aspect when working with heat-sensitive antibodies as targeting vectors. In the case of 111InIII, room temperature radiolabeling of H2bispa2 yields molar activities as high as 70 MBq nmol−1 within 10 minutes. These are promising results for radiopharmaceutical applications of H2bispa2.The synthesis and coordination chemistry of the novel octadentate bispidine ligand H2bispa2 is described. Furthermore, the N6O2-type bispa ligand was investigated with radioactive metal ions relevant for nuclear medicine, that is, 111InIII, 177LuIII and 225AcIII. Stabilities were observed to be the same or better than those of the corresponding metal-DOTA complexes in human serum; and quantitative radiolabeling at room temperature (in case of 111InIII and 225AcIII) were observed.
      PubDate: 2017-10-17T07:23:28.956826-05:
      DOI: 10.1002/chem.201702284
       
  • Usefulness of the σ-Aromaticity and σ-Antiaromaticity Concepts for
           Clusters and Solid-State Compounds
    • Authors: Ivan A. Popov; Alyona A. Starikova, Dmitry V. Steglenko, Alexander I. Boldyrev
      Abstract: In this Review we present examples of clusters, molecules, and solid-state compounds, for which the use of σ-aromaticity and σ-antiaromaticity concepts is essential for understanding of chemical bonding. We show that the bonding patterns in these σ-aromatic and σ-antiaromatic compounds are similar to those of the corresponding π-aromatic and π-antiaromatic chemical systems, respectively. Undoubtedly, σ-aromaticity helps us understand why the high symmetry isomers are the most stable among myriads of other potential structures. We also show that besides systems exhibiting either σ- or π-aromatic features, there are species, which can possess multiple aromaticity/antiaromaticity, or conflicting aromaticity patterns. We believe that the σ-aromaticity and σ-antiaromaticity concepts will be helpful in rationalizing chemical bonding, structure, stability, and molecular properties of chemical species in both organic and inorganic chemistry. We hope that they will also be useful for other areas of science such as material science, catalysis, nanotechnology, and biochemistry.Understanding chemical bonding: This Review focuses on the usefulness of the concepts of σ-aromaticity and σ-antiaromaticity in chemistry: from small clusters to bulky solid-state compounds. As one of the numerous examples, the counter-intuitive geometry of the global minimum structure of the Li2Mg2 cluster is explained using the σ-aromaticity based on the particular delocalized bonding pattern and energy considerations (see picture).
      PubDate: 2017-10-17T07:23:17.343543-05:
      DOI: 10.1002/chem.201702035
       
  • Cooperative Noncovalent Interactions Induce Ion Pair Separation in
           Diphenylsilanides
    • Authors: Eric A. Marro; Eric M. Press, Tapas K. Purkait, Daniel Jimenez, Maxime A. Siegler, Rebekka S. Klausen
      Abstract: This crystallographic and computational study describes an unusual potassium silanide structure. A contact ion pair is expected in the solid state between potassium and silicon, yet the potassium cation binds an aromatic ring and the anionic silanide interacts with CH bonds on neighboring crown ether molecules. These structure-bonding phenomena are attributed to strong soft–soft interactions.Both bound to the crown: This crystallographic and computational study describes an unusual separated ion pair in which crown ether molecules bind both cation and anion. These structure–bonding phenomena are attributed to strong soft–soft interactions.
      PubDate: 2017-10-17T07:21:53.455482-05:
      DOI: 10.1002/chem.201704217
       
  • Ultrathin Anionic Tungstophosphite Molecular Wire with Tunable
           Hydrophilicity and Catalytic Activity for Selective Epoxidation in Organic
           Media
    • Authors: Zhenxin Zhang; Masahiro Sadakane, Michikazu Hara, Wataru Ueda
      Abstract: Self-assembly of a central HPIIIO3 with six surrounding WO6 octahedra forms tungstophosphite polyoxometalate units, [HPIIIW6O21]2−. The polyoxometalate units linearly polymerize under hydrothermal conditions, eventually forming 1D molecular wires with a diameter of 1.2 nm. Surface modification with organoammonium cation enables the molecular wires to disperse in organic solvents. The dispersed ultrathin molecular wire acts as an efficient catalyst for olefin epoxidation. More information can be found in the Full Paper by Z. Zhang, W. Ueda et al. (
      DOI : 10.1002/chem.201703856).
      PubDate: 2017-10-17T07:21:26.176956-05:
       
  • Ultrathin Anionic Tungstophosphite Molecular Wire with Tunable
           Hydrophilicity and Catalytic Activity for Selective Epoxidation in Organic
           Media
    • Authors: Zhenxin Zhang; Masahiro Sadakane, Michikazu Hara, Wataru Ueda
      Abstract: The extended 1D tungstophosphite molecular wire is obtained by connection of polyoxometalates. Self-assembly of a triangular PIIIO3 unit with tungstate produces a hexagonal [HPIIIW6O21]2− building block, which then connects linearly to form the molecular wire. The surface property of the molecular wire is tuned to hydrophobic using organoammonium cations, and the surface-modified material disperses easily in organic media. The multifunctional material, which possesses nanostructure, hydrophobicity, and redox properties simultaneously, is suitable for olefin epoxidation in organic solvent.A wire for catalysis: The tungstophosphite molecular wire was obtained by self-assembly of [HPIIIW6O21]2− unit. The hydrophobic molecular wire can be used as a nanocatalyst for olefin epoxidation.
      PubDate: 2017-10-17T07:17:40.734404-05:
      DOI: 10.1002/chem.201703856
       
  • Supramolecular Synthon Approach in Developing Anti-Inflammatory Topical
           Gels for In Vivo Self-Delivery
    • Authors: Rajdip Roy; Parthasarathi Dastidar
      Abstract: A new series of tertiary-butyl ammonium (TBA) salts of various nonsteroidal anti-inflammatory drugs (NSAIDs) have been synthesized and characterized. Nearly 90 % of the NSAID-derived primary ammonium monocarboxylate (PAM) salts displayed remarkable gelation ability with various solvents including methyl salicylate. Single crystal X-ray diffraction data (SXRD) revealed the existence of 1D PAM synthon in the gelator salts. Structure–property correlation studies based on SXRD and powder X-ray diffraction (PXRD) data established the presence of the 1D PAM synthon in the bulk salts as well as in the corresponding xerogels. A parallel series of salts derived from TRIS (2-amino-2-(hydroxymethyl)-1,3-propanediol) and the same set of NSAIDs displayed poor gelation ability; only 33 % of the salts in the series displayed gelation ability. A few selected gelator salts of both TBA and TRIS were found to be biocompatible (MTT assay with RAW 264.7 cell line) and two of the selected salts (FLR.TBA and FLR.TRIS) possessed anti-inflammatory properties equal to the parent drug FLR (flurbiprofen). Finally a methyl salicylate topical gel derived from FLR.TRIS was successfully delivered in a self-delivery fashion to treat inflamed skin conditions in the mice model. Histological studies of the dorsal tissues of the untreated and treated mice clearly demonstrated the effect of topical gels in such treatment.Synthons applied directly to the forehead: Supramolecular synthon approach in the context of crystal engineering was exploited judiciously in gelation by simply tuning the hydrogen bonding functionalities. While 1D hydrogen bonded networks (HBN) promoted gelation, 2D and 3D HBN produced weak or no gel at all. One such biocompatible and anti-inflammatory methyl salicylate (MS) gel showed promise in in vivo self-delivery.
      PubDate: 2017-10-17T07:17:31.515213-05:
      DOI: 10.1002/chem.201703850
       
  • Size-Dependent Reactivity of Nano-Sized Neutral Manganese Oxide Clusters
           toward Ethylene
    • Authors: Jiao-Jiao Chen; Ting Zhang, Mei-Qi Zhang, Qing-Yu Liu, Xiao-Na Li, Sheng-Gui He
      Abstract: Neutral manganese oxide clusters with the general composition Mn2 NO3 N+x (N=2–22; x=−1, 0, 1) with dimensions up to a nanosize were prepared by laser ablation and reacted with C2H4 in a fast flow reactor. The size-dependent reactivity of C2H4 adsorption on these clusters was experimentally identified and the adsorption reactivity decreases generally with an increase of the cluster size. Density functional theory calculations were performed to study the geometrical and electronic structures of the Mn2 NO3 N (N=1–6) clusters. The calculated results indicated that the coordination number and the charge distribution of the metal centers are responsible for the experimentally observed size-dependent reactivity. The highly charged Mn atoms with low coordination are preferential to adsorb C2H4. In contrast, the neutral manganese oxide clusters are completely inert toward the saturated hydrocarbon molecule C2H6. This work provides new perspectives to design related materials in the separation of hydrocarbon molecules.Size-dependent reactivity: The size-dependent reactivity of C2H4 adsorption on neutral manganese oxide clusters with dimensions up to a nanosize has been identified experimentally and theoretically (see figure).
      PubDate: 2017-10-17T07:17:12.958386-05:
      DOI: 10.1002/chem.201703745
       
  • Single Oxidative Collision Events of Silver Nanoparticles: Understanding
           the Rate-Determining Chemistry
    • Authors: Kamonwad Ngamchuea; Richard O. D. Clark, Stanislav V. Sokolov, Neil P. Young, Christopher Batchelor-McAuley, Richard G. Compton
      Abstract: The oxidative dissolution of citrate-capped silver nanoparticles (AgNPs, ∼50 nm diameter) is investigated herein by two electrochemical techniques: nano-impacts and anodic stripping voltammetry. Nano-impacts or single nanoparticle-electrode collisions allow the detection of individual nanoparticles. The technique offers an advantage over surface-immobilized methods such as anodic stripping voltammetry as it eliminates the effects of particle agglomeration/aggregation. The electrochemical studies are performed in different electrolytes (KNO3, KCl, KBr and KI) at varied concentrations (≤20 mm). In nano-impact measurements, the AgNP undergoes complete oxidation upon impact at a suitably potentiostated electrode. The frequency of the nanoparticle-electrode collisions observed as current-transient spikes depends on the electrolyte identity, its concentration and the potential applied at the working electrode. The frequencies of the spikes are significantly higher in the presence of halide ions and increase with increasing potentials. From the frequency, the rate of AgNP oxidation as compared with the timescale the AgNP is in electrical contact with the electrode can be inferred, and hence is indicative of the relative kinetics of the oxidation process. Primarily based on these results, we propose the initial formation of the silver (I) nucleus (Ag+, AgCl, AgBr or AgI) as the rate-determining process of silver oxidation on the nanoparticle.Single silver nanoparticle (AgNP) detection: Nano-impacts or single nanoparticle-electrode collisions allow the detection of individual nanoparticles. Upon the impact, AgNP undergoes complete oxidation. The technique further allows the rate-determining process of silver oxidation at the electrode interface to be determined.
      PubDate: 2017-10-17T07:16:59.545539-05:
      DOI: 10.1002/chem.201703591
       
  • Ultrathin Cobalt-Based Metal–Organic Framework Nanosheets with Both
           Metal and Ligand Redox Activities for Superior Lithium Storage
    • Authors: Yanqun Ning; Xiaobing Lou, Chao Li, Xiaoshi Hu, Bingwen Hu
      Abstract: The controllable synthesis and structural tailoring of nanostructured metal–organic frameworks (MOFs) is of huge significance in boosting their potential for rechargeable batteries. We herein present the facile synthesis of cobalt-based ultrathin metal–organic framework nanosheets (referred to as “u-CoTDA”) by using 2,5-thiophenedicarboxylic (H2TDA) as the organic building block through a one-pot ultrasonic method for the first time. The obtained u-CoTDA exhibits high reversible capacity (790 mAh g−1 after 400 cycles at 1 A g−1) and excellent rate capability (694 mAh g−1 at 2 A g−1), which outperforms its bulk counterpart. Moreover, the detailed lithiation/delithiation processes of u-CoTDA were studied by the combination of Co K-edge X-ray absorption near edge structure (XANES), O K-edge soft X-ray spectroscopy (sXAS) and electron paramagnetic resonance (EPR) techniques, which demonstrate that both the CoII centers and organic ligands of u-CoTDA are involved in the reduction/oxidation processes.Recharge your batteries: This work reports ultrathin cobalt-based metal–organic framework nanosheets (u-CoTDA) that exhibit superior performance in rechargeable batteries compared to the bulk counterpart b-CoTDA. In addition, the Li+ intercalation/deintercalation mechanism of u-CoTDA was carefully studied.
      PubDate: 2017-10-17T07:16:32.959427-05:
      DOI: 10.1002/chem.201703077
       
  • Anion-Directed Metallocages: A Study on the Tendency of Anion Templation
    • Authors: Jing-Yun Wu; Ming-Shiou Zhong, Ming-Hsi Chiang
      Abstract: Self-assembly of Cu(NO3)2⋅3 H2O and di(3-pyridylmethyl)amine (dpma) with addition of different acids (HNO3, HOAc, HCl, HClO4, HOTf, HPF6, HBF4, and H2SO4) afforded a family of anion-templated tetragonal metallocages with a cationic prismatic structure of [(Gn−)⊂{Cu2(Hdpma)4}](8−n)+ (Gn−=NO3−, PF6−, SiF62−) with different ligating anions/solvents (NO3−, Cl−, ClO4−, OTf−, H2O) outside the cage. Systematic competitive experiments have rationalized the tendency of anion templation towards the formation of metallocages [(Gn−)⊂{Cu2(Hdpma)4}](8−n)+ as occurring in the order SiF62−≈PF6−>NO3−>SO42−≈ClO4−≈BF4−. This sequence is mostly elucidated by shape control over size selectivity and electrostatic attraction between the cationic {Cu2(Hdpma)4}8+ host and the anionic guests. In addition, these results have also roughly ranked the anion coordination ability in the order Cl−, ClO4−, OTf−>NO3−>BF4−, CH3SO4−. Magnetic studies of metallocages 1 t and 2–4 suggest that the fitted magnetic interaction, being weakly magnetically coupled overall, is interpreted as a result of the combination of intracage ferromagnetic coupling integrals and intercage antiferromagnetic exchange; both contributions are very weak and comparable in strength.Metallocage preference of anion templation: The findings of the anion-templated metallocages have approximately rationalized the capacity of anions to act as templates: SiF62− ≈ PF6−> NO3−> SO42− ≈ ClO4− ≈ BF4−, which could mostly be elucidated by their shape selectivity over electrostatic attraction, coordination interactions, and size (see scheme).
      PubDate: 2017-10-17T07:15:51.097346-05:
      DOI: 10.1002/chem.201702848
       
  • Zn(II) interrupts R4-R3 association leading to accelerated aggregation of
           tau protein
    • Authors: 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. Here we show that Zn2+ coordinate through the cysteine in R3 repeat and significantly accelerate the aggregation rate of the three repeat tau construct (K19) but 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.
      PubDate: 2017-10-17T07:10:37.076569-05:
      DOI: 10.1002/chem.201704555
       
  • 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 structure. 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.
      PubDate: 2017-10-17T06:17:47.254419-05:
      DOI: 10.1002/chem.201703658
       
  • A Static Electricity-Responsive Supramolecular Assembly
    • Authors: Hirokuni Jintoku; Hirotaka Ihara, Yoko Matsuzawa, Hideyuki Kihara
      Abstract: Stimuli-responsive materials can convert between molecular scale and macroscopic scale phenomena. We present two macroscopic static electricity-responsive phenomena based on nanoscale supramolecular assemblies of a zinc porphyrin derivative. One example involves the movement of supramolecular assemblies in response to static electricity. The assembly of a pyridine (Py) complex of the above derivative in cyclohexane is drawn to a positively charged material, while the assembly of a 3,5-dimethylpyridine complex is drawn to a negatively charged material. The second phenomenon involves the movement of a non-polar solvent in response to static electrical stimulation. A cyclohexane solution containing a small quantity of the Py complexed assembly exhibits a strong movement response towards negatively charged materials. Based on spectroscopic measurements and electron microscope observations, we reveal that the assembled formation generates the observed response to static electricity.
      PubDate: 2017-10-17T05:40:37.600827-05:
      DOI: 10.1002/chem.201704154
       
  • Selective F or Br Functionalization of Dibenzofuran for Application as
           Host Materials of Phosphorescent Organic Light-Emitting Diodes
    • Authors: Ji Gwang Yu; Sung Yong Byeon, Si Hyun Han, Jun Yeob Lee
      Abstract: Four dibenzofuran-type host materials substituted with a carbazolylcarbazole moiety were synthesized to investigate the effect of substitution position on the material parameters and device performances of host materials. The carbazolylcarbazole moiety was substituted at the 1-, 2-, 3-, and 4-positions of dibenzofuran by F or Br for a comprehensive study of the positional effect of dibenzofuran-derived host materials. Systematic synthesis and comparison of the four host materials revealed that 1-, 2-, and 4-position modification was better than 3-position modification for high triplet energy and high external quantum efficiency.Location, location, location: The effect of halogen substitution position in four dibenzofuran-type host materials containing a carbazolylcarbazole moiety on the material parameters and device performances is discussed. Results reveal that modification at the 1-, 2-, and 4-positions is better than that at the 3-position for high triplet energy and high external quantum efficiency (see figure).
      PubDate: 2017-10-17T05:28:26.847709-05:
      DOI: 10.1002/chem.201703307
       
  • Rhodium-induced reversible C-C bond cleavage - transformations of
           rhodium(III) 22-alkyl-m-benziporphyrins
    • Authors: Karolina Hurej; Milosz Pawlicki, Lechoslaw Latos-Grazynski
      Abstract: The structurally prearranged carbaporphyrins: 22-methyl- and 22-ethyl-m-benziporphyrins provided the platform stabilizing aromatic rhodium(III) 22-(μ-methylene-m-benziporphyrin) and rhodium(III) 22-(μ-ethylidene-m-benziporphyrin). An intramolecular conversion facilitated by the m-phenylene reactivity and observed for both aromatic complexes efficiently leads to rhodium(III) 21-(μ-methylene)-21-carbaporphyrin and rhodium(III) 21-(μ-ethylidene)-21-carbaporphyrin. The distinctive macrocyclic environment of rhodium(III) 21-carbaporphyrin created an opportunity to trap unique organometallic transformations of inner core substituents affording the fulvene like bond pattern or the rearrangement to 21-vinyl substituent. The one electron reduction of the rhodium(III) carbaporphyrin anion π-radical with a (dxy)2(dxz)2(dyz)2 - (P*-) electronic configuration. The further process of reduction of paramagnetic species triggers the ethyl migration from carbon(22) to rhodium(III) affording the diamagnetic rhodium(III) meta-benziporphyrin containing the apically coordinated σ-ethyl ligand providing an example of reversible C(sp2)-C(sp3) bond cleavage.
      PubDate: 2017-10-17T05:14:18.598958-05:
      DOI: 10.1002/chem.201704411
       
  • Desymmetrization of Bisallylic Amides through Catalytic Enantioselective
           Bromocyclization with BINAP Monoxide
    • Authors: Yoshihiro Nagao; Tatsunari Hisanaga, Hiromichi Egami, Yuji Kawato, Yoshitaka Hamashima
      Abstract: We report the first desymmetrization of bisallylic amides by enantioselective bromocyclization with BINAP monoxide as a catalyst. Depending upon the substitution pattern of the alkene moieties, densely functionalized, optically active oxazoline or dihydrooxazine compounds were obtained in a highly stereoselective manner. The remaining alkene moiety was subjected to various functional group manipulations to afford a diverse array of value-added chiral molecules with multiple stereogenic centers.
      PubDate: 2017-10-17T04:45:48.909957-05:
      DOI: 10.1002/chem.201704847
       
  • A Novel Approach to Synthesis a Dual Mode Luminescent Composite Pigment
           for Uncloneable High Security Codes to Combat Counterfeiting
    • Authors: KANIKA -; PAWAN KUMAR, SATBIR SINGH, BIPIN KUMAR Gupta
      Abstract: We demonstrate a strategy 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 accounts 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 synthesized 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 characterized by using XRD, SEM, TEM and confocal photoluminescent microscopic techniques, respectively. The distribution of PL intensity of printed pattern was examined by using confocal PL mapping microscopy. The obtained results reveals that security codes printed using ink formulated from this bi-luminescent composite pigment provides dual stage security against counterfeiting.
      PubDate: 2017-10-17T01:40:26.249035-05:
      DOI: 10.1002/chem.201704076
       
  • Model macrocyclic ligands for proof-of-concept mechanistic studies in
           transition metal-catalysis
    • Authors: Xavi Ribas; Marc Devillard
      Abstract: In this Concept article, we will scrutinize different approaches devoted to the mechanistic understanding of catalytic processes, paying special attention to the successful use of triazamacrocyclic aryl-halide or arene-containing substrates used for Cu-, Ag-, Au-, Co- and Ni-catalysis. The importance of designing model substrate platforms to unravel mechanistic details at a molecular level of C─C or C─heteroatom bond forming processes catalysed by transition metals will be highlighted. This fundamental mechanistic knowledge will serve as a foundation for the catalyst design for a desired transformation.
      PubDate: 2017-10-16T12:55:24.747036-05:
      DOI: 10.1002/chem.201704408
       
  • Alkyl and aryl thiol addition to [1.1.1]propellane - scope and limitations
           of a fast conjugation reaction
    • Authors: Robin M. Bär; Stefan Kirschner, Martin Nieger, Stefan Bräse
      Abstract: Herein we report the addition of different thiols to the strained carbon-carbon bond of [1.1.1]propellane (1). We investigated the reaction pathway, performed the addition with substituted thiols, hydrogen sulfide and protected cysteine and verified further modifications of the products. The clean reaction proceeds probably through a radical chain process as we confirmed with different deuterium labelling experiments. It shows great functional group tolerance as halogen-, hydroxy-, methoxy-, carboxy-, amino- and nitro-substituted thiols could be added to 1 with few by-products in 16-90% yield. Oxidation of the products offers a tuning of the polarity and subsequent reactions of the products. The "click"-type reaction proceeds even faster with selenols as we show in a proof-of-concept. The thiol addition to 1 offers a facile tool for surface modifications, conjugations and tuning of hydrophilicity in bio- and medicinal chemistry compounds.
      PubDate: 2017-10-16T12:20:38.213013-05:
      DOI: 10.1002/chem.201704105
       
  • A Bifunctional Fluorogenic Rhodamine Probe for Proximity-Induced
           Bioorthogonal Chemistry
    • Authors: Philipp Werther; Jasper S. Möhler, Richard Wombacher
      Abstract: Bioorthogonal reactions have emerged as a versatile tool in life sciences. The inverse electron demand Diels-Alder reaction (DAinv) stands out due to the availability of reactants with very fast kinetics. However, highly reactive dienophiles suffer the disadvantage of being less stable and prone to side reactions. Here, we evaluate the extent of acceleration of rather unreactive but highly stable dienophiles by DNA-templated proximity. To this end, we developed a modular synthetic route for a novel bifunctional fluorogenic tetrazine rhodamine probe that we used to determine the reaction kinetics of various dienophiles in a fluorescence assay. Under proximity-driven conditions the reaction was found to be several orders of magnitude faster, and we observed almost no background reaction when proximity was not induced. This fundamental study identifies a minimally sized fluorogenic tetrazine dienophile reactant pair that has potential to be generally used for the visualization of biomolecular interactions with temporal and spatial resolution in living systems.
      PubDate: 2017-10-16T08:21:22.8301-05:00
      DOI: 10.1002/chem.201703607
       
  • Everything you always wanted to know about poly-L-lysine dendrigrafts (but
           were afraid to ask)
    • Authors: Jean-Patrick Francoia; Laurent Vial
      Abstract: Less than a decade ago, dendrigrafts of poly-L-lysine (DGLs) joined the family of polycationic dendritic macromolecules. Resulting from the iterative polycondensation of a N-carboxyanhydride in water, four generations of the dendrigraft can be obtained on a multi-gram scale and without chromatographic purification. DGLs share features with both dendrimers and hyperbranched polymers, but turned out to have unique biophysical and bioactive properties. The macromolecules - in their native form or functionalized - have been extensively characterized by various analytical and computational methods, and already found numerous applications in the biomedical field such as drug and gene delivery, biomaterials, tissue engineering, bioimaging, and biosensing. Despite a growing interest for DGLs, there is still plenty of room for further exiting developments that could result from a better exposure of these macromolecules, which is the ambition of this short review.
      PubDate: 2017-10-16T07:26:15.233879-05:
      DOI: 10.1002/chem.201704147
       
  • Bonding Scheme and Optical Properties in BiM2O2(PO4) (M=Cd, Mg, Zn);
           Experimental and Theoretical Analysis
    • Authors: J. Olchowka; O. Mentré, H. Kabbour, M. Colmont, M. Adlung, M. Suta, C. Wickleder
      Abstract: Luminescence properties of the Bi(M,M′)2PO6 (M=Mg, Zn, Cd) series have been rationalized as a function of the M element using optical spectroscopy, as well as empirical and first principles calculations. The latter yielded indirect band gaps for all compounds with energies between 2.64 and 3.62 eV, whereas luminescence measurements exhibit bright warm white emission luminescence even at room temperature assigned to Bi3+ transitions with, for example, 22.8 % quantum yield for M=Mg. The energies of the excitation maxima are shifted with the covalent character of the Bi−O bond by inductive effects of the neighboring M−O bonds. This is discussed on the basis of empirical and electronic structure calculations. Strikingly, in all the investigated compounds, an excitation process occurring at energies higher than the band gaps is observed, which seems to be intrinsic to the s2sp electronic transitions of the Bi3+ ions. Concerning the emission process, a direct correlation between the lone pair (LP) activity and the emission energy upon change of the lattice parameters was established governing the LP stereo-activity in the BiMg2-xCdxPO6 system. As a result, the possibility for tunable optical properties appears realistic in the Bi2O3-MO-X2O5 (X=P, V, As, etc.) systems taking into account the diversity of reported or novel crystal structures that can be designed using well-established rules of crystal chemistry.Lone pair excitation: Luminescence properties of the Bi(M,M′)2PO6 (M=Mg, Zn, Cd) series have been rationalized as a function of the M element using optical spectroscopy, as well as empirical and first principles calculations.
      PubDate: 2017-10-16T06:50:37.339961-05:
      DOI: 10.1002/chem.201702373
       
  • Catalytic Intramolecular Cycloaddition Reactions by Using a Discrete
           Molecular Architecture
    • Authors: Bijan Roy; Anthonisamy Devaraj, Rupak Saha, Suprita Jharimune, Ki-Whan Chi, Partha Sarathi Mukherjee
      Abstract: A discrete tetragonal tube-shaped complex (MT-1) has been synthesised by coordination-driven self-assembly of a carbazole-based tetraimidazole donor L and a Pd(II) 90° acceptor, that is, [cis-(dppf)Pd(OTf)2] (dppf=diphenylphosphinoferrocene, OTf=CF3SO3−). Complex MT-1 was characterised by multinuclear NMR, ESI-MS and single-crystal X-ray diffraction analysis (SCXRD), which showed its symmetrical tetrafacial tube-shaped architecture possessing a large cavity described by four aromatic walls. This coordination cage was successfully utilised as a molecular vessel to perform intramolecular cycloaddition reactions of O-allylated benzylidinebarbituric acid derivatives inside its confined nanospace. The presence of a catalytic amount of MT-1 promoted [4+2] cycloaddition reactions in a regio- and stereoselective manner, yielding the corresponding penta/tetracyclouracil derivatives in good yields under mild reaction conditions. This protocol is interesting compared with the literature reports for the synthesis of similar chromenopyran pyrimidinedione derivatives under high-temperature reflux conditions or solid-state melt reactions (SSMRs).A discrete tetragonal tube-shaped molecular architecture (MT-1; see figure) has been synthesized by self-assembly of a tetraimidazole donor L and a Pd(II) 90° acceptor. Complex MT-1 was utilized as a molecular vessel to perform intramolecular hetero-Diels–Alder reactions of O-allylated benzylidinebarbuturic acid derivatives inside its confined nanospace (see scheme).
      PubDate: 2017-10-16T06:50:28.355791-05:
      DOI: 10.1002/chem.201702507
       
  • Synthesis of Spirocyclic Pyrrolidines: Advanced Building Blocks for Drug
           Discovery
    • Authors: Bohdan A. Chalyk; Maryna V. Butko, Oksana O. Yanshyna, Konstantin S. Gavrilenko, Tetiana V. Druzhenko, Pavel K. Mykhailiuk
      Abstract: Invited for the cover of this issue is the group of Pavel K. Mykhailiuk at the Taras Shevchenko National University of Kyiv and Enamine Ltd. The image depicts spirocyclic pyrrolidine—a novel building block for drug discovery. Read the full text of the article at 10.1002/chem.201702362.“…we were very much impressed by the high practical potential of the developed procedure: from every cyclic ketone, a variety of spirocyclic pyrrolidines can be obtained.” Read more about the story behind the cover in the Cover Profile and about the research itself on page ▪▪ ff. (
      DOI : 10.1002/chem.201702362).
      PubDate: 2017-10-16T06:50:20.740301-05:
       
  • Coupling and Dearomatization of Pyridines at a Transient
           η2-Cyclopropene/Bicyclobutane Zirconocene Complex
    • Authors: Nuria Romero; Quentin Dufrois, Laure Vendier, Chiara Dinoi, Michel Etienne
      Abstract: This paper reports on stereospecific coupling reactions between an η2-cyclopropene ligand and pyridine derivatives, which are preferred to alternative C−H bond activation reactions. The dicyclopropylzirconocene complex [Cp2Zr(c-C3H5)2] (1) eliminates cyclopropane to generate the η2-cyclopropene/bicyclobutane intermediate [Cp2Zr(η2-c-C3H4)] (A). A does not activate any pyridine C−H bonds, but rather pyridine inserts into a Zr−C bond of A, yielding an azazirconacycle with a dearomatized pyridyl group [Cp2Zr{κ2-N,C8-(2-c-C3H4)-C5H5N}] (2). Kinetic data, isotopelabelling experiments, and DFT calculations indicate that the rate-determining step of this stereospecific reaction is cyclopropane elimination, and that the stability of the intermediate [Cp2Zr(η2-c-C3H4)(NC5H5)] (A-py) governs the selectivity of the reaction. Complex 2 tautomerizes to [Cp2Zr{κ2-N,C8-(2-C3H5)-C5H4N}] (6) through a base-catalyzed proton migration accompanied by cyclopropyl opening and restoration of conjugation within the zirconacycle.The Odd Couple: Diastereospecific coupling of pyridine with a transient η2-cyclopropene zirconocene complex takes precedence over C−H bond activation, an alternative pathway observed for other heteroaromatics
      PubDate: 2017-10-16T06:46:04.022025-05:
      DOI: 10.1002/chem.201703371
       
  • Structure, Electronics and Reactivity of Ce(PNP) Complexes
    • Authors: Alexander V. Zabula; Yusen Qiao, Alex J. Kosanovich, Thibault Cheisson, Brian C. Manor, Patrick J. Carroll, Oleg V. Ozerov, Eric J. Schelter
      Abstract: Synthetic methods for the coordination of the monoanionic bis[2-(diisopropylphosphino)-4-methylphenyl]amido (PNP) ligand framework to the cerium(III) cation have been developed and applied for the isolation of a series of {(PNP)Ce} and {(PNP)2Ce} type complexes. The structures of the complexes were studied by X-ray diffraction and multinuclear NMR spectroscopy. We found that the cerium(III) ion can induce the elimination of one of the iPr groups at phosphorus to yield a new dianionic PNP tridentate framework (PNP-iPr) featuring a phosphido-donor functionality, which is bound to the cerium ion with the shortest known Ce−P bond of 2.7884(14) Å for molecular compounds. The reaction of the complex [(PNP)Ce{N(SiMe3)2}2] (1) with Ph2CO gave the Ce-bound product of C−C coupling, -N(SiMe3)SiMe2CH2-CPh2O−, through the C−H bond activation of a SiMe3 group. 31P NMR spectroscopy was used to estimate the presence of a vacant coordination position at the cerium ion in the CeIII–PNP complexes by the examination of the δ(31P) shift recorded both in non-polar (C6D6) and polar ([D8]THF) solvents. Moreover, 31P NMR spectroscopy was also found to be a useful tool for the estimation of the Ce−P bond distances in {(PNP)CeIII} and {(PNP)2CeIII} systems. Electrochemical and computational studies for 1 and its lanthanum analogue containing a redox-innocent metal center revealed the stabilization of the CeIII oxidation state by the PNP ligand.Getting Ce-rious: CeIII–PNP complexes were prepared and characterized both in solution and in the solid state. These complexes were employed for the structural alteration of the PNP ligand framework and for C−C bond-forming reactions.
      PubDate: 2017-10-16T06:45:53.162199-05:
      DOI: 10.1002/chem.201703174
       
  • Binding Mode and Selectivity of a Scorpiand-Like Polyamine Ligand to
           Single- and Double-Stranded DNA and RNA: Metal- and pH-Driven Modulation
    • Authors: Mario Inclán; Lluis Guijarro, Isabel Pont, Juan C. Frías, Carmen Rotger, Francisca Orvay, Antoni Costa, Enrique García-España, M. Teresa Albelda
      Abstract: The interaction of a polyazacyclophane ligand having an ethylamine pendant arm functionalized with an anthryl group (L), with the single-stranded polynucleotides polyA, polyG, polyU, and polyC as well as with the double-stranded polynucleotides polyA–polyU, poly(dAT)2, and poly(dGC)2 has been followed by UV/Vis titration, steady state fluorescence spectroscopy, and thermal denaturation measurements. In the case of the single-stranded polynucleotides, the UV/Vis and fluorescence titrations permit to distinguish between sequences containing purine and pyrimidine bases. For the double-stranded polynucleotides the UV/Vis measurements show for all of them hypochromicity and bathochromic shifts. However, the fluorescence studies reveal that both polyA–polyU and poly(dAT)2 induce a twofold increase in the fluorescence, whereas interaction of poly(dGC)2 with the ligand L induces a quenching of the fluorescence. Cu2+ modulates the interaction with the double-stranded polynucleotides due to the conformation changes that its coordination induces in compound L. In general, the spectroscopic studies show that intercalation seems to be blocked by the formation of the metal complex. All these features suggest the possibility of using compound L as a sequence-selective fluorescence probe.Interplay: The binding mode, selectivity, and modulation of the interaction of a scorpiand-type polyamine ligand (see figure) towards different sequences of single- and double-stranded polynucleotides have been studied by spectroscopic techniques. The compound shows potential as a sequence-selective fluorescent probe.
      PubDate: 2017-10-16T06:45:42.015617-05:
      DOI: 10.1002/chem.201702934
       
  • η1-Arene Complexes as Intermediates in the Preparation of Molecular
           Phosphorescent Iridium(III) Complexes
    • Authors: Miguel A. Esteruelas; Daniel Gómez-Bautista, Ana M. López, Enrique Oñate, Jui-Yi Tsai, Chuanjun Xia
      Abstract: Molecular phosphorescent heteroleptic bis-tridentate iridium(III) emitters have been prepared via η1-arene intermediates. In the presence of 4.0 mol of AgOTf, the complex [(IrCl{κ3-N,C,N-(pyC6HMe2py)})(μ-Cl)]2 (1; pyC6H2Me2py=1,3-di(2-pyridyl)-4,6-dimethylbenzene) reacted with 9-(6-phenylpyridin-2-yl)-9H-carbazole (PhpyCzH) and 2-phenoxy-6-phenylpyridine (PhpyOPh) to give [Ir{κ3-N,C,N-(pyC6HMe2py)}{κ3-C,N,C′-(C6H4pyCzH)}]OTf (2) and [Ir{κ3-N,C,N-(pyC6HMe2py)}{κ3-C,N,C′-(C6H4pyOPh)}]OTf (3). The X-ray diffraction structures of 2 and 3 reveal that the carbazolyl and phenoxy substituents of the C,N,C′ ligand coordinate to the metal center to form an η1-arene π bond. Treatment of 2 and 3 with KOtBu led to the deprotonation of the coordinated carbon atom of the η1-arene group to afford the molecular phosphorescent [5t+4t′] heteroleptic iridium(III) complexes [Ir{κ3-N,C,N-(pyC6HMe2py)}{κ3-C,N,C′-(C6H4pyCz)}] (4) and [Ir{κ3-N,C,N-(pyC6HMe2py)}{κ3-C,N,C′-(C6H4pyOC6H4)}] (5). These complexes are green emitters that display short lifetimes and high quantum yields of 0.73 (4) and 0.87 (5) in the solid state.Green phosphorescence: Molecular phosphorescent heteroleptic bis-tridentate iridium(III) complexes with a six-membered heterometallacycle in their structure (see figure) have been prepared via η1-arene intermediates. They are green emitters that display short lifetimes (1–10 μs) and high quantum yields (0.73–0.87) in the solid state.
      PubDate: 2017-10-16T06:45:37.270858-05:
      DOI: 10.1002/chem.201703252
       
  • Mixed Allyl Rare-Earth Borohydride Complexes: Synthesis, Structure, and
           Application in (Co-)Polymerization Catalysis of Cyclic Esters
    • Authors: Sami Fadlallah; Jashvini Jothieswaran, Frédéric Capet, Fanny Bonnet, Marc Visseaux
      Abstract: A series of new trivalent rare-earth allyl–borohydride complexes with the formula [RE(BH4)2(C3H5)(thf)x] (RE=Sc (1), x=2; RE=Y (2) and La (3), x=3) were synthesized by reaction of the corresponding rare-earth trisborohydrides [RE(BH4)3(thf)x] with half an equivalent of bis(allyl)magnesium. The complexes were fully characterized by determining their X-ray structure. Similar to their previously described Nd (4) and Sm (5) analogues, these complexes display a monomeric structure with two terminal trihapto BH4 groups, one π–η3 allyl ligand, three THF molecules for complexes 2 and 3, and two THF molecules for complex 1. The catalytic behavior of complexes 1–5 toward the ring-opening polymerization (ROP) of l-lactide (l-LA) and ϵ-caprolactone (ϵ-CL) was assessed. The Nd complex featured the best activity toward l-LA (turnover frequency (TOF)=1300 h−1) and the order was Nd>La>Sm>Y>Sc. Complexes 1–3 were found very active for the ROP of ϵ-CL (TOF=166 000 h−1), which is in line with the already established exceptionnally high performance of complexes 4 and 5. With both monomers, it was shown that the borohydride moiety was the preferentially initiating group, rather than the allyl one. The random copolymerization of l-LA and ϵ-CL was performed with complexes 1–5, in the absence or in the presence of benzyl alcohol as a chain-transfer agent, affording copolymers with ϵ-caprolactone up to 62 % inserted. The copolymers synthesized display a variety of microstructures, that is, blocky, random, or quasi-alternating.A rare find: A series of new synthesized rare-earths (RE) complexes bearing borohydrido and allyl moieties was investigated with regard to their ability of catalyzing the ring-opening polymerization of l-lactide (l-LA) and ϵ-caprolactone (ϵ-CL) (see figure) and of mixtures of both monomers, giving rise to l-LA–ϵ-CL copolymers with different compositions.
      PubDate: 2017-10-16T06:45:26.104318-05:
      DOI: 10.1002/chem.201702902
       
  • Polyhedral Oligomeric Silsesquioxane (POSS) Bearing Glyoxylic Aldehyde as
           Clickable Platform Towards Multivalent Conjugates
    • Authors: Nasreddine Kanfar; Ahmad Mehdi, Pascal Dumy, Sébastien Ulrich, Jean-Yves Winum
      Abstract: Clickable POSS glyoxylic aldehydes: A stable octafunctionalized “cubic” silsesquioxane bearing aldehyde functions was successfully prepared and isolated. This clickable hybrid platform readily reacts with oxyamine or hydrazide and provides effective access to multivalent systems. More information can be found in the Communication by S. Ulrich, J.-Y. Winum et al. (
      DOI : 10.1002/chem.201703794).
      PubDate: 2017-10-16T06:41:37.395361-05:
       
  • A pH-sensitive Macromolecular Prodrug as TLR7/8 Targeting Immune Response
           Modifier
    • Authors: Stefan Aichhorn; Anne Linhardt, Angela Halfmann, Markus Nadlinger, Stefanie Kirchberger, Manuela Stadler, Barbara Dillinger, Martin Distel, Alexander Dohnal, Ian Teasdale, Wolfgang Schöfberger
      Abstract: The chemical synthesis and biological activity of new functionalized imidazoquinoline derivatives (ImQ) to generate Toll-like receptor (TLR) 7/8 specific prodrugs are presented. In vivo activity of ImQs to induce inflammation was confirmed in zebrafish larvae. After covalent ligation to fully biodegradable polyphosphazenes (ImQ-polymer), the macromolecular prodrugs were designed to undergo intracellular pH-sensitive release of ImQs to induce inflammation through binding to endosomal TLR7/8. More information can be found in the Full Paper by M. Distel, A. Dohnal, I. Teasdale, W.  Schöfberger et al. (
      DOI : 10.1002/chem.201702942).
      PubDate: 2017-10-16T06:41:05.813553-05:
       
  • Ag1Pd1 Nanoparticles–Reduced Graphene Oxide as a Highly Efficient and
           Recyclable Catalyst for Direct Aryl C−H Olefination
    • Authors: Qiyan Hu; Xiaowang Liu, Guoliang Wang, Feifan Wang, Qian Li, Wu Zhang
      Abstract: Ag1Pd1 nanoparticles–reduced graphene oxide (Ag1Pd1-rGO) was used as highly efficient and recyclable catalyst for the chelation-assisted ortho C−H bond olefination of amides with acrylates in good yields with a broad substrate scope. The catalyst can be recovered and reused at least 5 times without losing its activity. A synergistic effect between the Ag and Pd atoms on the catalytic activity was found, and a plausible mechanism for the AgPd-rGO catalyzed C−H olefination was proposed. More information can be found in the Communication by X. Liu, W. Zhang et al. (
      DOI : 10.1002/chem.201704056).
      PubDate: 2017-10-16T06:40:50.647507-05:
       
  • Di(hydroperoxy)alkane Adducts of Phosphine Oxides: Safe, Solid,
           Stoichiometric, and Soluble Oxidizing Agents
    • Authors: Shin Hye Ahn; Nattamai Bhuvanesh, Janet Blümel
      Abstract: The most fascinating feature of novel di(hydroperoxy)alkane adducts of phosphine oxides R3PO⋅(HOO)2CR′R“ is that for all substituents R, R′, and R” large single crystals are easily obtained, enabling easy purification and characterization. There are several other advantages, including facile synthesis at ambient temperature, they can be stored on a shelf indefinitely without loss of oxidizing power, and are soluble in organic solvents. More information can be found in the Full Paper by J. Blümel et al. (
      DOI : 10.1002/chem.201703676).
      PubDate: 2017-10-16T06:40:44.522849-05:
       
  • Topological Defects in Hyperbranched Glycopolymers Enhance Binding to
           Lectins
    • Authors: Míriam Salvadó; José J. Reina, Javier Rojo, Sergio Castillón, Omar Boutureira
      Abstract: Central scaffold topology and carbohydrate density are important features in determining the binding mechanism and potency of synthetic multivalent of poly- versus monodisperse carbohydrate systems against a model plant toxin (Ricinus communis agglutinin (RCA120)). Lower densities of protein receptors favour the use of heterogeneous, polydisperse glycoconjugate presentations, as determined by surface plasmon resonance and dynamic light scattering.Central scaffold topology and carbohydrate density are important features in determining the binding mechanism and potency of synthetic multivalent of poly- versus monodisperse carbohydrate systems against a model plant toxin (Ricinus communis agglutinin (RCA120); see figure). Binding differences can be detected in both dynamic light scattering (DLS) and surface plasmon resonance (SPR) experiments.
      PubDate: 2017-10-16T06:40:41.117135-05:
      DOI: 10.1002/chem.201703432
       
  • Electrocatalytic Azide Oxidation Mediated by a Rh(PNP) Pincer Complex
    • Authors: Christophe Rebreyend; Yann Gloaguen, Martin Lutz, Jarl Ivar van der Vlugt, Inke Siewert, Sven Schneider, Bas de Bruin
      Abstract: One-electron oxidation of a PNP pincer rhodium(I)-azido complex [Rh(PNP)(N3)] leads to selective formation of a rhodium(I)–N2 complex [Rh(PNP)(N2)]+. This complex functions as a catalyst for electrochemical N3− oxidation at a milder potential than direct oxidation of N3− at a Pt electrode. The mechanism includes dimerisation of the rhodium(II)–azido intermediate followed by rapid fragmentation of the azido-bridged dimer to produce the first 0.5 equivalents of [Rh(PNP)(N2)]. A second 0.5 equivalents is formed more slowly, most likely via intramolecular azide-to-nitride attack. More information can be found in the Communication by S. Schneider, B. de Bruin et al. (
      DOI : 10.1002/chem.201702938).
      PubDate: 2017-10-16T06:40:32.874122-05:
       
  • 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. 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
       
  • Immobilised Electrocatalysts: Nafion Particles Doped with Ruthenium (II)
           Tris(2,2'-bipyridyl)
    • Authors: Haiying Yang; Xiuting Li, Christopher Batchelor-McAuley, Stanislav V. Sokolov, Enno Kätelhön, Richard G. Compton
      Abstract: Nafion particles novelly doped with ruthenium (II) tris(2,2'-bipyridyl) are synthesized by using the re-precipitation method. Characterization including SEM sizing and quantification of Ru(bpy)32+ in the Nafion particles via 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.
      PubDate: 2017-10-16T00:55:52.218484-05:
      DOI: 10.1002/chem.201704418
       
  • Reversible Oxidative Se-Se Coupling of Phosphine Selenides by Ph3Sb(OTf)2
    • Authors: Neil Burford; Maximillian Poller, Konstantin Karaghiosoff
      Abstract: Salts of diphosphoniumdiselenide dications ([R3PSeSePR3][OTf]2) have been isolated from reactions of trialkylphosphine selenides with triphenylantimony bistriflate. The redox process is speculated to proceed via a cationic coordination complex [Ph3SbL2][OTf]2 (L = Me3PSe, iPr3PSe), which is also formed in the reaction of [R3PSeSePR3][OTf]2 with Ph3Sb. The observations indicate that the reductive elimination of [R3PSeSePR3]2+ from [Ph3Sb(SePR3)2]2+ is reversible through the oxidative addition of [R3PSeSePR3]2+ to Ph3Sb.
      PubDate: 2017-10-16T00:20:20.617616-05:
      DOI: 10.1002/chem.201704753
       
  • Substitution reactions at DippBIAN supported fluoroantimony cations
           yielding cyanoantimony and azidoantimony cations
    • Authors: Neil Burford; Riccardo Suter, Christopher Frazee, Robert McDonald, Michael Ferguson
      Abstract: We present 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.
      PubDate: 2017-10-15T23:51:01.757293-05:
      DOI: 10.1002/chem.201703951
       
  • Gold-doping of double-crown Pd nanoclusters
    • Authors: 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, we successfully dope Pd4(PET)8 and Pd5(PET)10 (PET: SCH2CH2Ph) with gold and characterize the doped nanoclusters 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. And 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.
      PubDate: 2017-10-15T21:50:36.369386-05:
      DOI: 10.1002/chem.201704413
       
  • Toward Molecular Re(I) Cages : Structural and Luminescent Properties
    • Authors: Biing-Chiau Tzeng; An Chao, Mei-Chun Lin, Gene-Hsiang Lee, Ting-Shen Kuo
      Abstract: As a new synthetic approach, a versatile building block of [(Re(CO)4)3(N3S3)] (1a) can be used to react with linear dipyridyl ligands (i.e., pyrazine (pz), 4,4'-bipyridine (bpy), 1,2-di(4-pyridyl)ethylene (dpe), bis(4-pyridyl)acetylene (bpa), and 1,4-bis(pyridyl-4-ylethynyl)benzene (bpb)) and a tripyridyl one (1,3,5-tris(4-pyridylethynyl)benzene (tpb)) to afford a series of molecular cages, [(Re(CO)3)6(L)3(N3S3)2] (L = pz 2; bpy 3; bpe 4; bpa 5; bpb 6) and [(Re(CO)3)9(tpb)3(N3S3)3] (7) by solvothermal methods. Interestingly, various structural dimensions and motifs can be systematically tuned and obtained depending on different dipyridyl and tripyridyl ligands used in the reaction condition. In this regard, molecular cages of hexanuclear complexes of 2-6 containing dipyridyl ligands feature interesting trigonal-prism structures with different dimensionalities. Furthermore, the nonanuclear complex of 7 shows a novel trianglular-star structure, and three benzene rings of tpb ligands form a triple-decker arrangement with significant pi...pi interactions of 3.490(1) and 3.528(1) Å. In addition, molecular cages of 1-3 and 5-7 exhibit luminescence in the solid state, and their luminescent properties are also studied.
      PubDate: 2017-10-15T21:50:30.728997-05:
      DOI: 10.1002/chem.201704122
       
  • Electron-proton transfer mechanism of excited-state hydrogen transfer in
           phenol−(NH3)n (n = 3 and 5)
    • Authors: Mitsuhiko Miyazaki; Ryuhei Ohara, Claude Dedonder, Christophe Jouvet, Masaaki Fujii
      Abstract: Excited-state hydrogen transfer (ESHT) is responsible for various photochemical processes of aromatics, including photoprotection of nuclear basis. Its mechanism is explained by internal conversion from the aromatic ππ* to πσ* states via conical intersection. This means that the electron is transferred to a diffuse Rydberg-like σ* orbital apart from proton migration. This picture means the electron and the proton do not move together and the dynamics are different in principle. Here, we have applied picosecond time-resolved near-infrared (NIR) and infrared (IR) spectroscopies to the phenol-(NH3)5 cluster, the benchmark system of ESHT, and monitored the electron transfer and proton motion independently. The electron transfer monitored by the NIR transition rises within 3 ps, while the overall H transfer detected by the IR absorption of NH vibration appears with the lifetime of ≈20 ps. This clearly proves that the electron motion and proton migration are decoupled. Such a difference of the time-evolutions between the NIR absorption and the IR transition has not been detected in a cluster with three ammonia molecules. We will report our full observation together with theoretical calculations of the potential energy surfaces of the ππ* and πσ* states, and will discuss the ESHT mechanism and its cluster size-dependence between n = 3 and 5. It is suggested that the presence and absence of a barrier in the proton transfer coordinate cause the different dynamics.
      PubDate: 2017-10-15T20:55:32.685985-05:
      DOI: 10.1002/chem.201704129
       
  • Experimental Evaluation of (L)Au Electron Donor Ability in Cationic Gold
           Carbene Complexes
    • Authors: Ross Widenhoefer; Robert Carden, nathan lam
      Abstract: 29Si NMR spectroscopy was employed to evaluate the electron donor properties of the (L)Au fragments in the cationic gold (β,β-disilyl)vinylidene complexes [L = P(tBu)2o-biphenyl or NHC] relative to the p-substituted aryl group in the α-aryl-(β,β-disilyl)vinyl cations . Similarly, 19F NMR was employed to evaluate the σ- and π-electron donor properties of the (L)Au fragments in the neutral gold fluorophenyl complexes (L)Au(C6H4F) and in the cationic (fluorophenyl)methoxycarbene complexes [(L)AuC(OMe)(C6H4F)]+ SbF6- [L = P(t-Bu)2o-biphenyl or IPr] relative to the p-substituted aryl group of the protonated monofluorobenzophenones [(p-C6H4X)(C6H4F)COH]+ OTf-. The results of these studies indicate that relative to p-substituted aryl groups, the gold (L)Au fragments [L = P(t-Bu)2o-biphenyl or NHC] are significantly more inductively electron releasing and are comparable π-donors and for this reason, the extent of (L)Au C1 electron donation in gold carbene complexes appears to exceed that provided by a p-(dimethyamino)phenyl group. Furthermore, the [L = P(tBu)2o-biphenyl]Au fragment is a nominally stronger electron donor than is the (IPr)Au fragment while both are significantly more inductively electron releasing than are the (PPh3)Au and [P(OMe)3]Au fragments.
      PubDate: 2017-10-14T10:30:21.50487-05:0
      DOI: 10.1002/chem.201703820
       
  • Acenequinocumulenes: Lateral and vertical π-extended analogs of
           tetracyanoquinodimethane (TCNQ)
    • Authors: Marco Gruber; Kevin Padberg, Jie Min, Andreas Waterloo, Frank Hampel, Harald Maid, Tayebeh Ameri, Christoph Brabec, Rik R Tykwinski
      Abstract: We have designed a series of molecules and developed synthetic methodology that allows for the inclusion of structural diversity along both the lateral and vertical axes of the basic TCNQ skeleton. In the lateral direction, benzoannulation extends the π-system through (hetero)acene formation, while incorporation of a [3]cumulene increases delocalization vertically. The potential of these new molecules as semiconductors is explored through UV vis spectroscopy, cyclic voltammetry, X-ray crystallography, thin film formation, and mobility measurements (via space charge limited current measurements).
      PubDate: 2017-10-14T09:30:52.623351-05:
      DOI: 10.1002/chem.201704314
       
  • Vertically Aligned Co9S8 Nanotube Arrays onto Graphene Papers as
           High-Performance Flexible Electrodes for Supercapacitors
    • Authors: Xifei Li; Dongbin Xiong, Zhimin Bai, Jianwei Li, Yan Han, Dejun Li
      Abstract: The paper-like electrodes are emerging as a new category of advanced electrodes for flexible supercapacitors (SCs). Graphene, a promising two-dimensional material with high conductivity, can be easily processed into papers. Here, we report a rational design of flexible architecture with Co9S8 nanotube arrays (NAs) grown onto graphene papers (GPs) via a facile two-step hydrothermal method. When employed as a novel flexible free-standing electrode for SCs, the proposed architectured Co9S8/GPs exhibits superior electrochemical performance with ultrahigh capacitance and outstanding rate capability (469 F g-1 at 10 A g-1). These results demonstrate that the novel nanostructured Co9S8/GPs can be potentially applied in high performance flexible supercapacitors.
      PubDate: 2017-10-14T04:30:25.058509-05:
      DOI: 10.1002/chem.201704239
       
  • Activating Inert Alkali Metal Ions by Electron Transfer from Manganese
           Oxide for Formaldehyde Abatement
    • Authors: Jiayi Gao; Zhiwei Huang, Yaxin Chen, Jing Wan, Xiao Gu, Zhen Ma, Jianmin Chen, Xingfu Tang
      Abstract: Alkali metal ions often act as promoters rather than active components due to their stable outermost electronic configurations and their inert properties in heterogeneous catalysis. Herein, we activate inert alkali metal ions such as K+ and Rb+ by electron transfer from hollandite-type manganese oxide (HMO) support for HCHO oxidation. Results from synchrotron X-ray diffraction, absorption, and photoelectron spectroscopies demonstrate that the electronic density of states of single alkali metal adatoms is much higher than that of K+ or Rb+, because electrons transfer from manganese to the alkali metal adatoms through bridging lattice oxygen. The electron transfer originates from the interactions of alkali d-sp frontier orbitals with lattice oxygen sp3 orbitals occupied by lone-pair electrons. Reaction kinetics data of HCHO oxidation reveal that the high electronic density of states of single alkali metal adatoms is favorable for the activation of molecular oxygen. Mn L3-edge and O K-edge soft-X-ray absorption spectra demonstrate that lattice oxygen gains part of electrons from the Mn eg orbitals, leading to the upshift of lattice oxygen orbitals in energy. Therefore, the facile activation of molecular oxygen by the electron-abundant alkali metal adatoms and active lattice oxygen are responsible for the high catalytic activity in complete oxidation of HCHO. This work could assist the design of efficient and cheap catalysts by tuning the electronic states of active components.
      PubDate: 2017-10-14T01:30:25.421687-05:
      DOI: 10.1002/chem.201704398
       
  • Radical behavior of CO2 versus its deoxygenation promoted by vanadium
           aryloxide complexes: how the geometry of intermediate CO2-adducts
           determines the reactivity.
    • Authors: Sandro Gambarotta; camilo Viasus, Nicholas Alderman, Ilia Korobkov, Sebastiano Licciulli
      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.
      PubDate: 2017-10-13T23:31:02.660433-05:
      DOI: 10.1002/chem.201702943
       
  • Structures of a Complex Hydrazinium Lead Iodide, (N2H5)15Pb3I21,
           Possessing [Pb2I9]5-, [PbI6]4-, and I- Ions and α- and β-(N2H5)PbI3
    • Authors: Joel S. Miller; Eric Campbell, Brandon Dick, Arnold Rheingold, Chuang Zhang, Xiaojie Liu, Zeev Vardeny
      Abstract: Photovoltaic Perovskites, most notably methylammonium lead triiodide, (NH3Me)PbI3, have recently attracted considerable attention, and based upon the 'Goldschmidt Tolerance Factor' hydrazinium should be able to occupy the same cation site as methylammonium. The reaction of N2H5+I- with PbI2 in DMF results in three types of yellow crystals; hexagonal, needle-like, and rod-like, whose structures were determined at 100 K. The hexagonal [P63/m: a = 10.8906(10) Å; b = 37.845(5) Å] crystals possess isolated face sharing octahedral [Pb2I9]5-, [PbI6]4-, and I- ions. IR spectroscopy indicates the presence of hydrogen-bonded N2H5+ and the composition was determined via single crystal X-ray diffraction, density, combustion elemental analysis, and thermogravimetric analysis to be (N2H5)15Pb3I21, which is photoluminescent at 50 K, but not at room temperature. The needle and rod crystals have an orthorhombic [Pnma: a = 11.1385(7) Å; b = 4.4806(3) Å; c = 17.6241(11) Å] and hexagonal [P63/mmc: a = 8.7386(9) Å; b = 8.2006(9) Å] unit cells, respectively, possessing the Perovskite ABX3 composition of (N2H5)PbI3, but neither exhibits the Perovskite structure type. The structure of α- and β-(N2H5)PbI3 possess parallel ribbons of Pb2I4 and chains of PbI2, respectively. (N2H5)15Pb3I21 has a band gap of 2.34 eV, and both α- and β-(N2H5)PbI3 have a 2.70 eV band gap.
      PubDate: 2017-10-13T14:30:20.947152-05:
      DOI: 10.1002/chem.201704356
       
  • Directly Coupled vs. Spectator Linkers on Diimine Pt(II) Acetylides -
           Change the Structure, Keep the Function'
    • Authors: Stuart Archer; Theo Keane, Milan Delor, Elizabeth Bevon, Alexander Auty, Dimitri Chekulaev, Igor Sazanovich, Michael Towrie, Antony Meijer, Julia Weinstein
      Abstract: A series of [Donor-Acceptor-Anchor] Platinum(II) bipy (bis)acetylides has been developed in order to systematically compare the effect of conjugated vs. electronically decoupled modes of attachment of protected anchoring groups on the photophysical properties of these light-harvesting units. This first example of "decoupled" phosphonate-diimine Pt(II) complexes presented here are compared and contrasted to their carboxylate analogs. Ultrafast TRIR and femtosecond transient absorption spectroscopies revealed that all complexes possess a charge transfer lowest excited state, with lifetimes between 2 and 14 ns. Vibrational signatures and dynamics of charge-transfer states have been identified; the assignment of electronic states and their vibrational origin was aided by TDDFT calculations. Ultrafast energy re-distribution accompanied by structural changes was detected, indicating, unexpectedly, a significant difference between the structures of the electronic ground and charge-transfer excited states, as well as the differences in the structural reorganisation in the complexes bearing directly attached vs. decoupled anchoring groups. This work demonstrates that decoupling of the anchoring group from the diimine via a saturated spacer is an easy approach that permits combining higher reduction potential and 10-fold longer charge-transfer excited state lifetime with the possibility of surface attachment, whilst retaining essential charge transfer properties.
      PubDate: 2017-10-13T12:25:26.022298-05:
      DOI: 10.1002/chem.201703989
       
  • The Synergistic Effect between Triphenylpyrrole Isomers as Donors, Linking
           Groups and Acceptors on the Fluorescence Properties of D-π-A Compounds in
           the Solid State
    • Authors: Yunxiang Lei; Yueying Lai, Lichao Dong, Guojun Shang, Zhengxu Cai, Jianbing Shi, Junge Zhi, Pengfei Li, Xiaobo Huang, Bin Tong, Yuping Dong
      Abstract: Eight D-π-A compounds employing triphenylpyrrole isomers (TPP-1,2,5 and TPP-1,3,4) as donors, malononitrile (CN) and 1H-indene-1,3(2H)-dione (CO) as acceptors, pyridine (P) and benzopyran (B) as π-linker were synthesized. The compounds exhibited aggregation-induced emission and piezochromic properties. Compared with previously reported donors, triphenylpyrroles induced all the compounds to have more remarkable photophysical properties. The compounds containing TPP-1,2,5 and P moiety displayed stronger fluorescence intensities, shorter emission wavelengths, and more distinct piezochromic properties. However, the same phenomenon was observed in the TPP-1,3,4-containing system if B was as π-linker. Moreover, the CN acceptor endowed the compound to have a relatively strong fluorescent intensity, wherein CO induced a relatively long emission wavelength. That is, the photophysical properties of D-π-A compounds can be controlled through adjusting the structure of donor, linker and acceptor.
      PubDate: 2017-10-13T10:26:35.014264-05:
      DOI: 10.1002/chem.201704020
       
  • N-doped carbon nano-fibrous network derived from bacterial cellulose for
           the loading of Pt nanoparticles for methanol oxidation reaction
    • Authors: Fanshu Yuan; Yang Huang, Mengmeng Fan, Chuntao Chen, Jieshu Qian, Qingli Hao, Jiazhi Yang, Dongping Sun
      Abstract: It is still challenging to prepare Pt based catalysts with high activity and durability with low cost on a large scale for methanol oxidation reaction. The key is to look for suitable supporting materials. In this paper, we report a facile preparation of N-doped carbon nano-fibrous network by annealing a gel containing two inexpensive and eco-friendly precursors, i.e. bacterial cellulose and urea, for the loading of Pt nanoparticles. An undoped analog was also prepared for comparison. Meanwhile, we evaluated the effect of the annealing temperature on the performance of the catalysts. The results showed that the N doping and higher annealing temperature can improve the electron conductivity of the catalyst and provide more active sites for the loading of ultrafine Pt nanoparticles with narrow size distribution. Our best catalyst exhibited a remarkably high electrocatalytic activity (627 mA mg-1), excellent poison tolerance and high durability. Our work has demonstrated an ideal Pt supporting material for methanol oxidation reaction.
      PubDate: 2017-10-13T06:26:12.703874-05:
      DOI: 10.1002/chem.201704266
       
  • Cytotoxicity of Group 5 Transition Metal Ditellurides (MTe2; M=V, Nb, Ta)
    • Authors: Martin Pumera
      Abstract: Much research effort has been put in to study layered compounds with transition metal dichalcogenides (TMDs) being one of the most studied compounds. Due to their extraordinary properties such as excellent electrochemical properties, tuneable band gaps and low shear resistance due to weak van der Waals interactions between layers, TMDs have been found to have a wide application such as electrocatalyst for hydrogen evolution reactions, supercapacitors, biosensors, field-effect transistors (FETs), photovoltaic and lubricant additives. In very recent years, Group 5 transition metal ditellurides have received immense amount of research attention. However to date, little has been known of the potential toxicities posed by these materials. As such, we conducted the cytotoxicity study by incubating various concentrations of the Group 5 transition metal ditellurides (MTe2; VTe2, NbTe2, TaTe2) with human lung carcinoma epithelial A549 cells for 24 hours and the remaining cell viabilities after treatment was measured. Our findings indicate that VTe2 is highly toxic while NbTe2 and TaTe2 are deemed to exhibit mild toxicities. This study constitutes an exemplary first step towards the understanding of the Group 5 transition metal ditellurides' toxicity effects in preparation for their possible commercialization in the future.
      PubDate: 2017-10-13T06:02:03.038919-05:
      DOI: 10.1002/chem.201704316
       
  • The Coordination and Supramolecular Chemistry of Gold Metalloligands
    • Authors: Juan Gil-Rubio; José Vicente
      Abstract: This review article deals with the use of gold metalloligands as building blocks for the assembly of heterometallic complexes. Several families of gold complexes decorated with crown-ether, amide, pyridine, bipyridine, terpyridine, carboxylato, aminoacid or pi-alkyne binding sites have been reported. Adducts of these metalloligands with alkaline or transition metal cations, or transition metal or lanthanide complexes, have been isolated and structurally characterized. The reported heterometallic species range from simple dinuclear complexes to self-assembled supramolecules, coordination polymers or solids. New structural motifs have been found in these complexes. Most of these metalloligands and complexes are photoluminescent and some of them show switchable emissions based on the formation and rupture of metallophilic contacts. Potential applications as sensors, sensitizers, in vivo imaging agents and anticancer drugs are envisaged.
      PubDate: 2017-10-13T06:01:23.576638-05:
      DOI: 10.1002/chem.201703574
       
  • Straightforward design of fluorescent receptors for sulfate: study of
           non-covalent interactions contributing to host-guest formation
    • Authors: Tatiana A Shumilova; Tobias Rüffer, Heinrich Lang, Evgeny A Kataev
      Abstract: A straightforward design of receptors for binding and sensing of sulfate in aqueous medium was developed. The design involves the connection of two naphthalimide-based pH-probes through a hydrogen-bonding motif. The structure of the receptor-sulfate complex, predicted by DFT calculations, was unambiguously confirmed by NMR measurements. There are three major interactions stabilizing the host-guest complex: electrostatic interactions, hydrogen bonding and stacking interactions of the dyes. Study of two control receptors containing either one dye or methyl amide groups instead of amides, revealed that electrostatic and hydrogen bonding interactions contribute the most to affinity and selectivity of receptors. The receptors can detect sulfate in a buffered solution in pH window 3.6-4.5 demonstrating up to 7-fold fluorescence enhancement. To the best of our knowledge, the reported PET anion probes possess the largest response for sulfate in aqueous solution yet described.
      PubDate: 2017-10-13T04:31:16.556336-05:
      DOI: 10.1002/chem.201704098
       
  • Li+ Ion Conductors with Adamantane-type Nitridophosphate Anions -
           β-Li10P4N10 and Li13P4N10X3 with X = Cl, Br
    • Authors: Eva-Maria Bertschler; Christian Dietrich, Thomas Leichtweiß, Jürgen Janek, Wolfgang Schnick
      Abstract: β-Li10P4N10 and Li13P4N10X3 with X = Cl, Br were synthesized from mixtures of P3N5, Li3N, LiX, LiPN2 and Li7PN4 at temperatures below 850 °C. β-Li10P4N10 is the low temperature polymorph of α-Li10P4N10 and crystallizes in trigonal space group R3. It is made up of non-condensed [P4N10]10− T2 supertetrahedra, which are arranged in sphalerite analogous packing. Li13P4N10X3 (X = Cl, Br) crystallizes in the cubic space group Fm-3m. Both isomorphic compounds comprise adamantine-type [P4N10]10−, Li+ ions and halides, which are forming an octahedra. These octahedra build up a face centered packing, whose tetrahedral voids are occupied by the [P4N10]10− ions. The crystal structures were elucidated from X-ray powder diffraction data and corroborated by EDX measurements, solid-sate NMR and FTIR spectroscopy. Furthermore, we examined the phase transition between α- and β-Li10P4N10. To confirm the ionic character, the migration pathways of the Li+ ions were evaluated and the ion conductivity and its temperature dependence were determined by impedance spectroscopy. XPS measurements were carried out to analyze the stability against Li metal.
      PubDate: 2017-10-13T04:30:54.302679-05:
      DOI: 10.1002/chem.201704305
       
  • Versatile Tailoring of NH2-Containing Metal Organic Frameworks with Paddle
           Wheel Units
    • Authors: Xiaoqi Sun; Xiangguang Guo, Zai-Yong Zhang, Sen Qiu, Xiang Su
      Abstract: An amine containing non-interpenetrated pillar-layer framework, {[Zn2(DBTCB)(L1) (1), has been synthesized from the ligands 1,4-dibromo-2,3,5,6-tetrakis(4-carboxyphenyl)benzene (H4DBTCB) and 1,4-bis(4-pyridyl)aniline (L1). The [Zn2(COO)4] secondary building units (SBUs) was bridged by DBTCB to form two-dimensional layer, further pillared by L1 to form three-dimensional network. This NH2 framework can undergo versatile tailoring through SC-SC by post synthetic covalent modification, solvent-assisted linker exchange, transmetalation reactions. Acylamide-functionalized {[Zn2(H4DBTCB)(L2) (2) could be obtained through three ways, i.e., post synthetic reaction of 1 with acetic anhydride, direct synthesis from 1,4-bis(4-pyridyl)acylamide (L2) with H4DBTCB, solvent-assisted linker exchange using L2 to replace L1. Transmetalation reaction of 1 and 2 with CuII, NiII, CoII ions, ICP analysis revealed that 1 undergo complete SC-SC transmetalation with CuII within 30h, whereas with NiII, CoII only 70 and 80 percent subsititution. Photoluminescence studies revealed that 1 and 2 display yellow-green and ultraviolet emission under UV lamp. Furthermore, photoluminescent property could be tuned by introducing mixed pillars L1 and L2 to produce 3 displaying overall orange emission.
      PubDate: 2017-10-13T02:55:42.753281-05:
      DOI: 10.1002/chem.201703126
       
  • A new member of the inverted cucurbit[n]uril family
    • Authors: Kai - Chen; Xin-Xin wang, Fang-Fang shen, Zi-Yi Hua, Sheng-Chao Qiu, Yun-Qian Zhang, Hang Cong, Qing-yun Liu, Zhu Tao, Xiao Xin
      Abstract: A new inverted cucurbituril, namely inverted hexamethylcucurbit[3,3]uril (iMe6Q[3,3]), has been isolated and characterized. It incorporates a single inverted un-substituted glycoluril unit oriented towards the interior of the cavity, shows good solubility in water and organic solvents (DMSO), and exhibits different selecties for guests to those of iQ[6] and other known Q[6]s.
      PubDate: 2017-10-12T22:55:36.717579-05:
      DOI: 10.1002/chem.201704069
       
  • Role of the Diphosphine Chelate in Emissive, Charge-Neutral Iridium(III)
           Complexes
    • Authors: Jia-Ling Liao; Leon Devereux, Mark A. Fox, Chun-Chieh Yang, Yu-Cheng Chiang, Chih-Hao Chang, Gene-Hsiang Lee, Yun Chi
      Abstract: A class of neutral tris-bidentate Ir(III) metal complexes incorporating a diphosphine as a chelate is prepared and characterized here for the first time. Treatment of [Ir(dppb)(tht)Cl3] (1) with fppzH afforded the dichloride complexes, trans-(Cl,Cl)[Ir(dppb)(fppz)Cl2] (2) and cis-(Cl,Cl)[Ir(dppb)(fppz)Cl2] (3). The reaction of 3 with the dianionic chelate precursor bipzH2 or mepzH2, in DMF gave the complex [Ir(dppb)(fppz)(bipz)] (4) or [Ir(dppb)(fppz)(mepz)] (5), respectively. In contrast, a hydride complex [Ir(dppb)(fppz)(bipzH)H] (6) was isolated instead of 4 in protic solvent, namely: DGME. All complexes 2 - 6 are luminescent in powder forms and thin films where the dichlorides (2, 3) emit with maxima at 590-627 nm (orange) and quantum yields (Q.Y.s) up to 90% whereas the tris-bidentate (4, 5) and hydride (6) complexes emit at 455-458 nm (blue) with Q.Y.s up to 70%. Hybrid TD-DFT calculations showed considerable MLCT contribution to the orange-emitting 2 and 3 but substantial ligand-centered 3ππ* transition character in the blue-emitting 4 - 6. The dppb does not participate to these radiative transitions in 4 - 6, but it provides the rigidity and steric bulk needed to promote the luminescence by suppressing the self-quenching in the solid state. Fabrication of an OLED with dopant 5 gave a deep blue CIE chromaticity of (0.16, 0.15). Superior blue emitters, which are vital in OLED applications, may be found in other neutral Ir(III) complexes containing phosphine chelates.
      PubDate: 2017-10-12T22:55:25.049512-05:
      DOI: 10.1002/chem.201703482
       
  • Multifaceted Supramolecular Interactions from C-methylresorcin[4]arene
           
    • Authors: Arnab Dawn; Harish Chandra, Chandra Ade-Browne, Jagjit Yadav, Harshita Kumari
      Abstract: Mimicking the antibacterial activity of polyphenols in synthetic systems is an attractive approach for the development of novel active pharmaceutical ingredients. Resorcinarenes represent a class of polyphenols which have been exploited for decades for their attractive chemical scaffold suitable for forming host-guest complexes with hydrophobic guest molecules. However, the polyphenolic character of resorcinarenes, which could be a potential asset to the pharmaceutical industry, have been least exploited. The present work represents an unprecedented interplay of chemical nature of resorcinarene conferring an antimicrobial activity together with its ability to interact with an antibacterial drug gatifloxacin, improving the overall antibacterial activity. The chemistry, and the clinical activities involved in this study, are investigated simultaneously with the help of spectroscopic techniques, and in vitro measurement of antibacterial activity toward two human bacterial pathogens, a gram-positive pathogen Staphylococcus aureus and a gram-negative lung pathogen Legionella pneumophila. The initial positive result obtained from this study could revolutionize the use of synthetically modifiable resorcinarenes and their analogues in fine-tuning the clinical behavior of drugs.
      PubDate: 2017-10-12T22:25:25.545667-05:
      DOI: 10.1002/chem.201704291
       
  • Front Cover: High-Energy-Resolution X-ray Absorption Spectroscopy for
           Identification of Reactive Surface Species on Supported Single-Site
           Iridium Catalysts (Chem. Eur. J. 59/2017)
    • Authors: Adam S. Hoffman; Dimosthenis Sokaras, Shengjie Zhang, Louise M. Debefve, Chia-Yu Fang, Alessandro Gallo, Thomas Kroll, David A. Dixon, Simon R. Bare, Bruce C. Gates
      Pages: 14665 - 14665
      Abstract: High-energy-resolution fluorescence detection (HERFD) X-ray absorption spectroscopy at SSRL is combined with density functional theory and FEFF simulations ascribing spectral features to ethylene and CO ligands adsorbed on catalytically active iridium centers isolated on zeolite HY and on MgO, pushing detection limits below those of conventional infrared spectroscopy, and allowing XAS to identify reactionary intermediates. More information can be found in the Full Paper by D. A. Dixon, S. R. Bare, B. C. Gates et al. on page 14760.
      PubDate: 2017-08-09T07:46:47.338618-05:
      DOI: 10.1002/chem.201703473
       
  • Cover Feature: Tuning the Porphyrin Building Block in Self-Assembled Cages
           for Branched-Selective Hydroformylation of Propene (Chem. Eur. J. 59/2017)
           
    • Authors: Xiaowu Wang; Sandra S. Nurttila, Wojciech I. Dzik, René Becker, Jody Rodgers, Joost N. H. Reek
      Pages: 14666 - 14666
      Abstract: Highly branched-selective hydroformylation of propene is an industrially important transformation, which now can be achieved using a novel caged rhodium catalyst. The catalyst encapsulation is based on a ligand-template approach in which the second coordination sphere around the encapsulated catalyst is generated by coordination of the catalyst's ligand to ZnII-porpholactone moieties surrounding it. As the ZnII-porpholactone binds more strongly than the previously used ZnII-TPP analogue, the hydroformylation reaction can now also be carried out in polar solvents. More information can be found in the Full Paper by J. N. H. Reek et al. on page 14769.
      PubDate: 2017-08-22T11:57:30.516049-05:
      DOI: 10.1002/chem.201703135
       
  • Cover Feature: Activatable Near-Infrared Probe for Fluorescence Imaging of
           γ-Glutamyl Transpeptidase in Tumor Cells and In Vivo (Chem. Eur. J.
           59/2017)
    • Authors: Zhiliang Luo; Liandong Feng, Ruibing An, Guanfu Duan, Runqi Yan, Hua Shi, Jian He, Zhengyang Zhou, Changge Ji, Hong-Yuan Chen, Deju Ye
      Pages: 14667 - 14667
      Abstract: An activatable near-infrared probe was developed by linking of a γ-glutamyl transpeptidase (GGT)-recognitive substrate, and a near infrared (NIR) fluorophore with a self-immolative linker. The probe was stable and could generate significant turn-on fluorescence in response to GGT. The probe was used for the real-time imaging of GGT activity and screening of GGT inhibitors both in live tumor cells and mice, allowing for the study and diagnosis of GGT-related diseases. More information can be found in the Full Paper by D. Ye et al. on page 14778.
      PubDate: 2017-08-22T11:57:10.071848-05:
      DOI: 10.1002/chem.201703472
       
  • Cover Feature: Testing the Limits of the BOPHY Platform: Preparation,
           Characterization, and Theoretical Modeling of BOPHYs and Organometallic
           BOPHYs with Electron-Withdrawing Groups at β-Pyrrolic and Bridging
           Positions (Chem. Eur. J. 59/2017)
    • Authors: Yuriy V. Zatsikha; Dion B. Nemez, Rebecca L. Davis, Simarpreet Singh, David E. Herbert, Alex J. King, Christopher J. Ziegler, Victor N. Nemykin
      Pages: 14668 - 14668
      Abstract: As part of our continuing investigations into the BOPHY fluorophore, we have started to explore the cyanation of derivatives both with and without ferrocene. Upon functionalization of BOPHY with cyanide, however, extrusion of a BF2 unit is observed, resulting in a “half-BOPHY” compound, which exhibits reduced emission. The introduction of a CN unit reduces the basicity of the bridging hydrazine. More information can be found in the Full Paper by V. N. Nemykin et al. on page 14786.
      PubDate: 2017-08-30T11:18:40.479927-05:
      DOI: 10.1002/chem.201703947
       
  • High-Energy-Resolution X-ray Absorption Spectroscopy for Identification of
           Reactive Surface Species on Supported Single-Site Iridium Catalysts
    • Authors: Adam S. Hoffman; Dimosthenis Sokaras, Shengjie Zhang, Louise M. Debefve, Chia-Yu Fang, Alessandro Gallo, Thomas Kroll, David A. Dixon, Simon R. Bare, Bruce C. Gates
      Pages: 14669 - 14669
      Abstract: Invited for the cover of this issue are the groups of David A. Dixon at the University of Alabama, Simon R. Bare at Stanford Synchrotron Radiation Lightsource and Bruce C. Gates at the University of California, Davis. The image depicts a visual representation of the key conclusion of the work. Read the full text of the article at 10.1002/chem.201701459.“Using high-energy resolution fluorescence detection (HERFD) X-ray absorption spectroscopy (XAS) we have been able to demonstrate that there are unique features in the spectra that can be assigned to specific ligands bound to a catalytic iridium center.” Read more about the story behind the cover in the Cover Profile and about the research itself on page 14760 ff. (
      DOI : 10.1002/chem.201701459).
      PubDate: 2017-08-16T13:10:28.261696-05:
       
  • Recent Advances in Conjugated Furans
    • Authors: Hongda Cao; Paul A. Rupar
      Pages: 14670 - 14675
      Abstract: Thiophene is one of the most ubiquitous moieties in organic conjugated materials; however, furan, its oxygen congener, and furan derivatives have received comparatively less attention. This is primarily due to the intrinsic instability of furan and its tendency to decompose in the presence of oxygen and light. Incorporating furan into conjugated systems can confer many benefits, including increases in conjugation, improved solubility, and better transport properties. In this Concept Article, advances in furan-containing conjugated materials are presented. The impact of furan on the properties of conjugated materials is discussed, recent advances in synthetic methods are overviewed, and strategies for improving the stability of conjugated furans are detailed.Furan versus thiophene: This Concept Article presents recent advances in furans containing conjugated materials. The impact of furan on the properties of conjugated systems is discussed, recent synthetic advances presented, and strategies for improving the stability of conjugated furans presented.
      PubDate: 2017-09-27T09:55:05.62477-05:0
      DOI: 10.1002/chem.201703355
       
  • Difluoromethylation Reactions of Organic Compounds
    • Authors: Damian E. Yerien; Sebastian Barata-Vallejo, Al Postigo
      Pages: 14676 - 14701
      Abstract: The relevance of the -CF2H moiety has attracted considerable attention from organic synthetic and medicinal chemistry communities, because this group can act as a more lipophilic isostere of the carbinol, thiol, hydroxamic acid, or amide groups. Being weakly acidic, the CF2H moiety can establish hydrogen-bonding interactions to improve the binding selectivity of biologically active compounds. Therefore, the hydroxyl, amino, and thio substituents of lead structures are routinely replaced by a CF2H motif in drug discovery, with great benefits in the pharmacological activity of drugs and drug candidates and agrochemicals. Consequently, the late-stage introduction of CF2H is a sought-after strategy in designing bioactive compounds. Secondly, but nonetheless relevant and meaningful, is the study of synthetic pathways to introduce a CF2−Y moiety (Y≠H, F) into organic substrates because compounds that contain a CF2−Y functionality have also found vast applications in medicinal chemistry and in other areas, such as that of fungicides, insecticides, etc., and thus, this functionality deserves special attention. Although emphasis is made on difluoromethylation strategies to functionalize different families of organic compounds, three main methodological protocols will be presented in this review article for the late-stage introduction of a CF2H or CF2Y moieties into organic substrates: i) a metal-photoredox catalysis; ii) through transition metal-catalyzed thermal protocols; and iii) from transition-metal-free strategies.Put fluorine on it: The difluoromethylation reactions of (hetero)aromatics, olefins, alkynes, alcohols, carbonyl compounds, amines and hydrazones are achieved through the use of different CF2H reagents.
      PubDate: 2017-08-25T05:21:15.007101-05:
      DOI: 10.1002/chem.201702311
       
  • Indole- and Pyrrole-BX: Bench-Stable Hypervalent Iodine Reagents for
           Heterocycle Umpolung
    • Authors: Paola Caramenti; Stefano Nicolai, Jerome Waser
      Pages: 14702 - 14706
      Abstract: The one-step synthesis of the bench-stable hypervalent iodine reagents IndoleBX and PyrroleBX using mild Lewis acid catalyzed conditions is reported. The new reagents are stable up to 150 °C and were applied in the C−H arylation of unactivated arenes using either rhodium or ruthenium catalysts. A broad range of heterocyclic systems of high interest for synthetic and medicinal chemistry was accessed in high yields. The developed C−H functionalization could not be achieved using reported reagents or methods, highlighting the unique reactivity of Indole- and Pyrrole-BX.Electrophilic Indoles/Pyrroles: The first synthesis of indole- and pyrrole-derived benziodoxole reagents in one step from the heterocycles is reported. The new indole- and pyrrole-BX reagents are stable up to 150 °C and can be used for selective heterocycle transfer onto the C−H bonds of arenes ortho to directing groups by using rhodium or ruthenium catalysts.
      PubDate: 2017-08-30T11:18:58.514465-05:
      DOI: 10.1002/chem.201703723
       
  • Catalytic Asymmetric Formal [3+2] Cycloaddition of 2-Isocyanatomalonate
           Esters and Unsaturated Imines: Synthesis of Highly Substituted Chiral
           γ-Lactams
    • Authors: Miguel Espinosa; Gonzalo Blay, Luz Cardona, M. Carmen Muñoz, José R. Pedro
      Pages: 14707 - 14711
      Abstract: Unlike their isocyano and isothiocyanato analogues, isocyanato esters remain almost unexplored as formal 1,3-dipoles in asymmetric catalytic reactions. The first asymmetric formal [3+2] cycloaddition involving isocyanato esters and electrophilic alkenes is reported. Diisopropyl 2-isocyanatomalonate reacts with α,β-unsaturated N-(o-anisidyl) imines in the presence of a Mg(OTf)2–BOX complex to give highly substituted chiral pyrrolidinones featuring a conjugate exocyclic double bond with excellent yields and enantiomeric excesses up to 99 %. Several transformations of the resulting heterocycles, including the synthesis of a pyroglutamic acid derivative, have been carried out.Close the ring: The first asymmetric formal [3+2] cycloaddition involving 2-isocyanato esters and electrophilic alkenes is reported. Diisopropyl 2-isocyanatomalonate reacts with α,β-unsaturated N-(o-anisidyl) imines in the presence of a Mg(OTf)2–BOX complex to give highly substituted chiral pyrrolidinones with excellent yields and enantiomeric excesses up to 99 % (see scheme).
      PubDate: 2017-09-21T08:55:49.929546-05:
      DOI: 10.1002/chem.201702777
       
  • Fabrication of Photocontrolled Surfaces for Oil/Water Separation through
           Sulfur(VI) Fluoride Exchange
    • Authors: Haiguang Zhu; Dongyun Chen, Najun Li, Qingfeng Xu, Hua Li, Jinghui He, Hua Wang, Peng Wu, Jianmei Lu
      Pages: 14712 - 14717
      Abstract: Smart surfaces with controllable wettability have attracted substantial interest owing to the potential use of these materials for the separation of oil from oily water caused by frequent oil-spill accidents. Because there are few separation materials on the market that are capable of switching between hydrophobicity and hydrophilicity, this work reports an efficient and low-cost method to fabricate a photoresponsive membrane through the sulfur(VI) fluoride exchange reaction (SuFEx) between poly(4-vinylphenol sulfofluoridate) and (E)-1-(4-(tert-butoxy)phenyl)-2-(4-(trifluoromethoxy)phenyl)diazene. The resulting material displays switchable wettability between hydrophobic and hydrophilic states when subjected to ultraviolet or visible irradiation. This membrane can be recycled (greater than five times) and features superior efficiency (up to 97.9 %) for the separation of oils that have both higher and lower densities than water. This work is the first proof-of-concept application of SuFEx to fabricate functional materials for environmental remediation.An intelligent polymer with switchable wettability was synthesized through a click reaction (sulfur(VI) fluoride exchange reaction) between silylated compounds containing an azobenzene structure and fluorinated polymer (poly(4-vinylphenol sulfofluoridate)). The azobenzene derivative on the surface of the polymer provides it with photoswitchable wettability between hydrophobicity and hydrophilicity by adjusting UV or visible light irradiation.
      PubDate: 2017-09-26T09:44:08.984774-05:
      DOI: 10.1002/chem.201703309
       
  • Heptazine: an Electron-Deficient Fluorescent Core for Discotic Liquid
           Crystals
    • Authors: Indu Bala; Harpreet Singh, Venugopala Rao Battula, Santosh Prasad Gupta, Joydip De, Sunil Kumar, Kamalakannan Kailasam, Santanu Kumar Pal
      Pages: 14718 - 14722
      Abstract: Herein, room-temperature discotic liquid crystals based on heptazine, an electron deficient central core, are reported for the first time. Mesomorphic behaviors of the materials are also investigated. Supramolecular assembly of the mesophase derivatives were confirmed by X-ray scattering experiments. Heptazine-based solid thin films are strong blue light emitters, whereas in the solution state, they are weakly emissive or non-emissive. The band gap energy is found to be low in this class of compounds. Formation of room-temperature mesophases, low band-gap behavior, and strong blue-light emission in the solid state are promising attributes for optoelectronic applications of the materials.Solidly fluorescent: room-temperature discotic liquid crystals based on heptazine, an electron-deficient and photoluminescent central core, are reported for the first time. Their mesomorphic behaviors are also investigated.
      PubDate: 2017-10-06T05:41:02.39916-05:0
      DOI: 10.1002/chem.201703364
       
  • An Imide-Based Pentacyclic Building Block for n-Type Organic
           Semiconductors
    • Authors: Fu-Peng Wu; Hio-Ieng Un, Yongxi Li, Hailiang Hu, Yi Yuan, Bin Yang, Kai Xiao, Wei Chen, Jie-Yu Wang, Zuo-Quan Jiang, Jian Pei, Liang-Sheng Liao
      Pages: 14723 - 14727
      Abstract: A new electron-deficient unit with a fused 5-membered heterocyclic ring was developed by replacing a cyclopenta-1,3-diene from electron-rich donor indacenodithiophene (IDT) with a cyclohepta-4,6-diene-1,3-diimde unit. The imide bridge endows dithienylbenzenebisimide (BBI) with a fixed planar configuration and low energy levels for both the highest occupied molecular orbital (HOMO; −6.24 eV) and the lowest unoccupied molecular orbit (LUMO; −2.57 eV). Organic field-effect transistors (OFETs) based on BBI polymers exhibit electron mobility up to 0.34 cm2 V−1 s−1, which indicates that the BBI is a promising n-type building block for optoelectronics.The FET controller: an electron-deficient building block with a fused 5-membered dithienylbenzenebisimide (BBI) ring was synthesized by replacing a cyclopenta-1,3-diene moiety of indacenodithiophene (IDT) with a cyclohepta-4,6-diene-1,3-diimde unit. The imide bridge endows BBI with a fixed planar configuration and both low HOMO and LUMO energy levels. The polymers based on BBI show good n-type characteristics in OFET devices with the best electron mobility up to 0.34 cm2 V−1 s−1 measured under aerobic, ambient conditions.
      PubDate: 2017-10-09T02:21:42.322414-05:
      DOI: 10.1002/chem.201703415
       
  • Synthesis and Reactivity of a Scandium Terminal Hydride: H2 Activation
           by a Scandium Terminal Imido Complex
    • Authors: Xianghao Han; Li Xiang, Carlos A. Lamsfus, Weiqing Mao, Erli Lu, Laurent Maron, Xuebing Leng, Yaofeng Chen
      Pages: 14728 - 14732
      Abstract: Dihydrogen is easily activated by a scandium terminal imido complex containing the weakly coordinated THF. The reaction proceeds through a 1,2-addition mechanism, which is distinct from the σ-bond metathesis mechanism reported to date for rare-earth metal-mediated H2 activation. This reaction yields a scandium terminal hydride, which is structurally well-characterized, being the first one to date. The reactivity of this hydride is reported with unsaturated substrates, further shedding light on the existence of the terminal hydride complex. Interestingly, the H2 activation can be reversible. DFT investigations further eludciate the mechanistic aspects of the reactivity of the scandium anilido-terminal hydride complex with PhNCS but also on the reversible H2 activation process.Reversible activation: Activation of H2 by scandium terminal imido complex through 1,2-addition provided the first structurally characterized scandium terminal hydride. DFT investigations further highlighted the easiness of H−H bond cleavage over the Sc=N double bond. This hydride can also release H2 to regenerate the imido complex, making the H2 activation reversible.
      PubDate: 2017-09-22T06:21:57.091093-05:
      DOI: 10.1002/chem.201703905
       
  • C−H Cyanation of 6-Ring N-Containing Heteroaromatics
    • Authors: Bryony L. Elbert; Alistair J. M. Farley, Timothy W. Gorman, Tarn C. Johnson, Christophe Genicot, Bénédicte Lallemand, Patrick Pasau, Jakub Flasz, José L. Castro, Malcolm MacCoss, Robert S. Paton, Christopher J. Schofield, Martin D. Smith, Michael C. Willis, Darren J. Dixon
      Pages: 14733 - 14737
      Abstract: Heteroaromatic nitriles are important compounds in drug discovery, both for their prevalence in the clinic and due to the diverse range of transformations they can undergo. As such, efficient and reliable methods to access them have the potential for far-reaching impact across synthetic chemistry and the biomedical sciences. Herein, we report an approach to heteroaromatic C−H cyanation through triflic anhydride activation, nucleophilic addition of cyanide, followed by elimination of trifluoromethanesulfinate to regenerate the cyanated heteroaromatic ring. This one-pot protocol is simple to perform, is applicable to a broad range of decorated 6-ring N-containing heterocycles, and has been shown to be suitable for late-stage functionalization of complex drug-like architectures.A direct, reliable and general one-pot N-heteroaromatic C−H cyanation procedure by triflic anhydride N-activation, nucleophilic addition of cyanide, and concomitant elimination of trifluoromethanesulfinate is reported. The protocol is simple to perform, has computationally predictable site selectivity, and is applicable to a broad range of decorated 6-ring N-containing heterocycles, including complex drug-like architectures.
      PubDate: 2017-09-22T06:22:05.735886-05:
      DOI: 10.1002/chem.201703931
       
  • Dichloro-Cycloazatriphosphane: The Missing Link between N2P2 and P4 Ring
           Systems in the Systematic Development of NP Chemistry
    • Authors: Jonas Bresien; Alexander Hinz, Axel Schulz, Tim Suhrbier, Max Thomas, Alexander Villinger
      Pages: 14738 - 14742
      Abstract: A dichloro-cycloazatriphosphane that incorporates a cyclic NP3 backbone could be synthesized using knowledge gained from the chemistry of N2P2 and P4 ring systems. It fills the gap between the congeneric compounds [ClP(μ-NR)]2 and [ClP(μ-PR)]2 (R=sterically demanding substituent), and thus contributes to the systematic development of nitrogen–phosphorus chemistry in general. The title compound was studied with respect to its formation via a labile aminodiphosphene, which readily underwent different rearrangement reactions depending on the solvent. All compounds were fully characterized by experimental and computational methods.NP3 ring system: Starting from a highly reactive amino-diphosphene, a dichloro-cycloazatriphosphane (see Scheme) could be synthesized and fully characterized. This new ring system can be regarded as a congener of [XP(μ-NR)]2 and [XP(μ-PR)]2 systems and therefore contributes to a systematic development of NP chemistry.
      PubDate: 2017-10-09T02:06:22.361167-05:
      DOI: 10.1002/chem.201704278
       
  • Total Synthesis of the Diglycosidic Tetramic Acid Ancorinoside A
    • Authors: Markus Petermichl; Rainer Schobert
      Pages: 14743 - 14746
      Abstract: Ancorinoside A, a metabolite of a sponge Ancorina sp., was prepared in 18 steps as the first derivative of this class of glycosylated 3-acyltetramic acids. It features a β-d-glucopyranosyl-(14)-β-d-galacturonic acid linked to a d-aspartic acid derived tetramic acid via a 3-docosanoyl spacer. The diglycoside was built up by connecting the protected monosaccharides d-galactose and d-glucose via a thioglycoside glycosylation. Attachment of the spacer by a subsequent Schmidt glycosylation of this diglycoside, TEMPO oxidation to the uronic acid, functionalisation of the spacer terminus with an N-(β-ketoacyl)aspartate, and a final Dieckmann cyclisation were the key steps leading to ancorinoside A. This approach should also allow access to ancorinoside D.Sweet ′n sour: The marine sponge metabolite ancorinoside A was synthesised in 18 steps and 1.6 % yield as the first natural diglycosylated pyrrolidin-2,4-dione. Remarkably, it is comprised of a d-configured aspartic acid, a galacturonic acid and a 3-acyltetramic acid.
      PubDate: 2017-10-06T02:41:32.926847-05:
      DOI: 10.1002/chem.201704379
       
  • Structure–Property Relationship Study of Donor and Acceptor
           2,6-Disubstituted BODIPY Derivatives for High Performance Dye-Sensitized
           Solar Cells
    • Authors: Shih-Chieh Yeh; Li-Jing Wang, Hong-Ming Yang, Yu-Huei Dai, Chao-Wen Lin, Chin-Ti Chen, Ru-Jong Jeng
      Pages: 14747 - 14759
      Abstract: Seven donor and acceptor 2,6-disubstituted 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dyes have been synthesized and characterized. Including MPBTCA, which is a known compound, the seven BODIPY dyes have been characterized by varied physical methods, such as UV/Visible absorption spectroscopy, low energy photo-electron spectroscopy (AC-2), and HOMO-LUMO DFT/TDDFT calculation. All seven BODIPY dyes have absorption λmax around 535–545 nm, which is significantly longer than 499 nm of 4,4-difluoro-1,3,5,7,8-pentamethyl-4-bora-3a,4a-diaza-s-indacene (PM 546). Having structural variation on donor group, acceptor group, donor π-spacer, acceptor π-spacer, and the substituent on boron, some BODIPY dyes exhibit small extinction coefficients or spectral integrals in solution (MPCtBTCA, MPBT-pyO, MPBTT-pyO, MTBTCA), broadening absorption spectral profile (MTBTCA), weak intramolecular charge transfer characteristics (MPBT-pyO, MPBTT-pyO, MTBTCA), too low LUMO energy level (PPBTCA), or insufficient dye-uptake by TiO2 FTO (MPBT-pyO, MPBTT-pyO, MTBTCA). Two of the seven BODIPY dyes, MPBTCA and MPBTTCA, do not show the adverse properties like other BODIPY dyes. With our improved TiO2 FTO (fluorine doped tin oxide) dyeing method, namely a solution dropping method, high performance dye-sensitized solar cells (DSCs) have been realized by MPBTCA and MPBTTCA photosensitizers. Power conversion efficiencies of 6.3 and 6.4 % have been achieved by MPBTCA and MPBTTCA DSCs, respectively. To the best of our knowledge, MPBTCA and MPBTTCA are the most efficient dyes for the donor and acceptor 2,6-disubstituted BODIPY DSCs so far.Dyeing to meet you: A series of 2,6-disubstituted BODIPY derivatives have been synthesized and characterized, and subsequently tested for use in dye-sensitized solar cells. Theoretical calculations and spectroscopic data suggest reasons for the improved performance, including a power conversion efficiency as high as 6.4% for MPBTTCA.
      PubDate: 2017-09-25T03:14:25.143817-05:
      DOI: 10.1002/chem.201702285
       
  • High-Energy-Resolution X-ray Absorption Spectroscopy for Identification of
           Reactive Surface Species on Supported Single-Site Iridium Catalysts
    • Authors: Adam S. Hoffman; Dimosthenis Sokaras, Shengjie Zhang, Louise M. Debefve, Chia-Yu Fang, Alessandro Gallo, Thomas Kroll, David A. Dixon, Simon R. Bare, Bruce C. Gates
      Pages: 14760 - 14768
      Abstract: We report high-energy-resolution X-ray absorption spectroscopy detection of ethylene and CO ligands adsorbed on catalytically active iridium centers isolated on zeolite HY and on MgO supports. The data are supported by density functional theory and FEFF X-ray absorption near-edge modelling, together with infrared (IR) spectra. The results demonstrate that high-energy-resolution X-ray absorption spectra near the iridium LIII (2p3/2) edge provide clearly ascribable, distinctive signatures of the ethylene and CO ligands and illustrate effects of supports and other ligands. This X-ray absorption technique is markedly more sensitive than conventional IR spectroscopy for characterizing surface intermediates, and it is applicable to samples having low metal loadings and in reactive atmospheres and is expected to have an increasing role in catalysis research by facilitating the determination of mechanisms of solid-catalyzed reactions through identification of reaction intermediates in working catalysts.Beam me up, Scotty! High-energy-resolution X-ray absorption spectroscopy is combined with density functional theory and FEFF simulations ascribing spectral features to adsorbates on single-site supported iridium catalyst, pushing detection limits below those of conventional infrared spectroscopy.
      PubDate: 2017-07-27T07:40:32.005734-05:
      DOI: 10.1002/chem.201701459
       
  • Tuning the Porphyrin Building Block in Self-Assembled Cages for
           Branched-Selective Hydroformylation of Propene
    • Authors: Xiaowu Wang; Sandra S. Nurttila, Wojciech I. Dzik, René Becker, Jody Rodgers, Joost N. H. Reek
      Pages: 14769 - 14777
      Abstract: Unprecedented regioselectivity to the branched aldehyde product in the hydroformylation of propene was attained on embedding a rhodium complex in supramolecular assembly L2, formed by coordination-driven self-assembly of tris(meta-pyridyl)phosphine and zinc(II) porpholactone. The design of cage L2 is based on the ligand-template approach, in which the ligand acts as a template for cage formation. Previously, first-generation cage L1, in which zinc(II) porphyrin units were utilized instead of porpholactones, was reported. Binding studies demonstrate that the association constant for the formation of second-generation cage L2 is nearly an order of magnitude higher than that of L1. This strengthened binding allows cage L2 to remain intact in polar and industrially relevant solvents. As a consequence, the unprecedented regioselectivity for branched aldehyde products can be maintained in polar and coordinating solvents by using the second-generation assembly.Cage-controlled catalysis: The self-assembly of tris(m-pyridyl)phosphine and three zinc porpholactone units yields a supramolecular cage that is stable in both nonpolar and polar solvents. Coordination to rhodium(I) affords a catalyst that is capable of unprecedented branched-selective hydroformylation of propene in industrially relevant solvents (see figure).
      PubDate: 2017-08-17T06:51:13.389927-05:
      DOI: 10.1002/chem.201702113
       
  • Activatable Near-Infrared Probe for Fluorescence Imaging of γ-Glutamyl
           Transpeptidase in Tumor Cells and In Vivo
    • Authors: Zhiliang Luo; Liandong Feng, Ruibing An, Guanfu Duan, Runqi Yan, Hua Shi, Jian He, Zhengyang Zhou, Changge Ji, Hong-Yuan Chen, Deju Ye
      Pages: 14778 - 14785
      Abstract: γ-Glutamyl transpeptidase (GGT) is a cell-membrane-bound enzyme that is involved in various physiological and pathological processes and is regarded as a potential biomarker for many malignant tumors, precise detection of which is useful for early cancer diagnosis. Herein, a new GGT-activatable near-infrared (NIR) fluorescence imaging probe (GANP) by linking of a GGT-recognitive substrate γ-glutamate (γ-Glu) and a NIR merocyanine fluorophore (mCy-Cl) with a self-immolative linker p-aminobenzyl alcohol (PABA) is reported. GANP was stable under physiological conditions, but could be efficiently activated by GGT to generate ≈100-fold enhanced fluorescence, enabling high sensitivity (detection limit of ≈3.6 mU L−1) and specificity for the real-time imaging of GGT activity as well as rapid evaluation of the inhibition efficacy of GGT inhibitors in living tumor cells. Notably, the deep tissue penetration ability of NIR fluorescence could further allow GANP to image GGT in frozen tumor tissue slices with large penetration depth (>100 μm) and in xenograft tumors in living mice. This GGT activatable NIR fluorescence imaging probe could facilitate the study and diagnosis of other GGT-correlated diseases in vivo.A γ-glutamyl transpeptidase (GGT) activatable NIR fluorescence probe (GANP) was developed, allowing for real-time imaging of endogenous GGT activity both in tumor cells and living mice with high sensitivity and specificity.
      PubDate: 2017-08-18T01:35:49.344366-05:
      DOI: 10.1002/chem.201702210
       
  • Testing the Limits of the BOPHY Platform: Preparation, Characterization,
           and Theoretical Modeling of BOPHYs and Organometallic BOPHYs with
           Electron-Withdrawing Groups at β-Pyrrolic and Bridging Positions
    • Authors: Yuriy V. Zatsikha; Dion B. Nemez, Rebecca L. Davis, Simarpreet Singh, David E. Herbert, Alex J. King, Christopher J. Ziegler, Victor N. Nemykin
      Pages: 14786 - 14796
      Abstract: Several BOPHY derivatives with and without ferrocene fragments, and with electron-withdrawing ester groups appended to the β-pyrrolic positions have been prepared and characterized by NMR, UV/Vis near-infrared (NIR), high-resolution mass spectrometry, and fluorescence spectroscopy, as well as X-ray crystallography. The redox properties of new BOPHYs were probed by electrochemical (cyclic and differential pulse voltammetry) and spectroelectrochemical methods. In an attempt to prepare BOPHY derivatives with a cyano group at the bridging position using a similar approach for BODIPY cyanation, adducts from the nucleophilic attack of the cyanide anion on the bridging position in BOPHY have been isolated and characterized by spectroscopic methods. Oxidation of such adducts, however, resulted in formation of either the starting BOPHYs, or partial extrusion of the BF2 fragment from the BOPHY core, which was confirmed by spectroscopy and X-ray crystallography. DFT and TDDFT calculations on all target materials correlate well with the experimental data, and suggest the dramatic reduction of the nitrogen atom basicity at the hydrazine bridge of the BOPHY upon introduction of the cyano group at the bridging-carbon atom.Light of my life: Several organic and organometallic BOPHYs were prepared and characterized by experimental and theoretical methods during an attempt to prepare a BOPHY core with cyano-groups located at the bridging-position. The limitations of the BOPHY platform were discussed in conjunction with their electronic structures.
      PubDate: 2017-08-10T10:46:08.830847-05:
      DOI: 10.1002/chem.201702597
       
  • Helicity-Dependent Regiodifferentiation in the Excited-State Quenching and
           Chiroptical Properties of Inward/Outward Helical Coumarins
    • Authors: Arindam Mukhopadhyay; Tousif Hossen, Indrajit Ghosh, Apurba Lal Koner, Werner M. Nau, Kalyanasis Sahu, Jarugu Narasimha Moorthy
      Pages: 14797 - 14805
      Abstract: Influence of helicity on the excited-state as well as chiroptical properties of two sets of regiohelical coumarins that are differentiated by “inward” and “outward” disposition of the pyran-2-one ring has been investigated. A subtle difference in the helicities manifests in divergent excited-state properties and significant differences in the dipole moments. The latter permit heretofore unprecedented regiodifferentiation in the O−H⋅⋅⋅O hydrogen-bond assisted electron-transfer quenching by phenols. Furthermore, the enantiopure hexahelical coumarins exhibit strong Cotton effects and lend themselves to a very high differentiation in the specific rotations and anisotropic dissymmetry factors. The specific rotation observed for 6-in turns out being the highest of the values reported for all hexahelicenes reported so far.So similar, yet so divergent: The inward/outward divergence replicates in the excited-state quenching phenomenon as well as chiroptical properties of regiohelical coumarins. Unprecedented regiodifferentiation is observed in the hydrogen-bond assisted electron-transfer quenching by phenols, as also in anisotropic dissymmetry factors and specific rotations.
      PubDate: 2017-09-21T08:56:07.115268-05:
      DOI: 10.1002/chem.201701787
       
  • Model Catalytic Studies of Novel Liquid Organic Hydrogen Carriers: Indole,
           Indoline and Octahydroindole on Pt(111)
    • Authors: Matthias Schwarz; Philipp Bachmann, Thais Nascimento Silva, Susanne Mohr, Marlene Scheuermeyer, Florian Späth, Udo Bauer, Fabian Düll, Johann Steinhauer, Chantal Hohner, Tibor Döpper, Heshmat Noei, Andreas Stierle, Christian Papp, H.-P. Steinrück, Peter Wasserscheid, Andreas Görling, Jörg Libuda
      Pages: 14806 - 14818
      Abstract: Indole derivatives were recently proposed as potential liquid organic hydrogen carriers (LOHC) for storage of renewable energies. In this work, we have investigated the adsorption, dehydrogenation and degradation mechanisms in the indole/indoline/octahydroindole system on Pt(111). We have combined infrared reflection absorption spectroscopy (IRAS), X-ray photoelectron spectroscopy (XPS) and DFT calculations. Indole multilayers show a crystallization transition at 200 K, in which the molecules adopt a strongly tilted orientation, before the multilayer desorbs at 220 K. For indoline, a less pronounced restructuring transition occurs at 150 K and multilayer desorption is observed at 200 K. Octahydroindole multilayers desorb already at 185 K, without any indication for restructuring. Adsorbed monolayers of all three compounds are stable up to room temperature and undergo deprotonation at the NH bond above 300 K. For indoline, the reaction is followed by partial dehydrogenation at the 5-membered ring, leading to the formation of a flat-lying di-σ-indolide in the temperature range from 330–390 K. Noteworthy, the same surface intermediate is formed from indole. In contrast, the reaction of octahydroindole with Pt(111) leads to the formation of a different intermediate, which originates from partial dehydrogenation of the 6-membered ring. Above 390 K, all three compounds again form the same strongly dehydrogenated and partially decomposed surface species.Carrying hydrogen: Following a surface science approach, we explore the reaction mechanisms of indole, indoline, and octahydroindole, a potential LOHC system. Combining surface infrared spectroscopy, synchrotron-based photoelectron spectroscopy, and density functional theory, we identify surface intermediates on Pt(111) and decomposition pathways that may lead to degradation.
      PubDate: 2017-09-26T09:44:47.435842-05:
      DOI: 10.1002/chem.201702333
       
  • β-Acrolein-Substituted Corroles: A Route to the Preparation of
           
    • Authors: Andrea Savoldelli; Gabriele Magna, Corrado Di Natale, Alexandro Catini, Sara Nardis, Frank R. Fronczek, Kevin M. Smith, Roberto Paolesse
      Pages: 14819 - 14826
      Abstract: An efficient β-functionalization of [5,10,15-tris-(4-methylphenyl)corrolato]cobalt derivatives through a Vilsmeier-type reaction allows the introduction of an acrolein substituent, which is subsequently copolymerized with pure acrolein. The obtained hybrid microspheres are exploited as nanogravimetric chemical sensors. The sensing properties of the developed sensors are tested through exposure to different volatile organic compounds chosen as model analytes. The results show improved sensor sensitivity of the resulting devices for all the tested analytes with respect to sensors functionalized with either corrole or polyacrolein. The enhanced properties are attributed to the accurate and tunable merging of the properties of both exploited materials.Unity is strength: Grafting of a functionalized Co corrole complex on polyacrolein microspheres affords a composite material, which shows improved properties upon application as a sensing material for the development of quartz microbalance sensors (see figure).
      PubDate: 2017-09-21T08:55:55.481517-05:
      DOI: 10.1002/chem.201702380
       
  • The Design of a New Cobalt Sulfide Nanoparticle Implanted Porous Organic
           Polymer Nanohybrid as a Smart and Durable Water-Splitting
           Photoelectrocatalyst
    • Authors: Subhash Chandra Shit; Santimoy Khilari, Indranil Mondal, Debabrata Pradhan, John Mondal
      Pages: 14827 - 14838
      Abstract: Development of an inexpensive, efficient and robust nanohybrid catalyst as a substitute for platinum in photoelectrocatalytic hydrogen production has been considered intriguing and challenging. In this study, the design and sequential synthesis of a novel cobalt sulfide nanoparticle grafted Porous Organic Polymer nanohybrid (CoSx@POP) is reported and used as an active and durable water-splitting photoelectrocatalyst in the hydrogen evolution reaction (HER). The specific textural and relevant chemical properties of as-synthesised nanohybrid materials (Co3O4@POP &CoSx@POP) were investigated by means of XRD, XPS, FTIR, 13C CP MAS NMR, spectroscopy, HR-TEM, HAADF-STEM with the corresponding elemental mapping, FE-SEM and nitrogen physisorption studies. CoSx@POP has been evaluated as a superior photoelectrocatalyst in HER, achieving a current density of 6.43 mA cm−2 at 0 V versus the reversible hydrogen electrode (RHE) in a 0.5 m Na2SO4 electrolyte which outperforms its Co3O4@POP analogue. It was found that the nanohybrid CoSx@POP catalyst exhibited a substantially enhanced catalytic performance of 1.07 μmol min−1cm−2, which is considered to be ca. 10 and 1.94 times higher than that of pristine POP and CoSx, respectively. Remarkable photoelectrocatalytic activity of CoSx@POP compared to Co3O4@POP toward H2 evolution could be attributed to intrinsic synergistic effect of CoSx and POP, leading to the formation of a unique CoSx@POP nanoarchitecture with high porosity, which permits easy diffusion of electrolyte and efficient electron transfer from POP to CoSx during hydrogen generation with a tunable bandgap, that straddles between the reduction and oxidation potential of water.Water splitting photocatalyst: A noble metal free cobalt sulfide nanoparticle grafted Porous Organic Polymer nanohybrid (CoSx@POP) has been developed as an active and durable water-splitting photoelectrocatalyst for the hydrogen evolution reaction.
      PubDate: 2017-09-26T09:44:34.072836-05:
      DOI: 10.1002/chem.201702561
       
  • In-Situ Fabrication of MOF-Derived Co−Co Layered Double Hydroxide Hollow
           Nanocages/Graphene Composite: A Novel Electrode Material with Superior
           Electrochemical Performance
    • Authors: Xue Bai; Jingyuan Liu, Qi Liu, Rongrong Chen, Xiaoyan Jing, Bin Li, Jun Wang
      Pages: 14839 - 14847
      Abstract: Rational design of a transition metal layered double hydroxide (LDH) and graphene composite is vitally important for designing high-performance supercapacitor electrodes. Although various methods are performed, the realization of high-performance is still impeded by the agglomeration of graphene and layered double hydroxide. Here, metal–organic framework derived cobalt–cobalt layered double hydroxide (Co−Co LDH) hollow nanocages, uniformly deposited on graphene nanosheets, are fabricated through facile in situ co-deposition and thermal ion-exchange reaction. Electrochemical investigation reveals that Co−Co LDH/15 mg graphene is rather outstanding, which delivers high specific capacitance of 1205 F g−1, excellent rate capability (60.3 % capacitance retention is obtained after the current density increased 6.67 times), and cycling stability. The excellent performance of electrode is also confirmed by assembling an asymmetric supercapacitor, which delivers high energy density of 49.5 Wh kg−1 as well as the maximum power density of 7000 W kg−1. The Co−Co LDH/graphene composite proves a promising concept for constructing hierarchical structure materials in the future.Layer cake: A metal–organic framework derived Co−Co LDH/graphene composite was successfully synthesized through facile co-precipitation method followed by chemical etching. The special hollow nanocages structure of Co−Co LDH combined with high conductivity of graphene nanosheets endowed the material with superior electrochemical performance. Moreover, an asymmetric supercapacitor based on the composite and active carbon exhibit outstanding electrochemical properties ascribed to the co-effect of graphene and Co−Co LDH.
      PubDate: 2017-09-22T06:21:52.246448-05:
      DOI: 10.1002/chem.201702676
       
  • Rhenium-Loaded TiO2: A Highly Versatile and Chemoselective Catalyst for
           the Hydrogenation of Carboxylic Acid Derivatives and the N-Methylation of
           Amines Using H2 and CO2
    • Authors: Takashi Toyao; S. M. A. H. Siddiki, Yoshitsugu Morita, Takashi Kamachi, Abeda S. Touchy, Wataru Onodera, Kenichi Kon, Shinya Furukawa, Hiroko Ariga, Kiyotaka Asakura, Kazunari Yoshizawa, Ken-ichi Shimizu
      Pages: 14848 - 14859
      Abstract: Herein, we report a heterogeneous TiO2-supported Re catalyst (Re/TiO2) that promotes various selective hydrogenation reactions, which includes the hydrogenation of esters to alcohols, the hydrogenation of amides to amines, and the N-methylation of amines, by using H2 and CO2. Initially, Re/TiO2 was evaluated in the context of the selective hydrogenation of 3-phenylpropionic acid methyl ester to afford 3-phenylpropanol (pH2=5 MPa, T=180 °C), which revealed a superior performance over other catalysts that we tested in this study. In contrast to other typical heterogeneous catalysts, hydrogenation reactions with Re/TiO2 did not produce dearomatized byproducts. DFT studies suggested that the high selectivity for the formation of alcohols in favor of the hydrogenation of aromatic rings is ascribed to the higher affinity of Re towards the COOCH3 group than to the benzene ring. Moreover, Re/TiO2 showed a wide substrate scope for the hydrogenation reaction (19 examples). Subsequently, this Re/TiO2 catalyst was applied to the hydrogenation of amides, the N-methylation of amines, and the N-alkylation of amines with carboxylic acids or esters.Chemoselective hydrogenation catalyst: A heterogeneous TiO2-supported Re catalyst (Re/TiO2) promotes the selective hydrogenation of esters to alcohols and amides to amines, as well as the N-methylation of amines, by using H2 and CO2 (see picture). Re/TiO2 shows a wide substrate scope for each reaction.
      PubDate: 2017-09-26T09:44:22.261554-05:
      DOI: 10.1002/chem.201702801
       
  • Buildup of Redox-Responsive Hybrid from Polyoxometalate and Redox-Active
           Conducting Oligomer: Its Self-Assemblies with Controllable Morphologies
    • Authors: Shan She; Zehuan Huang, Panchao Yin, Aruuhan Bayaguud, Hongli Jia, Yichao Huang, Yen Wei, Yongge Wei
      Pages: 14860 - 14865
      Abstract: A redox-responsive hybrid of polyoxometalate and conducting oligomer including its self-assemblies with controllable morphologies are reported. To this end, a hybrid molecule, containing a Lindqvist hexamolybdate as the polar head group and N,N′-bis(4′-amino-2,6-dimethylphenyl)-1,4-quinonediimine as the redox-responsive and aggregating group, is prepared. This hybrid exhibits redox-responsive behavior with controllable assembling morphological transition from spherical vesicles to short cylindrical vesicles. Besides, the hybrid-based self-assemblies are transferred to the surface, thus the surface wettability can be well-tuned owing to the morphological transitions of the self-assemblies. By marrying conducting materials with polyoxometalate chemistry, this research opens a new horizon of polyoxometalate-based self-assembled systems with potential applications in functional materials.Redox-responsive POM hybrid: Tri(aniline) was covalently introduced to the Lindqvist hexamolybdate, which exhibits interesting self-assembling behaviors with redox-responsive morphological transitions. Additionally, such redox-controlled morphological transitions can be further employed in tuning the surface wettability.
      PubDate: 2017-09-27T09:55:19.406068-05:
      DOI: 10.1002/chem.201702857
       
  • Transition Metal Catalyzed, Regioselective B(4)-Halogenation and
           B(4,5)-Diiodination of Cage B−H Bonds in o-Carboranes
    • Authors: Hairong Lyu; Yangjian Quan, Zuowei Xie
      Pages: 14866 - 14871
      Abstract: Transition metal catalyzed, regioselective carborane-cage B(4)−H iodination, bromination, and chlorination as well as B(4,5)−H diiodination were achieved by using NXS (X=I, Br), FeCl3, or IOAc as the halogenating agent, respectively. A series of previously inaccessible B(4)-halogenated o-carboranes were synthesized in a simple one-pot process, and proved to be valuable synthons for the functionalization of carboranes. Mono- and di-selectivity can be controlled by in situ removal of the carboxy directing group. The resultant 4-I-o-C2B10H11 can serve as a versatile feedstock for the construction of cage B−C(sp2), B−C(sp), B−O, and B−N bonds.Access granted: Transition metal catalyzed, regioselective cage B(4)−H iodination, bromination, and chlorination as well as B(4,5)−H diiodination were achieved to grant access to a series of previously inaccessible B(4)-halogenated o-carboranes in a simple one-pot process (see scheme). Mono- and di-selectivity can be controlled by in situ removal of the carboxyl directing group.
      PubDate: 2017-09-21T08:56:15.620249-05:
      DOI: 10.1002/chem.201703006
       
  • Photochemical and Electrochemical Triggered Bis(hydrazone) Switch
    • Authors: Mónica A. Gordillo; Mónica Soto-Monsalve, Christian C. Carmona-Vargas, Gustavo Gutiérrez, Richard F. D'vries, Jean-Marie Lehn, Manuel N. Chaur
      Pages: 14872 - 14882
      Abstract: Herein, we report the synthesis of a double hydrazone capable of undergoing photochemical E/Z isomerization through the imine double bonds. The bis(hydrazone) 1-E,E can be considered as a “two-arm” system in which the controlled movement of each arm is obtained by photo-modulation, making possible the appearance of two isolable metastable isomeric states 1-E,Z and 1-Z,Z. Such states are characterized by very specific structural, optical, and electrochemical properties. The latter allows the reversible return from either 1-E,Z or 1-Z,Z to the 1-E,E state. Our results are of great importance in the further development of molecular machines and photochemically controlled reactions by introducing for the first time double hydrazones as tunable photochemical switches.En este trabajo presentamos la síntesis de una doble hidrazona capaz de experimentar isomerización fotoquímica E/Z a través de los dobles enlaces imina. La bis(hidrazona) 1-E,E puede ser considerada como un sistema de “dos brazos” en el cual el movimiento controlado de cada brazo es obtenido por foto-modulación, siendo posible la aparición de dos estados isoméricos metaestables 1-E,Z y 1-Z,Z. Los 3 isómeros están caracterizados por sus propiedades estructurales, ópticas y electroquímicas. El estudio de estas últimas, muestra el retorno de manera reversible de los estados 1-E,Z o 1-Z,Z al estado 1-E,E. Nuestros resultados son de gran importancia para el desarrollo de máquinas moleculares y reacciones controladas fotoquímicamente, presentando por primera vez hidrazonas dobles como interruptores fotoquímicos manipulables.Switching sides: The synthesis of a double hydrazone capable of undergoing photochemical E/Z isomerization through the imine double bonds is reported. The bis(hydrazone) 1-E,E can be considered as a “two-arm” system in which the controlled movement of each arm is obtained by photo-modulation, making possible the appearance of two isolable metastable isomeric states 1-E,Z and 1-Z,Z (see scheme).
      PubDate: 2017-09-27T05:06:54.346427-05:
      DOI: 10.1002/chem.201703065
       
  • Autonomous and Continuous Stimuli-Responsive Polymer Surface for
           Antibacterial Application through Enzymatic Self-Propagating Reactions
    • Authors: Chao Ding; Zhengqing Yan, Jinsong Ren, Xiaogang Qu
      Pages: 14883 - 14888
      Abstract: Stimuli-responsive polymer materials inspired by biological materials have invoked increasing research interest; however, they still suffer from limitations such as finite amplified responses and poor sensitivity of the unstimulated parts. Herein, a new strategy for creating H+-responsive polymer surfaces that are capable of transforming specific local fleeting stimuli into global macroscopic changes is described. The introduction of self-propagating reactions into the polymer-surface systems endows them with excellent stimuli-amplifying properties and response of the unstimulated parts. On the basis of this design, a polymer and enzymatic reaction were employed to enable a specific response to a stimulus and then lead to macroscopic changes of the surface. It is further shown that the prepared H+-responsive polymer surfaces can be employed for antibacterial application. This work provides a good example of achieving autonomously reconfigurable materials that respond to local fleeting stimuli.Please respond! pH-Responsive polymer surfaces that are capable of transforming specific local fleeting stimuli into global macroscopic property changes were designed by the introduction of self-propagating reactions into polymer-surface systems (see figure). The H+-responsive polymer surfaces can be employed for antibacterial applications, and this design strategy offers methods for achieving autonomously reconfigurable materials.
      PubDate: 2017-09-18T08:45:27.050045-05:
      DOI: 10.1002/chem.201703067
       
  • Rhodium-Catalyzed [2+2+2] Cycloaddition Reactions of Linear
           Allene–Ene–Ynes to afford Fused Tricyclic Scaffolds: Insights into the
           Mechanism
    • Authors: Daniel Cassú; Teodor Parella, Miquel Solà, Anna Pla-Quintana, Anna Roglans
      Pages: 14889 - 14899
      Abstract: Allene-(E)-ene-yne N-tosyl-tethered substrates 3 a–3 h were efficiently prepared and their rhodium-catalyzed [2+2+2] cycloaddition reactions were evaluated. The cycloadditions are chemoselective as only the proximal double bond of the allene reacted to afford exocyclic double bonds in the fused-tricyclic scaffolds. The stereoselectivity depended on the catalytic system used. Reactivity between allene, alkene, and alkyne was studied for the first time by density functional theory calculations. This mechanistic study determines the order in which the unsaturated groups take part in the catalytic cycle.S′ha preparat satisfactòriament una sèrie de substrats 3 a–3 h de cadena oberta contenint un al⋅lè, un doble enllaç i un alquí i s'ha avaluat la seva reacció de cicloaddició [2+2+2] catalitzada per rodi. La cicloaddició és quimioselectiva degut a què només el doble enllaç intern de l′al⋅lè reacciona per donar un sistema tricíclic fusionat amb un doble enllaç exocíclic. L′estereoselectivitat del procés depèn del sistema catalític emprat. La diferent reactivitat entre l′al⋅lè, l′alquè i l′alquí s'ha estudiat per primer cop mitjançant càlculs teòrics basats en la teoria del funcional de la densitat. Aquest estudi mecanístic permet determinar l′ordre en què les insaturacions participen en el cicle catalític.Fused tricyclic scaffolds: Three carbon-based unsaturated moieties (allene–alkyne–alkene) have been jointly involved in [2+2+2] cycloaddition reactions under rhodium catalysis. The ligands on the catalyst affect the diastereoselectivity of the process. DFT calculations rationalize these selectivity issues and the order in which the different unsaturated groups take part in the catalytic cycle.
      PubDate: 2017-09-27T05:07:06.226272-05:
      DOI: 10.1002/chem.201703194
       
  • Copper-Containing Nitrite Reductase Employing Proton-Coupled
           Spin-Exchanged Electron-Transfer and Multiproton Synchronized Transfer to
           Reduce Nitrite
    • Authors: Xin Qin; Li Deng, Caihong Hu, Li Li, Xiaohua Chen
      Pages: 14900 - 14910
      Abstract: The possible catalytic mechanism of the reduction of nitrite by copper-containing nitrite reductases (CuNiRs) is examined by using the M06 function according to two copper models, which include type-one copper (T1Cu) and type-two copper (T2Cu) sites. Examinations confirm that the protonation of two residues, His255 and Asp98, near the T2Cu site, can modulate the redox states of T1Cu and T2Cu, but cannot directly cause electron transfer from T1Cu to T2Cu. The electron hole remains at the T2Cu site when only one residue, His255 or Asp98, is protonated. However, the hole resides at the T1Cu site when both His255 and Asp98 are protonated. Then, the first protonation of nitrite takes place through indirect proton transfer from protonated His255 through the bridging H2O and Asp98 with three protons moving together, which cannot cause the cleavage of the HO−NO bond. Subsequently, the substrate is required to obtain another proton from reprotonated His255 through the bridging H2O. The reprotonation of nitrite induces the generation of nitric oxide (NO) and H2O at the T2Cu site through a special double-proton-coupled spin-exchanged electron-transfer mechanism with indirect proton transfer from His255 to the substrate, a beta-electron of T2CuI shift to the NO cation, and the remaining alpha-electron changing spin direction at the same time. These results may provide useful information to better understand detailed proton-/electron-transfer reactions for the catalytic processes of CuNiR.Overcoming transfer barriers: New insights into the catalytic mechanism of copper-containing nitrite reductases are reported. The protonation of both His255 and Asp98 is sufficient for electron transfer (ET) from T1Cu to T2Cu, but not a direct cause. The reaction mechanism, including triple-proton synchronized transfer (tPST) with indirect proton transfer (PT) and double-proton-coupled spin-exchanged ET (dPCseET) with indirect PT, has been investigated by DFT calculations (see scheme).
      PubDate: 2017-09-25T03:13:27.136692-05:
      DOI: 10.1002/chem.201703221
       
  • A Highly Sensitive Bimodal Detection of Amine Vapours Based on Aggregation
           Induced Emission of 1,2-Dihydroquinoxaline Derivatives
    • Authors: Parvej Alam; Nelson L. C. Leung, Huifang Su, Zijie Qiu, Ryan T. K. Kwok, Jacky W. Y. Lam, Ben Zhong Tang
      Pages: 14911 - 14917
      Abstract: The detection of food spoilage is a major concern in food safety as large amounts of food are transported globally. Direct analysis of food samples is often time-consuming and requires expensive analytical instrumentation. A much simpler and more cost-effective method for monitoring food fermentation is to detect biogenic amines generated as a by-product during food decomposition. In this work, a series of 1,2-dihydroquinoxaline derivatives (DQs) with aggregation-induced emission (AIE) characteristics were synthesised and their protonated forms, that is, H+DQs, can be utilised for the sensitive detection of biogenic amines. For example, upon exposure to amine vapours, deprotonation occurs that converts the red-coloured, non-emissive H+DQ2 back to its yellow-coloured, fluorescent parent form. The bimodal absorption and emission changes endow the system with high sensitivity, capable of detecting ammonia vapour at a concentration of as low as 690 ppb. Taking advantage of this, H+DQ2 was successfully applied for the detection of food spoilage and was established as a robust and cost effective technique to monitor food safety.Detecting biogenic amines: A new family of AIEgens provide a platform for simple, sensitive, bimodal detection of biogenic amine vapours produced by food fermentation. The colourimetric change allows for easy naked eye visualisation, while fluorescence turn-on provides enhanced sensitivity for earlier indication, with a detection limit of 690 ppb for ammonia.
      PubDate: 2017-09-25T05:25:29.112354-05:
      DOI: 10.1002/chem.201703253
       
  • (CF3)3Au as a Highly Acidic Organogold(III) Fragment
    • Authors: Alberto Pérez-Bitrián; Miguel Baya, José M. Casas, Larry R. Falvello, Antonio Martín, Babil Menjón
      Pages: 14918 - 14930
      Abstract: The Lewis acidity of perfluorinated trimethylgold (CF3)3Au was assessed by theoretical and experimental methods. It was found that the (CF3)3Au unit is much more acidic than its nonfluorinated analogue (CH3)3Au, and probably sets the upper limit of the acidity scale for neutral organogold(III) species R3Au. The significant acidity increase on fluorination is in line with the CF3 group being more electron-withdrawing than CH3. The solvate (CF3)3Au⋅OEt2 (1) is presented as a convenient synthon of the unsaturated, 14-electron species (CF3)3Au. Thus, the weakly coordinated ether molecule in 1 is readily replaced by a variety of neutral ligands (L) to afford a wide range of (CF3)3Au⋅L compounds, which were isolated and characterized. Most of these mononuclear compounds exhibit marked thermal stability. This enhanced stabilization can be rationalized in terms of substantially stronger [Au]−L interactions with the (CF3)3Au unit. An affinity scale of this single-site, highly acidic organogold(III) fragment was calculated by DFT methods and experimentally mapped for various neutral monodentate ligands. The high-energy profile calculated for the fluorotropic [Au]−CF3⇌F−[Au]CF2 process makes this potential decomposition path unfavorable and adds to the general stabilization of the fragment.Gold standard: Formal perfluorination of trimethylgold (CH3)3Au causes a substantial increase in the Lewis acidity of the Au center in (CF3)3Au. The single-site perfluorinated (CF3)3Au moiety arguably has the highest Lewis acidity of any conceivable R3Au organogold species.
      PubDate: 2017-09-26T09:43:46.760342-05:
      DOI: 10.1002/chem.201703352
       
  • Anti-Electrostatic CH–Ion Bonding in Decorated Graphanes
    • Authors: Martin Novák; Radek Marek, Cina Foroutan-Nejad
      Pages: 14931 - 14936
      Abstract: State-of-the-art computations combined with Ziegler–Rauk energy decomposition analyses are employed to introduce a new class of anti-electrostatic ion–σ bonds with considerable stability and a substantial contribution from charge transfer and dispersion between ions and finite-size functionalized graphane flakes, G-XYs. G-XYs have diverse electric multipolar moments that are comparable with those of newly synthesized all-cis-hexa-halocyclohexanes. The strong, long-range electrostatic and Pauli repulsions between some G-XYs and certain ions induce a gas-phase energy barrier to the physisorption of ions on the surface of G-XYs. However, the repulsive interactions can be overbalanced by the strong orbital interactions operating in the formation of ion–σ complexes at short range, leading to covalent-type intermolecular bonds as strong as −34 kcal mol−1.Ion–σ interactions: A new class of anti-electrostatic ion–σ bonds between ions and functionalized graphane flakes, G-XYs, is introduced. The strong, long-range electrostatic and Pauli repulsions can be overbalanced by strong orbital interactions (see figure), leading to ion–σ complexes with covalent-type intermolecular bonds as strong as −34 kcal mol−1.
      PubDate: 2017-09-14T04:18:55.450059-05:
      DOI: 10.1002/chem.201703459
       
  • Conjugated Gold–Porphyrin Monolayers Assembled on Inorganic Surfaces
    • Authors: Annalinda Contino; Giuseppe Maccarrone, Maria E. Fragalà, Luca Spitaleri, Antonino Gulino
      Pages: 14937 - 14943
      Abstract: Gold nanoparticles show important properties owing to their electronic structures. A limitation of some gold nanoparticles is that they either show surface plasmons or luminescence. The increase in size of the gold nanoparticles, and the appearance of the surface plasmons may result in the disappearance of luminescence. The aim of our study is the nanoscale assembly of Au nanoparticles on a monolayer of porphyrin molecules anchored to functionalized inorganic surfaces. This functional architecture not only exhibits a strong surface plasmon due to the gold nanoparticles, but also a strong luminescence signal from the porphyrin molecules. Finally we observed a long-range order in the Au nanoparticles conjugated to the porphyrin monolayer.Gold! gold: A luminescent and plasmonic nanoscale assembly of ordered gold nanoparticles on a monolayer of porphyrin molecules has been obtained.
      PubDate: 2017-09-25T11:10:32.886335-05:
      DOI: 10.1002/chem.201703523
       
  • Lanthanide Fluorobenzoates as Bio-Probes: a Quest for the Optimal Ligand
           Fluorination Degree
    • Authors: Alena S. Kalyakina; Valentina V. Utochnikova, Ivan S. Bushmarinov, Irina M. Le-Deygen, Daniel Volz, Patrick Weis, Ute Schepers, Natalia P. Kuzmina, Stefan Bräse
      Pages: 14944 - 14953
      Abstract: The thorough study of fluorinated benzoates of lanthanides (Eu, Tb, Nd, Er, Yb, Gd, La, Lu) is reported. Their composition in single crystal and powder state revealed two predominant structural motifs. An in-depth luminescence study has been performed on the reported fluorobenzoates, showing, that terbium and europium complexes in solid state possess high luminescence intensity with the quantum yield of up to 69 %. High solubility in most organic solvents, as well as in water, combined with the high luminescence intensity in water solution and non-toxicity allowed the testing of europium complexes as bioprobes in cellulo. Among all tested fluorobenzoates, europium 2-fluorobenzoate dihydrate combined the best luminescent properties, thermodynamic stability, aqueous solubility, and non-toxicity, and was shown to be a viable bio-marker.Probe: An in-depth study on the luminescence of fluorinated benzoates of lanthanides was performed, optimizing the fluorination degree of the complexes. This leads to a europium 2-fluorobenzoate dehydrate showing excellent properties, as a viable bio-marker.
      PubDate: 2017-09-22T03:27:18.346209-05:
      DOI: 10.1002/chem.201703543
       
  • Mechanism of the Catalytic Carboxylation of Alkylboronates with CO2 Using
           Ni−NHC Complexes: A DFT Study
    • Authors: Maicon Delarmelina; Enrico Marelli, José Walkimar de M. Carneiro, Steven P. Nolan, Michael Bühl
      Pages: 14954 - 14961
      Abstract: A new mechanism is proposed for the Ni-catalyzed carboxylation of organoboronates with CO2. DFT investigations at the PBE0-D3 level have shown that direct CO2 addition to the catalysts [Ni(NHC)(Allyl)Cl] (1NHC, NHC=IMe, IPr, SIPr and IPr*) is kinetically disfavored and formation of the Aresta-type intermediate is unlikely to occur. According to the mechanism proposed here, the carboxylation process starts with addition of the borate species to 1NHC, followed by transmetalation, CO2 cycloaddition and carboxylation. The rate-determining step was identified as being the transmetalation process, with computed relative free energy barriers of 34.8, 36.8, and 33.5 kcal mol−1 for 1IPr, 1SIPr and 1IPr*, respectively.CO2 Activation: Based on DFT calculations a new mechanism is proposed for the Ni-catalyzed carboxylation of organoboronates with CO2. In this mechanism, transfer of the organic moiety from boron to nickel (transmetalation) is identified as the rate-limiting step.
      PubDate: 2017-09-26T09:42:12.599477-05:
      DOI: 10.1002/chem.201703567
       
  • Thermally-Triggered Crystal Dynamics and Permanent Porosity in the First
           Heptatungstate-Metalorganic Three-Dimensional Hybrid Framework
    • Authors: Jagoba Martín-Caballero; Beñat Artetxe, Santiago Reinoso, Leire San Felices, Oscar Castillo, Garikoitz Beobide, José Luis Vilas, Juan M. Gutiérrez-Zorrilla
      Pages: 14962 - 14974
      Abstract: The hybrid compound [{Cu(cyclam)}3(W7O24)]⋅15.5 H2O (1) (cyclam=1,4,8,11-tetraaza-cyclotetradecane) was synthesized by reacting the {Cu(cyclam)}2+ complex with a tungstate source in water at pH 8. Compound 1 exhibits an unprecedented three-dimensional covalent structure built of heptatungstate clusters linked through metalorganic complexes in a POMOF-like framework that displays water-filled channels. This dynamic architecture undergoes two sequential single-crystal-to-single-crystal transformations upon thermal evacuation of water molecules to result in the partially dehydrated [{Cu(cyclam)}3(W7O24)]⋅12 H2O (2) and anhydrous [Cu(cyclam)]0.5[{Cu(cyclam)}2.5(W7O24)] (3) crystalline phases. These transitions are associated with cluster rotations and modifications in the CuII coordination geometries, which reduce the dimensionality of the original lattice to layered systems but preserving the porous nature. Phase 3 reverts to 2 upon exposure to ambient moisture, whereas the transition between 1 and 2 proved to be irreversible. The permanent microporosity of 3 was confirmed by gas sorption measurements (N2, CO2), which reveal a system of parallel channels made of wide cavities connected through narrow necks that limit the adsorption process. This observation is in good agreement with Grand Canonical Monte Carlo simulations.Framework transformation: A three-dimensional covalent open framework built of copper(II)-complexes of a macrocyclic tetraaza ligand and heptatungstate anions undergoes two sequential single-crystal-to-single-crystal transformations upon dehydration. The permanent porosity of the system has been confirmed by CO2 and N2 sorption experiments.
      PubDate: 2017-09-26T09:42:03.832841-05:
      DOI: 10.1002/chem.201703585
       
 
 
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