Chemistry - A European Journal

Cover image for Vol. 17 Issue 20

May 9, 2011

Volume 17, Issue 20

Pages 5449–5747

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Back Cover
    5. Graphical Abstract
    6. News
    7. Review
    8. Communications
    9. Full Papers
    10. Preview
    1. Cover Picture: Viability of 4,5-Dihydro-1,2,3,4-oxatriazoles Reinvestigated (Chem. Eur. J. 20/2011) (page 5449)

      Samia Firdous, Prof. Dr. Klaus Banert and Prof. Dr. Alexander A. Auer

      Version of Record online: 29 APR 2011 | DOI: 10.1002/chem.201190098

      Thumbnail image of graphical abstract

      Exothermic or endothermic? This question arises for some intramolecular 1,3-dipolar cycloaddition reactions of azides. The picture schematically illustrates the answer for alkene and aldehyde units as dipolarophiles. In their Full Paper on page 5539 ff., S. Firdous, K. Banert, and A. A. Auer used both experimentally and quantum chemical methods to investigate the possibility of generating known and supposedly known nitrogen heterocycles.

  2. Inside Cover

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Back Cover
    5. Graphical Abstract
    6. News
    7. Review
    8. Communications
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    1. Inside Cover: Signal Transducers and Enzyme Cofactors are Susceptible to Oxidation by Nanographite Impurities in Carbon Nanotube Materials (Chem. Eur. J. 20/2011) (page 5450)

      Emma J. E. Stuart and Prof. Martin Pumera

      Version of Record online: 29 APR 2011 | DOI: 10.1002/chem.201190099

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      Carbon nanotubes (CNTs) are often employed in biofuel cells, artificial photosystems and bioelectronics in order to enhance electron transfer. However, typical CNTs are highly heterogeneous materials, containing large amounts of impurities. In their Full Paper on page 5544 ff., M. Pumera, and E. J. E. Stuart demonstrate that nanographite impurities within CNTs are responsible for the “electrocatalytic” oxidation of NADH and two amino acids involved in signal transduction. In the figure the purity symbolised by Geisha is given in contrast with imperfections of CNTs.

  3. Back Cover

    1. Top of page
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    4. Back Cover
    5. Graphical Abstract
    6. News
    7. Review
    8. Communications
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    1. Back Cover: A Heteroleptic Bis(tridentate) Ruthenium(II) Complex of a Click-Derived Abnormal Carbene Pincer Ligand with Potential for Photosensitzer Application (Chem. Eur. J. 20/2011) (page 5450)

      Dipl.-Chem. Benjamin Schulze, Daniel Escudero, Dipl.-Chem. Christian Friebe, Dipl.-Chem. Ronald Siebert, Dr. Helmar Görls, Dr. Uwe Köhn, Esra Altuntas, Dipl.-Chem. Anja Baumgaertel, Dr. Martin D. Hager, Dr. Andreas Winter, Dr. Benjamin Dietzek, Prof. Dr. Jürgen Popp, Prof. Dr. Leticia González and Prof. Dr. Ulrich S. Schubert

      Version of Record online: 29 APR 2011 | DOI: 10.1002/chem.201190103

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      More than just a click 1,2,3-triazoles not only serve as linkers, they also provide access to 1,2,3-triazolylidenes that are powerful mesoionic carbene donors. In their Communication on page 5494 ff., L. González, U. S. Schubert et al. report on a heteroleptic ruthenium(II) complex of a new tridentate triazolylidene ligand. The complex features great potential for photosensitizer applications and is studied by experimental and computational methods.

  4. Graphical Abstract

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Back Cover
    5. Graphical Abstract
    6. News
    7. Review
    8. Communications
    9. Full Papers
    10. Preview
  5. News

    1. Top of page
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    5. Graphical Abstract
    6. News
    7. Review
    8. Communications
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  6. Review

    1. Top of page
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    1. Coupling Reactions

      Recent Progress in Coupling of Two Heteroarenes (pages 5466–5492)

      Dongbing Zhao, Prof. Dr. Jingsong You and Prof. Dr. Changwei Hu

      Version of Record online: 19 APR 2011 | DOI: 10.1002/chem.201003039

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      Opposites attract: The biheteroaryl structural motif is prevalent in polymers, advanced materials, molecules of medicinal interest, and natural products. In this article, four types of coupling reactions are reviewed. The general purpose of this review is to give a clear picture in heteroaryl–heteroaryl bond formation as well as its application in the synthesis of natural products, pharmaceuticals, catalyst ligands, and materials.

  7. Communications

    1. Top of page
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    4. Back Cover
    5. Graphical Abstract
    6. News
    7. Review
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    1. Coordination Chemistry

      A Heteroleptic Bis(tridentate) Ruthenium(II) Complex of a Click-Derived Abnormal Carbene Pincer Ligand with Potential for Photosensitzer Application (pages 5494–5498)

      Dipl.-Chem. Benjamin Schulze, Daniel Escudero, Dipl.-Chem. Christian Friebe, Dipl.-Chem. Ronald Siebert, Dr. Helmar Görls, Dr. Uwe Köhn, Esra Altuntas, Dipl.-Chem. Anja Baumgaertel, Dr. Martin D. Hager, Dr. Andreas Winter, Dr. Benjamin Dietzek, Prof. Dr. Jürgen Popp, Prof. Dr. Leticia González and Prof. Dr. Ulrich S. Schubert

      Version of Record online: 12 APR 2011 | DOI: 10.1002/chem.201100045

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      Long live the complex! A heteroleptic ruthenium(II) complex of a click-derived tridentate triazolylidene ligand (see graphic) and the parent terpyridine were prepared and investigated by experimental and computational methods. The new ligand enables excited-state lifetimes and room-temperature emission quantum yields that can compete with tris(bipyridine)ruthenium(II) complexes, but with the structural benefits of bis(terpyridine)ruthenium(II) complexes.

    2. Nanostructures

      Layered TiO2 Composed of Anatase Nanosheets with Exposed {001} Facets: Facile Synthesis and Enhanced Photocatalytic Activity (pages 5499–5502)

      Huan Yu, Dr. Baozhu Tian and Prof. Dr. Jinlong Zhang

      Version of Record online: 11 APR 2011 | DOI: 10.1002/chem.201003437

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      Layered TiO2composed of nanosheets with exposed {001} facets were synthesized by using in situ generated BF4 and PrO as morphology-controlling agents (see scheme). The obtained layered TiO2 with reactive {001} facets shows excellent photocatalytic activity, resulting from the synergetic effects of the layered structures and the {001} facet-dominated nanosheets.

    3. Self-Assembly

      Self-Assembly of Monodisperse Oligonucleotide–Elastin Block Copolymers into Stars and Compound Micelles (pages 5503–5506)

      Dr. Sabine Fluegel, Jasmin Buehler, Dr. Karl Fischer, Jonathan R. McDaniel, Prof. Ashutosh Chilkoti and Prof. Manfred Schmidt

      Version of Record online: 5 APR 2011 | DOI: 10.1002/chem.201100436

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      A DNA star is born: The molecular recognition of a mixture of oligonucleotide–elastinlike polypeptide (ODN–ELP) block copolymers leads to the formation of monodisperse three- and four-arm stars with DNA cores and pendant ELP arms. These hybrid block copolymers combine molecular recognition and thermal responsiveness, resulting in the temperature-triggered formation of relatively monodisperse compound micelles at temperatures above the lower critical solution temperature (see scheme).

    4. Umpolung Reactions

      A Titanium(III)-Catalyzed Redox Umpolung Reaction for the Reductive Cross-Coupling of Enones with Acrylonitriles (pages 5507–5510)

      Dr. Jan Streuff

      Version of Record online: 12 APR 2011 | DOI: 10.1002/chem.201100501

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      Titanium does the job: 1,6-Difunctionalized alkyl units, which are traditionally hard to access, have been successfully obtained through a reductive cross-coupling of activated alkenes catalyzed by TiIII. A plausible reaction mechanism that proceeds through redox umpolung of the enone is briefly discussed (see scheme, Cp=cyclopentadiene).

    5. Domino Reactions

      Synthesis of 5-Halo-4H-1,3-oxazine-6-amines by a Copper-Mediated Domino Reaction (pages 5511–5515)

      Prof. Dr. A. Stephen K. Hashmi, Dipl.-Chem. Andreas M. Schuster, Marc Zimmer and Dr. Frank Rominger

      Version of Record online: 13 APR 2011 | DOI: 10.1002/chem.201100423

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      Three become one! In one copper-mediated step, three simple components, including a propargylcarboxamide, a protected amine, and a source of chloride, assemble to give highly functionalized oxazines, which are interesting building blocks for the synthesis of other aminooxazine derivatives (see scheme; R1=range of aryl or alkyl groups, R2=alkyl, EWG=electron-withdrawing group).

    6. Catalysis

      Copper-Catalyzed C–P Coupling through Decarboxylation (pages 5516–5521)

      Jie Hu, Ning Zhao, Bin Yang, Ge Wang, Li-Na Guo, Prof. Yong-Min Liang and Shang-Dong Yang

      Version of Record online: 14 APR 2011 | DOI: 10.1002/chem.201003561

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      An acid for a phosphine: A versatile protocol for preparation of various di(phenyl)phosphoryl oxides was developed by copper-catalyzed decarboxylative coupling of alkenyl, alkynyl carboxylic acids, and N-benzylproline, respectively, with R2P(O)H (see scheme). All classes of products are important precursors for preparation of biologically active molecules and various phosphorus ligands. This finding represents the first example of copper-catalyzed decarboxylative coupling to construct C[BOND]P bonds.

      Corrected by:

      Corrigendum: Corrigendum: Copper-Catalyzed C[BOND]P Coupling through Decarboxylation

      Vol. 17, Issue 23, 6289, Version of Record online: 20 MAY 2011

    7. Photoluminescence

      UV-Induced Rhodamine B Aggregation into Nanoparticles Exhibiting Reversible Changes of Yellow- and White-Light Photoluminescent Emissions (pages 5522–5525)

      Chih-Yuan Hsu and Prof. Ying-Ling Liu

      Version of Record online: 5 APR 2011 | DOI: 10.1002/chem.201003692

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      Light switches: UV irradiation induces Rhodamine B (RhB) aggregation into nanoparticles and changes RhB photoluminescent emissions from yellow to white light (see graphic). The UV-induced changes are reversible. A novel approach to generate organic fluorescent nanoparticles and to prepare white-light-emitting fluorescent materials is demonstrated.

  8. Full Papers

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Back Cover
    5. Graphical Abstract
    6. News
    7. Review
    8. Communications
    9. Full Papers
    10. Preview
    1. Self-Assembly

      Virus-Sized DNA Nanoparticles for Gene Delivery Based on Micelles of Cationic Calixarenes (pages 5526–5538)

      Dr. Roman V. Rodik, Dr. Andrey S. Klymchenko, Dr. Namrata Jain, Dr. Stanislav I. Miroshnichenko, Dr. Ludovic Richert, Dr. Vitaly I. Kalchenko and Prof. Dr. Yves Mély

      Version of Record online: 18 APR 2011 | DOI: 10.1002/chem.201100154

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      Calixarene/DNA nanoparticles: Cone-shaped cationic amphiphilic calixarenes synthesized in this work form micelles of 6 nm diameter that can compact DNA into small nanoparticles of about 50 nm diameter (see figure; scale bar=1 μm). These virus-sized particles showed promising transfection properties and low cytotoxicity in cell culture and therefore can be of interest for the development of new gene delivery vectors.

    2. Azides

      Viability of 4,5-Dihydro-1,2,3,4-oxatriazoles Reinvestigated (pages 5539–5543)

      Samia Firdous, Prof. Dr. Klaus Banert and Prof. Dr. Alexander A. Auer

      Version of Record online: 19 APR 2011 | DOI: 10.1002/chem.201100231

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      Chemistry in question: Upon treatment with sodium azide, bromo- or tosyloxy-substituted butanals lead exclusively to the corresponding azides but not to heterocycles (see scheme). This result is supported by experimental work and quantum chemical calculations. The latter suggest that 4,5-dihydro-1,2,3,4-oxatriazoles generally do not belong to the class of stable compounds.

    3. Carbon Nanotubes

      Signal Transducers and Enzyme Cofactors are Susceptible to Oxidation by Nanographite Impurities in Carbon Nanotube Materials (pages 5544–5548)

      Emma J. E. Stuart and Prof. Martin Pumera

      Version of Record online: 13 APR 2011 | DOI: 10.1002/chem.201003639

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      (Im)pure and simple! The influence of nanographite impurities contained within CNTs upon the redox properties of signal transducers and enzyme cofactors that are vital for the functioning of biofuel cells, artificial leaves and bioelectronics as well as for the survival of living organisms are reported. It has been found that nanographite impurities within CNTs are responsible for the “electrocatalytic” oxidation of NADH and two amino acids involved in signal transduction.

    4. Dendrimers

      Fluorenyl Hexa-peri-hexabenzocoronene-Dendritic Oligothiophene Hybrid Materials: Synthesis, Photophysical Properties, Self-Association Behaviour and Device Performance (pages 5549–5560)

      Dr. Wallace W. H. Wong, Dr. Chang-Qi Ma, Dr. Wojciech Pisula, Dr. Alexey Mavrinskiy, Dr. Xinliang Feng, Dr. Helga Seyler, Dr. David J. Jones, Prof. Dr. Klaus Müllen, Prof. Dr. Peter Bäuerle and Prof. Andrew B. Holmes

      Version of Record online: 12 APR 2011 | DOI: 10.1002/chem.201100211

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      Solar cells: Bisfunctionalised hexa-peri-hexabenzocoronenes with dendritic oligothiophene arms (see scheme) were synthesised, characterised and examined as electron-donor materials for organic solar cells.

    5. Nonlinear Optics

      Electron-Rich Iron/Ruthenium Arylalkynyl Complexes for Third-Order Nonlinear Optics: Redox-Switching between Three States (pages 5561–5577)

      Dr. Nicolas Gauthier, Dr. Gilles Argouarch, Dr. Frédéric Paul, Dr. Loic Toupet, Abdelkader Ladjarafi, Dr. Karine Costuas, Dr. Jean-François Halet, Prof. Marek Samoc, Dr. Marie P. Cifuentes, T. Christopher Corkery and Prof. Mark G. Humphrey

      Version of Record online: 14 APR 2011 | DOI: 10.1002/chem.201003427

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      Ru/Fe redox switchability: The insertion of Fe/Ru heterobinuclear organometallic fragments into carbon-rich molecular scaffolds imparts redox switchability of the third-order nonlinear optical (NLO) properties between three states (see picture). The synthesis of new heteropolynuclear complexes containing Fe/Ru units are reported along with their linear and cubic NLO properties in their various redox states. These properties are discussed in connection with DFT calculations performed on the electronic structures of these redox isomers.

    6. Supramolecular Chemistry

      Anion-Templated Assembly of Half-Sandwich Rhodium-Based Multinuclear Metallamacrocycles (pages 5578–5587)

      Dr. Guo-Liang Wang, Dr. Yue-Jian Lin and Prof. Guo-Xin Jin

      Version of Record online: 6 APR 2011 | DOI: 10.1002/chem.201003167

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      Running rings around anions: A series of half-sandwich rhodium-based metallamacrocycles with tetra- and hexanuclearities (see scheme) have been assembled in the presence of the corresponding counteranions. When the counteranion was the tetrahedral BF4 ion, tetranuclear metallamacrocycle 1 d was formed. However, the larger OTf, PF6, and SbF6 counterions favored the formation of hexanuclear metallamacrocycles 1 ac.

    7. Metal–Organic Frameworks

      Spin Canting and Metamagnetism in the First Hybrid Cobalt–Hypoxanthine Open Framework with umr Topology (pages 5588–5594)

      Xu-Hui Zhang, Zheng-Ming Hao and Prof. Dr. Xian-Ming Zhang

      Version of Record online: 8 APR 2011 | DOI: 10.1002/chem.201003199

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      A cobalt–nucleobase microporous framework has been constructed by using hypoxanthine as bridging ligands and Co3(OH)4 chains as rod-shaped secondary building units (SBUs, see figure). This microporous framework shows spin canting and metamagnetism.

    8. Photocatalysis

      Catalytic Photooxidation of Alcohols by an Unsymmetrical Tetra(pyridyl)pyrazine-Bridged Dinuclear Ru Complex (pages 5595–5604)

      Dr. Weizhong Chen, Dr. Francisca N. Rein, Dr. Brian L. Scott and Dr. Reginaldo C. Rocha

      Version of Record online: 30 MAR 2011 | DOI: 10.1002/chem.201002168

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      Driven by sunshine: A tppz-bridged Ru complex was prepared, structurally and electronically characterized, and its proton-coupled multi-electron photooxidation reactivity was demonstrated through the photocatalytic dehydrogenation of aliphatic and benzylic alcohols. Under simulated solar irradiation, the photoactivated catalyst (in water, at ambient conditions) can perform the visible-light-driven conversion of the alcohols into their aldehydes or ketones with very high selectivity and several tens of turnover cycles per day.

    9. Macrocycles

      Anion-Free Bambus[6]uril and Its Supramolecular Properties (pages 5605–5612)

      Jan Svec, Dr. Michal Dusek, Karla Fejfarova, Peter Stacko, Prof. Dr. Petr Klán, Prof. Dr. Angel E. Kaifer, Wei Li, Edita Hudeckova and Prof. Dr. Vladimir Sindelar

      Version of Record online: 11 APR 2011 | DOI: 10.1002/chem.201003683

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      A free choice: Anion-free bambus[6]uril (BU6) is prepared by the oxidation of iodide anion, which is bound inside the macrocycle (see picture). BU6 acts as a ditopic receptor and is able to bind halide ions in both organic solvents and aqueous media, while preserving its high affinity and selectivity.

    10. Cyclization

      Radical Cyclization of α-Bromo Aluminum Acetals onto Alkenes and Alkynes (Radic[Al] Process): A Simple Access to γ-Lactols and 4-Methylene-γ-Lactols (pages 5613–5627)

      Anne Boussonnière, Romain Bénéteau, Nicolas Zimmermann, Prof. Dr. Jacques Lebreton and Dr. Fabrice Dénès

      Version of Record online: 6 APR 2011 | DOI: 10.1002/chem.201100049

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      A ‘radic[Al]’ process: An efficient preparation of γ-lactols and methylene-γ-lactols is described. Highly acid-sensitive lactols are prepared in a concise manner by using a radical cyclization of aluminum acetals. Functionalization of the resulting γ-lactols and methylene-γ-lactols can be achieved following isolation, leading to synthetically useful building blocks (see scheme).

    11. Oligothiophenes

      Thiolate Chemistry: A Powerful and Versatile Synthetic Tool for Immobilization/Functionalization of Oligothiophenes on a Gold Surface (pages 5628–5640)

      Dr. Truong Khoa Tran, Dr. Quentin Bricaud, Dr. Maïténa Oçafrain, Dr. Philippe Blanchard, Dr. Jean Roncali, Dr. Stéphane Lenfant, Dr. Sylvie Godey, Dr. Dominique Vuillaume and Dr. David Rondeau

      Version of Record online: 13 APR 2011 | DOI: 10.1002/chem.201003687

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      A functional fixation: A versatile synthetic approach based on the use of differently protected thiolate groups has been developed for the synthesis of highly functionalized oligothiophenes and for their double fixation on gold surfaces, either by direct immobilization or by post-functionalization of a pre-immobilized monolayer (see figure).

    12. Natural Products

      The First Total Synthesis of Ganglioside GalNAc-GD1a, a Target Molecule for Autoantibodies in Guillain–Barré Syndrome (pages 5641–5651)

      Dr. Kohki Fujikawa, Shinya Nakashima, Miku Konishi, Tomoaki Fuse, Naoko Komura, Dr. Takayuki Ando, Dr. Hiromune Ando, Dr. Nobuhiro Yuki, Dr. Hideharu Ishida and Dr. Makoto Kiso

      Version of Record online: 5 APR 2011 | DOI: 10.1002/chem.201003357

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      Minor but targeted: Ganglioside GalNAc-GD1a (see figure), carrying two sialyl branches and a target for autoantibodies in Guillain–Barré syndrome (GBS), has been synthesized for the first time in an approach featuring efficient glycan assembly and a cyclic glucosyl ceramide as a versatile unit for ganglioside synthesis. The reactivity of the synthetic GalNAc-GD1a towards serum IgG from GBS patients was comparable to that of natural GalNAc-GD1a.

    13. Functional-Group Transformations

      General Copper-Catalyzed Transformations of Functional Groups from Arylboronic Acids in Water (pages 5652–5660)

      Haijun Yang, Prof. Dr. Yong Li, Min Jiang, Junmei Wang and Prof. Dr. Hua Fu

      Version of Record online: 8 APR 2011 | DOI: 10.1002/chem.201003711

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      Water chemistry: A simple and general copper-catalyzed method has been developed for the transformations of various functional groups on aromatic rings from arylboronic acids in water under air. This study should provide a useful strategy for interconversions of the functional groups on aromatic rings (see scheme).

    14. Cyclisation with Gold

      Gold Catalysis: 1,3-Oxazines by Cyclisation of Allene Amides (pages 5661–5667)

      Prof. Dr. A. Stephen K. Hashmi, Dipl.-Chem. Andreas M. Schuster, Sebastian Litters, Dr. Frank Rominger and Dr. Markus Pernpointner

      Version of Record online: 12 APR 2011 | DOI: 10.1002/chem.201100132

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      Gold and rings: In gold-catalysed reactions, allenamides mainly afford 1,3-oxazines (see figure), through atypical 6-exo-dig or 6-endo-dig cyclisations. Mechanistic and computational studies showed only one additional species, assigned as the σ-allyl gold species bearing the gold catalyst at the sterically less hindered methylene end. Regiospecific deuterodeauration of this intermediate confirmed a SE′-type mechanism for this last step of the catalytic cycle.

    15. Catalytic Mechanisms

      The Remarkable Enhancement of CO-Pretreated CuO[BOND]Mn2O3/γ-Al2O3 Supported Catalyst for the Reduction of NO with CO: The Formation of Surface Synergetic Oxygen Vacancy (pages 5668–5679)

      Dr. Dan Li, Qiang Yu, Shan-Shan Li, Hai-Qin Wan, Lian-Jun Liu, Lei Qi, Bin Liu, Dr. Fei Gao, Prof. Dr. Lin Dong and Prof. Yi Chen

      Version of Record online: 4 APR 2011 | DOI: 10.1002/chem.201002786

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      A catalytic concept: To account for the remarkable enhancement in the activity and selectivity observed during NO reduction by a CO-pretreated CuO[BOND]Mn2O3/γ-Al2O3 catalyst (see figure), the concept of surface synergetic oxygen vacancy (SSOV), which describes the oxygen vacancy formed between individual Mn and Cu ions, is introduced.

    16. Dispersion Interactions

      Three-Dimensional Potential Energy Surface of Selected Carbohydrates’ CH/π Dispersion Interactions Calculated by High-Level Quantum Mechanical Methods (pages 5680–5690)

      Dr. Stanislav Kozmon, Radek Matuška, Dr. Vojtěch Spiwok and Prof. Dr. Jaroslav Koča

      Version of Record online: 8 APR 2011 | DOI: 10.1002/chem.201002876

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      Sugar under control: Three-dimensional potential energy surface scans around selected carbohydrate molecules have shown attractive areas in terms of CH/π interactions (see scheme). The CH/π interaction in these areas has high affinity, up to 5 kcal mol−1, for one carbohydrate's CH group.

    17. DNA Catalysis

      DNA-Based Peroxidation Catalyst—What Is the Exact Role of Topology on Catalysis and Is There a Special Binding Site for Catalysis? (pages 5691–5698)

      Dr. Shizuka Nakayama, Jingxin Wang and Prof. Dr. Herman O. Sintim

      Version of Record online: 5 APR 2011 | DOI: 10.1002/chem.201002349

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      Topsy-turvy activity: Anti-parallel G-quadruplexes are known to be poor peroxidation catalysts. This paper demonstrates that the covalent attachment of a hemin cofactor to G-quadruplexes that form anti-parallel topology promotes the formation of parallel/mixed-hybrid structures and turns a bad peroxidation catalyst into an excellent catalyst (see figure).

    18. Density Functional Calculations

      Toward the Assignment of the Manganese Oxidation Pattern in the Water-Oxidizing Complex of Photosystem II: A Time-Dependent DFT Study of XANES Energies (pages 5699–5713)

      Dr. Adrian R. Jaszewski, Dr. Simon Petrie, Prof. Ronald J. Pace and Prof. Rob Stranger

      Version of Record online: 5 APR 2011 | DOI: 10.1002/chem.201001996

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      Lower than thought: DFT calculations are used to interpret experimental Mn K-edge X-ray absorption near-edge structure spectra from the water-oxidizing complex (WOC) of photosystem II during the water-oxidizing catalytic cycle. The mean oxidation levels of the four Mn centers in the enzyme are systematically lower than previously believed, with mean oxidation states of +2.75 to +3.50 for the four kinetically isolatable intermediate forms of the enzyme (see picture).

    19. Asymmetric Catalysis

      Asymmetric Catalytic Oxidative Cleavage of Polycyclic Systems: The Synthesis of Atropisomeric Diazonanes and Diazecanes (pages 5714–5718)

      Dr. Alan M. Jones, Dr. Gu Liu, Dr. Magali M. Lorion, Dr. Stephen Patterson, Dr. Tomas Lebl, Prof. Alexandra M. Z. Slawin and Dr. Nicholas J. Westwood

      Version of Record online: 5 APR 2011 | DOI: 10.1002/chem.201003188

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      Time for the snip: Nine- and ten-membered-ring-containing heterocycles are prepared by oxidative cleavage of a double bond in the polycyclic substrate by using three different protocols (see picture). The products exhibit atropisomerism and the use of the Nishiyama–Beller ruthenium-based catalysts results in an atropselective oxidative cleavage reaction.

    20. Semiclathrates

      Semiclathrates of the Ge–P–Te System: Synthesis and Crystal Structures (pages 5719–5726)

      Dipl.-Chem. Maria A. Kirsanova, Dr. Liudmila N. Reshetova, Dr. Andrei V. Olenev, Dr. Artem M. Abakumov and Prof. Dr. Andrei V. Shevelkov

      Version of Record online: 5 APR 2011 | DOI: 10.1002/chem.201003553

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      Really attractive! Semiclathrates of the Ge–P–Te system combine structural features of the clathrate I superstructure with, previously unknown for Zintl clathrates, an ability of some of the guest atoms (gold spheres in the figure) to form just one covalent bond with the host framework. Another remarkable property is the notable change in structural features, such as atomic coordination and bond cleavage/formation, with variation of the content of guest tellurium atoms.

    21. Redox Potentials

      Energy-Level Tailoring in a Series of Redox-Rich Quinonoid-Bridged Diruthenium Complexes Containing Tris(2-pyridylmethyl)amine as a Co-Ligand (pages 5727–5736)

      Dipl.-Chem. Fritz Weisser, Dipl.-Chem. Ralph Huebner, Dipl.-Chem. David Schweinfurth and Dr. Biprajit Sarkar

      Version of Record online: 4 APR 2011 | DOI: 10.1002/chem.201003253

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      What a difference a bridge makes! The redox-rich complexes [{Ru(tmpa)}2(μ-L1−2 H)][ClO4]2, [{Ru(tmpa)}2(μ-L2−2 H)][ClO4]2, and [{Ru(tmpa)}2(μ-L3−2 H)][ClO4]2 (tmpa=tris(2-pyridylmethyl) amine) show several redox processes (see figure), the potentials of which can be tuned by systematic variation of the quinonoid bridge. Absorptions in the NIR region can be switched on and off by electron-transfer processes. The position, shape, and intensity of the NIR bands can be tuned by substitution of the quinonoid bridge.

    22. Quantum Dots

      Controlled Synthesis of CdSe Quantum Dots by a Microwave-Enhanced Process: A Green Approach for Mass Production (pages 5737–5744)

      Dr. Delele Worku Ayele, Hung-Ming Chen, Prof. Wei-Nien Su, Chun-Jern Pan, Prof. Liang-Yih Chen, Prof. Hung-Lung Chou, Ju-Hsiang Cheng, Prof. Dr. Bing-Joe Hwang and Jyh-Fu Lee

      Version of Record online: 6 APR 2011 | DOI: 10.1002/chem.201003686

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      Microwave quantum dots: The preparation of CdSe quantum dots (QDs) by a microwave (MW)-enhanced process in aqueous solution is described. A selenium source (Na2SeSO3) was prepared by microwave heating of solution A at 100 W and 100 °C for 30 min. Then different sizes of CdSe QDs with different colors (red, orange, yellow) that can absorb in the visible region were prepared by microwave heating of solution B under different conditions.

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    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Back Cover
    5. Graphical Abstract
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      Preview: Chem. Eur. J. 21/2011 (page 5747)

      Version of Record online: 29 APR 2011 | DOI: 10.1002/chem.201190102

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