Chemistry - A European Journal

Cover image for Vol. 13 Issue 25

August 27, 2007

Volume 13, Issue 25

Pages 7027–7263

  1. Cover Picture

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    1. Cover Picture: Revealing Shape Selectivity and Catalytic Activity Trends Within the Pores of H-ZSM-5 Crystals by Time- and Space-Resolved Optical and Fluorescence Microspectroscopy (Chem. Eur. J. 25/2007) (page 7027)

      Eli Stavitski, Marianne H. F. Kox and Bert M. Weckhuysen

      Article first published online: 15 AUG 2007 | DOI: 10.1002/chem.200790092

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      Wanted!…nonbulky and electron-donating species in zeolite channels! In their Full Paper on page 7057 ff., Bert M. Weckhuysen et al. have demonstrated that the use of combined in-situ optical microspectroscopic and fluorescence microscopic techniques under the same reaction conditions provides very valuable insights into the catalytic processes occurring within a zeolite catalyst particle.

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    1. Graphical Abstract: Chem. Eur. J. 25/2007 (pages 7028–7034)

      Article first published online: 15 AUG 2007 | DOI: 10.1002/chem.200790093

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  4. Concept

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    1. Two-Dimensional Electronic Conjugation: Statics and Dynamics at Structural Domains Beyond Molecular Wires (pages 7040–7049)

      Elizabeth Opsitnick and Dongwhan Lee

      Article first published online: 20 JUL 2007 | DOI: 10.1002/chem.200700813

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      Beyond molecular wires: increasing the spatial dimensionality of electronic conjugation fundamentally modifies its optoelectronic properties. A simple geometric model (illustrated here schematically) shows how the two-dimensional conjugation area contracts and expands reversibly by “correlated” bond rotations. Control over this dynamic process can be achieved by manipulating multiple noncovalent interactions.

  5. Full Papers

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    1. [(dpp-bian)Ga[BOND]Ga(dpp-bian)] and [(dpp-bian)Zn[BOND]Ga(dpp-bian)]: Synthesis, Molecular Structures, and DFT Studies of These Novel Bimetallic Molecular Compounds (pages 7050–7056)

      Igor L. Fedushkin, Anton N. Lukoyanov, Sergey Y. Ketkov, Markus Hummert and Herbert Schumann

      Article first published online: 15 AUG 2007 | DOI: 10.1002/chem.200700736

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      Zinc marriage to gallium: 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) stabilizes gallium–gallium and zinc–gallium bonds. The compound [(dpp-bian)Ga[BOND]Ga(dpp-bian)] was prepared by the reaction of GaCl3 with K3[dpp-bian] and the heterometallic [(dpp-bian)Zn[BOND]Ga(dpp-bian)] by a simple one-pot reaction of [{(dpp-bian)ZnI}2] with GaCl3 and K4[dpp-bian].

    2. Revealing Shape Selectivity and Catalytic Activity Trends Within the Pores of H-ZSM-5 Crystals by Time- and Space-Resolved Optical and Fluorescence Microspectroscopy (pages 7057–7065)

      Eli Stavitski, Marianne H. F. Kox and Bert M. Weckhuysen

      Article first published online: 18 JUL 2007 | DOI: 10.1002/chem.200700568

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      Channeling oligomers: The in-situ investigation of ZSM-5 crystals (see figure) during the oligomerization of various styrene derivatives by means of the complementary methods of optical and fluorescence microspectroscopy reveals that different substituents lead to distinct catalytic activities; electron-donating and nonbulky substituents result in an enhanced reactivity.

    3. Investigation of an Acid–Base and Redox Molecular Switch: From Bulk to the Single-Molecule Level (pages 7066–7074)

      Rabih O. Al-Kaysi, José Luis Bourdelande, Iluminada Gallardo, Gonzalo Guirado and Jordi Hernando

      Article first published online: 22 JUN 2007 | DOI: 10.1002/chem.200700236

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      A pH and redox molecular switch operated at the single-molecule level: The fluorescence of a spirocyclic Meisenheimer complex bearing a guanidine moiety can be reversibly switched on and off upon acid–base addition (see figure) as well as under electrochemical reduction–oxidation. Ultimate monitoring of its switching mechanism at the single-molecule level is achieved by using scanning fluorescence microscopy.

    4. Ligand versus Metal Protonation of an Iron Hydrogenase Active Site Mimic (pages 7075–7084)

      Gerriet Eilers, Lennart Schwartz, Matthias Stein, Giuseppe Zampella, Luca de Gioia, Sascha Ott and Reiner Lomoth

      Article first published online: 13 JUN 2007 | DOI: 10.1002/chem.200700019

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      Who gets the proton? A dibasic hydrogenase active-site mimic can be protonated at either the Fe[BOND]Fe bond or at the ligand nitrogen (see picture) although, as the Fe[BOND]Fe bond is thermodynamically more basic but kinetically inert, ligand protonation is favored. Tautomerization of the metastable N-protonated complex to the stable metal hydride can be accelerated by halides. The doubly protonated complex is easily reduced, but catalytic proton reduction is characterized by slow turnover.

    5. Tryptophan-to-Dye Fluorescence Energy Transfer Applied to Oxygen Sensing by Using Type-3 Copper Proteins (pages 7085–7090)

      Gerhild Zauner, Emanuela Lonardi, Luigi Bubacco, Thijs J. Aartsma, Gerard W. Canters and Armand W. J. W. Tepper

      Article first published online: 19 JUN 2007 | DOI: 10.1002/chem.200601806

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      Oxygen makes the switch: We have devised a simple FRET-based method to make O2-binding “type-3 copper” proteins, such as hemocyanin and tyrosinase, better suited for oxygen-sensing applications. The endogenous tryptophan emission of these proteins reports on the binding of O2 to the copper centre, but this is difficult to detect in samples that show background fluorescence in the near-UV region. To circumvent this problem, the tryptophan emission is translated to emission at higher wavelengths utilizing Fluorescence Resonance Energy Transfer to a label attached to the protein.

    6. Face-Selective [2]- and [3]Rotaxanes: Kinetic Control of the Threading Direction of Cyclodextrins (pages 7091–7098)

      Tomoya Oshikiri, Yoshinori Takashima, Hiroyasu Yamaguchi and Akira Harada

      Article first published online: 12 JUN 2007 | DOI: 10.1002/chem.200601657

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      Face up to it! Kinetic control of the face direction of cyclodextrin (CD) molecules in the construction of pseudorotaxanes with alkyl-chain-bearing pyridinium stoppers is reported. It was found that the number and position of the two methyl substituents on the pyridinium molecules can govern the degree of complex formation of the CD molecules with the axle molecules (see figure).

    7. A Study of (Binap)(enyne)tetracarbonyldicobalt(0) Complexes (pages 7099–7109)

      Susan E. Gibson, David J. Hardick, Peter R. Haycock, Karina A. C. Kaufmann, Ayako Miyazaki, Matthew J. Tozer and Andrew J. P. White

      Article first published online: 26 JUN 2007 | DOI: 10.1002/chem.200700587

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      Heating a series of (binap)(enyne)tetracarbonyldicobalt(0) complexes produces (binap)dicarbonylhydridocobalt(−1) (see figure), a species also observed on monitoring the behaviour of N-(prop-2-enyl)-N-(prop-2-ynyl)-p-toluenesulfonamide, binap and octacarbonyldicobalt(0) under typical catalytic Pauson–Khand conditions.

    8. Synthesis, Photophysical and Electrochemical Properties, and Protein-Binding Studies of Luminescent Cyclometalated Iridium(III) Bipyridine Estradiol Conjugates (pages 7110–7120)

      Kenneth Kam-Wing Lo, Kenneth Yin Zhang, Chi-Keung Chung and Karen Ying Kwok

      Article first published online: 13 JUN 2007 | DOI: 10.1002/chem.200700530

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      Novel luminescent probes for estrogen receptor α were designed by incorporating an estradiol unit into a series of cyclometalated iridium(III) bipyridine complexes. Upon binding to the receptor, all the iridium(III) estradiol conjugates displayed emission enhancement (see picture for an example) and lifetime extension.

    9. Synthesis of the 2,4,5-Tri-tert-butyl-1,3-diphospholide Anion by Phosphinidene Elimination from 2,4,6-Tri-tert-butyl-1,3,5-triphosphabenzene on Treatment with the Amide Li[NPh(SiMe3)] (pages 7121–7128)

      Scott B. Clendenning, Peter B. Hitchcock, Michael F. Lappert, Philippe G. Merle, John F. Nixon and László Nyulászi

      Article first published online: 11 JUN 2007 | DOI: 10.1002/chem.200601626

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      Abstraction of a phosphorus atom from triphosphabenzene affords an intermediate aminophosphinidene, which is further stabilised by the solvent THF and which shows, in agreement with previous theoretical predictions, enhanced stability and reacts then with a second molecule of triphosphabenzene.

    10. Copper(II) Interaction with Prion Peptide Fragments Encompassing Histidine Residues Within and Outside the Octarepeat Domain: Speciation, Stability Constants and Binding Details (pages 7129–7143)

      Katalin Ősz, Zoltán Nagy, Giuseppe Pappalardo, Giuseppe Di Natale, Daniele Sanna, Giovanni Micera, Enrico Rizzarelli and Imre Sóvágó

      Article first published online: 13 JUN 2007 | DOI: 10.1002/chem.200601568

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      Macrochelation preferred: The Cu2+-binding modes to prion protein have been investigated by potentiometric and spectroscopic techniques at different metal-to-ligand ratios. The comparison with appropriate single-histidine-substituted peptide fragments provided evidence for the presence of imidazole-assisted macrochelate complexes (an example of which is shown here) at acidic pH values.

    11. Tandem Exploitation of Helix pomatia Glycosyltransferases: Facile Syntheses of H-Antigen-Bearing Oligosaccharides (pages 7144–7152)

      Hagen Bretting, Friedrich Buck, Günter Jacobs, Sebastian Meinke, Angela M. Scheppokat and Joachim Thiem

      Article first published online: 25 JUN 2007 | DOI: 10.1002/chem.200700440

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      The albumen gland of the snail Helix pomatia contains several glycosyltransferases that can be activated independently to attach step by step either β-(1[RIGHTWARDS ARROW]6)-linked D-Gal or α-(1[RIGHTWARDS ARROW]2)-linked L-Fuc residues to form branched oligosaccharides (see scheme) with multiple H-antigen determinants. These oligosaccharides may be of substantial value to elucidate the specificity of a multitude of carbohydrate-recognizing bioactive molecules.

    12. One-Step Synthesis of Highly Water-Soluble Magnetite Colloidal Nanocrystals (pages 7153–7161)

      Jianping Ge, Yongxing Hu, Maurizio Biasini, Chungli Dong, Jinghua Guo, Ward P. Beyermann and Yadong Yin

      Article first published online: 15 JUN 2007 | DOI: 10.1002/chem.200700375

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      Colloidal magnetite nanocrystals with well-controlled size and size distribution, high crystallinity, and high water solubility have been synthesized by using a high-temperature solution-phase hydrolysis approach. The superior water solubility is achieved by using a polyelectrolyte, that is, poly(acrylic acid) as the capping agent, the carboxylate groups of which partially bind to the nanocrystal surface and partially extend into the surrounding water (see picture).

    13. Asymmetric Hydrogenation Routes to Deoxypolyketide Chirons (pages 7162–7170)

      Jianguang Zhou, James W. Ogle, Yubo Fan, Vorawit Banphavichit(Bee), Ye Zhu and Kevin Burgess

      Article first published online: 21 JUN 2007 | DOI: 10.1002/chem.200700390

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      Interplay of catalyst and substrate vectors allow application of asymmetric hydrogenations to facilitate formation of terminal- and internal-deoxypolyketide chirons (see scheme). Two of the tools used to achieve this were: DFT calculations to understand the abnormal mechanism for hydrogenation of α,β-unsaturated esters and double asymmetric syntheses (Horeau's principle) in reduction of dienes.

    14. Experimental Studies on the trans-Influence of Boryl Ligands in Square-Planar Platinum(II) Complexes (pages 7171–7176)

      Holger Braunschweig, Peter Brenner, Andreas Müller, Krzysztof Radacki, Daniela Rais and Katharina Uttinger

      Article first published online: 26 JUN 2007 | DOI: 10.1002/chem.200700539

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      Boryl is best! A stronger trans-labilizing ability is exerted by boryl ligands than by other boron-based groups. This was determined from a comparison of the Pt[BOND]Br bond lengths in a series of new platinum boryl complexes, trans-[(Cy3P)2Pt(Br){B(X)X′}] with those of known Pt complexes with iminoboryl, base-stabilized and terminal borylene ligands (values of Pt[BOND]Br bond lengths are listed in Å).

    15. Synthesis, X-ray Diffraction and Computational Study of the Crystal Packing of Polycyclic Hydrocarbons Featuring Aromatic and Perfluoroaromatic Rings Condensed in the Same Molecule: 1,2,3,4-Tetrafluoronaphthalene, -anthracene and -phenanthrene (pages 7177–7184)

      Franco Cozzi, Sergio Bacchi, Giuseppe Filippini, Tullio Pilati and Angelo Gavezzotti

      Article first published online: 14 JUN 2007 | DOI: 10.1002/chem.200700267

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      A dramatic change: Molecules in the anthracene crystal pack edge-to-face (left of figure), whereas tetrafluoroanthracene molecules pack in flat layers with overlapping aromatic and perfluoroaromatic rings (right of figure).

    16. Quantum Mechanical Calculations of Conformationally Relevant 1H and 13C NMR Chemical Shifts of N-, O-, and S-Substituted Calixarene Systems (pages 7185–7194)

      Giuseppe Bifulco, Raffaele Riccio, Carmine Gaeta and Placido Neri

      Article first published online: 13 JUN 2007 | DOI: 10.1002/chem.200700238

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      Giving a shape: Quantum mechanics-derived 13C and 1H chemical-shift surfaces versus ϕ and χ dihedral angles of the ArCH2Ar group in simplified calixarene models (see scheme) can be used to predict conformational features in calix[n]arenes.

    17. Tuning the Electronic Properties of N-Heterocyclic Carbenes (pages 7195–7203)

      Steffen Leuthäußer, Daniela Schwarz and Herbert Plenio

      Article first published online: 25 JUN 2007 | DOI: 10.1002/chem.200700228

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      Closing the gap between phosphines and NHC ligands: N-heterocyclic carbenes (NHCs) substituted with electron-deficient groups (see scheme) have the same donor strength as electron-rich trialkylphosphines.

    18. Molecular Optical Switches: Synthesis, Structure, and Photoluminescence of Spirosila Compounds (pages 7204–7214)

      Duanchao Yan, Javad Mohsseni-Ala, Norbert Auner, Michael Bolte and Jan W. Bats

      Article first published online: 26 JUN 2007 | DOI: 10.1002/chem.200700178

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      Molecular optical switches: A series of novel organosilicon based compounds (such as 1, 2, and 3) were synthesized by basic organic and organometallic reaction routes from starting materials 4, 5, and 6. The spiro compounds that combine two organic photoactive subunits at one silicon center were fully characterized and their photoluminescence spectra were recorded. Owing to their optoelectronic properties these compounds might be useful tools for the design of sensitive sensor materials and optical switches.

    19. Transmission of Binding Information across Lipid Bilayers (pages 7215–7222)

      Harmen P. Dijkstra, Jordan J. Hutchinson, Christopher A. Hunter, Haiyuan Qin, Salvador Tomas, Simon J. Webb and Nicholas H. Williams

      Article first published online: 19 JUN 2007 | DOI: 10.1002/chem.200601723

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      Transmembrane communication: A synthetic transmembrane receptor system transmits molecular information across a lipid bilayer by cooperative binding events on the inside and outside of vesicle membranes (see graphic). An extravesicular binding event induces receptor aggregation, resulting in enhanced copper(II) binding to intravesicular aggregated ligand sites.

    20. Nitroxide Radicals as Probes for Exploring the Binding Properties of the Cucurbit[7]uril Host (pages 7223–7233)

      Elisabetta Mezzina, Francesca Cruciani, Gian Franco Pedulli and Marco Lucarini

      Article first published online: 14 JUN 2007 | DOI: 10.1002/chem.200601830

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      A specific EPR spin probe and the corresponding diamagnetic precursors were used to detect the formation of a ternary complex between a cucurbituril derivative, a neutral organic guest, and alkali metal cations. The characteristic timescale of EPR spectroscopy allowed the determination of the exchange rates of the metal cation between the aqueous phase and the nitroxide-CB7 inclusion complex.

    21. The Heteropolytungstate Core {BW13O46}11− Derived as Monomer, Dimer, and Trimer (pages 7234–7245)

      Nathalie Leclerc-Laronze, Jérôme Marrot, Gilbert Hervé, René Thouvenot and Emmanuel Cadot

      Article first published online: 20 JUN 2007 | DOI: 10.1002/chem.200601873

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      The borotungstate system exhibits unconventional reactivity with regard to condensation. The chiral [H3BW13O46]8− precursor leads successively to monomeric {BW14}, dimeric {B2W26}, and trimeric {B3W39} polyoxometalates. The origin of the chirality within the trimeric anion has been examined in detail through structural analyses, combining the X-ray structure and 183W NMR data (1D and 2D COSY; see picture).

    22. Synthesis and Conformational Analysis of Macrocyclic Dihydroxystilbenes Linked between the parapara Positions (pages 7246–7256)

      Carmen Mateo, Vilmarí López, Manuel Medarde and Rafael Peláez

      Article first published online: 13 JUN 2007 | DOI: 10.1002/chem.200700323

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      Anchored in: The conformational restriction of otherwise freely rotating stilbenes is achieved by macrocyclization with linkers of seven or eight atoms (see picture). The accessible conformations of these [2.7]- and [2.8]cyclophanes is relevant in the biological activities of antimitotic stilbenes.

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      Preview: Chem. Eur. J. 26/2007 (page 7263)

      Article first published online: 15 AUG 2007 | DOI: 10.1002/chem.200790095

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