Chemistry - A European Journal

Cover image for Vol. 12 Issue 28

September 25, 2006

Volume 12, Issue 28

Pages 7271–7531

  1. Cover Picture

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    1. Cover Picture: The Molecular Basis of Self-Assembly of Dendron–Rod–Coils into One-Dimensional Nanostructures (Chem. Eur. J. 28/2006) (page 7271)

      Eugene R. Zubarev, Eli D. Sone and Samuel I. Stupp

      Version of Record online: 14 SEP 2006 | DOI: 10.1002/chem.200690089

      Supramolecular ribbons are formed by the self-assembly of dendron–rod–coil (DRC) triblock molecules. In their Full Paper on page 7313 ff., S. I. Stupp et al. describe the properties and structural characterization of such molecules. The study provides mechanistic insights and unveils general strategies to create well-defined one-dimensional supramolecular objects.

  2. Graphical Abstract

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    3. Graphical Abstract
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  3. Concept

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    1. Organic Reaction Pathways in the Nonaqueous Synthesis of Metal Oxide Nanoparticles (pages 7282–7302)

      Markus Niederberger and Georg Garnweitner

      Version of Record online: 23 AUG 2006 | DOI: 10.1002/chem.200600313

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      Organic reactions in inorganic synthesis: Organic reactions play a crucial, but yet hardly understood role in the nonaqueous synthesis of crystalline metal oxide nanoparticles. The correlation of the organic reactions to the crystallization of the inorganic nanoparticles, as well as the influence of the organic species on nanoparticle morphology, are great challenges on the way to developing a rational and generally applicable synthesis design for inorganic materials.

  4. Full Papers

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    1. Synthesis, Multiphase Characterization, and Helicity Control in Chiral DACH-Linked Oligothiophenes (pages 7304–7312)

      Manuela Melucci, Giovanna Barbarella, Massimo Gazzano, Massimiliano Cavallini, Fabio Biscarini, Alessandro Bongini, Fabio Piccinelli, Magda Monari, Marco Bandini, Achille Umani-Ronchi and Paolo Biscarini

      Version of Record online: 31 AUG 2006 | DOI: 10.1002/chem.200600312

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      All change! Enantiopure diimino- and diamino-DACH-linked bis(oligothiophenes) that are helical with controlled handedness were synthesized and characterized in solution and cast film. The peculiar behavior of diaminobis(bithiophene), which shows inverted helicity and chiral amplification in the transition from solution to film, is discussed in detail (see figure; DACH=trans-1,2-cyclohexanediamine).

    2. The Molecular Basis of Self-Assembly of Dendron–Rod–Coils into One-Dimensional Nanostructures (pages 7313–7327)

      Eugene R. Zubarev, Eli D. Sone and Samuel I. Stupp

      Version of Record online: 7 AUG 2006 | DOI: 10.1002/chem.200600619

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      Self-assembling triblock molecules, that is, dendron–rod–coil (DRC) molecules, form well-defined supramolecular structures with a ribbonlike morphology (illustrated here). A detailed analysis of crystal structures of model compounds revealed the formation of stable one-dimensional structures that involve two types of noncovalent interactions; aromatic π–π stacking and hydrogen bonding.

    3. Investigation of a Molecular Morphology Effect on Polyphenylazomethine Dendrimers; Physical Properties and Metal-Assembling Processes (pages 7328–7336)

      Takane Imaoka, Reiko Tanaka and Kimihisa Yamamoto

      Version of Record online: 3 AUG 2006 | DOI: 10.1002/chem.200600511

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      Layer-by-layer binding of SnCl2 to substituted dendritic polyphenylazomethines (DPA) occurs in a completely stepwise fashion when the dendritic framework is fixed by steric constraints, as in bis- and tris-substituted DPAs with four generations (G4). However, the process becomes disordered if the framework can bend and freely rotate, as in monosubstituted G4 or tris-substituted G3 (see schematic diagram).

    4. The Domino Chemistry Approach to Molecular Complexity: Competing Domino Processes Modulated by the Substitution Pattern (pages 7337–7344)

      Imad Safir, Isabel Castellote, Susana Porcel, Talbi Kaoudi, Nicolas Birlirakis, Loïc Toupet and Siméon Arseniyadis

      Version of Record online: 7 AUG 2006 | DOI: 10.1002/chem.200600494

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      Ring expansion: A path-selective domino process has been developed that can be employed to provide versatile building blocks for the synthesis of complex molecules. This domino protocol includes the simultaneous formation of additional rings and stereogenic centers with excellent stereo- and regiocontrol in high yields (see scheme). Two quite different products can be formed from the same substrate by the appropriate choice of the angular substituent.

    5. Activating an Enzyme by an Engineered Coiled Coil Switch (pages 7345–7352)

      Satoshi Yuzawa, Toshihisa Mizuno and Toshiki Tanaka

      Version of Record online: 25 JUL 2006 | DOI: 10.1002/chem.200600007

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      A de novo protein based on a circular permutant of RNaseT1 is described, in which the enzymatic activity can be manipulated by engineered peptide binding (see figure).

    6. Probing the Lewis Acidity and Catalytic Activity of the Metal–Organic Framework [Cu3(btc)2] (BTC=Benzene-1,3,5-tricarboxylate) (pages 7353–7363)

      Luc Alaerts, Etienne Séguin, Hilde Poelman, Frédéric Thibault-Starzyk, Pierre A. Jacobs and Dirk E. De Vos

      Version of Record online: 31 JUL 2006 | DOI: 10.1002/chem.200600220

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      A systematic study of the catalytic properties of a metal-organic framework: [Cu3(btc)2] is a very selective catalyst for specific isomerizations of terpenes, terpene epoxides, and ketals (see scheme). Together with IR spectroscopic measurements on adsorbed probe molecules, this proves the hard Lewis acid properties of the material.

    7. Apoptolidinone A: Synthesis of the Apoptolidin A Aglycone (pages 7364–7377)

      Julia Schuppan, Hermut Wehlan, Sonja Keiper and Ulrich Koert

      Version of Record online: 25 JUL 2006 | DOI: 10.1002/chem.200600461

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      An efficient synthesis of apoptolidinone A using a CuI-mediated cross-coupling key step is described. Key steps for the introduction of the southern half stereocenters are a stereoselective aldol reaction, a substrate controlled dihydroxylation and a chelation-controlled Grignard/aldehyde addition. The conjugated triene of the northern half was built up successively by E-selective Wittig reactions.

    8. Apoptolidin A: Total Synthesis and Partially Glycosylated Analogues (pages 7378–7397)

      Hermut Wehlan, Mario Dauber, M. Teresa Mujica Fernaud, Julia Schuppan, Sonja Keiper, Rainer Mahrwald, M.-Elisa Juarez Garcia and Ulrich Koert

      Version of Record online: 25 JUL 2006 | DOI: 10.1002/chem.200600462

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      An early-glycosylation strategy was applied for the total synthesis of apoptolidin A. The cross-coupling of the glycosylated northern half with the glycosylated southern half was achieved with CuI-thiophene carboxylate. The macrocyclization of a trihydroxy carboxylic acid produced the 20-membered macrolide selectively.

    9. Total Syntheses of the Tylophora Alkaloids Cryptopleurine, (−)-Antofine, (−)-Tylophorine, and (−)-Ficuseptine C (pages 7398–7410)

      Alois Fürstner and Jason W. J. Kennedy

      Version of Record online: 31 JUL 2006 | DOI: 10.1002/chem.200600592

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      Potent cytotoxicity against drug sensitive as well as multidrug resistant cancer cell lines is the most striking physiological property of various tylophora alkaloids. To facilitate a more systematic evaluation of this family of natural products, a flexible and concise synthesis route has been developed based on metal catalyzed cross-coupling and cycloisomerization reactions as the key steps. The advantages of this approach are evident from the total synthesis of four representative members of this series (see graphic).

    10. Tetrahedrane—Dossier of an Unknown (pages 7411–7420)

      Adelina Nemirowski, Hans Peter Reisenauer and Peter R. Schreiner

      Version of Record online: 21 JUL 2006 | DOI: 10.1002/chem.200600451

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      Could tetrahedrane be isolated? We address this question with high level ab initio computations (see scheme) and through an experimental re-examination of the reaction of cyclopropene with carbon atoms.

    11. A Range of Spin-Crossover Temperature T1/2>300 K Results from Out-of-Sphere Anion Exchange in a Series of Ferrous Materials Based on the 4-(4-Imidazolylmethyl)-2-(2-imidazolylmethyl)imidazole (trim) Ligand, [Fe(trim)2]X2 (X=F, Cl, Br, I): Comparison of Experimental Results with Those Derived from Density Functional Theory Calculations (pages 7421–7432)

      Gilles Lemercier, Nicolas Bréfuel, Sergiu Shova, Juliusz A. Wolny, Françoise Dahan, Marc Verelst, Hauke Paulsen, Alfred X. Trautwein and Jean-Pierre Tuchagues

      Version of Record online: 28 JUL 2006 | DOI: 10.1002/chem.200501249

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      Spin-crossover temperature controlled by counteranions: A variation of the low-spin⇄high-spin crossover temperature of FeII larger than 300 K was achieved by exchange of the out-of-sphere anion in [Fe(trim)2]X2 (X=F, Cl, Br, I; see picture). The trend for the spin-state splittings calculated with periodic boundary conditions agrees with that observed for the transition temperatures, thus proving the importance of intermolecular effects in tuning the ligand field.

    12. Electrocarboxylation of Benzyl Halides through Redox Catalysis on the Preparative Scale (pages 7433–7447)

      Onofrio Scialdone, Alessandro Galia, Giuseppe Silvestri, Christian Amatore, Laurent Thouin and Jean-Noel Verpeaux

      Version of Record online: 19 JUL 2006 | DOI: 10.1002/chem.200501499

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      Homogeneous charge-transfer catalysis under preparative-scale conditions was investigated both theoretically and experimentally in the framework of the electrocarboxylation of benzyl halides (see graphic). The effect of the particular structuring of the diffusion layer involved in the mediated process, both on the Faradaic efficiency and the catalyst consumption was shown. Strategies for optimizing the process were discussed. A good agreement between theoretical predictions and experimental data was found.

    13. Kinetic Analysis of Semisynthetic Peroxidase Enzymes Containing a Covalent DNA–Heme Adduct as the Cofactor (pages 7448–7457)

      Ljiljana Fruk, Joachim Müller and Christof M. Niemeyer

      Version of Record online: 10 JUL 2006 | DOI: 10.1002/chem.200501613

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      DNA-modified heme cofactor was used to prepare well-defined DNA–enzyme conjugates. A detailed kinetic study enabled the quantification of the DNA–enzyme activity both in solution and immobilized at solid supports by means of the DNA-directed immobilization (DDI) method, and provided initial insights into the catalytic cycles occurring during substrate transformation (see picture).

    14. Identity SN2 Reactions X+CH3X[RIGHTWARDS ARROW]XCH3+X (X=F, Cl, Br, and I) in Vacuum and in Aqueous Solution: A Valence Bond Study (pages 7458–7466)

      Lingchun Song, Wei Wu, Philippe C. Hiberty and Sason Shaik

      Version of Record online: 28 JUL 2006 | DOI: 10.1002/chem.200600372

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      Solvent effects: The valence bond method coupled with a polarized continuum model has been applied to the identity SN2 reaction of halides in the gas phase and in aqueous solution. Reaction barriers were computed, and reactivity parameters were calculated and allowed the valence bond state correlation diagram method to be applied (see figure).

    15. Experimental and Theoretical Characterization of the Valence Isomerization of Bi-2H-azirin-2-yls to Diazabenzenes (pages 7467–7481)

      Klaus Banert, Stefan Grimme, Rainer Herges, Kirsten Heß, Frank Köhler, Christian Mück-Lichtenfeld and Ernst-Ulrich Würthwein

      Version of Record online: 3 JUL 2006 | DOI: 10.1002/chem.200600318

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      Mechanistic details of the aromatization of the title compounds, which leads selectively to pyridazines at surprisingly low temperatures, are given with the help of quantum-chemical calculations. The key reactions include stepwise or simultaneous homolytic cleavage of both C[BOND]N single bonds of the bi-2H-azirin-2-yls to yield energetically favorable nitrogen-centered 1,6-diradicals (see scheme).

    16. Novel Template-Directed Anodic Phenol-Coupling Reaction (pages 7482–7488)

      Itamar M. Malkowsky, Christina E. Rommel, Roland Fröhlich, Ulrich Griesbach, Hermann Pütter and Siegfried R. Waldvogel

      Version of Record online: 28 JUL 2006 | DOI: 10.1002/chem.200600375

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      Substituted phenols were anodically coupled to the corresponding 2,2′-biphenols via tetraphenoxy borate derivatives (see scheme). This electrochemical method is particularly useful for methyl-substituted substrates, such as 2,4-dimethyl phenol. The selective ortho-coupling reaction can be easily performed on a multikilogram scale.

    17. Ligand Topology Effects on Olefin Oxidations by Bio-Inspired [FeII(N2Py2)] Catalysts (pages 7489–7500)

      Rubén Mas-Ballesté, Miquel Costas, Tieme van den Berg and Lawrence Que Jr.

      Version of Record online: 26 JUL 2006 | DOI: 10.1002/chem.200600453

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      Iron-catalyzed oxidations: The topology of the linear tetradentate N2py2 ligand significantly affects the catalytic activity of the non-heme iron center in olefin oxidation, the diol/epoxide ratio, and the reaction mechanism (see scheme).

    18. Mechanistic Investigation of the Oxygen-Atom-Transfer Reactivity of Dioxo-molybdenum(VI) Complexes (pages 7501–7509)

      Brian W. Kail, Lisa M. Pérez, Snežana D. Zarić, Andrew J. Millar, Charles G. Young, Michael B. Hall and Partha Basu

      Version of Record online: 25 JUL 2006 | DOI: 10.1002/chem.200600269

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      Multiple transition states: The oxygen-atom-transfer reactions from a dioxo-MoVI complex involve more than one transition state, as shown here. The reaction mechanism was probed both experimentally and computationally.

    19. Light-Harvesting Metallosupramolecular Squares Composed of Perylene Bisimide Walls and Fluorescent Antenna Dyes (pages 7510–7519)

      Chang-Cheng You, Catharina Hippius, Matthias Grüne and Frank Würthner

      Version of Record online: 25 JUL 2006 | DOI: 10.1002/chem.200600413

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      A fluorescent multichromophore square composed of sixteen dimethylaminonaphthalimide antenna dyes and four central perylene bisimide dyes was constructed by metal-ion-directed self-assembly. Steady-state and time-resolved fluorescence spectroscopy revealed efficient energy transfer from the peripheral naphthalimide dyes to the core perylene bisimide manifold with an energy transfer rate of kT=1.91×109 s−1 and a transfer efficiency of 95 % (see picture). Thus, the macrocyclic array is an efficient artificial model for natural cyclic light-harvesting assemblies.

    20. Discrimination of Metallosupramolecular Architectures in Solution by Using Diffusion Ordered Spectroscopy (DOSY) Experiments: Double-Stranded Helicates of Different Lengths (pages 7520–7525)

      Lionel Allouche, Annie Marquis and Jean-Marie Lehn

      Version of Record online: 28 JUL 2006 | DOI: 10.1002/chem.200600552

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      Know thyself! A series of double helicates were investigated by using 1H NMR DOSY (Diffusion Ordered SpectroscopY) experiments. The spectrum of a mixture of five CuI helicates of the same series, but different in length (see figure), showed the signals of each component with no observable cross-linking, confirming the self-recognition properties of the helicates.

  5. Preview

    1. Top of page
    2. Cover Picture
    3. Graphical Abstract
    4. Concept
    5. Full Papers
    6. Preview
    1. Preview: Chem. Eur. J. 28/2006 (page 7531)

      Version of Record online: 14 SEP 2006 | DOI: 10.1002/chem.200690091

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