Chemistry - A European Journal

Cover image for Vol. 9 Issue 4

February 17, 2003

Volume 9, Issue 4

Pages 815–1022

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    2. Phase Separation in Metal Oxides (pages 828–836)

      C. N. R. Rao, P. V. Vanitha and Anthony K. Cheetham

      Version of Record online: 5 FEB 2003 | DOI: 10.1002/chem.200390092

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      Some of the transition metal oxides exhibit phase separation due to electronic inhomogeneities or cation disorder, giving rise to metallic ferromagnetic clusters or domains coexisting with insulating, antiferromagnetic regions (see scheme; hatched portions represent the ferromagnetic regions with high carrier concentrations), with the length scale varying from 1 nm to 200 nm. Rare earth manganates show a rich variety of magnetic, electronic and other properties because of phase separation, and the phenomenon appears to be a characteristic of many systems with strongly correlated electrons.

    3. tert-Butylphosphonic Acid: From the Bulk to the Gas Phase (pages 837–849)

      Michael Mehring, Markus Schürmann and Ralf Ludwig

      Version of Record online: 5 FEB 2003 | DOI: 10.1002/chem.200390093

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      tert-Butylphosphonic acid forms strong hydrogen bonds in the solid, in solution and in the gas phase. The crystallization process is solvent-controlled and gives either a one-dimensional polymer or the hexameric cluster C6. In a combined experimental and theoretical approach clusters of different size were observed. The aggregate C6 is energetically favored as a result of strong cooperative enhancement of the hydrogen bonds.

    4. Rapid Screening of Binding Constants by Calibrated Competitive 1H NMR Spectroscopy (pages 850–855)

      Richard E. Heath, Graham M. Dykes, Heather Fish and David K. Smith

      Version of Record online: 5 FEB 2003 | DOI: 10.1002/chem.200390094

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      A method of NMR analysis is reported that enables the rapid assessment of a binding constant by measuring a single standard 1H NMR spectrum (see sketch). This methodology has significance for chemists working in the fields of combinatorial receptor/substrate design and supramolecular chemistry.

    5. Synthesis and Crystal Structure of IM-6, a New Open Framework Cobalt–Gallium Phosphate with Ten- and Twelve-Membered Pore Openings (pages 856–861)

      Ludovic Josien, Angélique Simon-Masseron, Volker Gramlich, Joël Patarin and Loïc Rouleau

      Version of Record online: 5 FEB 2003 | DOI: 10.1002/chem.200390095

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      A new three-dimensional microporous cobalt–gallium phosphate, named IM-6, has been synthesized under solvothermal conditions with an N-substituted piperazine as the organic template. IM-6 exhibits a new framewrok topology. It displays a two-dimensional interconnected channel system running along the [0 equation image 1] and [1 0 0] directions and delimited by ten- and twelve-membered ring openings, respectively.

    6. Iron Twin-Coronet Porphyrins as Models of Myoglobin and Hemoglobin: Amphibious Electrostatic Effects of Overhanging Hydroxyl Groups for Successful CO/O2 Discrimination (pages 862–870)

      Fumito Tani, Mikiya Matsu-ura, Kiyoko Ariyama, Toshikazu Setoyama, Takayuki Shimada, Shinjiro Kobayashi, Takashi Hayashi, Takashi Matsuo, Yoshio Hisaeda and Yoshinori Naruta

      Version of Record online: 5 FEB 2003 | DOI: 10.1002/chem.200390096

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      Better CO/O2selectivity is provided by the overhanging OH groups of twin coronet porphyrin models of myoglobin and hemoglobin with a linked axial imidazole or pyridine ligand. The improved performance is due to the ability of the OH groups to both destabilize the CO adduct by suppressing back-bonding and stabilize the O2 adduct by hydrogen bonding (see schematic diagram).

    7. Determination of the C4[BOND]H Bond Dissociation Energies of NADH Models and Their Radical Cations in Acetonitrile (pages 871–880)

      Xiao-Qing Zhu, Hai-Rong Li, Qian Li, Teng Ai, Jin-Yong Lu, Yuan Yang and Jin-Pei Cheng

      Version of Record online: 11 FEB 2003 | DOI: 10.1002/chem.200390108

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      The C4[BOND]H bond dissociation energies of ten NADH models and their radical cations in acetonitrile were determined for the first time by using titration calorimetry and electrochemistry according to the four thermodynamic cycles constructed from the reactions of the NADH models with N,N,N′,N′-tetramethyl-p-phenylenediamine radical cation perchlorate (see scheme). These results can be used to guide thermodynamic analysis on the mechanism of hydride transfer from NADH and its models.

    8. Stabilities and Isomeric Equilibria in Aqueous Solution of Monomeric Metal Ion Complexes of Adenosine 5′-Diphosphate (ADP3−) in Comparison with Those of Adenosine 5′-Monophosphate (AMP2−) (pages 881–892)

      Emanuela M. Bianchi, S. Ali A. Sajadi, Bin Song and Helmut Sigel

      Version of Record online: 11 FEB 2003 | DOI: 10.1002/chem.200390109

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      The stability constants of metal ion complexes formed with adenosine 5′-diphosphate (ADP3−) were determined in aqueous solution for ten metal ion; the degree of macrochelate formation (involving N7 of the adenine residue) was determined and compared with the corresponding metal ion complexes formed with adenosine 5′-monophosphate (AMP2−).

    9. Fluorogenic Stereochemical Probes for Transaldolases (pages 893–899)

      Eva González-García, Virgil Helaine, Gérard Klein, Melanie Schuermann, Georg A. Sprenger, Wolf-Dieter Fessner and Jean-Louis Reymond

      Version of Record online: 11 FEB 2003 | DOI: 10.1002/chem.200390110

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      A fluorescence assay for probing the activity and stereoselectivity of transaldolases, which catalyze the stereoselective aldol coupling between dihydroxyacetone and α-hydroxyaldehydes, is demonstrated. It is based on synthetic probes that undergo selective retroaldolization with the enzymes to form a fluorescent product. These probes comprise the simple fructose analogue 1 and the stereoisomeric pair 2/3, which is used to measure the fructo/tagato-stereoselectivity of transaldolases.

    10. Synthesis and Nonlinear Optical Absorption of Novel Porphyrin–Osmium-Cluster Complexes (pages 900–904)

      Guo Ying Yang, Siau Gek Ang, Leng Leng Chng, Yiew Wang Lee, Ernest Wei-Pin Lau, Kin Seng Lai and How Ghee Ang

      Version of Record online: 11 FEB 2003 | DOI: 10.1002/chem.200390111

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      The first porphyrin–metal-cluster dyads linked by an axial bridge (e.g., 1) are obtained by the reaction of azidoindium(III)–porphyrin and the osmium cluster [Os3(μ-H)2(CO)10]. The two dyads exhibited a large nonlinear optical absorption at 532 nm with a laser pulse width of 5 ns.

    11. Generation of Reactive Species by One-Electron Reduction of Fischer-Type Carbene Complexes of Group 6 Metals and Their Use for Carbon–Carbon Bond Formation (pages 905–914)

      Kohei Fuchibe and Nobuharu Iwasawa

      Version of Record online: 11 FEB 2003 | DOI: 10.1002/chem.200390112

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      Novel reactive species generated by one-electron reduction of Fischer-type carbene complexes of Group 6 metals were exploited in carbon–carbon bond-forming reactions. One-electron reduction of tungsten arylcarbene complexes afforded anion radical species, which underwent addition to ethyl acrylate. In contrast, one-electron reduction of chromium carbene complexes gave α-methoxyacylchromate complexes by carbonyl insertion, which underwent conjugate addition to various electron-poor olefins (see scheme; EWG=electron-withdrawing group).

    12. Swelling and Shrinking of Polyelectrolyte Microcapsules in Response to Changes in Temperature and Ionic Strength (pages 915–920)

      Changyou Gao, Stefano Leporatti, Sergio Moya, Edwin Donath and Helmuth Möhwald

      Version of Record online: 11 FEB 2003 | DOI: 10.1002/chem.200390113

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      Multilayered polyelectrolyte microcapsules are sensitive to the change of temperature and ionic strength. Swelling and shrinking can be modulated by annealing and electrolyte exporsure, respectively (see scheme). These features will benefit the loading of substances to form filled capsules for drug delivery and controlled release, catalysis, and artificial cells.

    13. Hierarchical Self-Assembly, Coassembly, and Self-Organization of Novel Liquid Crystalline Lattices and Superlattices from a Twin-Tapered Dendritic Benzamide and Its Four-Cylinder-Bundle Supramolecular Polymer (pages 921–935)

      Virgil Percec, Tushar K. Bera, Martin Glodde, Qiongying Fu, Venkatachalapathy S. K. Balagurusamy and Paul A. Heiney

      Version of Record online: 11 FEB 2003 | DOI: 10.1002/chem.200390114

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      A diversity of novel liquid crystalline superlattices was coassembled from a four-cylinder-bundle supramolecular dendrimer self-assembled from a polymethacrylate containing twin-dendritic benzamide side groups and the low molecular mass twin-dendritic benzamide that self-assembles in a supramolecular cylinder (see picture).

    14. Synthesis and Characterization of Luminescent Rod–Coil Block Copolymers by Atom Transfer Radical Polymerization: Utilization of Novel End-Functionalized Terfluorenes as Macroinitiators (pages 936–943)

      Panagiotis K. Tsolakis and Joannis K. Kallitsis

      Version of Record online: 11 FEB 2003 | DOI: 10.1002/chem.200390115

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      Rod-coil triblock copolymers bearing well-defined oligofluorene units (e.g., 1) have been synthesized by using atom transfer radical polymerization (ATRP). The resulting copolymers were characterized by using spectroscopic and optical techniques. The optical properties did not vary when passing from solution to the solid state. No excimer formation was observed in the solid state, even after thermal processing, making these materials promising candidates for electronic applications.

    15. Fragmentation of Transition Metal Carbonyl Cluster Anions: Structural Insights from Mass Spectrometry (pages 944–950)

      Colin P. G. Butcher, Paul J. Dyson, Brian F. G. Johnson, Tetyana Khimyak and J. Scott McIndoe

      Version of Record online: 11 FEB 2003 | DOI: 10.1002/chem.200390116

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      Metal core rearrangement of anionic transition metal carbonyl clusters can be clearly observed by energy-dependent electrospray ionisation mass spectrometry. Insight into the geometry of the polyhedral core can be obtained and the gas-phase transformations mirror those that take place in solution (see picture).

    16. A Computational Study of Regioselectivity in a Cyclodextrin-Mediated Diels–Alder Reaction: Revelation of Site Selectivity and the Importance of Shallow Binding and Multiple Binding Modes (pages 951–962)

      Wan-Sheung Li, Wen-Sheng Chung and Ito Chao

      Version of Record online: 11 FEB 2003 | DOI: 10.1002/chem.200390117

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      MD simulations bring insights to the change in regioselectivity of a Diels–Alder reaction in the presence of β-cyclodextrin and modified cyclodextrin.

    17. Neutral and Ionic Hydrogen Bonding in Schiff Bases (pages 963–970)

      Paulina M. Dominiak, Eugeniusz Grech, Gordon Barr, Simon Teat, Paul Mallinson and Krzysztof Woźniak

      Version of Record online: 11 FEB 2003 | DOI: 10.1002/chem.200390118

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      According to the geometrical and critical point parameters in Schiff bases the neutral O[BOND]H⋅⋅⋅N hydrogen bond seems to be stronger than ionic hydrogen bonds. There are also differences between the charge density parameters of the aromatic rings which are consistent with the neutral hydrogen bond being stronger than the ionic equivalent, with a consequent reduction in the aromaticity of the ring. The figure shows Laplacian maps in the plane of the hydrogen bond rings: left: neutral O[BOND]H⋅⋅⋅N bond; right: ionic O[BOND]H⋅⋅⋅N bond.

    18. Re-Based Heterogeneous Catalysts for Olefin Metathesis Prepared by Surface Organometallic Chemistry: Reactivity and Selectivity (pages 971–975)

      Mathieu Chabanas, Christophe Copéret and Jean-Marie Basset

      Version of Record online: 11 FEB 2003 | DOI: 10.1002/chem.200390119

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      The well-defined Re alkylidene complex 1 supported on silica, prepared by surface organometallic chemistry, is highly active in olefin metathesis (see diagram).

    19. Combinatorial Library of Low Molecular-Weight Organo- and Hydrogelators Based on Glycosylated Amino Acid Derivatives by Solid-Phase Synthesis (pages 976–983)

      Shigeki Kiyonaka, Seiji Shinkai and Itaru Hamachi

      Version of Record online: 11 FEB 2003 | DOI: 10.1002/chem.200390120

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      Glycosylated amino acetate based low molecular weight organo- and hydrogelators were efficiently discovered by a combinatorial solid-phase synthesis approach. The supramolecular hydrogel thus obtained could successfully entrap a native protein in its active form.

    20. Preorganization and Reorganization as Related Factors in Enzyme Catalysis: The Chorismate Mutase Case (pages 984–991)

      Sergio Martí, Juan Andrés, Vicent Moliner, Estanislao Silla, Iñaki Tuñón and Juan Bertrán

      Version of Record online: 11 FEB 2003 | DOI: 10.1002/chem.200390121

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      A theoretical insight into the chorismate-to-prephenate rearrangement, catalyzed by Bacillus subtilis chorismate mutase, by means of statistical quantum mechanics/molecular mechanics methods is provided. In this reaction the enzyme is optimized to interact with the transition structure (see picture), but these same interactions have important effects on the reactant structure. The key factor, sometimes not stressed enough in the literature, is the importance of enzyme deformation during the enzymatic process.

    21. Towards a Universal Polymer Backbone: Design and Synthesis of Polymeric Scaffolds Containing Terminal Hydrogen-Bonding Recognition Motifs at Each Repeating Unit (pages 992–999)

      Ludger P. Stubbs and Marcus Weck

      Version of Record online: 11 FEB 2003 | DOI: 10.1002/chem.200390122

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      A polymeric scaffold for the self-assembly of receptors through hydrogen bonding was synthesized by ring-opening metathesis polymerization of norbornenes functionalized with donor–acceptor–donor recognition units. Diaminopyridine-based monomers, such as that depicted, proved to be superior to diaminotriazines due to their low dimerization and high association constants.

    22. Evidence for the Intermediacy of Arylbenzylnitrenium Ions in the Thermal Rearrangement of Isoxazolidines Derived from C,N-Diarylnitrones and 2-Morpholin-4-yl-acrylonitrile (pages 1000–1007)

      Annie Liard, Thi-Huu Nguyen, Abdel Illah Djelloul Smir, Michel Vaultier, Aïcha Derdour and Jacques Mortier

      Version of Record online: 11 FEB 2003 | DOI: 10.1002/chem.200390102

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      Arylbenzylnitrenium ions can be generated by a process involving an unprecedented thermal rearrangement of isoxazolidines derived from C,N-diarylnitrones and 2-morpholin-4-yl-acrylonitrile (see scheme). Most of the observed chemistry originates from the singlet state.

    23. Conformers of Gaseous Proline (pages 1008–1019)

      Eszter Czinki and Attila G. Császár

      Version of Record online: 11 FEB 2003 | DOI: 10.1002/chem.200390103

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      For eighteen conformers of neutral L-proline accurate geometries, relative energies, rotational and quartic centrifugal distortion constants, dipole moments, harmonic vibrational frequencies, and infrared intensities were determined from converged ab initio electronic structure calculations. Only the four conformers shown in the picture have notable populations at low and moderate temperature. Conformer II lies only 2±2 kJ mol−1 above the global minimum I, whereas the third and fourth conformers are nearly degenerate and have an excess energy of 7±2 kJ mol−1.

    24. Preview: Chem. Eur. J. 4/2003 (page 1022)

      Version of Record online: 11 FEB 2003 | DOI: 10.1002/chem.200390104