Chemistry - A European Journal

Cover image for Chemistry - A European Journal

June 6, 2011

Volume 17, Issue 24

Pages 6565–6871

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. News
    6. Concept
    7. Communications
    8. Full Papers
    9. Preview
    1. Cover Picture: Solvent-Dependent Aromatic versus Antiaromatic Conformational Switching in meso-(Heptakis)pentafluorophenyl [32]Heptaphyrin (Chem. Eur. J. 24/2011) (page 6565)

      Dr. Min-Chul Yoon, Jae-Yoon Shin, Jong Min Lim, Dr. Shohei Saito, Tomoki Yoneda, Prof. Dr. Atsuhiro Osuka and Prof. Dr. Dongho Kim

      Version of Record online: 26 MAY 2011 | DOI: 10.1002/chem.201190120

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      Conformational switching between Möbius aromatic and Hückel antiaromatic congeners in expanded porphyrins has been optically identified by using solvent- and excitation-wavelength-dependent time-resolved absorption measurements. In the Full Paper by D. Kim and co-workers on page 6707 ff., photophysical properties along with theoretical calculations are used to show that the molecular aromaticity is sensitive to surrounding environments in expanded porphyrinoid systems.

  2. Inside Cover

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. News
    6. Concept
    7. Communications
    8. Full Papers
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    1. Inside Cover: Fast and High-Resolution Stereochemical Analysis by Nonuniform Sampling and Covariance Processing of Anisotropic Natural Abundance 2D 2H NMR Datasets (Chem. Eur. J. 24/2011) (page 6566)

      Dr. Olivier Lafon, Dr. Bingwen Hu, Prof. Jean-Paul Amoureux and Dr. Philippe Lesot

      Version of Record online: 26 MAY 2011 | DOI: 10.1002/chem.201190121

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      The accurate determination of natural 1H/2H isotopic fractions on biological-interest molecules, such as fatty acids, by using natural abundance 2H 2D NMR spectroscopy in chiral-oriented media provides new and crucial stereochemical information on their bioenzymatic synthesis. Combining non-uniform sampling and covariance transform strongly improves the quality of such analyses, and decreases the experimental measurement time by at least a factor of four, as shown by as shown by O. Lafon, P. Lesot et al. in their Full Paper on page 6716 ff.

  3. Graphical Abstract

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    3. Inside Cover
    4. Graphical Abstract
    5. News
    6. Concept
    7. Communications
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  4. News

    1. Top of page
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    4. Graphical Abstract
    5. News
    6. Concept
    7. Communications
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  5. Concept

    1. Top of page
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    3. Inside Cover
    4. Graphical Abstract
    5. News
    6. Concept
    7. Communications
    8. Full Papers
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    1. Gold Nanoclusters

      Quantum-Sized Gold Nanoclusters: Bridging the Gap between Organometallics and Nanocrystals (pages 6584–6593)

      Prof. Rongchao Jin, Yan Zhu and Huifeng Qian

      Version of Record online: 17 MAY 2011 | DOI: 10.1002/chem.201002390

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      Small is beautiful: Ultrasmall gold nanoparticles of 1–2 nm in size (also called nanoclusters) lie in between organogold compounds (e.g., few-atom complexes, <1 nm) and fcc crystalline Au nanoparticles (typically >2 nm). A lot of transitions, including atomic packing structure, electronic, and optical properties, occur over this size regime. Fundamental understanding of the evolution from the atomic state to nanoclusters to fcc-structured nanocrystals is of crucial importance and constitutes a major undertaking in nanoscience research, and will ultimately impact chemistry, condensed matter physics, and materials science.

  6. Communications

    1. Top of page
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    3. Inside Cover
    4. Graphical Abstract
    5. News
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    1. Metal–Organic Frameworks

      B[BOND]N Chemistry@ZIF-8: Dehydrocoupling of Dimethylamine Borane at Room Temperature by Size-Confinement Effects (pages 6594–6597)

      Dr. Suresh Babu Kalidindi, Daniel Esken and Prof. Dr. Roland A. Fischer

      Version of Record online: 26 APR 2011 | DOI: 10.1002/chem.201100518

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      Confined coupling: A dimethylamine borane adduct undergoes catalytic dehydrocoupling inside a zeolite–imidazole framework (ZIF-8) to yield the cyclic dimer (Me2N⋅BH2)2 under mild conditions owing to strong caging effects (see graphic).

    2. Chemosensors

      Calix[2]-m-benzo[4]phyrin with Aggregation-Induced Enhanced-Emission Characteristics: Application as a HgII Chemosensor (pages 6598–6601)

      P. S. Salini, Ajesh P. Thomas, R. Sabarinathan, S. Ramakrishnan, K. C. Gowri Sreedevi, Dr. M. L. P. Reddy and Dr. A. Srinivasan

      Version of Record online: 28 APR 2011 | DOI: 10.1002/chem.201100046

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      Quenched by mercury: A hybrid, core-modified, expanded calixphyrin was synthesized, confirmed by single-crystal X-ray analysis, and found to exhibit aggregation-induced enhanced-emission (AIEE) characteristics. The aggregate formation was confirmed by HR-TEM analysis. The efficient emission in aqueous solution and in the solid state was utilized for metal-ion-sensing studies, which concluded a potential application for selective detection of HgII ions (see graphic).

    3. Bond Analysis

      Do ν(CO) Stretching Frequencies in Metal Carbonyl Complexes Unequivocally Correlate with the Intrinsic Electron-Donicity of Ancillary Ligands? (pages 6602–6605)

      Dr. Dmitry A. Valyaev, Rémy Brousses, Dr. Noël Lugan, Dr. Israel Fernández and Prof. Dr. Miguel A. Sierra

      Version of Record online: 5 MAY 2011 | DOI: 10.1002/chem.201100651

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      Distorting the ν(CO) response: Weak Cipso⋅⋅⋅C[TRIPLE BOND]O and Hortho⋅⋅⋅C[TRIPLE BOND]O interligand interactions within MnI aryloxycarbene complexes are seen to induce a significant redshift of the corresponding IR ν(CO) stretching frequencies, revealing that the position of such bands may not unequivocally correlate with the intrinsic electron-donicity of ancillary ligands.

    4. N-Heterocyclic Carbenes

      Enabling Bifunctionality and Hemilability of N-Heteroaryl NHC Complexes (pages 6606–6609)

      Zephen G. Specht, Prof. Sara A. Cortes-Llamas, Hai N. Tran, Christoffel J. van Niekerk, Khing T. Rancudo, Prof. James A. Golen, Dr. Curtis E. Moore, Prof. Arnold L. Rheingold, Prof. Tammy J. Dwyer and Prof. Douglas B. Grotjahn

      Version of Record online: 29 APR 2011 | DOI: 10.1002/chem.201100521

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      Functionalized carbene ligands: Increasing the steric bulk of R1 on 1 from H to tBu results in lengthening of the M[BOND]N bond (by up to 9 %), lowered activation energy for chelate opening (cf. 2) by 17 kcal mol−1, and improved binding of an amine and intramolecular hydrogen bonding (3). Iridium species with R1=tBu are effective catalysts of base-free intramolecular hydroamination, unlike less-hindered analogues.

    5. Near-IR Dyes

      BODIPY-Fused Porphyrins as Soluble and Stable Near-IR Dyes (pages 6610–6614)

      Chongjun Jiao, Lijun Zhu and Prof. Jishan Wu

      Version of Record online: 26 APR 2011 | DOI: 10.1002/chem.201100619

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      Beneficial fusion! Boron dipyrromethene (BODIPY) has been successfully fused to a porphyrin core by an intramolecular, oxidative, cyclodehydrogenation reaction. The newly synthesized dyes 1 and 2 have good solubility and exhibit intensified near-IR absorption and remarkable photostability.

    6. Nanostructures

      Controllable Nanocarving of Anatase TiO2 Single Crystals with Reactive {001} Facets (pages 6615–6619)

      Xiao Hua Yang, Prof. Dr. Hua Gui Yang and Prof. Dr. Chunzhong Li

      Version of Record online: 28 APR 2011 | DOI: 10.1002/chem.201100134

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      The dual role of HF: Controllable nanocarving of {001} faceted anatase TiO2 single crystals was achieved through various chemical processes involving HF, which was revealed to predominantly act as an etching agent during the process. The etching activity preferably occurred on the highly reactive {001} facets (see figure). Moreover, isopropanol can retard the etching of {001} faceted surfaces effectively.

    7. Antitumor Complexes

      Cytotoxicity of Gold(I) N-Heterocyclic Carbene Complexes Assessed by Using Human Tumor Cell Lines (pages 6620–6624)

      Dr. Jennifer Weaver, Dr. Sylvain Gaillard, Caroline Toye, Stephen Macpherson, Prof. Dr. Steven P. Nolan and Prof. Andrew Riches

      Version of Record online: 3 MAY 2011 | DOI: 10.1002/chem.201100321

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      Antitumor AuI–NHC: Gold(I) N-heterocyclic carbene complexes exhibit marked cytotoxicity to human tumor cell lines. The cytotoxicity is dependent on the group bound to the gold–NHC moiety: [Au(OH)(IPr)] (1) and [Au(IPr)Cl] (2) are most effective. There was no difference between the cytotoxic effects on normal prostate or breast epithelial cells compared to tumor cells from the same tissue. The active compounds were more potent than cisplatin.

  7. Full Papers

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

      A Highly Selective, Cell-Permeable Fluorescent Nanoprobe for Ratiometric Detection and Imaging of Peroxynitrite in Living Cells (pages 6626–6634)

      Jiangwei Tian, Huachao Chen, Linhai Zhuo, Yanxia Xie, Na Li and Prof. Bo Tang

      Version of Record online: 17 MAY 2011 | DOI: 10.1002/chem.201100148

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      The living daylights: A polymeric micelle-based and cell-penetrating peptide-coated fluorescent nanoprobe incorporates ONOO indicator dye (benzylselenide-tricarbocyanine, BzSe-Cy) and reference dye (isopropylrhodamine B, IRhB) for ratiometric detection and imaging of ONOO in living cells. The nanoprobe exhibits good biocompatibility and membrane permeability for intracellular ONOO imaging.

    2. Polyoxometalates

      Reduced Molybenum-Oxide-Based Core–Shell Hybrids: “Blue” Electrons Are Delocalized on the Shell (pages 6635–6642)

      Dr. Ana Maria Todea, Julia Szakács, Dr. Sanjit Konar, Dr. Hartmut Bögge, Prof. Dr. Debbie C. Crans, Prof. Dr. Thorsten Glaser, Hélène Rousselière, Dr. René Thouvenot, Prof. Dr. Pierre Gouzerh and Prof. Dr. Achim Müller

      Version of Record online: 3 MAY 2011 | DOI: 10.1002/chem.201003260

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      Competition for electrons: In metal-oxide-based core–shell hybrids, in which the core (Keggin ion) as well as the shell (Keplerate cluster) can both easily be reduced, the electrons appear preferably delocalized on the shell.

    3. Microporous Materials

      Modulated Synthesis of Zr-Based Metal–Organic Frameworks: From Nano to Single Crystals (pages 6643–6651)

      Andreas Schaate, Pascal Roy, Prof. Dr. Adelheid Godt, Jann Lippke, Florian Waltz, Dr. Michael Wiebcke and Prof. Dr. Peter Behrens

      Version of Record online: 5 MAY 2011 | DOI: 10.1002/chem.201003211

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      Modulated crystallinity: Nanocrystals of varying sizes of UiO-66 (Zr–bdc metal–organic framework (MOF)), individual microcrystals of UiO-67 (Zr–bpdc MOF) and the first single crystal of a Zr-based MOF containing a long linker (Zr–tpdc–NH2 MOF) were obtained (see figure). The last one allowed, for the first time, a single-crystal diffraction study of a Zr-based MOF. (H2bdc: terephthalic acid, H2bpdc: biphenyl-4,4′-dicarboxylic acid, H2tpdc: terphenyl-4,4′′-dicarboxylic acid.)

    4. Photochromic Behavior

      Mechanistic Insights into Photochromic Behavior of a Ruthenium(II)–Pterin Complex (pages 6652–6662)

      Dr. Tomoya Ishizuka, Takuya Sawaki, Dr. Soushi Miyazaki, Prof. Dr. Masaki Kawano, Dr. Yoshihito Shiota, Prof. Dr. Kazunari Yoshizawa, Prof. Dr. Shunichi Fukuzumi and Prof. Dr. Takahiko Kojima

      Version of Record online: 3 MAY 2011 | DOI: 10.1002/chem.201003522

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      There and back again: The pterin-coordinated ruthenium(II) complex, [RuII(dmdmp)(tpa)]+ (Hdmdmp=N,N-dimethyl-6,7-dimethylpterin; tpa=tris(2-pyridylmethyl)amine), performs photoinduced isomerization. The resulting isomer complex can reversibly turn back to the original complex through a thermal process (see graphic).

      Corrected by:

      Corrigendum: Corrigendum: Mechanistic Insights into Photochromic Behavior of a Ruthenium(II)–Pterin Complex

      Vol. 17, Issue 36, 9858, Version of Record online: 22 AUG 2011

    5. Molecular Electronics

      Synthesis and Photoswitching Studies of Difurylperfluorocyclopentenes with Extended π-Systems (pages 6663–6672)

      Dmytro Sysoiev, Artem Fedoseev, Youngsang Kim, Dr. Thomas E. Exner, Prof. Dr. Johannes Boneberg, Dr. Thomas Huhn, Prof. Dr. Paul Leiderer, Prof. Dr. Elke Scheer, Prof. Dr. Ulrich Groth and Prof. Dr. Ulrich E. Steiner

      Version of Record online: 5 MAY 2011 | DOI: 10.1002/chem.201003716

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      Photoswitches: Novel molecular photoswitches based on the difurylperfluorocyclopentene chromophore and carrying π-system-extending substituents with terminal anchor groups to gold were synthesized and characterized spectrally and photokinetically (see figure). Preliminary surface plasmon resonance experiments demonstrate reversible photoswitching in monolayers on gold.

    6. Mesoporous Materials

      Functionalization of Mesoporous Carbon with Superbasic MgO Nanoparticles for the Efficient Synthesis of Sulfinamides (pages 6673–6682)

      Dr. Rajashree Chakravarti, Ajayan Mano, Dr. Hideo Iwai, Prof. Salem S. Aldeyab, R. Pradeep Kumar, Dr. M. Lakshmi Kantam and Prof. Ajayan Vinu

      Version of Record online: 27 APR 2011 | DOI: 10.1002/chem.201002885

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      Reuse and recycle: Highly basic MgO-functionalized mesoporous carbon with different pore diameters has been prepared (see picture). The material showed a much higher performance in the synthesis of sulfinamides than pure MgO nanoparticles. The catalyst was also highly stable and could be reused several times without affecting its activity.

    7. DNA Constructs

      Assembly of DNA Triangles Mediated by Perylene Bisimide Caps (pages 6683–6688)

      Dipl.-Chem. Florian Menacher, Dr. Vladimir Stepanenko, Prof. Frank Würthner and Prof. Hans-Achim Wagenknecht

      Version of Record online: 29 APR 2011 | DOI: 10.1002/chem.201100141

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      Red glue for DNA: Perylene bisimides, as caps of a Y-shaped triangular DNA construct, drive the assembly of branched higher structures by dimerization due to strong π–π interactions (see figure). This dimerization yields characteristic optical changes of the material, giving rise to the red color in the photograph.

    8. Gas Separation

      Selective CO2 Adsorption by a Triazacyclononane-Bridged Microporous Metal–Organic Framework (pages 6689–6695)

      Guillaume Ortiz, Dr. Stéphane Brandès, Dr. Yoann Rousselin and Prof. Roger Guilard

      Version of Record online: 28 APR 2011 | DOI: 10.1002/chem.201003680

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      CO2capture: An unprecedented metal–organic framework, composed of a cyclic polyamine, was synthesised from a N-carboxybenzyl-functionalised triazacyclononane and Zn2+ (see figure). The resulting material exhibits a high capacity and selectivity for CO2 over CO, CH4, N2 and O2, and is a good compromise to design a new adsorbent for CO2 capture.

    9. Fluorescence and Magnetism

      Silica Nanocapsules of Fluorescent Conjugated Polymers and Superparamagnetic Nanocrystals for Dual-Mode Cellular Imaging (pages 6696–6706)

      Happy Tan, Miao Wang, Dr. Chang-Tong Yang, Shilpa Pant, Dr. Kishore Kumar Bhakoo, Siew Yee Wong, Dr. Zhi-Kuan Chen, Dr. Xu Li and Prof. Dr. John Wang

      Version of Record online: 3 MAY 2011 | DOI: 10.1002/chem.201003632

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      Template synthesis: Fluorescent conjugated polymers are successfully integrated with superparamagnetic iron oxide nanocrystals inside PEOlated (PEO=poly(ethylene oxide)) silica nanocapsules to form a new type of bifunctional nanostructure (see figure), which can be used for dual-mode fluorescence and magnetic resonance cellular imaging.

    10. Aromaticity

      Solvent-Dependent Aromatic versus Antiaromatic Conformational Switching in meso-(Heptakis)pentafluorophenyl [32]Heptaphyrin (pages 6707–6715)

      Dr. Min-Chul Yoon, Jae-Yoon Shin, Jong Min Lim, Dr. Shohei Saito, Tomoki Yoneda, Prof. Dr. Atsuhiro Osuka and Prof. Dr. Dongho Kim

      Version of Record online: 12 MAY 2011 | DOI: 10.1002/chem.201003736

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      Between Hückel and Möbius: Switching dynamics of [32]heptaphyrin between Hückel antiaromatic and Möbius aromatic conformers are strongly affected by solvent polarity as well as temperature. Existence of conformers different in structure and aromaticity has been revealed mainly by time-resolved spectroscopic measurements along with theoretical calculations (see graphic).

    11. NMR Spectroscopy

      Fast and High-Resolution Stereochemical Analysis by Nonuniform Sampling and Covariance Processing of Anisotropic Natural Abundance 2D 2H NMR Datasets (pages 6716–6724)

      Dr. Olivier Lafon, Dr. Bingwen Hu, Prof. Jean-Paul Amoureux and Dr. Philippe Lesot

      Version of Record online: 11 MAY 2011 | DOI: 10.1002/chem.201100461

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      2H or not2H: The combination of nonuniform sampling and covariance transform allows fast and accurate stereochemical analysis of isotopic enantio- and diastereomers (see figure). This general method has permitted the acquisition of high- resolution 2D NMR spectra by using a measurement time at least four times shorter than that required by conventional approaches.

    12. Structure Determination

      Molecular Structures of THF-Solvated Alkali-Metal 2,2,6,6-Tetramethylpiperidides Finally Revealed: X-ray Crystallographic, DFT, and NMR (including DOSY) Spectroscopic Studies (pages 6725–6730)

      Dr. David R. Armstrong, Dr. Pablo García-Álvarez, Dr. Alan R. Kennedy, Prof. Robert E. Mulvey and Dr. Stuart D. Robertson

      Version of Record online: 29 APR 2011 | DOI: 10.1002/chem.201100523

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      Structure solved: THF-solvated lithium 2,2,6,6-tetramethylpiperidide (LiTMP) is established as a cyclodimer with an asymmetric (LiN)2 ring in the solid state (see scheme). In non-polar solvents, a concentration-dependent equilibrium exists between this dimer, a solvated monomer and unsolvated LiTMP, as confirmed by multinuclear and diffusion-ordered NMR spectroscopy.

    13. Zwitterion Synthesis

      Synthesis and Reactivity of Alkynyl-Linked Phosphonium Borates (pages 6731–6743)

      Xiaoxi Zhao, Dr. Alan J. Lough and Prof. Dr. Douglas W. Stephan

      Version of Record online: 5 MAY 2011 | DOI: 10.1002/chem.201100203

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      Born of frustration: Zwitterionic alkynyl-linked phosphonium borates of the form R2P(R′)C[TRIPLE BOND]CB(C6F5)2X (see graphic) were prepared. In addition to studying their fundamental reactivity, these species are used in the synthesis of macrocyclic species in which P and B are linked by addition to olefins, alkynes, or the ring opening of THF. These compounds are also shown to react readily with a variety of Lewis acids including AlX3 (X=Cl, Br), [Zn(C6F5)2]C7H8, [Al(C6F5)3]C7H8, and HB(C6F5)2.

    14. Bioorganometallic Chemistry

      Probing the Role of the Linker in Ferrocene–ATP Conjugates: Monitoring Protein Kinase Catalyzed Phosphorylations Electrochemically (pages 6744–6752)

      Dr. Sanela Martić, Dr. Mahmoud Labib, Daniel Freeman and Prof. Heinz-Bernhard Kraatz

      Version of Record online: 3 MAY 2011 | DOI: 10.1002/chem.201003535

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      Size does matter! Ferrocene (Fc)–ATP bioconjugates act as reporters for the kinase-catalyzed phosphorylation through peptide-based biosensing platforms. Studies support the relationship between the Fc–ATP structure (see graphic) and protein kinase; a relationship that potentially modulates the phosphorylation and analytical response.

    15. Polynuclear Lanthanides

      Thermodynamics, Structure and Properties of Polynuclear Lanthanide Complexes with a Tripodal Ligand: Insight into their Self-Assembly (pages 6753–6764)

      Dr. Josef Hamacek, Dr. Céline Besnard, Dr. Tiphaine Penhouet and Dr. Pierre-Yves Morgantini

      Version of Record online: 5 MAY 2011 | DOI: 10.1002/chem.201100173

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      Three-legged race: The reaction of a tripodal ligand with lanthanides (see figure) has been investigated by using supramolecular analytical tools. An equimolar mixture of components gives tetranuclear helical complexes. A new trinuclear complex formed in the presence of excess metal was characterised by crystallography. The self-assembly processes were studied by using thermodynamic modelling of stability constants.

    16. Amino Acids

      Efficient Copper-Catalyzed Synthesis of Poly-N-Heterocycles Containing Amino Acid Residues (pages 6765–6771)

      Tao Liu, Prof. Dr. Ruji Wang, Haijun Yang and Prof. Dr. Hua Fu

      Version of Record online: 27 APR 2011 | DOI: 10.1002/chem.201100690

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      Ullmann-type coupling: An efficient copper-catalyzed method has been developed for the synthesis of poly-N-heterocycles containing amino acid residues (see scheme). The protocol uses readily available 2-halobenzamides containing amino acids and their methyl esters, substituted phenylacetonitriles, and malononitrile as the starting materials.

    17. Supramolecular Self-Assembly

      Carbon Nanotube–Nucleobase Hybrids: Nanorings from Uracil-Modified Single-Walled Carbon Nanotubes (pages 6772–6780)

      Dr. Prabhpreet Singh, Dr. Francesca Maria Toma, Dipl.-Chem. Jitendra Kumar, Dipl.-Chem. V. Venkatesh, Dr. Jesus Raya, Prof. Dr. Maurizio Prato, Prof. Dr. Sandeep Verma and Dr. Alberto Bianco

      Version of Record online: 3 MAY 2011 | DOI: 10.1002/chem.201100312

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      Go nano! Uracil-functionalized single-walled carbon nanotubes (SWCNTs) result in the formation of nanorings (see figure). The simplest model for the nanoring formation involves two bundles of CNTs interacting with each other through uracil–uracil base-pairing at both nanotube ends. These nanorings can be exploited for the development of new electronic devices.

    18. Solar Cells

      Heteroleptic Ruthenium Sensitizers That Contain an Ancillary Bipyridine Ligand Tethered with Hydrocarbon Chains for Efficient Dye-Sensitized Solar Cells (pages 6781–6788)

      Dr. Yung-Sheng Yen, Dr. Yung-Chung Chen, Dr. Ying-Chan Hsu, Dr. Hsien-Hsin Chou, Prof. Dr.  Jiann T. Lin and Da-Jong Yin

      Version of Record online: 28 APR 2011 | DOI: 10.1002/chem.201100188

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      The dyeing of the light: Ruthenium dyes have been synthesized with an ancillary bipyridine ligand tethered with hydrocarbon chains. Dye-sensitized solar cells (DSSCs) based on the sensitizer YS-3 (see figure) gave a high conversion efficiency of 6.91 %, which surpassed that of Z907-based (6.36 %) and was comparable to that of N719-based (7.13 %) DSSCs.

    19. Protein Structures

      Amino Acids with Hydrogen-Bonding Side Chains have an Intrinsic Tendency to Sample Various Turn Conformations in Aqueous Solution (pages 6789–6797)

      Dr. Andrew Hagarman, Daniel Mathieu, Siobhan Toal, Dr. Thomas J. Measey, Prof. Harald Schwalbe and Prof. Reinhard Schweitzer-Stenner

      Version of Record online: 5 MAY 2011 | DOI: 10.1002/chem.201100016

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      Know when to fold: The intrinsic propensity of amino acids to adopt elements of secondary structure is vital in the absence of long-range interactions in the earliest stages of protein folding. Polar residues were demonstrated to have an intrinsic tendency to adopt dihedral angles found predominantly in turn motifs (see figure). These results demonstrate that the high occurrence of polar residues in turns reflects an intrinsic property.

    20. Heterocycles

      Coarctate versus Pericyclic Reactivity in Naphthalene-Fused Azo–Ene–Ynes: Synthesis of Benzocinnolines and Benzoisoindazoles (pages 6798–6806)

      Dr. Sean P. McClintock, Dr. Lev N. Zakharov, Prof. Dr. Rainer Herges and Prof. Dr. Michael M. Haley

      Version of Record online: 3 MAY 2011 | DOI: 10.1002/chem.201002936

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      Made-to-measure cycles: A series of naphthalene-fused azo–ene–yne structures were synthesized and cyclized to afford benzocinnolines and benzoisoindazoles. Computational analysis reveals that fusing a second benzene ring in a linear fashion (B) has a negligible effect on the cyclization energies. Affixing the second benzene in an angular orientation (A or C) leads to lower energy pathways computationally, and interesting dimeric structures experimentally.

    21. Spin Crossover

      On the Role of Intermolecular Interactions on Structural and Spin-Crossover Properties of 2D Coordination Networks [Fe(bbtr)3]A2 (bbtr=1,4-bis(1,2,3-triazol-1-yl)butane; A=ClO4, BF4) (pages 6807–6820)

      Prof. Dr. Joachim Kusz, Dr. Robert Bronisz, Maciej Zubko and Gabriela Bednarek

      Version of Record online: 5 MAY 2011 | DOI: 10.1002/chem.201100394

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      A structural phase transition (space group Pequation imagePequation image) occurs in [Fe(bbtr)3](ClO4)2 (bbtr=1,4-bis(1,2,3-triazol-1-yl)butane), which undergoes high spin (HS)⇄low spin (LS) spin crossover (SCO), whereas its BF4 analogue remains in the HS form in the whole temperature range of 5–300 K. Studies on [FexZn1−x(bbtr)3](ClO4)2 systems revealed that introduction of ZnII ions into an FeII matrix increases the separation between the phase-transition (Tstruct) and spin-transition (T1/2) temperatures (see picture).

    22. Organic Electronics

      Rodlike Macromolecules through Spatial Overlapping of Thiophene Dendrons (pages 6821–6829)

      Prof. Mutsumi Kimura, Akiko Kitao, Tadashi Fukawa and Prof. Hirofusa Shirai

      Version of Record online: 5 MAY 2011 | DOI: 10.1002/chem.201003627

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      They're electroactive: Dendronized polymers containing thiophene dendrons as a pendant group were synthesized. The absorption, fluorescence, and electrochemical changes in solution revealed that the linkage of dendrons with a polymer backbone leads to spatial overlapping of the thiophene dendrons (see scheme). The photophysical and redox behaviors of the dendronized polymers were investigated.

    23. NMR Spectroscopy

      4,4′-Dithiobisdipicolinic Acid: A Small and Convenient Lanthanide Binding Tag for Protein NMR Spectroscopy (pages 6830–6836)

      Dr. Xinying Jia, Ansis Maleckis, Dr. Thomas Huber and Prof. Gottfried Otting

      Version of Record online: 3 MAY 2011 | DOI: 10.1002/chem.201003573

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      Novel protein tag: The disulfide dimer of 4-mercaptodipicolinic acid (4MDPA) presents a new and convenient reagent for selective derivatisation of cysteine residues to generate lanthanide binding sites in proteins (see figure). 4MDPA is a small and rigid tag capable of producing significant pseudocontact shifts also without additional coordination of the lanthanide. This makes it a powerful tool for structural biology by NMR spectroscopy.

    24. Ionic Liquids

      Layered Structure of Room-Temperature Ionic Liquids in Microemulsions by Multinuclear NMR Spectroscopic Studies (pages 6837–6846)

      Dr. R. Dario Falcone, Dr. Bharat Baruah, Dr. Ernestas Gaidamauskas, Dr. Christopher D. Rithner, Dr. N. Mariano Correa, Prof. Juana J. Silber, Prof. Debbie C. Crans and Prof. Nancy E. Levinger

      Version of Record online: 6 MAY 2011 | DOI: 10.1002/chem.201002182

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      Confining ions: Multinuclear NMR experiments were used to explore two different reverse micelle systems formed by using a cationic and nonionic surfactant with the room-temperature ionic liquid (RTIL) [bmim][BF4] (bmim=1-butyl-3-methylimidazolium) as the polar phase. Microemulsions formed by using a cationic surfactant revealed layering of the RTIL that does not occur in systems formed with the nonionic surfactant (see figure).

    25. Main Group Polycations

      [Sb10Se10]2+, a Heteronuclear Polycyclic Polycation from a Room-Temperature Ionic Liquid (pages 6847–6852)

      Ejaz Ahmed , Dr. Anna Isaeva, Andy Fiedler, Marcel Haft and Prof. Dr. Michael Ruck 

      Version of Record online: 5 MAY 2011 | DOI: 10.1002/chem.201100398

      Thumbnail image of graphical abstract

      Two realgar-type [Sb4Se4] cages are connected by an [Sb2Se2] ring in the first Sb/Se heteronuclear polycation, [Sb10Se10]2+ (see picture), which was obtained in a Lewis acidic ionic liquid at room temperature. Quantum chemical calculations indicate primarily covalent bonding with varying ionic contribution within the polycation.

    26. Heterometallic Complexes

      Multistep Oligometal Complexation of the Macrocyclic Tris(N2O2) Hexaoxime Ligand (pages 6853–6861)

      Dr. Shigehisa Akine, Shuichi Sunaga and Prof. Dr. Tatsuya Nabeshima

      Version of Record online: 3 MAY 2011 | DOI: 10.1002/chem.201100122

      Thumbnail image of graphical abstract

      Three at a time: A macrocyclic oxime ligand (H6L) undergoes two-step oligometal complexation. The reaction with zinc(II) afforded two kinds of hexanuclear complexes, L2Zn6 then LZn6, with a unique oligonuclear structure (see picture). Heterometallic complexes LZn3M (M=Ca, Ba, La, Eu, Lu) were obtained. The apparent binding affinity in the central O6 site is in the order of Ca2+, Ba2+<Zn33-OH)<La3+.

    27. Cytochromes

      Dearomatisation of o-Xylene by P450BM3 (CYP102A1) (pages 6862–6868)

      Dr. Christopher J. C. Whitehouse, Dr. Nicholas H. Rees, Dr. Stephen G. Bell and Dr. Luet-Lok Wong

      Version of Record online: 26 APR 2011 | DOI: 10.1002/chem.201002465

      Thumbnail image of graphical abstract

      Migration of a methyl group leads to the generation of products not formed by microsomal cytochrome P450s in the oxidation of o-xylene by P450BM3 (CYP102A1), including a dienone (see figure). m-Xylene gives substantially lower benzylic hydroxylation percentages than o-xylene. Variants with enlarged active sites give product profiles similar to microsomal P450s with both xylene isomers.

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      Preview: Chem. Eur. J. 25/2011 (page 6871)

      Version of Record online: 26 MAY 2011 | DOI: 10.1002/chem.201190124

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