ChemPhysChem

Cover image for ChemPhysChem

September 15, 2003

Volume 4, Issue 9

Pages 901–1030

    1. Cover Picture: Molecular Spin Clusters: New Synthetic Approaches and Neutron Scattering Studies (ChemPhysChem 9/2003) (page 901)

      Reto Basler, Colette Boskovic, Grégory Chaboussant, Hans U. Güdel, Mark Murrie, Stefan T. Ochsenbein and Andreas Sieber

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200390104

    2. Graphical Abstract: ChemPhysChem 9/2003 (pages 903–909)

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200390105

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      Freely Suspended Actin Cortex Models on Arrays of Microfabricated Pillars (page 908)

      Wouter H. Roos, Alexander Roth, Johannes Konle, Hartmut Presting, Erich Sackmann and Joachim P. Spatz

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200390106

    4. Molecular Spin Clusters: New Synthetic Approaches and Neutron Scattering Studies (pages 910–926)

      Reto Basler, Colette Boskovic, Grégory Chaboussant, Hans U. Güdel, Mark Murrie, Stefan T. Ochsenbein and Andreas Sieber

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200300689

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      In a spin.The structure and properties of molecular spin clusters and single-molecule magnets is an exciting field of interdisciplinary research, which covers experiment and theory, physics and chemistry, as well as materials sciences. The review focuses on the determination of exchange and anisotropy parameters of molecular clusters using inelastic neutron scattering (INS), and upon the magnetic properties of some interesting new clusters. The figure shows INS spectra of [Mn4O3X(OAc)3(dbm)3] (X=Cl, Br, OAc) at 18 K obtained with a time-of-flight spectrometer.

    5. Atomic Resolution of Oxygen in Solid Oxides by Electron Microscopy: What Next? (pages 927–929)

      John Meurig Thomas and Wuzong Zhou

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200300772

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      Atomic resolution: the final frontier? This highlight outlines the remarkable recent advances in transmission electron microscopy (TEM) that have enabled the observation of light elements, and in particular of oxygen (see graphic). Will the boundaries of TEM technology keep being pushed back, or have its limits been reached?

    6. New Insights into the Jahn–Teller Effect through ab initio Quantum-Mechanical/Molecular-Mechanical Molecular Dynamics Simulations of CuII in Water (pages 931–943)

      Christian F. Schwenk and Bernd M. Rode

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200300659

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      What's in the shell? The CuII hydration shell structure has been studied by using classical molecular dynamics (MD) simulations. The copper(II) ion is found to be six-fold coordinated and [Cu(H2O)6]2+ exhibits a distorted octahedral structure. The quantum mechanics/molecular mechanics MD approach reproduces correctly the experimentally observed Jahn–Teller effect but exhibits faster inversions (<200 fs) and a more complex behaviour than expected from experimental data (see graphic for a comparison of the radial distribution functions).

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      Ionic Liquid for in situ Vis/NIR and Raman Spectroelectrochemistry: Doping of Carbon Nanostructures (pages 944–950)

      Ladislav Kavan and Lothar Dunsch

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200300692

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      Doped peapods. Single-walled carbon nanotubes (SWCNT) and fullerene peapods (C60@SWCNT) were doped electrochemically in 1-butyl-3-methylimidazolium tetrafluoroborate (see graphic). In situ Vis/NIR and Raman spectra demonstrate the charging-induced changes of transitions between Van Hove singularities, which occurred in a broad window of electrochemical potentials. The Raman spectrum of fullerene C60 in C60@SWCNT exhibits considerable intensity increase upon anodic doping of peapods.

    8. Time-Resolved Spectroscopic Study on Photoinduced Electron-Transfer Processes in Zn(II)porphyrin–Zn(II)chlorin–Fullerene Triad (pages 951–958)

      Jeong-Hyon Ha, Hyun Sun Cho, Dongho Kim, Jong-Cheol Lee, Tae-Young Kim and Young Key Shim

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200300695

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      Capturing light: Femtosecond time-resolved transient absorption studies have been performed to investigate the photoinduced energy and electron-transfer processes in the Zn(II)porphyrin–Zn(II)chlorin–fullerene triad shown here in which energy and oxidation potential gradients are directed along the donor–acceptor-linked arrays.

    9. Long-Range Transport in an Assembly of ZnO Quantum Dots: The Effects of Quantum Confinement, Coulomb Repulsion and Structural Disorder (pages 959–966)

      Aarnoud L. Roest, Alexander Germeau, John J. Kelly, Daniël Vanmaekelbergh, Guy Allan and Eric A. Meulenkamp

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200300696

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      Building new materials with quantum dots: In assemblies of ZnO quantum dots permeated with an electrolyte solution, the quantum properties of the individual building-blocks are preserved. Transport of the electrons occurs via tunneling between the atom-like conduction energy levels (see picture). The Coulomb interaction between the free electrons depends on the interpenetrating solution.

    10. Crosslinked Copolyimide Membranes for Phenol Recovery from Process Water by Pervaporation (pages 967–973)

      Frankie Pithan and Claudia Staudt-Bickel

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200300707

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      Polyimides clean up: A study on the effectiveness of copolyimide membranes (graphic shows the monomers) for the recovery of phenol from process water by pervaporation is presented. The influence that crosslinking and fluorine content have on the effectiveness of the membranes is discussed. A comparison with rubbery membrane materials is also given.

    11. Electrochemical Studies of Vitamin K1 Microdroplets: Electrocatalytic Hydrogen Evolution (pages 974–982)

      Andrew J. Wain, Jay D. Wadhawan and Richard G. Compton

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200300765

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      Fizzy drops. Vitamin K1 microdroplets are immobilised on the surface of a basal-plane pyrolytic graphite electrode and their redox processes monitored in the presence of aqueous electrolytes. In acidic or strongly alkaline solutions, electrochemical processes occur at the triple-phase junction (see graphic), but addition of alkali-metal cations to the aqueous acidic solution leads to electrocatalytic formation of molecular hydrogen within the microdroplets.

    12. Electroluminescent Diodes from Complementary Discotic Benzoperylenes (pages 983–985)

      Sonia Alibert-Fouet, Sebastien Dardel, Harald Bock, Mimoun Oukachmih, Samuel Archambeau, Isabelle Seguy, Pascale Jolinat and Pierre Destruel

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200300734

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      Unequal brothers: Benzoperylene carboxylic acid derivatives with flexible chains not only form charge-transporting columnar liquid crystals (see graphic), their charge-transport properties can also be tuned to be either of n- or of p-type: relatively minor changes in the substitution pattern yield different materials that are complementary enough to form red-fluorescent charge-transfer complexes and pn junction electronic devices.

    13. Probing Solid Surfaces with Single Polymers (pages 986–990)

      Markus Seitz, Claudia Friedsam, Willi Jöstl, Thorsten Hugel and Hermann E. Gaub

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200300760

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      Coming unstuck: Adhesion and desorption forces of single polymer chains on solid substrates can be measured with the atomic force microscope, shown here for polyvinylamine and polyacrylic acid on the minerals mica and calcite.

    14. The One-Photon and Two-Photon Absorption Properties for Porphyrin-Derived Monomers and Dimers (pages 991–997)

      Xin Zhou, Ai-Min Ren, Ji-Kang Feng, Xiao-Juan Liu and Yun-Dong Zhang

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200300767

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      Theoretically brilliant. Monomers and dimers of porphyrin polymers (see, for example, the graphic) as novel two-photon absorption materials have been theoretically investigated by means of density functional theory B3 LYP/6-31G level and the semiempirical ZINDO-SOS method. It is found that the conjugation length plays a most crucial role for large two-photon absorption response, which results in the increase of the two-photon cross-section by two orders of magnitude. The largest two-photon absorption cross-section calculated is 7.6×10−46 cm4 s photon−1, which is in agreement with experimental observations.

    15. On the Covalency of Silver–Fluorine Bonds in Compounds of Silver(I), Silver(II) and Silver(III) (pages 997–1001)

      Wojciech Grochala, Russ G. Egdell, Peter P. Edwards, Zoran Mazej and Boris Žemva

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200300777

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      Unconventional covalence: For the higher silver fluorides the silver–fluorine chemical bonding is significantly covalent, in contrast to the conventional “ionic” picture most frequently used in the chemistry of inorganic fluorides. For KAgF4, an Ag(III) fluoride, the Ag(4d) states (see picture) are more within the “ligand band” (60 %) than within the “metal band” (40 %) reflecting significant covalency of the Ag[BOND]F bond, and an electronic band with significant hole production within the anionic F(2p) states.

    16. Polarization-Dependent Surface-Enhanced Raman Spectroscopy of Isolated Silver Nanoaggregates (pages 1001–1005)

      Hongxing Xu and Mikael Käll

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200200544

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      Ultrasensitive to nanogaps: Raman scattering from pairs of silver nanoparticles bound together by hemoglobin varies strongly with incident polarization. Experiments and electrodynamic calculations (see graphic) show that only that part of the incident field that is polarized parallel to the dimer axis generates intense surface-enhanced Raman scattering (SERS). The results support the idea that nanogaps between particles are a key ingredient of ultrasensitive SERS analysis.

    17. Maximum-Likelihood Approach to Single-Molecule Polarization Modulation Analysis (pages 1005–1011)

      Kenneth D. Osborn, Manoj K. Singh, Ramona J. Bieber Urbauer and Carey K. Johnson

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200300677

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      Mobile or not mobile? Polarization modulation has been used to probe single-molecule dynamic heterogeneity of dye molecules that are either surface-bound or incorporated in the biological system calmodulin–plasma membrane calcium ATPase. A maximum-likelihood approach was applied to determine modulation depth and phase shift of the fluorescence trajectories (see picture), which give a measure of the orientational mobility of the molecules.

    18. Gas-Phase Reactivity of Uracil, 2-Thiouracil, 4-Thiouracil, and 2,4-Dithiouracil towards the Cu+ Cation: A DFT Study (pages 1011–1016)

      Al Mokhtar Lamsabhi, Manuel Alcamí, Otilia Mó and Manuel Yáñez

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200300704

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      80 Cu+–(thio)uracil structures were investigated by DFT calculations, which, with the exception of 2-thiouracil, showed that attachment of the Cu+ cation occurs initially at the heteroatom at position 4. For uracil–Cu+, 2-thiouracil–Cu+, and 2,4-dithiouracil–Cu+ in the global minimum the Cu+ cation bridges the heteroatom at position 2 and an adjacent amino group of the corresponding enolic tautomer. Isomerization processes leading from the most stable adduct to the global minimum (shown for 2-thiouracil in the picture, with energies in kJ mol−1) and to other stable conformers were also investigated.

    19. Tunable Surface Oxidation States in Si/SiO2 Nanostructures Prepared from Si/SiO2 Mixtures and Phenol Hydroxylation Activity (pages 1016–1021)

      James L. Gole, Brian D. Shinall, Alexei V. Iretskii, Mark G. White, W. Brent Carter and Ann S. Erickson

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200300719

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      Active spheres: Nearly monodisperse Si/SiO2 nanospheres (see graphic) with a tunable silicon-to-oxygen ratio have been synthesized and analyzed with respect to their average Si oxidation states. The metalloid oxides are synthesized in a two-step generalizable process in the absence of liquid solvents, which is an environmentally friendly method for preparation of an adsorbent and catalyst with an activity much higher than that of fumed silica in the phenol hydroxylation reaction.

    20. Local Formation of an Alloy by Atomic Contact between the STM Tip and the Substrate Surface (pages 1022–1024)

      Michael Nielinger and Helmut Baltruschat

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200300820

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      Tip-induced nanostructuring: Scanning with a STM tip very close to an electrode surface covered by a copper or palladium monolayer leads to a local alloy formation (see picture). The measurement of the tunneling resistance indicates that a point contact between the STM tip and electrode surface is sufficient for the alloying process.

    21. Book Review: Valence Bond Methods—Theory and Applications. By Gordon A. Gallup (page 1027)

      F. Matthias Bickelhaupt

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200390102

    22. Preview: ChemPhysChem 9/2003 (page 1030)

      Article first published online: 10 SEP 2003 | DOI: 10.1002/cphc.200390103

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