ChemPhysChem

Cover image for Vol. 5 Issue 7

July 19, 2004

Volume 5, Issue 7

Pages 913–1070

    1. Cover Picture: Morphology and Nanomechanics of Conducting Plastic Crystals (ChemPhysChem 7/2004) (page 913)

      Maritza Volel, Pierre-Jean Alarco, Yaser Abu-Lebdeh and Michel Armand

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200490039

      The cover picture shows weakly interacting anions and cations in ionic plastic crystals that are free to rotate in a spherical symmetry and give rise to multiple subphases, as seen by AFM. Here, the compact shape of the cation, which is favourable for the tumbling motion, has been designed by fusing a second carbocycle to a pyrazole ring. For more information read the Article by Armand et al. on p. 1027.

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    4. Type H Superconductors and the Vortex Lattice (pages 924–929)

      Alexei A. Abrikosov

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200400138

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      Super work: The picture shows the lines of current that coincide with the constant lines for a square lattice in a type II superconductor. The author's work on superconduction in liquid helium established the existence of type II superconductors and proved that vortex lattices exist in superfluid helium, in the presence of magnetic fields. The theories he developed are the basis for much current research, and he was awarded the Nobel prize in 2003.

    5. On Superconductivity and Superfluidity (What I Have and Have Not Managed to Do), as well as on the ‘Physical Minimum’ at the Beginning of the 21st Century (pages 930–945)

      Vitaly L. Ginzburg

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200400182

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      Superconducting in theory: Together with his colleague L. D. Landau, V. L. Ginzburg developed a phenomenological theory of superconductivity in the late 1940s. This theory proposes that those electrons that contribute to superconduction form a superfluid. The superconductor is described by a complex function Ψ, called the order parameter (see equation), and |Ψ|2 indicates the fraction of electrons that has condensed into a superfluid.

    6. 2003 Nobel Prize in Physics for Theoretical Work on Superfluid 3He (pages 946–958)

      Anthony J. Leggett

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200400134

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      Complex detective tale is how the author and Nobel prizewinner Anthony Leggett describes the story of how, in roughly the twelve-month period July 1972–July 1973, he and others came to a theoretical understanding of the experimental data of what we now know as superfluid 3He. The graphic shows a comparison of ferromagnetic and “spontaneously broken spin-orbit symmetry” in liquid helium.

    7. Direct Measurement of Dynamic Frequency Shift Induced by Cross-Correlations in 15N-Enriched Proteins (pages 959–965)

      Hervé Desvaux, Rainer Kümmerle, Jozef Kowalewski, Claudio Luchinat and Ivano Bertini

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200301034

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      Direct determination of the dynamic frequency shift induced by chemical shift anisotropy/dipolar interaction cross-correlations in 15N-enriched proteins is presented in a new NMR experimental scheme. Its principle consists of comparing two rates of polarisation transfer between the amide proton and nitrogen atom. The dynamic frequency shift induced by cross-correlation is equal to the difference in cross-polarisation frequencies between N and H in the presence (red) and in the absence (blue) of radiofrequency irradiation.

    8. Two-Dimensional Double-Quantum 2H NMR Spectroscopy in the Solid State under OMAS Conditions: Correlating 2H Chemical Shifts with Quasistatic Line Shapes (pages 966–974)

      Anke Hoffmann and Ingo Schnell

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200301215

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      A new dimension: A new two-dimensional 2H double-quantum (DQ) experiment is performed under fast magic-angle spinning with a slight offset of the magic angle (OMAS) to combine 2H chemical-shift resolution with DQ-filtered quasistatic 2H line shapes. In this way, it is possible to separate 2H resonances and to independently determine 2H quadrupole couplings at multiple sites (see spectrum). While 2H chemical shifts are resolved in the 2H DQ dimension, the quadrupole parameters can be obtained from characteristic line shapes which are reintroduced in the second dimension by the magic-angle offset.

    9. On the Bond-Stretch Isomerism in the Benzo[1,2:4,5]dicyclobutadiene System—An ab initio MR-AQCC Study (pages 975–981)

      Ivana Antol, Mirjana Eckert-Maksić, Hans Lischka and Zvonimir B. Maksić

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200301016

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      On a quest for highly elusive bond-stretch isomers. Do bond-stretch isomers exist? Available experimental and theoretical evidence is either unconvincing or offers arguments against their existence. The present high level MR-AQCC/6–31G(d) calculations strongly indicate that two forms of benzo[1,2:4,5]dicyclobutadiene (see graphic) are separated by a barrier of 5 kcal mol−1 and differ only in several C–C bond lengths, thus providing in principle an example par excellence for bond-stretch isomers.

    10. Two-Photon Absorption in Linear Bis-dioxaborine Compounds—The Impact of Correlation-Induced Oscillator-Strength Redistribution (pages 982–988)

      Egbert Zojer, Wim Wenseleers, Marcus Halik, Cara Grasso, Stephen Barlow, Joseph W. Perry, Seth R. Marder and Jean-Luc Brédas

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200301023

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      Unprecedented predictions: Increasing the two-photon absorption (TPA) properties of π-conjugated chromophores by acceptor and/or donor substitution is a frequently adopted strategy (see graphic). The authors use theoretical and experimental studies to provide an in-depth understanding of the underlying quantum-mechanical effects. The presented results imply that a tuning of the redistribution of oscillator strength by electron-correlation could allow TPA cross-sections of unprecedented magnitude.

    11. Scanning Force Microscopy Based Rapid Force Curve Acquisition on Supported Lipid Bilayers: Experiments and Simulations Using Pulsed Force Mode (pages 989–997)

      Stephanie Krüger, Daniel Krüger and Andreas Janshoff

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200301059

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      Mapping elastic properties of phase-separated lipid bilayers by pulsed force mode microscopy (see graphic) is investigated by computer simulations and experiments. The impact of crucial parameters, such as driving frequency and amplitude, on the observed stiffness and adhesion contrast is discussed.

    12. Surfactant-Directed Polypyrrole/CNT Nanocables: Synthesis, Characterization, and Enhanced Electrical Properties (pages 998–1002)

      Xuetong Zhang, Jin Zhang, Rongming Wang, Tao Zhu and Zhongfan Liu

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200301217

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      Electric cables: Carbon-nanotube-cored nanocables were obtained by polymerizing pyrrole in the presence of surfactant-stabilized aqueous dispersions of carbon nanotubes followed by removal of the surfactant. The nanocables show enhanced electrical properties; a negative temperature coefficient of resistance at 77–300 K and negative magnetoresistance at 10–200 K were observed. The picture shows nanocables obtained in the presence of the cationic surfactant cetyltrimethylammonium bromide.

    13. Amorphous Silica as a Versatile Supermolecular Ligand for NiII Amine Complexes: Toward Interfacial Molecular Recognition (pages 1003–1013)

      Souhir Boujday, Jean-François Lambert and Michel Che

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200400008

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      The nature of silica adsorption sites was probed with Ni complexes. The silica surface acts as a mono- or polydentate ligand that substitutes aqua ligands of the NiII complexes. Each nickel complex selects a limited number of adsorption sites, and different sites are recognised by the three complexes. The specific sites involve silanol/silanolate groups and other surface groups that probably act as hydrogen-bond acceptors, as shown for [Ni(dien)(H2O)3]2+ (A=hydrogen-bond acceptor).

    14. Microsolvation of Phthalocyanines in Superfluid Helium Droplets (pages 1014–1019)

      Rudolf Lehnig and Alkwin Slenczka

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200400022

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      First layer determines spectrum: The emission spectra of Mg-phthalocyanine and of phthalocyanine–argon clusters in helium droplets are presented. A scheme of levels (shown) is deduced from the emission spectra and attributed to quantized states of the first helium layer surrounding the dopant molecule.

    15. Photochromism of Novel Molybdate/Alkylamine Composite Thin Films (pages 1020–1026)

      Zhaohui Chen, Boon H. Loo, Ying Ma, Yunwei Cao, Amin Ibrahim and Jiannian Yao

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200400041

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      Pushing to longer wavelengths: Photochromic inorganic/organic thin films consisting of polyoxomolybdate and alkylammonium ions have been fabricated by a self-assembly process. Characterization of the films reveals a lamellar nature. Proton transfer between the alkylammonium ions and the MoO6 octahedra is suggested to be responsible for the photochromic behavior (see graphic) centered around 472 nm, a longer wavelength than normally accessible with transition-metal thin films.

    16. Morphology and Nanomechanics of Conducting Plastic Crystals (pages 1027–1033)

      Maritza Volel, Pierre-Jean Alarco, Yaser Abu-Lebdeh and Michel Armand

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200400070

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      Probing plastics: The authors present a temperature-controlled AFM characterisation of the morphology and mechanical properties of conducting N,N′-cyclized pyrazolium trifluoromethanesulfonimide plastic crystalline salts (see picture) around their phase transitions.

    17. Evaporation of Water Microdroplets on Self-Assembled Monolayers: From Pinning to Shrinking (pages 1035–1038)

      Hua-Zhong Yu, Dinah M. Soolaman, Aaron W. Rowe and Jeffrey T. Banks

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200301042

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      The great escape: Mixed ω-terminated self-assembled monolayers (SAMs) were explored as model surfaces to understand fundamental aspects of liquid evaporation phenomena on solids. The authors demonstrate that on these SAMs the evaporation of water microdroplets follows an exclusive trend. Despite the different wettabilities of the surfaces, the evaporation of water microdroplets switches from a constant contact area (“pinning”) to a constant contact angle mode (“shrinking”).

    18. Generation and Spectroscopic Characterization of Methylnitrene Diradicals Adsorbed on the Cu(110) Surface (pages 1038–1041)

      Run-Sheng Zhai, Yuet Loy Chan, Chien-Kui Hsu, Ping Chuang, Ruth Klauser and Tung J. Chuang

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200400012

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      Important radical: A novel method to generate pure methylnitrene radicals on copper surfaces and their characterization by ultraviolet photoemission (see spectrum), vibrational spectroscopy and thermal desorption mass spectrometry are presented. The radical may play an essential role in various heterogeneous reactions.

    19. System-Size Biresonance for Intracellular Calcium Signaling (pages 1041–1045)

      Jiqian Zhang, Zhonghuai Hou and Houwen Xin

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200400089

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      Using the chemical Langevin equation, the authors have addressed the effects of internal fluctuations on intracellular calcium signaling. It is found that the effect of the internal fluctuations depends on the volume of the cell. The signal-to-noise ratio (SNR; see plot) of the stochastic calcium oscillation shows two maxima, demonstrating the occurrence of system-size biresonance. Most importantly, the first resonance matches the size of real living cells.

    20. Pseudorotation of Natural and Chemically Modified Biological Phosphoranes: Implications for RNA Catalysis (pages 1045–1049)

      Carlos Silva López, Olalla Nieto Faza, Brent A. Gregersen, Xabier Lopez, Angel R. de Lera and Darrin M. York

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200400091

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      Model intermediates: Catalytic mechanisms of RNA transphosphorylation are investigated by monitoring changes in the reaction rate that occur upon substitution of key phosphate oxygen atoms with sulfur atoms. The mechanisms and barriers to pseudorotation for a series of oxyphosphorane and thiophosphorane molecules are presented (see picture). Theoretical models provide detailed insight into biological phosphorous reactivity in RNA systems.

    21. Molecular Simulation Study of Interactions of Carbon Dioxide and Water with Ionic Liquids (pages 1049–1052)

      Johnny Deschamps, Margarida F. Costa Gomes and Agílio A. H. Pádua

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200400097

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      Simulating solubilities in green solvents: Molecular simulations have been used to predict qualitatively the solubility of several small molecules (see picture) in imidazolium-based ionic liquids.

    22. Resolving Rotational Spectra of Hydrogen Adsorbed on a Single-Walled Carbon Nanotube Substrate (pages 1053–1055)

      H. Gijs Schimmel, Gordon J. Kearley and Fokko M. Mulder

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200400109

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      In the groove: Hydrogen molecules adsorbed on single-walled carbon nanotube substrates have been studied using neutron rotational spectroscopy. Hydrogen first occupies the grooves between aligned tubes, then the surface becomes covered, and eventually more than one monolayer is formed (see graphic).

    23. The Impact of Phase Changes, Alloying and Segregation in Supported RhPd Catalysts during Selective NO Reduction by H2 (pages 1056–1058)

      Mark A. Newton, Bhrat Jyoti, Andrew J. Dent, Sofia Diaz-Moreno, Steven G. Fiddy and John Evans

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200400204

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      Illuminating complexity: Time-resolved, microreactor-based, EDE/mass spectrometry (EDE=energy dispersive extended X-ray absorption fine structure) was used to probe the behaviour of both Rh and Pd components of alloyed nanoparticles during NO reduction by H2. The picture shows the NO conversion as a function of temperature. This surface enrichment in Pd is shown to curtail rapid oxidation of the Rh component by NO and leads to a promotion of NO reduction.

    24. Photochemistry of Charge-Transfer Complexes in a Viologen Periodic Mesoporous Organosilica: Time Evolution from Femtoseconds to Minutes (pages 1058–1062)

      Mercedes Álvaro, Belén Ferrer, Hermenegildo García, Shuichi Hashimoto, Masahiro Hiratsuka, Tsuyoshi Asahi and Hiroshi Masuhara

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200301038

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      Persistent radical cations can be generated in V∝PMO, a periodic mesoporous organosilica incorporating a viologen in its silicate framework. Photoexcitation of V∝PMO forms a geminate viologen–halide ion pair that can undergo rapid charge recombination or electron hopping to form the nongeminate ion pair, which persists for minutes (see picture). In contrast, viologen–halide CT complexes in solution undergo complete charge recombination on the sub-nanosecond timescale.

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      Preview: ChemPhysChem 7/2004 (page 1070)

      Version of Record online: 16 JUL 2004 | DOI: 10.1002/cphc.200490038

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