Cover image for Vol. 6 Issue 6

June 13, 2005

Volume 6, Issue 6

Pages 1001–1190

    1. Cover Picture: Energy Transfer in Single Hydrogen-Bonded Water Molecules (ChemPhysChem 6/2005) (page 1001)

      Huib J. Bakker, Joop J. Gilijamse and Anjan J. Lock

      Version of Record online: 8 JUN 2005 | DOI: 10.1002/cphc.200590009

      The cover picture shows a single water molecule that is hydrogen-bonded (thin blue lines) to two neigboring acetone molecules. Water can enter an apolar solvent such as CCl4 if it is embedded by amphiphilic acetone molecules. In their Article on page 1146 Bakker et al. show by femtosecond mid-infrared spectroscopy that the water molecules enter the apolar matrix in the form of particularly hydrogen-bonded complexes with acetone. The O[BOND]H stretching vibrations of the water molecule have been excited by an infrared laser pulse. Because the O[BOND]H vibrations of the water molecule are in resonance, the vibration is delocalized over the molecule.

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      Energy–Entropy Compensation in the Transfer of Nonpolar Solutes from Water to Cosolvent/Water Mixtures (page 1010)

      Nico F. A. van der Vegt, Daniel Trzesniak, Besnik Kasumaj and Wilfred F. van Gunsteren

      Version of Record online: 8 JUN 2005 | DOI: 10.1002/cphc.200590011

    3. Microstorms in Cellular Polymers: A Route to Soft Piezoelectric Transducer Materials with Engineered Macroscopic Dipoles (pages 1014–1025)

      Michael Wegener and Siegfried Bauer

      Version of Record online: 11 MAY 2005 | DOI: 10.1002/cphc.200400517

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      Electric storms: Cellular polymers can be internally charged within the voids to give microdischarges accompanied by flashes of visible light, or “microstorms” (see blue image). The soft foams form ferroelectrets, which are strongly piezoelectric and useful, in a wide range of applications, as transducers. The micrograph (red image) shows a cellular polypropylene film. This Review details the preparation, characterization, and applications of such closed-cell foams.

    4. Mesoscopic Structures of Maghemite Nanocrystals: Fabrication, Magnetic Properties, and Uses (pages 1027–1034)

      Marie-Paule Pileni and Anh-Tu Ngo

      Version of Record online: 10 MAY 2005 | DOI: 10.1002/cphc.200400574

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      Organized nanocrystals: The coatings on maghemite (γ-Fe2O3) nanocrystals affect their self-organization into mesoscopic structures in the presence of a magnetic field. Van der Waals and dipolar interactions and the shapes of the nanocrystals are responsible for their collective magnetic response. Spherical γ-Fe2O3 nanocrystals (see image; dodecanoic acid coating) can be used as a mask to reproduce the mesostructure on a silicon wafer.

    5. An Electrochemical and ESR Spectroscopic Study on the Molecular Dynamics of TEMPO in Room Temperature Ionic Liquid Solvents (pages 1035–1039)

      Russell G. Evans, Andrew J. Wain, Christopher Hardacre and Richard G. Compton

      Version of Record online: 4 MAY 2005 | DOI: 10.1002/cphc.200500157

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      Slow rotational diffusion of probe molecule TEMPO in several room temperature ionic liquid solvents results in asymmetry in its ESR spectrum (see figure), the severity of which depends on the temperature. In some cases the observed variation may be rationalised using simple hydrodynamic theories, while in others it points to an increased level of ordering within the liquid structure (TEMPO: 2,2,6,6-tetramethylpiperidine-N-oxyl).

    6. Weak Backscattering in Deflected Doped Carbon Nanotubes (pages 1040–1042)

      Sheng-Yi Lu and Wen-Kuang Hsu

      Version of Record online: 10 MAY 2005 | DOI: 10.1002/cphc.200500043

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      Deflected nanotubes: The constant bending of boron-doped multiwalled carbon nanotubes (BCNTs; see picture) produces a weak backscattering of the electron transmission, which is due to the fact that the primary conduction in p-doped nanotubes is switched to an “extra” energy level near the valence-band edge and the electron-hopping amplitude at bending 2pz orbitals no longer plays a crucial role in the conduction mechanism.

    7. Optimal Spike Coherence and Synchronization on Complex Hodgkin–Huxley Neuron Networks (pages 1042–1047)

      Yubing Gong, Maosheng Wang, Zhonghuai Hou and Houwen Xin

      Version of Record online: 10 MAY 2005 | DOI: 10.1002/cphc.200500051

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      Optimal random shortcuts for spike coherence: Sixty stochastic Hodgkin-Huxley neurons on complex networks, each driven by a subthreshold sinusoidal current, are considered. If the neurons are regularly connected to each other, the temporal response is bad. With increasing number of random shortcuts, the temporal response improves and reaches an intermediate value when the spatial synchronization is already good (see picture).

    8. Stepwise Shrinkage of Liposomes Driven by Thermal Fluctuations of the Membranes (pages 1047–1050)

      Tamiki Umeda, Fumimasa Nomura, Takehiko Inaba, Kingo Takiguchi and Hirokazu Hotani

      Version of Record online: 10 MAY 2005 | DOI: 10.1002/cphc.200400519

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      Fourier analysis of the microscopic images of a shrinking liposome in the presence of detergents shows that the radius drops in a stepwise fashion (see figure) while the membrane fluctuations expand intermittently. Periodical opening of membrane holes and the thermal fluctuations of the membrane quantitatively explain this dynamic behavior of solubilizing vesicles.

    9. Percolating Microemulsions of Nonionic Surfactants Probed by Dielectric Spectroscopy (pages 1051–1055)

      Simon Schrödle, Richard Buchner and Werner Kunz

      Version of Record online: 4 MAY 2005 | DOI: 10.1002/cphc.200400605

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      Charge exchange in aggregated micelles: Percolation phenomena in microemulsions of nonionic surfactants (see picture) are investigated by dielectric spectroscopy. For the investigated 10−3M KCl(aq)/n-octane/C12E5 system the conductivity and Cole–Cole parameter follow the predictions of the dynamic percolation theory, whereas the relaxation time and the dispersion amplitude of the characteristic relaxation are specific to the sample composition.

    10. Surface-Structure-Sensitive Adsorption of Adenine on Gold Electrodes (pages 1056–1060)

      Ana Martins, Ana Queirós and Fernando Silva

      Version of Record online: 10 MAY 2005 | DOI: 10.1002/cphc.200400600

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      Attracted to gold: The adsorption and assembly of nucleobases on gold electrodes, as well as the influence of the surface atomic structure of these electrodes on the adsorbed films, were studied by means of cyclic voltametry (see picture) and differential capacitance measurements.

    11. Theoretical and Experimental Study of the Adsorption of Neutral Glycine on Silica from the Gas Phase (pages 1061–1070)

      C. Lomenech, G. Bery, D. Costa, L. Stievano and J. F. Lambert

      Version of Record online: 8 JUN 2005 | DOI: 10.1002/cphc.200400608

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      Support group: DFT calculations suggest that glycine adsorbed on amorphous silica interacts through its COOH end with one or more silanol groups, with the formation of one H-acceptor and one H-donor bond. The experimental and calculated frequencies for the different functional groups of glycine correspond to glycine adsorbed on two vicinal, adjacent silanols (see picture).

    12. Particle Distribution in a Microporous Material: Experiments with Zeolite A (pages 1071–1080)

      Marc Meyer, Claudia Leiggener and Gion Calzaferri

      Version of Record online: 10 MAY 2005 | DOI: 10.1002/cphc.200500049

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      Exchange is no robbery: The thermodynamic quantities of the Ag+ exchange reactions in zeolite A should be revised. In zeolite Na-A the Na+ ion occupying a four-ring position is exchanged first for Ag+, while in zeolite K-A the exchange starts with the six-ring ion. Upon dehydration, only Ag+ ions in the four-ring yield yellow samples. The picture shows dehydrated zeolites Ag+xK+12−x-A with 1) x=2, 2) x=5, 3) x=6.

    13. Synthesis of Poly(ε-lysine)-Grafted Dextrans and Their pH- and Thermosensitive Hydrogelation with Cyclodextrins (pages 1081–1086)

      Hak Soo Choi, Kaori Yamamoto, Tooru Ooya and Nobuhiko Yui

      Version of Record online: 4 MAY 2005 | DOI: 10.1002/cphc.200400598

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      A sensitive hydrogel: Rapid phase transitions in response to pH and temperature (see figure) were achieved in supramolecular hydrogel formation between polycation-grafted dextran copolymer and cyclodextrins. In this system, poly(ε-lysine) was introduced as a linear cationic side chain, which induced highly pH-sensitive phase transitions via inclusion complexation and dissociation with α-cyclodextrin.

    14. Switching Mechanism in Polar Columnar Mesophases Made of Bent-Core Molecules (pages 1087–1093)

      Ewa Gorecka, Nataša Vaupotič, Damian Pociecha, Mojca Čepič and Jozef Mieczkowski

      Version of Record online: 10 MAY 2005 | DOI: 10.1002/cphc.200400623

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      Phases bent on switching: Two competing ferroelectric switching mechanisms in columnar phases of bent molecules under an electric field are reported. The molecules can adjust their dipole moment to the external field either by rotation around their long axes or by rotation on the tilt cone around the layer normal (see picture).

    15. Theoretical Study of the Magnetic Behavior of Ferric Wheels (pages 1094–1099)

      Eliseo Ruiz and Santiago Alvarez

      Version of Record online: 4 MAY 2005 | DOI: 10.1002/cphc.200400477

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      Ferric wheels: A theoretical study has been carried out to obtain the exchange coupling constants of eight ferric wheels. The graphic shows the magnetostructural correlation for such complexes, with the Fe[BOND]O[BOND]Fe angle and the Fe[BOND]O bond distance, in comparison with the results for dinuclear alkoxo-bridged FeIII complexes.

    16. The Influence of Solid-State Molecular Organization on the Reaction Paths of Thiyl Radicals (pages 1100–1107)

      Antonio Faucitano, Armando Buttafava, Mario Mariani and Chryssostomos Chatgilialoglu

      Version of Record online: 10 MAY 2005 | DOI: 10.1002/cphc.200400450

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      Compelling pathways: The reaction of thiyl radicals with thiol affords a high yield of perthiyl radicals in the channels of a clathrate. The perthiyl radical yield becomes negligible, however, in solution chemistry and when the reaction is performed within a polymer matrix containing a random distribution of the reacting centers. The authors explain this difference in yield on the basis of “structure control” by the clathrate, and propose analogous “structure control” in the mechanism of solid “dry” lysozyme (see figure).

    17. Interfacial Langmuir–Blodgett Assembly of Straight and Parallel Aligned Nanoribbons (pages 1108–1113)

      Penglei Chen, Peng Gao, Chuanlang Zhan and Minghua Liu

      Version of Record online: 8 JUN 2005 | DOI: 10.1002/cphc.200400465

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      Ordered nanoribbons: A novel amphiphilic molecule (without a long alkyl chain), 1,3,5-trimesyl-tri-L-glutamic acid hexaester, was spread on a water surface. It formed a stable, ultrathin film with a plateau region in its isotherm. Compressing the film over the plateau region generated long, straight, and parallel three-dimensional nanoribbons (see figure).

    18. Sensing Nitrite through a Pseudoazurin–Nitrite Reductase Electron Transfer Relay (pages 1114–1120)

      Yann Astier, Gerard W. Canters, Jason J. Davis, H. Allen O. Hill, Martin P. Verbeet and Hein J. Wijma

      Version of Record online: 18 MAY 2005 | DOI: 10.1002/cphc.200400384

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      Design of an efficient biosensor: Natural pseudoazurin and ruthenium hexammine are used as electron relay mediators in the generation of an amperometric nitrite sensing system. The pseudoazurin redox centre is able to undergo facile electron transfer at a thiolated hexapeptide-modified gold electrode and exchanges electrons through association with a copper-containing nitrite reductase (CuNiR; the picture shows the hexapeptide–pseudoazurin–CuNiR system).

    19. Degenerate Two-Photon Absorption Spectra in Azoaromatic Compounds (pages 1121–1125)

      Leonardo De Boni, Lino Misoguti, Sergio C. Zílio and Cleber R. Mendonça

      Version of Record online: 11 MAY 2005 | DOI: 10.1002/cphc.200400391

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      Nonlinear optics: The degenerate two-photon absorption spectra of several azoaromatic compounds were determined using the femtosecond Z-scan technique (see graphic; DIAMINO=diaminoazobenzene, DR13=Disperse Red 13). The resonance enhancement and the peak of the two-photon absorption cross-section could be adjusted with a model based on perturbation theory.

    20. Cross-Linking of Polyolefins: A Study by Thermoporosimetry with Benzene Derivatives as Swelling Solvents (pages 1126–1132)

      Nicolas Billamboz, Jean-Marie Nedelec, Manuel Grivet and Mohamed Baba

      Version of Record online: 18 MAY 2005 | DOI: 10.1002/cphc.200400472

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      Swollen polymers cross-examined: The cross-linking levels of irradiated polyolefins swollen by solvents, such as o-, m-, p-xylene, p-dichlorobenzene, 1,2,4-trichlorobenzene and naphthalene, are studied by thermoporosimetry. The results from differential scanning calorimetry experiments allow calculation of the mesh-size distribution of the swollen polymeric gel (see graphic).

    21. Molecular Dynamics and Conformational Kinetics of Mono- and Disaccharides in Aqueous Solution (pages 1133–1145)

      Ralph Behrends and Udo Kaatze

      Version of Record online: 8 JUN 2005 | DOI: 10.1002/cphc.200400508

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      Conformational changes in carbohydrates: Broadband acoustic and dielectric measurements of saccharides in water are used to obtain detailed information about ring isomerizations and excyclic hydroxylmethyl group rotations as well as their interferences with calcium complex formation. The graphic shows an acoustical spectrum of a D-fructose solution. A chair–chair inversion is reflected by low-frequency relaxation.

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      Energy Transfer in Single Hydrogen-Bonded Water Molecules (pages 1146–1156)

      Huib J. Bakker, Joop J. Gilijamse and Anjan J. Lock

      Version of Record online: 11 MAY 2005 | DOI: 10.1002/cphc.200400606

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      Simple system, complex behavior: The authors present a detailed linear vibrational and femtosecond mid-infrared pump–probe spectroscopic study on the structure and dynamics of hydrogen-bonded complexes of single H2O/HDO molecules and acetone dissolved in CCl4. The picture shows the T conformation of a water–acetone complex.

    23. Energy Flow in Push–Pull Chromophores: Vibrational Dynamics in para-Nitroaniline (pages 1157–1163)

      Tissa Gunaratne, J. Reddy Challa and M. Cather Simpson

      Version of Record online: 10 MAY 2005 | DOI: 10.1002/cphc.200400288

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      Photoexcitation: Ultrafast time-resolved anti-Stokes resonance Raman spectroscopy (TRARRS) on para-nitroaniline (see picture), the prototype of push–pull chromophores, supports a picture in which vibrational, conformational, and solvent dynamics on the S1 surface are fast relative to the internal conversion rate. Phenyl breathing and symmetric NO2 stretching ultimately accept excess vibrational energy deposited in the S0 state during internal conversion, and then lose this energy with lifetimes of 8.1 and 5.2 ps, respectively.

    24. Angle-Resolved Photoelectron Spectroscopy of Randomly Oriented 3-Hydroxytetrahydrofuran Enantiomers (pages 1164–1168)

      Anna Giardini, Daniele Catone, Stefano Stranges, Mauro Satta, Mario Tacconi, Susanna Piccirillo, Stefano Turchini, Nicola Zema, Giorgio Contini, Tommaso Prosperi, Pietro Decleva, Devis Di Tommaso, Giovanna Fronzoni, Mauro Stener, Antonello Filippi and Maurizio Speranza

      Version of Record online: 8 JUN 2005 | DOI: 10.1002/cphc.200400483

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      Not only the electron distribution but also the structure, conformation, and nuclear vibrational motion of floppy chiral molecules markedly affect the angular distribution of the valence electrons emitted by their interaction with circularly polarized vacuum ultraviolet light (see picture). These findings suggest that circular dichroism may be a tool for investigating the structural and conformational dynamics of chiral molecules in the isolated state.

    25. How Good is Fluorine as a Hydrogen-Bond Acceptor in Fluorinated Single-Walled Carbon Nanotubes? (pages 1169–1174)

      Holger F. Bettinger

      Version of Record online: 8 JUN 2005 | DOI: 10.1002/cphc.200400324

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      Three-centered, chelated hydrogen bonds are important in the interaction between methanol and highly fluorinated single-walled carbon nanotubes (F-SWNTs) of stoichiometry (C2F)n, according to ab initio investigations on finite F-SWNT models, such as that shown in the picture.

    26. A Computational Study of Thiolate and Selenolate Oxidation by Hydrogen Peroxide (pages 1175–1180)

      Bruno Cardey and Mironel Enescu

      Version of Record online: 10 MAY 2005 | DOI: 10.1002/cphc.200400568

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      Rapid residues: The selenocysteine residue in the glutathione peroxidase active centre is efficiently oxidised by hydrogen peroxide with a rate constant that is several orders of magnitude greater than that reported for cysteine in aqueous solution. To understand the origin of this difference, the reaction of selenolate and thiolate with hydrogen peroxide (transition state given in the graphic) is analysed by means of ab initio calculations.

    27. Probing Binding-Mode Diversity in Guanidinium–Oxoanion Host–Guest Systems (pages 1181–1186)

      Manal Haj-Zaroubi and Franz P. Schmidtchen

      Version of Record online: 10 MAY 2005 | DOI: 10.1002/cphc.200400559

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      The ties that bind: Does host–guest binding in solution produce a unique complex structure? Calorimetry combined with trend analysis provides a route to unfold the problem of binding-mode diversity using the popular guanidinium–oxoanion supramolecular motif as an example (see picture).

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      Preview: ChemPhysChem 6/2005 (page 1190)

      Version of Record online: 8 JUN 2005 | DOI: 10.1002/cphc.200590012