ChemPhysChem

Cover image for Vol. 7 Issue 2

February 13, 2006

Volume 7, Issue 2

Pages 281–534

    1. Cover Picture: Multifunctional Carbon Nanofibers with Conductive, Magnetic and Superhydrophobic Properties (ChemPhysChem 2/2006) (page 281)

      Ying Zhu, Jing Chang Zhang, Jin Zhai, Yong Mei Zheng, Lin Feng and Lei Jiang

      Article first published online: 6 FEB 2006 | DOI: 10.1002/cphc.200690004

      The cover picture shows water droplets on a superhydrophobic surface of carbon nanofibers (CNFs) forming spheres. Inspired by self-cleaning plant leaves an interesting hybrid material, made of electrospun nanofibers, has been obtained with not only conductive and magnetic (see the hysteresis loop of the CNFs) but also superhydrophobic properties. This self-cleaning material may find application as corrosive protection or electromagnetic shielding coating. To read how Y. Zhu et al. combine conductive, magnetic and superhydrophobic properties of these CNFs, please turn to page 336.

    2. Graphical Abstract: ChemPhysChem 2/2006 (pages 283–293)

      Article first published online: 6 FEB 2006 | DOI: 10.1002/cphc.200690005

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    4. Microwave Synthesis of Nanoporous Materials (pages 296–319)

      Geoffrey A. Tompsett, William Curtis Conner and K. Sigfrid Yngvesson

      Article first published online: 6 FEB 2006 | DOI: 10.1002/cphc.200500449

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      Microwaves in material synthesis: Microwaves can increase the rate of synthesis of nanoporous materials by orders of magnitude. Many porous materials and membranes have been prepared using microwave synthesis (see figure). The enhancement depends on several mechanistic and engineering factors, resulting in thermal and nonthermal effects.

    5. Resonant X-ray Scattering: A Tool for Structure Elucidation in Liquid Crystals (pages 321–328)

      Helen F. Gleeson and Linda S. Hirst

      Article first published online: 6 FEB 2006 | DOI: 10.1002/cphc.200500426

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      Forbidden reflections reveal liquid crystal structures: The technique of resonant X-ray scattering (see figure) has recently been applied with great success to the study of subtle structures in liquid crystals (LCs). Results are reviewed and future directions considered.

    6. Array Formation in Evanescent Waves (pages 329–332)

      Christopher D. Mellor and Colin. D. Bain

      Article first published online: 27 DEC 2005 | DOI: 10.1002/cphc.200500348

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      A chessboard pattern: Polystyrene particles form arrays at the silica–water interface, trapped in the evanescent field of two counterpropagating laser beams (see figure; particle size: 460 nm). In the horizontal direction, the periodicity of the array is twice the spacing of the interference fringes of the laser beam. In the vertical direction, the periodicity depends on the particle diameter and the ionic strength, which affects the repulsive potential between the charged latices.

    7. Electrochemical Synthesis and Fabrication of Gold Nanostructures Based on Poly(N-vinylpyrrolidone) (pages 333–335)

      Houyi Ma, Shaoxin Huang, Xingli Feng, Xiaokai Zhang, Fang Tian, Feifei Yong, Wei Pan, You Wang and Shenhao Chen

      Article first published online: 6 FEB 2006 | DOI: 10.1002/cphc.200500398

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      Building blocks: Poly(N-vinylpyrrolidone)-protected gold nanoparticles synthesized electrochemically were used as “building blocks” to construct varieties of nanostructures (see figure), including well-defined nanorings, single-crystal films and dense particle films.

    8. Multifunctional Carbon Nanofibers with Conductive, Magnetic and Superhydrophobic Properties (pages 336–341)

      Ying Zhu, Jing Chang Zhang, Jin Zhai, Yong Mei Zheng, Lin Feng and Lei Jiang

      Article first published online: 12 JAN 2006 | DOI: 10.1002/cphc.200500407

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      Multifunctional carbon nanofibers (CNFs, see picture), fabricated by a simple electrospinning method, show not only outstanding conductive and magnetic but also superhydrophobic characteristics, which make these materials attractive for the application as corrosive protection and electromagnetic shielding coating. The conductive and magnetic properties of these materials are maintained by the superhydrophobic surfaces.

    9. Vibrational Properties of CrII Centers on Reduced Phillips Catalysts Highlighted by Resonant Raman Spectroscopy (pages 342–344)

      Alessandro Damin, Francesca Bonino, Silvia Bordiga, Elena Groppo, Carlo Lamberti and Adriano Zecchina

      Article first published online: 3 JAN 2006 | DOI: 10.1002/cphc.200500408

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      Surface chromate species on Phillips catalysts are probed directly using resonant Raman spectroscopy (see figure). Under pre-resonance conditions, for the first time, the vibrational features of the CrII-active centers and their evolution upon interaction with N2 and CO are observed.

    10. A C2 Molecule Entrapped in the Pentagonal-Dodecahedral Y2 Cage in Y2C2@C82(III) (pages 345–348)

      Eiji Nishibori, Shintaro Narioka, Masaki Takata, Makoto Sakata, Takashi Inoue and Hisanori Shinohara

      Article first published online: 6 FEB 2006 | DOI: 10.1002/cphc.200500437

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      Carbon-encapsulating metallofullerenes: A C2 molecule is entrapped in the pentagonal-dodecahedral charge density of Y2 in Y2C2@C82(III) according to the maximum entropy/Rietveld analysis of the synchrotron X-ray powder diffraction data, which clearly show an additional charge-density peak for C2 (blue) inside the pentagonal-dodecahedral Y2 cage (red) in Y2C2@C82(III) (picture, left) but not in Y2@C82(III) (right).

    11. A Novel Electrochemical Information Storage System Based on Stripping Voltammetry of Metals (pages 349–352)

      Ronen Polsky, Ronan Baron, Eugenii Katz and Itamar Willner

      Article first published online: 16 JAN 2006 | DOI: 10.1002/cphc.200500450

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      Write–read systems: Stripping voltammetry of metals allows the encoding of information and the development of “write—read” systems. A novel electrochemical information storage system that is capable of encoding large bits of information in the form of distinct voltammograms corresponding to the stripping behavior of metal ions is described. The picture shows the corresponding square wave voltammograms that spell out the words “Hebrew University”.

    12. Determining Molecular Structures and Conformations Directly from Electron Diffraction using a Genetic Algorithm (pages 353–362)

      Scott Habershon and Ahmed H. Zewail

      Article first published online: 13 JAN 2006 | DOI: 10.1002/cphc.200500532

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      Structure of conformationally flexible molecules (see diagram): Quantum mechanical geometry optimizations, which are expensive and time-consuming, are bypassed as the authors present a protocol based on the application of a global optimization strategy (a genetic algorithm) which accurately predicts the structure directly from gas-phase electron diffraction data.

    13. Femtosecond Relaxation Dynamics of Solvated Electrons in Liquid Ammonia (pages 363–369)

      Jörg Lindner, Andreas-N. Unterreiner and Peter Vöhringer

      Article first published online: 6 FEB 2006 | DOI: 10.1002/cphc.200500467

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      From ultrafast transients to solvation structures? Femtosecond near-infrared pump–probe spectroscopy provides the first glimpse at the ultrafast relaxation dynamics and the microscopic structure of the solvent environment of the famous solvated electron in liquid ammonia (see figure).

    14. Synthesis and Photoluminescence of Titania Nanoparticle Arrays Templated by Block-Copolymer Thin Films (pages 370–378)

      Zaicheng Sun, Dong Ha Kim, Markus Wolkenhauer, Gabriela Gina Bumbu, Wolfgang Knoll and Jochen S. Gutmann

      Article first published online: 3 JAN 2006 | DOI: 10.1002/cphc.200500340

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      Photophysics of titania nanoparticles: Ordered crystalline titania nanoparticles are obtained via a sol–gel synthetic route. The resulting nanoparticle arrays are initially amorphous but highly ordered over large distances as proven by grazing incidence small-angle X-ray scattering (GISAXS; see picture) experiments. The photophysical properties before and after calcination of the samples are also reported.

    15. Field Effect of Screened Charges: Electrical Detection of Peptides and Proteins by a Thin-Film Resistor (pages 379–384)

      Simon Q. Lud, Michael G. Nikolaides, Ilka Haase, Markus Fischer and Andreas R. Bausch

      Article first published online: 11 JAN 2006 | DOI: 10.1002/cphc.200500484

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      A biosensing device based on a thin-film resistor: The direct electrical detection of small peptides and proteins by their intrinsic charges is achieved using a biofunctionalized thin-film resistor (see figure). The response of the nanometer-thin conducting silicon film to electrolyte screening effects is taken into account to determine quantitatively the charges of the peptides. Even in physiological electrolyte solutions it is possible to detect peptides with a single charge and to distinguish single charge variations of the analytes.

    16. Controllable Growth of Straight Nanorods and Nanowires in the Langmuir Films of a Bolaamphiphilic PAR Derivative (pages 385–393)

      Peizhi Guo , Minghua Liu, Hiroo Nakahara and Kiminori Ushida

      Article first published online: 19 DEC 2005 | DOI: 10.1002/cphc.200500268

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      One-dimensional nanostructures: When the bolaamphiphile (PAR)2C10 is spread in a subphase containing Cu(NO3)2, either nanorods or nanowires can be obtained depending on the concentration of Cu(II) ions (see picture). Furthermore, it is shown that the counteranions can also affect the morphology of the nanostructures formed. These results, which were not observed for other metal ions, may lead to a new, facile way of fabricating 1D regular nanoarchitectures.

    17. Study of the Pmequation imagen Space Group of Cubic Mesoporous Silica (pages 394–399)

      Shuhua Han, Wanguo Hou, Jun Xu, Xirong Huang and Liqiang Zheng

      Article first published online: 3 JAN 2006 | DOI: 10.1002/cphc.200500271

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      Using a Gemini surfactant with a short spacer, namely, [C14H25N+(CH3)2[BOND](CH2)2[BOND]N+(CH3)2C14H25]⋅2 Br, as structure-directing agent and sodium silicate as precursor under hydrothermal conditions in the presence of ethyl acetate resulted in high-quality, ordered cubic mesoporous silica with space group Pmequation imagen. The picture shows a transmission electron micrograph of a sample prepared with a surfactant-to-sodium-silicate ratio of 0.33.

    18. Effective Controlled Release of Captopril by Silylation of Mesoporous MCM-41 (pages 400–406)

      Fengyu Qu, Guangshan Zhu, Shiying Huang, Shougui Li and Shilun Qiu

      Article first published online: 13 JAN 2006 | DOI: 10.1002/cphc.200500294

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      Remarkable silica surfaces: The tuning of the surface hydrophilicity/hydrophobicity and the steric hindrance properties of mesoporous silica via stepwise silylation controls the drug release rate of the water-soluble drug, Captopril (see figure).

    19. Berry Pseudorotation Mechanism for the Interpretation of the 19F NMR Spectrum in PF5 by Ab Initio Molecular Dynamics Simulations (pages 407–413)

      Christophe Raynaud, Laurent Maron, Jean-Pierre Daudey and Franck Jolibois

      Article first published online: 11 JAN 2006 | DOI: 10.1002/cphc.200500297

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      Fluxional effects in PF5 can be included using ab initio molecular dynamics for the theoretical determination of 19F NMR parameters that are in agreement with experiment. The picture shows the average shielding constants of all fluorine 19F atoms over a series of 10 000 snapshots obtained by ab initio molecular dynamics simulations performed at 1000 K.

    20. Asbestos Mineral Analysis by UV Raman and Energy-Dispersive X-ray Spectroscopy (pages 414–420)

      Renate Petry, Remigius Mastalerz, Stefan Zahn, Thomas G. Mayerhöfer, Günther Völksch, Lothar Viereck-Götte, Birgit Kreher-Hartmann, Lothar Holz, Markus Lankers and Jürgen Popp

      Article first published online: 3 JAN 2006 | DOI: 10.1002/cphc.200500303

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      Excited minerals: UV micro-Raman spectroscopy at excitation wavelengths of 257 and 244 nm and scanning electron microscopy/energy-dispersive X-ray analysis have been used to examine fibrous asbestos minerals (see picture). The fluorescence-free Raman bands give a molecular fingerprint that allows differentiation between the different asbestos species in the serpentine and amphibole structural groups.

    21. Chair, Boat and Twist Conformation of Dodecamethylcyclohexasilane and Undecamethylcyclohexasilane: A Combined DFT and Raman Spectroscopic Study (pages 421–429)

      Günter Tekautz, Alexandra Binter, Karl Hassler and Michaela Flock

      Article first published online: 13 JAN 2006 | DOI: 10.1002/cphc.200500417

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      Stable conformers: Theoretical investigations generating the potential energy surface of methylated silanes show that for Si6Me12 there are three local minima structures, the chair, twist, and boat conformers (see figure). The twist and the boat structures cannot be distinguished by Raman spectroscopy due to the small energy barrier and the similarity between their vibrational modes. The calculated relative energy between the chair and twist conformers is confirmed by the results of temperature-dependent Raman measurements.

    22. Homolysis of N-alkoxyamines: A Computational Study (pages 430–438)

      Anouk Gaudel-Siri, Didier Siri and Paul Tordo

      Article first published online: 6 FEB 2006 | DOI: 10.1002/cphc.200500308

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      Nitroxide-mediated polymerization (NMP): The relative bond dissociation energy (BDE) of the NO[BOND]C bond within a series of N-alkoxyamines is estimated. Good correlations between the calculated BDE (NO[BOND]C) and the experimental cleavage temperatures and the dissociation rate constants are obtained. These correlations are a predictive tool for finding new nitroxide controllers for the NMP of acrylic or styrenic monomers (see figure).

    23. Potential Energy Surfaces of the Microhydrated Guanine⋅⋅⋅Cytosine Base Pair and its Methylated Analogue (pages 439–447)

      Lucie Zendlová, Pavel Hobza and Martin Kabeláč

      Article first published online: 6 FEB 2006 | DOI: 10.1002/cphc.200500311

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      A complete scan of potential and free-energy surfaces of microhydrated guanine⋅⋅⋅cytosine and 9-methylguanine⋅⋅⋅1-methylcytosine base pairs was realized by the molecular dynamics/quenching technique. There is a preference for stacked structures of nucleic acids base pairs in an aqueous environment due to the hydrophilic interaction of water molecules with the base pairs. The picture shows the two most stable structures for 9-methylguanine⋅⋅⋅1-methylcytosine.

    24. Probing the Acidity of p-Substituted Phenols in the Excited State: Electronic Spectroscopy of the p-Cyanophenol–Water Cluster (pages 448–454)

      Christoph Jacoby , Marcel Böhm, Chau Vu, Christian Ratzer and Michael Schmitt

      Article first published online: 13 JAN 2006 | DOI: 10.1002/cphc.200500365

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      Clusters under investigation: Rotationally resolved UV spectroscopy along with ab initio calculations of the p-cyanophenol–water cluster are used to investigate the correlation between the structures of substituted phenol clusters and the pKa values of the respective monomers moieties (see picture).

    25. A Theoretical Study of the Structure and Bonding of UOX4 (X=F, Cl, Br, I) Molecules: The Importance of Inverse Trans Influence (pages 455–462)

      Attila Kovács and Rudy J. M. Konings

      Article first published online: 6 FEB 2006 | DOI: 10.1002/cphc.200500324

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      Four stationary points were located on the potential energy surface of UOX4 (X=F, Cl, Br, I), which corresponded to the C2v , C3v , C4v and Cs structures. UOF4 prefers the C3v structure, whereas the oxyhalides with larger halogen atoms prefer the C2v structure (see picture). The inverse trans influence is important in stabilising the sterically less favoured C3v geometry. The U[DOUBLE BOND]O double bonds show a clear triple-bond character.

    26. Structure of the HOOO Radical in Liquid Water: A Theoretical Study (pages 463–467)

      Stéphanie Chalmet and Manuel F. Ruiz-López

      Article first published online: 11 JAN 2006 | DOI: 10.1002/cphc.200500326

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      Crucial electrostatic solvent effects: Ozone decomposition in the atmosphere and in liquid water seems to involve the HOOO radical. The structure of this species in liquid water is investigated using ab initio calculations, together with discrete, discrete-continuum, and continuum solvation models. Long-range electrostatic interactions are shown to play a crucial role, stabilizing the radical and forcing a trans conformation (see figure).

    27. Conductivity of Oriented Bis-azo Polymer Films (pages 468–474)

      Dirk Apitz, Ralph Peter Bertram, Nils Benter, Peter Sommer-Larsen, Per Michael Johansen and Karsten Buse

      Article first published online: 11 JAN 2006 | DOI: 10.1002/cphc.200500342

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      Electro-optic polymers: The conductivity of bis-azo polymer films (see picture) corona poled at various temperatures has been measured below and above the glass transition temperature (Tg), and after cooling. The orientation of the chromophores changes the charge-carrier mobility. Ionic conductivity dominates the initial disordered configuration, then hole hopping takes over in the liquid-crystalline phase above the Tg. Such microcrystallization enhances the conductivity.

    28. Computational Studies on the Cyclization of Polycyclic Aromatic Hydrocarbons in the Synthesis of Curved Aromatic Derivatives (pages 475–481)

      Elena Buñuel, Juan Marco-Martínez, Sergio Díaz-Tendero, Fernando Martín, Manuel Alcamí and Diego J. Cárdenas

      Article first published online: 6 FEB 2006 | DOI: 10.1002/cphc.200500345

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      Carbon cycles: The cyclization reactions of polycyclic aromatic hydrocarbons (PAHs) to form additional five- and six-membered rings (see picture) are studied at the DFT level, and intermediates and transition states for the possible pathways are determined. The relatively low activation energies suggest that ionization of PAHs can be used for the tailored preparation of nonplanar derivatives and new fullerenes.

    29. In situ and Online Monitoring of Hydrodynamic Flow Profiles in Microfluidic Channels Based upon Microelectrochemistry: Optimization of Electrode Locations (pages 482–487)

      Christian Amatore, Oleksiy V. Klymenko and Irina Svir

      Article first published online: 6 FEB 2006 | DOI: 10.1002/cphc.200500400

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      Microfluidic flow: Optimization of electrode widths (W) as well as generator–collector interelectrode gaps (Gmin<G<Gmax) are presented for single- and double-band assemblies, to enhance the speed and precision of the flow profile reconstruction for any Peclet number (Pe; see figure), using a method developed previously that allows the reconstruction of any experimental flow profile occurring in a microfluidic flow channel.

    30. A Kinetic Study of the Reaction between N,N-Dimethyl-p-toluidine and its Electrogenerated Radical Cation in a Room Temperature Ionic Liquid (pages 488–496)

      Russell G. Evans and Richard G. Compton

      Article first published online: 6 FEB 2006 | DOI: 10.1002/cphc.200500404

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      Reaction kinetics in a room temperature ionic liquid are investigated by analysing voltammetry for the anodic dimerisation of N,N-dimethyl-p-toluidine (DMT) in N-methyl-N-butylpyrrolidinium bis(trifluoromethylsulfonyl)imide (see figure). While both diffusion and heterogeneous electron transfer are significantly slowed relative to the same processes in a conventional nonaqueous solvent, the rate of the homogeneous deprotonation step between DMT and its radical cation is found to be largely unchanged.

    31. Sol–Gel Template Synthesis and Photoluminescence of n- and p-Type Semiconductor Oxide Nanowires (pages 497–501)

      Huaqiang Cao, Xianqing Qiu, Yu Liang, Lei Zhang, Meijuan Zhao and Qiming Zhu

      Article first published online: 19 DEC 2005 | DOI: 10.1002/cphc.200500452

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      Single-crystal oxide nanowires: Synthesis and characterization of nanowries made from n-type semiconductor SnO2 (see picture) and p-type semiconductor NiO are reported. The nanowires have diameters ranging from 100 to 300 nm and lengths exceeding 10 μm. The photoluminescence properties of these semiconductor nanowries are investigated.

    32. Multipeak Distributions of First Passage Times in Bistable Dynamics in a Model of a Thermochemical System (pages 502–507)

      Bogdan Nowakowski and Andrzej L. Kawczyński

      Article first published online: 20 JAN 2006 | DOI: 10.1002/cphc.200500461

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      Peak times: Fluctuations can induce transitions in bistable chemical systems, in which a stable focus coexists with a stable limit cycle. The distribution of the first passage times P(τ) from the cycle to the focus exhibits a multipeak form (see picture; N=number of molecules). A coherence resonance is observed for the return time from the focus to itself.

    33. Theoretical Study on the Structures and Electronic Spectra of TCNE2− (pages 508–513)

      Inmaculada García Cuesta, José Sánchez-Marín and Alfredo M. J. Sánchez de Merás

      Article first published online: 6 FEB 2006 | DOI: 10.1002/cphc.200500468

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      Stable geometric structures: The experimental electronic spectrum of the tetracyanoethylene dianion (TCNE2−; see figure) exhibits different features in dichloromethane and acetonitrile due to solute–solvent interactions. The authors use coupled cluster (CC) calculations which include the effects of the solvent to theoretically generate the spectra and elucidate the different geometrical structures adopted.

    34. Enantiodiscrimination between an N-Acetyl-L-cysteine SAM and Proline: An In Situ Spectroscopic and Computational Study (pages 514–523)

      Marco Bieri and Thomas Bürgi

      Article first published online: 6 FEB 2006 | DOI: 10.1002/cphc.200500474

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      Discriminating deprotonation: Intermolecular interactions between proline enantiomers and a chiral self-assembled monolayer (SAM) of N-acetyl-L-cysteine are investigated using IR modulation experiments (see figure) and density functional theory. At the surface of the SAM, the acid group exists in both the protonated and deprotonated form, however only the deprotonated form leads to enantioselectivity.

    35. Optical Properties of Gas-Phase Tryptophan–Silver Cations: Charge Transfer from the Indole Ring to the Silver Atom (pages 524–528)

      Rodolphe Antoine, Thibault Tabarin, Michel Broyer, Philippe Dugourd, Roland Mitrić and Vlasta Bonačić-Koutecký

      Article first published online: 6 FEB 2006 | DOI: 10.1002/cphc.200500495

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      The photodissociation spectrum of gas-phase [Trp-Ag]+ was measured from 215 to 330 nm (see figure) using a quadrupole ion trap coupled to an optical parametric-oscillator laser. The calculated absorption spectra for different prototype structures are presented. The results demonstrate that charge transfer can be photoinduced from the indole ring to the silver atom.

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      Preview: ChemPhysChem 2/2006 (page 534)

      Article first published online: 6 FEB 2006 | DOI: 10.1002/cphc.200690007

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