ChemPhysChem

Cover image for Vol. 6 Issue 4

April 15, 2005

Volume 6, Issue 4

Pages 565–750

    1. Cover Picture: Engineering the Electronic Structure of Single-Walled Carbon Nanotubes by Chemical Functionalization (ChemPhysChem 4/2005) (page 565)

      Jijun Zhao, Zhongfang Chen, Zhen Zhou, Hyoungki Park, Paul von Ragué Schleyer and Jian Ping Lu

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200590003

      The cover picture shows single-walled carbon nanotube (SWCNT) sidewalls that can be opened by chemical modifications such as a CCl2 addition reaction. The SWCNT electronic structures near the Fermi level are only changed slightly by functionalizations at low modification ratios; however, at higher ratios, the metallic SWCNTs become nonmetallic. Therefore, the electronic properties of SWCNTs can be controlled by chemical modification. Details can be found in the Communication by J. Zhao, Z. Chen and co-workers on page 598.

    2. Graphical Abstract: ChemPhysChem 4/2005 (pages 567–574)

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200590004

    3. Single Carbon Nanotube Optical Spectroscopy (pages 577–582)

      Achim Hartschuh, Hermenegildo N. Pedrosa, Jeffrey Peterson, Libai Huang, Pascal Anger, Huihong Qian, Alfred J. Meixner, Mathias Steiner, Lukas Novotny and Todd D. Krauss

      Article first published online: 7 MAR 2005 | DOI: 10.1002/cphc.200400408

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      Ideal single photons: Fluorescence spectra from single carbon nanotubes (see picture) provide novel insights into their electronic structure and demonstrate the potential of nanotubes as a stable, single-molecule infrared photon source for applications in quantum optics and biophotonics.

    4. Double-Tunnel Nanoscale Switch with a Redox Mediator: Operational Principles and Tunneling Spectroscopy (pages 583–586)

      A. A. Kornyshev, A. M. Kuznetsov and J. Ulstrup

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200400586

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      Molecular-scale electronics: In this Concept, the principles of operation of an electrochemical double-tunnel contact switch are formulated and basic current–voltage characteristics are provided (see picture): A bridge molecule with a redox group b anchors the nanoparticle to the substrate electrode at a distance d. The potential drops between the substrate and the reference electrode and between the substrate and the scanning tunnelng microscopy (STM) tip (located at a distance s from the nanoparticle). Vbias can be controlled independently.

    5. Synergistic Enhancement of the Solubility of Hexamethylenetetramine in Subcritical CO2–Ethanol Mixtures Studied by Infrared Spectroscopy (pages 587–590)

      Santiago Sala, Nora Ventosa, Thierry Tassaing, Mary Cano, Yann Danten, Marcel Besnard and Jaume Veciana

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200400499

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      A vibrational spectroscopic survey of CO2-expanded ethanol solutions of hexamethylenetetramine allows the investigation of the organization of solvent molecules in the solute cybotactic region. The synergistic solubility enhancement observed in this system is explained by the occurrence of co-operative interactions of EtOH and CO2 around hexamethylenetetramine molecules, as schematized in the picture.

    6. Multiwalled Carbon Nanotubes Covalently Modified with Fast Black K (pages 590–595)

      Henry C. Leventis, Gregory G. Wildgoose, Ieuan G. Davies, Li Jiang, Timothy G. J. Jones and R. G. Compton

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200400536

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      Nanoscale electrochemical switching device: A novel material comprising molecules of the azo-dye Fast Black K (2,5-dimethoxy-4-[(4-nitrophenyl)azo]benzenediazonium chloride, FBK) covalently attached to multiwalled carbon nanotubes (MWCNTs) is shown to form the basis of a nanoscale voltammetric switching device (see picture) for use in electronic nanocircuits, or alternatively, in high-density memory storage devices. The FBK-derivatised MWCNTs may also be used as a chemical release reagent.

    7. Towards Raman Optical Activity Calculations of Large Molecules (pages 595–597)

      Gérard Zuber, Michael-Rock Goldsmith, David N. Beratan and Peter Wipf

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200400544

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      A chiroptical spectroscopy tool: A strategy to extend Raman optical activity (ROA) calculations to larger chiral systems and biomolecules is presented by avoiding the evaluation of the four-center Coulomb integrals and by omitting the electric quadrupole contribution. The computational (see picture) and experimental ROA spectra of (4S)-Galaxolide® are compared to demonstrate the applicability of this methodology.

    8. Engineering the Electronic Structure of Single-Walled Carbon Nanotubes by Chemical Functionalization (pages 598–601)

      Jijun Zhao, Zhongfang Chen, Zhen Zhou, Hyoungki Park, Paul von Ragué Schleyer and Jian Ping Lu

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200400593

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      Nanotube sidewall opening: The functionalization of single-walled carbon nanotubes (SWCNTs) by addition of CCl2 and NCOOC2H5 groups to the sidewalls has been investigated computationally using density functional theory. The SWCNT electronic structures near the Fermi level are only changed slightly by functionalization at low modification ratios. However, at higher ratios, the metallic SWCNTs become nonmetallic (see graphic).

    9. Photochemical α-Cleavage in Pyran-2-thione: Generation of Aldehyde–Thioketene and Thioaldehyde–Ketene Photoproducts (pages 602–604)

      Susana Breda, Igor D. Reva, Leszek Lapinski and Rui Fausto

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200400539

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      Ring-opening photoreaction: UV irradiation (λ>337 nm) of a matrix-isolated, unstrained six-membered-ring thiocarbonyl compound, pyran-2-thione, promotes the ring-opening photoreaction that leads to the cleavage of the C[BOND]O α-bond yielding the open-ring aldehyde–thioketene, which after subsequent rearrangement can be transformed in its isomeric thioaldehyde–ketene (see picture).

    10. Direct NMR Evidence for the Presence of Mobile Surface Hydrides on Ruthenium Nanoparticles (pages 605–607)

      Tal Pery, Katrin Pelzer, Gerd Buntkowsky, Karine Philippot, Hans-Heinrich Limbach and Bruno Chaudret

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200400621

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      Surface-reactive metal colloids: Ruthenium nanoparticles are able to accommodate hydrogen atoms at, or immediately below, their surface, as shown by a combination of liquid, gas-phase and solid-state NMR techniques. The hydrogen atoms are mobile on the ruthenium particles—and reactive—which leads to fast hydrogen–deuterium exchange with the ligands (see graphic) even in the solid state.

    11. On Differences between Hydrogen Bonding and Improper Blue-Shifting Hydrogen Bonding (pages 609–617)

      Wiktor Zierkiewicz, Petr Jurečka and Pavel Hobza

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200400243

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      Red- and blue-shifting H bonds: The nature of the red and blue shifts in standard and improper H-bonded complexes is different (see graphic). While in the former case the shift comes from the electron transfer to the σ* orbital of the proton donor, in the latter case all the attractive forces, including dispersion, act against exchange–repulsion, which leads to compression of the X⋅⋅⋅H bond and blue shift.

    12. Noncovalent Complexes between Dimethyl Ether and Formic Acid—An Ab Initio and Matrix Isolation Study (pages 618–624)

      Elsa Sánchez-García, Marc Studentkowski, Luis A. Montero and Wolfram Sander

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200400430

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      Hydrogen-bonded complexes: The thermal aggregation of monomeric formic acid and dimethylether produces two dimers A and B (see picture) that could be characterized by matrix infrared spectroscopy in combination with high-level ab initio calculations. According to the calculations the two dimers are energetically almost degenerate.

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      Solvent-Dependent Photoacidity State of Pyranine Monitored by Transient Mid-Infrared Spectroscopy (pages 625–636)

      Omar F. Mohammed, Jens Dreyer, Ben-Zion Magnes, Ehud Pines and Erik T. J. Nibbering

      Article first published online: 14 MAR 2005 | DOI: 10.1002/cphc.200400510

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      Solvation dynamics: Femtosecond mid-infrared spectroscopy is used to demonstrate that a solvent-dependent photoacidity state exists in pyranine (see picture; HPTS=8-hydroxy-1,3,6-trisulfonate pyrene).

    14. Autoxidation of Cyclohexane: Conventional Views Challenged by Theory and Experiment (pages 637–645)

      Ive Hermans, Thanh Lam Nguyen, Pierre A. Jacobs and Jozef Peeters

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200400211

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      Radical mechanism innovation: Theoretical chemistry is shown to be an efficient optimization tool for industrial processes. Theoretical evidence confirmed by experimental observations is presented for crucial, hitherto overlooked, radical reaction paths that are shown to have a major impact on the kinetics and product distribution of the autoxidation of cyclohexane (see picture).

    15. Kinetics and Stability of CH4–CO2 Mixed Gas Hydrates during Formation and Long-Term Storage (pages 646–654)

      Tsutomu Uchida, Ikuko Y. Ikeda, Satoshi Takeya, Yasushi Kamata, Ryo Ohmura, Jiro Nagao, Olga Y. Zatsepina and Bruce A. Buffett

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200400364

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      Storage mechanism of mixed gas hydrates: Variations in gas composition during formation of a CH4–CO2 mixed gas hydrate in a batch-type reactor (see graphic) and Raman spectroscopic analysis on the obtained samples showed that CH4 molecules play important roles in the formation process. Long-term storage of these hydrates under thermodynamically stable conditions showed that the hydrates were relatively unstable and lost more CO2 than CH4.

    16. Dynamic Evolution of Kohn–Sham Electron Density in the Real-Time Domain with Finite Basis Expansion (pages 655–662)

      Anguang Hu and Tom K. Woo

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200400381

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      Quantum chemistry: A novel method is presented for time-dependent density functional theory calculations on dynamic linear response and electron density evolution in the real-time domain with the finite basis expansion approach of conventional quantum chemistry. Dynamic polarizabilities of a water chain and diphenylene molecules (see response densities at selected time intervals) are computed to demonstrate the validity and efficiency of this method.

    17. Mechanical Response Analysis and Power Generation by Single-Cell Stretching (pages 663–670)

      Alexandre Micoulet, Joachim P. Spatz and Albrecht Ott

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200400417

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      Single-cell stretching of tissue cells under physiological conditions (see picture) allowed a detailed analysis of the mechanical properties of single cells and provided information about their active and passive mechanical responses to a defined force stimulation and a power generation of Pmax=10−16 Watts, which corresponds to 2500 ATP molecules s−1 at 10 kBT/molecule.

    18. Theoretical Study of Inversion and Topomerization Processes of Substituted Cyclohexanes: The Relevance of the Energy 3D Hypersurface (pages 671–680)

      María del Carmen Fernández-Alonso, Javier Cañada, Jesús Jiménez-Barbero and Gabriel Cuevas

      Article first published online: 1 APR 2005 | DOI: 10.1002/cphc.200400495

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      No more 2D conformational schemes: The conformational dynamics of methylcyclohexane, oxane (see graphic), and thiane occurs through two independent processes, inversion and topomerization. These processes are connected by some common conformers. Three- dimensional schemes are presented, which allow for a more appropriate idea of the process, and their use shows the limitation of the traditional 2D schemes.

    19. Conformational and Electronic Properties of a Microperoxidase in Aqueous Solution: A Computational Study (pages 681–689)

      Carla Di Teodoro, Massimiliano Aschi, Andrea Amadei, Danilo Roccatano, Francesco Malatesta and Luca Ottaviano

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200400493

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      Enzyme structure–activity relation: A theoretical study of the conformational properties of a small heme peptide in aqueous solution is carried out by classical, long-timescale molecular dynamics simulations (see picture). The electronic properties of this species, that is, the relative energies of its excited electronic states and the redox potential, are reproduced and related to the conformational behavior using the perturbed matrix method and basic statistical mechanics.

    20. A Kinetic Model to Describe Nanocrystal Growth by the Oriented Attachment Mechanism (pages 690–696)

      Caue Ribeiro, Eduardo J. H. Lee, Elson Longo and Edson R. Leite

      Article first published online: 11 MAR 2005 | DOI: 10.1002/cphc.200400505

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      Nanoparticle growth on colloids is strongly influenced by coalescence mechanisms (see figure). Several works have discussed the growth mechanism of such nanoparticles; however, only few physical models have been reported which can contribute to a better understanding of this process. The authors propose a physical model, which is based on classical coagulation models, to explain nanoparticle growth by coalescence and its implications.

    21. The Sound Velocity in Ideal Liquid Mixtures from Thermal Volume Fluctuations (pages 697–705)

      Helge Pfeiffer and Karel Heremans

      Article first published online: 11 MAR 2005 | DOI: 10.1002/cphc.200400534

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      Molecular acoustics: The selection of the correct mixing rule for sound velocity in ideal liquid mixtures determines the interpretation of the sound velocity in real mixtures. The authors present a new derivation of the mixing rule, which is based on statistical mechanics, and demonstrate that the correlation of volume fluctuations between adjacent components of the propagation medium (see picture) has a crucial influence on the ideal mixing rule.

    22. Possible Pathways of CVD Processes Leading to III–V Semiconductors via a Two-Dimensional Growth (pages 706–713)

      Hans-Jörg Himmel

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200400643

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      The first possible intermediates formed during chemical vapour deposition (CVD) processes leading to III–V semiconductors via a two-dimensional growth process were studied applying quantum-chemical calculations (see picture).

    23. Bandgap Widening of Titania through Semiconductor Support Interactions (pages 714–718)

      Marc Gärtner, Viatcheslav Dremov, Paul Müller and Horst Kisch

      Article first published online: 14 MAR 2005 | DOI: 10.1002/cphc.200400185

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      Bandgap control: Covalent attachment of titania onto silica increases the bandgap energy by up to 0.27 eV as indicated in the figure. Surprisingly, this does not arise from a quantum size effect but rather from an electronic semiconductor support interaction.

    24. Ab Initio Calculations and Franck–Condon Simulation of the Absorption Spectra of GeCl2 Including Anharmonicity (pages 719–731)

      Daniel K. W. Mok, Foo-tim Chau, Edmond P. F. Lee and John M. Dyke

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200400489

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      The ã–X̃ and ÖX̃ transitions in the laser-induced fluorescence (LIF) spectra of GeCl2 are studied theoretically with high-level ab initio calculations and spectral simulations using anharmonic Franck–Condon factors. In the first case, good agreement is obtained between simulated and observed LIF spectra. For the ÖX̃ transition (see graphic), a non-Boltzmann vibrational population distribution of the X̃ state and a revised vibrational assignment are proposed.

    25. Photophysical and Electrochemical Properties of meso,meso-Linked Oligoporphyrin Rods with Appended Fullerene Terminals (pages 732–743)

      Nicola Armaroli, Gianluca Accorsi, Fayi Song, Amit Palkar, Luis Echegoyen, Davide Bonifazi and François Diederich

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200400558

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      Electro- and photoactive nanorods: Electronic interactions between the porphyrin backbone and carbon spheres of oligoporphyrin rods with two fullerene residues are evidenced by electrochemistry and UV/Vis spectroscopy. Photoinduced porphyrin[RIGHTWARDS ARROW]fullerene electron transfer and radiative charge recombination in the near-infrared region are observed, the kinetics and color of which are tunable by solvent polarity (see picture; red: zinc porphyrin units; blue: C60).

    26. Preview: ChemPhysChem 4/2005 (page 750)

      Article first published online: 12 APR 2005 | DOI: 10.1002/cphc.200590005

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