Cover image for ChemPhysChem

June 16, 2003

Volume 4, Issue 6

Pages 533–650

    1. Cover Picture: Electronic Excitation Energy Migration in a Photonic Dye–Zeolite Antenna (ChemPhysChem 6/2003) (page 533)

      Mikalai M. Yatskou, Marc Meyer, Stefan Huber, Michel Pfenniger and Gion Calzaferri

      Article first published online: 6 JUN 2003 | DOI: 10.1002/cphc.200390078

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    3. Search for Resolution of Chiral Fluorohalogenomethanes and Parity-Violation Effects at the Molecular Level (pages 541–548)

      Jeanne Crassous, Franck Monier, Jean-Pierre Dutasta, Michaël Ziskind, Christophe Daussy, Christophe Grain and Christian Chardonnet

      Article first published online: 6 JUN 2003 | DOI: 10.1002/cphc.200200536

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      Left and right are different. The physical and chemical properties of left-handed and right-handed enantiomers are often considered to be strictly identical. In fact, the weak interaction, which is extremely weak at the molecular level, is the only force that induces a difference between left and right (see picture). It is responsible for relative frequency differences of the order of 10-14–10-19 between the molecular spectra. Despite the very small size of the effect, the authors show that the perspective of its observation is not an inaccessible dream anymore. In this context, the resolution of the enantiomers of the simplest chiral molecules such as fluorohalogenomethanes is of great importance.

    4. Engineering Nanoarchitectures for Photonic Crystals (pages 549–554)

      Frank Marlow and Wenting Dong

      Article first published online: 6 JUN 2003 | DOI: 10.1002/cphc.200200531

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      Illuminating theory: After ten years intensive research on inverse opals, photonic crystals can still show surprises in theory and synthesis pathways. Although the electromagnetic theory of photonic crystals is well-developed and clear, the structure–property relationship is not yet fully understood. Small changes in structure (see graphic) lead to qualitative changes in the photonic properties. In the future, self-assembled or stepwise self-assembled systems may be found that show large photonic band gaps and versatile optical properties.

    5. Smaller–Faster–Brighter: Developing Optical Probes of the Future (pages 555–558)

      John M. Lupton

      Article first published online: 6 JUN 2003 | DOI: 10.1002/cphc.200300728

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      Optically brilliant: The fifth international topical conference on optical probes of conjugated polymers and organic and inorganic nanostructures was an exciting place to be and demonstrated three main directions of research: a move to do spectroscopy on individual molecules, application of ever faster coherent probes over an increasingly broad spectral range and the development of new material systems as well as enhancement of known ones. The graphic compares two different methods for studying such new materials, which contribute to models describing the role of excess energy in exciton dissociation processes.

    6. Ion–Dipole Interactions in Concentrated Organic Electrolytes (pages 559–566)

      Alexandre Chagnes, Stamatios Nicolis, Bernard Carré, Patrick Willmann and Daniel Lemordant

      Article first published online: 6 JUN 2003 | DOI: 10.1002/cphc.200200512

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      Pseudolattice models of conductivity must take into account ion–dipole interactions in addition to ion–ion interactions according to calculations of the activation energy for conductivity of various salts dissolved in γ-butyrolactone. The authors present an algorithm for calculating the strength of ion–dipole interactions that considers solvent molecules and ions as hard spheres and introduces a dielectric-field gradient around ions that takes account of their nature by a distance parameter. The results obtained from this model (see picture) are in fair agreement with experimental data.

    7. Electronic Excitation Energy Migration in a Photonic Dye–Zeolite Antenna (pages 567–587)

      Mikalai M. Yatskou, Marc Meyer, Stefan Huber, Michel Pfenniger and Gion Calzaferri

      Article first published online: 6 JUN 2003 | DOI: 10.1002/cphc.200300567

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      Seeing red with Zeolite: Electronic excitation energy migration in a host–guest material has been investigated by time-resolved fluorescence experiments and by Monte Carlo calculations. The main characteristic of the time evolution of acceptor,donor–zeolite L crystals is that the acceptor intensity is first built up before it starts to decay. This intensity increase becomes faster with increasing donor loading (see graphic), a fact which beautifully shows that the crystals behave as photonic antenna in which excitation energy is transported preferentially along the channels by a Förster-type mechanism until it reaches the acceptor, where it is emitted.

    8. Molecular Reorientational Dynamics of the Neat Ionic Liquid 1-Butyl-3-methylimidazolium Hexafluorophosphate by Measurement of 13C Nuclear Magnetic Relaxation Data (pages 588–594)

      Jürgen H. Antony, Dirk Mertens, Andreas Dölle, Peter Wasserscheid and William R. Carper

      Article first published online: 6 JUN 2003 | DOI: 10.1002/cphc.200200603

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      Hydrogen bonding plays a key role in the ionic liquid [BMIM]PF6, of which the calculated structure of one ion pair is shown in the picture. It occurs mainly between C2[BOND]H of the heterocyclic ring and the PF6 anion. This specific interaction strongly influences the molecular structure and dynamics in the liquid and may explain its relatively high viscosity and some of its other specific properties. In particular, the effect of the hydrogen bonds on the reorientational dynamics of [BMIM]PF6 was investigated.

    9. Mesostructured Dye-Doped Titanium Dioxide for Micro-Optoelectronic Applications (pages 595–603)

      Robert Vogel, Paul Meredith, Indriana Kartini, Michael Harvey, Jamie D. Riches, Alexis Bishop, Norman Heckenberg, Matt Trau and Halina Rubinsztein-Dunlop

      Article first published online: 6 JUN 2003 | DOI: 10.1002/cphc.200200494

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      Spontaneous emission. Mesostructured titanium dioxide thin films were doped with the dye Rhodamine 6G, and patterned into microcavities. The material displayed amplified spontaneous emission (see picture), and shows great promise for solid-state dye microlaser and other optoelectronic applications.

    10. Surface Photovoltage, Luminescence, and Cyclic Voltammetry on the First Series of Lanthanide(III) Tetrabenzoporphyrin Liquid Crystals (pages 605–608)

      Ming-Hui Qi and Guo-Fa Liu

      Article first published online: 6 JUN 2003 | DOI: 10.1002/cphc.200200600

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      Lighting up. The first lanthanide(III) benzoporphyrin liquid crystals (see picture) were prepared, and the application of cyclic voltammetry and surface photovoltage and luminescence spectroscopy in the analysis of hexagonal liquid crystals was demonstrated. The complex with n=13 exhibits phosphorescence at low temperature. The photoelectric properties of the liquid-crystalline porphyrin aggregates suggest potential applications in electro-optical data storage.

    11. Discrimination of σ-Bond Metathesis Pathways in H/D Exchange Reactions on [([TRIPLE BOND]SiO)3Zr[BOND]H]: A Density Functional Theory Study (pages 608–611)

      Christophe Copéret, Annie Grouiller, Jean-Marie Basset and Henry Chermette

      Article first published online: 6 JUN 2003 | DOI: 10.1002/cphc.200200495

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      Chemical switch-a-roo: H/D exchange in methane/hydrogen mixtures on silica-supported zirconium hydride proceeds via a two-step process and a single four-centred σ-bond metathesis transition state (TS3; see graphic).

    12. Comparison between MCM-41 and Periodic Mesoporous Organosilica: Charge-Transfer Donor-Viologen Complexes as Probes (pages 612–617)

      Mercedes Álvaro, Belén Ferrer, Vicente Fornés and Hermenegildo García

      Article first published online: 6 JUN 2003 | DOI: 10.1002/cphc.200200580

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      A radical result. Viologen embedded in the walls of the mesoporous silica (see graphic) forms less stable charge-transfer complexes than when adsorbed onto MCM-41 and with a red-shifted λmax. The as-synthesized material thermally generates the corresponding radical cation.

    13. “Dark” Photocatalysis: The Degradation of Organic Molecules Anchored to Dark Microdomains of Titanium Dioxide (pages 617–620)

      Hossam Haick and Yaron Paz

      Article first published online: 6 JUN 2003 | DOI: 10.1002/cphc.200200622

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      Join the dark side: Titanium dioxide is widely used as a photocatalyst for the degradation of many contaminants in air, in water and on solid surfaces. By anchoring self-assembled monolayers onto “dark” microdomains of titanium dioxide (see picture) and measuring their photodegradation kinetics, it is shown that molecules located on dark areas at the vicinity of illuminated domains of titanium dioxide might be prone to an oxidizing attack by oxidizing species that out-diffuse from the illuminated areas.

    14. Mechanism of Lck Recruitment to the T-Cell Receptor Cluster as Studied by Single-Molecule-Fluorescence Video Imaging (pages 620–626)

      Hiroshi Ike, Atsushi Kosugi, Akiko Kato, Ryota Iino, Hidemi Hirano, Takahiro Fujiwara, Ken Ritchie and Akihiro Kusumi

      Article first published online: 6 JUN 2003 | DOI: 10.1002/cphc.200300670

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      Molecular movies: The Src-family kinase Lck is recruited to the site of Tcell receptor (TCR) clustering at very early stages after TCR engagement. The authors have investigated the mechanism of Lck recruitment to the TCR cluster by monitoring the movement of single molecules of Lck and its N-terminal ten amino acid sequence (N10; for experimental procedure see picture), both fused with green fluorescent protein (GFP) and expressed in the Jurkat Tcell line. Single-molecule observations revealed that neither Lck- nor N10-GFP underwent directed movement toward the cluster, but they both underwent apparent short-term simple Brownian diffusion.

    15. Bis(μ-oxo)dicopper as Key Intermediate in the Catalytic Decomposition of Nitric Oxide (pages 626–630)

      Marijke H. Groothaert, Kristof Lievens, Jeroen A. van Bokhoven, Andrea A. Battiston, Bert M. Weckhuysen, Kristine Pierloot and Robert A. Schoonheydt

      Article first published online: 6 JUN 2003 | DOI: 10.1002/cphc.200300746

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      Oxygen transport: Here, the authors present the elucidation of the NO decomposition activity of Cu-ZSM-5 (see picture) by identifying the bis(μ-oxo)dicopper species as the key intermediate that allows the smooth formation and desorption of O2. Its isomerized (μ-η22-peroxo)dicopper core is present in natural enzymes, where it is responsible for dioxygen transport and selective oxidation catalysis, similar to the catalytic roles played by Cu-ZSM-5.

    16. Optical Levitation of Single Microdroplets at Temperatures Down to 180 K (pages 630–638)

      C. Mund and R. Zellner

      Article first published online: 6 JUN 2003 | DOI: 10.1002/cphc.200200398

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      A little light levitation: Optically transparent microdroplets can be levitated by means of the photon pressure exerted by a slightly focussed laser beam. The picture shows the forces operating on a particle during this process. The operation of this levitation techniques is reviewed on the basis of generalized Lorenz–Mie theory. The behaviour of levitated microparticles with respect to changes in composition and size can be investigated by Raman and Mie scattering. The feasibility of this technique for levitation studies down to 180 K is demonstrated.

    17. Raman- and Mie-Spectroscopic Studies of the Cooling Behaviour of Levitated, Single Sulfuric Acid/H2O Microdroplets (pages 638–645)

      C. Mund and R. Zellner

      Article first published online: 6 JUN 2003 | DOI: 10.1002/cphc.200200629

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      Acidic aerosols aloft: The behaviour of supercooled, single sulfuric acid/H2O microdroplets with respect to concentration and temperature relaxation can be investigated with Raman- and Mie-scattering techniques upon scavenging of such particles in a vertical laser beam. The rates of relaxation by water evaporation prevent such particles from homogeneous freezing forming either H2O, ice or sulfuric acid trihydrate (see picture). Instead thermodynamically stable solutions are formed.

    18. Book Review: Principles of Thermodynamics by Myron Kaufman (page 648)

      Ralf Ludwig

      Article first published online: 6 JUN 2003 | DOI: 10.1002/cphc.200390082

    19. Preview: ChemPhysChem 6/2003 (page 650)

      Article first published online: 6 JUN 2003 | DOI: 10.1002/cphc.200390083