ChemPhysChem

Cover image for Vol. 5 Issue 9

September 20, 2004

Volume 5, Issue 9

Pages 1257–1454

    1. Cover Picture: Photostability of Isolated and Paired Nucleobases: N[BOND]H Dissociation of Adenine and Hydrogen Transfer in its Base Pairs Examined by Laser Spectroscopy (ChemPhysChem 9/2004) (page 1257)

      Isabel Hünig, Christian Plützer, Kai A. Seefeld, Dennis Löwenich, Michael Nispel and Karl Kleinermanns

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200490047

      The cover picture shows an artist's view of the interaction of the DNA α helix with light. Prebiotic chemistry supposedly happened under conditions of intense short wavelength radiation without UV-absorbing oxygen or ozone layer. UV photostability may have been an important factor for the evolutionary selection of the DNA bases besides their capability to form strong hydrogen bonds. The apparent photostability of the genetic code has been ascribed to fast internal conversion of the electronically excited DNA bases to the electronic ground state via doorway states. The results presented on page 1427 by Hünig et al. point to N[BOND]H dislocation as important pathway to convert photoexcitation of DNA to innoxious heat in the condensed phase.

    2. Graphical Abstract: ChemPhysChem 9/2004 (pages 1259–1267)

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200490048

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      Pseudorotation of Natural and Chemically Modified Biological Phosphoranes: Implications for RNA Catalysis (page 1266)

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

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200490049

    4. Photonic Crystals—A Step towards Integrated Circuits for Photonics (pages 1268–1283)

      Lars Thylén, Min Qiu and Srinivasan Anand

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200301075

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      Light-controlling crystals: The authors present an in-depth Review of the field of photonic crystals (see picture), including the basics of photonic crystal structures and the state-of-the-art in photonic crystal fabrication.

    5. Ultrafast Electron Dynamics in Metals (pages 1284–1300)

      Jose M. Pitarke, Vladlen P. Zhukov, Robert Keyling, Evgueni V. Chulkov and Pedro M. Echenique

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200301222

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      Hot electrons: Rates and branching ratios of ultrafast chemical reactions at metal surfaces are governed by the dynamics of electronically excited hot electrons. This Review focuses on the theoretical description of the finite lifetime of these hot electrons, which mainly originates in the inelastic scattering of the excited quasiparticle with occupied states below the Fermi level of the solid (see graphic).

    6. Molecular Origins of the Remarkable Chiral Sensitivity of Second-Order Nonlinear Optics (pages 1301–1310)

      Garth J. Simpson

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200300959

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      Chirality goes simple: The molecular and macromolecular origins of the remarkable chiral responses in second harmonic generation and sum-frequency generation (see graphic) are discussed. Although the chiral activity originates from a potentially complex array of interactions, remarkably simple physical models often capture the essence of the driving interactions.

    7. Optical Spectroscopy of Biomolecular Dynamics (pages 1311–1313)

      Peter Vöhringer and Gilad Haran

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200400287

      Of visible interest: At the Minerva-Gentner Symposium on Optical Spectroscopy of Biomolecular Dynamics, which took place between 21st and 25th March 2004 at Banz, Germany, scientists from many disciplines came together to compare the study of single molecules to that of ensembles. Fluorescent proteins, time-resolved IR, and protein folding dynamics were among the main topics discussed.

    8. Femtosecond Pump-Probe Measurements of Solvation by Hydrogen-Bonding Interactions (pages 1315–1327)

      Ehud Pines, Dina Pines, Ying-Zhong Ma and Graham R. Fleming

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200301004

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      Seeing hydrogen bonds in action: The acidity of a strong photoacid forming well-defined hydrogen-bonding complexes in solution was optically switched by femtosecond-pulse excitation. By reconstructing the temporal shift of the transient absorption band of the photoacid (see graphic) the authors were able to identify a sub-100 femtosecond solvation-like response in the hydrogen-bonding complex.

    9. The Effect of Ge Incorporation on the Brønsted Acidity of ZSM-5 (pages 1328–1335)

      Leon G. A. van de Water, Martijn A. Zwijnenburg, Willem G. Sloof, Jan C. van der Waal, Jacobus C. Jansen and Thomas Maschmeyer

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200301037

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      Acidic strength of doped zeolites: The effect of the isomorphous substitution of some of the Si atoms in ZSM-5 by Ge atoms on the Brønsted acid strength has been investigated by DFT calculations on zeolite cluster models (see picture) and by 31P NMR and X-ray photoelectron spectroscopy (XPS) studies of ZSM-5 and Ge-ZSM-5 samples.

    10. Theoretical Study of the Reactions of CF3OCHF2 with the Hydroxyl Radical and the Chlorine Atom (pages 1336–1344)

      Jia-yan Wu, Jing-yao Liu, Ze-sheng Li and Chia-chung Sun

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200400010

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      Radical kinetics: The graphic shows the rate constants calculated by canonical variational transition-state theory with small-curvature tunnelling (CVT/SCT) at the G3(MP2)//B3LYP/6–311G(d,p) level for the reaction CF3OCHF2+OH[RIGHTWARDS ARROW]CF3OCF2+H2O (k1), and the reaction CF3OCHF2+Cl[RIGHTWARDS ARROW]CF3OCF2+HCl (k2), together with the available experimental values as inverse functions of the temperature.

    11. A Computational Investigation of HCN2+ Isomeric Structures: Implications for the Chemistry of Titan's Atmosphere (pages 1345–1351)

      Paola Antoniotti, Stefano Borocci, Nicoletta Bronzolino and Felice Grandinetti

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200400028

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      Traces in space: In Titan's atmosphere, the neutralisation of HCN2+ isomers may lead to the presence of different trace neutral molecules. The authors investigate the structure and stability of various HCN2+ isomeric structures (see graphic) by ab initio calculations.

    12. The Origin of Aromaticity: Important Role of the Sigma Framework in Benzene (pages 1352–1364)

      Borislav Kovačević, Danijela Barić, Zvonimir B. Maksić and Thomas Müller

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200400061

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      Addressing the physical nature of aromaticity: The extrinsic aromaticity of benzene, defined by means of homodesmic reactions involving linear zig-zag polyenes (e.g., benzene reacting with three ethylene molecules to form three molecules of 1,3-butadiene) is a consequence of its σ-electron framework (top), as conclusively shown by a detailed ab initio analysis. In contrast, the π-electron framework (bottom) prefers the open-chain linear polyenes.

    13. The Diels–Alder Reaction of Ethene and 1,3-Butadiene: An Extended Multireference ab initio Investigation (pages 1365–1371)

      Hans Lischka, Elizete Ventura and Michal Dallos

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200400104

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      The Diels–Alder reaction of butadiene and ethene has been revisited using highly correlated multireference quantum chemical methods. The Figure shows a potential energy curve for the rotation of the ethene subunit around the carbon–carbon bond connecting to butadiene. The lowest energy point on this curve, the gauche-in structure, does not correspond to an energy minimum, but connects without an energy barrier to cyclohexene.

    14. Quantum Dynamics Study of the Excited-State Double-Proton Transfer in 2,2′-Bipyridyl-3,3′-diol (pages 1372–1378)

      Ricard Gelabert, Miquel Moreno and José M. Lluch

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200400078

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      Slowing down an ultrafast process: The double-proton transfer process in 2,2′-bipyridyl-3,3′-diol in the first excited singlet state is a branched process with very different time scales for each mechanism (see Figure). A quantum dynamics study on a time-dependent density functional theory (TDDFT) model surface is used to find an explanation to this behavior.

    15. Mechanism and Kinetics of the Reaction of OH Radicals with Glyoxal and Methylglyoxal: A Quantum Chemistry+CVT/SCT Approach (pages 1379–1388)

      Annia Galano, J. Raúl Alvarez-Idaboy, Ma. Esther Ruiz-Santoyo and Annik Vivier-Bunge

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200400127

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      Working for the troposphere: The OH abstraction reactions from glyoxal and methylglyoxal were modeled according to a complex mechanism that involves the formation of a reactant complex (represented here by RC-G). The results obtained in this work may help to improve air-quality models.

    16. Coherent Oscillation and Ultrafast Internal Conversion of Tetrafluoroethene after Excitation at 197 nm (pages 1389–1397)

      Sergei A. Trushin, Sébastien Sorgues, Werner Fuß and Wolfram E. Schmid

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200400218

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      Living fast: Why is fluorocarbon chemistry so different from hydrocarbon chemistry? Photochemical and thermal C[DOUBLE BOND]C dissociation of C2F4 can be understood on the basis of potential energy surfaces (such as that shown) inferred from a femtosecond pump–probe experiment.

    17. Local Dense Structural Heterogeneities in Liquid Water from Ambient to 300 MPa Pressure: Evidence for Multiple Liquid–Liquid Transitions (pages 1398–1404)

      Dimitri E. Khoshtariya, Achim Zahl, Tina D. Dolidze, Anton Neubrand and Rudi van Eldik

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200400219

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      Don't crack under pressure! The graphic shows a water cubic octamer (in red) fitted to the hexagonal quasicrystalline (Ih icelike) lattice (in black). Note an almost ideal compatibility between the basic (“water II”) and the pressure-induced (dense) substructures.

    18. Fabrication, Characterisation and Voltammetric Studies of Gold Amalgam Nanoparticle Modified Electrodes (pages 1405–1410)

      Christine M. Welch, Olga Nekrassova, Xuan Dai, Michael E. Hyde and Richard G. Compton

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200400263

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      Gold improves sensitivity: Gold and gold amalgam nanoparticles on glassy carbon electrodes were prepared and studied; these modified electrode demonstrate a unique voltammetric behaviour (see voltammogram: gold macroelectrode - - - - and gold nanoparticle electrode —) and can be applied for electroanalysis when enhanced sensitivity is crucial.

    19. Structural Phase Transitions in Heavy Alkali Metals Under Pressure (pages 1411–1415)

      Jorge M. Osorio-Guillén, Rajeev Ahuja and Börje Johansson

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200400292

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      Complex crystal structures: Detailed theoretical studies support the experimental observations that suggest that the Cs II[RIGHTWARDS ARROW]Cs III transition involves a crystallographic phase transformation. The classical isostructural phase transformation in Cs under pressure can now be ruled out. The picture shows the structure of Cs III along different crystal axes.

    20. Surface Chemistry and Structure of Purified, Ozonized, Multiwalled Carbon Nanotubes Probed by NEXAFS and Vibrational Spectroscopies (pages 1416–1422)

      Sarbajit Banerjee, Tirandai Hemraj-Benny, Mahalingam Balasubramanian, Daniel A. Fischer, James A. Misewich and Stanislaus S. Wong

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200400122

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      Probing tubes: Near-edge X-Ray absorption fine structure (NEXAFS) spectroscopy is a means of probing chemical composition and electronic structure in functionalized multiwalled carbon nanotubes (see graphic).

    21. Femtosecond Time-Resolved Hydrogen-Atom Elimination from Photoexcited Pyrrole Molecules (pages 1423–1427)

      H. Lippert, H.-H. Ritze, I. V. Hertel and W. Radloff

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200400079

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      Ultrafast N[BOND]H breaking in pyrrole: Using resonance-enhanced multiphoton ionization, hydrogen-atom formation by photodissociation of pyrrole molecules was monitored with femtosecond time resolution. The results indicated two fast time constants (see picture), which were interpreted within the framework of a nonradiative decay mechanism for aromatic biomolecules.

    22. Photostability of Isolated and Paired Nucleobases: N[BOND]H Dissociation of Adenine and Hydrogen Transfer in its Base Pairs Examined by Laser Spectroscopy (pages 1427–1431)

      Isabel Hünig, Christian Plützer, Kai A. Seefeld, Dennis Löwenich, Michael Nispel and Karl Kleinermanns

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200400142

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      A stable genetic code: The authors present the first spectroscopic proof of UV-light-induced N[BOND]H dissociation in the nucleobase adenine and hydrogen transfer in its dimer in the gas phase (see picture). The N[BOND]H dissociation is investigated by UV photolysis of adenine followed by 2+1 resonant multiphoton ionisation of neutral hydrogen-atom photoproducts under collisionless conditions.

    23. Spontaneous Change of Physical State from Hydrogels to Crystalline Precipitates during Poly-pseudorotaxane Formation (pages 1431–1434)

      Hak Soo Choi, Tooru Ooya, Shintaro Sasaki, Nobuhiko Yui, Motoichi Kurisawa, Hiroshi Uyama and Shiro Kobayashi

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200400172

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      Spontaneous change: Hydrogels spontaneously changed to crystalline precipitates through heating and cooling processes in linear polyethylenimine-based inclusion complexes with α-cyclodextrins (see graphic).

    24. Near-Infrared Electroluminescence from HgTe Nanocrystals (pages 1435–1438)

      Dmitry S. Koktysh, Nikolai Gaponik, Martin Reufer, Jana Crewett, Ullrich Scherf, Alexander Eychmüller, John M. Lupton, Andrey L. Rogach and Jochen Feldmann

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200400178

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      Colloidal semiconductor nanocrystals: We present a hybrid inorganic–organic near-infrared light-emitting device (see picture), which comprises a blend of a blue–green emitting, hole-conducting conjugated polymer, methyl-substituted ladder-type poly(para-phenylene), and HgTe nanocrystals. The demonstrated device emits at the telecommunications wavelength of 1.3 μm, while the exceptionally broad spectral range covered by HgTe nanocrystals allows further spectral tunability in the near-infrared region.

    25. Theoretical Design of Substituted Tetrathia-[7]-Helicenes with Large Second-Order Nonlinear Optical Responses (pages 1438–1442)

      Benoît Champagne, Jean-Marie André, Edith Botek, Emanuela Licandro, Stefano Maiorana, Alberto Bossi, Koen Clays and André Persoons

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200400225

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      Increasing response: Semiempirical calculations show that substituting tetrathia-[7]-helicene in positions 7 and 8 (see graphic) as well as in positions 2 and 13 by adequate donor/acceptor pairs can lead to a substantial increase of the second-order nonlinear optical response.

    26. Enhanced Molecular Multipole Moments and Solvent Structure in Supercritical Carbon Dioxide (pages 1442–1445)

      Moumita Saharay and Sundaram Balasubramanian

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200400252

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      Understanding the green solvent: The solvent structure and molecular electrostatic multipole moments of supercritical carbon dioxide (scCO2) were studied using ab initio molecular dynamics simulations. Blue, cyan, and orange (see graphic) represent the increasing probability of finding an oxygen atom, which belongs to a neighboring molecule, in the first coordination shell of CO2.

      Corrected by:

      Corrigendum: Enhanced Molecular Multipole Moments and Solvent Structure in Supercritical Carbon Dioxide

      Vol. 7, Issue 6, 1167, Article first published online: 31 MAY 2006

    27. Isolation and Characterisation of Two Sc3N@C80 Isomers (pages 1445–1449)

      Matthias Krause and Lothar Dunsch

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200400085

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      Endohedral cluster fullerenes: Two cage isomers of endohedral cluster fullerene Sc3N@C80 (I and II) were isolated and characterised by optical and vibrational spectroscopy for the first time. Both isomers are large energy gap structures. Even the minor isomer of D5h cage symmetry contains a trigonal planar Sc3N cluster in a C80 carbon cage, and no pyramidal cluster, as could be intuitively expected (see picture).

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      Preview: ChemPhysChem 9/2004 (page 1454)

      Article first published online: 17 SEP 2004 | DOI: 10.1002/cphc.200490050

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