Browsing by Author "Koch, P."

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    Doped dialkylated phenazines : a novel series of highly conducting organic solids
    (1981) Dietz, Klaus; Flandrois, Serge; Keller, Heimo J.; Koch, P.; Queckbörner, Jobst G.; Schweitzer, Dieter
    Doping dimethylphenazine (M2P)-TCNQ and diethylphenazine (E2P)-TCNQ with phenazine gave rise to new conducting compounds with segregated stacks : (M2P)0.5 (P)0,5 TCNQ and (E2P)0,55 (P)0,45 TCNQ. The room temperature electrical conductivities are in the range 10-100 Ω-1 cm-1 for (1) and 1-10 Ω-1cm-1 for (2). The paramagnetism of both compounds could be separated into contributions from TCNQ and Phenazine stacks. The structural electrical and magnetic similarities of (1) with the well-known N-methylphenazinium (NMP)-TCNQ led to a reexamination of its magnetic properties. It was shown that an estimate of the charge transfer can be obtained from the temperature dependence of the magnetic susceptibility.
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    Electrochemical synthesis of new one-dimensional metals: radical salts of perylene
    (1981) Keller, Heimo J.; Nöthe, Dietrich; Pritzkow, Hans; Wehe, Dieter; Werner, M.; Harms, Ralf H.; Koch, P.; Schweitzer, Dieter
    The electrochemical synthesis of four highly conducting peryleniumyl salts is reported. The temperature dependence of the conductivity has been measured and exhibits a metallic regime between 200-300 K. The crystal structures of two of the compounds have been solved.
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    Electrochemically generated peryleniumyl-hexafluorophosphate and hexafluoroarsenate : new one-dimensional metals
    (1980) Keller, Heimo J.; Nöthe, Dietrich; Pritzkow, Hans; Wehe, Dieter; Werner, M.; Koch, P.; Schweitzer, Dieter
    Compounds of stoichiometry (pe)2(PF6)1.1x times 0.8CH2Cl2(1) (pe = perylene), (pe)2(AsF6)1.1 timesx 0.7 CH2Cl2 (2), (pe)2(PF6)1.4 times 0.6 THF (3), (pe)2(AsF6)1.5x times 0.5 THF (4) and (pe)3(SbF6)2 times 0.75 CH2Cl2 (5) have been obtained as crystalline samples by electrochemical deposition from CH2Cl2 [(1), (2) and (5)] or from THF [(3) and (4)] solutions of perylene, containing the appropriate counterion. The three compounds (1)-(3) crystallize in isomorphous orthorhombic lattices. (1) forms black needles: space group Pnmn with a = 4.285 Aring, b = 12.915 Aring and c = 14.033 Aring, z = 1. (2) gives black needles, orthorhombic space group Pnmn with a = 4.294 Aring, b = 13.077 Aring, and c = 14.132 Aring, z = 1. The structures of (1) and (2) were solved by direct methods and refined by least squares to final R = 0.148 and R = 0.088 based on 476 and 322 observed reflections. The perylene forms segregated stacks in direction of the a-axis with interplanar distances of 3.40 Aring and an angle of 37.7° between the bc-plane and the perylene. The channels between the segregated stacks are filled by anions and solvent molecules. The d.c. conductivities (four probe measurements) of (1)-(4) fall in the range of 70-1200Ω-1. cm-1 at room temperature. The conductivities show a metallic regime down to about 200°K and drop off below that temperature.
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    Highly conducting perylene radical salts
    (1982) Koch, P.; Schweitzer, Dieter; Harms, Ralf H.; Keller, Heimo J.; Schäfer, Herbert; Helberg, Hans W.; Wilckens, Rudolf; Geserich, Hans Peter; Ruppel, Wolfgang
    Temperature dependent dc and microwave conductivity data together with EPR and optical reflectance measurements on the "mixed" system (pe)2(ASF6)0,75(PF6)0,35 times 0,85 CH2Cl2 are described. The data prove metallic behaviour of this organic solid down to 200 K.
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    Spectral reflectance of the one-dimensional organic metals (perylene)2(PF6)1.1 × 0.8CH2Cl2 and (perylene)2(AsF6)1.1 × 0.7CH2Cl2
    (1982) Wilckens, Rudolf; Geserich, Hans Peter; Ruppel, Wolfgang; Koch, P.; Schweitzer, Dieter; Keller, Heimo J.
    We report on the optical reflectance of (perylene)2(PF6)1.1 × 0.8CH2Cl2 and (perylene)2(AsF6)1.1 × 0.7CH2Cl2 single crystals in the energy range from 0.25 to 4 eV. For light polarized perpendicular to the molecular stacks the crystals exhibit the optical behaviour of an insulating molecular crystals, whereas for light polarized parallel to the stacks a pronounced plasma edge at hω=0,9eV image is observed. The experimental data were analyzed by a Lorentz-Drude model in order to determine the electrical conductivity, the carrier concentration, the effective mass, the collision time, the band width, and the Fermi vector of the crystals.