Browsing by Author "Heid, Rolf"

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    The double-stack structure of di(3,4-ethylenedithio-3',4'-dimethyl-2,2',5,5'-tetrathiafulvalenium)perchlorate, (DIMET)2ClO4
    (1987) Endres, Helmut; Heid, Rolf; Keller, Heimo J.; Heinen, Ilsabe; Schweitzer, Dieter
    2C10H10S6 1/2+.ClO-4 , M r= 744·62, triclinic, PI, α=7·000 (2), b =7·824 (3), c = 27·010 (14) A, α = 88· 10 (4), β= 89·02 (4), Y = 74· 58 (3)°, V = 1425 A 3, Z=2, Dx=1·73gcm-3, λ( MoKa) = 0·7107 A, μ= 10·1 cm-1, F(000) = 762, room temperature, final R = 0.063 for 3076 observed independent reflections. Two crystallographically independent DIMET molecules each with an average charge of ½+ form stacks, which run nearly perpendicularly to one another. Within each stack, two different interplanar spacings between adjacent parallel molecules are found. These overlap patterns are similar to those found in tetrahydrofuran solvate. The stacks are arranged side by side perpendicular to the long molecular axis to give a sheet-like arrangement.
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    Radical cation salts of an unsymmetrical BEDT-TTF derivative: DIMET
    (1987) Bender, Klaus; Endres, Helmut; Gärtner, Stephan; Gogu, Emil; Heid, Rolf; Heinen, Ilsabe; Keller, Heimo J.; Kraatz, Andrea; Schweitzer, Dieter
    A surprising fact in the structures of the organic superconductors (TMTSF)2 Cl04 and -β-(BEDT-TTF)2X (X=I3-, IBr2- and AuI2-) is that there exists a slight dimerisation of the donor molecules within the stacks of these radical cation salts. Therefore, the question arises whether a more pronounced dimerisation in organic radical salts of this type leads to stronger intra- and interstack interactions and to stronger couplings between the unpaired electrons. This might result in an increase of the transition temperature to superconductivity. A step in this direction is the preparation of "unsymmetrical" donors like DIMET, which was synthesized recently. This new donor was electrocrystallized by us in different solvents using tetrabutylammonium salts of various anions like ClO4-, ReO4-, NO3-, I3-, (AuI2)-, PF6-, ASF6- and SbF6- as electrolytes. With all these anions radical salts were obtained and in some cases even several crystallographic different phases.
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    Radical cation salts of an unsymmetrical BEDT-TTF derivative: molecular structure and physical properties of (DIMET)2ClO4xTHF
    (1985) Heid, Rolf; Endres, Helmut; Keller, Heimo J.; Gogu, Emil; Heinen, Ilsabe; Bender, Klaus; Schweitzer, Dieter
    Sheets of cations with an average charge of 1/2+ are separated by sheets of anions and THF solvent molecules. Intermolecular S···S contacts result in two-dimensional physical properties. Electrical conductivity and thermopower measurements indicate two broad phase transitions at around 200 K and 80 K.
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    Radical cation salts of BEDT-TTF and an unsymmetrical BEDT-TTF derivative
    (1986) Schweitzer, Dieter; Bender, Klaus; Endres, Helmut; Gärtner, Stephan; Heid, Rolf; Heinen, Ilsabe; Keller, Heimo J.; Weber, Angelika; Weger, Meir
    Investigations of several BEDT-TTF and DIMET radical salts are presented. Measurements on β-(BEDT-TTF)2IAuI crystals show that their conducting and superconducting properties might vary strongly depending on the decomposition of (IAuI)− anions during the electrochemical process.