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Publication Type: search.filters.UBSTyp.KonferenzbeitragSubject: search.filters.subject.530Author: search.filters.author.Schweitzer, DieterStart date: 1980End date: 1989

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Now showing 1 - 8 of 8
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    Excited electronic states of flavin-containing coenzyme models
    (1988) Gückel, Friedemann; Schweitzer, Dieter; Becker, Katja; Schirmer, Rolf Heiner; Zipplies, Matthias F.; Staab, Heinz A.
    In order to gain further insight into the physical basis of flavin-catalyzed reactions, the interactions of a flavin with a second flavin and with other aromatic ring systems were studied. For this purpose compounds through 1 were synthesized These compounds contain the interacting units in defined geometric orientation. A monomeric flavin and glutathione reductase a flavoenzyme of known active-site chemistry, were included as reference molecules. The present report deals with excited triplet states of the flavin compounds as studied by optical spectroscopy and optically detected magnetic resonances (ODMR) at 1.3K.
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    Metallic coordination polymers using CS2 as starting material
    (1987) Keller, Heimo J.; Klutz, Thomas; Münstedt, Helmut; Renner, Gerd; Schweitzer, Dieter
    Organic polymers with "metallic" properties have found widespread interest during the last few years. Acetylene and aniline as well as different nitrogen and sulfur heterocycles have been used as starting materials. One main problem hampering the technical application of these solids up to now is their environmental and thermal instability. Therefore, we introduced metal ions to stabilize polymeric backbones with high electrical conductivity. Because of the enormous coordination ability of sulfur to many transition metal ions we decided to use a polymeric carbon-sulfur backbone.
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    ODMR of triplet states of organic electron donors
    (1986) Grimm, Hans; Schweitzer, Dieter; Hausser, Karl H.; Keller, Heimo J.
    Energies of the first excited triplet states and triplet zero field splitting parameters /D/ and /E/ of several organic donors - usually used for the preparation of organic metals and superconductors - are reported.
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    BEDT-TTF radical salts: organic metals and superconductors
    (1987) Schweitzer, Dieter
    A review of the structural, electronic and superconducting properties of some BEDT-TTF-radical salts is given.
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    Spectroscopic properties of kekulene
    (1981) Schweitzer, Dieter; Hausser, Karl H.; Diederich, Francois; Staab, Heinz A.; Vogler, Helmut
    Kekulene [1,2] is the first example of a new class of aromatic compounds in which the annelation of six membered rings leads to a cyclic system enclosing a cavity with hydrogen atoms.
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    Molecular metals and superconductors: BEDT-TTF radical salts
    (1987) Schweitzer, Dieter; Keller, Heimo J.
    The first discovery of superconductivity in an organic metal - in the radical salts of TMTSF (tetramethyltetraselenafulvalene) - under pressure and ambient pressure has demonstrated that in addition to the usual intrastack contacts between the donor molecules in quasi one dimensional metals intermolecular contacts between molecules in neighbouring stacks are important. These interstack contacts result in a less pronounced one dimensional electronic behaviour leading to a stabilization of the metallic character down to low temperatures.
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    Existence of two phases in β-(BEDT-TTF)2I3: proof by resonance Raman spectroscopy
    (1987) Swietlik, Roman; Schweitzer, Dieter; Keller, Heimo J.
    Among various organic metals and superconductors based on the BEDT-TTF molecule [bis(ethylenedithiololtetrathiafulvalene] and different polyhalide anions the most intensively studied is β-(BEDT-TTF)2I3. Partially it is caused by the fact that these crystals exhibit the superconductivity with the highest critical temperature reported for organic materials, but the main reason of this interest is the existence of two superconducting states in these crystals. Under ambient pressure the superconductivity in β-(BEDT-TTF)2I3 is observed below Tc≈1,3K1-4 (low-Tc phase) but after a particular pressure-temperature cycling procedure the superconductivity can be stabilized under ambient pressure at Tc≈8,1K5,6(high-Tc phase). α-(BEDT-TTF)2I3 is another modification of the salt formed hetween BEDT-TTF and I3-; at ambient pressure α-phase crystals undergo a metal-insulator phase transition at T=135K 4,7. Recently, it was discovered that by tempering α-phase crystals at about 75°C for several days crystals can be obtained with similar properties as the high-Tc state of the β-crystals 8,9 (these crystals are further denoted as α t-(BEDT-TTF)2I3).
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    Electronic interactions between polycyclic arenes in cyclophanes
    (1988) Haenel, Matthias; Schweitzer, Dieter
    The π-π interaction between polycyclic arenes and the effects of orientation were studied in [2.2]-, [3.3]-, and [3.2]naphthalenophanes, [2]naphthaleno[2]paracyclophanes, and syn- and anti[2.2](2,7)fluorenophane by electron absorption and emission spectroscopy as well as by optically detected magnetic resonance (ODMR) of the excited triplet state. The π-π interaction in the excited singlet and triplet state was found to be highest if a maximal number of sixmembered rings of the interacting arenes in a parallel orientation are completely eclipsed. Similarly, the π-π interaction between the nonbonding nitrogen electron pair and the aromatic π electrons was investigated in isomeric etheno-bridged naphthalenopyridinophanes and an anthracenopyridinophane; in these pyridinophanes, the pyridine rings are fixed perpendicularly above different sites of the naphthalene and anthracene units, respectively.