Universität Stuttgart
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Item Open Access 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.Item Open Access Electronic spectra and triplet state properties of superphane(1986) Schweitzer, Dieter; Hausser, Karl H.; Vogler, Helmut; Staab, Heinz A.; Boekelheide, VirgilThe emission and the zero-field splitting parameters D and E of the superphane 1 and the [25](1,2,3,4,5)-cyclophane 2 are investigated. The large number of six and five methylene bridges, respectively, leads to a more rigid molecular frame and to a smaller transanular distance as compared to other [2.2]cyclophanes. The experimental results exhibit characteristics features which are due to these unusual properties; they are discussed and compared with semi-empirical Π-electron calculations.Item Open Access Spectroscopic properties of kekulene(1981) Schweitzer, Dieter; Hausser, Karl H.; Diederich, Francois; Staab, Heinz A.; Vogler, HelmutKekulene [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.Item Open Access [3.3]- and [4.4](2,7)pyrenophanes as excimer models : synthesis, molecular structure, and spectroscopic properties(1984) Staab, Heinz A.; Riegler, Norbert; Diederich, Francois; Krieger, Claus; Schweitzer, DieterAs excimer models the [3.3]- and [4.4]pyrenophanes 1 and 2 were synthesized. As the key precursor for the synthesis of 1 the octahydro-dithia[4.4]pyrenophane 9 was obtained by cyclisation of 4 and 8, the syntheses of which are described. Disulfone 10, derived from 9, on vapour-phase pyrolysis yielded 11 which by dehydrogenation was converted into 1. In an analogous route 2 was obtained via 16, 17, and 18 starting from 4 and 15 (prepared in the reaction sequence 12 - 13 - 14 - 15). - The molecular structures of 1 and 2, determined by X-ray structure analyses, are discussed with regard to transanular distances and deviations from planarity of the pyrene units. - Absorption spectra of 1 and 2 are discussed with reference to transanular interactions. The fluorescence emissions of 1 and 2 are found to be 'excimer-like'. Results obtained by ODMR measurements of 1 are reported.Item Open Access Optical detection of magnetic resonance (ODMR) of triple-layered phanes(1981) Melzer, Guenter; Schweitzer, Dieter; Hausser, Karl H.; Staab, Heinz A.; Zapf, Udo-Item Open Access Electronic properties of [3.3]TTF-phan TCNQ-crystals(1982) Schweitzer, Dieter; Taopen, Chu; Krieger, Claus; Staab, Heinz A.-Item Open Access [2.2]- and [3.3]tetrathiafulvalenophanes(1980) Ippen, Joachim; Chu, Tao-pen; Starker, Barbara; Schweitzer, Dieter; Staab, Heinz A.In the "metallic" conducting 1:1 complex of tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ), donor and acceptor molecules form separate stacks in the crystal. In order to enforce other TTF/TCNQ arrangements by altering the molecular architecture the phane-like bridged TTF-paracyclophanes (1), n = 3, and (2) were first synthesized. To do this a novel reaction sequence had to be developed which also facilitated synthesis of the tetrathiafulvalenophanes (3)/(4) (and the corresponding [2.2]-derivatives). (3)/(4) and TCNQ form a 1:4 complex having a conductivity of σ = 5 × 10−3 to 10−2 [Ω cm]−1 (single crystal, long axis, 300 K).Item Open Access Molecular structure and spectroscopic properties of Kekulene(1979) Krieger, Claus; Diederich, Francois; Schweitzer, Dieter; Staab, Heinz A.Considerable bond localization has been detected in kekulene(1) by X-ray structure analysis: only every second ring is "aromatic". This initially surprising result is in accord with various spectroscopic properties of (1).Item Open Access Molekülstruktur und spektroskopische Eigenschaften des Kekulens(1979) Krieger, Claus; Diederich, Francois; Schweitzer, Dieter; Staab, Heinz A.Beträchtliche Bindungslokalisation im Kekulen (1) wurde durch Röntgen-Strukturanalyse nachgewiesen: Nur jeder zweite Ring ist "aromatisch". Dieser zunächst überraschende Befund ist mit einigen spektroskopischen Eigenschaften von (1) in Einklang.Item Open Access Transanular interaction in [2.2]phanes: models for dimers?(1979) Goldacker, Wilfried; Hausser, Karl H.; Schweitzer, Dieter; Staab, Heinz A.The emission spectra of pseudo-ortho 3 and pseudo-geminal-4,7,12,15-tetramethoxy[2.2]-paracyclophane 3 were measured in glass matrices at 1.3 K. Furthermore, the zero field splitting parameters D and E and the decay rate constants ki of the excited triplet state were studied by optical detection of magnetic resonance in zero field. The results were compared with the corresponding monomer 1,4-dimethyl-2,5-dimethoxybenzene.