Browsing by Author "Krieger, Claus"

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    1,8-dipyrenylnaphthalenes : syntheses, molecular structure, and spectroscopic properties
    (1984) Wahl, Peter; Krieger, Claus; Schweitzer, Dieter; Staab, Heinz A.
    Syntheses of the 1,8-dipyrenylnaphthalenes 1-3 are reported. The stereoisomers 1 and 2 were separated; their structural assignment is based on 1H NMR, on the optical activity of 2, and on X-ray structure analyses of 1 and 2. Kinetic parameters for the isomerisation 2 = 1 were determined by optical rotation measurements. - Emission spectra of 1 - 3 are discussed in comparison to monopyrenyl compounds 4 and 8. For 1 and 3 typical 'excimer-like' fluorescence is observed. The difference between 1 and 2 clearly demonstrates the dependence of excimer interactions between the pyrene units on the mutual orientation of the π-systems involved. - On the basis of X-ray analyses the molecular structures of 1- 3 are discussed with emphasis on π···π-interactions between the pyrene units.
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    [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, Dieter
    As 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.
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    Electronic properties of [3.3]TTF-phan TCNQ-crystals
    (1982) Schweitzer, Dieter; Taopen, Chu; Krieger, Claus; Staab, Heinz A.
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    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).
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    Molecular structure and spectroscopic properties of kekulene (Cycloarenes, a new class of aromatic compounds ; 2)
    (1983) Staab, Heinz A.; Diederich, Francois; Krieger, Claus; Schweitzer, Dieter
    The molecular structure of kekulene (1) was determined by X-ray structure analysis. From the bond lengths of 1 a remarkable localisation of aromatic sextets and double bonds is concluded (cf. formula 1b). - The problem of annulenoid versus benzenoid diatropicity in 1 is discussed on the basis of 1 H NMR absorptions. These data, in agreement with recent theoretical calculations support a predominant ring-current induction in the benzenoid subunits of 1 and rule out a significant contribution of annulenoid structures like 1a. - Absorption and emission spectra of 1 are discussed as are the zero-field splitting parameters of the excited triplet state of 1.
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    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.
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    Structures of 3,6-dimethoxy-1,2,4,5-tetrazine(V) and 3,6-Bis(1-aziridinyl)-1,2,4,5-tetrazine(VI)
    (1987) Krieger, Claus; Fischer, Hans; Neugebauer, Franz A.; Gückel, Friedemann; Schweitzer, Dieter
    (V): C4H6N4O2, Mr=142·12, orthorhombic, Pbca, a=6·865(3), b =13·192(5), c=7·013(3)A, V =635·1(7)A3, Z=4, Dx=1·486gcm-3, λ(MoKα)=0·71069A, μ=1·139cm-1, F(000)=296, T=295K, R=0·043 for 589 unique observed reflections [I ≥ 1·96σ(I)]. (VI): C6H8N6, Mr=164·18, monoclinic, C2/m, a=9·660(2), b=9·077(1), c=4·294(1)A, β=91·07(I)°, V=376·5(2)A3, Z=2, Dx=1·448gcm-3, λ(MoKα)=0·71069 A, μ=0·952 cm-1, F(000)=172, T=295K, R=0·037 for 405 unique observed reflections [I≥1·96σ(I)]. (V) and (VI) are centrosymmetric, with planar 1,2,4,5-tetrazine rings slightly compressed in the C···C direction (N-C-N≅126°). The remarkably short exocyclic C-O [1·328(2)A] and C-N[1·385(1)A] bond distances indicate that the methoxy and aziridinyl substituents act as π donors to the electron-deficient 1,2,4,5-tetrazine system.
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    ZFS-tensor of the triplet states of [2.2]phanes as studied by ESR
    (1981) Bär, Monika; Dinse, Klaus Peter; Goldacker, Wilfried; Hausser, Karl H.; Schweitzer, Dieter; Zimmermann, Herbert; Krieger, Claus
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