Browsing by Author "Diederich, Francois"

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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, 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.
Open Access
Electronic properties of kekulene
(1982) Schweitzer, Dieter; Hausser, Karl H.; Vogler, Helmut; Diederich, Francois; Staab, Heinz A.
The fluorescence and phosphorescence of kekulene in a host matrix of polycrystalline tetrachlorobenzene are investigated, together with the triplet zero field splitting parameters |D| and |E| obtained by ODMR in zero field. The D value is also calculated within a semi-empirical π-theory and compared with experiment. It could be shown that the triplet state energies of a number of different sites of kekulene in the host matrix and the zero field splitting parameters are related, in first order, by spin orbit interaction.
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).
Open Access
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.
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.
Open Access
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.