Browsing by Author "Vogler, Helmut"
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Item 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.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 investigations of the lowest triplet state of s-tetrazines(1992) Gückel, Friedemann; Maki, August H.; Neugebauer, Franz A.; Schweitzer, Dieter; Vogler, HelmutWe report on the electronic and triplet state ODMR spectroscopy of s-tetrazine, 3,6-dimethyl-, 3,6-dimethoxy- and 3,6-bis(methylthio)-s-tetrazines. Zero field splitting parameters were obtained by ODMR monitoring both the delayed fluorescence and the phosphorescence in neat single crystals. The S1 and T1 exciton electronic origins are reported. The zero field splitting tensor is nearly axially symmetric with |D| approximately 0.4 cm-1. This value is found to be in good agreement with calculations based on magnetic dipole-dipole coupling in a 3B3u (nπ*) state. The calculations predict a positive value for D with the major axis passing through the C atoms at the 3 and 6 positions.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.