Beiträge zur Chemie der Pyrrolpigmente, 84. Mitt.: Darstellung und Lumineszenz bichromophorer 5-Aryl-dipyrrinderivate

Summary 1,3- and 1,4-Bis-dipyrrin-benzenes and their various zinc and difluoroboryl chelates are prepared. Their absorption and fluorescence spectra are compared with those of the corresponding mono-dipyrrin derivatives. The conformations of these compounds are analyzed using the ring current model and absorption spectra. Dipole-dipole type transfer of excitation energy is discussed to represent a main photophysical channel in these compounds.

     

9,12-Dibenzothiazolylhypericin and 10,11-Dibenzothiazolyl-10,11-didemethylhypericin: Photochemical Properties of Hypericin Derivatives Depending on the Substitution Site

Investigating the properties of similar but regioselectively differently substituted hypericin derivatives, 9,12-dibenzothiazolylhypericin was synthesized and compared with the recently prepared 10,11-analogue. A significant difference in the ability to generate singlet oxygen and/or reactive oxygen species and different absorption spectra of these two derivatives were observed.     

Equilibrium charge state distributions of beam foil excited molecular fragments exiting carbon foils

Summary Equilibrium charge state distributions of ions emerging from solids have been measured. As incident particles were used both atomic (C⁺, N⁺, O⁺) and molecular (N ₂ ⁺ , CO⁺) projectile ions (0.025<E/M<0.108 MeV/u). The data of atomic projectile ions agree well with the data of other authors in a range in which they overlap. Charge state fractions of emerging molecular-fragment ions behind a carbon foil are strongly influenced by the Coulomb explosion and possibly by the wake potential. Supported by BMFT/Bonn.     

Well-posedness of the fundamental boundary value problems for constrained anisotropic elastic materials

We consider the equations of linear homogeneous anisotropic elasticity admitting the possibility that the material is internally constrained, and formulate a simple necessary and sufficient condition for the fundamental boundary value problems to be well-posed. For materials fulfilling the condition, we establish continuous dependence of the displacement and stress on the elastic moduli and ellipticity of the elasticity system. As an application we determine the orthotropic materials for which the fundamental problems are well-posed in terms of their Young's moduli, shear moduli, and Poisson ratios. Finally, we derive a reformulation of the elasticity system that is valid for both constrained and unconstrained materials and involves only one scalar unknown in addition to the displacements. For a two-dimensional constrained material a further reduction to a single scalar equation is outlined.This paper is dedicated to Professor Joachim Nitsche on the occasion of his sixtieth birthday     

Gas‐Phase Infrared Spectra of Three Compounds of Astrochemical Interest: Vinyl,Allenyl, and Propargyl Isocyanides

Isocyanides, isomers of the cyanides detected in the interstellar medium, are also possible components of this medium. The infrared spectra (5000–500 cm^?1) of gaseous vinyl isocyanide, allenyl isocyanide, and propargyl isocyanide have been recorded at 0.1 cm^?1 resolution. When prepared on a gram scale to produce a partial pressure of 10 mbar after evaporation in the cell, these three isocyanides, which have previously been reported to be kinetically unstable, do not display any sign of decomposition when recording the spectra. Geometry optimizations and harmonic and anharmonic vibrational frequencies were calculated using the LCCSD(T) method with the cc‐pVTZ basis set. Anharmonic frequencies of fundamental, overtone, and combination transitions were calculated using a variational approach implemented in the P Anhar.v2.0 code, to assign the experimental data for each compound. These results improve our knowledge of these under‐investigated compounds and pave the way for other physicochemical studies on functionalized isocyanides.     

Coupling of ortho-substituted aryl chlorides with bulky amides

Voluminous amides were coupled with deactivated, sterically hindered aryl chlorides in excellent yields providing products, which have not been efficiently accessible by transition metal catalysis so far. Application of an unsymmetric bisphosphine ligand was critical for the high catalytic activity.     

Ammonoxidised lignins as slow nitrogen-releasing soil amendments and CO₂-binding matrix

Nitrogen (N) is a major nutrient element controlling the cycling of organic matter in the biosphere. Its availability in soils is closely related to biological productivity. In order to reduce the negative environmental impact, associated with the application of mineral N-fertilizers, the use of ammonoxidised technical lignins is suggested. They can act as potential slow N-release fertilisers which concomitantly may increase C sequestration of soils by its potential to bind CO?. The idea of our study was to combine an improved chemical characterisation of ammonoxidised ligneous matter as well as their CO?-binding potential, with laboratory pot experiments, performed to enable an evaluation of their behaviour and stability during the biochemical reworking occurring in active soils.