Showing papers by "Burkhard König published in 1999"
TL;DR: In this article, a kinetically labile coordinative bond has been designed for self-assembly of an electron donor (phenothiazine) and a photo-inducible electron acceptor (riboflavin) in water at neutral pH.
Abstract: The known electron acceptor systems whereby the redox centers are linked by reversible noncovalent interactions are in most cases restricted to organic solvents. A kinetically labile coordinative bond has been designed for self-assembly of an electron donor (phenothiazine) and a photoinducible electron acceptor (riboflavin) in water at neutral pH. The pH dependent formation of the donor−acceptor complex in water was investigated by potentiometric titrations showing a binding constant of log K = 5.9. The strong binding constant supports the observed large fluorescence deactivation of the riboflavin emission by the phenothiazine zinc complex. The riboflavin fluorescence lifetime was found to be constant (τ = 4.7 ns) whatever the quencher concentration, clear evidence for a static quenching mechanism. A strong thermodynamical driving force and the observation of the riboflavin radical anion and phenothiazine radical cation by transient spectroscopy provide evidence for intramolecular electron transfer as the...
74 citations
9 citations
TL;DR: A derivative of 4-amino-N-methyl 1H-pyrrole-2-carboxylic acid was synthesized in this article, which is suitable for automated solid phase Fmoc protocols.
7 citations
Patent•
29 Jan 1999
TL;DR: In this article, a chromatographic separating media for the separation of nucleic acids, comprising a base carrier and an affinity ligand, which ligand contains a heteroaromatic rest of the formula (I), where X is -CH= or -N= and Y is -NCH3- or -O-.
Abstract: The invention relates to chromatographic separating media for the separation of nucleic acids, comprising a base carrier and an affinity ligand, which ligand contains a heteroaromatic rest of the formula (I), where X is -CH= or -N= and Y is -NCH3- or -O-. The invention also relates to a synthesis pathway for producing heteroaromatic oligoamides, in which the heteroaromatic amide units are introduced into a polymer support in the form of nitrated heteroaromatic carbonic acid derivatives without the need for protective groups.
6 citations
TL;DR: In this article, a convenient and regioselective synthesis of 6-O-sugar esters, which are useful additives as emulsifiers in food technology and cosmetics, without the use of protecting groups or catalysts is described.
5 citations
TL;DR: The [2.2]paracyclophane annelated cycloproparenes 2 and 3 were synthesized by dehydrohalogenation of the adducts prepared by reacting 1-bromo-2-chlorocyclopropene with 1-vinyl[2] paracyclogenes as discussed by the authors.
4 citations
TL;DR: In this article, the selectivity patterns of concave 1,10-phenanthroline membrane carriers have been determined, and measurements with copper (II) and lead(II) nitrates confirmed the predicted selectivities and revealed high transport rates for 1a and 1b.
Abstract: Concave 1,10-phenanthrolines 1 are selective and efficient carrier molecules for membrane transport of copper(II) and lead(II) ions. With competitive membrane transport experiments the selectivity patterns of three concave 1,10-phenanthroline membrane carriers have been determined. Measurements with copper(II) and lead(II) nitrates confirmed the predicted selectivities and revealed high transport rates for 1a and 1b. While 1b shows a high preference for copper(II) nitrate, 1a transports lead and copper nitrates equally well, but with much higher flux. In bulk liquid membranes, the carrier mediated ion flux remained constant over an extended period, whereas it decreased significantly in reused supported liquid membranes, which indicates rapid loss of carrier from the membrane under these conditions.
3 citations
TL;DR: Cyclophane chemistry and the research targets in this area have changed over the past two decades and more and more attention is now being paid to the function of the molecules, e.g., to the formation of inclusion complexes of large cyclophanes or the use of chiral cyclophane as auxiliars in asymmetric synthesis as discussed by the authors.
Abstract: Cyclophane chemistry and the research targets in this area have changed over the past two decades. While the unique electronic and structural properties of cyclophanes are still fascinating, more and more attention is now being paid to the function of the molecules, e.g., to the formation of inclusion complexes of large cyclophanes or the use of chiral cyclophanes as auxiliars in asymmetric synthesis. The rigid structures of short bridge cyclophanes has stimulated the synthesis of compounds with extended p-systems. Both their interesting physical properties, e. g., in intramolecular electron transfer processes, and their often beautiful structures of high symmetry are alluring. While synthetic approaches to cyclophanes, their reactivity and inclusion ability have been reviewed extensively, applications of the cyclophane scaffold and its properties are scattered. Therefore the author will focus on the recent developments in the chemistry of cyclophanes that have been used as building blocks for functional devices, as ligands for metal coordination and chiral auxiliaries or chiral ligands in synthesis. It will show that a class of compounds considered esoteric 20 years ago is now even reaching industrial applications. A review with 60 schemes and 122 references.