Abstract
In order to introduce binding sites into rigid membrane gaps, reactions were investigated to functionalise double- or triplebonds in aqueous media. Various oxidants (osmiumtetroxid, mercurydiacetate, tetrachloroauric(III)acid und rutheniumdioxide) led to secondary alcohols or ketones in 50-60 % yield. Tetrachloroauric(III)acid was found to be the best reagent under these reaction conditions. It was the only one which worked without addition of organic solvents, so it could be used for the purpose of oxidation within a rigid membrane which is localised in monolayers on solid substrates. Bolaamphiphiles with two central amide functions in addition to a terminal thiol function were synthesized in order to construct the membrane gaps.
Other synthetic target molecules containing carbon-carbon double bonds were bipyridyl-amphiphiles containing alkene chains (oleyicacid chains, or derivates of dodecylmethacrylate). They should produce layered micelles with a fluid center and a redox-active head group. The center should dissolve photoactive porphyrins, the head groups work as electron acceptors or donors.
The synthetised complexes showed however, that the increase of fluidity inside caused a destruction of the multilayered structure. Organised systems could not be obtained, although the new formed micelles dissolved a magnesia tetradecyloxyphenyl-porphyrin perfectly well.
In the course of the investigation of fluid and solid micellar membrane structures dissolving the magnesia-porphyrin we observed strong effects of added solvents, in particular methylene dichloride. We observed a split soret band (exciton effect) indicating the formation of linear (no stacks) porphyrin assemblies. These aggregates were also found in presence of SDS micelles, which generally only provides space for porphyrin monomers.
Ruthenium(II) the central metal ion of the complex head group of the bipyridyl-amphiphiles which formed rigid multilayered micelles upon sonification was then exchanged against iron(II). Although the iron complexes are kinetically much less stable compared to the ruthenium ones it was impossible to introduce the three different ligands one after the other analogous to the typical procedures for the synthesis of ruthenium complexes. Under this circumstances only symmetrical iron complexes trisubstituted with the ligand of highest binding constant towards iron(II) were obtained. Synthesis started therefore with bipyridinyl-5-carboxylate only. After reaction with one equivalent of an ethylendiamine derivate with two long alkylic chains we succeeded to obtain the desired unsymmetrically build trisbipyridyl-iron(II)-complex. |
