Dokument

Summary:
The metalloid silicon is one of the most versatile elements of the world. Besides its widespread occurrence in the lithosphere, silicon containing compounds, for example the polymeric silicones, are used in numerous applications of the modern world. Moreover, the digital revolution and the progress in the photovoltaic industry is relying on silicon and its semiconductor properties. In contrast to its lower homologue, the carbon, silicon is capable of expanding its coordination geometry forming penta-, hexa- and even heptacoordinate complexes. Several of these structures have been examined over the last decades. However, most of these higher coordinate silicon complexes have been found to be hydrolytically unstable limiting their wider use, for instance in biological applications. The present thesis is addressing these limitations by investigating hexacoordinate (arenediolato)bis(polypyridyl)silicon(IV) complexes. The first part of the thesis deals with the synthesis and synthetic modification of higher coordinate silicon(IV) complexes. A successful post-coordination functionalization of silicon(IV) complexes is demonstrated. Besides halogenation, oxidation, and nitration reactions, a convenient nitrationreduction- condensation strategy tolerating various functional groups is discussed. Moreover, a synthetic approach to tris-heteroleptic complexes coordinating the DNA-intercalating ligand dppz is shown. In a prove of principal study, the results of the binding affinity of some silicon(IV) complexes to calf thymus DNA are presented. In a second project, the syntheses and biological properties of dinuclear metal-silicon(IV) complexes are studied. In order to constitute a small library of dinuclear complexes, different synthetic strategies including the previously presented nitration-reduction-condensation strategy, are discussed. With the library in hand, the biological activities of these complexes are investigated through binding studies to calf thymus DNA and G-quadruplex DNA. Moreover, the outcome of a cytotoxicity study using the MTT test for some dinuclear complexes is presented. In a third project, a Bodipy fluorophor is attached to the silicon(IV) complexes using various synthetic routes including the nitration-reduction-condensation strategy as well as a post-coordination clickchemistry approach. The photochemical and biological properties, namely the binding to calf thymus DNA and the light-switch behavior, of the obtained complexes are examined. Finally, the results of in-vitro confocal laser scanning microscope tests studying the ability of the complexes to enter the cell nucleus are shown.

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