Im Rahmen dieser Arbeit war es möglich, diverse dinukleare Platinphosphankomplexe darzustellen, wodurch unteranderem neuartige unsymmetrische (N- Aminoboryl)aminoboryl Pt-Komplexe, Borandiyl- und Diboran-1,2-diyl-verbrückte Diplatin-A-Frame Komplexe synthetisiert und charakterisiert werden konnten. Der abschließende Teil dieser Arbeit befasst sich mit den ersten Versuchen zur Darstellung von Polyboranen durch eine Palladium-vermittelte Kreuzkupplungsreaktion. / Within the scope of this work, it was possible to prepare diverse dinuclear platinum phosphane complexes, allowing, among others, the synthesis and characterization of novel asymmetric (N-aminoboryl)aminoboryl Pt- complexes, boranediyl- and diborane-1,2-diyl-bridged diplatinum A-frame complexes. The final part of this thesis focuses on the first attempts to synthesize polyboranes through a palladium-mediated cross-coupling reaction.

Der erste Teil der Arbeit untersucht den Einsatzes von 4,6-Di-(pyrid-2´-yl)-1,3,5-triazin als Baustein für Metallo-supramolekulare Polyelektrolyte. Die dafür nötigen ditopen Liganden werden mittels Stille Kreuzkupplungen dargestellt. Die Absorptions- und Fluoreszenzeigenschaften können durch den Einbau von Oligothiophenen eingestellt werden. Im zweiten Teil der Arbeit werden die elektrorheologischen Eigenschaften von Metallo-supramolekularen Polyelektrolyten untersucht. Zu diesem Zweck werden die Koordinationspolymere in das Schichtsilikat Montmorillonit interkaliert. Die Interkalation wird mittels verschiedener analytischer Methoden wie Pulverdiffraktometrie, Thermoanalyse oder Infrarotspektroskopie untersucht. Die entstehenden Nanokomposite zeigen einen elektrorheologischen Effekt bei einer geringen Stromdichte. / The first part of the thesis shows the use of 4,6-di-(pyrid-2´-yl)-1,3,5-triazine as building block for metallosupramolecular polyelectrolytes. The necessary ditopic ligands are available by a Stille cross coupling. The absorption and fluorescence properties can be tuned by the incorporation of oligothiophenes. The electrorheological properties of metallosupramolecular polyelectrolytes are examined in the second part. On this account the coordination polymers are intercalated into the layered silicate montmorillonite. The intercalation is analyzed by methods as powder diffraction, thermoanalytical techniques and infrared spectroscopy. The nanocomposites show an electrorheological effect and low current densities.

Mechanochromic polymers respond to external force by changing their color. This can be achieved by the incorporation of a molecular switch such as spiropyran (SP) into polymers. SPs can be isomerized by mechanical force from their colorless form into colored merocyanines. Main chain copolymerization of spiropyrans allows investigation of their mechanochromic behavior and potential use as force sensors. So far, several covalent polymer matrices have been used to investigate the mechanochromic response of SPs, among them poly(ε caprolactone) (PCL). Less investigated is how the mechanochromic response can be fine-tuned by substituent effects. First, PCL with differently substituted spiropyrans at the chain’s midpoint were used in order to investigate the effect of different substituents and their regiochemistry on the isomerization behavior of SPs under mechanical stress. A low activation barrier was observed for NO2 substitution of “ortho”-spiropyrans compared to no substitution (R = H). In order to investigate phenyl-substituted “para,para” spiropyrans, a newly developed kinked polyarylene was employed as covalent matrix material. This new polyarylene (PmmpP) has a meta,meta,para connection in its backbone and exhibits excellent mechanical properties. Its high strength allows the isomerization of this molecular switch with a large activation barrier. The phenyl-substituted “para,para” spiropyran showed transient mechanochromism and was switched 25 times in force-and-release cycles. The synthesis of PmmpP was carried out by a Suzuki polycondensation in three steps from commercial starting materials. To further capitalize on the simplicity and properties of PmmpP, a two step synthesis of a semifluorinated kinked polyarylene was demonstrated by direct arylation polycondensation with tetrafluorobenzene (F4). This partially fluorinated PmmpF4 was synthesized with a variety of side-chains. Resulting polymers exhibited a large range of glass transition temperatures, allowing for the production of tailor-made smart materials.

Mechanochromic polymers are force-sensitive materials that change their color as a response to mechanical stimuli. This visualization of forces can be used to further optimize polymer-based materials by understanding microscopic force transduction or to display fatigue of material. Most mechanochromic systems rely on bond cleavage, so they can only distinguish between “on” and “off” state without any further correlation of the applied force with the optical signal. Although reversibility to the initial state is possible for most of these systems, it often demands time or input of energy making them rather unsuitable for sensing forces in real-time. In this work, the development and application of mechanochromic donor (D)-acceptor (A) torsional springs is presented as a new concept for mechanochromic materials. The mechanically induced planarization of D and A leads to a continuous red-shift of both absorption and emission color. A suitable DA-system is found in ortho-substituted diphenyldiketopyrrolopyrrole (o-DPP) having the large torsional angle required for the equilibrium geometry and therefore showing blue-shifted optical spectra compared to reference compounds with a smaller torsional angle. The covalent incorporation into tough poly(meta,meta,para-phenylene) (PmmpP) by Suzuki polycondensation enables sufficient force transduction to the DA spring during uniaxial elongation of thin-film specimens. The detected mechanochromic response correlates with the applied stress and shows full reversibility upon stress release. Theoretical experiments based on density functional theory (DFT) confirm the experimental results and offer a detailed explanation of the molecular deformations responsible for the optical shift. In addition, the application as stress sensor was tested investigating the molecular force transduction in glassy PmmpP as a function of the number average molecular weight (Mn) by blending o-DPP-PmmpP probe chains of varying Mn with pristine PmmpP. The distinct mechanochromic response for entangled and non-entangled probe chains, respectively, allows the extraction of the critical molar mass (Mc) that is required for entanglements to become effective. The resulting value for the entanglement molar mass Me ≈ 1/2 Mc is in excellent agreement with the value determined by rheology.