@phdthesis{Riensch2021,
  author    = {Riensch, Nicolas Alexander},
  title     = {Silicon/Boron Exchange Routes to Novel Inorganic-Organic Hybrid Molecules, Oligomers, Polymers and Macrocycles},
  doi       = {10.25972/OPUS-23865},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-238657},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {Industrially used semiconducting materials, building blocks of modern electronics and computer industry, are mostly based on inorganic, crystalline solids, which have the drawback of relatively high production costs. As an alternative, organic pi-conjugated systems show enhanced flexibility and processability as well as the opportunity to obtain light-weight materials. They have emerged as attractive candidates, especially since elements beyond hydrogen and carbon can be used to create pi-conjugated frameworks. In recent years, pi-conjugated oligomers and polymers with tricoordinate boron centers incorporated into the main chain of such organic polymers have attracted considerable attention as the interaction of the vacant p orbital on boron with an adjacent pi system of the chain leads to extended conjugated materials. These materials show intriguing optical and electronic properties and potential applications in organic electronics and optoelectronics (OLEDs, OFETs, photovoltaics) or as sensory materials. In this thesis, a catalytic Si/B exchange reaction protocol is used as a facile and highly effective B-C bond formation method to synthesize organoboron molecules, oligomers, polymers and macrocycles. This reaction is applied to synthesize a series of thienyl- and furylborane based materials. Special focus is on furylborane based materials, which, in general, have been only scarcely explored so far. This is mainly due to synthetic challenges since furan decomposes readily in the presence of light and oxygen. Our mild and highly selective reaction protocol in combination with sufficient kinetic protection of the boron centers gives access to a series of extended organoboranes featuring furylborane units in the main chain. Furthermore, kinetically stabilized furylboranes are established as highly robust and versatile building blocks for pi conjugated materials. The obtained materials reveal remarkable luminescence properties. The scope of potential starting materials was investigated by a catalyst screening, demonstrating that the Si/B exchange reaction can also be performed for less reactive aryldichloroboranes. Furthermore, borazine-based hybrid cyclomatrix microspheres have been synthesized via a Si/B exchange condensation reaction under precipitation polymerization conditions. Finally, synthetic routes to tetrabora- and diboraporphyrinogens were attempted in a multi-step reaction procedure. In the case for tetraboraporphyrinogens, the final macrocyclization reaction under pseudo high-dilution conditions afforded a mixture of macrocycles with different ring sizes. UV-vis and fluorescence spectroscopic analysis indicated significant differences in comparison to their linear congeners.},
  subject      = {Bororganische Verbindungen},
  language  = {en}
}
@phdthesis{Lorenz2021,
  author    = {Lorenz, Thomas},
  title     = {Conjugated Polymers with BN Units in the Main Chain},
  doi       = {10.25972/OPUS-21923},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-219230},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {In recent years <mi>PI</mi>-conjugated organoboron polymers and BN-doped polycyclic aromatic hydrocarbons have attracted a lot of interest due to their great potential in organic electronics. However, there are only few known examples of conjugated polymers with BN units in their main chain. Within this work silazane cleavage with silicon-boron (Si/B) exchange for the synthesis of a novel class of inorganic-organic hybrid polymers is demonstrated. These polymers consist of alternating NBN and para-phenylene units in the main chain. Photophysical studies and TD-DFT calculations for the polymer and molecular model systems were carried out, revealing a low extent of <mi>PI</mi>-conjugation across the NBN units. The new polymers can be used as macromolecular polyligands by a cross-linking reaction with a ZrIV compound. In the next chapter the synthesis and characterization of the first poly(p-phenylene iminoborane) is presented. This novel inorganic-organic hybrid polymer can be described as a BN analogue of the well-known poly(p-phenylene vinylene) (PPV) and is also accessible using the previously described Si/B exchange as synthetic strategy. Photophysical investigations and TD-DFT calculations on the polymer and corresponding model oligomers provide clear evidence for <mi>PI</mi>-conjugation across the B=N units and extension of the conjugation path with increasing chain length. Furthermore, a possible application of Si/B exchange for the synthesis of polysulfoximines was explored. Herein, diaryl sulfoximines and a p-phenylene bisborane serve as building blocks for new BN- and BO-doped alternating inorganic-organic hybrid copolymers. While the BN-linked polymers were accessible by a facile silicon/boron exchange protocol, the synthesis of polymers with B-O linkages in the main chain is achieved by salt elimination. In the last chapter the concept of Si/B exchange was investigated for the synthesis of BP-linked oligomers. Herein oligomers with sterically less demanding substituents (substituents: 2,4,6-trimethylphenyl or 2,4,6-tri-iso-propylphenyl) at the phosphorus are accessible using Si/B exchange, but the oligomer with Mes* (2,4,6-tri-tert-butylphenyl) as substituent needed a salt elimination pathway to give the desired product. Experimental data and theoretical investigations indicate, that the P-substituent has a high influence on the geometry of the phosphorus center and therefore on the possible conjugation over the BP units.},
  subject      = {Polyphenylenvinylenanaloga},
  language  = {en}
}