Synthesis of New Monomers for Semiconducting Polymers and Their Application in Organic Optoelectronic Devices
Push-pull conjugated polymers, consisting of electron donating and withdrawing units gained increased attention because of their narrow band gap and their response to the light absorption and emission. Accordingly, four monomers with an intrinsic push-pull effect were synthesized via a dually selective cross-coupling reaction under Stille conditions between two types of heterocycles. The dinucleophile type beared both a trimethyl stannyl group and either a pinacol boronate (3-n-hexylthiophene) or a magnesium chloride group (N-derivate pyrrole). The dielectrophilic type consisted of iodo-bromo heterocycle derivates (phenyl, pyridine and thienyl). For these monomers, the presence of a remaining metal (pinacol boronate or magnesium chloride group) and bromine allowed further polymerizations under Suzuki-Miyaura or Kumada conditions. In the case of the thienyl-phenyl and thienyl-pyridine type monomer, oligomers were formed. Their electroluminescence was successfully demonstrated by the implementation into OLED devices. Additionally, stannoles, which are tin analogues of cyclopentadienes, were studied as possible electron deficient systems in combination with thiophene derivates in organometallic push-pull monomers. The synthesis of stannoles is generally performed using the conditions of the well-known Fagan Nugent reaction of alkynes, where in the first step zirconacyclopentadienes are formed and secondly transmetalated with dichloro stannanes. This thesis focusses on the formation of zirconacyclopentadienes by comparing the synthetic reactions between Negishi’s and Rosenthal’s reagent with several alkynes. The Rosenthal’s reagent proved to give higher reaction rates as well as higher yields of zirconacyclopentadienes in those cases, in which functional groups as aryl-halides, trimethylstannyl and trimethylsilyl were present. Lastly, first attempts of cross-coupling reactions between stannoles with nucleophilic substituents and thiophene electrophilic derivates were done.
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