Conventionally, π-conjugated polymers for organic electronic applications are prepared by polymerization methodologies based on palladium or nickel- catalyzed cross-coupling reactions such as Suzuki-Miyaura, Stille, Negishi and Kumada-Corriu couplings. These methods involve coupling between aryl halides or triflates and organometallic components such as -SnR3, -B(OR)2, -ZnR or –MgX. These conventional methods have some drawbacks; for example, they require synthetic steps to prepare the metallated monomers which can be difficult, or the compounds are unstable and difficult to purify. Furthermore, Stille coupling generates a stoichiometric amount of toxic byproducts that can be problematic to remove in large scale reactions. On the contrary, direct arylation polymerization has emerged as a potential alternative to traditional transition metal-catalyzed cross-coupling reactions. This method has several advantages over conventional cross-coupling reactions such as the absence of the organometallic precursors, eliminating the use of toxic Sn reagents and their byproducts, and fewer synthetic steps in the preparation of the monomers, which results in better atom economy and potentially lower cost overall. Of utmost importance, direct arylation polycondensation provides a useful and efficient way to integrate electron poor compounds into organic electronic materials. While electron donor heteroaromatic compounds are generally integrated into p-conjugated polymeric materials by Stille or Suzuki coupling with satisfactory results, electron acceptor monomers may give poor yields. Moreover, the synthesis of aryl halide, borononate, and tin derivatives of electron acceptor moieties can be challenging in many cases. Siloles are a family of low band gap compounds, with good charge carrying capabilities and optoelectronic properties. The C-H activation on 2,5-dithienylsiloles has been unsatisfactory due to silole ring opening attributed to the presence of nucleophile additives. However, by oxidizing the thiophenes at the 2 and 5 positions on the silole, we expect to be able to carry out selective C-H activation on the oxidized thiophene moiety without the silole ring opening side reaction, due to the mild reaction condition with no nucleophilic additive. In this talk, we will present our results on the use a modified electron poor silole monomer to generate conjugated co-polymers with other electron poor aryl compounds using a previously reported mild reaction condition.

Investigation of the direct arylation polycondensation of silole-thiophene-S,S-dioxide monomers

255th National Meeting (2018)

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