Synthesis and characterization of 2,3-difunctionalized thieno[3,4- b]pyrazine-based terthienyls: Structure-function relationships and side chain tunability.

摘要

The ability to tune the physical, electronic, and optical properties of polymer precursors has garnered a great deal of interest in the conjugated organic materials field. The Rasmussen group has previously demonstrated the ability to produce tunable, low band gap materials through the generation of new families of functionalized thieno[3,4-b]pyrazines (TPs). The scope of conventional TPs has been limited to either 2,3-dialkyl or diaryl analogues due to the standard synthetic approach of 3,4-diaminothiophene condensation with available stable alpha-diones. As a consequence, this limited the ability to effectively tune the electronic and optical properties of the TP unit. In an effort to expand the application and versatility of this new approach to tunable, low band gap materials, analogous families of TP-based terthienyls have been prepared as new polymer precursors. The synthetic route utilizes the well-known 3',4'-diamino-2,2':5',2"-terthiophene precursor for the production of 2,3-bis(trifluoromethanesulfonyl)-5,7-(2-thienyl)-thieno[3,4- b]pyrazine as a reactive intermediate. Simple substitution with a variety of nucleophiles thus allows the possibility to tune the properties of the oligomeric unit via the addition of electron-withdrawing or electron-donating groups at the 2- and 3-positions of the central TP unit. Incorporation of these new TPs into the terthienyl framework reduces the chemical reactivity of the central fused-ring unit and more easily allows for the application of these precursors to the desired polymeric materials.