Synthesis of asymmetric thieno[3,4-b]pyrazine-based terthienyls as precursors to low band gap materials

ORGN 463

Kelli Jo Syltie, kelli.syltie@ndsu.edu, LI Wen, Li.wen@ndsu.edu, and Seth C. Rasmussen, seth.rasmussen@ndsu.edu. Department of Chemistry and Molecular Biology, North Dakota State University, Fargo, ND 58105
A popular approach to the design of conjugated materials is through the use of mixed terthienyl-based precusors. In particular, the end-capping of a tailored fused-ring unit with external thiophenes gives mixed terthienyls that have been successful precursors to low band gap materials. However, current methods result in symmetrical terthienyls that provide either insoluble materials with low band gaps, or soluble materials with reduced conjugation. Through the production of three component thieno[3,4-b]pyrazine-based terthienyls with different external thiophenes, precursors can be designed that allow the advantage of alkyl side chains for increased solubility, without the steric interactions resulting from side chains on both external thiophenes. The use of only one external alkylthiophene in such thieno[3,4-b]pyrazine-based terthienyls will eliminate chain-chain interactions, and should provide soluble, low band gap materials. The synthesis of thieno[3,4-b]pyrazine-based terthienyl compounds and their electronic and optical characterizations will be presented.