Thienoisoindigo-based small molecules and narrow bandgap polymers synthesized via C-H direct arylation coupling

Abstract

Thienoisoindigo (TIIG) has emerged as an attractive building block for high-performance organic optoelectronic devices. Here we report the first synthesis of a series of π-conjugated TIIG-based small molecules and alternating copolymers via direct C–H arylation, which enables the efficient synthesis without use of flammable and toxic orgametallic reagents in fewer steps compared Suzuki and Stille coupling. The direct arylation coupling between TIIG and two respective mono-bromo aryl reactants clearly shows that the α-H is more reactive than the β-H in the thiophene unit of TIIG. The high regioselectivity of TIIG monomer warrants the successful synthesis of high-quality alternating copolymers with minimal structural defects. PTIIG-BT polymer synthesized via direct arylation polymerization (DAP) showed comparable molecular weight and hole mobility than the same polymer previously synthesized via Suzuki coupling. Moreover, the two new polymers (PTIIG-TF and PTIIG-2FBT) synthesized via DAP showed hole mobility up to 10−3 cm2 V−1 s−1 in FET devices fabricated and tested under ambient conditions. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2015–2031