ipso‐Arylative Ring‐Opening Polymerization as a Route to Electron‐Deficient Conjugated Polymers.

ipso‐Arylative ring‐opening polymerization of 2‐bromo‐8‐aryl‐8H‐indeno[2,1‐b]thiophen‐8‐ol monomers proceeds to Mn up to 9 kg mol−1 with conversion of the monomer diarylcarbinol groups to pendent conjugated aroylphenyl side chains (2‐benzoylphenyl or 2‐(4‐hexylbenzoyl)phenyl), which influence the optical and electronic properties of the resulting polythiophenes. Poly(3‐(2‐(4‐hexylbenzoyl)phenyl)thiophene) was found to have lower frontier orbital energy levels (HOMO/LUMO=−5.9/−4.0 eV) than poly(3‐hexylthiophene) owing to the electron‐withdrawing ability of the aryl ketone side chains. The electron mobility (ca. 2×10−3 cm2 V−1 s−1) for poly(3‐(2‐(4‐hexylbenzoyl)phenyl)thiophene) was found to be significantly higher than the hole mobility (ca. 8×10−6 cm2 V−1 s−1), which suggests such polymers are candidates for n‐type organic semiconductors. Density functional theory calculations suggest that backbone distortion resulting from side‐chain steric interactions could be a key factor influencing charge mobilities. [ABSTRACT FROM AUTHOR]