Turbo Grignard-Mediated Distannylation of Ester-Functionalized Quinoid Heterocycles for Narrow-Bandgap Polymer Acceptors

Abstract

Conventional lithiation of ester-substituted quinoid fluorinated thieno[3,4-b]thiophenes (FTT) induces irreversible carbonyl degradation. We report a kinetically controlled i-PrMgCl·LiCl-mediated halogen–magnesium exchange that bypasses this limitation, enabling gram-scale synthesis of pure distannylated monomers. Stille polycondensation affords PY-FTT, a quinoid-enhanced polymer acceptor. All-polymer solar cells utilizing PY-FTT deliver an outstanding 12.4% power conversion efficiency. This mild stannylation protocol provides a robust paradigm for advanced narrow-bandgap conjugated materials.