Fluorinated Thiophene-Based Synthons: Polymerization of 1,4-Dialkoxybenzene and Fluorinated Dithieno-2,1,3-benzothiadiazole by Direct Heteroarylation

The incorporation of fluorine atoms along the conjugated polymer backbone is an effective strategy to tune the electro-optical properties of donor–acceptor based copolymers. We report here an efficient way to synthesize and purify new mono-fluorinated thiophene derivatives for the synthesis of fluorinated dithienobenzothiadiazole (DTBT) comonomers. It was observed that the reactivity and regioselectivity of the direct (hetero)arylation polymerization (DHAP) were modified upon the amount and the positioning of the fluorine atoms on the DTBT moiety. Indeed, the polymerization time went from 66 h (for non-fluorinated DTBT, M1) to only 11 min (for tetra-fluorinated DTBT, M2). In addition to enhanced reactivity, the degree of fluorination of the flanking thiophene of the DTBT moiety also modulates the electro-optical properties, lowering both the bandgap and stabilizing the ionization energy level. Indeed, P1 (with non-fluorinated flanking thiophene) has a bandgap of 1.73 eV and an ionization energy (IE) of 4....