Ternary thiophene–X–thiophene semiconductor building blocks (X = fluorene, carbazole, phenothiazine): Modulating electronic properties and electropolymerization ability by tuning the X core

To achieve rationalization criteria for target-oriented molecular design of Th–X–Th (Th = thiophene) semiconductor building blocks, we have carried out an extensive investigation on the effects of the X core (X = fluorene, carbazole or phenothiazine) on the electronic properties and polymerization ability of Th–X–Th monomers and on the electronic and structural properties of the corresponding periodic conducting polymers –(Th–X–Th)n–, obtained by electropolymerization and, for comparison's sake, by FeCl3-catalyzed polymerization and/or Suzuki coupling. The effects of molecule bending and of solubilising bulky alkyl substituents have also been considered. The systematic, exhaustive template sequence combined with a rigorous, multitechnique investigation protocol affords a unique data library and a complete set of reliable interpretative/predictive guidelines.

► Effect of aromatic core on electronic properties in thiophene–X–thiophene trimers.
► The lower the electron richness of X core, the deeper the HOMO level.
► Different thiophene positions on X lead to kinked structure with lower conjugation.
► The fluorene structure exhibits the lowest Stokes shift and the highest quantum yield.
► The corresponding polymers obtained through three routes were studied.