Decreasing aromaticity in π-conjugated materials: Efficient synthesis and electronic structure identification of cyclopentadiene-containing systems

An efficient route to cyclopentadiene-containing π-conjugated molecules is reported. A comparative analysis between the aryl/dienyl hybrids and their aromatic congeners shows a propensity of the diene moiety to reduce the optical band gap of a π-conjugated system without compromising a planar structural topology. Moreover, a novel poly(fluorene) derivative bearing alternating cyclopentadiene repeat units was synthesized to demonstrate the applicability of this method in polymer synthesis.