Highly emissive iptycene-fluorene conjugated copolymers: Synthesis and photophysical properties

Iptycene-type quinoxaline and thienopyrazine monomers were successfully synthesized via a condensation between 10-dihydro-9,10-ethanoanthracene-11,12- dione and the corresponding diamines. Copolymers based on fluorene and three iptycene monomers were prepared via Suzuki coupling reaction, and they exhibited good solubility in appropriate organic solvents. These copolymers are fluorescent in both solution and the solid state, emitting blue, greenish-blue, and red color due to the different electronic properties of the iptycene comonomers. The difference in their absorption and emission spectra was attributed to the donor-acceptor charge transfer interactions and/or polymer backbone conformational changes induced by steric effects. Moreover, the spectroscopic data clearly demonstrated the insulating effect of iptycene units, which prevented the aggregation of the polymer chains and the formation of excimers in the solid state.