Cationic Dithieno[3,2-b:2‘,3‘-d]phospholes:  A New Building Block for Luminescent, Conjugated Polyelectrolytes

Cationic dithieno[3,2-b:2‘,3‘-d]phospholes are accessible very efficiently by methylation of the phosphorus center. Further functionalization with bromo substituents in 2,6-positions affords a polymerizable monomer that can be copolymerized with a difunctionalized fluorene in a Suzuki−Miyaura-type cross-coupling protocol. The monomers as well as the resulting conjugated polyelectrolyte based on the phospholium units show very intriguing photoluminescence properties, even in the solid state.