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.