Highly luminescent 1,4-diketo-3,6-diphenylpyrrolo[3,4-c]pyrrole(DPP-) based conjugated polymers prepared upon Suzuki coupling

Five new Soluble conjugated polymers are described, which were prepared upon Suzuki polycondensation reactions. They alternately consist of dialkylated 1,4-diketo-3,6-diphenyl-pyrrolo[3,4-c]pyrrole (DPP) units and carbazole, triphenylamine, benzo[2,1,3]thiadiazole, anthracene, and fluorene units. The polymers were prepared from 1,4-diketo-2,5-dihexyl-3,6-bis(4-bromophenyl)pyrrolo[3,4-c]pyrrole (1a), 1,4-diketo-2,5-di(2-ethylhexyl)-3,6-bis(4-bromophenyl)pyrrolo[3,4-c]pyrrole (1b), or 1,4-diketo-2,5-dihexyl-3,6-bis(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)pyrrolo[3,4-c]pyrrole (1c), and 3,6-bis(4,4,5,5-tetramethyl-1,3,2dioxaborolan-2-yl)-9-ethylhexylcarbazole (2), 4,4'-dibromotriphenylamine (3), 4,4'-bis(4,4,5,5-tetramethyl-1,3,2dioxaborolan-2-yl)triphenylamine (4), 2,7-bis(4,4,5,5-tetramethyl- 1,3,2-dioxaborolan-2-yl)-9,9-dihexylfluorene (5), 9,10-anthracenebispinaeolatoboron ester (6), and 4,7-dibromo-2,1,3-benzothiadiazole (7). The polymers exhibit brilliant red colors. They are soluble in common organic solvents and form orange to red solutions with absorption maxima between 479 and 515 nm. Polymer solutions are highly fluorescent with photoemission maxima between 552 and 600 nm. Photoluminescence quantum yields up to 86% could be determined. The polymers exhibit molecular weights up to 20 000 Da. Cyclic voltammetric studies indicate quasi-reversible oxidative cycles, while reductive cycles are irreversible. Exemplary studies on the electroluminescence of the DPP-fluorene copolymer indicate a maximum emission at 600 nm, the turn-on voltage being 3.5 V. Maximum efficiencies up to 0.5% and a brightness of 50 cd m(-2) could be reached.