New π-conjugated polymers are described, which entirely consist of aryl-aryl-coupled 1,4-diketo-2,5-dialkyl-3,6-diphenylpyrrolo[3,4-c]pyrrole (DPP) units. The alkyl groups are n-hexyl (4a) or 2-ethylhexyl (4b) groups. The polymers are synthesized using nickel-promoted and palladium-catalyzed one-pot coupling reactions starting from 1,4-diketo-2,5-dialkyl-3,6-di(4-bromophenyl)pyrrolo[3,4-c]pyrrole (dibromo-DPP) as monomer, or conventional palladium-catalyzed coupling of dibromo-DPP and the 3,6-bis(pinacolato)boronester derivative of DPP. Polymers exhibit molecular weights up to 33 000 and are excellently soluble in chloroform and toluene. Deep red solutions (λ max of 4b: 525 nm) with intense red photoemission (λ max of 4b: 632 nm) and unusually large Stokes shift up to 107 nm are obtained. Cyclic voltammetry indicates quasi-reversible oxidation and reduction behavior, the onset potentials of 4b are +1.03 and -0.74 V vs SCE, respectively. From these potentials, HOMO/ LUMO levels of -5.47 and -3.70 eV, respectively, can be calculated. Good solubility and processability into thin films render the compounds suitable for electronic applications.

Summary: Six new soluble conjugated polymers are described, which were prepared by Stille and Heck polycondensation reactions. They alternately consist of dialkylated 1,4‐diketo‐3,6‐diphenyl‐pyrrolo[3,4‐c]pyrrole (DPP) units and divinylbenzene or thiophene‐based units. The polymers were prepared from 1,4‐diketo‐2,5‐dialkyl‐3,6‐di(4‐bromophenyl)‐pyrrolo[3,4‐c]pyrrole with alkyl being hexyl (1a), methyl (1b), and 2‐ethylhexyl (1c) and 2,5‐bis(tributylstannyl)thiophene (2), 5,5′‐bis(tributylstannyl)bithiophene (3), 3,4‐ethylenedioxythiophene (4) and divinylbenzene (5). The new polymers exhibit brilliant red purple color and strong photoluminescence in common organic solvents. The DPP‐phenylenevinylene copolymers exhibit molecular weights up to 41 000 Da, and the poly(DPP‐thienylene)s up to 12 200 Da. In chloroform, the poly(DPP‐thienylene)s exhibit absorption and photoluminescence maxima up to 560 and 624 nm, respectively, the corresponding maxima of the poly(DPP‐phenylenevinylene)s are at 529 and 640 nm, respectively. Quantum yields of fluorescence up to 36% were determined. Cyclic voltammetric studies indicate quasi‐reversible oxidation (p‐doping) of the poly(DPP‐thienylene)s and irreversible reduction (n‐doping) of all polymers.Molecular structure of polymers.magnified imageMolecular structure of polymers.