Copolymers Containing Phosphorescent Iridium(III) Complexes Obtained by Free and Controlled Radical Polymerization Techniques

Abstract

A methacrylate‐functionalized phosphorescent Ir(III)‐complex has been synthesized, characterized, and applied as a monomer in radical copolymerizations. Together with methyl methacrylate, the complex has been copolymerized under free radical polymerization conditions. Aiming for host‐guest‐systems, applicable e.g. in organic light emitting devices (OLEDs), the complex was further copolymerized with a methacrylate‐functionalized carbazole derivative using the atom transfer radical polymerization technique. Applying gel permeation chromatography, in combination with a photodiode array detector, could clearly prove the formation of the copolymers. The optical properties of the photoactive monomers as well as the copolymers were investigated by absorption and emission spectroscopy (in solution). For the carbazole‐copolymer, the emission originates almost exclusively from the complex. This provides evidence of an efficient intrachain energy transfer, which makes the system an interesting candidate for potential OLED applications.magnified image

Recent Developments in the Application of Phosphorescent Iridium(III) Complex Systems

“…Recently, Ulbricht et al described the copolymerization of a bis-cyclometallated Ir III complex coordinating a methacrylate-equipped acetoacetate ligand with methyl methacrylate by free radical polymerization (using AIBN as initiator) and with a methacrylate-carbazole derivative applying atom transfer radical polymerization (ATRP) conditions (Scheme 4), respectively. [146] Unlike in PVK the carbazole-moieties of the ATRP-copolymer were introduced with a spacer to the polymeric backbone, which should even more suppress the formation of excimers [170] as in the case of 3-vinylcarbazole based polymers. [141] An almost exclusive emission from the complex in highly diluted solutions indicated an efficient intramolecular energy transfer from the carbazole units to the triplet emitter.…”

A π‐stacked and conjugated hybrid based on poly(N‐vinylcarbazole) postfunctionalized with terfluorene for stable deep‐blue hole‐transporting materials

“…We previously demonstrated rod–coil SCHs containing OPE/Cz to investigate the energy transfer and morphological stability 10. However, either unfavorable electroplex behaviors or irregularly π‐stacked channels due to flexible alkyl linkers occurs in above SCHs 11, 12…”

Novel Complex Polymers with Carbazole Functionality by Controlled Radical Polymerization

“…The wavelength of emitted light also differed in the range of blue-violet and blue-green fluorescence for carbazolyl and anthryl copolymers, respectively. A methacrylate-functionalized phosphorescent Ir(III)complex was copolymerized with a methacrylate-functionalized carbazole-derivative using ATRP (Scheme 8), with the aim of applying this type of host-guest-system to organic light-emitting devices [99]. In the system, the emission originated almost exclusively from the complex, suggesting efficient intrachain energy transfer.…”