Synthesis and electronic properties of conjugated polymers based on rhenium or ruthenium dipyridophenazine complexes

Abstract

Two series of luminescent conjugated polymers based on rhenium (I) or ruthenium (II) dipyridophenazine complexes have been synthesized by the palladium catalyzed coupling reaction using divinylbenzene and aromatic dibromides as the monomers. From the photoluminescence spectra, an energy transfer process between the conjugated backbone and the metal complexes is proposed. The ruthenium containing polymers were fabricated into light emitting devices because of their better film forming qualities. The electroluminescence (EL) of the polymers originated from the emission due to the π*-π or π*-d transitions. Depending on the metal complex content, the polymers exhibit different absorption and EL spectra. The devices exhibit a turn-on voltage of 10 V and external quantum efficiency of 0.6%. From the cyclic voltammetry results, an additional oxidation couple was observed after the incorporation of the ruthenium complex which may contribute to the charge transport process. This was further supported by the charge mobilities measurement in which the electron and hole mobilities of the polymers are enhanced by the metal complex and are of the order of 10-4 cm2 V-1 s- 1.