Luminescence of Ln3+ lanthanide complexes in polymer matrices

Abstract

The photoluminescence properties of Tb3+ and Eu3+ complexes with polymer ligands containing various kinds of complexing groups—namely, carboxyl (5–20 mol %), pyridylquinoline (5 mol %), or pyridylnaphthyl (5 and 10 mol %) groups—in solution and block are considered. The chemical structure of a neutral comonomer (methyl methacrylate; styrene; isopropyl-, phenyl-, or benzylmethacrylamide; and N-vinylamides) in polymer ligands is varied. The intensity of photoluminescence is dependent not only on the chemical nature of a complexing group but also the chemical nature of a neutral comonomer and a spacer. Variation in the nature of a comonomer and a ligand makes it possible to prepare complexes in which a high luminescence of a low-molecular-mass complex is preserved and advantages inherent in a polymer complex are acquired. The effect of the nature of the polymer matrix (photoactive and photoinert) on the efficiency of electronic-excitation energy transfer is ascertained. The data on the photoluminescence of metal-polymer complexes that are based on polymer ligands containing vinylcarbozole units and that possess hole conductivity make it possible to regard them as materials for electroluminescence. The intensity of photoluminescence of these complexes is related to the competition of oppositely directed photophysical processes in a macromolecule: formation of excimers and migration of electronic excitation energy. An analysis of the published data and of the results of the authors shows that detailed studies of these polymer systems in solution and in matrices are needed to gain insight into the relationship between photo- and electroluminescence properties of metal-polymer complexes, because the matrix plays different roles in photoluminescence and electroluminescence (inner filter or conduction); as a consequence, the emission spectra may differ appreciably. It is shown that the efficiency of electroluminescence may be improved if the transfer of energy from the lanthanide ligand in a complex to the conducting matrix is decreased.