COMPARATIVE CHARACTERISTICS OF SPECTRAL-LUMINESCENCE PROPERTIES OF Yb(III) COMPLEXES WITH UNSATURATED β-DIKETONES

The study presents a comparative analysis of the spectral-luminescent properties of synthesized β-diketonate coordination complexes of ytterbium with the following ligands: 2,7-dimethyl-oct-1-en-3,5-dione, 2,6-dimethyl-hept-1-en-3,5-dione, 2-methyl-5-phenylpent-1-en-3,5-dione, 2-methyl-5-­biphenylpent-1-en-3,5-dione. In addition, research was conducted on polymeric compounds based on these complexes and their phenanthroline mixed-ligand derivatives. Using a range of physicochemical analysis methods, it was established that the structure of the ele­mentary unit during polymerization, as well as the coordination sphere of the complexes during the formation of mixed-ligand compounds, does not undergo significant changes compared to the initial β-diketonate molecules. Thermal analysis revealed a significant increase in the decomposition onset temperature of mixed-ligand and metallopolymeric compounds compared to their monomeric counterparts. Luminescence spectroscopy demonstrated that the studied samples exhibit luminescence in the infrared (IR) range. A comparative analysis of the integral luminescence intensities of ytterbium complexes identified key factors influencing the emission characteristics. Primarily, the synthesis of mixed-ligand complexes with phenanthroline mitigates the negative effects of one of the most well-known quenching factors: OH-oscillators of water molecules, which complement the coordination sphere of monomeric ytterbium complexes. Furthermore, the synthesis of polymeric compounds based on β-diketonate complexes positively affects the luminescence, potentially due to a reduction in concentration quenching, as in polymers, the emitting centers are uniformly distributed along the macromolecular chain. Besides directly enhancing luminescent properties, this approach aims to address the practical application of the synthesized compounds since polymers are significantly easier to process and can form film materials. Based on the conducted research, the following luminescence intensity dependencies were established: dmod>dmhpd>mbphpd>mphpd, as well as monomer-polymer-MLC-MLC polymer. As seen from the presented data, the best emission characteristics are exhibited by ytterbium mixed-ligand mono- and polycomplexes with β-diketones containing alkyl substituents.