Abstracts

This work presents a detailed study of lanthanide ions (Eu³⁺, Gd³⁺) with nalidixic acid and flumequine ligands as binary complexes and as ternary complexes with phenanthroline (phen) and triphenylphosphine oxide (tppo) as co-ligands.When it comes to forming complexes with lanthanides, the choice of ligands plays a crucial role. Both flumequine and nalidixic acid because of their structures (Fig. 1) coordinate with metal ions in a bidentate fashion, utilizing the oxygen atoms from both their carbonyl (quinolone) and carboxylic groups. This not only allows to formation of stable complexes but also enhances the spectroscopic properties of lanthanide by displacing water molecules from the inner coordination sphere which might cause unwanted nonradiative quenching of luminescence. Both chosen ligands belong to a first generation quinolone antibiotics which makes them perfect ligands. Their anti-microbial properties have been thoroughly tested which expands the possibility of use their compounds in the biological and biolabeling areas and as ligands they are readily available at very reasonable cost. Introducing to the complexes co-ligands is aimed at increasing the luminescence properties of complexes. In order to characterize the structure of the compounds, carbon analysis, thermogravimetry and infrared spectroscopy (FTIR) were used. The strong red luminescence arises from the ⁵D₀ → ⁷F₂ transition which indicates efficient energy transfer from ligand to metal ion. Furthermore, decay times, the overall and intrinsic quantum yields were used to determine a contribution of the radiative and non-radiative paths to the excited state deactivation and to estimate the efficiency of ligand-to-metal energy transfer. Luminescent properties indicate a high application potential of the tested compounds, especially when introduced into polymeric materials such as films or beads.