Thermodynamic Discrimination in the Formation of Tetranuclear Lanthanide Helicates

The complexation of lanthanide cations with a tripodal ligand bearing terminal ester functions was investigated. Thermodynamic speciation was achieved by a combination of different physicochemical methods, and the stability constants of the related complexes were determined spectrophotometrically. The formation of tetranuclear 3D edifices occurs preferentially with heavier lanthanides. Their molecular structure was confirmed by X-ray crystallography. Solid-state luminescence properties of the EuIII and TbIII compounds were also examined.