Crystal Structures of the Lanthanum(III), Europium(III), and Terbium(III) Cryptates of Tris(bipyridine) Macrobicyclic Ligands

The crystal structures of the La^III, Eu^III, and Tb^III complexes of macrobicyclic [bpy.bpy.bpy] ligands, [La³⁺ ? 1 ]3 Cl^? ( = 3- La), [Tb³⁺ ? 1 ]3 Cl^? ( = 3- Tb), and [Eu³⁺ ? 2 ]3 C1^? ( = 3- Eu), have been determined. They confirm the cryptate nature of these species, the cations being bound to the eight N-sites of the ligand. The macrobicycle presents two open faces, thus allowing additional coordination of two species, Cl^? ions or H₂O molecules, to the bound cations. These data provide structural support for the photophysical studies of the luminescent properties of the Eu^III and Tb^III cryptates, which indicated residual coordination of H₂O molecules.