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+ subset-of 1]3 Cl- (= 3-La), [Tb3+ subset-of 1]3 Cl- (= 3-Tb), and [Eu3+ subset-of 2]3 Cl- (= 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.