Coordination of Ln3+ Ions to Perhydroxycucurbit[5]uril and the Formation of Supramolecular Self-Assemblies in the Presence of [SiW12O40]4- Anions and Transition Metal Salts - Potential Application in the Isolation of Light Lanthanides

The coordination and supramolecular assemblies of lanthanide cations and perhydroxycucurbit[5]uril {(HO)(10)Q[5]} in the presence of [SiW12O40](4-) anions and transition metal salts show significant differences as the lanthanide atomic number increases. The molecular capsule (HO)(10)Q[5] coordinates with the light lanthanide cations Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, and Tb3+ but does not coordinate with heavier Ln(3+) cations. However, (HO)(10)Q[5]/Na+-based molecular capsules form in the presence of the heavier lanthanide cations Ho3+, Er3+, Tm3+, Yb3+, and Lu3+ under the same synthetic conditions. These differences could be key in establishing a strategy for the isolation of light lanthanides from their heavier counterparts.