Time-Resolved Self-Assembly of a Fullerene-Topology Core–Shell Cluster Containing 68 Uranyl Polyhedra

A complex core–shell cluster consisting of 68 uranyl peroxo polyhedra, 16 nitrate groups, and ∼44 K⁺ and Na⁺ cations was obtained by self-assembly in alkaline aqueous solution under ambient conditions. Crystals formed after a month and were characterized. The cluster, designated as {U₁⊂U₂₈⊂U_40R}, contains a fullerene-topology cage built from 28 uranyl polyhedra. A ring consisting of 40 uranyl polyhedra linked into five-membered rings and 16 nitrate groups surrounds this cage cluster. Topological pentagons in the cage and ring are aligned, and their corresponding rings of uranyl bipyramids are linked through K⁺ cations located between the two shells. A partially occupied U site is located at the center of the cluster. Time-resolved small-angle X-ray scattering and electrospray ionization mass spectrometry demonstrated that the U₂₈ cage cluster formed in solution within an hour, whereas the U_40R shell formed around the cage cluster after more than several days