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⊂U40R}, 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 U40R shell formed around the
cage cluster after more than several days.