Closing Uranyl Polyoxometalate Capsules with Bismuth and Lead Polyoxocations.

Uranyl polyoxometalate clusters are both fundamentally fascinating and potentially relevant to nuclear energy applications. With only ten years of development, there is still much to be discovered about heterometal derivatives and aqueous speciation and behavior. Herein, we show that it is possible to encapsulate the polyoxocations [Bi O ] and [Pb O ] in [(UO )(O )(OH)] (denoted Bi@U and Pb@U ) in pure form and high yields despite the fact that under aqueous conditions, these compounds are stable on opposite ends of the pH scale. Moreover, [Pb O ] is a formerly unknown Pb polynuclear species, both in solution and in the solid state. Raman spectroscopic and mass spectrometric analysis of the reaction solutions revealed the very rapid assembly of the nested clusters, driven by bismuth- or lead-promoted decomposition of excess peroxide, which inhibits U formation. Experimental and simulated small-angle X-ray scattering data of Bi@U and Pb@U solutions revealed that this technique is very sensitive not only to the size and shape of the clusters, but also to the encapsulated species.