Closing Uranyl Polyoxometalate Capsules with Bismuth and Lead Polyoxocations

Abstract

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.

Benchmarking Uranyl Peroxide Capsule Chemistry in Organic Media

“…We tentatively attribute this to the encapsulation of heavy atoms. In a previous study, we had synthesized U 24 capsules that contain the heavy p‐block metal–oxo clusters [Bi 6 O 8 ] and [Pb 8 O 6 ] . The SAXS curves of these clusters likewise exhibit a very similar suppression of the first oscillation, which is also observed in the data simulated from their crystal structures.…”

Beyond Charge Balance: Counter‐Cations in Polyoxometalate Chemistry

“…This provides a conceptual strategy to further exploit Bi 3+ for stabilizing highly charged clusters. Interestingly, Nyman and colleagues used this strategy in reverse, stabilizing a Bi–oxo cluster via encapsulation and weak coordination inside a uranyl peroxide fullerene‐like capsule …”

Jenseits von Ladungsausgleich: Gegenkationen in der Polyoxometallat‐Chemie

“…So ergibt sich eine konzeptionelle Strategie, um diese Bindungseigenschaften von Bi 3+ zu nutzen, um weitere hochgeladene Cluster zu stabilisieren. Es sei bemerkt, dass Nyman und Mitarbeiter einen umgekehrten Prozess nutzten, um einen Bi‐Oxo‐Cluster durch Verkapselung und schwache Koordination innerhalb einer fullerenartigen Uranylperoxidkapsel zu stabilisieren …”

“…B. [Bi 6 O 8 ] 2+ oder [Pb 8 O 6 ] 4+ , als zentrale Template bei der Bildung von Uranylperoxidkapseln wie [(UO 2 )(O 2 )(OH)] 24 24− genutzt . Weiterhin wurde die supramolekulare Dreikomponenten‐Erkennung durch Kombination von Wells‐Dawson‐Wolframaten, kationischen Tantalbromidclustern (Ta 6 Br 12 (H 2 O) 6 ] 2+ ) und ungeladenem γ‐Cyclodextrin untersucht .…”