Dynamics of a Nanometer-Sized Uranyl Cluster in Solution

摘要

The discovery of a family of large uranyl peroxo clusters has dramatically affected the ideas about the environmental chemistry of actinide elements. To date more than 40 structures have been isolated and have proven to make up a heterogeneous class in terms of size, structural motifs, solution stability, and speciation. In spite of their likely importance as environmentally relevant species, little is known about the solution dynamics of these clusters, such as dissociation mechanisms and electrochemical stabilities. An added challenge has been the isolation of large quantities of pure compound with NMR-active nuclei in the structure. Here we probe the solution chemistry of a uranyl peroxo cluster that contains 24 uranyl moieties linked by 12 pyrophosphate units. This oblong uranyl pyrophosphate cluster has a nominal stoichiometry of [(UO2)_(24)(O2)_(24)-(HP2O7)6(H,P2O7)6]~(30-)(Figure 1, U_(24)P), is soluble in aqueous solution over a wide pH range and is easily detected by ~(31)P NMR spectroscopy.