Organic Functionalization of Uranyl Peroxide Clusters to Impact Solubility.

Benzene-1,2-diphosphonic acid (Ppb) was introduced into the uranyl peroxide cluster system, resulting in three Ppb-functionalized uranyl peroxide clusters, (UO)(O)(CHPO) (UPpb), (UO)(O)(CHPO) (UPpb), and (UO)(O)(CHPO) (UPpb). Dissolution experiments were performed for the potassium salts of UPpb and UPpb, which revealed the capacity of UPpb to dissolve in the organic solvent dimethyl sulfoxide (DMSO). Unlike UPpb, the K salt of UPpb did not dissolve in DMSO but was more soluble in water, perhaps due to the lower proportion of Ppb ligands in its structure. In this work, UPpb and UPpb formed as potassium salts and both adopt the fullerene topology of previously reported U. U contains 20 uranyl peroxide units and encapsulates 12 Na cations. It is not possible for unfunctionalized U to incorporate 12 K cations owing to space constraints, as is the case in the new clusters reported here. Transformation of UPpb in water over time to produce U was observed, possibly owing to its ability to incorporate K cations, which have been associated with the formation of U.