Calorimetric Study of Functionalized Uranyl Peroxide Nanoclusters and Their Monomeric Building Block

The description of the energy landscape of polyoxometalates (POMs) enriches our understanding of their solution behavior through quantitative information that can be used to predict their existence, stability, and properties. Herein, we report thermodynamic values that describe the energy landscape of four uranyl peroxide nanoclusters (UPCs) (LiRb-U@U-24, LiNa-U(24)Pp(12), NaK-U(24)Pp(12), and U(60)Ox(30)) and a building block of UPCs, lithium uranyl triperoxide monomer (Li-UT). The results reveal relationships between the affinity of counter cations and the anionic uranyl peroxide units, enthalpy of dissolution, as well as enthalpy of crystallization and cluster solubility. Additionally, the calorimetric measurements of Li-UT allowed us to calculate a favorable enthalpy of formation of Li-U-24 and Li-U-28 from their monomeric units.