Synthesis and Vibrational Identification of the Uranyl Peroxodicarbonato [UO ₂ (O ₂ )(CO ₃ ) ₂ ] ⁴– : Insights into Peroxide-Carbonate Bonding from ¹⁸ O Labeling, DFT, and QTAIM Analysis

O substitution. FTIR data further confirm these assignments, providing the first infrared evidence of a uranyl peroxo-carbonato complex in aqueous solution. DFT calculations validate the observed frequencies and isotope shifts, clarifying the role of solvation and countercation effects. These results clarify uranyl peroxo-carbonato speciation, resolving long-standing ambiguities and establishing a robust spectroscopic framework for applications in uranium fuel dissolution, environmental mobility, and long-term waste stability.