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
Year: 2026
Type: article
Abstract: In carbonate-rich aqueous environments relevant to spent nuclear fuel storage, radiolytic H2O2 and carbonate species promote the formation of uranyl peroxo-carbonate complexes under mild conditions. These complexes are poorly characterized spectroscopically, with many assignments remaining controversial. This work presents the first isotope validated solution-phase identification of the peroxo-dicarbonato species Mx[UO2(O2)(CO3)2](4–x)– (M = Na+ or K+) achieved through Raman and 18O-labeled H2O2 Fourier-transform infrared (FTIR) spectroscopy, combined with density functional theory (DFT) calculations. Key vibrational signatures distinguish the peroxo-dicarbonato complex from those of the tricarbonato complex [UO2(CO3)3]4–, including the νs(U–Oyl) stretch at 765–769 cm–1, the ν(U–Operoxo) mode at 400–452 cm–1, and the ν(O–O) stretch at 845–850 cm–1, which shifts upon 18O 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.
Source: Inorganic Chemistry
Language: English
Subfield: Inorganic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7162415297