The actinyl cation (An(V/VI)O2+/2+ ) can participate in a variety of interactions through the strongly coordinated oxygen atoms, which can influence the overall chemical reactivity of the system. The interactions that occur with low-valent cations (actinyl-cation interactions) may influence the spectroscopic signals and chemical properties of the An(V/VI)O2+/2+ in solution phase and resulting solid materials. In this study, we focused on the impacts of varying concentrations of lithium ions on the spectroscopic signals of uranyl (VI) cation, neptunyl (V) cation, and neptunyl (VI) cation in solution. Raman spectroscopy was utilized to evaluate the impact of these interactions on the actinyl symmetric stretching vibration (ν1) and absorption spectroscopy was used to confirm the oxidation state of the metal center. Our results indicate that the peak position of the (ν1) stretching modes varies with the formation of different actinyl species and actinyl-lithium interactions in solution. The influence of Li+ on the actinyl cation symmetric stretch increases in order of U(VI)O22+ &lt; Np(VI)O22+ &lt; Np(V)O2+ , with Np(V)O2+ being the only actinyl cation that engages in a redox reaction with increasing LiCl concentration.

Formation of actinyl-cation interactions and the impacts of Li+ on the actinyl cation vibrational bands in solution

ACS Spring 2022

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