Solution and solid-state investigations of actinides-halides have been foundational to understanding the complexes that exist within nuclear waste management and separations scenarios, as well as discerning covalency in the 5f-block. Yet, the impact that outer coordination sphere interactions have on the speciation, stability, and properties of tetravalent actinide-halide phases is relatively unexplored. In this work, we have examined the formation and composition of U(IV) chloride complexes isolated from acidic aqueous solutions containing non-coordinating pyridinium cations. A series of compounds built from UCl62- structural units charge-balanced by pyridinium derivatives functionalized with various electron donating and withdrawing groups were prepared. Functionalization of the pyridinium cations was pursued with an eye towards understanding the effects of hydrogen bond donor strength on species formation as well as the spectroscopic properties of the resulting phases. While the identity of the pyridinium cation had little effect on the U(IV) building unit observed in the solid state, changes in the spectroscopic signatures of these compounds attributed to U-Cl---HN- outer coordination sphere interactions were observed. Presented here are the structural and spectroscopic (Raman and fluorescence) characterization of the isolated compounds.

Effects of pyridinium counter-ions on the structure and properties of novel UCl62- compounds

256th National Meeting (2018)

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