Invited Paper AC-ThA6
Structural Chemistry of M(IV) (M = Ce, Th, and U) Complexes Isolated from Aqueous Solution

Thursday, October 25, 2018, 4:00 pm, Room 202C

Understanding actinide metal ion speciation and reactivity is of great strategic and scientific importance, and relates to a number of areas ranging from waste management to separations chemistries. Speciation depends on oxidation state, and our knowledge of the structural and energetic properties of tetravalent actinide complexes is relatively limited in comparison to the higher valent oxidation states. This lack of structural and chemical information has resulted in large discrepancies in thermodynamic data, significant challenges in process chemistry, and unanticipated behaviors in environmental systems. As a means of filling this knowledge gap, we have been examining the solid-state structural chemistry of tetravalent Ce, Th, and U complexes obtained from aqueous solutions with an eye towards understanding the directing effects of inner and outer coordination sphere interactions. Moreover, using spectroscopic and X-ray scattering techniques, we have been probing the correlation between the precipitated phases and the solution phase species. Presented here will be an overview of recent efforts to elucidate the effects of both inner- and outer- coordination sphere interactions on the structural chemistry of tetravalent metal ion (Ce, Th, and U) complexes. How the synthetic conditions, identity of the counter-ions, and nature of complexing ligands affect the speciation and reactivity of the Ce(IV), Th(IV)- and U(IV)-building units will be discussed.