Utilizing Ionic Liquids as Bifunctional Reagents for the Ionothermal Synthesis of Uranyl Compounds

Abstract

The extraction of actinides, specifically uranyl and other actinyl ions, from fission products is a critical aspect of spent nuclear fuel reprocessing. In this study, ionothermal syntheses were conducted to control the formation of uranyl (UO2)2+ salt complexes generated by exposure to a selection of ionic liquids (ILs). The high-thermal stability and ligation potential of ILs were exploited in a multifaceted approach toward uranyl salt complexation by enabling ligation of the IL anionic component while simultaneously providing polar reaction media to promote speciation. Furthermore, an evaluation of uranyl complex templating by the IL cation revealed that small, heterocyclic cationic molecules resulted in more densely packed anionic clusters. The uranium source was also varied to determine the oxidizing effect of nitrate on the ILs and the propensity for nitrate and acetate byproduct formation. Uranyl triflate was found to be the optimal uranium source for the production of pure uranyl complexes. The degree to which nitrate oxidizes the ILs was investigated to determine what oxidation products form and subsequently coordinate to the uranyl ion. Finally, it was shown that a uranyl succinate framework can be synthesized in high yield from an IL that contains succinate as the anion.

Uranyl-Tc(vii)/Tc(v) hybrid clusters

“…Isolating SBUs as soluble molecular clusters (instead of insoluble lattices) is challenging, surmised from the paucity of published structures and solution phase studies. 3 a ,9 Prior-reported uranyl-hybrid materials exploit carboxylates, carboxyphosphonates, and halides as ligands, partly motivated by their prevalence in environmental, reprocessing, or waste storage environments. 8 b ,10 Uranyls linked by inorganic ligands (carbonate, 11 phosphate, 12 sulfate, 13 selenate, 13 a vanadate, 9 b molybdate, 14 silicate 15 ) expand uranyl solid-state chemistry and the understanding of complex mineral topologies.…”

Tc(VII)/Tc(V) direct coordination with secondary building unit of uranyl hybrid materials and their isolation as molecular cluster

“…Isolating the SBU building blocks as soluble molecular clusters (instead of infinite lattices) is challenging, as surmised from the paucity of published structures and solution phase studies. 4,18,19 Isolation and solution studies of SBUs can yield valuable information about assembly pathways of uranyl hybrid materials and minerals. The extended structures of SBUs have been synthesized using carboxylates, carboxyphosphonates, and halides, considering the prevalence of these functional groups in environmental, reprocessing, or potential long-term waste stewardship settings 16,[20][21][22] .…”

“…The extended structures of SBUs have been synthesized using carboxylates, carboxyphosphonates, and halides, considering the prevalence of these functional groups in environmental, reprocessing, or potential long-term waste stewardship settings 16,[20][21][22] . In addition, different inorganic ions such as carbonate 23 , phosphate [24][25][26] , sulfate 27,28 , selenate 27 vanadate 19 , molybdate 29 , silicate 30 etc. are used as linkers for SBUs in order to develop uranyl solid state chemistry and understand in complex mineral topologies.…”

“…In the extended structure the 2D framework stack on top of each other along c axis (Figure S2). The uranyl tetramer (UO2)4 containing hybrid materials has been published before [34][35][36] including recent report of their isolation as molecular cluster by Felton et al 2023 19 .…”

Thorium Cluster Synthesized by a Solvent-Free Flux Approach: The Richest Coordination Diversity and Application Exploration

“…The solvation environment plays a vital role in regulating the stability constant and coordination environment of solutes. − Solvent-free synthesis, such as ionothermal synthesis, , melting of azoles, and the use of deep eutectic solvents, , has been widely applied in coordination chemistry in view of its unique solvation environment. − Solvent-free synthesis represents a greener synthetic approach to eliminating radio-contaminated solvents when handling actinide compounds , and provides a unique solvation environment that may lead to reaction mechanisms different from those of traditional solvothermal methods, , offering a new opportunity to enrich the coordination diversity in Th clusters. Organic azoles, particularly triazoles with low melting point, attract our attention due to its widespread use in coordination chemistry .…”