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A Roadmap to Uranium Ionic Liquids: Anti-Crystal Engineering

TitleA Roadmap to Uranium Ionic Liquids: Anti-Crystal Engineering
Publication TypeJournal Article
Year of Publication2014
AuthorsYaprak, D, Spielberg, ET, Backer, T, Richter, M, Mallick, B, Klein, A, Mudring, AV
JournalChemistry-a European Journal
Volume20
Pagination6482-6493
Date Published05
Type of ArticleArticle
ISBN Number0947-6539
Accession NumberWOS:000335773800036
Keywords1-butyl-3-methylimidazolium, basis-sets, behavior, chloride, Crystal structure, density functional calculations, dithiocarbamate, extraction, Ionic liquids, IR, rn, solubilizing metal-oxides, spectra, Spectroscopy, uranium, uranyl complexes
Abstract

In the search for uranium-based ionic liquids, tris(N,N-dialkyldithiocarbamato)uranylates have been synthesized as salts of the 1-butyl-3-methylimidazolium (C(4)mim) cation. As dithiocarbamate ligands binding to the UO22+ unit, tetra-, penta-, hexa-, and heptamethylenedithiocarbamates, N,N-diethyldithiocarbamate, N-methyl-N-propyldithiocarbamate, N-ethyl-N-propyldithiocarbamate, and N-methyl-N-butyldithiocarbamate have been explored. X-ray single-crystal diffraction allowed unambiguous structural characterization of all compounds except N-methyl-N-butyldithiocarbamate, which is obtained as a glassy material only. In addition, powder X-ray diffraction as well as vibrational and UV/Vis spectroscopy, supported by computational methods, were used to characterize the products. Differential scanning calorimetry was employed to investigate the phase-transition behavior depending on the N,N-dialkyldithiocarbamato ligand with the aim to establish structure-property relationships regarding the ionic liquid formation capability. Compounds with the least symmetric N,N-dialkyldithiocarbamato ligand and hence the least symmetric anions, tris(N-methyl-N-propyldithiocarbamato)uranylate, tris(N-ethyl-N-propyldithiocarbamato)uranylate, and tris(N-methyl-N-butyldithiocarbamato)uranylate, lead to the formation of (room-temperature) ionic liquids, which confirms that low-symmetry ions are indeed suitable to suppress crystallization. These materials combine low melting points, stable complex formation, and hydrophobicity and are therefore excellent candidates for nuclear fuel purification and recovery.

DOI10.1002/chem.201303333
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