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A fundamental understanding of thebehavior of actinides in ionicliquids is required to develop advanced separation technologies. Spectroscopicmeasurements indicate a change in the coordination of uranyl in thehydrophobic ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([EMIM][Tf2N]) as water is added to the system. Moleculardynamics simulations of dilute uranyl (UO22+) and plutonyl (PuO22+) solutionsin [EMIM][Tf2N]/water mixtures have been performed in orderto examine the molecular-level coordination and dynamics of the actinylcation (AnO22+); An = U, Pu) as the amount of water in the system changes. Thesimulations show that the actinyl cation has a strong preference fora first solvation shell with five oxygen atoms, although a highercoordination number is possible in mixtures with little or no water.Water is a much stronger ligand for the actinyl cation than Tf2N, with even very small amounts of water displacing Tf2N from the first solvation shell. When enough water is present,the inner coordination sphere of each actinyl cation contains fivewater molecules without any Tf2N. Water also populatesthe second solvation shell, although it does not completely displacethe Tf2N. At high water concentrations, a significant fractionof the water is found in the bulk ionic liquid, where it primarilycoordinates with the Tf2N anion. Potential of mean forcesimulations show that the progressive addition of up to five watermolecules to uranyl is very favorable, with ΔGranging from −52.3 kJ/mol for the addition of the first watermolecule to −37.6 kJ/mol for the addition of the fifth. Uranyland plutonyl dimers formed via bridging Tf2N ligands arefound in [EMIM][Tf2N] and in mixtures with very small amountsof water. Potential of mean force calculations confirm that the dimericcomplexes are stable, with relative free energies of up to −9kJ/mol in pure [EMIM][Tf2N]. We find that the self-diffusioncoefficients for all the components in the mixture increase as thewater content increases, with the largest increase for water and thesmallest increase for the ionic liquid cation and anion. The velocityautocorrelation functions also indicate changes in structure and dynamicsas the water content changes. [ABSTRACT FROM AUTHOR]

Theradiolytic production of molecular hydrogen in the ionic liquids N-trimethyl-N-butylammonium bis(trifluoromethanesulfonyl)imide([N1114][Tf2N]) and 1-ethyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide ([emim][Tf2N]) has beenexamined with γ-rays, 2–10 MeV protons, and 5–20MeV helium ions to determine the functional dependence of the yieldon particle track structure. Molecular hydrogen is the dominant gaseousradiolysis product from these ionic liquids, and the yields with γ-raysare 0.73 and 0.098 molecules per 100 eV of energy absorbed for [N1114][Tf2N] and [emim][Tf2N], respectively.These low yields are consistent with the relative insensitivity ofmost aromatic compounds to radiation. However, the molecular hydrogenyields increase considerably on going from γ-rays to protonsto helium ions with [emim][Tf2N] while they remain essentiallyconstant for [N1114][Tf2N]. FTIR and UV–visspectroscopic studies show slight degradation of the ionic liquidswith radiation. [ABSTRACT FROM AUTHOR]

Room-temperature ionic liquids (RTILs) are regarded asgreen solventsdue to their low volatility, low flammability, and thermal stability.RTILs exhibit wide electrochemical windows, making them prime candidatesas media for electrochemically driven reactions such as electro-catalysisand electro-plating for separations applications. Therefore, understandingthe factors determining edges of the electrochemical window, the electrochemicalstability of the RTILs, and the degradation products is crucial toimprove the efficiency and applicability of these systems. We presenthere computational investigations of the electrochemical propertiesof a variety of RTILs covering a wide range of electrochemical windows.We proposed four different approaches with different degrees of approximationand computational cost from gas-phase calculations to full explicitsolvation models. It was found that, whereas the simplest model hassignificant flaws in accuracy, implicit and explicit solvent modelscan be used to reliably predict experimental data. The general trendof electrochemical windows of the RTILs studied is well reproduced,showing that it increases in the order of imidazolium < ammonium< pyrrolidinium < phosphonium giving confidence to the methodologypresented to use it in screening studies of ionic liquids. [ABSTRACT FROM AUTHOR]