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(Invited) Ionic Fluids Containing Both Strongly and Weakly Interacting Ions of the Same Charge Have Unique Ionic and Thus Chemical Environments As a Function of Ion Concentration
(Invited) Ionic Fluids Containing Both Strongly and Weakly Interacting Ions of the Same Charge Have Unique Ionic and Thus Chemical Environments As a Function of Ion Concentration
Tuesday, 26 May 2015: 08:10
Marquette (Hilton Chicago)
Liquid multi-ion systems or Double Salt Ionic Liquids (DSILs; salts composed of more than two types of ions, liquid at low temperature (below 100 °C),[1]) made by combining two or more salts can exhibit charge ordering and interactions not found in the parent salts, leading to new sets of properties. This effect is investigated here by examining liquid systems made by mixing two miscible ionic liquids comprised of a single cation, 1-ethyl-3-methylimidazolium ([C2mim]+), and two anions with very different properties, acetate ([OAc]-) and bis(trifluoromethylsulfonyl)imide ([NTf2]-), namely [C2mim][OAc]x[NTf2](1-x), and made by dissolving a crystalline salt, ammonium acetate ([NH4][OAc]), in the ionic liquid [C2mim][OAc] in their miscible range, namely [NH4]x[C2mim](1-x)[OAc] (0 ≤ x ≤ 0.58). Through NMR and FT-IR spectroscopic analysis, we have shown that the electrostatic interactions present are quite different from those in the parent salts. We attribute this to the unique charge ordering arising from the ability of [OAc]- to form complexes with [C2mim]+ ions by drawing [C2mim]+ ions away from the less basic [NTf2]- ions or the ability of [NH4]+ cation to form complexes with [OAc]- ions by “stealing” [OAc]- from the less acidic [C2mim]+ ions. Solubility studies with various kinds of organic solutes (e.g., EtOAc, H2O, chloroform, benzene, tetrahydrofuran) and active pharmaceutical ingredients (ibuprofen and diphenhydramine) indicate that the solubilities of these solutes in the DSILs show dramatic, non-linear trends as a function of ion concentration, demonstrating that solubility of selected solutes can be finely tuned via changes in the ionic compositions. These kinds of DSILs provide potential solvent systems with unique and tunable properties to be used in the electrochemical and separation fields.
References
[1]. G. Chatel, J. F. B. Pereira, V. Debbeti, H. Wang and R. D. Rogers, Green Chem., 16, 2051 (2014).