Proton Magnetic Resonance Solvation Study of Sc(NO3)3, Y(NO3)3, and Th(NO3)4 in Water–Acetone Mixtures

Abstract

Nonideality in diffusion of ionic and hydrophobic solutes and pair dynamics in water-acetone mixtures of varying compositionCation coordination measurements of Sc(NOa)a, Y(NO a )8, and Th(NO a )4 in water-acetone mixtures have been made by a proton magnetic resonance method. At low temperatures, solutions of these salts exhibit separate proton resonance signals for bulk water and water molecules in the primary solvation shell of the cation. Integration of these signals provides a direct measure of the number of water molecules coordinated to the cation. Values of 3.9, 2.4, and 2.9 were obtained for Sc(In), Y(In), and Th(IV), respectively, over a range of salt and solvent concentrations. These values may reflect extensive ion pairing in these solutions, particularly in the Y(nI) and Th(IV) cases. The PMR spectra of Th(IV) solutions revealed multiple signals for the protons of coordinated water molecules, lending evidence to the postulate of ion pairing in these systems.

Proton Magnetic Resonance Studies of Ionic Solvation in Ion-exchange Resins. Part III. Multivalent Counterions

“…Ion pairing has been postulated in mixed aqueous and non-aqueous solutions of electrolytes to account for the decrease in the measured hydration number at the concentrations similar t o those prevailing in the resin phase (39,40). In contrast to the resin phase, however, cations and anions are both mobile in these systems; furthermore, the diffiision coefficients of the ionic species are also higher due to the relatively lower viscosity of the homogeneous phase.…”

A proton magnetic resonance coordination number and ion-pairing study of GaCl3, GaBr3, GaI3, Ga(NO3)3and Ga(ClO4)3in acetone-water mixtures

“…studies of A13+ [12,14,[16][17][18], Mg 2+ [12,13,21] and Ga z+ [12,19] in water-acetone mixtures. In the gallium halide solutions studied here, solvation by acetone can be induced only by lowering the water to Ga ~+ mole ratio to 3 : 1 or less, at which point a signal for complexed acetone is observed at -50~ 36 HZ downfield from the bulk peak.…”

“…Recently we demonstrated that by cooling concentrated, pure aqueous solutions of many cations, or more dilute samples of these cations in aqueous solvent mixtures, proton exchange could be slowed sufficiently to permit the direct observation of signals for the protons of bulk water and water in the ion solvation shell [11][12][13][14][15][16][17][18][19][20]. Like the oxygen-17 method, this technique provides an accurate and quantitative measure of an ion coordination number, but it requires only readily available Downloaded by [Tulane University] at 16:57 21 June 2016 instrumentation, no sample enrichment, and it is much more versatile.…”

“…For example, in addition to knowing the hydration number of an ion in solution, it is of fundamental importance to know how the extent of hydration is affected by the particular anion, or by the presence of a non-aqueous solvent component. Previous studies have already dealt with the hydration numbers of A1 a § Be 2 § Ga a+, In a+ and Mg 2+ in water and water-acetone mixtures [11][12][13][14], the extent of competitive or selective solvation of A1 a+ in aqueous mixtures of acetone, dimethylformamide, dioxane, tetrahydrofuran, tetramethylurea, dimethylsulphoxide, and other sulphoxides and sulphones [15][16][17], and the cation hydration number and extent of ion-pairing in aqueous-acetone solutions of GaCla, Sc(NO8)8, Y(NOa)a and Th(NOa)4 [18,19]. Mg 2 § in water and aqueous-acetone solutions [21], A1 a+ in aqueous-acetonitrile solutions [22], and Co 2+ in water [23] also have been studied by this method.…”

Raman, infrared, and proton magnetic resonance investigation of solutions of zinc nitrate in anhydrous methanol

“…spectra of solvent molecules bound to cations is now an accepted technique. The majority of reported solvation numbers are, within experimental error, equal to 6 (1-6), although lower values have been reported (7-lo), and assumed to reflect the replacement of solvent molecules by anions in the first coordination shell of the cation (9,10).…”