Anion—Cation Interactions in Molten Inorganic Nitrates: Vibrational Analysis

Wait, Samuel C.; Ward, A. T.; Janz, George J.

doi:10.1063/1.1727297

Cited by 65 publications

(14 citation statements)

References 21 publications

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“…This order is in accord with the order of increasing force constant for the metal-oxygen stretch in molten nitrates [17], Cs+< Rb+< K+< Li+< Na + [B], but disagrees with the order of increasing polarizing power of cations defined as (cation charge)/(cation radius), Cs + < Rb + < K + < Na + < Li + [C], which is the same as that noted for the extent of anion-cation interaction from N.M.R. studies of a series of chlorides [17].…”

Section: Mean-square Torquesupporting

confidence: 79%

Raman spectral studies of ionic motion and ionic interaction in aqueous nitrate solutions

1978

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The Raman spectra of the totally symmetric vl(Al') mode of an NO3-ion have been recorded in aqueous LiNO3, NaNO3, KNO3 and' NHINOa solutions at various concentrations. The vibrational and rotational correlation functions have been calculated from the Fourier transform of the Raman profiles. Reorientation of the symmetry axis of an NO3-ion in the aqueous solutions may be represented by the inertial motion for short times (t~< 0-t 5 ps, jump angle 17~ and by the rotational diffusion for longer times (t~>0"3 ps). An effective moment of inertia for short times has been found to be 1• = 20 • 10-39 gcm ~, which suggests, as compared with the free NO3-value i• 6 x 10-39g cm 2, some association with the surrounding water molecules or cations. The mean-square torque acting on an NO3-ion from the moment analysis has been found to increase linearly with nitrate concentration. The torque on an NO3-ion in concentrated nitrate solutions is predominantly from other ions, while the contribution from an NO3--water interaction is small. It is concluded that the vibrational band width of 6-13 cm -1 in these nitrate solutions is to be attributed to the pure vibrational dephasing, due to an NO3--water interaction in dilute solutions, and due to NO3--water and increased NO3--cation interactions in concentrated solutions. The contribution from the induced dipole-induced dipole resonance vibrational energy transfer has been found to be negligible.

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Section: Mean-square Torquesupporting

confidence: 79%

Raman spectral studies of ionic motion and ionic interaction in aqueous nitrate solutions

1978

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“…the 740 cm-' band observed in the infrared spectrum. Surprisingly, however, the separation of the components of v3(E1) decreases slightly as the concentration increases and no splitting is reported for the molten salt (27). The explanation may lie in the symmetry of the ion atmosphere surrounding the nitrate ion.…”

Section: + ( a D + No3 -( A Dmentioning

confidence: 72%

“…Raman bands at 1439, 1358, 1067, and 726 cm-' have been interpreted in terms of a contact ion pair in the melt with C,, or C, symmetry (27). The increasing separation of components of v3(E1) with increasing concentration has already been noted for aqueous solutions of LiNO, (see Fig.…”

Section: + ( a D + No3 -( A Dmentioning

confidence: 94%

Interactions in aqueous alkali metal nitrate solutions

Irish¹,

Davis²

1968

Can. J. Chem.

142

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Raman (R) and infrared (I) spectra of aqueous alkali metal nitrate solutions have been recorded at 25 "C for a wide range of concentrations. In dilute solution the nitrate ion is perturbed by solvent water; the effects attributed to cations are nonspecific. The solvated nitrate ion generates the following spectrum: 1404 cm-' (I, R), 1348 cin-' (I, R), 1049 cm-I (R), 825 cm-I (I), 719 cm-I (I, R). In more concentrated solutions band positions, intensities, and especially half-widths show a marked concentration and cation dependence. Changes in band half-width with concentration have been related to hydrated radii of the cations and are discussed in terms of interaction of solvated ions. For solutions of lithium and sodium nitrate more concentrated than 7 M a splitting of the v4(E1) mode of nitrate ion into components at 720 and 740 cm-' has been detected. Contact between ions is believed to account for the spectral changes observed for these high concentrations although water is shown to still markedly influence the interaction.Canadian Journal of Chemistry, 46. 943 (1968) Interactions between ions in concentrated of strong acids (7) and of complex ions (8). aqueous solutions of strong electrolytes, such as In addition to the number of modes of vibration, the alkali metal nitrates, which are responsible their activity and polarization properties, which for apparent deviations of observed properties together characterize a species, variations in from properties predicted from theories which vibrational frequency and the width of spectral assume complete dissociation are often de-lines provide information about environmental scribed in terms of "ion-pairs". Methods for the influences. evaluation of the dissociation constant of the Results of a detailed study of vibrational ion-pair have been summarized in two recent spectra of aqueous nitrate solutions of lithium, monographs (1, 2). For the alkali metal nitrates sodium, potassium, and cesium are described the values of these constants increase as the below. The Raman spectra of these systems have hydrated radius of the cation decreases (2). been described before. The fact that the intensity Prue has noted that factors outside the scope of of the v,(Alt) nitrate line (ca. 1050 cm-l) in the the simple electrostatic model must be important Raman spectra of alkali metal nitrates is proand suggests consideration of the molecular portional to concentration was considered to be nature of the solvent (3). The nature of these sufficient proof of complete dissociation (6). ion-pairs and their dependence on the solvent More recently small deviations from linearity is not well understood. The characterization of have been interpreted in terms of the influence of the solvent by its bulk properties and the neglect hydrated cations on the nitrate ion (9). of solvent structure seriously limit the classical Other bands in the Raman spectrum have theories (4). Ion-solvent interactions are not received less attention. Several authors have readily accommodated by the "sphere in con...

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“…The silver atoms are above the nitrate plane, off the C3-axis. It has even been suggested that silver ions are found in molten salt (27) in the same locations as they are in concentrated aqueous solutions (5 1).…”

Section: Introductionmentioning

confidence: 99%

Silver nitrate in aqueous solution and as molten salt: A molecular dynamics simulation and NMR relaxation study

Laaksonen¹,

Kovács²

1994

Can. J. Chem.

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A A~ LAAKSONEN AND HELENA KOVACS. Can. J. Chem. 72,2278Chem. 72, (1994. Using molecular dynamics simulations, the motion and intermolecular interactions of the ions of silver nitrate are studied in aqueous solution and compared to the results obtained from simulations of molten AgN0,. The particularly interesting and experimentally frequently studied modes of reorientational motion (in-plane and end-over-end) of the planar nitrate ion have been determined from the simulation results. In accordance with earlier experimental results, the correlation times for the endover-end rotation in aqueous solution are longer than those for the in-plane rotation, while the opposite is found to hold in the melt. In addition, the rotational motion of the nitrate ion in aqueous solution is experimentally studied using ' 4~ relaxation measurements. Good agreement is found between the reorientational correlation times obtained from MD simulations and from NMR relaxation measurements. [Traduit par la redaction]

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Anion—Cation Interactions in Molten Inorganic Nitrates: Vibrational Analysis

Cited by 65 publications

References 21 publications

Raman spectral studies of ionic motion and ionic interaction in aqueous nitrate solutions

Raman spectral studies of ionic motion and ionic interaction in aqueous nitrate solutions

Interactions in aqueous alkali metal nitrate solutions

Silver nitrate in aqueous solution and as molten salt: A molecular dynamics simulation and NMR relaxation study

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