Ion-ion-solvent interactions in solution. I. Solutions of LiClO4 in acetone

1982 ◽  
Vol 35 (9) ◽  
pp. 1775 ◽  
Author(s):  
DW James ◽  
RE Mayes
Keyword(s):  
Raman Band ◽  
Ion Pairs ◽  
Ion Association ◽  
Solvent Interactions ◽  
Solvation Numbers ◽  
Solvated Ions ◽  
Component Band ◽  
Li Ion ◽  
Contact Ion Pairs ◽  
Association Equilibrium

Vibrational spectra and 7Li, 13C and 35Cl n.m.r. spectra have been obtained for solutions of LiClO4 in acetone for salt concentrations from 0.05 to 6 M. Infrared spectra give qualitative indications of ion association. Analysis of the Raman band due to C-C stretching in acetone yields solvation numbers for the Li+ ion of the order of 3. Component band analysis of the ClO4- symmetric stretching vibrational band and the various n.m.r. spectra lead to the identification of solvent-separated ion pairs, contact ion pairs and ion aggregates, in addition to free solvated ions. The dependence on salt concentration of all four species has been determined. The association quotient for the association equilibrium (Li+)s(ClO4)- ↔ [Li+(acetone)ClO4-)s was determined to be 1.4 � 0.3 dm3 mol-1.

Ion-ion-solvent interactions in solution. Aqueous solutions of nitrates of cations from Groups 2A and 3A

1982 ◽  
Vol 35 (9) ◽  
pp. 1793 ◽  
Author(s):  
DW James ◽  
RL Frost
Keyword(s):  
Aqueous Solutions ◽  
Ion Pairs ◽  
Ion Pair ◽  
Band Shape ◽  
Nitrate Ion ◽  
Solvent Interactions ◽  
Contact Ion Pair ◽  
Component Band ◽  
Association Equilibria ◽  
Contact Ion Pairs

Association equilibria in aqueous solutions of the salts Be(NO3)2, Ca(NO3)2 Sr(NO3)2, Ba(NO3)2 and Al(NO3)3 have been studied through band shape and component band analysis of the non-degenerate, Raman-active V1 vibrational band of the nitrate ion. Band contributions due to the aquated nitrate ion, solvent-separated ion pair, and contact ion pair were made for all salts. The nature of the contact ion pair was shown to be different in the presence of Be2+ and Al3+ from that seen for the other salts. This difference was associated with a strongly directional perturbation of the nitrate ion. For all salts the solvent-separated ion pair species was present in the lowest concentration solution studied (as low as 0.05 M). At intermediate concentrations the solvent separated ion pair species was the dominant solution species while at the higher concentrations the species with anion and cation in contact becomes appreciable. For solutions of Ca(NO3)2 some evidence for a more extensive ion aggregate was found at the highest concentration (5M). Equilibrium quotients calculated from the spectroscopic components are in reasonable agreement with previous values determined by equilibrium and transport measurements, and it is suggested that these previous determinations detected the presence of solvent-separated ion pairs rather than contact ion pairs.

scholarly journals When spectroscopy fails: The measurement of ion pairing

2006 ◽  
Vol 78 (8) ◽  
pp. 1571-1586 ◽  
Author(s):  
Glenn Hefter
Keyword(s):  
Metal Ion ◽  
Chemical Speciation ◽  
Ion Pairs ◽  
Ion Association ◽  
Ion Pair ◽  
Association Constants ◽  
Spectroscopic Techniques ◽  
Association Equilibria ◽  
Solvent Molecules ◽  
Contact Ion Pairs

Spectroscopic techniques such as UV/vis, NMR, and Raman are powerful tools for the investigation of chemical speciation in solution. However, it is not widely recognized that such techniques do not always provide reliable information about ion association equilibria. Specifically, spectroscopic measurements do not in general produce thermodynamically meaningful association constants for non-contact ion pairs, where the ions are separated by one or more solvent molecules. Such systems can only be properly quantified by techniques such as dielectric or ultrasonic relaxation, which can detect all ion-pair types (or equilibria), or by traditional thermodynamic methods, which detect the overall level of association. Various types of quantitative data are presented for metal ion/sulfate systems in aqueous solution that demonstrate the inadequacy of the major spectroscopic techniques for the investigation of systems that involve solvent-separated ion pairs. The implications for ion association equilibria in general are briefly discussed.

A Raman spectral study of solvation and ion association in the systems LiAsF6/CH3CO2CH3 and LiAsF6/HCO2CH3

1991 ◽  
Vol 69 (11) ◽  
pp. 1766-1773 ◽  
Author(s):  
Zhongyi Deng ◽  
Donald E. Irish
Keyword(s):  
Methyl Acetate ◽  
Methyl Formate ◽  
Ion Pairs ◽  
Lithium Ion ◽  
Ion Association ◽  
Ion Solvation ◽  
Lithium Cation ◽  
Different Types ◽  
Raman Spectral ◽  
Contact Ion Pairs

The structure of the solvated lithium cation in methyl acetate (MA) solutions has been investigated using Raman spectroscopy. Two bands at 844 and 864 cm−1 have been assigned to two different types of MA: the former is from the bulk solvent and the latter arises from MA molecules solvating the lithium cation. From measurement of changes in intensity of these bands with increasing salt concentration a solvation number of four for Li+ in MA has been inferred. Changes in the Raman bands at ca. 1740 cm−1 suggest that solvation occurs through the carbonyl group. Evidence for contact ion pairing between Li+ and AsF6− is also presented. An equilibrium between solvent-shared ion pairs and contact ion pairs is proposed for which an equilibrium constant is estimated. The system LiAsF6/methyl formate (MF) is similar in structure. Key words: Raman, ion pair formation, lithium and hexafluoroarsenate ions, methyl acetate and formate, lithium ion solvation.

Ion Ion Solvent Interactions in Solution .XI. Spectroscopic Studies of Group-2 Perchlorates in Acetone

1986 ◽  
Vol 39 (1) ◽  
pp. 149 ◽  
Author(s):  
DW James ◽  
PG Cutler
Keyword(s):  
Raman Spectra ◽  
Spectroscopic Studies ◽  
Solvent Interactions ◽  
Solvation Numbers ◽  
Steric Crowding ◽  
Component Band ◽  
Group 2 ◽  
Association Equilibria ◽  
High Level ◽  
Ion Species

Solutions of Mg(ClO4)2 and Sr (ClO4)2 in acetone have been studied at various concentrations up to saturation by using infrared absorption, Raman scattering and multinuclear n.m.r (1H, 13C, 17O, 25Mg, 35Cl). Solvation numbers of c. 4.5 (Mg2+) and c. 5.5 (Sr2+) were determined from component band analysis of the c. 800 cm-1 acetone band in the Raman spectra. The solvent shell about the Mg2+ had a high level of steric crowding. There was a small amount of solvent-shared ion-pair formation at all oncentrations in solutions of Mg(ClO4)2 which showed little concentration dependence. In solutions of Sr (ClO4)2 there was evidence for the formation of both solvent-shared associated-ion species and ion-contact species. The solvent-shared species appeared to have two alternative configurations in one of which the anion was both polarized and highly hindered. There was a salt-promoted reaction in which the perchlorate was reduced to chloride and the solution darkened. This reaction prevented the use of Raman spectra to quantify the association equilibria.

Ion Association in Polymer Electrolytes; A Raman Study of Poly (Propylene Oxide) Based Complexes

1988 ◽  
Vol 135 ◽  
Author(s):  
M. Kakihana ◽  
S. Schantz ◽  
L.M. Torell ◽  
L. Borjesson
Keyword(s):  
Salt Concentration ◽  
Ion Pairs ◽  
Ion Association ◽  
Major Effect ◽  
Polymer Complexes ◽  
Ion Interactions ◽  
Different Temperatures ◽  
Component Band ◽  
Raman Study ◽  
Poly Propylene

AbstractRaman spectra of a series of PPO-LiClO4 and PPO-NaCF3SO3 complexes have been obtained for different temperatures and salt concentrations to study the various ion associations of the dopant salt. It was found that ion-ion interactions dramatically influenced the internal symmetric stretching modes ν1 of the anions. Splitting of ν1 into a multicomponent band was observed. The intensity profile of the band was found to change rapidly with salt concentration and temperature. A three component band analysis led to the identification of dissociated ions, ion pairs and multiple ion aggregates, respectively. Increased ion association with increased temperature and/or salt concentration was observed for both LiCIO4- and NaCF3SO3- complexes. It is likely to initiate the phase separation and salt precipitation observed in many salt-polymer complexes at higher temperatures. Considerably stronger ion-ion interaction was observed in the NaCF3SO3-system than in the LiCIO4-complex, which may explain the lower conductivities reported for PPO-NaCF3SO3 electrolytes. The drastic conductivity drop observed in both systems at higher salt concentrations can however only partly be due to a decreased concentration of “free” ions, the major effect being attributed to decreased ion mobility.

Ion-ion-solvent interactions in solution. II. Solutions of LiClO4 in diethyl ether

1982 ◽  
Vol 35 (9) ◽  
pp. 1785 ◽  
Author(s):  
DW James ◽  
RE Mayes
Keyword(s):  
Diethyl Ether ◽  
Vibrational Spectra ◽  
Salt Concentration ◽  
Ion Pairs ◽  
Solvent Interactions ◽  
Free Ions ◽  
Contact Ion Pairs ◽  
Solvate Molecule

.Vibrational spectra and 35Cl, 13C, 7Li and 1H n.m.r. spectra of anhydrous solutions of LiClO4 in diethyl ether have been studied. There is no evidence for the formation of free ions down to 0.1 M concentration of salt. Two salt species having concentration-dependent distributions are identified, these being contact ion pairs and ion aggregates. The salt species are solvated with one mole of solvent per mole of salt. The preferred conformation of the diethyl ether solvate molecule is trms-gauche. For pure dlethyl ether at 25°C the trans-trans → trans-gauche equilibrium has ΔH 5.85 kJ mol-1 and ΔS 19.5 J K-1 mol-1. The ΔH value is not influenced by the presence of salt, but ΔS increases as the salt concentration increases until at 4 M LiClO4 the value is 37.6 J K-1 mol-1.

Formation of Contact Ion Pairs and Solvation of Li+Ion in Sulfones: Phase Diagrams, Conductivity, Raman Spectra, and Dynamics†

2010 ◽  
Vol 55 (5) ◽  
pp. 1958-1964 ◽  
Author(s):  
Dmytro O. Tretyakov ◽  
Vitaly D. Prisiazhnyi ◽  
Malik M. Gafurov ◽  
Kamil Sh. Rabadanov ◽  
Sviatoslav A. Kirillov
Keyword(s):  
Phase Diagrams ◽  
Raman Spectra ◽  
Ion Pairs ◽  
Li Ion ◽  
Contact Ion Pairs

Ion Pairing and Dielectric Decrement in Glycosaminoglycan Brushes

2020 ◽  
Author(s):  
James Sterling ◽  
Wenjuan Jiang ◽  
Wesley M. Botello-Smith ◽  
Yun L. Luo
Keyword(s):  
Molecular Dynamics ◽  
Ion Pairs ◽  
Mean Field ◽  
Salt Bridge ◽  
Ion Pairing ◽  
Donnan Potential ◽  
Mean Field Models ◽  
Ion Exclusion ◽  
Dynamics Simulations ◽  
Contact Ion Pairs

Molecular dynamics simulations of hyaluronic acid and heparin brushes are presented that show important effects of ion-pairing, water dielectric decrease, and co-ion exclusion. Results show equilibria with electroneutrality attained through screening and pairing of brush anionic charges by cations. Most surprising is the reversal of the Donnan potential that would be expected based on electrostatic Boltzmann partitioning alone. Water dielectric decrement within the brush domain is also associated with Born hydration-driven cation exclusion from the brush. We observe that the primary partition energy attracting cations to attain brush electroneutrality is the ion-pairing or salt-bridge energy associated with cation-sulfate and cation-carboxylate solvent-separated and contact ion pairs. Potassium and sodium pairing to glycosaminoglycan carboxylates and sulfates consistently show similar abundance of contact-pairing and solvent-separated pairing. In these crowded macromolecular brushes, ion-pairing, Born-hydration, and electrostatic potential energies all contribute to attain electroneutrality and should therefore contribute in mean-field models to accurately represent brush electrostatics.

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