Ions in Mixed Solvents

The physical and chemical properties of (binary) solvent mixtures, necessary for understanding the solvation of ions in the mixtures, are dealt with in Sections 3.4.1 and 3.4.2, respectively. The preferences of ions for certain solvents over others are described in terms of their standard molar Gibbs energies of transfer from a source solvent (water has generally been arbitrarily selected as this source) to neat target solvents in Section 4.3.2.I. These sections should be consulted to complement the present discussions regarding ions in mixed solvents. 

Ions in Solution and Their Solvation, First Edition. Yizhak Marcus. 

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Haque, R., Reeves, L. W. Coupling Constant and Chemical Shift of Tetrafluoroborate Ion in Mixed Solvents. J. Chem. Phys. 70, 2753 11966). 

The treatment of all those properties of electrolyte solutions, where selective solvation of ions in mixed solvents may play a major role, would result in an accumulation of data hard to follow up. Therefore, only those theoretical treatments of ion solvation have been mentioned in the following whose results have been used to ... 

While in the methods treated before ion solvation represents the sum of various terms of ion-solvent interaction, spectroscopic methods are mainly, if at all, sensitive to the immediate environment of an ion. Due to this the coordination model, representing the primary solvation shell, is not only used for highly charged ions but also for univalent ions. The precise results of the direct ion-solvent interactions made it possible to evaluate equilibrium constants describing the composition in the solvation shell of an ion in mixed solvents. Therefore, the estimation of single ion free ener es of transfer from spectroscopic measurements is the subject of several recent efforts and is theme of Part III. 

Thermodynamic Properties of Transfer for Single Ions in Mixed Solvents... 

Table 1. Free energies of transfer and some other thermodynamic properties of transfer for single ions in mixed solvents...

In order to simplify the determination of free energies of transfer, Covington et deduced a relation between AG and the chemical shifts of ions. It is well known that the chemical shift of alkali metal and halide ions in mixed solvents e.g. 

The results of investigations on electrode kinetics of various solvated metal ions in mixed solvents were obtained mostly with the use of the mercury electrode. Although explanations of kinetic data obtained with such electrodes are simpler than with solid electrodes, the understanding and detailed description of the observed changes is still not satisfactory. A reasonable explanation was only given for the results obtained in water-rich solutions for the case when a decrease in the rate of the electrode reaction occurs. 

The signiflcant recent advances in both colloidal and polymer chemistries have enabled the successful fabrication of complex, defect-free tianoslruclures following a bottom-up approach [353]. Two recent related examples are mentioned to stress the point. Recently, triblock copolymer with divalent counter-ions in mixed solvents led to the formation of particles with tunable internal structure mimicking lipid anphiphiles for potential use in drug delivery. The mechanism of formation involves either nanophase separation within the triblock copolymer nanoparticle upon addition of water or microemulsion formation similar to that in lipid systems... 

In the above sections, coextraction of ions into water-immiscible solvents has been elucidated in terms of selective hydration of ions in mixed solvents. However, it has frequently been asked whether water molecules are actually bound with ions in organic solvent. Nevertheless, there seems to be no doubt about it, since the selective hydration of hydrophilic ions in water-miscible and -immiscible solvents has been confirmed by solubility... 

Marcus, Y. 1983. A quasi-lattice, quasi-chemical theory of preferential solvation of ions in mixed solvents. Australian Journal of Chemistry. 36,1719. 

DYNAMIC PROPERTIES OF WATER MOLECULES IN HYDRATION SHELLS OF IONS IONIC HYDRATION UNDER EXTREME CONDITIONS IONIC SOLVATION IN NONAQUEOUS SOLVENTS PREFERENTIAL SOLVATION OF IONS IN MIXED SOLVENTS THEORETICAL CONSIDERATION OF IONIC SOLVATION CONCLUSION REFERENCES... 

Halide Ions in Mixed Solvent and Non-Aqueous Solutions... 

Quadrupole relaxation of ions in mixed solvents has been examined both theoretically and experimentally by Holz et at, [522],... 

As said above, the properties of ions in solvent mixtures generally do not depend linearly on the bulk solvent composition (whether in mole or volume fractions). The deviations of the properties from the linear dependence throw light on the interactions that take place between the ions and the components of the solvent mixture and between the latter. In the following, thermodynamic and dansport properties are dealt with. Only binary solvent mixtures are handled within the scope of this book, but extension toward multicomponent mixtures should be straight-forward. The information concerning the properties of ions in mixed solvent is very extensive, and hence only representative examples are dealt with here. 

Similar cases of specific interactions have been found also for the partial molar volumes of electrolytes (ions) in mixed solvents. The reports concerning the partial molar volumes of electrolytes in mixed solvents generally do no pertain to dilute solutions of the cosolvent, but on the contrary, most such studies cover the entire composition range. The curves tend to be very asymmetric in the solvent composition and changes in direction are often encountered, as shown, for example, in Figure 6.1 for some electrolytes in aqueous DMSO according to Letellier et al. [30]. In a few cases were very dilute solutions were studied, so that pair-interaction parameters could be... 

T1 NMR has been used to determine ion-pair formation constants and the thermodynamic parameters of ion-pairing processes for T1(I) salts in a number of solvents. The values of ion-pair formation constants have been found to be dependent on the dielectric constant of the solvent. A correlation between the 205 1 chemical shift and the DN of the solvent has been indicated the more basic the solvent, the lower the shielding of the TB ion. There have also been numerous studies of the preferential solvation of the TB ion in mixed solvent systems. The relative solvating abilities were analysed in terms of solvent donor-acceptor properties and the solvent DN was found to be most important in the preferential solvation. 

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