Solvent extraction, ligands applications

All these methods have found applications in theoretical considerations of numerous problems more or less directly related to solvent extraction. The MM calculated structures and strain energies of cobalt(III) amino acid complexes have been related to the experimental distribution of isomers, their thermodynamic stability, and some kinetic data connected with transition state energies [15]. The influence of steric strain upon chelate stability, the preference of metal ions for ligands forming five- and six-membered chelate rings, the conformational isomerism of macrocyclic ligands, and the size-match selectivity were analyzed [16] as well as the relation between ligand structures, coordination stereochemistry, and the thermodynamic properties of TM complexes [17]. 

Mixed donor macrocycles have been employed in a number of applications involving the separation or analysis of manganesetll). These include examples of use of such a ligand as the extractant in solvent extraction processes " and as the ionophore in membrane transport studies. 

Solvent extraction is a classical analytical technique used to determine the contents of various inorganic and organic species. Inorganic compounds are usually extracted after complexation with organic ligands. The technique also enables preconcentration of solutes and their separation and finds practical applications in various industries, including nuclear, metal processing, petrochemistry, pharmaceutical. 

Koryta reported the first FIT reaction in 1979 (25), and this method can not only provide the stoichiometric information between the ion and the ligand, thermodynamic and kinetic parameters, but can also have applications in selective amperometric ion sensors, and in electro-assisted solvent extraction across liquid membranes (1, 2, 6, 62). Various ionophores, such as crown ethers, antibiotics, ETH series ionophores and calixarenes, have been used to facilitate cations transfer (1-6). Recently anion transfers facilitated by ionophores have also been observed (63, 64). 

Since no special ligand design is usually required to dissolve transition metal complexes in ionic liquids, the application of ionic ligands can be an extremely useful tool with which to immobilize the catalyst in the ionic medium. In applications in which the ionic catalyst layer is intensively extracted with a non-miscible solvent (i.e., under the conditions of biphasic catalysis or during product recovery by extraction) it is important to ensure that the amount of catalyst washed from the ionic liquid is extremely low. Full immobilization of the (often quite expensive) transition metal catalyst, combined with the possibility of recycling it, is usually a crucial criterion for the large-scale use of homogeneous catalysis (for more details see Section 5.3.5). 

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