Abstract

Thermodynamic values for cation-cyclic polyether interactions for several systems are reported and discussed in light of ligand geometry, cation selectivity, solvent effects, structure, stoichiometry and the nature of the coordinate bond. Cyclic polyethers are shown to be remarkably good ligands even in water and to have marked selectivity for d0, d10 and d10 s2 cations. Syntheses of one new cyclic polyether and several new mixed cyclic polyether-thioethers are reported. Cyclic chelates with smaller rings are shown to prefer smaller cations, but this selectivity is masked by the hydration energy of the cation. Except for thiophillic cations such as Hg2+ and Ag+, substituting sulfur for oxygen in the ligands reduces their complexing power. A large number of crystalline complexes of several cyclic polyethers were isolated containing over twenty different metallic cations. Most had stoichiometries of 1:1 (ligand:metal), but one had 1:2 and several had 2:1 stoichiometries. A unique oxonium complex was also prepared and characterized. A new technique for the separation of crown-31 isomers is outlined.

Degree

College and Department

Physical and Mathematical Sciences; Chemistry and Biochemistry

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