Conductance and Thermodynamic Study of Thallium and Silver Ion Complexes with Crown Ethers in Different Binary Acetonitrile–Water Solvent Mixtures

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The complexation reactions between Ag+ and Tl+ ions with 15-crown-5 (15C5) and phenyl-aza-15-crown-5 (PhA15C5) have been studied conductometrically in 90% acetonitrile-water and 50% acetonitrile - water mixed solvents at temperatures of 293, 298, 303 and 308 K. The stability constants of the resulting 1:1 complexes were determined, indicating that the Tl+ complexes are more stable than the Ag+ complexes. The enthalpy and entropy of crown complexation reactions were determined from the temperature dependence of the complexation constants. The enthalpy and entropy changes depend on solvent composition and the T Δ S0o –ΔH0 plot shows a good linear correlation, indicating the existence of entropy – enthalpy compensation in the crown complexation reactions.

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