Studies of cation binding by lariat ethers and thermodynamics of the complexation process

Cation binding studies of crown ethers have received much attention ever since the discovery that crown ethers bind alkali metals. While there have been extensive studies on crown ethers and their complexing abilities, the results are often inconclusive or incomplete. The studies presented here focus on how certain factors such as ring size, conformation, donor group polarity, lipophilicity, and solvation affect cation binding and selectivity of crown ethers. Results of binding studies are reported for series of aza-12-crown-4 lariat ethers, diaza-15-crown-5 lariat ethers, and diaza-18-crown-6 lariat ethers.The binding constants or the $\Delta$ G\u27s of the reactions have provided much information about binding ability and selectivity but, there is still a lack of comprehensive understanding of the binding phenomenon. To gain more information, the $\Delta$ H and T $\Delta$ S components of $\Delta$ G were measured for a number of lariat ethers. These values were obtained from the dependence of the stability constants on temperature. The enthalpy and the entropy data provide considerable insight into complexation