Conductometric Studies on Cation-Crown Ether Complexes: A Review

Crown ethers have proved to be unique cyclic molecules for molecular recognition of suitable substrates by hydrogen bonds, ionic interactions, and/or hydrophobic interactions. The study of interactions involved in complexation of different cations with crown ethers in mixtures of solvents is important for a better understanding of the mechanism of biological transport, molecular recognition, and other analytical applications. This fundamental review summarizes different aspects of cation-crown ether complexes studied by conductometry in diverse solvent systems. A comprehensive literature summary is presented in tabular form for the complexation of cations with different crown ethers and their derivatives and other related crown ethers, highlighting their formation constant and thermodynamic parameters in diverse solvent media. Various factors that influence the stability and selectivity of cation-crown ether complexes have been discussed for thermodynamic consideration. Supplemental materials are available for this article. Go to the publisher's online edition of Critical Reviews in Analytical Chemistry to view the free supplemental file.