Mobilities of cation-macrocyclic ligand complexes

Abstract

Formation constants for complexion between alkali metal cations and the crown ether 18C6 in the solvent 2-cyanopyridine at 30°C were determined from conductance measurements. The method allows for precise determination of these formation constants up to values of Kfaround 10 mol-1 dm3. The method also permits accurate evaluation of association equilibrium constants between the complex species (M-18C6)+ and the anion. The magnitudes of these ion association constants are related to the nature of the solvation of the cation and of the complexed cation. The mobilities of the complexes are also dependent, in part, upon solvation effects. In 2-cyanopyridine the single ion molar conductance of the (Li-18C6)+ complex is greater than that of the uncomplexed cation. Similar behavior is observed for alkali metal complexes with 18C6 and the cryptand 222 in other solvents such as propylene carbonate and propylene carbonate mixtures with dichloromethane. © 1993 IUPAC