ADSORPTION PROPERTIES OF CRYPTAND-222 AT THE CHARGED MERCURY-SOLUTIONINTERFACE

The adsorption of the macrocyclic ligand kryptofix 222 at the mercury- water interface has been studied as a function of the polarization pot ential and the ligand concentration. An automated apparatus has been u sed to measure interfacial tension by the drop-shape technique. The re lative surface excess and the surface charge density have been obtaine d, and from these parameters, the molecular packing at the interface a nd the free energy of adsorption have been calculated. The results sho w that the macrocyclic ligand strongly adsorbs at the interface in the presence of an intermolecular repulsive electrostatic contribution du e to Na+ cations trapped inside the macrocyclic cage. Moreover the ads orption driving force is similar to that reported for the adsorption o f aliphatic compounds, i.e., the hydrophobic repulsion of the exposed molecular surfaces.