Adsorption phenomena in the systems containing macrocyclic cavitand cucurbit [7]uryl

Abstract

Adsorption phenomena at the mercury electrode/cucurbit[7]uryl aqueous solutions are studied by the measuring of the electrode differential capacitance C as a function of potential E. The data obtained showed that the adsorption potential region is abnormally wide (>2 V). Two segments are observed in the C,E-dependences, which relate to adsorption layers with different structure. The complicated adsorption layers forming in the studied systems can be explained by the structure of the cucurbit[7]uryl cavitand whose complexes with inorganic cations are formed by the cation binding by oxygen-containing groups of external portals, rather than their inclusion into the cavitand’s inner cavity as in the case of cryptate formation. Adsorption parameters for adsorbate layers formed in the cucurbit[7]uryl + Na₂SO₄ solution are calculated. The data obtained evidence a rather strong potential dependence of the properties of the adsorption layers formed at the electrode/solution interface in the studied system.