Selective complexation of copper ions in monolayers of a new amphiphilic cage molecule at the liquid/air and liquid/liquid interfaces
Résumé
We report studies of a newly synthesized cyclam derivative with four chain substituents (tetra-(N-2-tetradecyl-carboxamidoethyl)-tetraazacyclotetradecane; TC14) which could be of interest for the selective liquid–liquid extraction of cations. We investigated the monolayer properties of TC14 molecules spread at the aqueous solution/air interface by surface pressure–area isotherm measurements and Brewster angle microscopy. Surface pressure–area isotherms measurements were also performed at the aqueous solution/decane interface with a new interfacial Langmuir trough. The effects of the salt concentration in solutions (CuCl2, NaCl and CsCl) on the TC14 surface pressure–area isotherms were related to the binding of the cations to the cage molecule at the interface. It was found that the film was sensitive to the presence of ions in the aqueous phase, particularly in the high-pressure region of the isotherm, where the film collapses. The Langmuir balance technique revealed the preferential complexation of Cu2+ ions by the cage molecule in the interface and permitted us to detect the presence of very small ion concentrations in the subphase.