Complexation of metal ions by azocrown ethers in Langmuir-Blodgett monolayers

Monomolecular films of amphiphilic derivatives of crown ethers bearing an a zo group in the macrocycle were formed on the surfaces of pure water or aqu eous solutions of metal cations and transferred onto a thin mercury film el ectrode using the Langmuir-Blodgett technique. The properties of the monola yer modified electrodes were studied by voltammetry. The azocrown molecules assembled in monolayers at the air-solution and electrode-solution interfa ces were found to interact with selected alkali metal cations. This was rev ealed by the changes of the parameters of the surface-pressure and surface- potential isotherms recorded during the formation of monolayers at the air- solution interface, and by the electrochemical behaviour of the monolayer c overed electrodes. The stability constants of the complexes formed by Na+, K+ and Ca2+ cations with the neutral (K-ox) and reduced (K-red) forms of th e macrocyclic ligand in the monolayer, and the reaction coupling efficiency (K-ox/K-red), were calculated.