ELECTROCHEMICAL-BEHAVIOR AND COMPLEXATION WITH ALKALI-METAL CATIONS OF REDUCED SYNTHETIC MACROCYCLIC-COMPOUNDS OF THE CROWN-ETHER TYPE ATTACHED TO AN ANTHRAQUINONE UNIT

The electrochemical characterization of synthetic crown ethers linked to an anthraquinone unit and aza-derived species, and their complexati on behaviour towards the alkali metal ions have bee, studied by cyclic voltammetry. These species undergo two one-electron reductions genera ting anion radicals and dianions which may show a larger cationic affi nity than their neutral form. Among the alkali cations, Li+ has the la rgest increase in its interaction with the reduced ligand when the mac rocyclic ring contains oxygen atoms in the binding sites, the increasi ng order being Li+ > Na+ > K+ > Rb+, Cs+. The substitution of two oxyg en ether atoms by two amine groups in the macroring cavity reduces the cation binding enhancement when the ligand is reduced with the cation order Na+ > K+ and there is no detectable complexation enhancement fo r Li+, Rb+ and Cs+.