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 complexation behaviour towards the alkali metal ions have bee, studied by cyclic voltammetry. These species undergo two one-electron reductions generating anion radicals and dianions which may show a larger cationic affinity than their neutral form. Among the alkali cations, Li+ has the largest increase in its interaction with the reduced ligand when the macrocyclic ring contains oxygen atoms in the binding sites, the increasing order being Li+ > Na+ > K+ > Rb+, Cs+. The substitution of two oxygen 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 for Li+, Rb+ and Cs+.