Electrochemical behaviour of tetraazamacrocyclic nickel(II) complexes functionalized with crown ethers

Abstract Tetraazamacrocyclic nickel(II) complexes linked by the system of conjugated double bonds with one or two benzo-15-crown-5 moieties ( 2Ni and 3Ni ) were synthesized and characterized. The CV of these complexes in acetonitrile (ACN) solution exhibited reversible Ni II/III redox process. At more positive potentials oxidation of the bezno-15-crown-5 ether (B15C5) moiety was found. In complexes 2Ni and 3Ni redox potential of Ni II/III did not change after the interactions of alkali and alkaline earth metal cations with B15C5 unit. However, the presence of guest cations caused a significant change of B15C5 oxidation potential. Complexation of two Cl − anions to the coordinated Ni II in 2Ni and 3Ni resulted in an appreciable shift of both Ni II/III and B15C5 redox processes after addition of metal cations. Behaviour of complexes 2Ni and 3Ni was compared with behaviour of similar Cu II complexes.