Synthesis and spectral properties of new bis(macrocyclic) nickel complexes and the influence of their structure and medium on electrochemical behaviour

Abstract

New bis(macrocyclic) dinickel complexes containing long polymethylene or xylylene bridges between macrocyclic subunits have been synthesised via template condensation of a nickel(II) open-chain amine complex with formaldehyde and symmetric α,ω-diamines. Spectral characteristics of the new complexes are typical of nickel(II) complexes with 14-membered tetraaza macrocycles. Electrochemical measurements revealed that the length of the linker exerts a rather moderate influence on the characteristics of Ni II/I and Ni III/II couples. On the other hand, the electrochemical behaviour of the complexes is influenced essentially by the nature of the solvent and supporting electrolyte. Thus, DMSO exerts an averaging effect on the interaction of the nickel(III) cation with anions while in DMF a pronounced dependence of the redox potentials on the length of the linker and the electrolyte is observed. The behaviour of the complexes in ACN is influenced to a large extent by the adsorption processes, the effectiveness of which is determined by the structure of the complex and the nature of the electrolyte.