Neutral Ni(II) and Cu(II) complexes of tetraazatetraenemacrocyles

Abstract

A series of electron donors [neutral Ni(II) and Cu(II) complexes of tetraazatetraenemacrocyclic ligands] differing in metal ion, size of the macrocyclic ligand, and the length of the aliphatic bridges linking the macrocyclic units in dimeric species were synthesized and their redox, structural and spectroscopic properties were studied. The x-ray results for the donors under study show a nearly planar geometry of the monomeric tetraazamacrocyclic complexes and interesting ‘organic-zeolite-like’ structures of the dimers. The dimeric Ni complexes have flexible cavities between the two single ligands linked with aliphatic chains suitable for accommodating some small-sized guests. For the dimeric compounds the metal oxidation [M(II)/M(III)] takes place independently on each centre except one binuclear Ni complex, where the cooperativity of the metal centres was observed. Methyl substituents give rise to irreversibility of the oxidation process of the complexes studied. In the absence of these substituents neither reorganization nor ligand addition/elimination kinetics affect the electrode process. A common scale for the donors under study and some important acceptor compounds (p-benzoquinone, chloranil, tetracyanoethylene and tetracyanoquinodimethane, etc.) was proposed on the basis of their cyclic voltammetric behaviour in the same physicochemical conditions. Copyright © 2000 John Wiley & Sons, Ltd.