Complexation of Cu(II)M(II) (M=Cd, Co, Ni, Zn) heterodinuclear compounds of an octacoordinate hexaazamacrocyclic ligand

In this paper the investigation of the formation of HDTHCu heterodinuclear complexes of Zn(II), Cd(II),Co(II) and Ni(II) and HDTHCo heterodinuclear complexes with Ni(II) and Pb(II) in aqueous solution by control of the stoichiometry of metal ions and HDTH as well as p[H] of the solution (HDTH is a dinucleating 28-membered hexaazadiphenol macrocyclic ligand 3,7,11,19,23,27-hexaaza-33,34-dihydroxy-15,31-dimethyl-tricyclo-tetratriaconta-1(32),13,15,17(34),29(33),30-hexaene). The pH potentiometric method has been utilized successfully to determine formation constants while in turn determine the distribution of species present in the solution as a function of p[H]. Spectrophotometry was used to investigate the formation process of the heterodinuclear complexes. The X-ray crystal structures of two homodinuclear complexes of Cu(II) and Zn(II) are also reported. These results show that the two moieties of the ligand react with Cu(II) ions separately, functioning like two independent binding groups. These studies suggested that the Cu(II) complexes of the macrocyclic ligand can form the basis for discrete and stable heterodinuclear complexes and can be used to investigate the complexation in solution by taking Cu(II) as one moiety of the heterodinuclear complex.