Properties of some ferrocene macrocyclic dioxotetraamines: the roles of aromatic side-arms

The coordination chemistry and electrochemical behavior of a series of ferrocene macrocyclic dioxotetraamines 1–4 each of which bears a pendant aromatic group and a malonic diamide fragment in their framework were investigated by electronic absorption spectroscopy and cyclic voltammetry. For the purpose of comparison, their model compounds 5–8 were also synthesized and studied. The stoichiometry of 1:1 for the complexes has been confirmed by FAB mass spectroscopy and UV–vis titration of Cu(II) ion with ligands 4 and 8. Stability constants for the equilibrium of the above complexes have been evaluated. The ferrocene ligands 1–4 can electrochemically recognize the transition metal ions (Co2+, Ni2+ and Cu2+), while those ligands with a complexible atom in the side-arm can stabilize selectively the uncommon state of Ni(III).