Comparison of selectivity of a family of chelating agents for trivalent (Al3+, Fe3+) and bivalent (Cu2+, Zn2+) metal ions

Chelation therapy is used for the treatment of metal intoxication in humans. Selectivity towards the target metal ion is one important characteristic of the chelating agent.
In the frame of our research of chelating agents for iron and aluminium, we synthesized five new ligands (Figure 1), and studied their behavior toward the trivalent metal ions. L4, L5, L6 and L8 were found to be excellent ligands for the coordination of Fe3+ and Al3+. We are presenting here a study on the same ligands with the two essential bivalent metal ions, Zn2+ and Cu2+. The results of spectrophotometric, potentiometric, and NMR measurements performed to determine the equilibrium formation constants will be presented. The speciation of the complexes with the trivalent metal ions in presence of endogenous zinc and copper will be discussed.