Water-soluble hexadentate Schiff-base ligands as sequestrating agents for iron(III) and gallium(III)

Complexes of FeIII and GaIII with hexadentate Schiff-base ligands have been characterised in aqueous solution. They were prepared by the condensation of salicylaldehydes, containing a sulphonate or trimethylammonium group, with polyamines in the presence of the metal ions. These complexes have stabilities, at physiological pH, similar to those of the hydroxamic acid siderophore complexes. The kinetics of the displacement of FeIII from [FeIII(edta)]–(edta = ethylenediamine-N,N,N′,N′-tetra-acetate) by two of these ligands has been studied.