Kinetics and mechanism of iron exchange in a hydroxamate siderophore analogue complex

Abstract

The kinetics of iron release from the dinuclear iron(III) complex of piperazine-1,4-bis(N-methylaceto-hydroxamic acid), upon treatment with ethylenediaminetetraacetate (edta) has been studied using UV/VIS absorption spectrophotometry. The absorbance vs. time evolution of the complex is well described by a consecutive two-step reaction mechanism. The rate constants for removal of the first and the second iron(III) ions have different dependences on the edta concentration. This is attributed to different conformations of the ligand involved in the co-ordination of di-and mono-iron(III) complexes. The increase in the rate constants with the acidity of the medium probably results from changes in conformation and the degree of co-ordination of the complexes. The results are compared with published studies for iron release from transferrins.