A new diazacyclooetane dihydroxamate as a siderophore analogue - Synthesis and equilibrium studies of iron(III) and copper(II) complexes

A new siderophore analogue based on the mesocyclic diamine 1,5-diazacyclooctane (DACO) functionalized with two additional hydroxamate donor pendant groups, 1,5-diazacyclooctane-1,5-bis(N-methylacetohydroxamic acid) (DACODMAHA), has been synthesized from the corresponding diacetate derivative (DACODA). The complexation behaviour of this ligand towards Cu-II and Fe-III in aqueous solution has been studied by potentiometry, UV/Vis and EPR spectroscopy and magnetic moment measurements. The Cu-II complexation involves the formation of a mononuclear species with a tetradentate mixed amine/hydroxamate coordination mode, whereas the Fen, complexation involves a binuclear species with Fe2L3 stoichiometry and normal {O,O}-hydroxamate coordination mode. The redox potential of the iron complexes and the corresponding electron transfer mechanism are also evaluated.