Thermodynamic studies of iron(III) complex of some new dihydroxamic acids model of rhodotorulic acid

The objective of this research is to elucidate the coordination chemistry and the structure of complexes formed with siderochelates organic ligands and the physico-chemical studies of iron(III) complexation. Three dihydroxamic acids synthesized ((L-CyEt)(2-), (L-CyPr)(2-) and (L-O)(2-)) mimicking a fungal siderophore, rhodotorulic acid. They were evaluated with iron(III) chelation by potentiometric and spectrophotometric titrations in 0.1 M KNO3. These measurements revealed the formation of dileptic and trileptic complexes in excess ligand conditions. The chemical model includes five species of [Fe-m(L)(l)H-h]((3m - 2l) (+ h)+) with general formula: [Fe(L)](+), [Fe(L)(OH)], [Fe (L)(OH)(2)](-), [Fe(L)(2)H] and [Fe-2(L)(3)]. The numerical treatment of the spectrophotometric data collected in the visible range led us to propose the electronic absorption spectrum for each of the identified species. Moreover, electrospray ionization mass spectroscopy (ESI-MS) confirmed the formation of the monoleptic ([FeL](+)) and dileptic ([FeL2H]) complexes.