STRUCTURE OF IRON(III)-TIRON COMPLEXES IN AQUEOUS-SOLUTION

The structure of iron(III) complexes with 1,2-dihydroxybenzene-3,5-disulfonate (tiron4-) ion in aqueous solution has been studied by means of extended X-ray absorption fine structure (EXAFS) spectroscopy. EXAFS analyses of solutions containing [Fe(tiron)]-, [Fe(tiron)2]5- and [Fe(tiron)3]9- complexes as the main species, respectively, revealed that the complexes have an octahedral structure. The Fe-O bond lengths within the [Fe(H2O)6]3+, [Fe(tiron)(H2O)4]-, [Fe(tiron)2((H2O)2]5- and [Fe(tiron)3]9- complexes are 202(1), 205(1), 202(1) and 204(1) pm, respectively, and are practically the same as that within the [Fe(H2O)6]3+ ion (200 pm) determined by the X-ray diffraction method. The Fe-O distances are thus practically the same for all the complexes, within experimental uncertainties. The similar distances may reflect the pure electrostatic interaction between iron(III) ion and oxygen atom in ligands. © 1990, The Japan Society for Analytical Chemistry. All rights reserved.