STABILITIES OF THE IRON(III) CHELATES OF 1,2-DIMETHYL-3-HYDROXY-4-PYRIDINONE AND RELATED LIGANDS

The protonation constants and iron(III) binding constants of 1,2-dimethyl-3-hydroxy-4-pyridinone, DMHP, are reported and the effectiveness of this ligand in the complexation of iron(III) is compared with those of other iron(III) chelators at moderate and high dilution. The ligand is highly effective for Fe(III) in moderately dilute solution (approximately 10(-3) M), but because of its 3:1 stoichiometry, the most stable complex FeL3 dissociates extensively in very dilute solution (approximately 10(-6) M). The relative effectiveness of DMHP for iron(III) binding is compared with those of the bidentate ligands, acethydroxamic acid and catechol, and with the multidentate ligands desferriferrioxamine, diethylenetriaminepentaacetic acid, racemic ethylenebis(omicron-hydroxyphenylglycine), N,N'-bis(omicron-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, with the triscatechols MECAMS and enterobactin, as well as with the physiological iron(III) transport protein transferrin.