Iron(III) complexing ability of carbohydrate derivatives

A solution study on the coordinative ability of galactaric acid (GalAH(2)), D-glucosamine (GlcN) and D-glucosaminic acid (GlcNAH) toward Fe3+ ion is reported. UV spectroscopic study provides useful information to identify complex species formation and their stability constants are determined by means of potentiometric measurements. GalAH(2) behaves as chelating ligand through carboxylic oxygen and alpha-hydroxylic oxygen in the protonated or dissociated form depending on pH value. Two complex species [Fe(2)GalA(OH)(4)] and Na[FeGalAH(-2)](.)2H(2)O are also isolated in the solid state and characterised through IR spectroscopy. Glc-NAH also binds the Fe3+ ion through carboxylic and hydroxylic groups, while NH2 group is probably involved in metal coordiantion up to pH 4. GlcN demonstrates low ligating ability at acidic pH and does not prevent metal hydroxyde precipitation.