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 Fe 3+ 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 α-hydroxylic oxygen in the protonated or dissociated form depending on pH value. Two complex species [Fe 2GalA(OH) 4] and Na[FeGalAH −2] · 2H 2O are also isolated in the solid state and characterised through IR spectroscopy. GlcNAH also binds the Fe 3+ ion through carboxylic and hydroxylic groups, while NH 2 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.