Iron chelates of diethylenetriaminepentaacetic acid

The interaction of Fe(II) and Fe(III) ions with diethylenetriaminepentaacetic acid (DTPA) has been investigated by pH titration and redox titration measurements. The co-ordination of Fe(III) ions with this synthetic amino acid results in the formation of the following chelate species: Fe(III)-DTPA, Fe(III)-HDTPA, Fe(III)-(OH)DTPA. Similarly Fe(II)-DTPA exists in solution in the form of a Fe(II)-DTPA, Fe-(II)-HDTPA, Fe(II)-(OH)DTPA and Fe(II)-(OH)2DTPA. Equilibrium constants governing the existence of the various chelate forms have been calculated and probable chelate structures have been formulated on the basis of these quantitative data.