1,2-FDTA: A ferrocene-based redox-active EDTA analogue with a high Ca2+/Mg2+ and Ca2+/Sr2+ selectivity in aqueous solution

Article abstract of DOI:10.1002/cber.19971301008

1,2-Ferrocenemethylenediyldiamino tetraacetate (1,2-FDTA) is a redox-active relative of EDTA and was synthesized in the reaction of l,2-bis(chloromethyl)ferrocene with iminodiacetate methyl ester followed by cleavage of the ester with methanolic KOH. Potentiometric determination of the stability constants of the complexes of 1,2-FDTA with the alkaline earth metal ions showed this ligand to display a higher Ca²⁺/ Mg²⁺ and Ca²VSr²⁺ selectivity (Ca²⁺ log K = 6.56, Mg²⁺ log K = 4.65, Sr²⁺ log K = 3.32) than EDTA itself. The redox potential of l,2-FDTA-Ca²⁺ determined in aqueous solution by cyclic voltammetry was found to be anodically shifted by +50 mV with respect to that of the calcium free complex. Consequently the redox-inactive calcium can be determined electrochemically in aqueous solution with a high selectivity with respect to the other alkaline earth metal ions. WILEY-VCH Verlag GmbH,.