1,2‐FDTA: A Ferrocene‐Based Redox‐Active EDTA Analogue with a High Ca
2+
/Mg
2+
and Ca
2+
/Sr
2+
Selectivity in Aqueous Solution
摘要:
Abstract1, 2‐Ferrocenemethylenediyldiamino tetraacetate (1,2‐FDTA) is a redox‐active relative of EDTA and was synthesized in the reaction of 1,2‐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 Ca2+/Sr2+ selectivity (Ca2+ log K = 6.56, Mg2+ log K = 4.65, Sr2+ log K = 3.32) than EDTA itself. The redox potential of 1,2‐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.