A Study of the Polarographic Behavior of N,N'-Ethylenebis-[2-(o-hydroxyphenyl)] glycine in the Presence of Iron Ions.

Plants can utilize iron form Fe‐N,N'‐di‐(2‐hydroxybenzoyl)‐ethylenediamine‐N,N'‐diacetic acid, a ferric chelate with 106greater formation constant than Fe‐EDDHA.

“…Unfortunately, no one has published Fe 2 " 1 " stability constants for HBED, although there is no reason to expect this value to exceed the Zn 2 * constant since the phenolic ligands are not known to favor Fe 2 " 1 " chelation. Schroder (1964b) used polarography to estimate the Fe 2+ EDDHA constarA: at 14.26; the data reported weakly support this estimate.…”

Electrochemistry of Iron(II/III)‐N,N'‐ethylene‐bis‐(o‐hydroxyphenylglycine) Complexes in Aqueous Solution Indicates Potential for Use in Redox Flow Batteries

“…Two independent works on Fe II/III ‐EDDHA complexes suggested that the reduced complex would be spontaneously oxidized by the ligand . Schroder reported a stable Fe II ‐EDDHA complex after reduction of the Fe III ‐EDDHA complex in aqueous solution . Since a stable ferrous complex is a fundamental condition for use as electroactive species in a RFB, bulk electrolysis was carried out in borate buffer at pH 9.…”

“…At pH values below 5 the redox potential is shifted to more positive values and the system becomes quasi reversible which cannot be explained by the species distribution of the ferric complex calculated from literature data in Figure . The redox potential also depends on the complexation of the ferrous species and information about this system is scarce . In bulk electrolysis experiments it was observed that reduction of the ferric complex leads to a colourless solution which indicates that Fe‐phenolate bonds are absent .…”

“…A CV recorded after reoxidation was congruent with the voltammogram recorded before the bulk electrolysis experiment (Figure ). The stability of the Fe II ‐EDDHA complex found in these experiments is in good agreement with the literature results …”

“…Due to its stereochemical structure, two diastereomeric forms of the Fe‐o,o‐EDDHA complex exist, the racemic and the meso forms (Figure ).The electrochemical behaviour of Fe II/III ‐o,o‐EDDHA as a mixture of its two diastereomers has been studied by voltammetry and cyclic voltammetry (CV) . These results indicated that Fe‐o,o‐EDDHA complexes exhibit a negative redox potential of −560 mV vs (Ag/AgCl, 3 M KCl) at pH 7.4 in a phosphate buffer, however the presence of the two diastereomers of o,o‐EDDHA hindered a detailed analysis.…”