Iron(III) Complexation by New Aminocarboxylate Chelators − Thermodynamic and Kinetic Studies

Abstract

The complexation of FeIII by new tetradentate and pentadentate aminocarboxylate chelators, designed to protect cells against iron‐catalysed oxidative damage, was investigated. Ferric iron complexes of N,N′‐bis(3,4,5‐trimethoxybenzyl)ethylenediamine‐N,N′‐diacetic acid (L1), N,N′‐dibenzylethylenediamine‐N,N′‐diacetic acid (L2) and [N‐(2‐hydroxybenzyl)‐N′‐benzylethylenediamine‐N,N′‐diacetic acid] (L3) have been characterized in aqueous solution by potentiometric, UV/Vis spectrophotometric and cyclic voltammetric measurements. The parent ligand, ethylenediamine‐N,N′‐diacetic acid (L4), has also been studied. As expected, the presence of a hard phenolate donor group in L3 significantly enhances the affinity for iron while decreasing the potential of the FeIII/FeII redox couple compared to L1 or L2. Kinetics studies have provided the kinetic rate constants related to the formation and the dissociation of the ferric complex with L3. The results reveal a fast FeIII uptake, which is a favorable feature for a biological use of this type of ligand. Overall, these results demonstrate the pertinence of the use of such ligands to protect biological tissues against oxidative stress.

Minding metals: Tailoring multifunctional chelating agents for neurodegenerative disease

“…H 2 O 2 and a reductant, metal complexes like 14 are hydroxylated and their iron affinity increases. In addition to an increase in affinity, another consequence of the added phenolate donor is a decrease in Fe 3+ /Fe 2+ redox potential that prevents further redox cycling of iron 55. The early compounds were not efficient at protecting cells from oxidative stress, probably because they were unable to cross cell membranes.…”

Adsorption of alpha amino acids at the water/goethite interface

“…A prerequisite is that the speciation in the aqueous Fe(III)-ligand system is thoroughly characterized in order to establish reliable IR spectra-structure relationships. The Fe(III)MIDA [30] and Fe(III)EDDA [31] systems have been previously studied, and the stability constants determined were used to generate the distribution diagrams displayed in Fig. 4.…”

“…The stability constants used to generate the MIDA diagram are from Sanchiz et al[30] and the EDDA diagram from Serratrice et al[31].…”

Design of Iron chelators: Syntheses and iron (III) complexing abilities of tripodal tris-bidentate ligands

“…Lipophilic enterobactin analogues (tris-catecholates) have been described ) using a spermidine spacer in which the N terminal nitrogen atom is substituted by long alkyl chains. Lipophilic chelators derived from EDTA (Galey et al 2000;Serratrice et al 2001) or trisaminophenol (Bollinger et al 1995) have also been reported. An elegant strategy has been developed by Shanzer and collaborators in which the lipophilic ferrichrome analogues with masked hydrophilic moieties (Figure 8a) A series of three tris-hydroxyquinolinate derivatives of O-TRENSOX containing a C-pivotal atom as spacer and grafted with various polyoxyethylene chains (POE) has been prepared in our group (Figure 9a, Imbert et al 2002), leading to the observation that the hydrophilic-lipophilic balance (quantified by the partition coefficients) of the overall neutral ferric complexes is tuned by the length of the polyoxyethylene chain.…”