ChemInform Abstract: THE REACTIVITY OF DIFFERENT IRON(III) SPECIES IN THE FORMAION OF MONOACETOHYDROXAMATOIRON(III)

Biruš, Mladen; Kujundžić, Nikola; Pribanic, Marijan

doi:10.1002/chin.198121302

Cited by 12 publications

(22 citation statements)

References 1 publication

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“…Therefore, the Fe-N pyr bond cleavage rates from analysis of stage 1 (too fast to be measured), stage 2 (k 2 ), and stage 3 (k 3 ) are decreased from the complex with three Fe-N pyr bonds to the complex with no Fe-N pyr bond as observed in a dissociation mechanism. 56 The last step of the mechanism has been tentatively assigned to the formation of coordination with two carbonyl oxygen atoms on the basis of the UV-visible spectra. We were able to determine the rate constant (k 4 ) 0.26 s -1 ) corresponding to the first carbonyl oxygen coordination.…”

Section: Discussionmentioning

confidence: 99%

O-TRENSOX, a New Tripodal Iron Chelator Based on 8-Hydroxyquinoline Subunits: Thermodynamic and Kinetic Studies

et al. 1997

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The thermodynamic stability of Fe(III) complexes with a new hexadentate tripodal ligand (O-TRENSOX) incorporating three 8-hydroxyquinoline ("oxine") subunits, linked to a tetraamine ("TREN") via an amide connection, has been investigated by the use of UV-vis spectrophotometry and potentiometric methods. O-TRENSOX has been found to form, at pH < 1, a protonated complex FeLH 5 2+ (orange color) which deprotonates, over the pH range 1-2, to a green complex FeLH 2through a four-proton process. The first protonation constant of ferric O-TRENSOX has been determined to be 5.60. The stability constant log β 110 has been determined to be 30.9. A pFe (pFe ) -log [Fe 3+ ]) value of 29.5 has been calculated at pH ) 7.4, [ligand] tot ) 10 µΜ, and [Fe 3+ ] tot ) 1 µM, indicating that O-TRENSOX is one of the most powerful among the iron synthetic chelators. Cyclic voltammetry experiments have shown that the system Fe III -O-TRENSOX/Fe II -O-TRENSOX is quasi reversible, with a redox potential of 0.087 V vs NHE. This value is related to the high complexing ability of O-TRENSOX for both the ferric and ferrous iron redox states, making it relevant for biological uses. The kinetics of formation and acid hydrolysis of the ferric O-TRENSOX complex have been investigated in acidic medium using the diode array stopped-flow spectrophotometry technique in 2.0 M NaClO 4 /HClO 4 at 25 °C. The determining step for the complex formation involves the reaction of FeOH 2+ with the LH 7 + ligand species, with a rate constant of 789 ( 17 M -1 s -1 . The acid hydrolysis of the FeLH 2complex in 0.02-1.0 M HClO 4 and ionic strength 2.0 M NaClO 4 /HClO 4 leads to the FeLH 5 2+ complex, indicating that O-TRENSOX is a very strong chelating agent for Fe(III) in acidic medium. The kinetic data have been interpreted by a stepwise mechanism related to the successive protonation of four binding sites. The spectroscopic change is consistent with removal of one arm of the ligand followed by a shift from a bis(oxinate) to a bis(salicylate) mode of coordination.

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Section: Discussionmentioning

confidence: 99%

O-TRENSOX, a New Tripodal Iron Chelator Based on 8-Hydroxyquinoline Subunits: Thermodynamic and Kinetic Studies

et al. 1997

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“…The protolytic (K H ) equilibrium for the iron(III) species (Fe 3+ and Fe(OH) 2+ ) 46 can be considered as a fast step (eqn ( 6)). 54 The following mechanism (eqn ( 7)-(10)) can be thus suggested: This mechanism leads to the following rate equation:…”

Section: Complexation Of Iron(iii) By Pyochelinmentioning

confidence: 99%

Pyochelin, a siderophore of Pseudomonas aeruginosa: Physicochemical characterization of the iron(iii), copper(ii) and zinc(ii) complexes

et al. 2012

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Pseudomonas aeruginosa is an opportunistic pathogen, synthesizing two major siderophores, pyoverdine (Pvd) and pyochelin (Pch), to cover its needs in iron(III). If the high affinity and specificity of Pvd toward iron(III) (pFe = 27.0) was well described in the literature, the physicochemical and coordination properties of Pch toward biologically relevant metals (Fe(III), Cu(II) or Zn(II)) have been only scarcely investigated. We report a thorough physico-chemical investigation of Pch (potentiometry, spectrophotometries, ESI/MS) that highlighted its moderate but significantly higher affinity for Fe(3+) (pFe = 16.0 at p[H] 7.4) than reported previously. We also demonstrated that Pch strongly chelates divalent metals such as Zn(II) (pZn = 11.8 at p[H] 7.4) and Cu(II) (pCu = 14.9 at p[H] 7.4) and forms predominantly 1 : 2 (M(2+)/Pch) complexes. Kinetic studies revealed that the formation of the ferric Pch complexes proceeds through a Eigen-Wilkins dissociative ligand interchange mechanism involving two protonated species of Pch and the Fe(OH)(2+) species of Fe(III). Our physico-chemical parameters supports the previous biochemical studies which proposed that siderophores are not only devoted to iron(III) shuttling but most likely display other specific biological role in the subtle metals homeostasis in microorganisms. This work also represents a step toward deciphering the role of siderophores throughout evolution.

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“…[18] So, if we assume a value of about 10  Ϫ1 s Ϫ1 for k 4 , it seems reasonable to neglect the k 4 K a4 K a5 term with respect to k 3 K Fe K a5 . Thus, we can obtain k 3 ϭ 770 Ϯ 180  Ϫ1 s Ϫ1 .…”

Section: Formation and Acid Hydrolysis Kinetics Of The Fel3 Complexmentioning

confidence: 99%

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

Serratrice

Galey

Aman

et al. 2001

Eur. J. Inorg. Chem.

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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.

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ChemInform Abstract: THE REACTIVITY OF DIFFERENT IRON(III) SPECIES IN THE FORMAION OF MONOACETOHYDROXAMATOIRON(III)

Abstract: Die Abhängigkeit der Geschwindigkeitskonstanten der Bildung des Titelkomplexes von der Ionenstärke in saurer Lösung wurde bei 25°C untersucht.

Cited by 12 publications

References 1 publication

O-TRENSOX, a New Tripodal Iron Chelator Based on 8-Hydroxyquinoline Subunits: Thermodynamic and Kinetic Studies

O-TRENSOX, a New Tripodal Iron Chelator Based on 8-Hydroxyquinoline Subunits: Thermodynamic and Kinetic Studies

Pyochelin, a siderophore of Pseudomonas aeruginosa: Physicochemical characterization of the iron(iii), copper(ii) and zinc(ii) complexes

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

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