Mechanistic Studies on the Dissociation of Mono- and Bimetallic 1:1 Ferric Dihydroxamate Complexes: Probing Structural Effects in Siderophore Dissociation Reactions

Caudle, M. Tyler; Goswelll., P.; Crumbliss, Alvin L.

doi:10.1021/ic00099a029

Cited by 24 publications

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“…Such a relationship has been observed for the dissociation of a large series of Fe III ‐mono(hydroxamato) complexes yielding a slope of 0.9(1) in agreement with the theoretical value of 1, and an intercept ln K 1 = −0.6 (p K At = −0.26) 7. The correlation shows also that the transition state acidity of Fe III ( L 1 or L 2 or L 3 or L 5 ) is lower than that of Fe III (hydroxamic acid), i.e.…”

Section: Discussionsupporting

confidence: 82%

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Mechanism of the Stepwise Dissociation of Fe^III Complexes with Tripodal Ligands as Siderophore Models

et al. 2004

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The acid hydrolysis and formation kinetics of 1:1 ferric complexes with several tripodal hexadentate ligands were investigated over the [H + ] range of 0.02−1.0 M at 25°C and at an ionic strength of 2.0 M (NaClO 4 /HClO 4 ). These ligands are based on a tris(2-aminoethyl)amine (TREN) spacer connected through a tris(amide) moiety to identical pendant bidentate chelating group arms such as catecholate (TREN-CAMS,Mixed ligands with chelating arms such as catecholate and 8-hydroxyquinolinate (TRENSOX2CAMS, L 1 and TRENSOXCAMS2, L 2 ) were also investigated. An analogue of L 0 (C-SOX, L 4 ) with a C-pivot scaffold instead of TREN was studied for comparison. The acid hydrolysis reaction was found to proceed in four kinetically distinguishable stages. A common mechanism in the series was followed when the ligand structure was varied. The first stage is very fast and can be attributed to the dissociation of one arm of the tripodal ligand. The second and third stages involve protonation of the complex which in-

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Section: Discussionsupporting

confidence: 82%

“…The most studied, hexadentate desferrioxamine B (DFB, desferal), has three bidentate hydroxamate groups 8,9. Fe III complexes of dihydroxamate siderophores and siderophore models have been also investigated7,10,11 but there are a few kinetic data available for the dechelation processes of complexes with other types of ligands.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of the Stepwise Dissociation of Fe^III Complexes with Tripodal Ligands as Siderophore Models

et al. 2004

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“…Maybe even additional parallel pathways are operative, similar to those postulated for iron(III) dihydroxamate complexes. 26 After 4.5 h the dissociation is essentially complete and the final proton NMR spectrum is almost identical that of 3 at the same temperature. The reaction is not reversible on cooling, probably due to the rigidity of the ligand.…”

Section: Proton Nmr Spectroscopymentioning

confidence: 75%

Synthesis, characterisation, and solution behaviour of two dioxomolybdenum(VI) complexes of a bis(catecholamide) siderophore analogue

Duhme¹

1997

J. Chem. Soc., Dalton Trans.

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The bis(catecholamide) α,αЈ-bis(2,3-dihydroxybenzoylamino)-m-xylene (H 4 L 3 ) has been synthesized and characterised. It is an analogue of the naturally occurring siderophore azotochelin and structurally related to an approved enterobactin model. Two dioxomolybdenum() complexes of it have been synthesized, namely a di-and a mono-nuclear one. Variable-temperature proton NMR studies of the initially obtained dinuclear compound revealed that three kinetic processes are operative in Me 2 SO solution: geometrical isomerisation at lower temperatures, and inversion of configuration concomitant with dissociation into the monomer at higher temperatures. In contrast, the mononuclear complex obtained in this way isomerises and inverts almost simultaneously at 343-353 K. The crystal structure of Na 2 [MoO 2 L 3 ] confirmed the mononuclear nature of the complex and revealed that the cis, cis, cis geometrical isomer is adopted in the solid state.

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“…This is also shown in the CV voltammograms of the complexes: the anodic peak to the cathodic peak ratio is very close to 1 in the copper(II) and zinc(II) complexes, but much smaller in the iron(II) and nickel(II) complexes. Earlier studies suggested that dihydroxamic acid ligands, in general, exhibit a greater tendency to form dimeric species in solution [15,19,20]. However, the coordination modes of dihydroxamate ions were not discussed in the solid state and in one case an iron(III)-trihydroxamate complex was reported to be polynuclear [21].…”

Section: Electrochemical Behaviormentioning

confidence: 99%

Transition metal complexes of acetamidomalondihydroxamate: synthesis, spectral, thermal and electrochemical studies

Yılmaz

Topçu

2004

Journal of Coordination Chemistry

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Acetamidomalondihydroxamate (K 2 AcAMDH) and its manganese(II), iron(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes were synthesized and characterized by elemental analysis, UV-VIS, IR and magnetic susceptibility. The pK a1 and pK a2 values of the dihydroxamic acid in aqueous solution were found to be 8.0 AE 0.1 and 9.7 AE 0.1. The dihydroxamate anion AcAMDH behaves as a tetradentate bridging ligand through both hydroxamate groups, forming complexes with a metal to ligand ratio of 1 : 1 in the solid state. The FTIR spectra and thermal decompositions of the ligand and its metal complexes were recorded. The redox behavior of the complexes was investigated in aqueous solution by square wave voltammetry and cyclic voltammetry at neutral pH. In contrast to the solid state, in solution the copper(II) and zinc(II) ions form stable complex species with a metal to ligand ratio of 1 : 2. The iron(II) and nickel(II) complexes show a two-electron irreversible reduction behavior, while the copper(II) and zinc(II) complexes undergo reversible electrode reactions. The stability constants of the complexes were determined by square wave voltammetry.

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Mechanistic Studies on the Dissociation of Mono- and Bimetallic 1:1 Ferric Dihydroxamate Complexes: Probing Structural Effects in Siderophore Dissociation Reactions

Cited by 24 publications

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Mechanism of the Stepwise Dissociation of Fe^III Complexes with Tripodal Ligands as Siderophore Models

Mechanism of the Stepwise Dissociation of Fe^III Complexes with Tripodal Ligands as Siderophore Models

Synthesis, characterisation, and solution behaviour of two dioxomolybdenum(VI) complexes of a bis(catecholamide) siderophore analogue

Transition metal complexes of acetamidomalondihydroxamate: synthesis, spectral, thermal and electrochemical studies

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Mechanistic Studies on the Dissociation of Mono- and Bimetallic 1:1 Ferric Dihydroxamate Complexes: Probing Structural Effects in Siderophore Dissociation Reactions

Cited by 24 publications

References 0 publications

Mechanism of the Stepwise Dissociation of FeIII Complexes with Tripodal Ligands as Siderophore Models

Mechanism of the Stepwise Dissociation of FeIII Complexes with Tripodal Ligands as Siderophore Models

Synthesis, characterisation, and solution behaviour of two dioxomolybdenum(VI) complexes of a bis(catecholamide) siderophore analogue

Transition metal complexes of acetamidomalondihydroxamate: synthesis, spectral, thermal and electrochemical studies

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Mechanism of the Stepwise Dissociation of Fe^III Complexes with Tripodal Ligands as Siderophore Models

Mechanism of the Stepwise Dissociation of Fe^III Complexes with Tripodal Ligands as Siderophore Models