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Brown CJM, Codd R. Directing macrocyclic architecture using iron(III)-, gallium(III)-, or zirconium(IV)-assisted ring closure of linear dimeric endo-hydroxamic acid ligands. J Inorg Biochem 2020; 216:111337. [PMID: 33360106 DOI: 10.1016/j.jinorgbio.2020.111337] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 11/11/2020] [Accepted: 12/04/2020] [Indexed: 11/17/2022]
Abstract
Dimeric hydroxamic acid macrocycles are a subclass of bacterial siderophores produced for iron acquisition. Limited yields from natural sources provides the impetus to develop synthetic routes to improve access to these compounds, which have potential utility in metal ion binding applications in the environment and medicine. This work has examined the role of metal ions in forming pre-complexes with linear endo-hydroxamic acid (endo-HXA) ligands bearing terminal amine and carboxylic acid groups optimally configured for in situ ring closure reactions. The 1:1 reaction between Fe(III) and the dimeric endo-HXA ligand 5-((5-(5-((5-aminopentyl)(hydroxy)amino)-5-oxopentanamido)pentyl)(hydroxy)amino)-5-oxopentanoic acid (PPH-PPH) (1) formed the pre-complex (PC) [Fe(PP-PP)-PC]+ with in situ amide coupling generating the macrocycle (MC) [Fe(PP)2-MC]+ and, following Fe(III) removal, the apo-macrocycle 1,13-dihydroxy-1,7,13,19-tetraazacyclotetracosane-2,6,14,18-tetraone (PPH)2-MC (2). The 1:2 reaction system between Fe(III) and the monomeric endo-HXA ligand 5-((5-aminopentyl)(hydroxy)amino)-5-oxopentanoic acid (PPH) gave significantly less [Fe(PP)2-MC]+ than the former system, due to the requirement to form two rather than one amide bond(s). The 1:1 Ga(III):1 system yielded [Ga(PP-PP)-PC]+ and [Ga(PP)2-MC]+. Neither [Zr(PP-PP)-PC]2+ nor [Zr(PP)2-MC]2+ was detected in the 1:1 Zr(IV):1 system. Instead, the Zr(IV) system showed the formation of a 1:2 Zr(IV):1 pre-complex [Zr(PP-PP)2-PC], which following in situ amide bond forming chemistry, generated two Zr(IV) macrocyclic complexes with distinct architectures: a dimer-of-dimers complex [Zr((PP)2)2-MC] and an end-to-end macrocycle [Zr(PP)4-MC]. The formation of [Fe(PP)2-MC]+, [Ga(PP)2-MC]+ or [Zr((PP)2)2-MC] was confirmed from reconstitution experiments with 2. The work has shown that the choice of metal ion in metal-assisted ring closure reactions directs the assembly of macrocyclic complexes with distinct architectures.
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Affiliation(s)
- Christopher J M Brown
- The University of Sydney, School of Medical Sciences (Pharmacology), New South Wales 2006, Australia
| | - Rachel Codd
- The University of Sydney, School of Medical Sciences (Pharmacology), New South Wales 2006, Australia.
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Codd R, Soe CZ, Pakchung AAH, Sresutharsan A, Brown CJM, Tieu W. The chemical biology and coordination chemistry of putrebactin, avaroferrin, bisucaberin, and alcaligin. J Biol Inorg Chem 2018; 23:969-982. [PMID: 29946977 DOI: 10.1007/s00775-018-1585-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Accepted: 06/20/2018] [Indexed: 12/30/2022]
Abstract
Dihydroxamic acid macrocyclic siderophores comprise four members: putrebactin (putH2), avaroferrin (avaH2), bisucaberin (bisH2), and alcaligin (alcH2). This mini-review collates studies of the chemical biology and coordination chemistry of these macrocycles, with an emphasis on putH2. These Fe(III)-binding macrocycles are produced by selected bacteria to acquire insoluble Fe(III) from the local environment. The macrocycles are optimally pre-configured for Fe(III) binding, as established from the X-ray crystal structure of dinuclear [Fe2(alc)3] at neutral pH. The dimeric macrocycles are biosynthetic products of two endo-hydroxamic acid ligands flanked by one amine group and one carboxylic acid group, which are assembled from 1,4-diaminobutane and/or 1,5-diaminopentane as initial substrates. The biosynthesis of alcH2 includes an additional diamine C-hydroxylation step. Knowledge of putH2 biosynthesis supported the use of precursor-directed biosynthesis to generate unsaturated putH2 analogues by culturing Shewanella putrefaciens in medium supplemented with unsaturated diamine substrates. The X-ray crystal structures of putH2, avaH2 and alcH2 show differences in the relative orientations of the amide and hydroxamic acid functional groups that could prescribe differences in solvation and other biological properties. Functional differences have been borne out in biological studies. Although evolved for Fe(III) acquisition, solution coordination complexes have been characterised between putH2 and oxido-V(IV/V), Mo(VI), or Cr(V). Retrosynthetic analysis of 1:1 complexes of [Fe(put)]+, [Fe(ava)]+, and [Fe(bis)]+ that dominate at pH < 5 led to a forward metal-templated synthesis approach to generate the Fe(III)-loaded macrocycles, with apo-macrocycles furnished upon incubation with EDTA. This mini-review aims to capture the rich chemistry and chemical biology of these seemingly simple compounds.
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Affiliation(s)
- Rachel Codd
- School of Medical Sciences (Pharmacology) and Bosch Institute, The University of Sydney, Sydney, NSW, 2006, Australia.
| | - Cho Zin Soe
- School of Medical Sciences (Pharmacology) and Bosch Institute, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Amalie A H Pakchung
- School of Medical Sciences (Pharmacology) and Bosch Institute, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Athavan Sresutharsan
- School of Medical Sciences (Pharmacology) and Bosch Institute, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Christopher J M Brown
- School of Medical Sciences (Pharmacology) and Bosch Institute, The University of Sydney, Sydney, NSW, 2006, Australia
| | - William Tieu
- School of Medical Sciences (Pharmacology) and Bosch Institute, The University of Sydney, Sydney, NSW, 2006, Australia
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Dubbin WE, Goh TB. Increased Solubility and Bioavailability of Hydroxy-Cr(III) Precipitates in the Presence of Hydroxamate Siderophores. BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2018; 100:409-415. [PMID: 29214326 PMCID: PMC5820410 DOI: 10.1007/s00128-017-2234-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Accepted: 12/02/2017] [Indexed: 06/07/2023]
Abstract
Siderophores are a diverse group of low molecular weight biogenic metallophores with a particular affinity for Fe(III) but they also have potential to complex a number of other polyvalent metal cations, including Cr(III). Here we show that two hydroxamate siderophores, desferrioxamine B and rhodotorulic acid, at environmentally relevant concentrations, facilitate the dissolution of hydroxy-Cr(III) precipitates from a common layer silicate. Desferrioxamine B and rhodotorulic acid induced maximum initial Cr dissolution rates of 11.3 ± 1.7 × 10- 4 and 9.03 ± 0.68 × 10- 4 µmol m- 2 h- 1, respectively, yielding maximum solution Cr concentrations of 0.26 ± 0.01 and 0.20 ± 0.02 µmol m- 2, respectively. These data demonstrate that hydroxamate siderophores may play an important role increasing the dispersal of Cr in natural environments, thus facilitating greater bioavailability of this potential toxin.
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Affiliation(s)
- William E Dubbin
- Department of Earth Science, The Natural History Museum, London, SW7 5BD, UK.
| | - Tee Boon Goh
- Department of Soil Science, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada
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Kurth C, Kage H, Nett M. Siderophores as molecular tools in medical and environmental applications. Org Biomol Chem 2016; 14:8212-27. [PMID: 27492756 DOI: 10.1039/c6ob01400c] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Almost all life forms depend on iron as an essential micronutrient that is needed for electron transport and metabolic processes. Siderophores are low-molecular-weight iron chelators that safeguard the supply of this important metal to bacteria, fungi and graminaceous plants. Although animals and the majority of plants do not utilise siderophores and have alternative means of iron acquisition, siderophores have found important clinical and agricultural applications. In this review, we will highlight the different uses of these iron-chelating molecules.
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Affiliation(s)
- Colette Kurth
- Leibniz Institute for Natural Product Research and Infection Biology, Hans-Knöll-Institute, Adolf-Reichwein-Str. 23, D-07745 Jena, Germany
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Magnetic susceptibility of Mn(III) complexes of hydroxamate siderophores. J Inorg Biochem 2015; 148:22-6. [PMID: 25978931 DOI: 10.1016/j.jinorgbio.2015.04.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 04/23/2015] [Accepted: 04/24/2015] [Indexed: 11/23/2022]
Abstract
The hydroxamate siderophores putrebactin, desferrioxamine B, and desferrioxamine E bind Mn(II) and promote the air oxidation of Mn(II) to Mn(III) at pH>7.1. The magnetic susceptibility of the manganese complexes were determined by the Evans method and the stoichiometry was probed with electrospray ionization mass spectrometry (ESIMS). The room temperature magnetic moments (μeff) for the manganese complexes of desferrioxamines B and E were 4.85 BM and 4.84 BM, respectively, consistent with a high spin, d(4), Mn(III) electronic configuration. The manganese complex of putrebactin had a magnetic moment of 4.98 BM, consistent with incomplete oxidation of Mn(II), as confirmed by X band EPR spectroscopy. Mass spectra of the Mn(III) desferrioxamine B and E complexes showed complexes at m/z 613.26 and 653.26, respectively, consistent with 1:1 complexation. Mass spectral peaks for manganese putrebactin at m/z 797.31 and 1221.41 corresponds to 1:2 and 2:3 Mn:putrebactin complexation. This study directly confirms the Mn(III) oxidation state in hydroxamate siderophore complexes.
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Aziz SG, Elroby SA, Hilal RH, Osman OI. Theoretical and computational studies of conformation, natural bond orbital and nonlinear optical properties of cis-N-phenylbenzohydroxamic acid. COMPUT THEOR CHEM 2014. [DOI: 10.1016/j.comptc.2013.12.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Pakchung AAH, Soe CZ, Lifa T, Codd R. Complexes formed in solution between vanadium(IV)/(V) and the cyclic dihydroxamic acid putrebactin or linear suberodihydroxamic acid. Inorg Chem 2011; 50:5978-89. [PMID: 21627146 PMCID: PMC3124108 DOI: 10.1021/ic1025119] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Indexed: 01/25/2023]
Abstract
An aerobic solution prepared from V(IV) and the cyclic dihydroxamic acid putrebactin (pbH(2)) in 1:1 H(2)O/CH(3)OH at pH = 2 turned from blue to orange and gave a signal in the positive ion electrospray ionization mass spectrometry (ESI-MS) at m/z(obs) 437.0 attributed to the monooxoV(V) species [V(V)O(pb)](+) ([C(16)H(26)N(4)O(7)V](+), m/z(calc) 437.3). A solution prepared as above gave a signal in the (51)V NMR spectrum at δ(V )= -443.3 ppm (VOCl(3), δ(V) = 0 ppm) and was electron paramagnetic resonance silent, consistent with the presence of [V(V)O(pb)](+). The formation of [V(V)O(pb)](+) was invariant of [V(IV)]:[pbH(2)] and of pH values over pH = 2-7. In contrast, an aerobic solution prepared from V(IV) and the linear dihydroxamic acid suberodihydroxamic acid (sbhaH(4)) in 1:1 H(2)O/CH(3)OH at pH values of 2, 5, or 7 gave multiple signals in the positive and negative ion ESI-MS, which were assigned to monomeric or dimeric V(V)- or V(IV)-sbhaH(4) complexes or mixed-valence V(V)/(IV)-sbhaH(4) complexes. The complexity of the V-sbhaH(4) system has been attributed to dimerization (2[V(V)O(sbhaH(2))](+) ↔ [(V(V)O)(2)(sbhaH(2))(2)](2+)), deprotonation ([V(V)O(sbhaH(2))](+) - H(+) ↔ [V(V)O(sbhaH)](0)), and oxidation ([V(IV)O(sbhaH(2))](0) -e(-) ↔ [V(V)O(sbhaH(2))](+)) phenomena and could be described as the sum of two pH-dependent vectors, the first comprising the deprotonation of hydroxamate (low pH) to hydroximate (high pH) and the second comprising the oxidation of V(IV) (low pH) to V(V) (high pH). Macrocyclic pbH(2) was preorganized to form [V(V)O(pb)](+), which would provide an entropy-based increase in its thermodynamic stability compared to V(V)-sbhaH(4) complexes. The half-wave potentials from solutions of [V(IV)]:[pbH(2)] (1:1) or [V(IV)]:[sbhaH(4)] (1:2) at pH = 2 were E(1/2) -335 or -352 mV, respectively, which differed from the expected trend (E(1/2) [VO(pb)](+/0) < V(V/IV)-sbhaH(4)). The complex solution speciation of the V(V)/(IV)-sbhaH(4) system prevented the determination of half-wave potentials for single species. The characterization of [V(V)O(pb)](+) expands the small family of documented V-siderophore complexes relevant to understanding V transport and assimilation in the biosphere.
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Affiliation(s)
- Amalie A. H. Pakchung
- Center for Heavy Metals Research, School of Chemistry and School of Medical Sciences (Pharmacology) and Bosch Institute, University of Sydney, New South Wales 2006, Australia
| | - Cho Zin Soe
- Center for Heavy Metals Research, School of Chemistry and School of Medical Sciences (Pharmacology) and Bosch Institute, University of Sydney, New South Wales 2006, Australia
| | - Tulip Lifa
- Center for Heavy Metals Research, School of Chemistry and School of Medical Sciences (Pharmacology) and Bosch Institute, University of Sydney, New South Wales 2006, Australia
| | - Rachel Codd
- Center for Heavy Metals Research, School of Chemistry and School of Medical Sciences (Pharmacology) and Bosch Institute, University of Sydney, New South Wales 2006, Australia
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Crumbliss AL, Harrington JM. Iron sequestration by small molecules: Thermodynamic and kinetic studies of natural siderophores and synthetic model compounds. ADVANCES IN INORGANIC CHEMISTRY 2009. [DOI: 10.1016/s0898-8838(09)00204-9] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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Tomisić V, Blanc S, Elhabiri M, Expert D, Albrecht-Gary AM. Iron(III) uptake and release by chrysobactin, a siderophore of the phytophatogenic bacterium Erwinia chrysanthemi. Inorg Chem 2008; 47:9419-30. [PMID: 18803373 DOI: 10.1021/ic801143e] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The plant pathogenic enterobacterium Erwinia chrysanthemi causes important soft-rot disease on a wide range of plants including vegetables and ornamentals of economic importance. It produces a major mono(catecholate) siderophore, chrysobactin (alpha-N-(2,3-dihydroxybenzoyl)-D-lysyl-L-serine). To unravel the role of chrysobactin in the virulence of E. chrysanthemi, its iron(III) coordination properties were thus investigated in aqueous solutions using electrospray ionization mass spectrometric, potentiometric, and spectrophotometric methods. Moreover, kinetic experiments allowed us to determine the uptake and release mechanisms. The formation mechanism of the 1:1 complex reveals a key role of the terminal carboxylic group of chrysobactin in the binding of either FeOH(2+) or Fe2(OH)2(4+). The proton-driven dissociation of the ferric tris-, bis-, and mono(chrysobactin) complexes was also studied. For these three ferric complexes, a single protonation triggers the release of the bound chrysobactin molecule. Interestingly, the dissociation of the last ligand proceeded via the formation of an intermediate for which a salicylate-type mode of bonding was proposed.
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Affiliation(s)
- Vladislav Tomisić
- Laboratoire de Physico-Chimie Bioinorganique, ULP-CNRS (UMR 7177), Institut de Chimie, ECPM, 25 rue Becquerel, 67200 Strasbourg, France
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Upritchard HG, Yang J, Bremer PJ, Lamont IL, McQuillan AJ. Adsorption to metal oxides of the Pseudomonas aeruginosa siderophore pyoverdine and implications for bacterial biofilm formation on metals. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:7189-95. [PMID: 17530790 DOI: 10.1021/la7004024] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The initiation of biofilm formation is poorly understood, and in particular, the contribution of chemical bond formation between bacterial cells and metal surfaces has received little attention. We have previously used in situ infrared spectroscopy to show, during the initial stages of Pseudomonas aeruginosa biofilm formation, the formation of coordinate covalent bonds between titanium dioxide particle films and pyoverdine, a mixed catecholate and hydroxamate siderophore. Here we show using infrared spectroscopy that pyoverdine can also form covalent bonds with particle films of Fe2O3, CrOOH, and AlOOH. Adsorption to the metal oxides through the catechol-like 2,3-diamino-6,7-dihydroxyquinoline part of pyoverdine was most evident in the infrared spectrum of the adsorbed pyoverdine molecule. Weaker infrared absorption bands that are consistent with the hydroxamic acids of pyoverdine binding covalently to TiO2, Fe2O3, and AlOOH surfaces were also observed. The adsorption of pyoverdine to TiO2 and Fe2O3 surfaces showed a pH dependence that is indicative of the dominance of the catechol-like ligand of pyoverdine. Infrared absorption bands were also evident for pyoverdine associated with the cells of P. aeruginosa on TiO2 and Fe2O3 surfaces and were notably absent for genetically modified cells unable to synthesize or bind pyoverdine at the cell surface. These studies confirm the generality of pyoverdine-metal bond formation and suggest a wider involvement of siderophores in bacterial biofilm initiation on metals.
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Affiliation(s)
- Hamish G Upritchard
- Departments of Biochemistry, Chemistry, and Food Science, University of Otago, Dunedin, New Zealand
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Brickman TJ, Anderson MT, Armstrong SK. Bordetella iron transport and virulence. Biometals 2007; 20:303-22. [PMID: 17295050 DOI: 10.1007/s10534-006-9031-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2006] [Accepted: 07/20/2006] [Indexed: 11/26/2022]
Abstract
Bordetella pertussis, Bordetella parapertussis, and Bordetella bronchiseptica are pathogens with a complex iron starvation stress response important for adaptation to nutrient limitation and flux in the mammalian host environment. The iron starvation stress response is globally regulated by the Fur repressor using ferrous iron as the co-repressor. Expression of iron transport system genes of Bordetella is coordinated by priority regulation mechanisms that involve iron source sensing. Iron source sensing is mediated by distinct transcriptional activators that are responsive to the cognate iron source acting as the inducer.
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Affiliation(s)
- Timothy J Brickman
- Department of Microbiology, University of Minnesota Medical School, MMC 196, 420 Delaware Street S.E., Minneapolis, MN 55455-0312, USA
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Nayak S, Dash AC, Nayak PK, Das D. Kinetics and Mechanism of the Formation of (1,5)bis(2-hydroxybenzamido)3- azapentaneiron(III) and its Reactions with Thiocyanate, Azide, Acetate, Sulfur(IV) and Ascorbic Acid in Solution, and the Synthesis and Characterization of (nitrato)bis- (2-hydroxybenzamido)3-azapentaneiron(III). The Role of Phenol–amide–amine Coordination. TRANSIT METAL CHEM 2005. [DOI: 10.1007/s11243-005-5627-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Brickman TJ, Armstrong SK. Bordetella AlcS transporter functions in alcaligin siderophore export and is central to inducer sensing in positive regulation of alcaligin system gene expression. J Bacteriol 2005; 187:3650-61. [PMID: 15901687 PMCID: PMC1112062 DOI: 10.1128/jb.187.11.3650-3661.2005] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bordetella pertussis and Bordetella bronchiseptica, which are respiratory mucosal pathogens of mammals, produce and utilize the siderophore alcaligin to acquire iron in response to iron starvation. A predicted permease of the major facilitator superfamily class of membrane efflux pumps, AlcS (synonyms, OrfX and Bcr), was reported to be encoded within the alcaligin gene cluster. In this study, alcS null mutants were found to be defective in growth under iron starvation conditions, in iron source utilization, and in alcaligin export. trans complementation using cloned alcS genes of B. pertussis or B. bronchiseptica restored the wild-type phenotype to the alcS mutants. Although the levels of extracellular alcaligin measured in alcS strain culture fluids were severely reduced compared with the wild-type levels, alcS mutants had elevated levels of cell-associated alcaligin, implicating AlcS in alcaligin export. Interestingly, a deltaalcA mutation that eliminated alcaligin production suppressed the growth defects of alcS mutants. This suppression and the alcaligin production defect were reversed by trans complementation of the deltaalcA mutation in the double-mutant strain, confirming that the growth-defective phenotype of alcS mutants is associated with alcaligin production. In an alcA::mini-Tn5 lacZ1 operon fusion strain background, an alcS null mutation resulted in enhanced AlcR-dependent transcriptional responsiveness to alcaligin inducer; conversely, AlcS overproduction blunted the transcriptional response to alcaligin. These transcription studies indicate that the alcaligin exporter activity of AlcS is required to maintain appropriate intracellular alcaligin levels for normal inducer sensing and responsiveness necessary for positive regulation of alcaligin system gene expression.
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Affiliation(s)
- Timothy J Brickman
- Department of Microbiology, University of Minnesota, MMC 196, 420 Delaware Street S.E., Minneapolis, Minnesota 55455-0312, USA
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Serratrice G, Biaso F, Thomas F, Béguin C. Mechanism of the Stepwise Dissociation of FeIII Complexes with Tripodal Ligands as Siderophore Models. Eur J Inorg Chem 2004. [DOI: 10.1002/ejic.200300396] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Wirgau JI, Crumbliss AL. Carrier-facilitated bulk liquid membrane transport of iron(iii) hydroxamate complexes utilizing a labile recognition agent and amine recognition in the second coordination sphere. Dalton Trans 2003. [DOI: 10.1039/b306810b] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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16
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BURGESS JOHN, HUBBARD COLIND. LIGAND SUBSTITUTION REACTIONS. ADVANCES IN INORGANIC CHEMISTRY 2003. [DOI: 10.1016/s0898-8838(03)54002-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Boukhalfa H, Crumbliss AL. Kinetics and mechanism of a catalytic chloride ion effect on the dissociation of model siderophore hydroxamate-iron(III) complexes. Inorg Chem 2001; 40:4183-90. [PMID: 11487321 DOI: 10.1021/ic010050k] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Proton-driven ligand dissociation kinetics in the presence of chloride, bromide, and nitrate ions have been investigated for model siderophore complexes of Fe(III) with the mono- and dihydroxamic acid ligands R(1)C(=O)N(OH)R(2) (R(1) = CH(3), R(2) = H; R(1) = CH(3), R(2) = CH(3); R(1) = C(6)H(5), R(2) = H; R(1) = C(6)H(5), R(2) = C(6)H(5)) and CH(3)N(OH)C(=O)[CH(2)](n)C(=O)N(OH)CH(3) (H(2)L(n); n = 2, 4, 6). Significant rate acceleration in the presence of chloride ion is observed for ligand dissociation from the bis(hydroxamate)- and mono(hydroxamate)-bound complexes. Rate acceleration was also observed in the presence of bromide and nitrate ions but to a lesser extent. A mechanism for chloride ion catalysis of ligand dissociation is proposed which involves chloride ion dependent parallel paths with transient Cl(-) coordination to Fe(III). The labilizing effect of Cl(-) results in an increase in microscopic rate constants on the order of 10(2)-10(3). Second-order rate constants for the proton driven dissociation of dinuclear Fe(III) complexes formed with H(2)L(n)() were found to vary with Fe-Fe distance. An analysis of these data permits us to propose a reactive intermediate of the structure (H(2)O)(4)Fe(L(n)())Fe(HL(n))(Cl)(OH(2))(2+) for the chloride ion dependent ligand dissociation path. Environmental and biological implications of chloride ion enhancement of Fe(III)-ligand dissociation reactions are presented.
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Affiliation(s)
- H Boukhalfa
- Department of Chemistry, Duke University, Box 90346, Durham, North Carolina 27708-0346, USA
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