Influence of the polyamino carboxylate chelating ligand (L) on the kinetics and mechanism of the formation of FeII(L)NO in the system FeII(L)/NO/HONO/NO2- in aqueous solution

Zang, V.; Eldik, R. Van

doi:10.1021/ic00347a026

Cited by 79 publications

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“…For both oxidants, the oxidation of Fe(II)DTPA was an order of magnitude slower than that of Fe(II)EDTA, despite the similar nature of these ligands, which is consistent with previous results (Graf et al, 1984). The absence of a readily-exchangeable bound water molecule in the Fe(II)DTPA complex (Zang and Van Eldik, 1990a) could explain the much slower oxidation kinetics observed for this complex if oxidation of Fe(II)L (L = EDTA, DTPA) by O 2 and H 2 O 2 was an inner sphere process; in this case, with the initial binding of the oxidant to Fe(II)L being the rate-limiting step, exchange of a bound H 2 O molecule for an oxidant molecule should presumably proceed at a much greater rate and with less steric hindrance than would be observed when oxidant binding first requires breaking of an Fe(II)-chelate bond (Graf et al, 1984). Summers et al (2008) have demonstrated the importance of the water-loss rate to the related superoxide-mediated reduction of Fe(III)EDTA and Fe(III)DTPA.…”

Section: Verified As Discussed In Textmentioning

confidence: 99%

Importance of Iron Complexation for Fenton-Mediated Hydroxyl Radical Production at Circumneutral pH

2016

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The reaction between Fe(II) and H 2 O 2 to yield hydroxyl radicals (HO • ), the Fenton reaction, is of interest due to its role in trace metal and natural organic matter biogeochemistry, its utility in water treatment and its role in oxidative cell degradation and associated human disease. There is significant dispute over whether HO • , the most reactive of the so-called reactive oxygen species (ROS), is formed in this reaction, particularly under circumneutral conditions relevant to natural systems. In this work we have studied the oxidation kinetics of Fe(II) complexed by L = citrate, ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) and also measured HO • production using phthalhydrazide as a probe compound at pH 8.2. A kinetic model has been developed and utilized to confirm that HO • is the sole product of the Fe(II)L-H 2 O 2 reaction for L = EDTA and DTPA. Quantitative HO • production also appears likely for L = citrate, although uncertainties with the speciation of Fe(II)-citrate complexes as well as difficulties in modeling the oxidation kinetics of these complexes has prevented a definitive conclusion. In the absence of ligands at circumneutral pH, inorganic Fe(II) reacts with H 2 O 2 to yield a species other than HO • , contrary to the well-established production of HO • from inorganic Fe(II) at low pH. Our results suggest that at high pH Fe(II) must be complexed for HO • production to occur.

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Section: Verified As Discussed In Textmentioning

confidence: 99%

Importance of Iron Complexation for Fenton-Mediated Hydroxyl Radical Production at Circumneutral pH

2016

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“…2 and 1, respectively, with the latter being favored at low and room temperature. When no additional nucleophile is present, two mononuclear complexes (2) fold together to form the dinuclear complex (1). In order to bind the nucleophile, the bridge unfolds and allows a relatively open access to the active site.…”

Section: Kinetic Studies Of the Binding Of No To [Fe(s 4 Net 2 N)] Frmentioning

confidence: 99%

“…In order to bind the nucleophile, the bridge unfolds and allows a relatively open access to the active site. Evidence for the dinuclear species in solution comes from its very low solubility as well as the mass spectrum which shows a molecular ion peak at m/z = 1024 that corresponds to the dinuclear species (1). NO binding to the dinuclear complex [Fe II (S 4 NNEt 2 )] 2 was kinetically investigated and occurs according to the overall reaction (1).…”

Section: Kinetic Studies Of the Binding Of No To [Fe(s 4 Net 2 N)] Frmentioning

confidence: 99%

“…More recently this interest is focused on nitrosyl complexes as potential waste gas purification catalysts, [1] as drugs releasing the neuro-transmitter and mammalian bioregulator NO, [2] or as model complexes for metal enzymes such as nitrile hydratase, [3] cytochrome oxidase, [4] and nitrogenases, [5] and in the use of metallonitrosyl complexes as pharmaceutical reagents.…”

Section: Introductionmentioning

confidence: 99%

“…2) It is known that free heme model compounds usually show faster association and dissociation rates than found in hemeproteins as a result of the steric hindrance [1] and in this case the steric hindrance around the iron complex is higher in the case of the dinuclear complex as compared to the mononuclear species, which will slow down the associative binding of NO. Taking into account all the above information, the mechanism for the reaction of NO with dimer 1 can be represented as shown in Scheme 2.…”

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Mechanistic Information on the Reversible Binding of NO to Mono‐ and Dinuclear Fe^II Complexes of a Biomimetic S₄N Ligand

Shaban

Eldik

2010

Eur J Inorg Chem

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Structural and mechanistic information on the binding of NO to mono-and dinuclear [Fe II (S 4 NNEt 2 )] fragments as potential catalysts for the removal of NO from effluent gas streams have been obtained from concentration, temperature and pressure dependent kinetic measurements using stoppedflow techniques. The results indicate that the steric and electronic structure only affect the rate but not the nature of the binding mechanism by which NO coordinates to the selected complexes. Therefore, the sterically hindered dinuclear complex [Fe II (S 4 NNEt 2 )] 2 binds NO ca. eight times slower than

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Multistep Oxidation Kinetics of [FeII(cdta)] [cdta =N,N′,N′′,N′′′-(1,2-Cyclohexanediamine)tetraacetate] with Molecular Oxygen

Seibig¹,

Eldik²

1999

Eur. J. Inorg. Chem.

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The complicated oxidation kinetics of the reaction of [FeII(cdta)] [cdta = 1,2‐(N,N′‐ cyclohexanediamine)tetraacetate] with molecular oxygen was investigated as a function of [FeII], [O2], pH, temperature and pressure. In the presence of an excess of [FeII(cdta)] three steps could be observed, for which the following rate constants were found at 25°C; k1 = 1080 ± 16 M−1 s−1, k2 = 103 ± 4 M−1 s−1 and k3 = 59 ± 5 M−1 s−1. These reaction steps can be accounted for in terms of the following mechanism: (1) [FeII(cdta)H2O]2– reacts with O2 by a substitution process to form [FeII(cdta)O2]2–; (2) electron‐transfer to form an FeIII‐superoxo species; (3) subsequent bridge formation followed by electron‐transfer to give [(cdta)FeIII‐O22–‐FeIII(cdta)]4–; and (4) a fast decomposition of the peroxide intermediate yielding the monomeric [FeIII(cdta)] and H2O2. Rate and activation parameters for these steps are reported and discussed in terms of the postulated mechanism and in reference to available literature data.

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Influence of the polyamino carboxylate chelating ligand (L) on the kinetics and mechanism of the formation of FeII(L)NO in the system FeII(L)/NO/HONO/NO2- in aqueous solution

Cited by 79 publications

References 0 publications

Importance of Iron Complexation for Fenton-Mediated Hydroxyl Radical Production at Circumneutral pH

Importance of Iron Complexation for Fenton-Mediated Hydroxyl Radical Production at Circumneutral pH

Mechanistic Information on the Reversible Binding of NO to Mono‐ and Dinuclear Fe^II Complexes of a Biomimetic S₄N Ligand

Multistep Oxidation Kinetics of [FeII(cdta)] [cdta =N,N′,N′′,N′′′-(1,2-Cyclohexanediamine)tetraacetate] with Molecular Oxygen

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Influence of the polyamino carboxylate chelating ligand (L) on the kinetics and mechanism of the formation of FeII(L)NO in the system FeII(L)/NO/HONO/NO2- in aqueous solution

Cited by 79 publications

References 0 publications

Importance of Iron Complexation for Fenton-Mediated Hydroxyl Radical Production at Circumneutral pH

Importance of Iron Complexation for Fenton-Mediated Hydroxyl Radical Production at Circumneutral pH

Mechanistic Information on the Reversible Binding of NO to Mono‐ and Dinuclear FeII Complexes of a Biomimetic S4N Ligand

Multistep Oxidation Kinetics of [FeII(cdta)] [cdta =N,N′,N′′,N′′′-(1,2-Cyclohexanediamine)tetraacetate] with Molecular Oxygen

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Mechanistic Information on the Reversible Binding of NO to Mono‐ and Dinuclear Fe^II Complexes of a Biomimetic S₄N Ligand