Kinetics and mechanism of cobalt(III) oxidation of bis(2,2′,6′,2″-terpyridine) iron(II) in sulfuric acid solutions

Satyanarayana, Tatakuntla; Anipindi, Nageswara Rao

doi:10.1007/bf02137669

Cited by 6 publications

(5 citation statements)

References 13 publications

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“…The oxidation is fast with O 3 , 14 Mn(IV), 15 Mn(III), 16 and Co(III). 17 In these systems, the stopped-flow technique was used for monitoring the absorbance change, and the reactions follow overall second-order kinetics (the order with respect to both Fe(tpy) 2 2+ and the oxidants is one), with the exception of O 3 . The reaction of the complex with excess ozone does not obey a simple first-order rate equation.…”

Section: +mentioning

confidence: 84%

“…There are several reports in the literature on the kinetics of the oxidation of Fe(tpy) 2 2+ under strongly acidic conditions. The oxidation is fast with O 3 , Mn(IV), Mn(III), and Co(III) . In these systems, the stopped-flow technique was used for monitoring the absorbance change, and the reactions follow overall second-order kinetics (the order with respect to both Fe(tpy) 2 2+ and the oxidants is one), with the exception of O 3 .…”

Section: Introductionmentioning

confidence: 99%

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Kinetics and Mechanism of the Autocatalytic Oxidation of Bis(terpyridine)iron(II) by Peroxomonosulfate Ion (Oxone) in Acidic Medium

2017

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The autocatalytic oxidation of the bis(terpyridine)iron(II) complex, Fe(tpy) by peroxomonosulfate ion (PMS) proceeds via the formation of the corresponding iron(III) complex (Fe(tpy)) as the primary oxidation product. The proton-assisted dissociation of Fe(tpy) and subsequent oxidation of Fe are side reactions in this system. In the initial stage of the reaction, a 1:1 adduct is formed between PMS and bis(terpyridine)iron(II), which decomposes in an intramolecular electron transfer reaction step. The autocatalytic role of Fe(tpy) was also confirmed in the overall process. This effect is interpreted by considering the formation of an additional adduct between PMS and Fe(tpy). The decomposition of the adduct yields two strong oxidizing intermediates, an Fe(IV) species and SO, which consume the iron(II) complex in rapid reaction steps. A detailed kinetic model was postulated for the overall oxidation of Fe(tpy) by PMS. The equilibrium constants for the formation of the adducts between PMS and complexes Fe(tpy) and Fe(tpy) were estimated as 129 ± 18 M and 87 ± 10 M, respectively. In contrast to the closely related Fe(phen)-PMS reaction, the N-oxide derivative of the ligand (tpyO) does not have any kinetic role in the overall process because of the very slow formation of the N-oxide in the reaction.

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Section: +mentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Kinetics and Mechanism of the Autocatalytic Oxidation of Bis(terpyridine)iron(II) by Peroxomonosulfate Ion (Oxone) in Acidic Medium

2017

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“…20−23 It has been reported that aqueous Co(III) not only possesses a high standard reduction potential (E 0 (Co 3+ /Co 2+ ) = 1.92 V), 24 which is close to that of the aqueous Fe(IV)-oxo complex (E 0 (Fe IV O 2+ /Fe 3+ ) = 2.0 V) 25 but also exhibits moderate oxidation reactivity toward various inorganic ions and organic compounds. [21][22][23]26,27 Moreover, it has been confirmed that Co(III) participates in the oxidation of the inorganic ions Br − and Cl − by the Co(II)/PMS system. For instance, our previous studies revealed that Co(III) dominated the transformation of Br − and Cl − to HOCl and HOBr, respectively, in the Co(II)/ PMS system.…”

Section: Introductionmentioning

confidence: 93%

“…As an alternative reactive Co intermediate, aqueous Co(III), readily prepared by the electrochemical process, has been widely investigated and rigorously characterized. − It has been reported that aqueous Co(III) not only possesses a high standard reduction potential ( E 0 (Co 3+ /Co 2+ ) = 1.92 V), which is close to that of the aqueous Fe(IV)-oxo complex ( E 0 (Fe IV O 2+ /Fe 3+ ) = 2.0 V) but also exhibits moderate oxidation reactivity toward various inorganic ions and organic compounds. − ,, Moreover, it has been confirmed that Co(III) participates in the oxidation of the inorganic ions Br – and Cl – by the Co(II)/PMS system. For instance, our previous studies revealed that Co(III) dominated the transformation of Br – and Cl – to HOCl and HOBr, respectively, in the Co(II)/PMS system. , Nevertheless, it remains a significant challenge to confirm whether Co(III) is involved in micropollutant abatement by the Co(II)/PMS system and to further differentiate the relative contribution of Co(III) from that of free radicals and other potentially formed reactive Co intermediates.…”

Section: Introductionmentioning

confidence: 99%

Reinvestigation on High-Valent Cobalt for the Degradation of Micropollutants in the Co(II)/Peroxymonosulfate System: Roles of Co(III)

Cao,

Wang,

et al. 2024

Environ. Sci. Technol.

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Recently, reactive cobalt (Co) species, including Co(IV)-oxo and Co(II)-OOSO3 – complexes, were proposed to be the primary intermediates formed during the process of activating peroxymonosulfate (PMS) by Co(II), mainly based on the observation that the methyl phenyl sulfoxide (MPSO) probe was transformed to methyl phenyl sulfone (MPSO2) in this process. However, in this work, we rationalized the results of the MPSO probe assay based on the chemistry of aqueous Co(III), an alternative reactive Co species. Moreover, 18O-labeled water experiments and Raman spectroscopy analysis clearly proved the Co(III) formation in the Co(II)/PMS system. In parallel, sulfate radicals (SO4 •–) and hydroxyl radicals (HO•) were also involved in this system. Further, the relative contribution of Co(III) to the abatement of carbamazepine (CBZ), a representative micropollutant, in the Co(II)/PMS system was significantly increased by increasing the Co(II) dosage but was dramatically decreased by improving the PMS dosage and increasing the pH from 3 to 7. Additionally, the degradation pathway of CBZ by Co(III) and the Co(II)/PMS system was comparatively explored, confirming that Co(III) participated in the hydroxylation, carbonylation, deacetylation, and ring reduction of CBZ by the Co(II)/PMS system. Our work addresses the controversy regarding the reactive Co species involved in the Co(II)/PMS system with evidence of Co(III) as the chief one, which highlights the significance of re-evaluating the relative contribution of Co(III) in relevant environmental decontamination processes.

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“…The disappearance of the [Fe II Tpy 2 ] 2+ complex is also evidenced for both oxidizer molecules by the loss of the absorption band at 556 nm, characteristic of the Fe(II) complex, in the UV/vis spectrum (Figure a). According to the literature, the formed iron(III)–bis(terpyridine) complexes are not kinetically stable and exhibit a very high lability. − Considering now the consequences at the microgel scale, a rapid loss of the scattered intensity was observed five minutes after the addition of H 2 O 2 (Figure c; Supporting Information, Figure S7 for KPS). The loss of scattering intensity indeed reflects the dissociation of the microgels into linear chains as the latter do not scatter light unlike colloidal microgels, at the same polymer concentration.…”

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confidence: 99%

Oxidation-Responsive Emulsions Stabilized by Cleavable Metallo-Supramolecular Cross-Linked Microgels

et al. 2020

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An original route to develop an advanced class of microgels emulsifiers containing stimulable metallo-supramolecular instead of frozen covalent crosslinks is reported. The poly(Nisopropylmethacrylamide) (PNiPMAM) chains of the microgel are connected by iron(II)bis(terpyridine) coordination supramolecular complexes that can be cleaved on demand leading to unique properties both at interfaces and in volume. The microgels synthesis is undemanding and the characterization of their supramolecular structure can be precisely achieved by standard methods.Singularly, interfaces of an oil-in-water emulsion stabilized by the supramolecular particles can be triggered at molecular scale by oxidation of Fe(II) to Fe(III), leading to emulsion breaking. In bulk, we show that a microgel dispersion can indeed be transformed into a polymer solution upon oxidation. Our study paves the road to the discovery of unusual microgel properties as our proof-of-concept can be extended to different supramolecular chemistry and architecture.

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Kinetics and mechanism of cobalt(III) oxidation of bis(2,2′,6′,2″-terpyridine) iron(II) in sulfuric acid solutions

Cited by 6 publications

References 13 publications

Kinetics and Mechanism of the Autocatalytic Oxidation of Bis(terpyridine)iron(II) by Peroxomonosulfate Ion (Oxone) in Acidic Medium

Kinetics and Mechanism of the Autocatalytic Oxidation of Bis(terpyridine)iron(II) by Peroxomonosulfate Ion (Oxone) in Acidic Medium

Reinvestigation on High-Valent Cobalt for the Degradation of Micropollutants in the Co(II)/Peroxymonosulfate System: Roles of Co(III)

Oxidation-Responsive Emulsions Stabilized by Cleavable Metallo-Supramolecular Cross-Linked Microgels

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