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Holder, Alvin A.; Brown, Ross F. G.; Marshall, Sophia C.; Payne, Vince C. R.; Cozier, Maria D.; Alleyne, Walter A.; Bovell, Christopher O.

doi:10.1023/a:1007046125017

Cited by 17 publications

(12 citation statements)

References 18 publications

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“…The reaction between V(V) and ascorbic acid is pH dependent [85][86][87]. The initial study by Kustin and Toppen of the V(V)-ascorbic acid system was carried out below pH 1 [15].…”

Section: Reaction Of Ascorbic Acid With the Dioxovanadium(v) Cation Amentioning

confidence: 99%

Impairment of ascorbic acid’s anti-oxidant properties in confined media: Inter and intramolecular reactions with air and vanadate at acidic pH

Crans

Baruah

Gaidamauskas

et al. 2008

Journal of Inorganic Biochemistry

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“…The reaction between V(V) and ascorbic acid is pH dependent [85][86][87]. The initial study by Kustin and Toppen of the V(V)-ascorbic acid system was carried out below pH 1 [15].…”

Section: Reaction Of Ascorbic Acid With the Dioxovanadium(v) Cation Amentioning

confidence: 99%

Impairment of ascorbic acid’s anti-oxidant properties in confined media: Inter and intramolecular reactions with air and vanadate at acidic pH

Crans

Baruah

Gaidamauskas

et al. 2008

Journal of Inorganic Biochemistry

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“…Our research group and collaborators have been interested in the development of transition metal complexes that contain cobalt metal centres [24][25][26][27][28][29][30][31], as well as inorganic reaction mechanisms that involve electron transfer processes [25,26,[32][33][34][35][36]. In a recent report, we outlined the preparation and application a novel mixed-metal binuclear ruthenium(II)-cobalt(II) photocatalysts ([Ru(pbt) 2 (Lpyr)Co(dmgBF 2 ) 2 (H 2 O)](PF 6 ) 2 (where pbt = 2-(2′-pyridyl)benzothiazole, L-pyr = (4pyridine)oxazolo [4,5-f]phenanthroline, and dmgBF 2 = difluoroboryldimethylglyoximato) for photocatalytic production of hydrogen [24].…”

Section: Introductionmentioning

confidence: 99%

Assessing the stability of the Co(I) species of two mononuclear dichlorocobalt compounds bearing 2,2′-bipyridine and trans-2-(2′-quiolyl)methylene-3-quinuclidione via 59Co NMR spectroscopy, electrochemical, and catalyzed proton electroreduction studies

Lawrence

Holder

2016

Inorganica Chimica Acta

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The Co(I) species resulting from the reduction of two mononuclear species [CoL n Cl 2 ] (where L = 2,2'bipyridine (bpy) and n = 2, or L = trans-2-(2'-quiolyl)methylene-3-quinuclidione (quin) and n = 1), was studied by 59 Co NMR spectroscopy, UV-visible-NIR spectroscopy, and spectroelectrochemical techniques. A quasi-stable Co(I) species produced by the reduction of [Co(bpy) 2 Cl 2 ] was studied and gave a 59 Co NMR spectroscopic chemical shift of 2934 ppm in CD 3 CN-D 2 O (4:1, v/v) and a broad peak of  max = 600 nm in the UV-visible region of the spectrum. The Co(I) species generated from [Co(quin)Cl 2) (when reduced by electrochemical methods) was found to be unstable and produced a transient of  max = 530 nm. Both [CoL n Cl 2 ] species were examined as electrocatalysts for the proton reduction in an acetonitrile-water solvent mixture in the presence of p-cyanoanilinium tetrafluoroborate. The electrochemical properties of both species showed a dependence on the supporting electrolyte which also affected the electrocatalytic behavior. The simulation of the cyclic voltammograms in CH 3 CN-H 2 O (4:1, v/v) allowed for the extraction of kinetic data and suggested a homogenous reaction following the reduction to a Co(I) metal centre with rate constants k = 0.01 s-1 and 2 M s-1 for the Co(I) species with the ligands, bpy and quin, respectively. Analysis of the head space of controlled potential electrolysis experiments for an hour, in the presence of p-cyanoanilinium tetrafluoroborate, confirmed the production of hydrogen, and also showed that the supporting electrolyte affected the production of hydrogen at a glassy carbon electrode in CH 3 CN-H 2 O (either 1:1 or 4:1, v/v). A mechanism was postulated which involved a Co III-H species as the most likely candidate and appeared to involve both a homolytic and a heterolytic pathway towards the production of hydrogen.

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“…When the reacting species have similar charges, the rate of reaction is observed to increase, whereas when the reacting species have opposite charges, the rate of reaction is observed to decrease [35,56]. Upon varying the ionic strength as shown by in our kinetic data in Table 3, as the ionic strength is increased, the k obs value is increased.…”

Section: Resultsmentioning

confidence: 88%

“…The ionic strength has been recognized for its effects on the rates of ionic reactions [35,56]. When the reacting species have similar charges, the rate of reaction is observed to increase, whereas when the reacting species have opposite charges, the rate of reaction is observed to decrease [35,56].…”

Section: Resultsmentioning

confidence: 99%

Kinetics and mechanism of the oxidation of a cobaloxime by sodium hypochlorite in aqueous solution: Is it an outer-sphere mechanism?

Celestine

Joseph

Holder

2017

Inorganica Chimica Acta

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The kinetics and mechanism of the oxidation of [Co(dmgBF2)2(OH2)2] (where dmgBF2 = difluoroboryldimethylglyoximato) by sodium hypochlorite (NaOCl) were investigated by stopped-flow spectrophotometry at 450 nm over the temperature range of 10 °C ≤ θ ≤ 25 °C, pH range of 5.0 ≤ pH ≤ 7.8, and at an ionic strength of 0.60 M (NaCl). The pKa1 value for [Co(dmgBF2)2(H2O)2] was calculated as 5.27 ± 0.14 at I = 0.60 (NaCl). The redox process was dependent on pH and oxidant concentration in a complex manner, that is, kobs = ((k2[H+] + k1Ka)/([H+] + Ka))[OCl−]T, where at 25.3 °C, k1 was calculated as 3.54 × 104 M−1 s−1, and k2 as 2.51 × 104 M−1 cm−1. At a constant pH value, while varying the concentration of sodium hypochlorite two rate constants were calculated, viz., k′1 = 7.56 s−1 (which corresponded to a reaction pathway independent of the NaOCl concentration) and k′2 = 2.26 × 104 M−1 s−1, which was dependent on the concentration of NaOCl. From the variation in pH, ΔnormalH1≠,ΔnormalH2≠,ΔnormalS1≠, and ΔnormalS2≠ were calculated as 58 ± 16 kJ mol−1, 46 ± 1 kJ mol−1, 34 ± 55 J mol−1 K−1, and −6 ± 4 Jmol−1 K−1, respectively. The self-exchange rate constant, k11, for sodium hypochlorite (as ClO−) was calculated to be 1.2 × 103 M−1 s−1, where an outer-sphere electron transfer mechanism was assumed. A green product, [Co(dmgBF2)2(OH2)(OH)]·1.75NaOCl, which can react with DMSO, was isolated from the reaction at pH 8.04 with a yield of 13%.

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Untitled

Cited by 17 publications

References 18 publications

Impairment of ascorbic acid’s anti-oxidant properties in confined media: Inter and intramolecular reactions with air and vanadate at acidic pH

Impairment of ascorbic acid’s anti-oxidant properties in confined media: Inter and intramolecular reactions with air and vanadate at acidic pH

Assessing the stability of the Co(I) species of two mononuclear dichlorocobalt compounds bearing 2,2′-bipyridine and trans-2-(2′-quiolyl)methylene-3-quinuclidione via 59Co NMR spectroscopy, electrochemical, and catalyzed proton electroreduction studies

Kinetics and mechanism of the oxidation of a cobaloxime by sodium hypochlorite in aqueous solution: Is it an outer-sphere mechanism?

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