Oxidation of ascorbic acid by a (salen)ruthenium(<scp>vi</scp>) nitrido complex in aqueous solution

Wang, Qian; Man, Wai‐Lun; Lam, William W. Y.; Lau, Tai‐Chu

doi:10.1039/c4cc07568d

Cited by 10 publications

(9 citation statements)

References 35 publications

(29 reference statements)

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“…However, the reactivity of nitrido complexes towards inorganic substrates has received less attention . Moreover, there are relatively few studies on the reactivity of metal nitrido complexes in aqueous solutions; most nitrido complexes are either insoluble or unstable in water . We report herein the kinetics and mechanism of the reduction of Ru VI N by sulfite in aqueous acidic solutions.…”

Section: Figurementioning

confidence: 97%

“…[3,11] Moreover, there are relatively few studies on the reactivity of metal nitrido complexes in aqueous solutions;m ost nitrido complexes are either insoluble or unstablei nw ater. [12,13] We report herein the kinetics and mechanism of the reduction of Ru VI Nb ysulfite in aqueous acidic solutions. Althought he oxidation of sulfite by transition-metal complexes has been extensively studied, most of theser eactions are either one-electron outer-sphere processes involving substitution-inert oxidants, or one-electron inner-sphere processes involving labile oxidants.…”

mentioning

confidence: 99%

“…There are an umber of possible mechanisms that may account for the large KIE effect for the HSO 3 À pathway: 1)Rate-limitingp rotonation of Ru VI Nf ollowed by rapid NÀS bond formation ([Eqs. (12) and (13)]):…”

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confidence: 99%

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Kinetics and Mechanism of the Reaction of a Ruthenium(VI) Nitrido Complex with HSO₃⁻ and SO₃²⁻ in Aqueous Solution

Wang

Zhao

Man

et al. 2016

Chemistry A European J

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The kinetics and mechanism of the reaction of S(IV) (SO3 (2-) +HSO3 (-) ) with a ruthenium(VI) nitrido complex, [(L)Ru(VI) (N)(OH2 )](+) (Ru(VI) N, L=N,N'-bis(salicylidene)-o-cyclohexyldiamine dianion), in aqueous acidic solutions are reported. The kinetic results are consistent with parallel pathways involving oxidation of HSO3 (-) and SO3 (2-) by Ru(VI) N. A deuterium isotope effect of 4.7 is observed in the HSO3 (-) pathway. Based on experimental results and DFT calculations the proposed mechanism involves concerted N-S bond formation (partial N-atom transfer) between Ru(VI) N and HSO3 (-) and H(+) transfer from HSO3 (-) to a H2 O molecule.

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Section: Figurementioning

confidence: 97%

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confidence: 99%

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Kinetics and Mechanism of the Reaction of a Ruthenium(VI) Nitrido Complex with HSO₃⁻ and SO₃²⁻ in Aqueous Solution

Wang

Zhao

Man

et al. 2016

Chemistry A European J

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“…As one of the most important antioxidants, the kinetics and mechanisms of vitamin C/ascorbic acid reactions with various oxidants have been explored extensively [9,10,[16][17][18][19][20]; the oxidants include reactive oxygen species such as HO 2 /O 2 radicals and peroxynitrite, and some metal ions/complexes [16][17][18][19]. Among the metal ions/complexes, single electron oxidants apparently dominate the exploration [9,10].…”

Section: Introductionmentioning

confidence: 99%

Antioxidative Reactivity of L-Ascorbic Acid and D-Isoascorbic Acid Species towards Reduction of Hexachloroiridate (IV)

Zhang

Xia

Zhang

et al. 2021

Journal of Chemistry

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The pair [IrCl6]2–/[IrCl6]3– has been demonstrated to be a good redox probe in biological systems while L-ascorbic acid (AA) is one of the most important antioxidants. D-isoascorbic acid (IAA) is an epimer of AA and is widely used as an antioxidant in various foods, beverages, meat, and fisher products. Reductions of [IrCl6]2– by AA and IAA have been analyzed kinetically and mechanistically in this work. The reductions strictly follow overall second-order kinetics and the observed second-order rate constants were collected in the pH region of 0 ≤ pH ≤ 2.33 at 25.0°C. Spectrophotometric titration experiments revealed a well-defined 1 : 2 stoichiometry, namely Δ[AA] : Δ[Ir(IV)] or Δ[IAA] : Δ[Ir(IV)] = 1 : 2, indicating that L-dehydroascorbic acid (DHA) and D-dehydroisoascorbic acid (DHIA) were the oxidation products of AA and IAA, respectively. A reaction mechanism is suggested involving parallel reactions of [IrCl6]2– with three protolysis species of AA/IAA (fully protonated, monoanionic, and dianionic forms) as the rate-determining steps and formation of ascorbic/isoascorbic and ascorbate/isoascorbate radicals; in each of the steps, [IrCl6]2– acquires an electron via an outer-sphere electron transfer mode. Rate constants of the rate-determining steps have been derived or estimated. The fully protonated forms of AA and IAA display virtually identical reactivity whereas ascorbate and isoascorbate monoanions have a significant reactivity difference. The ascorbate and isoascorbate dianions are extremely reactive and their reactions with [IrCl6]2– proceed with the diffusion-controlled rate. The species versus pH and the species reactivity versus pH distribution diagrams were constructed endowing that the ascorbate/isoascorbate monoanionic form dominated the total reactivity at physiological pH. In addition, the value of pKa1 = 3.74 ± 0.05 for IAA at 25.0°C and 1.0 M ionic strength was determined in this work.

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“…In this case, kinetic and mechanistic studies suggest that proton-coupled electron transfer processes are involved in the reaction. Although there is an extensive aqueous redox chemistry of metal–oxo species, corresponding aqueous metal nitrido chemistry has received much less attention. − …”

Section: Introductionmentioning

confidence: 99%

Reduction of Ru^VI≡N to Ru^III—NH₃ by Cysteine in Aqueous Solution

et al. 2018

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The reduction of metal nitride to ammonia is a key step in biological and chemical nitrogen fixation. We report herein the facile reduction of a ruthenium(VI) nitrido complex [(L)Ru(N)(OH)] (1, L = N, N'-bis(salicylidene)- o-cyclohexyldiamine dianion) to [(L)Ru(NH)(OH)] by l-cysteine (Cys), an ubiquitous biological reductant, in aqueous solution. At pH 1.0-5.3, the reaction has the following stoichiometry: [(L)Ru(N)(OH)] + 3HSCHCH(NH)CO → [(L)Ru(NH)(OH)] + 1.5(SCHCH(NH)CO). Kinetic studies show that at pH 1 the reaction consists of two phases, while at pH 5 there are three distinct phases. For all phases the rate law is rate = k[1][Cys]. Studies on the effects of acidity indicate that both HSCHCH(NH)CO and SCHCH(NH)CO are kinetically active species. At pH 1, the reaction is proposed to go through [(L)Ru(NHSCHCHNHCOH)(OH)] (2a), [(L)Ru(NHSCHCHNHCOH)(OH)] (3), and [(L)Ru(NH)(OH)] (4) intermediates. On the other hand, at pH around 5, the proposed intermediates are [(L)Ru(NHSCHCHNHCO)(OH)] (2b) and [(L)Ru(NH)(OH)] (4). The intermediate ruthenium(IV) sulfilamido species, [(L)Ru(NHSCHCHNHCOH)(OH)] (2a) and the final ruthenium(III) ammine species, [(L)Ru(NH)(MeOH)] (5) (where HO was replaced by MeOH) have been isolated and characterized by various spectroscopic methods.

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Oxidation of ascorbic acid by a (salen)ruthenium(vi) nitrido complex in aqueous solution

Cited by 10 publications

References 35 publications

Kinetics and Mechanism of the Reaction of a Ruthenium(VI) Nitrido Complex with HSO₃⁻ and SO₃²⁻ in Aqueous Solution

Kinetics and Mechanism of the Reaction of a Ruthenium(VI) Nitrido Complex with HSO₃⁻ and SO₃²⁻ in Aqueous Solution

Antioxidative Reactivity of L-Ascorbic Acid and D-Isoascorbic Acid Species towards Reduction of Hexachloroiridate (IV)

Reduction of Ru^VI≡N to Ru^III—NH₃ by Cysteine in Aqueous Solution

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Oxidation of ascorbic acid by a (salen)ruthenium(vi) nitrido complex in aqueous solution

Cited by 10 publications

References 35 publications

Kinetics and Mechanism of the Reaction of a Ruthenium(VI) Nitrido Complex with HSO3− and SO32− in Aqueous Solution

Kinetics and Mechanism of the Reaction of a Ruthenium(VI) Nitrido Complex with HSO3− and SO32− in Aqueous Solution

Antioxidative Reactivity of L-Ascorbic Acid and D-Isoascorbic Acid Species towards Reduction of Hexachloroiridate (IV)

Reduction of RuVI≡N to RuIII—NH3 by Cysteine in Aqueous Solution

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Kinetics and Mechanism of the Reaction of a Ruthenium(VI) Nitrido Complex with HSO₃⁻ and SO₃²⁻ in Aqueous Solution

Kinetics and Mechanism of the Reaction of a Ruthenium(VI) Nitrido Complex with HSO₃⁻ and SO₃²⁻ in Aqueous Solution

Reduction of Ru^VI≡N to Ru^III—NH₃ by Cysteine in Aqueous Solution