Kinetics and mechanism of a fast leuco-Methylene Blue oxidation by copper(II)-halide species in acidic aqueous media

Olga Impert, A. Katafias, Przemyslaw Kita, Andrew Mills, Aleksandra Pietkiewiez-Graczyk, Grzegorz Wrzeszcz

Research output: Contribution to journalArticle

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Abstract

The kinetics of a fast leuco-Methylene Blue (LMB) re-oxidation to Methylene Blue (MB) by copper(II)-halide (Cl-, Br-) complexes in acidic aqueous media has been studied spectrophotometrically using a stopped-flow technique. The reaction follows a simple first order rate expression under an excess of the copper(II) species (and H+(aq)), and the pseudo-first order rate constant (k'(obs)) is largely independent of the atmosphere used (air, oxygen, argon). The rate law, at constant Cl- (Br-) anion concentration, is given by the expression: (d[MB+])/dt = ((k(a)K[H+] + k(b))/(1 + K[H+])).[Cu-II][LMB] = k'(obs)[LMB], where K is the protonation constant, and k(a) and k(b) are the pseudo-second order rate constants for protonated and deprotonated forms of LMB, respectively The rate law was determined based on the observed k'(obs) vs. [Cu-II] and [H+] dependences. The rate dramatically increases with [Cl-] over the range: 0.1-1.5 M, reflecting the following reactivity order: Cu2+(aq) << CuCl+(aq) <...< CuCl42-. The slow re-oxidation of LMB by oxygen has also been briefly examined at different [H+]. ESR results provide clear evidence for the formation of an intermediate radical. The mechanistic consequences of all these results are discussed.
LanguageEnglish
Pages348-353
Number of pages5
JournalDalton Transactions
Volume2003
Issue number3
DOIs
Publication statusPublished - 2003

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Methylene Blue
Copper
Oxidation
Kinetics
Rate constants
Oxygen
Argon
Protonation
Anions
Paramagnetic resonance
Air

Keywords

  • LEUCOMETHYLENE BLUE
  • ASCORBIC-ACID
  • EQUILIBRIUM
  • SYSTEM

Cite this

Impert, O., Katafias, A., Kita, P., Mills, A., Pietkiewiez-Graczyk, A., & Wrzeszcz, G. (2003). Kinetics and mechanism of a fast leuco-Methylene Blue oxidation by copper(II)-halide species in acidic aqueous media. Dalton Transactions, 2003(3), 348-353. https://doi.org/10.1039/b205786g
Impert, Olga ; Katafias, A. ; Kita, Przemyslaw ; Mills, Andrew ; Pietkiewiez-Graczyk, Aleksandra ; Wrzeszcz, Grzegorz. / Kinetics and mechanism of a fast leuco-Methylene Blue oxidation by copper(II)-halide species in acidic aqueous media. In: Dalton Transactions. 2003 ; Vol. 2003, No. 3. pp. 348-353.
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abstract = "The kinetics of a fast leuco-Methylene Blue (LMB) re-oxidation to Methylene Blue (MB) by copper(II)-halide (Cl-, Br-) complexes in acidic aqueous media has been studied spectrophotometrically using a stopped-flow technique. The reaction follows a simple first order rate expression under an excess of the copper(II) species (and H+(aq)), and the pseudo-first order rate constant (k'(obs)) is largely independent of the atmosphere used (air, oxygen, argon). The rate law, at constant Cl- (Br-) anion concentration, is given by the expression: (d[MB+])/dt = ((k(a)K[H+] + k(b))/(1 + K[H+])).[Cu-II][LMB] = k'(obs)[LMB], where K is the protonation constant, and k(a) and k(b) are the pseudo-second order rate constants for protonated and deprotonated forms of LMB, respectively The rate law was determined based on the observed k'(obs) vs. [Cu-II] and [H+] dependences. The rate dramatically increases with [Cl-] over the range: 0.1-1.5 M, reflecting the following reactivity order: Cu2+(aq) << CuCl+(aq) <...< CuCl42-. The slow re-oxidation of LMB by oxygen has also been briefly examined at different [H+]. ESR results provide clear evidence for the formation of an intermediate radical. The mechanistic consequences of all these results are discussed.",
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Impert, O, Katafias, A, Kita, P, Mills, A, Pietkiewiez-Graczyk, A & Wrzeszcz, G 2003, 'Kinetics and mechanism of a fast leuco-Methylene Blue oxidation by copper(II)-halide species in acidic aqueous media' Dalton Transactions, vol. 2003, no. 3, pp. 348-353. https://doi.org/10.1039/b205786g

Kinetics and mechanism of a fast leuco-Methylene Blue oxidation by copper(II)-halide species in acidic aqueous media. / Impert, Olga; Katafias, A.; Kita, Przemyslaw; Mills, Andrew; Pietkiewiez-Graczyk, Aleksandra; Wrzeszcz, Grzegorz.

In: Dalton Transactions, Vol. 2003, No. 3, 2003, p. 348-353.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Kinetics and mechanism of a fast leuco-Methylene Blue oxidation by copper(II)-halide species in acidic aqueous media

AU - Impert, Olga

AU - Katafias, A.

AU - Kita, Przemyslaw

AU - Mills, Andrew

AU - Pietkiewiez-Graczyk, Aleksandra

AU - Wrzeszcz, Grzegorz

PY - 2003

Y1 - 2003

N2 - The kinetics of a fast leuco-Methylene Blue (LMB) re-oxidation to Methylene Blue (MB) by copper(II)-halide (Cl-, Br-) complexes in acidic aqueous media has been studied spectrophotometrically using a stopped-flow technique. The reaction follows a simple first order rate expression under an excess of the copper(II) species (and H+(aq)), and the pseudo-first order rate constant (k'(obs)) is largely independent of the atmosphere used (air, oxygen, argon). The rate law, at constant Cl- (Br-) anion concentration, is given by the expression: (d[MB+])/dt = ((k(a)K[H+] + k(b))/(1 + K[H+])).[Cu-II][LMB] = k'(obs)[LMB], where K is the protonation constant, and k(a) and k(b) are the pseudo-second order rate constants for protonated and deprotonated forms of LMB, respectively The rate law was determined based on the observed k'(obs) vs. [Cu-II] and [H+] dependences. The rate dramatically increases with [Cl-] over the range: 0.1-1.5 M, reflecting the following reactivity order: Cu2+(aq) << CuCl+(aq) <...< CuCl42-. The slow re-oxidation of LMB by oxygen has also been briefly examined at different [H+]. ESR results provide clear evidence for the formation of an intermediate radical. The mechanistic consequences of all these results are discussed.

AB - The kinetics of a fast leuco-Methylene Blue (LMB) re-oxidation to Methylene Blue (MB) by copper(II)-halide (Cl-, Br-) complexes in acidic aqueous media has been studied spectrophotometrically using a stopped-flow technique. The reaction follows a simple first order rate expression under an excess of the copper(II) species (and H+(aq)), and the pseudo-first order rate constant (k'(obs)) is largely independent of the atmosphere used (air, oxygen, argon). The rate law, at constant Cl- (Br-) anion concentration, is given by the expression: (d[MB+])/dt = ((k(a)K[H+] + k(b))/(1 + K[H+])).[Cu-II][LMB] = k'(obs)[LMB], where K is the protonation constant, and k(a) and k(b) are the pseudo-second order rate constants for protonated and deprotonated forms of LMB, respectively The rate law was determined based on the observed k'(obs) vs. [Cu-II] and [H+] dependences. The rate dramatically increases with [Cl-] over the range: 0.1-1.5 M, reflecting the following reactivity order: Cu2+(aq) << CuCl+(aq) <...< CuCl42-. The slow re-oxidation of LMB by oxygen has also been briefly examined at different [H+]. ESR results provide clear evidence for the formation of an intermediate radical. The mechanistic consequences of all these results are discussed.

KW - LEUCOMETHYLENE BLUE

KW - ASCORBIC-ACID

KW - EQUILIBRIUM

KW - SYSTEM

UR - http://www.rsc.org/Publishing/Journals/DT/article.asp?doi=b205786g

U2 - 10.1039/b205786g

DO - 10.1039/b205786g

M3 - Article

VL - 2003

SP - 348

EP - 353

JO - Dalton Transactions

T2 - Dalton Transactions

JF - Dalton Transactions

SN - 1477-9226

IS - 3

ER -