Kinetics of oxidation of glutathione by an octahedral cobalt(III) complex with phenolate–amide–amine coordination

Nayak, Suprava ; Reddy, Venugopal K. ; Dash, Anadi C. (2014) Kinetics of oxidation of glutathione by an octahedral cobalt(III) complex with phenolate–amide–amine coordination Transition Metal Chemistry, 39 (2). pp. 177-187. ISSN 0340-4285

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Official URL: http://link.springer.com/article/10.1007%2Fs11243-...

Related URL: http://dx.doi.org/10.1007/s11243-013-9787-4

Abstract

The reduction of the octahedral cobalt(III) complex CoIII(HL)·9H2O, H4L = 1,8-bis(2-hydroxybenzamido)-3,6-diazaoctane by glutathione (GSH) has been studied by conventional spectrophotometry at 25.0 ≤ t/°C ≤ 45.0, 0.02 ≤ [H+]/mol dm−3 ≤ 0.20 and I = 0.3 mol dm−3 (NaClO4). The reaction is biphasic. The fast initial phase is attributed to the H+-induced formation of the mixed ligand complex, [CoIII(H2L)GSH]+, for which the rate-limiting step is the chelate ring opening via CoIII–NH (amide–N) bond cleavage of the protonated species, [CoIII(H2L)]+. Outer-sphere association equilibria between GSH/GSH2 + and [CoIII(H2L)]+ substantially retard the ring opening process and consequently the mixed ligand complex formation. This is then followed by a slow phase involving reduction of [CoIII(H2L)GSH]+ by both GSH and GSH2 +. The final products are the corresponding Co(II) complex and the oxidized form of GSH, GS–SG. The kinetic data and activation parameters for the redox process are interpreted in terms of an outer-sphere electron transfer mechanism.

Item Type:Article
Source:Copyright of this article belongs to Springer-Verlag.
ID Code:97913
Deposited On:03 Jan 2014 11:52
Last Modified:09 Jul 2014 05:11

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