Mechanism of Oxidation of (Meso-5, 7, 7, 12, 14, 14-Hexamethyl-1, 4, 8, 11-Tetraazacyclotetradecane)Nickel(II) by H2O Free Radicals in Aqueous Solutions. A Pulse Radiolysis Study

Avraham Meshulam, Dan Meyerstein, Haim Cohen, Rudi Van Eldik

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Abstract

The title complex NiL2+ is oxidized in aqueous solutions in the pH range 3-7 in the presence of stabilizing anions X, X = HCO2-, SO42-, and H2PO4-, by HO2· free radicals to NiIIILX2. The dependence of the rate of formation on [NiL2+] and X indicates that the H02· radical reacts with a [NiL2+] complex in the ion pair [NiL2+, X], forming the final products. The volumes of activation of the oxidation processes were measured; an analysis of the data indicates that the ion pairs involved are contact ion pairs. The results indicate that in the presence of appropriate transition-metal complexes the superoxide free radical is a potent oxidizing agent and suggest that this might cause some of the aspects of its toxicity.

Original languageEnglish
Pages (from-to)2151-2156
Number of pages6
JournalInorganic Chemistry
Volume31
Issue number11
DOIs
StatePublished - 1 Jan 1992

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