Oxidation of Cu(II) aminopolycarboxylates by carbonate radical: A flash photolysis study

Reactions of carbonate radical (CO3-.) generated by photolysis or by radiol ysis of a carbonate solution, with Cu(II) complexes of aminopolycarboxylic acids viz., Cu(II)ethylenediamine tetraacetate [Cu(II)EDTA](2-) and Cu(II)- iminodiacetate [Cu(II)IDA] were studied at pH 10.5 and ionic strength 0.2 m ol . dm(-3). Time-resolved spectroscopy and kinetics for the transients wer e studied using flash photolysis and stable products arising from the ligan d degradation of the complex were ascertained by steady-state radiolysis ex periments. From the kinetic data it is observed that CO3-. radical reacts i nitially with Cu-II-complex to form a transient intermediate having maximum absorption at 335 nm and 430 nm. From the subsequent reactions of this int ermediate it was assigned to be Cu-III, species. This Cu(III) species under goes intermolecular electron transfer with the Cu-II-complex to give a radi cal intermediate which again slowly reacts with Cu"-complex to give a long lived species containing Cu-C bond. This long lived species, however, slowl y decomposed to give glyoxalic reaction between Cu-III-complex and a suitab le donor, the one electron reduction potential for [Cu(III)EDTA](1-)/[Cu(II )EDTA](2-) and [Cu(III)IDA](+1)/Cu(II)IDA was determined.