Trivalent Copper. II. A Pulse Radiolytic Study of the Formation and Decomposition of Amino Complexes

The effect of amino ligands on the radiolytic induced formation and decomposition of trivalent copper complexes was studied. The spectra of the Cu(III) complexes with ammonia, ethylenediamine, and different amino acids weee measured. The specific rates of oxidation of Cu(NH₃)₄²⁺ by. NH₂ radicals and the complexes of Cu²⁺ with ethylenediamine and different amino acids by -OH radicals were determined. The Cu^III(NH₃)_n complex decomposes via a second-order reaction. The Cu^III(en)₂ complex also decomposes via a second-order reaction. The specific rate of the latter reaction increases with increasing pH from 2k = 5.5×10⁵ M^-1 sec^-1 at pH 5.8 to 2k = 3.9 × 10⁷ M^-1 sec^-1 at pH 11.6. It is suggested that this increase is due to the formation of. OH radicals as an intermediate in the decomposition reaction in alkaline solutions. All the amino acid complexes of Cu(III) decompose via a first-order reaction with a specific rate of (1-8)×10³ sec^-1. It is suggested that the first step in the latter reaction is an intramolecular electron transfer from the carboxylic group to the central copper atom. The specific rate of the reaction Cu(III)_aq + Cu^IIgly→Cu_aq²⁺ + Cu^IIIgly was measured: k = 8.1 × 107 M^-1 sec^-1.