Electrode Kinetics of the Redox Couples of Co(III/II) Complexes with Ethylenediamine-N-acetate, Iminodiacetate, and Diethylenetriamine

The electrochemical kinetic parameters of Co(edma)21+⁄0 (edma: ethylenediamine-N-acetate), Co(ida)21−⁄2− iminodiacetate), Co(dien)23+⁄2+ (dien: diethylenetriamine), Co(1,2-pn)33+⁄2+ (1,2-pn: 1,2-propanediamine), and Co(gly)30⁄1− (gly: glycinate) redox couples were determined by d.c. and normal pulse polarographic measurements as well as galvanostatic double pulse measurements. A difference in the evaluated kinetic parameters for the geometric isomers, trans(O)- and cis(O)-Co(edma)21+⁄0 and trans(N)- and cis(N)-Co(ida)21−⁄2− couples, was recognized. The values of the standard rate constant for the bis forms with dien, edma, and ida were reduced with increase in the number of replacement of amino groups in dien by carboxyl groups. The standard rate constants of the redox couples of Co(III/II) complexes with a series of bi- and tridentate polyamines and aminocarboxylates increase in proportion to the number of nitrogen donor atoms involved in the ligands.