Electrochemical behaviour of isomers of a tetraazamacrocyclic Ni(II) complex in solutions saturated with argon, CO and CO 2

Abstract

Isomers of [Ni(CRH)] 2+ have been isolated and studied by d.c. and a.c. voltammetry on mercury electrodes in aqueous solution. The configurational isomers of [Ni(CRH)] 2+ were found to differ in their stability in the solution and the isomerization process was monitored voltammetrically. The adsorptivity of the isomer A on mercury electrodes was found to be stronger than that of the isomer B, while no differences were seen for the adsorbed Ni(I) complexes. The solution resident [Ni(CRH)] + complexes are more labile than the corresponding Ni(II) compounds, hence upon reduction the isomer B undergoes fast transformation into the more stable isomer A. The electroreduction of [Ni(CRH)] 2+ in the presence of CO and CO 2 is described and the influence of the isomeric form used in the processes is discussed.