Formation and decomposition study of electrochemically-generated nickel(III)–nota complexes in aqueous solution (nota3–= 1,4,7-triazacyclononane-N,N′,N″-triacetate)

Abstract

Electrochemical oxidation of the nickel(II) complex of the macrocyclic ligand 1,4,7-triazacyclononane-N,N′,N″-triacetate (nota^3–) in aqueous solution yields the nickel(III) complex, which undergoes fast base-promoted chemical decomposition. This decomposition process was studied by cyclic voltammetry, ESR and electronic spectroscopy, and gave first-order kinetics relative to the nickel(III) complex. This is compatible with intramolecular reduction of the metal centre by the ligand, followed by rapid decomposition of the radical species formed. The ligand fragmentation process was analysed by proton NMR spectroscopy of the electrolysed solution of the complex.