FORMATION AND DECOMPOSITION STUDY OF ELECTROCHEMICALLY-GENERATED NICKEL(III)-NOTA COMPLEXES IN AQUEOUS-SOLUTION TA(3-)=1,4,7-TRIAZACYCLONONANE-N,N'N''-TRIACETATE)

Electochemical oxidation of the nickel(II) complex at the macrocyclic ligand 1,4,7-triazacylononane-N,N',N''-triacetate (nota(3-)) in aqueou s solution yields the nickel(III) complex, which undergoes fast base-p romoted chemical decomposition. This decomposition process was studied by cyclic voltammetry, ESR acid electronic spectroscopy, and gave fir st-order kinetics relative to the nickel(III) complex. This is compati ble with intramolecular reduction:of the metal centre by the ligand, f ollowed by rapid decomposition of the radical species formed. The liga nd fragmentation process was analysed by proton NMR spectroscopy of th e electrolysed solution of the complex.