ELECTROCHEMICAL STUDIES OF N-PHENYLAZA-15-CROWN-5

The electrochemical oxidation of the ionophoric macrocycle N-phenylaza -15-crown-5 has been investigated in acetonitrile. For a 1 mmol dm(-3) solution of N-phenylaza-15-crown-5, cyclic voltammetry revealed that the mechanism followed that of N,N-dimethylaniline, the initial one-el ectron irreversible oxidation leading to dimerisation at the para posi tion. Constant potential electrolysis in the presence of pyridine allo wed stoichiometric electrogeneration of the dimer in solution; subsequ ent cyclic voltammetry showing two reversible one-electron redox waves (E(f) = 0.57 and 0.70 V vs. SSCE) to the dimer radical cation and qui noidal dication respectively. Cyclic voltammetric investigations revea led that both the N-phenylaza-15-crown-5 irreversible oxidation wave a nd the reversible N-phenylaza-15-crown-5 neutral dimer-to-radical cati on redox wave were sensitive to the binding of sodium and magnesium gu est cations at the macrocyclic coordinating sites. Thus shifts to more positive potentials were found on titrimetric addition of these catio ns, the higher charge:radius ratio of the magnesium cation guest produ cing the most dramatic effect.