Rj. Mortimer et Js. Weightman, ELECTROCHEMICAL STUDIES OF N-PHENYLAZA-15-CROWN-5, Journal of electroanalytical chemistry [1992], 418(1-2), 1996, pp. 1-7
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.