Electrocatalytic oxidation of NADH at the self-assembled monolayer of nickel(II) macrocycle on gold electrode

Electroactive self-assembled monolayers (SAMs) of macrocyclic Ni(II) comple x (1) were fabricated on gold electrode and its electrochemistry has been s tudied in different supporting electrolytes. Substantial stabilization of t ervalent nickel and a significant negative shift of formal potential of the Ni3+/2+ couple have been observed when the supporting electrolyte is chang ed from nitrate to phosphate. Coordination of supporting electrolyte anion with the Ni(III) complex shifts the formal potential and thus tervalent nic kel is stabilized. SAM of 1 electrode shows an excellent electrocatalytic a ctivity towards the oxidation of NADH in aqueous NaNO3 solution, whereas it scarcely catalyzes the oxidation of NADH in aqueous phosphate buffer solut ion. The electrocatalytic oxidation of NADH in Na2SO4 solution is less effi cient than that in NaNO3 solution. The anion-dependent electrocatalysis has been discussed on the basis of the difference in the coordinating ability of the anions with the tervalent nickel centers. Steady-state current has b een measured for the oxidation of NADH and it was proportional to the conce ntration of NADH. (C) 2000 Elsevier Science B.V. All rights reserved.