Voltammetric studies of gold surface modified by bis(octakis(octyloxy) phthalocyaninato) europium(III) adlayers in perchloric acid solution

Bis(octakis(octyloxy) phthalocyaninato) europium(III) (Eu[Pc(OC8H17)8]2) adlayers were self-assembled on the gold surface by means of an improved self-assembling technique. The cyclic voltammograms (CVs) of the Eu[Pc(OC8H17)8]2-modified single-crystalline and poly-crystalline gold electrodes in perchloric acid displayed two pairs of redox waves due to the successive removal or addition of electrons from or to the ligand-based orbitals. The effect of Eu[Pc(OC8H17)8]2 adlayers on the electron transfer rate at electrode/solution interface was investigated by using Fe(CN)63−/4− couple as the redox probe. The redox behavior of Eu[Pc(OC8H17)8]2 adlayers and their accelerating effect on the electron transfer are closely associated with the electronic delocalization of rare earth sandwich complexes. However, in most cases, the Eu[Pc(OC8H17)8]2 adlayers were found to have inhibition role to complicated electrochemical reactions taking place on the gold surface, such as the gold substrate oxidation, the electrochemical reduction of oxygen, the electrochemical oxidation of ascorbic acid (Vitamin C) and the underpotential deposition (UPD) of silver.