Comparative electrochemistry and electrocatalytic activities of cobalt, iron and manganese phthalocyanine complexes axially co-ordinated to mercaptopyridine self-assembled monolayer at gold electrodes

• Published in: Electrochimica acta 2006-03, Vol.51 (13), p.2669-2677
• Main Authors: Ozoemena, Kenneth I., Nyokong, Tebello
• Format: Article
• Language: English
• Subjects: Chemistry; Electrocatalysis; Electrochemistry; Exact sciences and technology; General and physical chemistry; l-Cysteine; Metallophthalocyanine-mercaptopyridine self-assembled monolayers; Miscellaneous; Study of interfaces; Thiocyanate
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2005.08.007

Comparative surface electrochemistry and electrocatalytic properties of solid ultrathin monolayer films of metallophthalocyanine (MPc) complexes of cobalt (CoPc), iron (FePc) and manganese (MnPc) self-immobilised, via axial ligation reaction, onto preformed 4-mercaptopyridine self-assembled monolayers (SAMs) on gold electrodes have been described. Surface electrochemical parameters of the modified electrodes showed that these MPc-SAMs are densely packed with flat orientations. The electrochemical, electrocatalytic and stability properties of these MPc complexes follow this order: FePc > MnPc > CoPc. This finding is remarkable as it suggests that the success of using this method of self-assembling of MPc onto gold electrode is largely dependent on the bond distance between the pyridine linker and the central metal of the MPc; the shorter the distance, the faster the co-ordination and the better the electrocatalytic properties towards l-cysteine and thiocyanate. Thus, the superiority of FePc-based SAM over those of the MnPc and CoPc, has been proposed to be the result of the more favorable axial co-ordination properties of FePc with pyridine (i.e. shorter Fe–N(pyridine) bond length.