Issue 26, 2007
From the journal:

Physical Chemistry Chemical Physics

Tuning the redox properties of metalloporphyrin- and metallophthalocyanine-based molecular electrodes for the highest electrocatalytic activity in the oxidation of thiols

Fethi Bedioui,a   Sophie Griveau,a   Tebello Nyokong,b   A. John Appleby,c   Claudia A. Caro,d   Miguel Gulppi,†e   Gonzalo Ochoae  and  José H. Zagal*e  

* Corresponding authors

a INSERM, U 640, CNRS, UMR 8151, École Nationale Supérieure de Chimie de Paris, René Descartes Paris 5, Chemical and Genetic Pharmacology Laboratory, Paris, France

b Department of Chemistry, Rhodes University, Grahamstown, South Africa

c Center for Electrochemical Systems and Hydrogen Research 3402 Texas A & M University, College Station, TX, USA

d Facultad de Ciencias, Departamento de Ciencias Básicas, Universidad del Bío-Bío, Chillán, Chile

e Departamento de Química de los Materiales, Facultad de Química y Biología, Universidad de Santiago de Chile, Casilla 40, Correo 33 Santiago, Chile

Abstract

In this work we discuss different approaches for achieving electrodes modified with N4 macrocyclic complexes for the catalysis of the electrochemical oxidation of thiols. These approaches involve adsorption, electropolymerization and molecular anchoring using self assembled monolayers. We also discuss the parameters that determine the reactivity of these complexes. Catalytic activity is associated with the nature of the central metal, redox potentials and Hammett parameters of substituents on the ligand. Correlations between catalytic activity (log i at constant E) and the redox potential of catalysts for complexes of Cr, Mn, Fe, Co, Ni and Cu are linear with an increase of activity for more positive redox potentials. For a great variety complexes bearing the same metal center (Co) correlations between log i and Eo′ of the Co(II)/Co(I) couple have the shape of an unsymmetric volcano. This indicates that the potential of the Co(II)/Co(I) couple can be tuned using the appropiate ligand to achieve maximum catalytic activity. Maximum activity probably corresponds to a ΔG of adsorption of the thiol on the Co center equal to zero, and to a coverage of active sites by the thiol equal to 0.5.

Graphical abstract: Tuning the redox properties of metalloporphyrin- and metallophthalocyanine-based molecular electrodes for the highest electrocatalytic activity in the oxidation of thiols

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Article information

DOI
https://doi.org/10.1039/B618767F
Article type
Invited Article
Submitted
22 Dec 2006
Accepted
14 Mar 2007
First published
11 Apr 2007

Phys. Chem. Chem. Phys., 2007,9, 3383-3396

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Tuning the redox properties of metalloporphyrin- and metallophthalocyanine-based molecular electrodes for the highest electrocatalytic activity in the oxidation of thiols

F. Bedioui, S. Griveau, T. Nyokong, A. John Appleby, C. A. Caro, M. Gulppi, G. Ochoa and J. H. Zagal, Phys. Chem. Chem. Phys., 2007, 9, 3383 DOI: 10.1039/B618767F

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