Abstract

Tetrapyrrolic macrocycles, such as porphyrin, consisted of four pyrrole units bonded by different bridges, for example methene in the case of porphyrins and azamethene in the case of phthalocyanines [1]. These ligands can complex metal ion transition and the synthesized metallocomplexes are extremely stable [2, 3]. While some metalloporphyrins constitute the redox center of naturally occurring proteins, like heme in hemoglobin, metallophthalocyanines are purely synthetic molecules. The (electro) chemical properties of MN4 complexes have been widely studied and have been particularly used for the catalysis of several electrochemical reactions in homogeneous solutions [4]. It was shown that the electrochemical properties of a given macrocycle could be tuned via the attachment of specific chemical groups on the ligand macrocyte. For several practical applications, it is, however, interesting to use immobilized catalysts, notably to recover or regenerate easily the catalyst and avoid separation steps between electrolysis products and catalysts. The modification of electrode materials with MN4 complexes has opened the way to a wide variety of applications, going from energy to sensing fields. MN4 complexes have thus been used to design molecular electrode materials, to be used as electrocatalysts for electrochemical reactions such as oxygen electroreduction or for small molecules electro-oxidation [5, 6]. MN4-based electrodes have also been designed for the detection of small analytes of biological interest, such as nitric oxide, nitrite and thiols. Recently, the discovery of nanomaterials such as carbon nanotubes (CNTs) with exceptional electronic properties has triggered research oriented toward the development of hybrid materials [7, 8]. The concept is to combine the properties of MN4 and nanomaterials with synergetic effects, to get enhanced electrocatalytic properties. This should improve the performances of the obtained electrode materials for the conception of electrochemical sensors. This chapter describes the development and use of modified electrodes with a focus on metalloporphyrins and MPcs for electrocatalysis and electroanalysis of thiol oxidation. Firstly, the main preparation and characterization ways of MN4- modified electrode are presented, as well as the development of new immobilization strategies. The recent development of hybrid electrode materials combining MN4 macrocycles and nanoobjects are also described, with emphasis on their electrochemical properties. Finally, the main examples of development MN4-modified electrodes for the electroanalysis of thiols are commented.