Direct Grafting of Free‐Base meso‐Triarylporphyrins on Electrode Materials through Diazonium Reduction: Reversible Zinc(II) Metallation of the Resulting Materials

Abstract

Electroreduction of free base meso-diazonium-triarylporphyrins, generated in situ from their corresponding meso-aminotriarylporphyrin precursors, leads to the formation of ac ovalently graftedp orphyrin film. In this new material, contrary to recently published results, the free base porphyrin core is directly bondedt ot he surface, that is, without any spacers uch as phenylf ragments. These thin films are characterizedb yc yclic voltammetry (CV), UV/Vis absorption spectroscopy and water angle contact. The electrochemical response is in agreement with amultilayer structure. Efficient and reversible zinc metallation of the immobilized porphyrin units is readily achieved openingt he door to numerous applicationsi ns ensing and electrocatalysis.

Introducing Molecular Functionalities within High Surface Area Nanostructured ITO Electrodes through Diazonium Electrografting

“…Electrochemical surface functionalization of GLAD‐ITO electrodes was achieved by multiple reductive cyclic voltammetry (CV) scans in a quiet or stirred acetonitrile solution (Figure S1) of the free‐base porphyrin diazonium salt (generated in‐situ beforehand by addition of NaNO 2 and trifluoroacetic acid to 1 mM H 2 (PDTP)‐NH 2 , see Experimental Section) …”

“…This strategy has been widely used for the covalent modification of planar electrodes of different conductive materials, including metal oxide surfaces such as ITO, but it has never been explored for the modification of 3D transparent mesoporous metal oxide films and in particular 3D mesoporous films of ITO. The purpose of the present work is to fill this gap by investigating the electrochemical grafting of high surface area nanostructured ITO electrodes by an in‐situ generated meso‐triaryl free‐base porphyrin diazonium salt [H 2 (PDTP)‐N 2 + ], a surface functionalization strategy that was previously validated at standard planar electrodes . As a redox‐active chromophore, the grafted porphyrin has the merit of allowing quantitative analysis of the modified 3D electrodes not only by electrochemistry but also using various complementary spectroscopic techniques.…”

“…With this methodology, electrochemically‐generated aryl radicals form covalent bonds with the electrode surface, and fairly good control over the quantity of grafted molecules can be obtained via adjustment of the applied potential, appropriate selection of the grafting time and variation of the diazonium salt concentration in solution . This strategy has been widely used for the covalent modification of planar electrodes of different conductive materials, including metal oxide surfaces such as ITO, but it has never been explored for the modification of 3D transparent mesoporous metal oxide films and in particular 3D mesoporous films of ITO. The purpose of the present work is to fill this gap by investigating the electrochemical grafting of high surface area nanostructured ITO electrodes by an in‐situ generated meso‐triaryl free‐base porphyrin diazonium salt [H 2 (PDTP)‐N 2 + ], a surface functionalization strategy that was previously validated at standard planar electrodes .…”

“…Electrode functionalization was performed in a conventional three‐electrode amber glass cell under argon and at room temperature according to the literature . The auxiliary electrode was a platinum wire and the reference electrode was KCl‐saturated calomel (SCE).…”

Robust electrografted interfaces on metal oxides for electrocatalysis – an in situ spectroelectrochemical study

“…27 More recently, the electrografting of diazonium salts has been demonstrated on metal oxides, and it has been proposed that phenyl radical species (which are formed during the electrografting reaction) form covalent M-O-C bonds at the interface of the oxide. 28,29 Despite this, few examples exist where metal oxide materials have been functionalised in this way, including TiO2, [29][30][31] indium tin oxide (ITO), 24,[31][32][33][34] and fluorine-doped tin oxide (FTO). 35 Moreover, the stability of diazonium-derived interfaces on metal oxides has not been addressed so far; an aspect which is crucial for robust interface development.…”