Molecular and Biological Catalysts Coimmobilization on Electrode by Combining Diazonium Electrografting and Sequential Click Chemistry

Abstract

A generic approach has been developed for sequential heterogeneous surface modification of electrodes. The strategy, which is applicable for a wide range of functional groups, involves two main steps. In the first one, azide‐alkene bifunctionalized electrodes are obtained by electrochemical reduction of a mixture of diazonium salts generated in situ from the corresponding 4‐azidoaniline and 4‐vinylaniline. In that way, we provide reactive sites that are available for further selective functionalization in a sequential process based on ‘click reactions’, in which subsequent immobilization of the targeted molecules is achieved by the azide‐alkyne cycloaddition Huisgen reaction and alkene‐thiol coupling. Feasibility of the method has been first demonstrated for the coimmobilization of two distinct redox moieties (cobaltocenium and ferrocene) as evidenced by cyclic voltammetry and X‐ray photoelectron spectroscopy measurements. The versatility of the sequential method has then been exploited for the coimmobilization of a molecular electrocatalyst [Cp*Rh(bpy) Cl]+ and a biological catalyst, a NAD‐dependent dehydrogenase, that were proved to act in cascade in the electroenzymatic reduction of D‐fructose to D‐sorbitol. Such simple combination of diazonium chemistry and robust chemical reactions (‘click chemistry’) is promising for the environmentally friendly heterogeneous modification of electrodes with multiple chemical and biological catalysts.

Electrocatalytic Biosynthesis using a Bucky Paper Functionalized by [Cp*Rh(bpy)Cl]+ and a Renewable Enzymatic Layer

“…The electrografting on the BP electrode was achieved by running two cyclic voltammograms from 0.4 V to −0.8 V in this solution. These parameters were adapted from two previous work involving diazonium electrografting ,. After electrografting, the electrode was rinsed carefully with water and left to dry before use.…”

A post-functionalization toolbox for diazonium (electro)-grafted surfaces: review of the coupling methods

“…When the latter are biological application-oriented, chemical coupling with a redox entity constitutes the preliminary step to optimize the reaction, assess the robustness of the linkage and estimate the maximum coupling yield, since the biomolecules to be grafted are biggest than the redox species. 114,129,136,141,156 In these studies, ferrocene, which gives a reversible and stable redox signal, is commercially available, inexpensive and easily chemically functionalizable, was chosen as model molecule. These reasons also motivated the use of this redox probe to validate and better understand different concepts including functionalization of non-conventional electrodes, 132,135,140,157,158 electron transfer, 125,127,128,159 formation of more or less compact monolayers, 105,115,123,124,130,137,139 fabrication of mixed (mono)layers, 105,116,120,122,138 surface structuring, 117,126,131,133 building of dendrimer modified surfaces.…”

“…Additional spectroscopic analyzes (Raman, absorption or emission spectroscopies) have provided additional information on organic layers modified by fluorene, 148 BODIPY, 150,151 porphyrin 142 or phthalocyanin 113 derivatives. Targetted applications have also boosted the development of the latter (phthalocyanin-based surfaces), [143][144][145][146] since they are characterized, similarly to surfaces based on TEMPO 155 or metal complexes, 153,154,156,160 by good electrocatalytic properties. Immobilization of metal complexes has also been exploited for the development of molecular switches 152 or electrochemical sensors for alkylamine 85 and that of TTF for the formation of charge transfer complexes with tetracyanoquinodimethane (Fig.…”

“…The other studies, not falling into the two aforementioned categories (immobilization of redox molecules or biomolecules), relate to the modification of reactive platforms by gold nanoparticles, [169][170][171] polymers (already synthesized 172,173 or via direct growth from the surface [174][175][176] ), or other molecules like azobenzene 177 or azlactone. 178 Excluding the rare examples based on thiol-ene 156,179 or thiol-yne reactions, 180,181 click chemistry on surface consists in a reaction between an azide and an alkyne functions. Thus, two strategies can be envisaged: a coupling of an alkyne terminated target on an azide tethered surface, or a coupling of an azide derivative with an alkyne modified surface.…”

“…The first one, the most usual one, involves the chemical reduction (by L-ascorbic acid or L-sodium ascorbate) of various Cu(II) salts (generally sulfate or acetate) to form Cu(I). 114,117,118,120,[129][130][131]133,136,141,152,153,156,159,161,170,171,182 Large excess in reducing agent (molar ratios [reducing agent/Cu(II)] varying from 1 114,133 to 50 171 ) guarantees a sufficient Cu(I) concentration in the medium, even when the reaction mixture is not kept under inert atmosphere. Cu(I) can also be generated electrochemically by reduction of Cu(II) 126,167,169 or oxidation of Cu(0) (Fig.…”