On-surface cross-coupling methods for the construction of modified electrode assemblies with tailored morphologies

Abstract

Controlling the molecular topology of electrode–catalyst interfaces is a critical factor in engineering devices with specific electron transport kinetics and catalytic efficiencies. As such, the development of rational methods for the modular construction of tailorable electrode surfaces with robust molecular wires (MWs) exhibiting well-defined molecular topologies, conductivities and morphologies is critical to the evolution and implementation of electrochemical arrays for sensing and catalysis. In response to this need, we have established modular on-surface Sonogashira and Glaser cross-coupling processes to synthetically install arrays of ferrocene-capped MWs onto electrochemically functionalized surfaces. These methods are of comparable convenience and efficiency to more commonly employed Huisgen methods. Furthermore, unlike the Huisgen reaction, this new surface functionalization chemistry generates modified electrodes that do not contain unwanted ancillary metal binding sites, while allowing the bridge between the ferrocenyl moiety and electrode surface to be synthetically tailored. Electrochemical and surface analytical characterization of these platforms demonstrate that the linker topology and connectivity influences the ferrocene redox potential and the kinetics of charge transport at the interface.

Efficient Reduction of CO2 to CO with High Current Density Using in Situ or ex Situ Prepared Bi-Based Materials

“…16−18 Although recent work has shown that immobilization of a cobalt porphyrin onto conducting diamond 19 or nickel cyclam onto a conducting poly(allylamine) support 20 can promote the electrocatalytic production of CO, these heterogeneous architectures do not currently display technologically relevant current densities (fast kinetics) for CO 2 conversion applications.…”

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

“…119 Immobilization of this molecule on a reactive platform is also a good way to compare the effectiveness of different functionalization methods. 118,121,134 Even if more than half of the studies based on the immobilization of redox probes by click chemistry rely on the use of ferrocene, other less conventional redox probes have made it possible to widen the field of study and applications of electroactive 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.…”

“…Whether they are carried out in one direction or another (azide surface and alkyne in solution, or the opposite), the couplings are made under similar operating conditions. Cupper(I) is always used as a reaction catalyst (directly added, 134,148,162,173,175 or formed in situ from cupper(II) and a reducing agent 85,105,[113][114][115]119,[121][122][123][124]127,128,132,135,139,140,142,147,149,157,158,160,[163][164][165][166]168,177,178 or electrochemically generated 137,176 ). The most common option relies on the combined use of copper(II) sulfate and ascorbic acid (or sodium ascorbate, usually in excess) as reducing agent.…”

“…116,122 The use of smaller protective groups (trimethylsilyl or triethylsilyl) resulted in a decrease in size of the pinholes (formed on the surface after deprotection of the silyl groups), thus leading to an increase in the surface coverage of redox species immobilized by post-functionalization. 123 This approach have been exploited by other groups to develop an amperometric biosensor by covalent immobilization of a HRP azide on an ethynyl monolayer-modified electrode, 166 to anchor an azide-functionalized initiator, allowing the controlled radical polymerization of N-isopropylacrylamide 176 or to prepare monolayer platforms for the surface functionalization by Sonogashira, 121,184 Glaser coupling, 121 or Huisgen 1,3 dipolar cycloaddition. 139,184 In fine, the results obtained starting from monolayers (prepared by deprotection of silyl groups) or multilayers both highlight surface coverages around few 10 À10 mol cm À2 , excluding major differences in terms of interfacial reactivity.…”

“…In order to optimize the catalysts and other reaction conditions, two interesting different strategies have been conducted. A fist approach, implemented by Rosenthal, Watson et al, 121 relies on the optimization of the analogue homogeneous reaction, that is, a free-diffusing homologue of the grafted molecule is reacted with the same coupling partner employed in the interfacial process (Fig. 15).…”