Covalent attachment of [Ni(alkynyl-cyclam)]²⁺ catalysts to glassy carbon electrodes

Abstract

Surface modification of glassy carbon electrodes (GCEs) with molecular electrocatalysts is an important step towards developing more efficient heterogeneous CO2 reduction materials. Here, we report direct anodic electrografting of [Ni(alkynyl-cyclam)]2+ catalysts to the surface of GCEs in one simple step using inexpensive earth-abundant chemicals. When modified, these electrodes show reversible electrochemistry in organic solvents with zero peak-to-peak separations (ΔE = 0) and non-diffusive I (V) profiles that are typical for heterogeneous redox materials. CPE of these electrodes showed enhanced formation of H2 gas relative to CO compared to homogeneous catalysts.

Strong Electronic Coupling of Graphene Nanoribbons onto Basal Plane of Glassy Carbon Electrode

“…A more favorable way to introduce catalytic moieties to graphitic electrodes involves post-pyrolysis modifications of carbon edge and basal sites with well-defined molecular motifs. For this purpose, several creative chemical methods have been developed to immobilize molecular catalysts to the carbonbased surfaces using covalent bonds, [4][5][6][7][8][9][10][11] − stacking [12][13][14][15][16][17][18][19] and electrostatic interactions. 20,21 Carbon edge sites are often modified covalently using 'click' chemistry 4,7 or aryl radical intermediates formed from diazonium salts.…”

Anodic Oxidation of Ethynylferrocene Derivatives in Homogeneous Solution and Following Anodic Deposition onto Glassy Carbon Electrodes

“…New directions and applications of anodic ethynyl deposition methods have already begun to appear. These include the depositions of a nickel cyclam complex that is an effective catalyst for CO 2 reduction, using the direct oxidation method, [5] and several calixarenes anchored through multiple ethynyl groups, using the lithio activation method. [6] Both Sheridan et al [4] and Jouikov and Simonet [7] have shown that the direct oxidation method may be successful even when the leaving group of a terminal ethynyl moiety is SiMe 3 + .…”

“…Recently it has been shown that radical‐based electrografting processes are effective in preparing chemically modified electrodes to which molecules are covalently attached through an ethynyl group . We have previously described an assortment of methods whereby metallocenes derivatized at a cyclopentadienyl ring with a terminal ethynyl group can be covalently attached to carbon surfaces .…”

“…Recently it has been shown that radical-based electrografting processes are effective in preparing chemically modified electrodes to which molecules are covalently attached through an ethynyl group. [1][2][3][4][5][6][7] We have previously described an assortment of methods whereby metallocenes derivatized at a cyclopentadienyl ring with a terminal ethynyl group can be covalently attached to carbon surfaces. [1][2][3][4] The present paper augments that work by providing several new examples of glassy carbon (GC) electrodes that have been modified with ethynyl-attached ferrocene derivatives that differ in the number and types of bonds between the metal center and the ethynyl group.…”

Copper(II) Complexes of N-Propargyl Cyclam Ligands Reveal a Range of Coordination Modes and Colours, and Unexpected Reactivity

“…The recently reported surface modification of glassy carbon electrodes for CO2 reduction with a series of [Ni(alkynyl-cyclam)] 2+ complexes, serves as an isolated example. 25 We have ongoing interests in N-propargyl cyclams as precursors for Cu(I)-catalysed azide-alkyne Huisgen 'click' reactions, which enable the introduction of more complex pendant functionality as in 4 and 5 above, [26][27][28] a strategy that has also been employed in a number of other metal chelating systems. 29…”