Developing a Mechanistic Understanding of Molecular Electrocatalysts for CO₂ Reduction using Infrared Spectroelectrochemistry

Abstract

Review: 67 refs.

Design of a Catalytic Active Site for Electrochemical CO2 Reduction with Mn(I)-Tricarbonyl Species

“…The first reduction wave corresponds to a metal-based reduction of the Mn center, which leads to the formation of a Mn−Mn dimer. 37 In MnBr(bpy)(CO) 3 , oxidative cleavage of the metal−metal bond within the corresponding dimer is observed at −0.30 V vs SCE. 12 We similarly find an oxidative wave for this process at ca.…”

“…They reported that, on the basis of cyclic voltammetry and infrared spectroelectrochemistry investigations, a [Mn(bpy)(CO) 3 ] − intermediate serves as the active species for CO 2 reduction with manganese, which is analogous to the proposed pathway for rhenium. 37 Accordingly, we truncated the potential energy surface and considered only the transformation of as a barometer for improved design. Our theoretical investigation began by considering Mn(bpy)(CO) 3 COOH in a CO 2 -saturated acetonitrile environment.…”

Manganese Tricarbonyl Complexes with Asymmetric 2-Iminopyridine Ligands: Toward Decoupling Steric and Electronic Factors in Electrocatalytic CO2 Reduction

“…10 For some of the Re analogues, a one-electron reduced complex, [ReCl(CO) 3 (R-bpy )] was observed by IR spectroscopy and identified by the ca. 15-20 cm -1 decrease in the (CO) energy, 11,12,13 as was the five-coordinate radical [Re(CO) 3 ( t Bubpy)] by an additional 15-20 cm -1 shift .…”

“…10 For some of the Re analogues, a one-electron reduced complex, [ReCl(CO) 3 (R-bpy )] was observed by IR spectroscopy and identified by the ca. 15-20 cm -1 decrease in the (CO) energy, 11,12,13 as was the five-coordinate radical [Re(CO) 3 ( t Bubpy)] by an additional 15-20 cm -1 shift .Two mechanisms have been proposed 10,14-18 for the ultimate reduction of [Mn(CO) 3 ( -diimine)] 2 in the presence of CO 2 , which can be referred to as the anionic, and the oxidative addition 19 pathways. The anionic pathway involves reduction of the dimer [Mn(CO) 3 ( -diimine)] 2 at a more negative potential than the parent complex generating the five-coordinate anion [Mn(CO) 3 ( -diimine)] to which CO 2 coordinates and is catalyti-2 cally reduced in the presence of a Brönsted acid (the source of H + ).…”

Electrocatalytic Reduction of Carbon Dioxide by Mn(CN)(2,2′-bipyridine)(CO)3: CN Coordination Alters Mechanism

“…29,32 In any case, the proposed active species is a doubly reduced anion that possesses a vacant axial site for CO 2 coordination: [Mn(κ 2 -L)(CO) 3 ] − (c, see Scheme 1). Theoretical 38 and experimental 39,40 investigations of the mechanism suggest that oneelectron reduction of the metal center causes the axial ligand, usually a bromide ion, to dissociate. Subsequently, the neutral radical monomer dimerizes to give [Mn(κ 2 -L)(CO) 3 ] 2 (b).…”