Rhenium bipyridine catalysts with hydrogen bonding pendant amines for CO₂ reduction

Abstract

Rhenium tricarbonyl bipyridine complexes modified with pendant secondary and tertiary amines in the 6- and 6′-positions were synthesized and characterized.

Manganese and Rhenium Tricarbonyl Complexes Equipped with Proton Relays in the Electrochemical CO2 Reduction Reaction

“…16 and 18. [39,46,47] Two other complexes with acidic protons in equatorial positions of the ligand have been investigated (Figure 4, Figure 5). 19, with an α-diimine quinoline aldoxime ligand, was inactive.…”

“…A series of complexes with NH(Me) and NMe 2 units in 6,(6')‐position showed a moderate activities in the electrochemical CO 2 ‐to‐CO conversion in MeCN/TFE (TFE = trifluoroethanol, Figure 4). [ 46 ] The redox potential of the initial reduction is shifted in all complexes to more reducing potentials than in 1 Cl due to the electron donating character of the NR(Me) groups. After initial reduction of 15 and 16 , the radical dimerises, whereas 17 and 18 do not follow this pathway.…”

Electro‐ and Photochemical Reduction of CO2 by Molecular Manganese Catalysts: Exploring the Positional Effect of Second‐Sphere Hydrogen‐Bond Donors

“…Their simple ligand design and high selectivity for the two‐electron reduction of CO 2 to CO or HCO 2 H continue to garner attention. Researchers have also modified the second‐coordination sphere of these systems in order to achieve lower overpotentials and enhanced activities for electrochemical and light‐driven catalysis [8–18] . In this strategy, functional groups are appended to the ligand framework to introduce specific noncovalent, secondary interactions near the active site of catalysts that serve to stabilize intermediates or promote key steps (i. e., proton transfer) in the catalytic cycle [19,20] …”

“…Researchers have also modified the second-coordination sphere of these systems in order to achieve lower overpotentials and enhanced activities for electrochemical and light-driven catalysis. [8][9][10][11][12][13][14][15][16][17][18] In this strategy, functional groups are appended to the ligand framework to introduce specific noncovalent, secondary interactions near the active site of catalysts that serve to stabilize intermediates or promote key steps (i. e., proton transfer) in the catalytic cycle. [19,20] Since the initial report of electrocatalytic CO 2 reduction by fac-Mn(bpy)(CO) 3 Br (MnBpy), [8] a number of Mn catalysts have been reported with modified second-coordination sphere environments that have improved the efficiency and/or altered the product selectivity relative to the parent system.…”

An NADH-Inspired Redox Mediator Strategy to Promote Second-Sphere Electron and Proton Transfer for Cooperative Electrochemical CO2 Reduction Catalyzed by Iron Porphyrin

“…[16][17][18][19][20][21][22][23][24] Beyond this platform and other privileged primary coordination sphere motifs, approaches to enhance CO 2 reduction catalysis with secondary coordination sphere pendants have largely focused on improving the delivery of protons using intramolecular proton relays and/or stabilization of metal-bound CO 2 intermediates via hydrogen bonding. [17][18][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] Additionally, reduced CO 2 intermediates can be captured by inter/intra-molecular Lewis acid cations [40][41][42] or intramolecular charge-compensation moieties, such as ammonium 21,43 or imidazolium groups. [44][45][46] In addition to proton control, strategies for facilitating electron delivery from the secondary coordination sphere for CO 2 reduction have also been explored.…”