Ligand effects of ruthenium 2,2′-bipyridine and 1,10-phenanthroline complexes on the electrochemical reduction of CO₂

Abstract

Electrochemical reduction of CO, catalysed by [RUL'(L~)(CO),]~+ [L',L2 = (bipy),, (bipy)(dmbipy), (dmbipy),, or (phen),], [Ru(phen),(CO)CI] + (phen = 1 ,lo-phenanthroline), and [RuL(CO),CI,] [ L = 2,2'-bipyridine (bipy) or 4,4'-dimethyl-2,2'-bipyridine (dmbipy)] were carried out by controlledpotential electrolysis at -1.30 V vs. saturated calomel electrode in acetonitrile-water (4: 1 , v/v), MeOH, or MeCN-MeOH (4: 1 , v/v). In acetonitrile-water (4: 1 , v/v) n o difference in activities between the catalysts was observed, however i n MeOH the amounts of carbon monoxide produced became larger than those of HC0,-upon introduction of the dmbipy ligand. This is attributed to the equilibrium constants among the reaction intermediates [RuL'(L2) (C0),l2+, [RuL1(L2)(CO)-{C(O)OH}] +, and [RuL1(L2)(CO)(C0,-)] + which become smaller o n substitution of bipy by dmbipy, because of the donor property of the CH, group.

Unexpected effect of catalyst concentration on photochemical CO2 reduction by trans(Cl)–Ru(bpy)(CO)2Cl2: new mechanistic insight into the CO/HCOO− selectivity

“…73 Further reduction of the ruthenium dimer causes dissociation of the chloride ions to give [Ru(bpy)(CO) 2 ] n . The monomeric ruthenium complex, Ru(bpy)(CO) 2 Cl 2 , also shows catalytic activity for electrochemical CO 2 reduction, 63,65,67,69 but the complex tends to form an adherent film of the polymer on the electrode during electrochemical CO 2 reduction, making it difficult to investigate the catalytic properties of the monomeric complex in detail. The photochemical CO 2 reduction catalysed by Ru(bpy)(CO) 2 Cl 2 has been reported in the presence of [Ru(bpy) 3 ] 2+ as the photosensitizer and triethanolamine (TEOA) as the electron donor, 70 in which the reaction starts when [Ru(bpy) 3 ] 2+ absorbs visible light to induce electron transfer relay from TEOA to the catalyst.…”

Photocatalytic CO2 Reduction by Periodic Mesoporous Organosilica (PMO) Containing Two Different Ruthenium Complexes as Photosensitizing and Catalytic Sites

“…[1] Alarge numbers of metal complexes have been studied as catalysts for photochemical/electrochemical CO 2 reduction. [3][4][5][6][7][8] For photocatalyticC O 2 reduction,p hotosensitizers such as [Ru(bpy) 3 ] 2 + are required. Amongt he metal complexes, trans(Cl)-[Ru(bpy)(CO) 2 Cl 2 ]( bpy:2 ,2'-bipyridine) and its derivatives are known as excellent catalysts for reducing CO 2 to carbon monoxide( CO) and/or formate (HCOO À )f rom the viewpoint of high activity and durability.…”

Photocatalytic CO 2 reduction with high turnover frequency and selectivity of formic acid formation using Ru(II) multinuclear complexes

“…Only a few photocatalysts for the selective formation of formic acid from CO 2 have been reported (3)(4)(5)(6)(7)(8). Although oligo(p-phenylenes) (3) or a mixed system of phenazine and Co cyclam (4) successfully photocatalyzed the reduction of CO 2 to formic acid, these systems cannot work with visible light.…”

“…Although oligo(p-phenylenes) (3) or a mixed system of phenazine and Co cyclam (4) successfully photocatalyzed the reduction of CO 2 to formic acid, these systems cannot work with visible light. It has been reported that ½RuðbpyÞ 2 ðCOÞ 2 2þ (bpy ¼ 2,2′-bipyridine) acted as a catalyst for reducing CO 2 (5)(6)(7)(8). Under basic conditions, a mixed system of this complex with ½RuðbpyÞ 3 2þ as a redox photosensitizer photocatalyzed the reduction of CO 2 to formic acid with high selectivity (6,8).…”