Abstract
The rhenium complex Re(bpy)(CO)3Cl (1, bpy = 2,2′-bipyridine) catalyzes CO2 reduction to CO in mixtures containing triethanolamine (TEOA) as a sacrificial reductant. The mechanism of this reaction under photocatalytic conditions remains to be fully characterized. Here, we report the competitive carbon kinetic isotope effects (13C KIEs) on photocatalytic CO2 reduction by 1 and analyze the results of experimental measurements by comparing with computed KIEs via density functional theory (DFT) calculations as a means of formulating a chemical mechanism and illustrating the utility of this approach. The 13C KIEs, k(12C)/k(13C), in acetonitrile (ACN) and dimethylformamide (DMF) were determined to be 1.0718 ± 0.0036 and 1.0685 ± 0.0075, respectively. When [Ru(bpy)3]Cl2 is added to the reaction mixture in acetonitrile as a photosensitizer, the reduction of CO2 exhibited a 13C KIE = 1.0703 ± 0.0043. These values are consistent with the calculated isotope effect of CO2 binding to the one-electron reduced [ReI(bpy•-)(CO)3] species. The findings reported here provide strong evidence that the reactions in the two different solvents have the same first irreversible step and proceed with similar reactive intermediates upon reduction. Theoretically, we found that the major contribution for the large 13C isotope effects comes from a dominant zero-point energy (ZPE) term. These results lay the groundwork for combined experimental and theoretical approaches for analysis of competitive isotope effects toward understanding CO2 reduction catalyzed by other complexes.
| Original language | English |
|---|---|
| Pages (from-to) | 5473-5481 |
| Number of pages | 9 |
| Journal | ACS Catalysis |
| Volume | 6 |
| Issue number | 8 |
| DOIs | |
| Publication status | Published - Aug 5 2016 |
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Keywords
- CO reduction
- homogeneous catalysis
- isotope effects
- isotopic discrimination
- photocatalysis
ASJC Scopus subject areas
- Catalysis
Cite this
Mechanism of photocatalytic reduction of CO2 by Re(bpy)(CO)3Cl from differences in carbon isotope discrimination. / Schneider, Taylor W.; Ertem, Mehmed Z.; Muckerman, James; Angeles-Boza, Alfredo M.
In: ACS Catalysis, Vol. 6, No. 8, 05.08.2016, p. 5473-5481.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Mechanism of photocatalytic reduction of CO2 by Re(bpy)(CO)3Cl from differences in carbon isotope discrimination
AU - Schneider, Taylor W.
AU - Ertem, Mehmed Z.
AU - Muckerman, James
AU - Angeles-Boza, Alfredo M.
PY - 2016/8/5
Y1 - 2016/8/5
N2 - The rhenium complex Re(bpy)(CO)3Cl (1, bpy = 2,2′-bipyridine) catalyzes CO2 reduction to CO in mixtures containing triethanolamine (TEOA) as a sacrificial reductant. The mechanism of this reaction under photocatalytic conditions remains to be fully characterized. Here, we report the competitive carbon kinetic isotope effects (13C KIEs) on photocatalytic CO2 reduction by 1 and analyze the results of experimental measurements by comparing with computed KIEs via density functional theory (DFT) calculations as a means of formulating a chemical mechanism and illustrating the utility of this approach. The 13C KIEs, k(12C)/k(13C), in acetonitrile (ACN) and dimethylformamide (DMF) were determined to be 1.0718 ± 0.0036 and 1.0685 ± 0.0075, respectively. When [Ru(bpy)3]Cl2 is added to the reaction mixture in acetonitrile as a photosensitizer, the reduction of CO2 exhibited a 13C KIE = 1.0703 ± 0.0043. These values are consistent with the calculated isotope effect of CO2 binding to the one-electron reduced [ReI(bpy•-)(CO)3] species. The findings reported here provide strong evidence that the reactions in the two different solvents have the same first irreversible step and proceed with similar reactive intermediates upon reduction. Theoretically, we found that the major contribution for the large 13C isotope effects comes from a dominant zero-point energy (ZPE) term. These results lay the groundwork for combined experimental and theoretical approaches for analysis of competitive isotope effects toward understanding CO2 reduction catalyzed by other complexes.
AB - The rhenium complex Re(bpy)(CO)3Cl (1, bpy = 2,2′-bipyridine) catalyzes CO2 reduction to CO in mixtures containing triethanolamine (TEOA) as a sacrificial reductant. The mechanism of this reaction under photocatalytic conditions remains to be fully characterized. Here, we report the competitive carbon kinetic isotope effects (13C KIEs) on photocatalytic CO2 reduction by 1 and analyze the results of experimental measurements by comparing with computed KIEs via density functional theory (DFT) calculations as a means of formulating a chemical mechanism and illustrating the utility of this approach. The 13C KIEs, k(12C)/k(13C), in acetonitrile (ACN) and dimethylformamide (DMF) were determined to be 1.0718 ± 0.0036 and 1.0685 ± 0.0075, respectively. When [Ru(bpy)3]Cl2 is added to the reaction mixture in acetonitrile as a photosensitizer, the reduction of CO2 exhibited a 13C KIE = 1.0703 ± 0.0043. These values are consistent with the calculated isotope effect of CO2 binding to the one-electron reduced [ReI(bpy•-)(CO)3] species. The findings reported here provide strong evidence that the reactions in the two different solvents have the same first irreversible step and proceed with similar reactive intermediates upon reduction. Theoretically, we found that the major contribution for the large 13C isotope effects comes from a dominant zero-point energy (ZPE) term. These results lay the groundwork for combined experimental and theoretical approaches for analysis of competitive isotope effects toward understanding CO2 reduction catalyzed by other complexes.
KW - CO reduction
KW - homogeneous catalysis
KW - isotope effects
KW - isotopic discrimination
KW - photocatalysis
UR - http://www.scopus.com/inward/record.url?scp=84981313875&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84981313875&partnerID=8YFLogxK
U2 - 10.1021/acscatal.6b01208
DO - 10.1021/acscatal.6b01208
M3 - Article
VL - 6
SP - 5473
EP - 5481
JO - ACS Catalysis
JF - ACS Catalysis
SN - 2155-5435
IS - 8
ER -