Elucidating the mechanism of photochemical CO2 reduction to CO using a cyanide-bridged di-manganese complex

Kailyn Y. Cohen; Adam Reinhold; Rebecca Evans; Tia S. Lee; Hsin Ya Kuo; Delaan G. Nedd; Gregory D. Scholes; Andrew B. Bocarsly

doi:10.1039/d2dt02506j

Elucidating the mechanism of photochemical CO₂ reduction to CO using a cyanide-bridged di-manganese complex

Kailyn Y. Cohen, Adam Reinhold, Rebecca Evans, Tia S. Lee, Hsin Ya Kuo, Delaan G. Nedd, Gregory D. Scholes, Andrew B. Bocarsly

Princeton University

Research output: Contribution to journal › Article › peer-review

Abstract

The complex, [{[Mn(bpy)(CO)₃]₂}(μ-CN)]⁺ (Mn2CN+), has previously been shown to photochemically reduce CO₂ to CO. The detailed mechanism behind its reactivity was not elucidated. Herein, the photoevolution of this reaction is studied in acetonitrile (MeCN) using IR and UV-vis spectroscopy. Samples were excited into the Mn^I → π* bpy metal-to-ligand charge transfer (MLCT) absorption band triggering CO loss, and rapid MeCN solvent ligation at the open coordination site. It is concluded that this process occurs selectively at the Mn axial ligation site that is trans to the C-end of the bridging cyanide. Upon further photolysis, the metal-metal bonded dimeric species, [(CO)₃(bpy)Mn-Mn(bpy)(CO)₃] (Mn-Mn) is observed to form under anaerobic conditions. The presence of this dimeric species coincides with the observation of CO production. When oxygen is present, CO₂ photoreduction does not occur, which is attributed to the inability of Mn2CN+ to convert to the metal-metal bonded dimer. Photolysis experiments, where the Mn-Mn dimer is formed photochemically under argon first and then exposed to CO₂, reveal that it is the radical species, [Mn(bpy)(CO)₃^˙] (Mn˙), that interacts with the CO₂. Since the presence of Mn-Mn and light is required for CO production, [Mn(bpy)(CO)₃˙] is proposed to be a photochemical reagent for the transformation of CO₂ to CO.

Original language	American English
Pages (from-to)	17203-17215
Number of pages	13
Journal	Dalton Transactions
Volume	51
Issue number	45
DOIs	https://doi.org/10.1039/d2dt02506j
State	Published - Oct 31 2022

ASJC Scopus subject areas

Inorganic Chemistry

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10.1039/d2dt02506j

Cite this

@article{91ae90292b454126a0bb36d3c820319e,

title = "Elucidating the mechanism of photochemical CO2 reduction to CO using a cyanide-bridged di-manganese complex",

abstract = "The complex, [{[Mn(bpy)(CO)3]2}(μ-CN)]+ (Mn2CN+), has previously been shown to photochemically reduce CO2 to CO. The detailed mechanism behind its reactivity was not elucidated. Herein, the photoevolution of this reaction is studied in acetonitrile (MeCN) using IR and UV-vis spectroscopy. Samples were excited into the MnI → π* bpy metal-to-ligand charge transfer (MLCT) absorption band triggering CO loss, and rapid MeCN solvent ligation at the open coordination site. It is concluded that this process occurs selectively at the Mn axial ligation site that is trans to the C-end of the bridging cyanide. Upon further photolysis, the metal-metal bonded dimeric species, [(CO)3(bpy)Mn-Mn(bpy)(CO)3] (Mn-Mn) is observed to form under anaerobic conditions. The presence of this dimeric species coincides with the observation of CO production. When oxygen is present, CO2 photoreduction does not occur, which is attributed to the inability of Mn2CN+ to convert to the metal-metal bonded dimer. Photolysis experiments, where the Mn-Mn dimer is formed photochemically under argon first and then exposed to CO2, reveal that it is the radical species, [Mn(bpy)(CO)3˙] (Mn˙), that interacts with the CO2. Since the presence of Mn-Mn and light is required for CO production, [Mn(bpy)(CO)3˙] is proposed to be a photochemical reagent for the transformation of CO2 to CO.",

author = "Cohen, {Kailyn Y.} and Adam Reinhold and Rebecca Evans and Lee, {Tia S.} and Kuo, {Hsin Ya} and Nedd, {Delaan G.} and Scholes, {Gregory D.} and Bocarsly, {Andrew B.}",

note = "Publisher Copyright: {\textcopyright} 2022 The Royal Society of Chemistry.",

year = "2022",

month = oct,

day = "31",

doi = "10.1039/d2dt02506j",

language = "American English",

volume = "51",

pages = "17203--17215",

journal = "Dalton Transactions",

issn = "1477-9226",

publisher = "Royal Society of Chemistry",

number = "45",

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TY - JOUR

T1 - Elucidating the mechanism of photochemical CO2 reduction to CO using a cyanide-bridged di-manganese complex

AU - Cohen, Kailyn Y.

AU - Reinhold, Adam

AU - Evans, Rebecca

AU - Lee, Tia S.

AU - Kuo, Hsin Ya

AU - Nedd, Delaan G.

AU - Scholes, Gregory D.

AU - Bocarsly, Andrew B.

PY - 2022/10/31

Y1 - 2022/10/31

N2 - The complex, [{[Mn(bpy)(CO)3]2}(μ-CN)]+ (Mn2CN+), has previously been shown to photochemically reduce CO2 to CO. The detailed mechanism behind its reactivity was not elucidated. Herein, the photoevolution of this reaction is studied in acetonitrile (MeCN) using IR and UV-vis spectroscopy. Samples were excited into the MnI → π* bpy metal-to-ligand charge transfer (MLCT) absorption band triggering CO loss, and rapid MeCN solvent ligation at the open coordination site. It is concluded that this process occurs selectively at the Mn axial ligation site that is trans to the C-end of the bridging cyanide. Upon further photolysis, the metal-metal bonded dimeric species, [(CO)3(bpy)Mn-Mn(bpy)(CO)3] (Mn-Mn) is observed to form under anaerobic conditions. The presence of this dimeric species coincides with the observation of CO production. When oxygen is present, CO2 photoreduction does not occur, which is attributed to the inability of Mn2CN+ to convert to the metal-metal bonded dimer. Photolysis experiments, where the Mn-Mn dimer is formed photochemically under argon first and then exposed to CO2, reveal that it is the radical species, [Mn(bpy)(CO)3˙] (Mn˙), that interacts with the CO2. Since the presence of Mn-Mn and light is required for CO production, [Mn(bpy)(CO)3˙] is proposed to be a photochemical reagent for the transformation of CO2 to CO.

AB - The complex, [{[Mn(bpy)(CO)3]2}(μ-CN)]+ (Mn2CN+), has previously been shown to photochemically reduce CO2 to CO. The detailed mechanism behind its reactivity was not elucidated. Herein, the photoevolution of this reaction is studied in acetonitrile (MeCN) using IR and UV-vis spectroscopy. Samples were excited into the MnI → π* bpy metal-to-ligand charge transfer (MLCT) absorption band triggering CO loss, and rapid MeCN solvent ligation at the open coordination site. It is concluded that this process occurs selectively at the Mn axial ligation site that is trans to the C-end of the bridging cyanide. Upon further photolysis, the metal-metal bonded dimeric species, [(CO)3(bpy)Mn-Mn(bpy)(CO)3] (Mn-Mn) is observed to form under anaerobic conditions. The presence of this dimeric species coincides with the observation of CO production. When oxygen is present, CO2 photoreduction does not occur, which is attributed to the inability of Mn2CN+ to convert to the metal-metal bonded dimer. Photolysis experiments, where the Mn-Mn dimer is formed photochemically under argon first and then exposed to CO2, reveal that it is the radical species, [Mn(bpy)(CO)3˙] (Mn˙), that interacts with the CO2. Since the presence of Mn-Mn and light is required for CO production, [Mn(bpy)(CO)3˙] is proposed to be a photochemical reagent for the transformation of CO2 to CO.

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DO - 10.1039/d2dt02506j

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JO - Dalton Transactions

JF - Dalton Transactions

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