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Title: Positional effects of second-sphere amide pendants on electrochemical CO 2 reduction catalyzed by iron porphyrins

The development of catalysts for electrochemical reduction of carbon dioxide offers an attractive approach to transforming this greenhouse gas into value-added carbon products with sustainable energy input. Inspired by natural bioinorganic systems that feature precisely positioned hydrogen-bond donors in the secondary coordination sphere to direct chemical transformations occurring at redox-active metal centers, we now report the design, synthesis, and characterization of a series of iron tetraphenylporphyrin (Fe-TPP) derivatives bearing amide pendants at various positions at the periphery of the metal core. Proper positioning of the amide pendants greatly affects the electrocatalytic activity for carbon dioxide reduction to carbon monoxide. In particular, derivatives bearing proximal and distal amide pendants on the ortho position of the phenyl ring exhibit significantly larger turnover frequencies (TOF) compared to the analogous para-functionalized amide isomers or unfunctionalized Fe-TPP. Analysis of TOF as a function of catalyst standard reduction potential enables first-sphere electronic effects to be disentangled from second-sphere through-space interactions, suggesting that the ortho-functionalized porphyrins can utilize the latter second-sphere property to promote CO 2 reduction. Indeed, the distally-functionalized ortho-amide isomer shows a significantly larger through-space interaction than its proximal ortho-amide analogue. These data establish that proper positioning of secondary coordination sphere groups is an effectivemore » design element for breaking electronic scaling relationships that are often observed in electrochemical CO 2 reduction.The development of catalysts for electrochemical reduction of carbon dioxide offers an attractive approach to transforming this greenhouse gas into value-added carbon products with sustainable energy input.« less
Authors:
 [1] ;  [1] ;  [2] ;  [1] ; ORCiD logo [1]
  1. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Univ. of California, Berkeley, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Chemical Science
Additional Journal Information:
Journal Volume: 9; Journal Issue: 11; Related Information: © 2018 The Royal Society of Chemistry.; Journal ID: ISSN 2041-6520
Publisher:
Royal Society of Chemistry
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1465425

Nichols, Eva M., Derrick, Jeffrey S., Nistanaki, Sepand K., Smith, Peter T., and Chang, Christopher J.. Positional effects of second-sphere amide pendants on electrochemical CO2 reduction catalyzed by iron porphyrins. United States: N. p., Web. doi:10.1039/c7sc04682k.
Nichols, Eva M., Derrick, Jeffrey S., Nistanaki, Sepand K., Smith, Peter T., & Chang, Christopher J.. Positional effects of second-sphere amide pendants on electrochemical CO2 reduction catalyzed by iron porphyrins. United States. doi:10.1039/c7sc04682k.
Nichols, Eva M., Derrick, Jeffrey S., Nistanaki, Sepand K., Smith, Peter T., and Chang, Christopher J.. 2018. "Positional effects of second-sphere amide pendants on electrochemical CO2 reduction catalyzed by iron porphyrins". United States. doi:10.1039/c7sc04682k. https://www.osti.gov/servlets/purl/1465425.
@article{osti_1465425,
title = {Positional effects of second-sphere amide pendants on electrochemical CO2 reduction catalyzed by iron porphyrins},
author = {Nichols, Eva M. and Derrick, Jeffrey S. and Nistanaki, Sepand K. and Smith, Peter T. and Chang, Christopher J.},
abstractNote = {The development of catalysts for electrochemical reduction of carbon dioxide offers an attractive approach to transforming this greenhouse gas into value-added carbon products with sustainable energy input. Inspired by natural bioinorganic systems that feature precisely positioned hydrogen-bond donors in the secondary coordination sphere to direct chemical transformations occurring at redox-active metal centers, we now report the design, synthesis, and characterization of a series of iron tetraphenylporphyrin (Fe-TPP) derivatives bearing amide pendants at various positions at the periphery of the metal core. Proper positioning of the amide pendants greatly affects the electrocatalytic activity for carbon dioxide reduction to carbon monoxide. In particular, derivatives bearing proximal and distal amide pendants on the ortho position of the phenyl ring exhibit significantly larger turnover frequencies (TOF) compared to the analogous para-functionalized amide isomers or unfunctionalized Fe-TPP. Analysis of TOF as a function of catalyst standard reduction potential enables first-sphere electronic effects to be disentangled from second-sphere through-space interactions, suggesting that the ortho-functionalized porphyrins can utilize the latter second-sphere property to promote CO2 reduction. Indeed, the distally-functionalized ortho-amide isomer shows a significantly larger through-space interaction than its proximal ortho-amide analogue. These data establish that proper positioning of secondary coordination sphere groups is an effective design element for breaking electronic scaling relationships that are often observed in electrochemical CO2 reduction.The development of catalysts for electrochemical reduction of carbon dioxide offers an attractive approach to transforming this greenhouse gas into value-added carbon products with sustainable energy input.},
doi = {10.1039/c7sc04682k},
journal = {Chemical Science},
number = 11,
volume = 9,
place = {United States},
year = {2018},
month = {2}
}

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