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Electronically Modified Cobalt Aminopyridine Complexes Reveal an Orthogonal Axis for Catalytic Optimization for CO₂ Reduction

Chapovetsky, Alon and Liu, Jeffrey J. and Welborn, Matthew and Luna, John M. and Do, Thomas and Haiges, Ralf and Miller, Thomas F., III and Marinescu, Smaranda C. (2020) Electronically Modified Cobalt Aminopyridine Complexes Reveal an Orthogonal Axis for Catalytic Optimization for CO₂ Reduction. Inorganic Chemistry, 59 (18). pp. 13709-13718. ISSN 0020-1669. doi:10.1021/acs.inorgchem.0c02086.

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The design of effective electrocatalysts for carbon dioxide reduction requires understanding the mechanistic underpinnings governing the binding, reduction, and protonation of CO₂. A critical aspect to understanding and tuning these factors for optimal catalysis revolves around controlling the electronic environments of the primary and secondary coordination sphere. Herein we report a series of para-substituted cobalt aminopyridine macrocyclic catalysts 2–4 capable of carrying out the electrochemical reduction of CO₂ to CO. Under catalytic conditions, complexes 2–4, as well as the unsubstituted cobalt aminopyridine complex 1, exhibit i_(cat)/i_p values ranging from 144 to 781. Complexes 2 and 4 exhibit a pronounced precatalytic wave suggestive of an ECEC mechanism. A Hammett analysis reveals that ligand modifications with electron-donating groups enhance catalysis (ρ < 0), indicative of positive charge buildup in the transition state. This trend also extends to the Co^(I/0) potential, where complexes possessing more negative E(CoI/0) reductions exhibit greater i_(cat)/i_p values. The reported modifications offer a synthetic lever to tune catalytic activity, orthogonal to our previous study of the role of pendant hydrogen bond donors.

Item Type:Article
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URLURL TypeDescription
Chapovetsky, Alon0000-0001-8095-8830
Liu, Jeffrey J.0000-0003-2147-6449
Haiges, Ralf0000-0003-4151-3593
Miller, Thomas F., III0000-0002-1882-5380
Marinescu, Smaranda C.0000-0003-2106-8971
Additional Information:© 2020 American Chemical Society. Received: July 14, 2020; Published: August 31, 2020. The research was primarily supported by the National Science Foundation (NSF) under the CAREER Award CHE-1555387 (experimental studies) and the Chemistry of Life Processes Program CHE-1611581 (theoretical studies). S.C.M. acknowledges additional support from the Alfred P. Sloan Foundation through a Sloan research fellowship, the University of Southern California (USC), and the USC Women in Science and Engineering program. This material is based upon work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993. This research used resources of the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility supported by the DOE Office of Science under contract DE-AC02-05CH11231. M.W. thanks the Resnick Sustainability Institute for a postdoctoral fellowship. We thank Alfred Sattelberger for helpful discussions. Accession Codes: CCDC 2016095–2016096 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via, or by emailing, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033. Author Contributions: The manuscript was written through contributions of all authors. The authors declare no competing financial interest.
Group:JCAP, Resnick Sustainability Institute
Funding AgencyGrant Number
Alfred P. Sloan FoundationUNSPECIFIED
University of Southern CaliforniaUNSPECIFIED
Department of Energy (DOE)DE-SC0004993
Department of Energy (DOE)DE-AC02-05CH11231
Resnick Sustainability InstituteUNSPECIFIED
Issue or Number:18
Record Number:CaltechAUTHORS:20200901-095615539
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Official Citation:Electronically Modified Cobalt Aminopyridine Complexes Reveal an Orthogonal Axis for Catalytic Optimization for CO2 Reduction. Alon Chapovetsky, Jeffrey J. Liu, Matthew Welborn, John M. Luna, Thomas Do, Ralf Haiges, Thomas F. Miller III, and Smaranda C. Marinescu. Inorganic Chemistry 2020 59 (18), 13709-13718; DOI: 10.1021/acs.inorgchem.0c02086
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105197
Deposited By: Tony Diaz
Deposited On:08 Sep 2020 19:44
Last Modified:16 Nov 2021 18:40

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