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

Research Overview

Former Resnick Postdoctoral Scholar, Matthew Welborn, was a member of a research team that investigated a series of cobalt aminopyridine complexes to examine the effects of electronic modifications on CO₂ reduction catalysis. The results of this study are summarized in the publication, "Electronically Modified Cobalt Aminopyridine Complexes Reveal an Orthogonal Axis for Catalytic Optimization for CO₂ Reduction". Combining experimental and theoretical work, the team revealed that the CO₂ reduction catalysts may be further optimized to tune catalytic activity, through an orthogonal synthetic space via ligand-derived electronic modulation of the metal center.

Scientific Achievement

We synthesized and investigated a family of molecular cobalt catalysts for electrochemical CO₂ reduction.

Significance and Impact

Hydrogen-bonding and electronic inductive effects via chemical substitution can be utilized as orthogonal dials for catalytic tuning.

Incorporation of hydrogen bond donors into the framework of cobalt aminopyridine macrocycles has been demonstrated to increase the rate of reaction for electrochemical CO₂ reduction. Now further work has shown that electronic inductive effects imparted from chemical modification can influence catalysis through an orthogonal axis. Combined experimental and theoretical work suggests these inductive effects play a role in the basicity of critical reaction intermediates in the catalytic cycle. Credit: Reprinted with permission from Inorganic Chemistry. DOI:10.1021/acs.inorgchem.0c02086 (2020) American Chemical Society.

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Incorporation of hydrogen bond donors into the framework of cobalt aminopyridine macrocycles has been demonstrated to increase the rate of reaction for electrochemical CO₂ reduction. Now further work has shown that electronic inductive effects imparted from chemical modification can influence catalysis through an orthogonal axis. Combined experimental and theoretical work suggests these inductive effects play a role in the basicity of critical reaction intermediates in the catalytic cycle. Credit: Reprinted with permission from Inorganic Chemistry. DOI:10.1021/acs.inorgchem.0c02086 (2020) American Chemical Society.

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Technical Details

• Combined experimental and theoretical work finds electronic modification of the catalytic framework influences the basicity of critical Co-CO₂(H) intermediates.
• The most electrochemically active species via (i_cat/i_p) is predicted to have the most favorable Co-CO₂ proton binding energies.
• Hammett analysis is consistent with positive charge build up in the transition state (r < 0).

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

Contact: Thomas F. Miller, III