Metal-Ligand Cooperativity via Exchange Coupling Promotes Iron- Catalyzed Electrochemical CO 2 Reduction at Low Overpotentials.

Autor: Derrick JS; Department of Chemistry, University of California, Berkeley, California 94720, United States.; Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States., Loipersberger M; Department of Chemistry, University of California, Berkeley, California 94720, United States., Chatterjee R; Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States., Iovan DA; Department of Chemistry, University of California, Berkeley, California 94720, United States., Smith PT; Department of Chemistry, University of California, Berkeley, California 94720, United States.; Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States., Chakarawet K; Department of Chemistry, University of California, Berkeley, California 94720, United States., Yano J; Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States., Long JR; Department of Chemistry, University of California, Berkeley, California 94720, United States.; Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, United States.; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States., Head-Gordon M; Department of Chemistry, University of California, Berkeley, California 94720, United States.; Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States., Chang CJ; Department of Chemistry, University of California, Berkeley, California 94720, United States.; Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.; Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, United States.
Jazyk: angličtina
Zdroj: Journal of the American Chemical Society [J Am Chem Soc] 2020 Dec 02; Vol. 142 (48), pp. 20489-20501. Date of Electronic Publication: 2020 Nov 18.
DOI: 10.1021/jacs.0c10664
Abstrakt: Biological and heterogeneous catalysts for the electrochemical CO 2 reduction reaction (CO 2 RR) often exhibit a high degree of electronic delocalization that serves to minimize overpotential and maximize selectivity over the hydrogen evolution reaction (HER). Here, we report a molecular iron(II) system that captures this design concept in a homogeneous setting through the use of a redox non-innocent terpyridine-based pentapyridine ligand (tpyPY2Me). As a result of strong metal-ligand exchange coupling between the Fe(II) center and ligand, [Fe(tpyPY2Me)] 2+ exhibits redox behavior at potentials 640 mV more positive than the isostructural [Zn(tpyPY2Me)] 2+ analog containing the redox-inactive Zn(II) ion. This shift in redox potential is attributed to the requirement for both an open-shell metal ion and a redox non-innocent ligand. The metal-ligand cooperativity in [Fe(tpyPY2Me)] 2+ drives the electrochemical reduction of CO 2 to CO at low overpotentials with high selectivity for CO 2 RR (>90%) and turnover frequencies of 100 000 s -1 with no degradation over 20 h. The decrease in the thermodynamic barrier engendered by this coupling also enables homogeneous CO 2 reduction catalysis in water without compromising selectivity or rates. Synthesis of the two-electron reduction product, [Fe(tpyPY2Me)] 0 , and characterization by X-ray crystallography, Mössbauer spectroscopy, X-ray absorption spectroscopy (XAS), variable temperature NMR, and density functional theory (DFT) calculations, support assignment of an open-shell singlet electronic structure that maintains a formal Fe(II) oxidation state with a doubly reduced ligand system. This work provides a starting point for the design of systems that exploit metal-ligand cooperativity for electrocatalysis where the electrochemical potential of redox non-innocent ligands can be tuned through secondary metal-dependent interactions.
Databáze: MEDLINE
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