Developing optimized systems to minimizing energy input for electrocatalytically driven artificial photosynthetic processes is a key consideration in moving to a carbon neutral economy; coupling cathodic and anodic processes rationally designed to minimize wasted energy (i.e. overpotential), select for desired products, and maximize synthetic output are key objective in electrocatalytic conversions that are hampered by inherent high kinetic barriers, particularly the cathodic reaction involving carbon dioxide reduction. Reports from Fontecave have highlighted that large anodic shifts in metal- and ligand-based reduction potentials can be achieved by modifying the terminal pyridine units of 2,2’:6′,2″-terpyridine (terpy) coordinated to cobalt. Additionally, recently published work highlighting the use of functionalized aryl substituents at the 4’-position of terpy provides smaller adjustments to metal- and ligand-based reduction potentials, which correlate strongly to the Hammett parameter of the aryl-substituents’ functional group. Here we will present our preliminary findings analyzing the electrochemical and electrocatalytic reduction behavior of homoleptic complexes containing a new tridentate meridional ligand series derived from quinoline, which incorporates the design principles described above to fine-tune the complexes’ reduction potentials and will ultimately provide a template to optimizing electrocatalytic substrate reduction with these complexes.

Electrochemical behavior of homoleptic complexes of aryl substituted quinoline-derived ligands

ACS Spring 2022

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