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A series of molecular Mn catalysts featuring aniline groups in the second‐coordination sphere has been developed for electrochemical and photochemical CO₂reduction. The arylamine moieties were installed at the 6 position of 2,2’‐bipyridine (bpy) to generate a family of isomers in which the primary amine is located at theortho‐(1‐Mn),meta‐(2‐Mn), orpara‐site (3‐Mn) of the aniline ring. The proximity of the second‐sphere functionality to the active site is a critical factor in determining catalytic performance. Catalyst1‐Mn, possessing the shortest distance between the amine and the active site, significantly outperformed the rest of the series and exhibited a 9‐fold improvement in turnover frequency relative to parent catalyst Mn(bpy)(CO)₃Br (901 vs. 102 s⁻¹, respectively) at 150 mV lower overpotential. The electrocatalysts operated with high faradaic efficiencies (≥70 %) for CO evolution using trifluoroethanol as a proton source. Notably, under photocatalytic conditions, a concentration‐dependent shift in product selectivity from CO (at high [catalyst]) to HCO₂H (at low [catalyst]) was observed with turnover numbers up to 4760 for formic acid and high selectivities for reduced carbon products.

 

Two NNN pincer complexes of Cu( ii ) and Ni( ii ) with BPI Me − [BPI Me − = 1,3-bis((6-methylpyridin-2-yl)imino)isoindolin-2-ide] have been prepared and characterized structurally, spectroscopically, and electrochemically. The single crystal structures of the two complexes confirmed their distorted trigonal bipyramidal geometry attained by three equatorial N-atoms from the ligand and two axially positioned water molecules to give [Cu(BPI Me )(H 2 O) 2 ]ClO 4 and [Ni(BPI Me )(H 2 O) 2 ]ClO 4 . Electrochemical studies of Cu( ii ) and Ni( ii ) complexes have been performed in acetonitrile to identify metal-based and ligand-based redox activity. When subjected to a saturated CO 2 atmosphere, both complexes displayed catalytic activity for the reduction of CO 2 with the Cu( ii ) complex displaying higher activity than the Ni( ii ) analogue. However, both complexes were shown to decompose into catalytically active heterogeneous materials on the electrode surface over extended reductive electrolysis periods. Surface analysis of these materials using energy dispersive spectroscopy as well as their physical appearance suggests the reductive deposition of copper and nickel metal on the electrode surface. Electrocatalysis and decomposition are proposed to be triggered by ligand reduction, where complex stability is believed to be tied to fluxional ligand coordination in the reduced state.