Synthesis of Transition Metal Complexes Bearing Redox-Active Schiff Base Ligands and Their Electrocatalytic Activity

Abstract

Herein, we report two complementary strategies, electronic and geometric tuning, for designing CO2 electroreduction catalysts that exploit the electron reservoir properties of a Schiff base derived imino bipyridine (Imbpy) ligand. The electronically tuned W(Imbpy)(CO)3 complex shows CO2 dependent electrochemical behavior under CO2 saturated conditions, with a reduction at − 2.18 V vs. Fc+/0 that is shifted positively by 320 mV relative to a representative W bipyridine complexes, consistent with Imbpy facilitating CO2 activation. In the geometrically tuned Fe(bis-Imbpy) complex, intentional backbone strain promotes the mechanism where protonation facilitates open coordination sites, giving rise to a distinct catalytic wave at − 1.63 V vs. Fc+/0 in the presence of 2,2,2-trifluoroethanol (TFE). Together, these results suggest a design principle in which Imbpy’s electronic advantages are combined with targeted structural control to tune CO2 binding and reduction. The mechanistic picture proposed here motivates future single-crystal X-ray diffraction and DFT studies.