Atropisomeric Effects of Second Coordination Spheres on Electrocatalytic CO2 Reduction

Control of the second coordination spheres of molecular catalytic systems has enhanced the catalytic efficiencies and facilitated the elucidation of catalytic mechanisms. Herein, we present the evaluation of stereoisomeric effects of a set of metal redox-innocent zinc porphyrin complexes on CO(2)reduction, including complexes containing four (ZnP4T) and one (ZnP1T) triazole units, and two atropisomers with two triazole units positioned at the same (ZnP2T-alpha alpha) and different (ZnP2T-alpha beta) sides of the zinc porphyrin framework. Kinetic study and foot-of-the-wave analysis indicated that complexes with more than one triazole unit on the same side of the porphyrin framework (ZnP4TandZnP2T-alpha alpha) display at least double maximum turnover frequency than the counterparts with a single triazole unit on the same side (ZnP1TandZnP2T-alpha beta). These results suggest the formation of a hydrogen-bonding network in the second coordination sphere that facilitates proton transfer from the hydrophilic network to the catalyst-CO(2)intermediate.