Understanding the Role of Second Coordination Sphere Effects on Electrochemical CO₂ Reduction with Iron Porphyrins

Enzymes achieve fast kinetics and high selectivity by carefully controlling the functional groups in the vicinity of the active site. Collectively, these peripheral groups are termed the Second Coordination Sphere (SCS). Synthetic chemists have long been inspired by the biological importance of the SCS and have demonstrated that the SCS can play an important role in a number of transformations promoted by molecular catalysts. In particular, it is well-known that the kinetics of electrochemical CO 2 reduction depend on the presence of SCS functional groups capable of proton transfer, hydrogen bonding, or electrostatic interactions. However, many aspects still remain incompletely understood, such as the p K a requirements for protic SCS groups, the positional dependence of the SCS group with respect to the active site, and the role(s) of the SCS group in the catalytic reaction mechanism. This talk will showcase various SCS modifications made to iron porphyrins and, relying on a combination of molecular synthesis, electrochemistry, spectroscopy, and computational insights, will outline the various ways that the SCS can perturb reaction mechanisms and outcomes of electrochemical CO 2 reduction.