Sum frequency generation spectroscopy (SFG) and calculations of SFG spectra based on density functional theory are combined to elucidate the orientation of two Re(R-2,2′-bipyridine)(CO)3Cl (R = 4-cyano or 4,4′-dicyano) electrocatalysts when adsorbed on conductive gold surfaces. We find that the electrocatalysts lean on the Au surface to orient the plane of the bipyridine ligand at 63° relative to the surface normal. While the weak binding of the complexes to the gold surface precluded the ability to perform surface immobilized catalysis, homogeneous electrochemical experiments show that the molecular catalysts are active toward the reduction of CO2 to CO and carbonate in the triply reduced state (TOF of 13.3 and 7.2 s-1 for the doubly and singly substituted complexes, respectively). These findings demonstrate the capabilities of the approach of including rigorous spectroscopic and theoretical methods for revealing the conformation and orientation of CO2 reduction catalysts bound to electrode surfaces, which are critical considerations for redox state transitions and catalytic turnover.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films