The fixation of CO2 to reduced carbon compounds of higher energy will tremendously impact both the economy and the environment. One strategy is to use sunlight to convert CO2 and H2O into value-added products, whereby energy is stored in chemical bonds and used as needed. Here, we employ computational methods in collaboration with experimentalists to understand the electronic structure and reactivity for CO2-to-CO conversion using [Re[bpyMe(ImMe)](CO)3Cl]+ (1+) in water, and compare its reactivity to [Re[bpyMe(ImMe2)](CO)3Cl]+ (2+) and [Re[bpyMe(ImMe4)](CO)3Cl]+ (3+), and probe the role of imidazolium moieties in the secondary coordination sphere. Our results indicate that the imidazolium moieties stabilize the Re-CO2 adduct and facilitate the C-O cleavage through intermolecular hydrogen-bonding interactions. Furthermore, our calculations imply that the strongest hydrogen-bonding interactions at the C2 position in 1+ contribute to the faster reaction rate observed experimentally related to 2+. More significantly, the use of the energy span model demonstrates that the turnover frequency-determining transition state (TDTS) corresponds to the formation of the Re-CO2 adduct, contrasting with the manganese analogs in which the C-O bond cleavage step is the TDTS.

Computational study for CO2-to-CO conversion over proton reduction using [Re[bpyMe(Im-R)](CO)3Cl]+ (R = Me, Me2, and Me4) electrocatalysts and comparison with the manganese analogs

ACS Spring 2022

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