Re(I) NHC Complexes for Electrocatalytic Conversion of CO2

Area of Science:

• Organometallic Chemistry
• Catalysis
• Electrochemistry

Background:

• Modular ligand design around N-heterocyclic carbene (NHC) building blocks offers a versatile method for tuning metal complex electronic properties.
• Recent advances in transition-metal-free synthesis facilitate the construction of complex organic molecules.

Purpose of the Study:

• To synthesize novel methylbenzimidazolium-pyridine and methylbenzimidazolium-pyrimidine proligands.
• To chelate these proligands with a rhenium precursor to form new Re(I) NHC complexes.
• To investigate the electrocatalytic activity of these complexes in CO2 reduction.

Main Methods:

• Synthesis of methylbenzimidazolium-pyridine and methylbenzimidazolium-pyrimidine proligands.
• Chelation with ReCl(CO)5 to form Re(I) NHC complexes.
• Electrochemical studies including cyclic voltammetry and spectroelectrochemistry.
• Density functional theory (DFT) computations.
• Chemical reduction experiments.

Main Results:

• High-yield synthesis of the target proligands and subsequent formation of Re(I) NHC complexes.
• Demonstrated electrocatalytic activity of the Re(I) NHC complexes for the two-electron reduction of CO2.
• Observed Faradaic efficiency for CO formation exceeding 60%, with minimal H2 and formic acid production.
• Comparative electrochemical data against established bipyridine complexes.

Conclusions:

• The synthesized Re(I) NHC complexes are effective electrocatalysts for CO2 reduction to CO.
• The modular ligand design strategy provides a tunable platform for developing efficient CO2 reduction catalysts.
• The study provides insights into the mechanism of CO2 reduction mediated by these complexes.