Biological systems such as the [NiFe] CO-dehydrogenase enzyme can selectively reduce CO2 to CO through a catalytic process featuring a bifunctional activation of CO2 and an additional stabilization by hydrogen bonding interactions between the substrate and functional groups in the first, second and outer coordination spheres. In order to mimic the essential functions and structural features of this enzyme, we have developed a new type of catalysts M[bpyMe(ImMe)](CO)3Cl]+ (M= Re or Mn) by incorporating a charged, redox-active imidazolium moiety in the secondary coordination sphere of the conventional rhenium/manganese bipyridine electrocatalysts. In this work, electronic structure calculations have been performed in order to study the reaction mechanism for CO2-to-CO conversion using M[bpyMe(ImMe)](CO)3Cl]+ (M = Re, Mn) in the presence of water as a proton source. We propose that the incorporation of the imidazolium ligand in the secondary coordination sphere can not only shift the reduction potentials positively, but also tune the catalytic pathways through an intramolecular as well as an intermolecular interaction with the proton source. Notably, to characterize the transition states and activation energy barriers during the protonation steps, the proton source (e.g. 5H2O cluster) has been explicitly computed and an optimized conjugate acid/base couple was used as the reference to discuss the protonation steps.

Mechanistic study for the reduction of CO2 to CO using M[bpyMe(ImMe)](CO)3Cl]+ complexes: Probing the role of the imidazolium moiety in the secondary coordination sphere

2019 Spring National Meeting

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