Charged Macromolecular Rhenium Bipyridine Catalysts with Tunable CO Reduction Potentials.

A series of polymeric frameworks with functional assemblies were designed to alter the catalytic activity of covalently bound Re electrocatalysts. Norbornenyl polymers containing positively charged quaternary ammonium salts, neutral phenyl, or negatively charged trifluoroborate groups were end-labelled with a Re fac-tricarbonyl bipyridine electrocatalyst via cross metathesis. Electrochemical studies in acetonitrile under an inert atmosphere and with saturated CO indicate that the quaternary ammonium polymers exhibit a significantly lower potential for CO reduction to CO (ca.

Tuning Electron Delocalization and Transfer Rates in Mixed-Valent Ru3O Complexes through "Push-Pull" Effects.

Electron transfer rates in a series of oxo-centered triruthenium clusters featuring an extended aromatic ancillary ligand of the type [Ru3(OAc)6(μ3-O)(CO)(L)(pep)], where L = 4-cyanopyridine (cpy), pyridine (py), or 4-(dimethylamino)pyridine (dmap) and pep = 4-(phenylethynyl)pyridine were investigated. The electron self-exchange rate constants for the 0/- couple were determined by (1)H NMR line broadening experiments and found to range from 4.3 to 9.

Improving the Efficiency and Activity of Electrocatalysts for the Reduction of CO2 through Supramolecular Assembly with Amino Acid-Modified Ligands.

The use of hydrogen-bonding interactions to direct the noncovalent assembly of a Re-based bimetallic supramolecular electrocatalyst containing either tyrosine or phenylalanine residues is reported. Computational modeling and spectroelectrochemical characterization indicate that under catalytic conditions the phenol residues of tyrosine can act both as pendant proton sources and participate in the structural assembly of the bimetallic active species. As a result, an increased rate of catalysis is observed experimentally for the reductive disproportionation of CO2 to CO and CO3(2-) by a tyrosine-modified complex in comparison to a control complex containing phenylalanine residues.

Supramolecular assembly promotes the electrocatalytic reduction of carbon dioxide by Re(I) bipyridine catalysts at a lower overpotential.

The addition of methyl acetamidomethyl groups at the 4,4'-positions of a 2,2'-bipyridyl ligand is found to enhance the rate of a bimolecular reduction mechanism of CO2 by Re(I) fac-tricarbonyl chloride complexes. Electrochemical studies, spectroelectrochemical measurements, and molecular dynamics simulations indicate that these methyl acetamidomethyl groups promote the formation of a hydrogen-bonded dimer. This supramolecular complex catalyzes the reductive disproportionation of CO2 to CO and CO3(2-) at a lower overpotential (ca.