Atropisomeric Hydrogen Bonding Control for CO 2 Binding and Enhancement of Electrocatalytic Reduction at Iron Porphyrins

Philipp Gotico (1) , Loïc Roupnel (1) , Regis Guillot , Marie Sircoglou (1) , Winfried Leibl , Zakaria Halime (1) , Ally Aukauloo

1 ICMMO - Institut de Chimie Moléculaire et des Matériaux d'Orsay

The manipulation of the second coordination sphere for improving the electrocatalytic CO2 reduction has led to amazing breakthroughs with hydrogen bonding, local proton source, or electrostatic effects. We have developed two atropisomers of an iron porphyrin complex holding two urea functions acting as multiple hydrogen bonding tweezers to lock the metal bound CO2 in a similar fashion found in the carbon monoxide dehydrogenase (CODH) enzyme. We found that the  topological isomer with the two urea groups on the same side of the porphyrin platform provides a stronger binding affinity to tether the incoming CO2 substrate in comparison to the  disposition. However, the electrocatalytic activity of the  atropisomer outperforms its congener with one of the highest reported turnover frequency at low overpotential. The strong H/D KIE observed for the system indicates the existence of a tight water hydrogen bonding network for proton delivery which is disrupted upon addition of exogenous acid source. While the small H/D KIE for the  isomer and the enhanced electrocatalytic performance upon addition of stronger acid pertain the free access of protons to the bound CO2 on the opposite side of the urea arm.

Mots clés: Urea, carbon dioxide reduction, hydrogen bonding, iron porphyrin, second coordination

Domaines: Chimie

Philipp Gotico, Loïc Roupnel, Regis Guillot, Marie Sircoglou, Winfried Leibl, et al.. Atropisomeric Hydrogen Bonding Control for CO 2 Binding and Enhancement of Electrocatalytic Reduction at Iron Porphyrins. Angewandte Chemie International Edition, 2020, ⟨10.1002/anie.202010859⟩. ⟨hal-03016806⟩