jz9b03897_si_002.cif (3.47 MB)
Double Hangman Iron Porphyrin and the Effect of Electrostatic Nonbonding Interactions on Carbon Dioxide Reduction
dataset
posted on 2020-02-24, 13:51 authored by Charles
G. Margarit, Naomi G. Asimow, Miguel I. Gonzalez, Daniel G. NoceraHangman
porphyrins influence the reaction rates of small molecule
activation by positioning a functional group in the secondary coordination
sphere of the metal center. Electrocatalysis by hangman porphyrins
has examined only one face modification of the macrocycle with a hanging
group, thus allowing for circumvention of secondary sphere effects
by reaction of the small molecule on the opposite face of the hangman
cleft. We now report the synthesis and characterization of a double
hangman Fe porphyrin in which both faces of the macrocycle are modified
with a hanging group. With this double hangman architecture, we are
able to unequivocally examine the role of electrostatic interactions
on the carbon dioxide reduction reaction (CO2RR) and show
that CO2RR rates are significantly attenuated, consistent
with the initial reduction of CO2 to generate the anion,
whose binding is diminished within the negatively charged carboxylic
groups of the hangman cleft. The results demonstrate the pronounced
role that nonbonding electrostatic interactions may play in CO2RR and highlight the need to manage deleterious electrostatic
interactions during catalytic turnover.