Hangman Corroles: Efficient Synthesis and Oxygen Reaction Chemistry

Abstract

The construction of a new class of compounds--the hangman corroles--is provided efficiently by the modification of macrocyclic forming reactions from bilanes. Hangman cobalt corroles are furnished in good yields from a one-pot condensation of dipyrromethane with the aldehyde of a xanthene spacer followed by metal insertion using microwave irradiation. In high oxidation states, X-band EPR spectra and DFT calculations of cobalt corrole axially ligated by chloride are consistent with the description of a Co(III) center residing in the one-electron oxidized corrole macrocycle. These high oxidation states are likely accessed in the activation of O-O bonds. Along these lines, we show that the proton-donating group of the hangman platform works in concert with the redox properties of the corrole to enhance the catalytic activity of O-O bond activation. The hangman corroles show enhanced activity for the selective reduction of oxygen to water as compared to their unmodified counterparts. The oxygen adduct, prior to oxygen reduction, is characterized by EPR and absorption spectroscopy.

Self-Assembled Molecular Rafts at Liquid|Liquid Interfaces for Four-Electron Oxygen Reduction

“…To characterize the interfacial self-assembly, the dependence of the SSHG intensity with the fundamental input angle of polarization was also determined at the fundamental wavelength of 842 nm, 828 nm, and 848 nm for P 4 Figure 3e, f and g shows that the behavior of [P 4+ /P 4− ] is rather different from that of the isolated porphyrins. The SSHG intensity described by eq 1 has been fitted to estimate the coefficients a, b and c, see Table 2 and Figure 3e, f and g. The a coefficient is always the largest one and corresponds to the SSHG intensity collected with the fundamental beam p polarized at the interface.…”

Biological Outer-Sphere Coordination

“…Nocera and coworkers designed "hangman" porphyrins and corroles with pendant hydrogen-bonding groups that confer proton-coupled dioxygen activation activity [127,128]. This iron-mediated dioxygen activation has been extended to nonheme complexes.…”

Quantum Chemical Characterization of Water Oxidation Catalysts

“…As a result, significant recent research effort has been focused on the synthesis and characterization of WOCs based on earth-abundant metals such as cobalt and iron. In these categories, Dogutan and coworkers have recently reported the synthesis and electrocatalytic water oxidation of a cobalt-based catalyst containing a -octafluoro hangman corrole, CoH F -CO 2 H, while Ellis and coworkers have reported a series of iron(III)-centered tetraamido macrocyclic ligand (Fe III -TAML) catalysts capable of oxidizing water to molecular oxygen in the presence of an excess of sacrificial oxidant [29][30][31].…”