A five-coordinate heme dioxygen adduct isolated within a metal-organic framework

John S. Anderson, Audrey T. Gallagher, Jarad A. Mason, T. David Harris*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

60 Scopus citations

Abstract

The porphyrinic metal-organic framework (MOF) PCN-224 is metalated with FeII to yield a 4-coordinate ferrous heme-containing compound. The heme center binds O2 at -78 °C to give a 5-coordinate heme-O2 complex. For the first time, this elusive species is structurally characterized, revealing an FeIII center coordinated to superoxide via an end-on, η1 linkage. Mössbauer spectroscopy supports the structural observations and indicates the presence of a low-spin electronic configuration for FeIII. Finally, variable-temperature O2 adsorption data enable quantification of the Fe-O2 interaction, providing a binding enthalpy of -34(4) kJ/mol. This value is nearly half of that observed for comparable 6-coordinate, imidazole-bound heme-O2 complexes, a difference that further illustrates the importance of axial ligands in biological heme-mediated O2 transport and storage. These results demonstrate the ability of a MOF, by virtue of its rigid solid-state structure, to enable isolation and thorough characterization of a species that can only be observed transiently in molecular form.

Original languageEnglish (US)
Pages (from-to)16489-16492
Number of pages4
JournalJournal of the American Chemical Society
Volume136
Issue number47
DOIs
StatePublished - Nov 26 2014

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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