Structural and Spectroscopic Evidence for a Side-on Fe(III)-Superoxo Complex Featuring Discrete O-O Bond Distances

Hung Ruei Pan, Hsin Jou Chen, Zong Han Wu, Pu Ge, Shengfa Ye, Gene Hsiang Lee, Hua Fen Hsu

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

The O-O bond length is often used as a structural indicator to determine the valence states of bound O2 ligands in biological metal-dioxygen intermediates and related biomimetic complexes. Here, we report very distinct O-O bond lengths found for three crystallographic forms (1.229(4), 1.330(4), 1.387(2) Å at 100 K) of a side-on iron-dioxygen species. Despite their different O-O bond distances, all forms possess the same electronic structure of Fe(III)-O2•-, as evidenced by their indistinguishable spectroscopic features. Density functional theory and ab initio calculations, which successfully reproduce spectroscopic parameters, predict a flat potential energy surface of an η2-O2 motif binding to the iron center regarding the O-O distance. Therefore, the discrete O-O bond lengths observed likely arise from differential intermolecular interactions in the second coordination sphere. The work suggests that the O-O distance is not a reliable benchmark to unequivocally identify the valence state of O2 ligands for metal-dioxygen species in O2-utilizing metalloproteins and synthetic complexes.

Original languageEnglish
Pages (from-to)1389-1398
Number of pages10
JournalJACS Au
Volume1
Issue number9
DOIs
Publication statusPublished - 2021 Sept 27

All Science Journal Classification (ASJC) codes

  • Analytical Chemistry
  • Chemistry (miscellaneous)
  • Physical and Theoretical Chemistry
  • Organic Chemistry

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