Structural and Spectroscopic Characterization of a High-Spin {FeNO}6 Complex with an Iron(IV)-NO- Electronic Structure

Amy L. Speelman, Bo Zhang, Carsten Krebs, Nicolai Lehnert

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34 Scopus citations


Although the interaction of low-spin ferric complexes with nitric oxide has been well studied, examples of stable high-spin ferric nitrosyls (such as those that could be expected to form at typical non-heme iron sites in biology) are extremely rare. Using the TMG3tren co-ligand, we have prepared a high-spin ferric NO adduct ({FeNO}6 complex) via electrochemical or chemical oxidation of the corresponding high-spin ferrous NO {FeNO}7 complex. The {FeNO}6 compound is characterized by UV/Visible and IR spectroelectrochemistry, Mössbauer and NMR spectroscopy, X-ray crystallography, and DFT calculations. The data show that its electronic structure is best described as a high-spin iron(IV) center bound to a triplet NO- ligand with a very covalent iron-NO bond. This finding demonstrates that this high-spin iron nitrosyl compound undergoes iron-centered redox chemistry, leading to fundamentally different properties than corresponding low-spin compounds, which undergo NO-centered redox transformations. One-electron oxidation of the high-spin ferrous nitrosyl complex [Fe(TMG3tren)(NO)]2+ yields a rare high-spin (S=1) ferric NO adduct ({FeNO}6). Spectroscopic investigations and DFT calculations indicate that this species has an FeIV-NO- electronic structure. This finding demonstrates that high-spin non-heme iron nitrosyl complexes have fundamentally different redox behavior compared to corresponding low-spin heme systems.

Original languageEnglish (US)
Pages (from-to)6685-6688
Number of pages4
JournalAngewandte Chemie - International Edition
Issue number23
StatePublished - Jun 1 2016

All Science Journal Classification (ASJC) codes

  • Catalysis
  • General Chemistry


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