Non-heme High-Spin {FeNO}6-8 Complexes: One Ligand Platform Can Do It All

Amy L. Speelman, Corey J. White, Bo Zhang, E. Ercan Alp, Jiyong Zhao, Michael Hu, Carsten Krebs, James Penner-Hahn, Nicolai Lehnert

Research output: Contribution to journalArticle

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Abstract

Heme and non-heme iron-nitrosyl complexes are important intermediates in biology. While there are numerous examples of low-spin heme iron-nitrosyl complexes in different oxidation states, much less is known about high-spin (hs) non-heme iron-nitrosyls in oxidation states other than the formally ferrous NO adducts ({FeNO}7 in the Enemark-Feltham notation). In this study, we present a complete series of hs-{FeNO}6-8 complexes using the TMG3tren coligand. Redox transformations from the hs-{FeNO}7 complex [Fe(TMG3tren)(NO)]2+ to its {FeNO}6 and {FeNO}8 analogs do not alter the coordination environment of the iron center, allowing for detailed comparisons between these species. Here, we present new MCD, NRVS, XANES/EXAFS, and Mössbauer data, demonstrating that these redox transformations are metal based, which allows us to access hs-Fe(II)-NO-, Fe(III)-NO-, and Fe(IV)-NO- complexes. Vibrational data, analyzed by NCA, directly quantify changes in Fe-NO bonding along this series. Optical data allow for the identification of a "spectator" charge-transfer transition that, together with Mössbauer and XAS data, directly monitors the electronic changes of the Fe center. Using EXAFS, we are also able to provide structural data for all complexes. The magnetic properties of the complexes are further analyzed (from magnetic Mössbauer). The properties of our hs-{FeNO}6-8 complexes are then contrasted to corresponding, low-spin iron-nitrosyl complexes where redox transformations are generally NO centered. The hs-{FeNO}8 complex can further be protonated by weak acids, and the product of this reaction is characterized. Taken together, these results provide unprecedented insight into the properties of biologically relevant non-heme iron-nitrosyl complexes in three relevant oxidation states.

Original languageEnglish (US)
Pages (from-to)11341-11359
Number of pages19
JournalJournal of the American Chemical Society
Volume140
Issue number36
DOIs
StatePublished - Sep 12 2018

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Ligands
Iron
Oxidation-Reduction
Heme
Oxidation
Charge transfer
Magnetic properties
Metals
Acids
dinitrosyl iron complex

All Science Journal Classification (ASJC) codes

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

Cite this

Speelman, A. L., White, C. J., Zhang, B., Alp, E. E., Zhao, J., Hu, M., ... Lehnert, N. (2018). Non-heme High-Spin {FeNO}6-8 Complexes: One Ligand Platform Can Do It All. Journal of the American Chemical Society, 140(36), 11341-11359. https://doi.org/10.1021/jacs.8b06095
Speelman, Amy L. ; White, Corey J. ; Zhang, Bo ; Alp, E. Ercan ; Zhao, Jiyong ; Hu, Michael ; Krebs, Carsten ; Penner-Hahn, James ; Lehnert, Nicolai. / Non-heme High-Spin {FeNO}6-8 Complexes : One Ligand Platform Can Do It All. In: Journal of the American Chemical Society. 2018 ; Vol. 140, No. 36. pp. 11341-11359.
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abstract = "Heme and non-heme iron-nitrosyl complexes are important intermediates in biology. While there are numerous examples of low-spin heme iron-nitrosyl complexes in different oxidation states, much less is known about high-spin (hs) non-heme iron-nitrosyls in oxidation states other than the formally ferrous NO adducts ({FeNO}7 in the Enemark-Feltham notation). In this study, we present a complete series of hs-{FeNO}6-8 complexes using the TMG3tren coligand. Redox transformations from the hs-{FeNO}7 complex [Fe(TMG3tren)(NO)]2+ to its {FeNO}6 and {FeNO}8 analogs do not alter the coordination environment of the iron center, allowing for detailed comparisons between these species. Here, we present new MCD, NRVS, XANES/EXAFS, and M{\"o}ssbauer data, demonstrating that these redox transformations are metal based, which allows us to access hs-Fe(II)-NO-, Fe(III)-NO-, and Fe(IV)-NO- complexes. Vibrational data, analyzed by NCA, directly quantify changes in Fe-NO bonding along this series. Optical data allow for the identification of a {"}spectator{"} charge-transfer transition that, together with M{\"o}ssbauer and XAS data, directly monitors the electronic changes of the Fe center. Using EXAFS, we are also able to provide structural data for all complexes. The magnetic properties of the complexes are further analyzed (from magnetic M{\"o}ssbauer). The properties of our hs-{FeNO}6-8 complexes are then contrasted to corresponding, low-spin iron-nitrosyl complexes where redox transformations are generally NO centered. The hs-{FeNO}8 complex can further be protonated by weak acids, and the product of this reaction is characterized. Taken together, these results provide unprecedented insight into the properties of biologically relevant non-heme iron-nitrosyl complexes in three relevant oxidation states.",
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Speelman, AL, White, CJ, Zhang, B, Alp, EE, Zhao, J, Hu, M, Krebs, C, Penner-Hahn, J & Lehnert, N 2018, 'Non-heme High-Spin {FeNO}6-8 Complexes: One Ligand Platform Can Do It All', Journal of the American Chemical Society, vol. 140, no. 36, pp. 11341-11359. https://doi.org/10.1021/jacs.8b06095

Non-heme High-Spin {FeNO}6-8 Complexes : One Ligand Platform Can Do It All. / Speelman, Amy L.; White, Corey J.; Zhang, Bo; Alp, E. Ercan; Zhao, Jiyong; Hu, Michael; Krebs, Carsten; Penner-Hahn, James; Lehnert, Nicolai.

In: Journal of the American Chemical Society, Vol. 140, No. 36, 12.09.2018, p. 11341-11359.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Non-heme High-Spin {FeNO}6-8 Complexes

T2 - One Ligand Platform Can Do It All

AU - Speelman, Amy L.

AU - White, Corey J.

AU - Zhang, Bo

AU - Alp, E. Ercan

AU - Zhao, Jiyong

AU - Hu, Michael

AU - Krebs, Carsten

AU - Penner-Hahn, James

AU - Lehnert, Nicolai

PY - 2018/9/12

Y1 - 2018/9/12

N2 - Heme and non-heme iron-nitrosyl complexes are important intermediates in biology. While there are numerous examples of low-spin heme iron-nitrosyl complexes in different oxidation states, much less is known about high-spin (hs) non-heme iron-nitrosyls in oxidation states other than the formally ferrous NO adducts ({FeNO}7 in the Enemark-Feltham notation). In this study, we present a complete series of hs-{FeNO}6-8 complexes using the TMG3tren coligand. Redox transformations from the hs-{FeNO}7 complex [Fe(TMG3tren)(NO)]2+ to its {FeNO}6 and {FeNO}8 analogs do not alter the coordination environment of the iron center, allowing for detailed comparisons between these species. Here, we present new MCD, NRVS, XANES/EXAFS, and Mössbauer data, demonstrating that these redox transformations are metal based, which allows us to access hs-Fe(II)-NO-, Fe(III)-NO-, and Fe(IV)-NO- complexes. Vibrational data, analyzed by NCA, directly quantify changes in Fe-NO bonding along this series. Optical data allow for the identification of a "spectator" charge-transfer transition that, together with Mössbauer and XAS data, directly monitors the electronic changes of the Fe center. Using EXAFS, we are also able to provide structural data for all complexes. The magnetic properties of the complexes are further analyzed (from magnetic Mössbauer). The properties of our hs-{FeNO}6-8 complexes are then contrasted to corresponding, low-spin iron-nitrosyl complexes where redox transformations are generally NO centered. The hs-{FeNO}8 complex can further be protonated by weak acids, and the product of this reaction is characterized. Taken together, these results provide unprecedented insight into the properties of biologically relevant non-heme iron-nitrosyl complexes in three relevant oxidation states.

AB - Heme and non-heme iron-nitrosyl complexes are important intermediates in biology. While there are numerous examples of low-spin heme iron-nitrosyl complexes in different oxidation states, much less is known about high-spin (hs) non-heme iron-nitrosyls in oxidation states other than the formally ferrous NO adducts ({FeNO}7 in the Enemark-Feltham notation). In this study, we present a complete series of hs-{FeNO}6-8 complexes using the TMG3tren coligand. Redox transformations from the hs-{FeNO}7 complex [Fe(TMG3tren)(NO)]2+ to its {FeNO}6 and {FeNO}8 analogs do not alter the coordination environment of the iron center, allowing for detailed comparisons between these species. Here, we present new MCD, NRVS, XANES/EXAFS, and Mössbauer data, demonstrating that these redox transformations are metal based, which allows us to access hs-Fe(II)-NO-, Fe(III)-NO-, and Fe(IV)-NO- complexes. Vibrational data, analyzed by NCA, directly quantify changes in Fe-NO bonding along this series. Optical data allow for the identification of a "spectator" charge-transfer transition that, together with Mössbauer and XAS data, directly monitors the electronic changes of the Fe center. Using EXAFS, we are also able to provide structural data for all complexes. The magnetic properties of the complexes are further analyzed (from magnetic Mössbauer). The properties of our hs-{FeNO}6-8 complexes are then contrasted to corresponding, low-spin iron-nitrosyl complexes where redox transformations are generally NO centered. The hs-{FeNO}8 complex can further be protonated by weak acids, and the product of this reaction is characterized. Taken together, these results provide unprecedented insight into the properties of biologically relevant non-heme iron-nitrosyl complexes in three relevant oxidation states.

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