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Nitric Oxide Activation by Distal Redox Modulation in Tetranuclear Iron Nitrosyl Complexes

De Ruiter, Graham and Thompson, Niklas B. and Lionetti, Davide and Agapie, Theodor (2015) Nitric Oxide Activation by Distal Redox Modulation in Tetranuclear Iron Nitrosyl Complexes. Journal of the American Chemical Society, 137 (44). pp. 14094-14106. ISSN 0002-7863. PMCID PMC4871614. http://resolver.caltech.edu/CaltechAUTHORS:20151109-102021262

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[img] PDF (Synthetic procedures for [LFe3(PhPz)3OFe] and [LFe3(PhPz)3OFe][BF4]; reactivity studies with complexes 6 and 8; characterization data and crystal structures (Figures S1–S37); refinement data, bond angles and distances, and spectroscopic, Mössbauer, ...) - Supplemental Material
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Abstract

A series of tetranuclear iron complexes displaying a site-differentiated metal center was synthesized. Three of the metal centers are coordinated to our previously reported ligand, based on a 1,3,5-triarylbenzene motif with nitrogen and oxygen donors. The fourth (apical) iron center is coordinatively unsaturated and appended to the trinuclear core through three bridging pyrazolates and an interstitial μ_4-oxide moiety. Electrochemical studies of complex [LFe_3(PhPz)3OFe][OTf]_2 revealed three reversible redox events assigned to the Fe^(II)_4/Fe^(II)_3Fe^(III) (−1.733 V), Fe^(II)_3Fe^(III)/Fe^(II)_2Fe^(III)_2 (−0.727 V), and Fe^(II)_2Fe^(III)_2/Fe^(II)Fe^(III)_3 (0.018 V) redox couples. Combined Mössbauer and crystallographic studies indicate that the change in oxidation state is exclusively localized at the triiron core, without changing the oxidation state of the apical metal center. This phenomenon is assigned to differences in the coordination environment of the two metal sites and provides a strategy for storing electron and hole equivalents without affecting the oxidation state of the coordinatively unsaturated metal. The presence of a ligand-binding site allowed the effect of redox modulation on nitric oxide activation by an Fe^(II) metal center to be studied. Treatment of the clusters with nitric oxide resulted in binding of NO to the apical iron center, generating a {FeNO}^7 moiety. As with the NO-free precursors, the three reversible redox events are localized at the iron centers distal from the NO ligand. Altering the redox state of the triiron core resulted in significant change in the NO stretching frequency, by as much as 100 cm^(–1). The increased activation of NO is attributed to structural changes within the clusters, in particular, those related to the interaction of the metal centers with the interstitial atom. The differences in NO activation were further shown to lead to differential reactivity, with NO disproportionation and N_2O formation performed by the more electron-rich cluster.


Item Type:Article
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URLURL TypeDescription
http://dx.doi.org/10.1021/jacs.5b07397DOIArticle
http://pubs.acs.org/doi/abs/10.1021/jacs.5b07397PublisherArticle
http://pubs.acs.org/doi/suppl/10.1021/jacs.5b07397PublisherSupporting Information
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4871614/PubMed CentralArticle
ORCID:
AuthorORCID
Thompson, Niklas B.0000-0003-2745-4945
Agapie, Theodor0000-0002-9692-7614
Additional Information:© 2015 American Chemical Society. Received: July 15, 2015. Publication Date (Web): September 21, 2015. This research was supported by the California Institute of Technology and the NIH (R01-GM102687A). T.A. is a Sloan, Dreyfus, and Cottrell fellow. T.A. and G.de.R. are grateful for a Camille & Henry Dreyfus Environmental Chemistry Fellowship. We thank Michael K. Takase and Lawrence M. Henling for assistance with crystallography. In addition, we would like to thank the anonymous referees for providing useful comments and suggestions. The authors declare no competing financial interest.
Funders:
Funding AgencyGrant Number
NIHR01-GM102687A
Camille and Henry Dreyfus FoundationUNSPECIFIED
PubMed Central ID:PMC4871614
Record Number:CaltechAUTHORS:20151109-102021262
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20151109-102021262
Official Citation:Nitric Oxide Activation by Distal Redox Modulation in Tetranuclear Iron Nitrosyl Complexes Graham de Ruiter, Niklas B. Thompson, Davide Lionetti, and Theodor Agapie Journal of the American Chemical Society 2015 137 (44), 14094-14106 DOI: 10.1021/jacs.5b07397
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:61989
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:09 Nov 2015 18:46
Last Modified:27 Nov 2017 21:39

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