A mononuclear nonheme {FeNO}<sup>6</sup> complex: synthesis and structural and spectroscopic characterization

Hong, Seung-Woo; Yan, James J.; Karmalkar, Deepika G.; Sutherlin, Kyle D.; Jin, Kim Hyung; Lee, Yong Min; Goo, Yire; Mascharak, Pradip K.; Hedman, Britt; Karlin, Kenneth D.; Solomon, Edward I.; Nam, Wonwoo

doi:10.1039/c8sc01962b

Cited by 16 publications

(13 citation statements)

References 76 publications

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“…For example, whereas ferrous CO complexes are typically diamagnetic, two S = 1 ferrous CO complexes with trigonal-bipyramidal geometries have been isolated. 103,104 Nevertheless, in two other systems with square pyramidal geometries, S = 1 {FeNO} 6 complexes have been proposed 105,106 (although recent spectroscopic data on the TAML compound suggest an S = 0 spin state), 107 indicating that hs-{FeNO} 6 complexes may generally have an S = 1 spin state as observed in this study.…”

Section: Discussioncontrasting

confidence: 51%

“…However, it should be noted that both 3 and [Fe(PS3*)(NO)] are trigonal bipyramidal complexes, which generally favor an S = 1 spin state in d 6 systems due to the degeneracy of the d xz / yz and d x 2– y 2/ xy orbitals in a trigonal ligand field. For example, whereas ferrous CO complexes are typically diamagnetic, two S = 1 ferrous CO complexes with trigonal-bipyramidal geometries have been isolated. , Nevertheless, in two other systems with square pyramidal geometries, S = 1 {FeNO} 6 complexes have been proposed , (although recent spectroscopic data on the TAML compound suggest an S = 0 spin state), indicating that hs-{FeNO} 6 complexes may generally have an S = 1 spin state as observed in this study.…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2018

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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} in the Enemark-Feltham notation). In this study, we present a complete series of hs-{FeNO} complexes using the TMGtren coligand. Redox transformations from the hs-{FeNO} complex [Fe(TMGtren)(NO)] to its {FeNO} and {FeNO} 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} complexes are then contrasted to corresponding, low-spin iron-nitrosyl complexes where redox transformations are generally NO centered. The hs-{FeNO} 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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Section: Discussioncontrasting

confidence: 51%

Section: Discussionmentioning

confidence: 99%

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

et al. 2018

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“…Lippard and coworker reported the 5C complex [Fe(TAML)(NO)] − (TAML = tetraamidomacrocyclic ligand tetraanion), which bears a close to linear Fe–N–O bond (with an angle of 172°) and an N–O stretching frequency of 1797 cm –1 . Initially, this complex was proposed to have an S t = 1 ground state, but it was later shown by Nam and coworkers that this complex is in fact diamagnetic, and hence, of ls-{FeNO} 6 type . Surprisingly, [Fe(TAML)(NO)] − can reversibly bind NO when purged with N 2 , which is a rare property for non-heme FeNO complexes.…”

Section: Non-heme Iron Centers and Nomentioning

confidence: 58%

The Biologically Relevant Coordination Chemistry of Iron and Nitric Oxide: Electronic Structure and Reactivity

et al. 2021

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Nitric oxide (NO) is an important signaling molecule that is involved in a wide range of physiological and pathological events in biology. Metal coordination chemistry, especially with iron, is at the heart of many biological transformations involving NO. A series of heme proteins, nitric oxide synthases (NOS), soluble guanylate cyclase (sGC), and nitrophorins, are responsible for the biosynthesis, sensing, and transport of NO. Alternatively, NO can be generated from nitrite by heme- and copper-containing nitrite reductases (NIRs). The NO-bearing small molecules such as nitrosothiols and dinitrosyl iron complexes (DNICs) can serve as an alternative vehicle for NO storage and transport. Once NO is formed, the rich reaction chemistry of NO leads to a wide variety of biological activities including reduction of NO by heme or non-heme iron-containing NO reductases and protein post-translational modifications by DNICs. Much of our understanding of the reactivity of metal sites in biology with NO and the mechanisms of these transformations has come from the elucidation of the geometric and electronic structures and chemical reactivity of synthetic model systems, in synergy with biochemical and biophysical studies on the relevant proteins themselves. This review focuses on recent advancements from studies on proteins and model complexes that not only have improved our understanding of the biological roles of NO but also have provided foundations for biomedical research and for bio-inspired catalyst design in energy science.

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“…The v no stretch of observed for 9 (1667 cm −1 ) and 10 (1687 cm −1 ) is also significantly lower than the characteristic range for sixand even five-coordinate {Fe(NO)} 6 complexes. 69–72 In addition, the especially low Fe-N-O angles (150.9(2)° in 9 and 154.4(1)° in 10 ) are closer to the range of the more electron rich {Fe(NO)} 7 complexes, 73 where either the Fe(II)-NO• radical or Fe(III)-NO-description would be more appropriate. This description, coupled with the fact that both complexes are diamagnetic, suggests that the PDI ligand is also likely a monoradical (see computations below).…”

Section: Resultsmentioning

confidence: 93%

Hemilabile Proton Relays and Redox Activity Lead to {FeNO}^x and Significant Rate Enhancements in NO₂^– Reduction

et al. 2018

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Incorporation of the triad of redox-activity, hemilability, and proton responsivity, into a single ligand scaffold is reported. Due to this triad, the complexes Fe(PyrrPDI)(CO)2 (3) and Fe(MorPDI)(CO)2 (4) display 40-fold enhancements in the initial rate of NO2− reduction, with respect to Fe(MeOPDI)(CO)2 (7). Utilizing the proper sterics and pKa of the pendant base(s) to introduce hemilability into our ligand scaffolds, we report unusual {FeNO}x mononitrosyl iron complexes (MNICs) as intermediates in the NO2− reduction reaction. The {FeNO}x species behave spectroscopically and computationally similar to {FeNO}7, an unusual intermediate-spin Fe(III) coupled to triplet NO− and a singly-reduced PDI ligand. These {FeNO}x MNICs facilitate the enhancements in the initial rate.

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A mononuclear nonheme {FeNO}⁶ complex: synthesis and structural and spectroscopic characterization

Abstract: X-ray structures of nonheme {FeNO}6 and iron(iii)-nitrito complexes bearing a tetraamido macrocyclic ligand are reported along with three different generation pathways.

Cited by 16 publications

References 76 publications

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

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

The Biologically Relevant Coordination Chemistry of Iron and Nitric Oxide: Electronic Structure and Reactivity

Hemilabile Proton Relays and Redox Activity Lead to {FeNO}^x and Significant Rate Enhancements in NO₂^– Reduction

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A mononuclear nonheme {FeNO}6 complex: synthesis and structural and spectroscopic characterization

Abstract: X-ray structures of nonheme {FeNO}6 and iron(iii)-nitrito complexes bearing a tetraamido macrocyclic ligand are reported along with three different generation pathways.

Cited by 16 publications

References 76 publications

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

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

The Biologically Relevant Coordination Chemistry of Iron and Nitric Oxide: Electronic Structure and Reactivity

Hemilabile Proton Relays and Redox Activity Lead to {FeNO}x and Significant Rate Enhancements in NO2– Reduction

Contact Info

Product

Resources

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A mononuclear nonheme {FeNO}⁶ complex: synthesis and structural and spectroscopic characterization

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

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

Hemilabile Proton Relays and Redox Activity Lead to {FeNO}^x and Significant Rate Enhancements in NO₂^– Reduction