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Karmakar S, Patra S, Pramanik K, Adhikary A, Dey A, Majumdar A. Reactivity of Thiolate and Hydrosulfide with a Mononuclear {FeNO} 7 Complex Featuring a Very High N-O Stretching Frequency. Inorg Chem 2024; 63:8537-8555. [PMID: 38679874 DOI: 10.1021/acs.inorgchem.3c03274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/01/2024]
Abstract
Synthesis, characterization, electronic structure, and redox reactions of a mononuclear {FeNO}7 complex with a very high N-O stretching frequency in solution are presented. Nitrosylation of [(LKP)Fe(DMF)]2+ (1) (LKP = tris((1-methyl-4,5-diphenyl-1H-imidazol-2-yl)methyl)amine) produced a five-coordinate {FeNO}7 complex, [(LKP)Fe(NO)]2+ (2). While complex 2 could accommodate an additional water molecule to generate a six-coordinate {FeNO}7 complex, [(LKP)Fe(NO)(H2O)]2+ (3), the coordinated H2O in 3 dissociates to generate 2 in solution. The molecular structure of 2 features a nearly linear Fe-N-O unit with an Fe-N distance of 1.744(4) Å, N-O distance of 1.162(5) Å, and
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Affiliation(s)
- Soumik Karmakar
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - Suman Patra
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - Koushik Pramanik
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - Amit Adhikary
- Department of Chemistry, Technology Campus, University of Calcutta, JD Block, Sector III, Salt Lake, Kolkata 700098, India
| | - Abhishek Dey
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - Amit Majumdar
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
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2
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Ren W, Schulz CE, Shroyer MH, Xu W, Xi S, An P, Guo W, Li J. Electronic Configurations and the Effect of Peripheral Substituents of (Nitrosyl)iron Corroles. Inorg Chem 2022; 61:20385-20396. [DOI: 10.1021/acs.inorgchem.2c03026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Wanjie Ren
- College of Materials Science and Optoelectronic Technology and Chinese Academy of Sciences Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Yanqi Lake, Huairou District, Beijing101408, P. R. China
| | - Charles E. Schulz
- Department of Physics and Astronomy, Knox College, Galesburg, Illinois61401, United States
| | - Mark H. Shroyer
- Department of Physics and Astronomy, Knox College, Galesburg, Illinois61401, United States
| | - Wei Xu
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences (CAS), Beijing100049, P. R. China
- RICMASS, Rome International Center for Materials Science Superstripes, Via dei Sabelli 119A, Rome00185, Italy
| | - Shibo Xi
- Institute of Chemical and Engineering Sciences, Agency for Science, Technology and Research, 1 Pesek Road, Jurong Island, Singapore627833, Singapore
| | - Pengfei An
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences (CAS), Beijing100049, P. R. China
| | - Wenping Guo
- National Energy Center for Coal to Clean Fuels, Synfuels China Co., Ltd., Huairou District, Beijing101400, P. R. China
| | - Jianfeng Li
- College of Materials Science and Optoelectronic Technology and Chinese Academy of Sciences Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Yanqi Lake, Huairou District, Beijing101408, P. R. China
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3
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Kim Y, Sridharan A, Suess DLM. The Elusive Mononitrosylated [Fe 4 S 4 ] Cluster in Three Redox States. Angew Chem Int Ed Engl 2022; 61:e202213032. [PMID: 36194444 PMCID: PMC9669169 DOI: 10.1002/anie.202213032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2022] [Indexed: 11/06/2022]
Abstract
Iron-sulfur clusters are well-established targets in biological nitric oxide (NO) chemistry, but the key intermediate in these processes-a mononitrosylated [Fe4 S4 ] cluster-has not been fully characterized in a protein or a synthetic model thereof. Here, we report the synthesis of a three-member redox series of isostructural mononitrosylated [Fe4 S4 ] clusters. Mononitrosylation was achieved by binding NO to a 3 : 1 site-differentiated [Fe4 S4 ]+ cluster; subsequent oxidation and reduction afforded the other members of the series. All three clusters feature a local high-spin Fe3+ center antiferromagnetically coupled to 3 [NO]- . The observation of an anionic NO ligand suggests that NO binding is accompanied by formal electron transfer from the cluster to NO. Preliminary reactivity studies with the monocationic cluster demonstrate that exposure to excess NO degrades the cluster, supporting the intermediacy of mononitrosylated intermediates in NO sensing/signaling.
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Affiliation(s)
- Youngsuk Kim
- Department of ChemistryMassachusetts Institute of Technology77 Massachusetts AveCambridgeMA 02139USA
- Department of ChemistryPusan National UniversityBusan46241Republic of Korea
| | - Arun Sridharan
- Department of ChemistryMassachusetts Institute of Technology77 Massachusetts AveCambridgeMA 02139USA
| | - Daniel L. M. Suess
- Department of ChemistryMassachusetts Institute of Technology77 Massachusetts AveCambridgeMA 02139USA
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4
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White CJ, Lengel MO, Bracken AJ, Kampf JW, Speelman AL, Alp EE, Hu MY, Zhao J, Lehnert N. Distortion of the [FeNO] 2 Core in Flavodiiron Nitric Oxide Reductase Models Inhibits N-N Bond Formation and Promotes Formation of Unusual Dinitrosyl Iron Complexes: Implications for Catalysis and Reactivity. J Am Chem Soc 2022; 144:3804-3820. [PMID: 35212523 DOI: 10.1021/jacs.1c10388] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Flavodiiron nitric oxide reductases (FNORs) carry out the reduction of nitric oxide (NO) to nitrous oxide (N2O), allowing infectious pathogens to mitigate toxic levels of NO generated in the human immune response. We previously reported the model complex [Fe2(BPMP)(OPr)(NO)2](OTf)2 (1, OPr- = propionate) that contains two coplanar NO ligands and that is capable of quantitative NO reduction to N2O [White et al. J. Am. Chem. Soc. 2018, 140, 2562-2574]. Here we investigate, for the first time, how a distortion of the active site affects the ability of the diiron core to mediate N2O formation. For this purpose, we prepared several analogues of 1 that contain two monodentate ligands in place of the bridging carboxylate, [Fe2(BPMP)(X)2(NO)2]3+/1+ (2-X; X = triflate, 1-methylimidazole, or methanol). Structural data of 2-X show that without the bridging carboxylate, the diiron core expands, leading to elongated (O)N-N(O) distances (from 2.80 Å in 1 to 3.00-3.96 Å in 2-X) and distorted (O)N-Fe-Fe-N(O) dihedral angles (from coplanarity (5.9°) in 1 to 52.9-85.1° in 2-X). Whereas 1 produces quantitative amounts of N2O upon one-electron reduction, N2O production is substantially impeded in 2-X, to an initial 5-10% N2O yield. The main products after reduction are unprecedented hs-FeII/{Fe(NO)2}9/10 dinitrosyl iron complexes (DNICs). Even though mononuclear DNICs are stable and do not show N-N coupling (since it is a spin-forbidden process), the hs-FeII/{Fe(NO)2}9/10 DNICs obtained from 2-X show unexpected reactivity and produce up to quantitative N2O yields after 2 h. The implications of these results for the active site structure of FNORs are discussed.
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Affiliation(s)
- Corey J White
- Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Michael O Lengel
- Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Abigail J Bracken
- Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Jeff W Kampf
- Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Amy L Speelman
- Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - E Ercan Alp
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Michael Y Hu
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Jiyong Zhao
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Nicolai Lehnert
- Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, United States
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5
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Lehnert N, Kim E, Dong HT, Harland JB, Hunt AP, Manickas EC, Oakley KM, Pham J, Reed GC, Alfaro VS. The Biologically Relevant Coordination Chemistry of Iron and Nitric Oxide: Electronic Structure and Reactivity. Chem Rev 2021; 121:14682-14905. [PMID: 34902255 DOI: 10.1021/acs.chemrev.1c00253] [Citation(s) in RCA: 92] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
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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Affiliation(s)
- Nicolai Lehnert
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Eunsuk Kim
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Hai T Dong
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Jill B Harland
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Andrew P Hunt
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Elizabeth C Manickas
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Kady M Oakley
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - John Pham
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Garrett C Reed
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Victor Sosa Alfaro
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
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6
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Pal N, Jana M, Majumdar A. Reduction of NO by diiron complexes in relation to flavodiiron nitric oxide reductases. Chem Commun (Camb) 2021; 57:8682-8698. [PMID: 34373873 DOI: 10.1039/d1cc03149j] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Reduction of nitric oxide (NO) to nitrous oxide (N2O) is associated with immense biological and health implications. Flavodiiron nitric oxide reductases (FNORs) are diiron containing enzymes that catalyze the two electron reduction of NO to N2O and help certain pathogenic bacteria to survive under "nitrosative stress" in anaerobic growth conditions. Consequently, invading bacteria can proliferate inside the body of mammals by bypassing the immune defense mechanism involving NO and may thus lead to harmful infections. Various mechanisms, namely the direct reduction, semireduction, superreduction and hyponitrite mechanisms, have been proposed over time for catalytic NO reduction by FNORs. Model studies in relation to the diiron active site of FNORs have immensely helped to replicate the minimal structure-reactivity relationship and to understand the mechanism of NO reduction. A brief overview of the FNOR activity and the proposed reaction mechanisms followed by a systematic description and detailed analysis of the model studies is presented, which describes the development in the area of NO reduction by diiron complexes and its implications. A great deal of successful modeling chemistry as well as the shortcomings related to the synthesis and reactivity studies is discussed in detail. Finally, future prospects in this particular area of research are proposed, which in due course may bring more clarity in the understanding of this important redox reaction.
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Affiliation(s)
- Nabhendu Pal
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Kolkata 700032, India.
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7
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Chiang CK, Chu KT, Lin CC, Xie SR, Liu YC, Demeshko S, Lee GH, Meyer F, Tsai ML, Chiang MH, Lee CM. Photoinduced NO and HNO Production from Mononuclear {FeNO}6 Complex Bearing a Pendant Thiol. J Am Chem Soc 2020; 142:8649-8661. [DOI: 10.1021/jacs.9b13837] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Chuan-Kuei Chiang
- Department of Applied Science, National Taitung University, Taitung 950, Taiwan
| | - Kai-Ti Chu
- Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan
| | - Chia-Chin Lin
- Department of Chemistry, National Sun Yat-sen University, Kaohsiung 804, Taiwan
| | - Shi-Rou Xie
- Department of Applied Science, National Taitung University, Taitung 950, Taiwan
| | - Yu-Chiao Liu
- Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan
| | - Serhiy Demeshko
- Universität Göttingen, Institut für Anorganische Chemie, Tammannstraße 4, D-37077 Göttingen, Germany
| | - Gene-Hsiang Lee
- Instrumentation Center, National Taiwan University, Taipei 107, Taiwan
| | - Franc Meyer
- Universität Göttingen, Institut für Anorganische Chemie, Tammannstraße 4, D-37077 Göttingen, Germany
| | - Ming-Li Tsai
- Department of Chemistry, National Sun Yat-sen University, Kaohsiung 804, Taiwan
- Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan
| | - Ming-Hsi Chiang
- Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan
- Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan
| | - Chien-Ming Lee
- Department of Applied Science, National Taitung University, Taitung 950, Taiwan
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8
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Jana M, White CJ, Pal N, Demeshko S, Cordes (née Kupper) C, Meyer F, Lehnert N, Majumdar A. Functional Models for the Mono- and Dinitrosyl Intermediates of FNORs: Semireduction versus Superreduction of NO. J Am Chem Soc 2020; 142:6600-6616. [DOI: 10.1021/jacs.9b13795] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Manish Jana
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, West Bengal, India
| | - Corey J. White
- Department of Chemistry, The University of Michigan, 930 N. University Avenue, Ann Arbor 48109, Michigan, United States
| | - Nabhendu Pal
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, West Bengal, India
| | - Serhiy Demeshko
- Institut für Anorganische Chemie, Georg-August-Universität, Tammannstraße 4, Göttingen 37077, Germany
| | | | - Franc Meyer
- Institut für Anorganische Chemie, Georg-August-Universität, Tammannstraße 4, Göttingen 37077, Germany
| | - Nicolai Lehnert
- Department of Chemistry, The University of Michigan, 930 N. University Avenue, Ann Arbor 48109, Michigan, United States
| | - Amit Majumdar
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, West Bengal, India
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9
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Keilwerth M, Hohenberger J, Heinemann FW, Sutter J, Scheurer A, Fang H, Bill E, Neese F, Ye S, Meyer K. A Series of Iron Nitrosyl Complexes {Fe-NO} 6-9 and a Fleeting {Fe-NO} 10 Intermediate en Route to a Metalacyclic Iron Nitrosoalkane. J Am Chem Soc 2019; 141:17217-17235. [PMID: 31566964 DOI: 10.1021/jacs.9b08053] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Iron-nitrosyls have fascinated chemists for a long time due to the noninnocent nature of the NO ligand that can exist in up to five different oxidation and spin states. Coordination to an open-shell iron center leads to complex electronic structures, which is the reason Enemark-Feltham introduced the {Fe-NO}n notation. In this work, we succeeded in characterizing a series of {Fe-NO}6-9 complexes, including a reactive {Fe-NO}10 intermediate. All complexes were synthesized with the tris-N-heterocyclic carbene ligand tris[2-(3-mesitylimidazol-2-ylidene)ethyl]amine (TIMENMes), which is known to support iron in high and low oxidation states. Reaction of NOBF4 with [(TIMENMes)Fe]2+ resulted in formation of the {Fe-NO}6 compound [(TIMENMes)Fe(NO)(CH3CN)](BF4)3 (1). Stepwise chemical reduction with Zn, Mg, and Na/Hg leads to the isostructural series of high-spin iron nitrosyl complexes {Fe-NO}7,8,9 (2-4). Reduction of {Fe-NO}9 with Cs electride finally yields the highly reduced {Fe-NO}10 intermediate, key to formation of [Cs(crypt-222)][(TIMENMes)Fe(NO)], (5) featuring a metalacyclic [Fe-(NO-NHC)3-] nitrosoalkane unit. All complexes were characterized by single-crystal XRD analyses, temperature and field-dependent SQUID magnetization methods, as well as 57Fe Mössbauer, IR, UV/vis, multinuclear NMR, and dual-mode EPR spectroscopy. Spectroscopy-based DFT analyses provide insight into the electronic structures of all compounds and allowed assignments of oxidation states to iron and NO ligands. An alternative synthesis to the {Fe-NO}8 complex was found via oxygenation of the nitride complex [(TIMENMes)Fe(N)](BF4). Surprisingly, the resulting {Fe-NO}8 species is electronically and structural similar to the [(TIMENMes)Fe(N)]+ precursor. Based on the structural and electronic similarities between this nitrosyl/nitride complex couple, we adopted the strategy, developed by Wieghardt et al., of extending the Enemark-Feltham nomenclature to nitrido complexes, rendering [(TIMENMes)Fe(N)]+ as a {Fe-N}8 species.
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Affiliation(s)
- Martin Keilwerth
- Department of Chemistry and Pharmacy, Inorganic Chemistry , Friedrich-Alexander-University Erlangen-Nürnberg (FAU) , Egerlandstrasse 1 , D-91058 Erlangen , Germany
| | - Johannes Hohenberger
- Department of Chemistry and Pharmacy, Inorganic Chemistry , Friedrich-Alexander-University Erlangen-Nürnberg (FAU) , Egerlandstrasse 1 , D-91058 Erlangen , Germany
| | - Frank W Heinemann
- Department of Chemistry and Pharmacy, Inorganic Chemistry , Friedrich-Alexander-University Erlangen-Nürnberg (FAU) , Egerlandstrasse 1 , D-91058 Erlangen , Germany
| | - Jörg Sutter
- Department of Chemistry and Pharmacy, Inorganic Chemistry , Friedrich-Alexander-University Erlangen-Nürnberg (FAU) , Egerlandstrasse 1 , D-91058 Erlangen , Germany
| | - Andreas Scheurer
- Department of Chemistry and Pharmacy, Inorganic Chemistry , Friedrich-Alexander-University Erlangen-Nürnberg (FAU) , Egerlandstrasse 1 , D-91058 Erlangen , Germany
| | - Huayi Fang
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstraße 34-36 , D-45470 Mülheim an der Ruhr, Germany
| | - Eckhard Bill
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstraße 34-36 , D-45470 Mülheim an der Ruhr, Germany
| | - Frank Neese
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelmplatz 1 , D-45470 Mülheim an der Ruhr , Germany
| | - Shengfa Ye
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelmplatz 1 , D-45470 Mülheim an der Ruhr , Germany
| | - Karsten Meyer
- Department of Chemistry and Pharmacy, Inorganic Chemistry , Friedrich-Alexander-University Erlangen-Nürnberg (FAU) , Egerlandstrasse 1 , D-91058 Erlangen , Germany
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10
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Lehnert N, Fujisawa K, Camarena S, Dong HT, White CJ. Activation of Non-Heme Iron-Nitrosyl Complexes: Turning Up the Heat. ACS Catal 2019. [DOI: 10.1021/acscatal.9b03219] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Nicolai Lehnert
- Department of Chemistry and Department of Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Kiyoshi Fujisawa
- Department of Chemistry, Ibaraki University, Mito 310-8512, Japan
| | - Stephanie Camarena
- Department of Chemistry and Department of Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Hai T. Dong
- Department of Chemistry and Department of Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Corey J. White
- Department of Chemistry and Department of Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
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11
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Confer AM, Sabuncu S, Siegler MA, Moënne-Loccoz P, Goldberg DP. Mononuclear, Nonheme, High-Spin {FeNO} 7/8 Complexes Supported by a Sterically Encumbered N 4S-Thioether Ligand. Inorg Chem 2019; 58:9576-9580. [PMID: 31328501 DOI: 10.1021/acs.inorgchem.9b01475] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The synthesis of a new nonheme iron NO binding complex, [FeII(CH3CN)(N3Py2PhSEtCN)](BF4)2 (1), is reported. Complex 1, which contains two sterically encumbering phenyl substituents, exhibits a high-spin (hs) FeII (S = 2) ground state in contrast to the S = 0 ground state for unsubstituted [FeII(CH3CN)(N3PySEtCN)(BF4)2. Reaction of 1 with NO(g) in CH3CN yields an {FeNO}7 (S = 3/2) complex 2, which slowly decays at 25 °C with loss of NO• to regenerate 1. One-electron reduction of 2 with Cr(C6H6)2 at -40 °C yields the metastable, S = 1 {FeNO}8 complex 3. The nitrosyl moieties in thioether-ligated 2 and 3 are significantly less activated than in thiolate-ligated [Fe(NO)(N3PyS)]+/0, a structurally analogous pair of hs {FeNO}7/8 complexes. Calculations reveal that reduction of 2 is iron-centered, which may be a general property of hs {FeNO}7/8 complexes.
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Affiliation(s)
- Alex M Confer
- Department of Chemistry , The Johns Hopkins University , Baltimore , Maryland 21218 , United States
| | - Sinan Sabuncu
- Department of Biochemistry & Molecular Biology , Oregon Health & Science University , Portland , Oregon 97239 , United States
| | - Maxime A Siegler
- Department of Chemistry , The Johns Hopkins University , Baltimore , Maryland 21218 , United States
| | - Pierre Moënne-Loccoz
- Department of Biochemistry & Molecular Biology , Oregon Health & Science University , Portland , Oregon 97239 , United States
| | - David P Goldberg
- Department of Chemistry , The Johns Hopkins University , Baltimore , Maryland 21218 , United States
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12
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Popescu CV, Ding S, Ghosh P, Hall MB, Cohara M. Mössbauer Spectroscopy and Theoretical Studies of Iron Bimetallic Complexes Showing Electrocatalytic Hydrogen Evolution. Inorg Chem 2019; 58:7069-7077. [PMID: 31059245 DOI: 10.1021/acs.inorgchem.9b00746] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Mössbauer spectroscopy and density functional theory (DFT) calculations are reported for the mononuclear Fe-nitrosyl complex [Fe( N, N'-bis(2-mercaptoethyl)-1,4-diazacycloheptane)NO] {[Fe(bme-dach)(NO)] (1)} and the series of dithiolate-bridged dinuclear complexes M-Fe(CO)Cp [M = Fe(bme-dach)(NO) (1-A), Ni(bme-dach) (2-A), and Co(bme-dach)(NO) (3-A)], in which M is a metallo-ligand to Fe(CO)Cp+ (Fe'Cp). The latter is an organometallic fragment in which Fe is coordinated by one CO and one cyclopentadienyl ligand. Complexes 1-A and 2-A were previously shown to have electrocatalytic hydrogen evolution activity. Mononuclear {Fe-NO}7 complex 1, with overall spin of 1/2, has an isomer shift of 0.23(2) mm/s [Δ EQ = 1.37(2) mm/s] and magnetic hyperfine couplings of {-38 T, -26.8 T, 8.6 T}. In complexes 2-A and 3-A, Fe'(CO)Cp+ has a diamagnetic ground state and δ = 0.33(2) mm/s (Δ EQ ≈ 1.78 mm/s), consistent with a low-spin FeII site. In contrast, in complex 1-A, M = Fe(bme-dach)(NO) (i.e., complex 1) the magnetic hyperfine interactions of both metallo-ligand, M, and low-spin Fe'Cp are perturbed and Fe'Cp exhibits small magnetic hyperfine interactions, although its isomer shift and quadrupole splittings are largely unaltered. The DFT calculations for 1-A are in agreement with the paramagnetism observed for the Fe'(CO)Cp+ iron site.
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Affiliation(s)
- Codrina V Popescu
- Department of Chemistry , University of St. Thomas , St. Paul , Minnesota 55105 , United States
| | - Shengda Ding
- Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States
| | - Pokhraj Ghosh
- Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States
| | - Michael B Hall
- Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States
| | - Morgan Cohara
- Department of Chemistry , Colgate University , Hamilton , New York 13346 , United States
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13
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Pecak J, Stöger B, Mastalir M, Veiros LF, Ferreira LP, Pignitter M, Linert W, Kirchner K. Five-Coordinate Low-Spin {FeNO} 7 PNP Pincer Complexes. Inorg Chem 2019; 58:4641-4646. [PMID: 30880390 DOI: 10.1021/acs.inorgchem.9b00235] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The synthesis and characterization of air-stable cationic mono nitrosonium Fe(I) PNP pincer complexes of the type [Fe(PNP)(NO)Cl]+ are described. These complexes are obtained via direct nitroslyation of [Fe(PNP)Cl2] with nitric oxide at ambient pressure. On the basis of magnetic and EPR measurements as well as DFT calculations, these compounds were found to adopt a low-spin d7 configuration and feature a nearly linear bound NO ligand suggesting FeINO+ rather than FeIINO• character. X-ray structures of all nitrosonium Fe(I) PNP complexes are presented. Preliminary investigations reveal that [Fe(PNPNH- iPr)(NO)(Cl)]+ efficiently catalyzes the conversion of primary alcohols and aromatic and benzylic amines to yield mono N-alkylated amines in good isolated yields.
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Affiliation(s)
- Jan Pecak
- Institute of Applied Synthetic Chemistry , Vienna University of Technology , Getreidemarkt 9 , A-1060 Vienna , Austria
| | - Berthold Stöger
- X-Ray Center , Vienna University of Technology , Getreidemarkt 9 , A-1060 Vienna , Austria
| | - Matthias Mastalir
- Institute of Applied Synthetic Chemistry , Vienna University of Technology , Getreidemarkt 9 , A-1060 Vienna , Austria
| | - Luis F Veiros
- Centro de Química Estrutural, Instituto Superior Técnico , Universidade de Lisboa , Av. Rovisco Pais No. 1 , 1049-001 Lisboa , Portugal
| | - Liliana P Ferreira
- Biosystems and Integrative Sciences Institute, Faculdade de Ciências , Universidade de Lisboa , 1749-016 Lisboa , Portugal.,Department of Physics , University of Coimbra , 3004-516 Coimbra , Portugal
| | - Marc Pignitter
- Department of Physiological Chemistry, Faculty of Chemistry , University of Vienna , Althanstrasse 14 , 1090 Vienna , Austria
| | - Wolfgang Linert
- Institute of Applied Synthetic Chemistry , Vienna University of Technology , Getreidemarkt 9 , A-1060 Vienna , Austria
| | - Karl Kirchner
- Institute of Applied Synthetic Chemistry , Vienna University of Technology , Getreidemarkt 9 , A-1060 Vienna , Austria
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14
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Truong PT, Broering EP, Dzul SP, Chakraborty I, Stemmler TL, Harrop TC. Simultaneous nitrosylation and N-nitrosation of a Ni-thiolate model complex of Ni-containing SOD. Chem Sci 2018; 9:8567-8574. [PMID: 30568781 PMCID: PMC6253683 DOI: 10.1039/c8sc03321h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 09/17/2018] [Indexed: 11/21/2022] Open
Abstract
Nitric oxide (NO) is used as a substrate analogue/spectroscopic probe of metal sites that bind and activate oxygen and its derivatives. To assess the interaction of superoxide with the Ni center in Ni-containing superoxide dismutase (NiSOD), we studied the reaction of NO+ and NO with the model complex, Et4N[Ni(nmp)(SPh-o-NH2-p-CF3)] (1; nmp2- = dianion of N-(2-mercaptoethyl)picolinamide; -SPh-o-NH2-p-CF3 = 2-amino-4-(trifluoromethyl)benzenethiolate) and its oxidized analogue 1ox , respectively. The ultimate products of these reactions are the disulfide of -SPh-o-NH2-p-CF3 and the S,S-bridged tetrameric complex [Ni4(nmp)4], a result of S-based redox activity. However, introduction of NO to 1 affords the green dimeric {NiNO}10 complex (Et4N)2[{Ni(κ2-SPh-o-NNO-p-CF3)(NO)}2] (2) via NO-induced loss of nmp2- as the disulfide and N-nitrosation of the aromatic thiolate. Complex 2 was characterized by X-ray crystallography and several spectroscopies. These measurements are in-line with other tetrahedral complexes in the {NiNO}10 classification. In contrast to the established stability of this metal-nitrosyl class, the Ni-NO bond of 2 is labile and release of NO from this unit was quantified by trapping the NO with a CoII-porphyrin (70-80% yield). In the process, the Ni ends up coordinated by two o-nitrosaminobenzenethiolato ligands to result in the structurally characterized trans-(Et4N)2[Ni(SPh-o-NNO-p-CF3)2] (3), likely by a disproportionation mechanism. The isolation and characterization of 2 and 3 suggest that: (i) the strongly donating thiolates dominate the electronic structure of Ni-nitrosyls that result in less covalent Ni-NO bonds, and (ii) superoxide undergoes disproportionation via an outer-sphere mechanism in NiSOD as complexes in the {NiNO}9/8 state have yet to be isolated.
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Affiliation(s)
- Phan T Truong
- Department of Chemistry , Center for Metalloenzyme Studies , The University of Georgia , Athens , Georgia 30602 , USA .
| | - Ellen P Broering
- Department of Chemistry , Center for Metalloenzyme Studies , The University of Georgia , Athens , Georgia 30602 , USA .
| | - Stephen P Dzul
- Departments of Pharmaceutical Sciences, Biochemistry, and Molecular Biology , Wayne State University , Detroit , Michigan 48201 , USA
| | - Indranil Chakraborty
- Department of Chemistry and Biochemistry , Florida International University , Miami , Florida 33199 , USA
| | - Timothy L Stemmler
- Departments of Pharmaceutical Sciences, Biochemistry, and Molecular Biology , Wayne State University , Detroit , Michigan 48201 , USA
| | - Todd C Harrop
- Department of Chemistry , Center for Metalloenzyme Studies , The University of Georgia , Athens , Georgia 30602 , USA .
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15
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Banerjee A, Li J, Speelman AL, White CJ, Pawlak PL, Brennessel WW, Lehnert N, Chavez FA. A Structural Model for the Iron-Nitrosyl Adduct of Gentisate Dioxygenase. Eur J Inorg Chem 2018; 2018:4797-4804. [PMID: 32577096 DOI: 10.1002/ejic.201800992] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
We present the synthesis, properties, and characterization of [Fe(T1Et4iPrIP)(NO)(H2O)2](OTf)2 (1) (T1Et4iPrIP = Tris(1-ethyl-4-isopropyl-imidazolyl)phosphine) as a model for the nitrosyl adduct of gentisate 1,2-dioxygenase (GDO). The further characterization of [Fe(T1Et4iPrIP)(THF)(NO)(OTf)](OTf) (2) which was previously communicated (Inorg. Chem. 2014, 53, 5414) is also presented. The weighted average Fe-N-O angle of 162° for 1 is very close to linear (≥ 165°) for these types of complexes. The coordinated water ligands participate in hydrogen bonding interactions. The spectral properties (EPR, UV-vis, FTIR) for 1 are compared with 2 and found to be quite comparable. Complex 1 closely follows the relationship between the Fe-N-O angle and NO vibrational frequency which was previously identified for 6-coordinate {FeNO}7 complexes. Liquid FTIR studies on 2 indicate that the ν(NO) vibration position is sensitive to solvent shifting to lower energy (relative to the solid) in donor solvent THF and shifting to higher energy in dichloromethane. The basis for this behavior is discussed. The K eq for NO binding in 2 was calculated in THF and found to be 470 M-1. Density functional theory (DFT) studies on 1 indicate donation of electron density to the iron center from the π* orbitals of formally NO-. Such a donation accounts for the near linearity of the Fe-N-O bond and the large ν(NO) value of 1791 cm-1.
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Affiliation(s)
- Atanu Banerjee
- Department of Chemistry, Oakland University, Rochester, MI 48309-4477, USA
| | - Jia Li
- Department of Chemistry, Oakland University, Rochester, MI 48309-4477, USA
| | - Amy L Speelman
- Department of Chemistry, The University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Corey J White
- Department of Chemistry, The University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Piotr L Pawlak
- Department of Chemistry, Oakland University, Rochester, MI 48309-4477, USA
| | | | - Nicolai Lehnert
- Department of Chemistry, The University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Ferman A Chavez
- Department of Chemistry, Oakland University, Rochester, MI 48309-4477, USA
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16
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Ghosh P, Ding S, Quiroz M, Bhuvanesh N, Hsieh CH, Palacios PM, Pierce BS, Darensbourg MY, Hall MB. Structural and Electronic Responses to the Three Redox Levels of Fe(NO)N 2 S 2 -Fe(NO) 2. Chemistry 2018; 24:16003-16008. [PMID: 30216575 DOI: 10.1002/chem.201804168] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Indexed: 11/10/2022]
Abstract
The nitrosylated diiron complexes, Fe2 (NO)3 , of this study are interpreted as a mono-nitrosyl Fe(NO) unit, MNIU, within an N2 S2 ligand field that serves as a metallodithiolate ligand to a dinitrosyl iron unit, DNIU. The cationic Fe(NO)N2 S2 ⋅Fe(NO)2 + complex, 1+ , of Enemark-Feltham electronic notation {Fe(NO)}7 -{Fe(NO)2 }9 , is readily obtained via myriad synthetic routes, and shown to be spin coupled and diamagnetic. Its singly and doubly reduced forms, {Fe(NO)}7 -{Fe(NO)2 }10 , 10 , and {Fe(NO)}8 -{Fe(NO)2 }10 , 1- , were isolated and characterized. While structural parameters of the DNIU are largely unaffected by redox levels, the MNIU readily responds; the neutral, S= 1 / 2 , complex, 10 , finds the extra electron density added into the DNIU affects the adjacent MNIU as seen by the decrease its Fe-N-O angle (from 171° to 149°). In contrast, addition of the second electron, now into the MNIU, returns the Fe-N-O angle to 171° in 1- . Compensating shifts in FeMNIU distances from the N2 S2 plane (from 0.518 to 0.551 to 0.851 Å) contribute to the stability of the bimetallic complex. These features are addressed by computational studies which indicate that the MNIU in 1- is a triplet-state {Fe(NO)}8 with strong spin polarization in the more linear FeNO unit. Magnetic susceptibility and parallel mode EPR results are consistent with the triplet state assignment.
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Affiliation(s)
- Pokhraj Ghosh
- Department of Chemistry, Texas A&M University, 3255 TAMU, College Station, TX, 77843, USA
| | - Shengda Ding
- Department of Chemistry, Texas A&M University, 3255 TAMU, College Station, TX, 77843, USA
| | - Manuel Quiroz
- Department of Chemistry, Texas A&M University, 3255 TAMU, College Station, TX, 77843, USA
| | - Nattamai Bhuvanesh
- Department of Chemistry, Texas A&M University, 3255 TAMU, College Station, TX, 77843, USA
| | - Chung-Hung Hsieh
- Department of Chemistry, Tamkang Univesrity, New Taipei City, 25157, Taiwan
| | - Philip M Palacios
- Department of Chemistry, University of Texas at Arlington, 503 W 3rd St, Arlington, TX, 76010, USA
| | - Brad S Pierce
- Department of Chemistry, University of Texas at Arlington, 503 W 3rd St, Arlington, TX, 76010, USA
| | - Marcetta Y Darensbourg
- Department of Chemistry, Texas A&M University, 3255 TAMU, College Station, TX, 77843, USA
| | - Michael B Hall
- Department of Chemistry, Texas A&M University, 3255 TAMU, College Station, TX, 77843, USA
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17
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Dey A, Confer AM, Vilbert AC, Moënne-Loccoz P, Lancaster KM, Goldberg DP. A Nonheme Sulfur-Ligated {FeNO} 6 Complex and Comparison with Redox-Interconvertible {FeNO} 7 and {FeNO} 8 Analogues. Angew Chem Int Ed Engl 2018; 57:13465-13469. [PMID: 30125450 DOI: 10.1002/anie.201806146] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Indexed: 01/23/2023]
Abstract
A nonheme {FeNO}6 complex, [Fe(NO)(N3PyS)]2+ , was synthesized by reversible, one-electron oxidation of an {FeNO}7 analogue. This complex completes the first known series of sulfur-ligated {FeNO}6-8 complexes. All three {FeNO}6-8 complexes are readily interconverted by one-electron oxidation/reduction. A comparison of spectroscopic data (UV/Vis, NMR, IR, Mössbauer, X-ray absorption) provides a complete picture of the electronic and structural changes that occur upon {FeNO}6 -{FeNO}8 interconversion. Dissociation of NO from the new {FeNO}6 complex is shown to be controlled by solvent, temperature, and photolysis, which is rare for a sulfur-ligated {FeNO}6 species.
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Affiliation(s)
- Aniruddha Dey
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Alex M Confer
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Avery C Vilbert
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Pierre Moënne-Loccoz
- Division of Environmental and Biomolecular Systems, Oregon Health and Science University, Portland, OR, 97239, USA
| | - Kyle M Lancaster
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853, USA
| | - David P Goldberg
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD, 21218, USA
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18
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Dey A, Confer AM, Vilbert AC, Moënne‐Loccoz P, Lancaster KM, Goldberg DP. A Nonheme Sulfur‐Ligated {FeNO}
6
Complex and Comparison with Redox‐Interconvertible {FeNO}
7
and {FeNO}
8
Analogues. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201806146] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Aniruddha Dey
- Department of Chemistry The Johns Hopkins University Baltimore MD 21218 USA
| | - Alex M. Confer
- Department of Chemistry The Johns Hopkins University Baltimore MD 21218 USA
| | - Avery C. Vilbert
- Department of Chemistry and Chemical Biology Cornell University Ithaca NY 14853 USA
| | - Pierre Moënne‐Loccoz
- Division of Environmental and Biomolecular Systems Oregon Health and Science University Portland OR 97239 USA
| | - Kyle M. Lancaster
- Department of Chemistry and Chemical Biology Cornell University Ithaca NY 14853 USA
| | - David P. Goldberg
- Department of Chemistry The Johns Hopkins University Baltimore MD 21218 USA
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19
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Speelman AL, White CJ, Zhang B, Alp EE, Zhao J, Hu M, Krebs C, Penner-Hahn J, Lehnert N. Non-heme High-Spin {FeNO} 6-8 Complexes: One Ligand Platform Can Do It All. J Am Chem Soc 2018; 140:11341-11359. [PMID: 30107126 DOI: 10.1021/jacs.8b06095] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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.
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Affiliation(s)
- Amy L Speelman
- Department of Chemistry and Department of Biophysics , University of Michigan , Ann Arbor , Michigan 48109-1055 , United States
| | - Corey J White
- Department of Chemistry and Department of Biophysics , University of Michigan , Ann Arbor , Michigan 48109-1055 , United States
| | - Bo Zhang
- Department of Chemistry and Department of Biochemistry and Molecular Biology , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - E Ercan Alp
- Advanced Photon Source , Argonne National Laboratory , Argonne , Illinois 60439 , United States
| | - Jiyong Zhao
- Advanced Photon Source , Argonne National Laboratory , Argonne , Illinois 60439 , United States
| | - Michael Hu
- Advanced Photon Source , Argonne National Laboratory , Argonne , Illinois 60439 , United States
| | - Carsten Krebs
- Department of Chemistry and Department of Biochemistry and Molecular Biology , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - James Penner-Hahn
- Department of Chemistry and Department of Biophysics , University of Michigan , Ann Arbor , Michigan 48109-1055 , United States
| | - Nicolai Lehnert
- Department of Chemistry and Department of Biophysics , University of Michigan , Ann Arbor , Michigan 48109-1055 , United States
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20
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Li F, Meyer RL, Carpenter SH, VanGelder LE, Nichols AW, Machan CW, Neidig ML, Matson EM. Nitric oxide activation facilitated by cooperative multimetallic electron transfer within an iron-functionalized polyoxovanadate-alkoxide cluster. Chem Sci 2018; 9:6379-6389. [PMID: 30310566 PMCID: PMC6115649 DOI: 10.1039/c8sc00987b] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 06/30/2018] [Indexed: 01/06/2023] Open
Abstract
Cooperative multimetallic electron transfer to accommodate substrate binding.
A series of NO-bound, iron-functionalized polyoxovanadate–alkoxide (FePOV–alkoxide) clusters have been synthesized, providing insight into the role of multimetallic constructs in the coordination and activation of a substrate. Upon exposure of the heterometallic cluster to NO, the vanadium-oxide metalloligand is oxidized by a single electron, shuttling the reducing equivalent to the {FeNO} subunit to form a {FeNO}7 species. Four NO-bound clusters with electronic distributions ranging from [VV3VIV2]{FeNO}7 to [VIV5]{FeNO}7 have been synthesized, and characterized via1H NMR, infrared, and electronic absorption spectroscopies. The ability of the FePOV–alkoxide cluster to store reducing equivalents in the metalloligand for substrate coordination and activation highlights the ultility of the metal-oxide scaffold as a redox reservoir.
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Affiliation(s)
- F Li
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , USA .
| | - R L Meyer
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , USA .
| | - S H Carpenter
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , USA .
| | - L E VanGelder
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , USA .
| | - A W Nichols
- Department of Chemistry , University of Virginia , Charlottesville , Virginia 22904-4319 , USA
| | - C W Machan
- Department of Chemistry , University of Virginia , Charlottesville , Virginia 22904-4319 , USA
| | - M L Neidig
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , USA .
| | - E M Matson
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , USA .
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21
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Hong S, Yan JJ, Karmalkar DG, Sutherlin KD, Kim J, Lee YM, Goo Y, Mascharak PK, Hedman B, Hodgson KO, Karlin KD, Solomon EI, Nam W. A mononuclear nonheme {FeNO} 6 complex: synthesis and structural and spectroscopic characterization. Chem Sci 2018; 9:6952-6960. [PMID: 30210769 PMCID: PMC6124912 DOI: 10.1039/c8sc01962b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 07/18/2018] [Indexed: 01/19/2023] Open
Abstract
While the synthesis and characterization of {FeNO}7,8,9 complexes have been well documented in heme and nonheme iron models, {FeNO}6 complexes have been less clearly understood. Herein, we report the synthesis and structural and spectroscopic characterization of mononuclear nonheme {FeNO}6 and iron(iii)-nitrito complexes bearing a tetraamido macrocyclic ligand (TAML), such as [(TAML)FeIII(NO)]- and [(TAML)FeIII(NO2)]2-, respectively. First, direct addition of NO(g) to [FeIII(TAML)]- results in the formation of [(TAML)FeIII(NO)]-, which is sensitive to moisture and air. The spectroscopic data of [(TAML)FeIII(NO)]-, such as 1H nuclear magnetic resonance and X-ray absorption spectroscopies, combined with computational study suggest the neutral nature of nitric oxide with a diamagnetic Fe center (S = 0). We also provide alternative pathways for the generation of [(TAML)FeIII(NO)]-, such as the iron-nitrite reduction triggered by protonation in the presence of ferrocene, which acts as an electron donor, and the photochemical iron-nitrite reduction. To the best of our knowledge, the present study reports the first photochemical nitrite reduction in nonheme iron models.
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Affiliation(s)
- Seungwoo Hong
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea . .,Department of Chemistry , Sookmyung Women's University , Seoul 04310 , Korea
| | - James J Yan
- Department of Chemistry , Stanford University , Stanford , California 94305 , USA .
| | - Deepika G Karmalkar
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea .
| | - Kyle D Sutherlin
- Department of Chemistry , Stanford University , Stanford , California 94305 , USA .
| | - Jin Kim
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea .
| | - Yong-Min Lee
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea .
| | - Yire Goo
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea .
| | - Pradip K Mascharak
- Department of Chemistry and Biochemistry , University of California , Santa Cruz , California 95064 , USA
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource , SLAC National Accelerator Laboratory , Stanford University , California 94025 , USA . ;
| | - Keith O Hodgson
- Department of Chemistry , Stanford University , Stanford , California 94305 , USA . .,Stanford Synchrotron Radiation Lightsource , SLAC National Accelerator Laboratory , Stanford University , California 94025 , USA . ;
| | - Kenneth D Karlin
- Department of Chemistry , The Johns Hopkins University , Baltimore , Maryland 21218 , USA .
| | - Edward I Solomon
- Department of Chemistry , Stanford University , Stanford , California 94305 , USA . .,Stanford Synchrotron Radiation Lightsource , SLAC National Accelerator Laboratory , Stanford University , California 94025 , USA . ;
| | - Wonwoo Nam
- Department of Chemistry and Nano Science , Ewha Womans University , Seoul 03760 , Korea . .,School of Chemistry and Chemical Engineering , Shaanxi Normal University , Xi'an 710119 , P. R. China
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22
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Van Stappen C, Lehnert N. Mechanism of N–N Bond Formation by Transition Metal–Nitrosyl Complexes: Modeling Flavodiiron Nitric Oxide Reductases. Inorg Chem 2018; 57:4252-4269. [DOI: 10.1021/acs.inorgchem.7b02333] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Casey Van Stappen
- Department of Chemistry and Department of Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Nicolai Lehnert
- Department of Chemistry and Department of Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
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23
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Reed CJ, Agapie T. Tetranuclear Fe Clusters with a Varied Interstitial Ligand: Effects on the Structure, Redox Properties, and Nitric Oxide Activation. Inorg Chem 2018; 56:13360-13367. [PMID: 29052979 DOI: 10.1021/acs.inorgchem.7b02114] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
A new series of tetranuclear Fe clusters displaying an interstitial μ4-F ligand was prepared for a comparison to previously reported μ4-O analogues. With a single nitric oxide (NO) coordinated as a reporter of small-molecule activation, the μ4-F clusters were characterized in five redox states, from FeII3{FeNO}8 to FeIII3{FeNO}7, with NO stretching frequencies ranging from 1680 to 1855 cm-1, respectively. Despite accessing more reduced states with an F- bridge, a two-electron reduction of the distal Fe centers is necessary for the μ4-F clusters to activate NO to the same degree as the μ4-O system; consequently, NO reactivity is observed at more positive potentials with μ4-O than μ4-F. Moreover, the μ4-O ligand better translates redox changes of remote metal centers to diatomic ligand activation. The implication for biological active sites is that the higher-charge bridging ligand is more effective in tuning cluster properties, including the involvement of remote metal centers, for small-molecule activation.
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Affiliation(s)
- Christopher J Reed
- Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States
| | - Theodor Agapie
- Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States
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24
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White CJ, Speelman AL, Kupper C, Demeshko S, Meyer F, Shanahan JP, Alp EE, Hu M, Zhao J, Lehnert N. The Semireduced Mechanism for Nitric Oxide Reduction by Non-Heme Diiron Complexes: Modeling Flavodiiron Nitric Oxide Reductases. J Am Chem Soc 2018; 140:2562-2574. [DOI: 10.1021/jacs.7b11464] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Corey J. White
- Department
of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Amy L. Speelman
- Department
of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Claudia Kupper
- Institut
für Anorganische Chemie, Universität Göttingen, Tammannstrasse
4, D-37077 Göttingen, Germany
| | - Serhiy Demeshko
- Institut
für Anorganische Chemie, Universität Göttingen, Tammannstrasse
4, D-37077 Göttingen, Germany
| | - Franc Meyer
- Institut
für Anorganische Chemie, Universität Göttingen, Tammannstrasse
4, D-37077 Göttingen, Germany
| | - James P. Shanahan
- Department
of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - E. Ercan Alp
- Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Michael Hu
- Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Jiyong Zhao
- Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Nicolai Lehnert
- Department
of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, United States
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25
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Confer AM, McQuilken AC, Matsumura H, Moënne-Loccoz P, Goldberg DP. A Nonheme, High-Spin {FeNO} 8 Complex that Spontaneously Generates N 2O. J Am Chem Soc 2017; 139:10621-10624. [PMID: 28749673 DOI: 10.1021/jacs.7b05549] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
One-electron reduction of [Fe(NO)-(N3PyS)]BF4 (1) leads to the production of the metastable nonheme {FeNO}8 complex, [Fe(NO)(N3PyS)] (3). Complex 3 is a rare example of a high-spin (S = 1) {FeNO}8 and is the first example, to our knowledge, of a mononuclear nonheme {FeNO}8 species that generates N2O. A second, novel route to 3 involves addition of Piloty's acid, an HNO donor, to an FeII precursor. This work provides possible new insights regarding the mechanism of nitric oxide reductases.
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Affiliation(s)
- Alex M Confer
- Department of Chemistry, Johns Hopkins University , Baltimore, Maryland 21218, United States
| | - Alison C McQuilken
- Department of Chemistry, Johns Hopkins University , Baltimore, Maryland 21218, United States
| | - Hirotoshi Matsumura
- Institute of Environmental Health, Oregon Health & Science University , Portland, Oregon 97239, United States
| | - Pierre Moënne-Loccoz
- Institute of Environmental Health, Oregon Health & Science University , Portland, Oregon 97239, United States
| | - David P Goldberg
- Department of Chemistry, Johns Hopkins University , Baltimore, Maryland 21218, United States
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26
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Fujisawa K, Soma S, Kurihara H, Dong HT, Bilodeau M, Lehnert N. A cobalt–nitrosyl complex with a hindered hydrotris(pyrazolyl)borate coligand: detailed electronic structure, and reactivity towards dioxygen. Dalton Trans 2017; 46:13273-13289. [DOI: 10.1039/c7dt01565h] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The cobalt–nitrosyl complex [Co(NO)(L3)] is supported by a highly hindered tridentate nitrogen ligand, hydrotris(3-tertiary butyl-5-isopropyl-1-pyrazolyl)borate (denoted as L3−), and shows a linear Co–N–O unit.
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Affiliation(s)
| | - Shoko Soma
- Department of Chemistry
- Ibaraki University
- Mito 310-8512
- Japan
| | | | - Hai T. Dong
- Department of Chemistry and Department of Biophysics
- University of Michigan
- Ann Arbor
- USA
| | - Max Bilodeau
- Department of Chemistry and Department of Biophysics
- University of Michigan
- Ann Arbor
- USA
| | - Nicolai Lehnert
- Department of Chemistry and Department of Biophysics
- University of Michigan
- Ann Arbor
- USA
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27
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Kindermann N, Schober A, Demeshko S, Lehnert N, Meyer F. Reductive Transformations of a Pyrazolate-Based Bioinspired Diiron–Dinitrosyl Complex. Inorg Chem 2016; 55:11538-11550. [DOI: 10.1021/acs.inorgchem.6b02080] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nicole Kindermann
- Institut für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstraße 4, 37077 Göttingen, Germany
| | - Anne Schober
- Institut für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstraße 4, 37077 Göttingen, Germany
| | - Serhiy Demeshko
- Institut für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstraße 4, 37077 Göttingen, Germany
| | - Nicolai Lehnert
- Department of Chemistry, The University of Michigan, 930 N. University
Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Franc Meyer
- Institut für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstraße 4, 37077 Göttingen, Germany
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28
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Chalkley MJ, Peters JC. A Triad of Highly Reduced, Linear Iron Nitrosyl Complexes: {FeNO}(8-10). Angew Chem Int Ed Engl 2016; 55:11995-8. [PMID: 27560776 PMCID: PMC5079689 DOI: 10.1002/anie.201605403] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 07/10/2016] [Indexed: 11/05/2022]
Abstract
Given the importance of Fe-NO complexes in both human biology and the global nitrogen cycle, there has been interest in understanding their diverse electronic structures. Herein a redox series of isolable iron nitrosyl complexes stabilized by a tris(phosphine)borane (TPB) ligand is described. These structurally characterized iron nitrosyl complexes reside in the following highly reduced Enemark-Feltham numbers: {FeNO}(8) , {FeNO}(9) , and {FeNO}(10) . These {FeNO}(8-10) compounds are each low-spin, and feature linear yet strongly activated nitric oxide ligands. Use of Mössbauer, EPR, NMR, UV/Vis, and IR spectroscopy, in conjunction with DFT calculations, provides insight into the electronic structures of this uncommon redox series of iron nitrosyl complexes. In particular, the data collectively suggest that {TPBFeNO}(8-10) are all remarkably covalent. This covalency is likely responsible for the stability of this system across three highly reduced redox states that correlate with unusually high Enemark-Feltham numbers.
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Affiliation(s)
- Matthew J Chalkley
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA, 91125, USA
| | - Jonas C Peters
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA, 91125, USA.
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29
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30
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Piñeiro-López L, Ortega-Villar N, Muñoz MC, Molnár G, Cirera J, Moreno-Esparza R, Ugalde-Saldívar VM, Bousseksou A, Ruiz E, Real JA. Electronic Structure Modulation in an Exceptionally Stable Non-Heme Nitrosyl Iron(II) Spin-Crossover Complex. Chemistry 2016; 22:12741-51. [DOI: 10.1002/chem.201601172] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Indexed: 11/11/2022]
Affiliation(s)
- Lucía Piñeiro-López
- Instituto de Ciencia Molecular (ICMol); Universidad de Valencia; 46980 Paterna Valencia Spain
| | - Norma Ortega-Villar
- Facultad de Química (UNAM); Edificio B.; Av. Universidad 3000, Coyoacán México D.F. 04510 México
| | - M. Carmen Muñoz
- Departamento de Física Aplicada; Universitat Politècnica de València; 46022 Valencia Spain
| | - Gábor Molnár
- LCC; CNRS & Université de Toulouse (UPS, INP); 205 route de Narbonne 31077 Toulouse France
| | - Jordi Cirera
- Departament de Química Inorgànica i Orgànica; Secció de Química Inorgànica; Institut de Recerca de Química Teòrica i Computacional; Universitat de Barcelona; Diagonal 645 Barcelona 08028 Spain
| | - Rafael Moreno-Esparza
- Facultad de Química (UNAM); Edificio B.; Av. Universidad 3000, Coyoacán México D.F. 04510 México
| | | | - Azzedine Bousseksou
- LCC; CNRS & Université de Toulouse (UPS, INP); 205 route de Narbonne 31077 Toulouse France
| | - Eliseo Ruiz
- Departament de Química Inorgànica i Orgànica; Secció de Química Inorgànica; Institut de Recerca de Química Teòrica i Computacional; Universitat de Barcelona; Diagonal 645 Barcelona 08028 Spain
| | - José A. Real
- Instituto de Ciencia Molecular (ICMol); Universidad de Valencia; 46980 Paterna Valencia Spain
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31
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Soma S, Van Stappen C, Kiss M, Szilagyi RK, Lehnert N, Fujisawa K. Distorted tetrahedral nickel-nitrosyl complexes: spectroscopic characterization and electronic structure. J Biol Inorg Chem 2016; 21:757-75. [DOI: 10.1007/s00775-016-1366-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 06/01/2016] [Indexed: 10/21/2022]
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32
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Kupper C, Rees JA, Dechert S, DeBeer S, Meyer F. Complete Series of {FeNO}(8), {FeNO}(7), and {FeNO}(6) Complexes Stabilized by a Tetracarbene Macrocycle. J Am Chem Soc 2016; 138:7888-98. [PMID: 27191681 DOI: 10.1021/jacs.6b00584] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Use of a macrocyclic tetracarbene ligand, which is topologically reminiscent of tetrapyrrole macrocycles though electronically distinct, has allowed for the isolation, X-ray crystallographic characterization and comprehensive spectroscopic investigation of a complete set of {FeNO}(x) complexes (x = 6, 7, 8). Electrochemical reduction, or chemical reduction with CoCp2, of the {FeNO}(7) complex 1 leads to the organometallic {FeNO}(8) species 2. Its crystallographic structure determination is the first for a nonheme iron nitroxyl {FeNO}(8) and has allowed to identify structural trends among the series of {FeNO}(x) complexes. Combined experimental data including (57)Fe Mössbauer, IR, UV-vis-NIR, NMR and Kβ X-ray emission spectroscopies in concert with DFT calculations suggest a largely metal centered reduction of 1 to form the low spin (S = 0) {FeNO}(8) species 2. The very strong σ-donor character of the tetracarbene ligand imparts unusual properties and spectroscopic signatures such as low (57)Fe Mössbauer isomer shifts and linear Fe-N-O units with high IR stretching frequencies for the NO ligand. The observed metal-centered reduction leads to distinct reactivity patterns of the {FeNO}(8) species. In contrast to literature reported {FeNO}(8) complexes, 2 does not undergo NO protonation under strictly anaerobic conditions. Only in the presence of both dioxygen and protons is rapid and clean oxidation to the {FeNO}(7) complex 1 observed. While 1 is stable toward dioxygen, its reaction with dioxygen under NO atmosphere forms the {FeNO}(6)(ONO) complex 3 that features an unusual O-nitrito ligand trans to the NO. 3 is a rare example of a nonheme octahedral {FeNO}(6) complex. Its electrochemical or chemical reduction triggers dissociation of the O-nitrito ligand and sequential formation of the {FeNO}(7) and {FeNO}(8) compounds 1 and 2. A consistent electronic structure picture has been derived for these unique organometallic variants of the key bioinorganic {FeNO}(x) functional units.
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Affiliation(s)
- Claudia Kupper
- Institut für Anorganische Chemie, Georg-August-Universität , Tammannstrasse 4, D-37077 Göttingen, Germany
| | - Julian A Rees
- Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany.,Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195-1700, United States
| | - Sebastian Dechert
- Institut für Anorganische Chemie, Georg-August-Universität , Tammannstrasse 4, D-37077 Göttingen, Germany
| | - Serena DeBeer
- Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany.,Department of Chemistry and Biochemistry, Cornell University , Ithaca, New York 14853, United States
| | - Franc Meyer
- Institut für Anorganische Chemie, Georg-August-Universität , Tammannstrasse 4, D-37077 Göttingen, Germany
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33
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Conradie J, Ghosh A. Metalloporphyrin–Nitroxyl Interactions: The Low-Energy States of Reduced Manganese, Iron, and Cobalt Porphyrin Nitrosyls. J Phys Chem B 2016; 120:4972-9. [DOI: 10.1021/acs.jpcb.6b04983] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jeanet Conradie
- Department of Chemistry and Center for Theoretical and
Computational Chemistry, UiT − The Arctic University of Norway, 9037 Tromsø, Norway
- Department of Chemistry, University of the Free State, 9300 Bloemfontein, Republic of South Africa
| | - Abhik Ghosh
- Department of Chemistry and Center for Theoretical and
Computational Chemistry, UiT − The Arctic University of Norway, 9037 Tromsø, Norway
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34
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Speelman AL, Zhang B, Silakov A, Skodje KM, Alp EE, Zhao J, Hu MY, Kim E, Krebs C, Lehnert N. Unusual Synthetic Pathway for an {Fe(NO)2}9 Dinitrosyl Iron Complex (DNIC) and Insight into DNIC Electronic Structure via Nuclear Resonance Vibrational Spectroscopy. Inorg Chem 2016; 55:5485-501. [DOI: 10.1021/acs.inorgchem.6b00510] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Amy L. Speelman
- Department
of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Bo Zhang
- Department of Chemistry and Department of Biochemistry and Molecular
Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Alexey Silakov
- Department of Chemistry and Department of Biochemistry and Molecular
Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Kelsey M. Skodje
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - E. Ercan Alp
- Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Jiyong Zhao
- Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Michael Y. Hu
- Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Eunsuk Kim
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Carsten Krebs
- Department of Chemistry and Department of Biochemistry and Molecular
Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Nicolai Lehnert
- Department
of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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35
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Speelman AL, Zhang B, Krebs C, Lehnert N. Structural and Spectroscopic Characterization of a High-Spin {FeNO}(6) Complex with an Iron(IV)-NO(-) Electronic Structure. Angew Chem Int Ed Engl 2016; 55:6685-8. [PMID: 27101151 DOI: 10.1002/anie.201601742] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Indexed: 11/10/2022]
Abstract
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 TMG3 tren 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.
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Affiliation(s)
- Amy L Speelman
- Department of Chemistry, University of Michigan, 930 N University Avenue, Ann Arbor, MI, 48109, USA
| | - Bo Zhang
- Department of Chemistry, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Carsten Krebs
- Department of Chemistry, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Nicolai Lehnert
- Department of Chemistry, University of Michigan, 930 N University Avenue, Ann Arbor, MI, 48109, USA.
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36
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Speelman AL, Zhang B, Krebs C, Lehnert N. Structural and Spectroscopic Characterization of a High‐Spin {FeNO}
6
Complex with an Iron(IV)−NO
−
Electronic Structure. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201601742] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Amy L. Speelman
- Department of Chemistry University of Michigan 930 N University Avenue Ann Arbor MI 48109 USA
| | - Bo Zhang
- Department of Chemistry, Department of Biochemistry and Molecular Biology The Pennsylvania State University University Park PA 16802 USA
| | - Carsten Krebs
- Department of Chemistry, Department of Biochemistry and Molecular Biology The Pennsylvania State University University Park PA 16802 USA
| | - Nicolai Lehnert
- Department of Chemistry University of Michigan 930 N University Avenue Ann Arbor MI 48109 USA
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37
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Lionetti D, de Ruiter G, Agapie T. A trans-Hyponitrite Intermediate in the Reductive Coupling and Deoxygenation of Nitric Oxide by a Tricopper-Lewis Acid Complex. J Am Chem Soc 2016; 138:5008-11. [PMID: 27028157 DOI: 10.1021/jacs.6b01083] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The reduction of nitric oxide (NO) to nitrous oxide (N2O) is a process relevant to biological chemistry as well as to the abatement of certain environmental pollutants. One of the proposed key intermediates in NO reduction is hyponitrite (N2O2(2-)), the product of reductive coupling of two NO molecules. We report the reductive coupling of NO by an yttrium-tricopper complex generating a trans-hyponitrite moiety supported by two μ-O-bimetallic (Y,Cu) cores, a previously unreported coordination mode. Reaction of the hyponitrite species with Brønsted acids leads to the generation of N2O, demonstrating the viability of the hyponitrite complex as an intermediate in NO reduction to N2O. The additional reducing equivalents stored in each tricopper unit are employed in a subsequent step for N2O reduction to N2, for an overall (partial) conversion of NO to N2. The combination of Lewis acid and multiple redox active metals facilitates this four electron conversion via an isolable hyponitrite intermediate.
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Affiliation(s)
- Davide Lionetti
- Division of Chemistry and Chemical Engineering, California Institute of Technology , 1200 East California Boulevard, MC 127-72, Pasadena, California 91125, United States
| | - Graham de Ruiter
- Division of Chemistry and Chemical Engineering, California Institute of Technology , 1200 East California Boulevard, MC 127-72, Pasadena, California 91125, United States
| | - Theodor Agapie
- Division of Chemistry and Chemical Engineering, California Institute of Technology , 1200 East California Boulevard, MC 127-72, Pasadena, California 91125, United States
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38
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Yang W, Chen X, Su H, Fang W, Zhang Y. The fluorescence regulation mechanism of the paramagnetic metal in a biological HNO sensor. Chem Commun (Camb) 2016; 51:9616-9. [PMID: 25947080 DOI: 10.1039/c5cc00787a] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Paramagnetic metals are frequently used to regulate fluorescence emissions in chemical and biological probes. Accurate quantum calculations offer the first regulation theory that quenching is through the competitive nonradiative decay of the mixed fluorophore/metal (3)ππ*/dd state isoenergetic to the fluorophore-localized (1)ππ* state.
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Affiliation(s)
- Wenjing Yang
- Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education, Department of Chemistry, Beijing Normal University, Xin-wai-da-jie No. 19, Beijing, 100875, People's Republic of China.
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39
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Kundakarla N, Lindeman S, Rahman MH, Ryan MD. X-ray Structure and Properties of the Ferrous Octaethylporphyrin Nitroxyl Complex. Inorg Chem 2016; 55:2070-5. [DOI: 10.1021/acs.inorgchem.5b02384] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Nagabhushanam Kundakarla
- Marquette University, Chemistry Department, P.O. Box 1881, Milwaukee, Wisconsin 53201, United States
| | - Sergey Lindeman
- Marquette University, Chemistry Department, P.O. Box 1881, Milwaukee, Wisconsin 53201, United States
| | - Md. Hafiz Rahman
- Marquette University, Chemistry Department, P.O. Box 1881, Milwaukee, Wisconsin 53201, United States
| | - Michael D. Ryan
- Marquette University, Chemistry Department, P.O. Box 1881, Milwaukee, Wisconsin 53201, United States
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40
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Caramori GF, Ortolan AO, Parreira RL, da Silva EH. Ruthenium nitrosyl complexes containing pyridine-functionalized carbenes – A theoretical insight. J Organomet Chem 2015. [DOI: 10.1016/j.jorganchem.2015.08.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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41
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de Ruiter G, Thompson NB, Lionetti D, Agapie T. Nitric oxide activation by distal redox modulation in tetranuclear iron nitrosyl complexes. J Am Chem Soc 2015; 137:14094-106. [PMID: 26390375 DOI: 10.1021/jacs.5b07397] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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 μ4-oxide moiety. Electrochemical studies of complex [LFe3(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 N2O formation performed by the more electron-rich cluster.
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Affiliation(s)
- Graham de Ruiter
- Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States
| | - Niklas B Thompson
- Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States
| | - Davide Lionetti
- Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States
| | - Theodor Agapie
- Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States
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42
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Lehnert N, Peters JC. Preface for Small-Molecule Activation: From Biological Principles to Energy Applications. Part 2: Small Molecules Related to the Global Nitrogen Cycle. Inorg Chem 2015; 54:9229-33. [DOI: 10.1021/acs.inorgchem.5b02124] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Nicolai Lehnert
- Department of Chemistry, The University of Michigan, 930 N. University, Ann Arbor, Michigan 48109, United States
| | - Jonas C. Peters
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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43
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Foi A, Di Salvo F, Doctorovich F, Roy TG, Stirnat K, Biewer C, Klein A. Tracing the Iron Nitrosyl Complex [Fe(2,2′‐bipyridine)(CN)
3
(NO)]
–. Eur J Inorg Chem 2015. [DOI: 10.1002/ejic.201403145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Ana Foi
- Departamento de Química Inorgánica, Analítica, y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, INQUIMAE‐CONICET, Ciudad Universitaria, Pabellón 2, Piso 3, C1428EHA Buenos Aires, Argentina
| | - Florencia Di Salvo
- Departamento de Química Inorgánica, Analítica, y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, INQUIMAE‐CONICET, Ciudad Universitaria, Pabellón 2, Piso 3, C1428EHA Buenos Aires, Argentina
| | - Fabio Doctorovich
- Departamento de Química Inorgánica, Analítica, y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, INQUIMAE‐CONICET, Ciudad Universitaria, Pabellón 2, Piso 3, C1428EHA Buenos Aires, Argentina
| | | | - Kathrin Stirnat
- Universität zu Köln, Institut für Anorganische Chemie, Greinstraße 6, 50939 Köln, http://www.klein.uni‐koeln.de/
| | - Christian Biewer
- Universität zu Köln, Institut für Anorganische Chemie, Greinstraße 6, 50939 Köln, http://www.klein.uni‐koeln.de/
| | - Axel Klein
- Universität zu Köln, Institut für Anorganische Chemie, Greinstraße 6, 50939 Köln, http://www.klein.uni‐koeln.de/
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Kaim W. Complete and Partial Electron Transfer Involving Coordinated NOx. ADVANCES IN INORGANIC CHEMISTRY 2015. [DOI: 10.1016/bs.adioch.2014.10.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Khatua S, Majumdar A. Flavodiiron nitric oxide reductases: Recent developments in the mechanistic study and model chemistry for the catalytic reduction of NO. J Inorg Biochem 2015; 142:145-53. [DOI: 10.1016/j.jinorgbio.2014.09.018] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 09/26/2014] [Accepted: 09/29/2014] [Indexed: 11/24/2022]
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Bari SE, Olabe JA, Slep LD. Three Redox States of Metallonitrosyls in Aqueous Solution. ADVANCES IN INORGANIC CHEMISTRY 2015. [DOI: 10.1016/bs.adioch.2014.10.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Harrop TC. New Insights on {FeNO}n (n=7, 8) Systems as Enzyme Models and HNO Donors. ADVANCES IN INORGANIC CHEMISTRY 2015. [DOI: 10.1016/bs.adioch.2014.10.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Doctorovich F, Bikiel DE, Pellegrino J, Suárez SA, Martí MA. Reactions of HNO with metal porphyrins: underscoring the biological relevance of HNO. Acc Chem Res 2014; 47:2907-16. [PMID: 25238532 DOI: 10.1021/ar500153c] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Azanone ((1)HNO, nitroxyl) shows interesting yet poorly understood chemical and biological effects. HNO has some overlapping properties with nitric oxide (NO), sharing its biological reactivity toward heme proteins, thiols, and oxygen. Despite this similarity, HNO and NO show significantly different pharmacological effects. The high reactivity of HNO means that studies must rely on the use of donor molecules such as trioxodinitrate (Angeli's salt). It has been suggested that azanone could be an intermediate in several reactions and that it may be an enzymatically produced signaling molecule. The inherent difficulty in detecting its presence unequivocally prevents evidence from yielding definite answers. On the other hand, metalloporphyrins are widely used as chemical models of heme proteins, providing us with invaluable tools for the study of the coordination chemistry of small molecules, like NO, CO, and O2. Studies with transition metal porphyrins have shown diverse mechanistic, kinetic, structural, and reactive aspects related to the formation of nitrosyl complexes. Porphyrins are also widely used in technical applications, especially when coupled to a surface, where they can be used as electrochemical gas sensors. Given their versatility, they have not escaped their role as key players in chemical studies involving HNO. This Account presents the research performed during the last 10 years in our group concerning azanone reactions with iron, manganese, and cobalt porphyrins. We begin by describing their HNO trapping capabilities, which result in formation of the corresponding nitrosyl complexes. Kinetic and mechanistic studies of these reactions show two alternative operating mechanisms: reaction of the metal center with HNO or with the donor. Moreover, we have also shown that azanone can be stabilized by coordination to iron porphyrins using electron-attracting substituents attached to the porphyrin ring, which balance the negatively charged NO¯. Second, we describe an electrochemical HNO sensing device based on the covalent attachment of a cobalt porphyrin to gold. A surface effect affects the redox potentials and allows discrimination between HNO and NO. The reaction with the former is fast, efficient, and selective, lacking spurious signals due to the presence of reactive nitrogen and oxygen species. The sensor is both biologically compatible and highly sensitive (nanomolar). This time-resolved detection allows kinetic analysis of reactions producing HNO. The sensor thus offers excellent opportunities to be used in experiments looking for HNO. As examples, we present studies concerning (a) HNO donation capabilities of new HNO donors as assessed by the sensor, (b) HNO detection as an intermediate in O atom abstraction to nitrite by phosphines, and (c) NO to HNO interconversion mediated by alcohols and thiols. Finally, we briefly discuss the key experiments required to demonstrate endogenous HNO formation to be done in the near future, involving the in vivo use of the HNO sensing device.
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Affiliation(s)
- Fabio Doctorovich
- Departamento de Química Inorgánica,
Analítica
y Química Física/INQUIMAE-CONICET and †Departamento de Química
Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II (1428), Buenos Aires, Argentina
| | - Damian E. Bikiel
- Departamento de Química Inorgánica,
Analítica
y Química Física/INQUIMAE-CONICET and †Departamento de Química
Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II (1428), Buenos Aires, Argentina
| | - Juan Pellegrino
- Departamento de Química Inorgánica,
Analítica
y Química Física/INQUIMAE-CONICET and †Departamento de Química
Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II (1428), Buenos Aires, Argentina
| | - Sebastián A. Suárez
- Departamento de Química Inorgánica,
Analítica
y Química Física/INQUIMAE-CONICET and †Departamento de Química
Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II (1428), Buenos Aires, Argentina
| | - Marcelo A. Martí
- Departamento de Química Inorgánica,
Analítica
y Química Física/INQUIMAE-CONICET and †Departamento de Química
Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II (1428), Buenos Aires, Argentina
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Li J, Banerjee A, Pawlak PL, Brennessel WW, Chavez FA. Highest Recorded N–O Stretching Frequency for 6-Coordinate {Fe-NO}7 Complexes: An Iron Nitrosyl Model for His3 Active Sites. Inorg Chem 2014; 53:5414-6. [DOI: 10.1021/ic500558j] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Jia Li
- Department of Chemistry, Oakland University, Rochester, Michigan 48309-4477, United States
| | - Atanu Banerjee
- Department of Chemistry, Oakland University, Rochester, Michigan 48309-4477, United States
| | - Piotr L. Pawlak
- Department of Chemistry, Oakland University, Rochester, Michigan 48309-4477, United States
| | - William W. Brennessel
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, United States
| | - Ferman A. Chavez
- Department of Chemistry, Oakland University, Rochester, Michigan 48309-4477, United States
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Speelman AL, Lehnert N. Heme versus non-heme iron-nitroxyl {FeN(H)O}⁸ complexes: electronic structure and biologically relevant reactivity. Acc Chem Res 2014; 47:1106-16. [PMID: 24555413 DOI: 10.1021/ar400256u] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Researchers have completed extensive studies on heme and non-heme iron-nitrosyl complexes, which are labeled {FeNO}(7) in the Enemark-Feltham notation, but they have had very limited success in producing corresponding, one-electron reduced, {FeNO}(8) complexes where a nitroxyl anion (NO(-)) is formally bound to an iron(II) center. These complexes, and their protonated iron(II)-NHO analogues, are proposed key intermediates in nitrite (NO2(-)) and nitric oxide (NO) reducing enzymes in bacteria and fungi. In addition, HNO is known to have a variety of physiological effects, most notably in the cardiovascular system. HNO may also serve as a signaling molecule in mammals. For these functions, iron-containing proteins may mediate the production of HNO and serve as receptors for HNO in vivo. In this Account, we highlight recent key advances in the preparation, spectroscopic characterization, and reactivity of ferrous heme and non-heme nitroxyl (NO(-)/HNO) complexes that have greatly enhanced our understanding of the potential biological roles of these species. Low-spin (ls) heme {FeNO}(7) complexes (S = 1/2) can be reversibly reduced to the corresponding {FeNO}(8) species, which are stable, diamagnetic compounds. Because the reduction is ligand (NO) centered in these cases, it occurs at extremely negative redox potentials that are at the edge of the biologically feasible range. Interestingly, the electronic structures of ls-{FeNO}(7) and ls-{FeNO}(8) species are strongly correlated with very similar frontier molecular orbitals (FMOs) and thermodynamically strong Fe-NO bonds. In contrast, high-spin (hs) non-heme {FeNO}(7) complexes (S = 3/2) can be reduced at relatively mild redox potentials. Here, the reduction is metal-centered and leads to a paramagnetic (S = 1) {FeNO}(8) complex. The increased electron density at the iron center in these species significantly decreases the covalency of the Fe-NO bond, making the reduced complexes highly reactive. In the absence of steric bulk, monomeric high-spin {FeNO}(8) complexes decompose rapidly. Notably, in a recently prepared, dimeric [{FeNO}(7)]2 species, we observed that reduction leads to rapid N-N bond formation and N2O generation, which directly models the reactivity of flavodiiron NO reductases (FNORs). We have also made key progress in the preparation and stabilization of corresponding HNO complexes, {FeNHO}(8), using both heme and non-heme ligand sets. In both cases, we have taken advantage of sterically bulky coligands to stabilize these species. ls-{FeNO}(8) complexes are basic and easily form corresponding ls-{FeNHO}(8) species, which, however, decompose rapidly via disproportionation and H2 release. Importantly, we recently showed that we can suppress this reaction via steric protection of the bound HNO ligand. As a result, we have demonstrated that ls-{FeNHO}(8) model complexes are stable and amenable to spectroscopic characterization. Neither ls-{FeNO}(8) nor ls-{FeNHO}(8) model complexes are active for N-N coupling, and hence, seem unsuitable as reactive intermediates in nitric oxide reductases (NORs). Hs-{FeNO}(8) complexes are more basic than their hs-{FeNO}(7) precursors, but their electronic structure and reactivity is not as well characterized.
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Affiliation(s)
- Amy L. Speelman
- Department
of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Nicolai Lehnert
- Department
of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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