1
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Skubi KL, Hooper RX, Mercado BQ, Bollmeyer MM, MacMillan SN, Lancaster KM, Holland PL. Iron Complexes of a Proton-Responsive SCS Pincer Ligand with a Sensitive Electronic Structure. Inorg Chem 2022; 61:1644-1658. [PMID: 34986307 PMCID: PMC8792349 DOI: 10.1021/acs.inorgchem.1c03499] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Sulfur/carbon/sulfur pincer ligands have an interesting combination of strong-field and weak-field donors, a coordination environment that is also present in the nitrogenase active site. Here, we explore the electronic structures of iron(II) and iron(III) complexes with such a pincer ligand, bearing a monodentate phosphine, thiolate S donor, amide N donor, ammonia, or CO. The ligand scaffold features a proton-responsive thioamide site, and the protonation state of the ligand greatly influences the reduction potential of iron in the phosphine complex. The N-H bond dissociation free energy, derived from the Bordwell equation, is 56 ± 2 kcal/mol. Electron paramagnetic resonance (EPR) spectroscopy and superconducting quantum interference device (SQUID) magnetometry measurements show that the iron(III) complexes with S and N as the fourth donors have an intermediate spin (S = 3/2) ground state with a large zero field splitting, and X-ray absorption spectra show a high Fe-S covalency. The Mössbauer spectrum changes drastically with the position of a nearby alkali metal cation in the iron(III) amido complex, and density functional theory calculations explain this phenomenon through a change between having the doubly occupied orbital as dz2 or dyz, as the former is more influenced by the nearby positive charge.
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Affiliation(s)
- Kazimer L. Skubi
- Department of Chemistry, Yale University, New Haven, Connecticut 06511
| | - Reagan X. Hooper
- Department of Chemistry, Yale University, New Haven, Connecticut 06511
| | | | - Melissa M. Bollmeyer
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853
| | - Samantha N. MacMillan
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853
| | - Kyle M. Lancaster
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853
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2
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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: 101] [Impact Index Per Article: 33.7] [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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3
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Toledo S, Yan Poon PC, Gleaves M, Rees J, Rogers DM, Kaminsky W, Kovacs JA. Increasing reactivity by incorporating π-acceptor ligands into coordinatively unsaturated thiolate-ligated iron(II) complexes. Inorganica Chim Acta 2021; 524. [PMID: 34305163 DOI: 10.1016/j.ica.2021.120422] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Reported herein is the structural, spectroscopic, redox, and reactivity properties of a series of iron complexes containing both a π-donating thiolate, and π-accepting N-heterocycles in the coordination sphere, in which we systematically vary the substituents on the N-heterocycle, the size of the N-heterocycle, and the linker between the imine nitrogen and tertiary amine nitrogen. In contrast to our primary amine/thiolate-ligated Fe(II) complex, [FeII(SMe2N4(tren))]+ (1), the Fe(II) complexes reported herein are intensely colored, allowing us to visually monitor reactivity. Ferrous complexes with R = H substituents in the 6-position of the pyridines, [FeII(SMe2N4(6-H-DPPN)]+ (6) and [FeII(SMe2N4(6-H-DPEN))(MeOH)]+ (8-MeOH) are shown to readily bind neutral ligands, and all of the Fe(II) complexes are shown to bind anionic ligands regardless of steric congestion. This reactivity is in contrast to 1 and is attributed to an increased metal ion Lewis acidity assessed via aniodic redox potentials, Ep,a, caused by the π-acid ligands. Thermodynamic parameters (ΔH, ΔS) for neutral ligand binding were obtained from T-dependent equilibrium constants. All but the most sterically congested complex, [FeII(SMe2N4(6-Me-DPPN)]+ (5), react with O2. In contrast to our Mn(II)-analogues, dioxygen intermediates are not observed. Rates of formation of the final mono oxo-bridged products were assessed via kinetics and shown to be inversely dependent on redox potentials, Ep,a, consistent with a mechanism involving electron transfer.
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Affiliation(s)
- Santiago Toledo
- The Department of Chemistry, University of Washington, Box 351700 Seattle, WA 98195-1700, United States
| | - Penny Chaau Yan Poon
- The Department of Chemistry, University of Washington, Box 351700 Seattle, WA 98195-1700, United States
| | - Morgan Gleaves
- The Department of Chemistry, University of Washington, Box 351700 Seattle, WA 98195-1700, United States
| | - Julian Rees
- The Department of Chemistry, University of Washington, Box 351700 Seattle, WA 98195-1700, United States
| | - Dylan M Rogers
- The Department of Chemistry, University of Washington, Box 351700 Seattle, WA 98195-1700, United States
| | - Werner Kaminsky
- The Department of Chemistry, University of Washington, Box 351700 Seattle, WA 98195-1700, United States
| | - Julie A Kovacs
- The Department of Chemistry, University of Washington, Box 351700 Seattle, WA 98195-1700, United States
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4
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Gordon JB, McGale JP, Siegler MA, Goldberg DP. Proton-Coupled Electron-Transfer Reactivity Controls Iron versus Sulfur Oxidation in Nonheme Iron-Thiolate Complexes. Inorg Chem 2021; 60:6255-6265. [PMID: 33872005 DOI: 10.1021/acs.inorgchem.0c03779] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reaction of the five-coordinate FeII(N4S) complexes, [FeII(iPr3TACN)(abtX)](OTf) (abt = aminobenzenethiolate, X = H, CF3), with a one-electron oxidant and an appropriate base leads to net H atom loss, generating new FeIII(iminobenzenethiolate) complexes that were characterized by single-crystal X-ray diffraction (XRD), as well as UV-vis, EPR, and Mössbauer spectroscopies. The spectroscopic data indicate that the iminobenzenethiolate complexes have S = 3/2 ground states. In the absence of a base, oxidation of the FeII(abt) complexes leads to disulfide formation instead of oxidation at the metal center. Bracketing studies with separated proton-coupled electron-transfer (PCET) reagents show that the FeII(aminobenzenethiolate) and FeIII(iminobenzenethiolate) forms are readily interconvertible by H+/e- transfer and provide a measure of the bond dissociation free energy (BDFE) for the coordinated N-H bond between 64 and 69 kcal mol-1. This work shows that coordination to the iron center causes a dramatic weakening of the N-H bond and that Fe- versus S-oxidation in a nonheme iron complex can be controlled by the protonation state of an ancillary amino donor.
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Affiliation(s)
- Jesse B Gordon
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Jeremy P McGale
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Maxime A Siegler
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - David P Goldberg
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
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5
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Leipzig BK, Rees JA, Kowalska JK, Theisen RM, Kavčič M, Poon PCY, Kaminsky W, DeBeer S, Bill E, Kovacs JA. How Do Ring Size and π-Donating Thiolate Ligands Affect Redox-Active, α-Imino-N-heterocycle Ligand Activation? Inorg Chem 2018; 57:1935-1949. [PMID: 29411979 PMCID: PMC8312276 DOI: 10.1021/acs.inorgchem.7b02748] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Considerable effort has been devoted to the development of first-row transition-metal catalysts containing redox-active imino-pyridine ligands that are capable of storing multiple reducing equivalents. This property allows abundant and inexpensive first-row transition metals, which favor sequential one-electron redox processes, to function as competent catalysts in the concerted two-electron reduction of substrates. Herein we report the syntheses and characterization of a series of iron complexes that contain both π-donating thiolate and π-accepting (α-imino)-N-heterocycle redox-active ligands, with progressively larger N-heterocycle rings (imidazole, pyridine, and quinoline). A cooperative interaction between these complementary redox-active ligands is shown to dictate the properties of these complexes. Unusually intense charge-transfer (CT) bands, and intraligand metrical parameters, reminiscent of a reduced (α-imino)-N-heterocycle ligand (L•-), initially suggested that the electron-donating thiolate had reduced the N-heterocycle. Sulfur K-edge X-ray absorption spectroscopic (XAS) data, however, provides evidence for direct communication, via backbonding, between the thiolate sulfur and the formally orthogonal (α-imino)-N-heterocycle ligand π*-orbitals. DFT calculations provide evidence for extensive delocalization of bonds over the sulfur, iron, and (α-imino)-N-heterocycle, and TD-DFT shows that the intense optical CT bands involve transitions between a mixed Fe/S donor, and (α-imino)-N-heterocycle π*-acceptor orbital. The energies and intensities of the optical and S K-edge pre-edge XAS transitions are shown to correlate with N-heterocycle ring size, as do the redox potentials. When the thiolate is replaced with a thioether, or when the low-spin S = 0 Fe(II) is replaced with a high-spin S = 3/2 Co(II), the N-heterocycle ligand metrical parameters and electronic structure do not change relative to the neutral L0 ligand. With respect to the development of future catalysts containing redox-active ligands, the energy cost of storing reducing equivalents is shown to be lowest when a quinoline, as opposed to imidazole or pyridine, is incorporated into the ligand backbone of the corresponding Fe complex.
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Affiliation(s)
- Benjamin K. Leipzig
- The Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
| | - Julian A. Rees
- The Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
| | - Joanna K. Kowalska
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34–36, D–45470 Mülheim an der Ruhr, Germany
| | - Roslyn M. Theisen
- The Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
| | | | | | - Werner Kaminsky
- The Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
| | - Serena DeBeer
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34–36, D–45470 Mülheim an der Ruhr, Germany
| | - Eckhard Bill
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34–36, D–45470 Mülheim an der Ruhr, Germany
| | - Julie A. Kovacs
- The Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States
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6
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Çakmak D, Çakran S, Yalçinkaya S, Demetgül C. Synthesis of salen-type Schiff base metal complexes, electropolymerization on graphite electrode surface and investigation of electrocatalytic effects. J Electroanal Chem (Lausanne) 2018. [DOI: 10.1016/j.jelechem.2017.11.058] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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7
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Wu Y, Chang C, Wang C, Hsieh C, Horng Y. C=N Bond Activation and Hydration by an Iron(III) Complex with Asymmetric Sulfur Oxygenation. Eur J Inorg Chem 2017. [DOI: 10.1002/ejic.201601565] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Yun‐Ru Wu
- Department of Chemistry National Changhua University of Education 50058 Changhua Taiwan
| | - Chia‐Ming Chang
- Department of Chemistry National Changhua University of Education 50058 Changhua Taiwan
| | - Chia‐Chi Wang
- Department of Chemistry National Changhua University of Education 50058 Changhua Taiwan
| | - Chang‐Chih Hsieh
- Department of Chemistry National Changhua University of Education 50058 Changhua Taiwan
| | - Yih‐Chern Horng
- Department of Chemistry National Changhua University of Education 50058 Changhua Taiwan
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8
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Villar-Acevedo G, Lugo-Mas P, Blakely MN, Rees JA, Ganas AS, Hanada EM, Kaminsky W, Kovacs JA. Metal-Assisted Oxo Atom Addition to an Fe(III) Thiolate. J Am Chem Soc 2016; 139:119-129. [PMID: 28033001 DOI: 10.1021/jacs.6b03512] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Cysteinate oxygenation is intimately tied to the function of both cysteine dioxygenases (CDOs) and nitrile hydratases (NHases), and yet the mechanisms by which sulfurs are oxidized by these enzymes are unknown, in part because intermediates have yet to be observed. Herein, we report a five-coordinate bis-thiolate ligated Fe(III) complex, [FeIII(S2Me2N3(Pr,Pr))]+ (2), that reacts with oxo atom donors (PhIO, IBX-ester, and H2O2) to afford a rare example of a singly oxygenated sulfenate, [FeIII(η2-SMe2O)(SMe2)N3(Pr,Pr)]+ (5), resembling both a proposed intermediate in the CDO catalytic cycle and the essential NHase Fe-S(O)Cys114 proposed to be intimately involved in nitrile hydrolysis. Comparison of the reactivity of 2 with that of a more electron-rich, crystallographically characterized derivative, [FeIIIS2Me2NMeN2amide(Pr,Pr)]- (8), shows that oxo atom donor reactivity correlates with the metal ion's ability to bind exogenous ligands. Density functional theory calculations suggest that the mechanism of S-oxygenation does not proceed via direct attack at the thiolate sulfurs; the average spin-density on the thiolate sulfurs is approximately the same for 2 and 8, and Mulliken charges on the sulfurs of 8 are roughly twice those of 2, implying that 8 should be more susceptible to sulfur oxidation. Carboxamide-ligated 8 is shown to be unreactive towards oxo atom donors, in contrast to imine-ligated 2. Azide (N3-) is shown to inhibit sulfur oxidation with 2, and a green intermediate is observed, which then slowly converts to sulfenate-ligated 5. This suggests that the mechanism of sulfur oxidation involves initial coordination of the oxo atom donor to the metal ion. Whether the green intermediate is an oxo atom donor adduct, Fe-O═I-Ph, or an Fe(V)═O remains to be determined.
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Affiliation(s)
- Gloria Villar-Acevedo
- The Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195-1700, United States
| | - Priscilla Lugo-Mas
- The Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195-1700, United States
| | - Maike N Blakely
- The Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195-1700, United States
| | - Julian A Rees
- The Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195-1700, United States
| | - Abbie S Ganas
- The Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195-1700, United States
| | - Erin M Hanada
- The Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195-1700, United States
| | - Werner Kaminsky
- The Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195-1700, United States
| | - Julie A Kovacs
- The Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195-1700, United States
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9
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Reprint of: Nitrile functionalized organogermane chalcogenide clusters with hetero-(nor-)adamantane cores. J Organomet Chem 2016. [DOI: 10.1016/j.jorganchem.2016.09.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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10
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Heimann S, Thiele G, Dehnen S. Nitrile functionalized organogermane chalcogenide clusters with hetero-(nor-)adamantane cores. J Organomet Chem 2016. [DOI: 10.1016/j.jorganchem.2016.03.026] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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11
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Fang YX, Ao YF, Wang DX, Zhao L, Wang MX. Synthesis, structure and transition metal ion complexation property of lariat azacalix[4]pyridines. Tetrahedron 2015. [DOI: 10.1016/j.tet.2015.02.045] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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12
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Widger LR, Jiang Y, McQuilken AC, Yang T, Siegler MA, Matsumura H, Moënne-Loccoz P, Kumar D, de Visser SP, Goldberg DP. Thioether-ligated iron(II) and iron(III)-hydroperoxo/alkylperoxo complexes with an H-bond donor in the second coordination sphere. Dalton Trans 2014; 43:7522-32. [PMID: 24705907 PMCID: PMC4319814 DOI: 10.1039/c4dt00281d] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The non-heme iron complexes, [Fe(II)(N3PySR)(CH3CN)](BF4)2 () and [Fe(II)(N3Py(amide)SR)](BF4)2 (), afford rare examples of metastable Fe(iii)-OOH and Fe(iii)-OOtBu complexes containing equatorial thioether ligands and a single H-bond donor in the second coordination sphere. These peroxo complexes were characterized by a range of spectroscopic methods and density functional theory studies. The influence of a thioether ligand and of one H-bond donor on the stability and spectroscopic properties of these complexes was investigated.
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Affiliation(s)
- Leland R Widger
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA.
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13
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Widger LR, Davies CG, Yang T, Siegler MA, Troeppner O, Jameson GNL, Ivanović-Burmazović I, Goldberg DP. Dramatically accelerated selective oxygen-atom transfer by a nonheme iron(IV)-oxo complex: tuning of the first and second coordination spheres. J Am Chem Soc 2014; 136:2699-702. [PMID: 24471779 PMCID: PMC4004223 DOI: 10.1021/ja410240c] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
The
new ligand N3PyamideSR and its FeII complex
[FeII(N3PyamideSR)](BF4)2 (1) are described. Reaction of 1 with
PhIO at −40 °C gives metastable [FeIV(O)(N3PyamideSR)]2+ (2), containing a sulfide
ligand and a single amide H-bond donor in proximity to the terminal
oxo group. Direct evidence for H-bonding is seen in a structural analogue,
[FeII(Cl)(N3PyamideSR)](BF4)2 (3). Complex 2 exhibits rapid O-atom
transfer (OAT) toward external sulfide substrates, but no intramolecular
OAT. However, direct S-oxygenation does occur in
the reaction of 1 with mCPBA, yielding sulfoxide-ligated
[FeII(N3PyamideS(O)R)](BF4)2 (4). Catalytic OAT with 1 was also observed.
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Affiliation(s)
- Leland R Widger
- Department of Chemistry, The Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States
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14
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Lincoln KM, Offutt ME, Hayden TD, Saunders RE, Green KN. Structural, Spectral, and Electrochemical Properties of Nickel(II), Copper(II), and Zinc(II) Complexes Containing 12-Membered Pyridine- and Pyridol-Based Tetra-aza Macrocycles. Inorg Chem 2014; 53:1406-16. [DOI: 10.1021/ic402119s] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Kimberly M. Lincoln
- Department
of Chemistry, Texas Christian University, Fort Worth, Texas 76109, United States
| | - Michael E. Offutt
- Department
of Chemistry, Texas Christian University, Fort Worth, Texas 76109, United States
| | - Travis D. Hayden
- Department
of Chemistry, Texas Christian University, Fort Worth, Texas 76109, United States
| | - Ryker E. Saunders
- Department
of Chemistry, Texas Christian University, Fort Worth, Texas 76109, United States
| | - Kayla N. Green
- Department
of Chemistry, Texas Christian University, Fort Worth, Texas 76109, United States
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15
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Warner DS, Limberg C, Mebs S. Synthesis of a Chiral, Polydentate Ligand System Setting Out fromL-Cysteine and First Nickel Complexes Thereof. Z Anorg Allg Chem 2013. [DOI: 10.1002/zaac.201300071] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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16
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Abstract
The S-oxygenation of cysteine with dioxygen to give cysteine sulfinic acid occurs at the non-heme iron active site of cysteine dioxygenase. Similar S-oxygenation events occur in other non-heme iron enzymes, including nitrile hydratase and isopenicillin N synthase, and these enzymes have inspired the development of a class of [N(x)S(y)]-Fe model complexes. Certain members of this class have provided some intriguing examples of S-oxygenation, and this article summarizes these results, focusing on the non-heme iron(II/III)-thiolate model complexes that are known to react with O(2) or other O-atom transfer oxidants to yield sulfur oxygenates. Key aspects of the synthesis, structure, and reactivity of these systems are presented, along with any mechanistic information available on the oxygenation reactions. A number of iron(III)-thiolate complexes react with O(2) to give S-oxygenates, and the degree to which the thiolate sulfur donors are oxidized varies among the different complexes, depending upon the nature of the ligand, metal geometry, and spin state. The first examples of iron(II)-thiolate complexes that react with O(2) to give selective S-oxygenation are just emerging. Mechanistic information on these transformations is limited, with isotope labeling studies providing much of the current mechanistic data. The many questions that remain unanswered for both models and enzymes provide strong motivation for future work in this area.
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Affiliation(s)
- Alison C. McQuilken
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - David P. Goldberg
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
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17
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McQuilken AC, Jiang Y, Siegler MA, Goldberg DP. Addition of dioxygen to an N4S(thiolate) iron(II) cysteine dioxygenase model gives a structurally characterized sulfinato-iron(II) complex. J Am Chem Soc 2012; 134:8758-61. [PMID: 22578255 PMCID: PMC3403739 DOI: 10.1021/ja302112y] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The non-heme iron enzyme cysteine dioxygenase (CDO) catalyzes the S-oxygenation of cysteine by O(2) to give cysteine sulfinic acid. The synthesis of a new structural and functional model of the cysteine-bound CDO active site, [Fe(II)(N3PyS)(CH(3)CN)]BF(4) (1) is reported. This complex was prepared with a new facially chelating 4N/1S(thiolate) pentadentate ligand. The reaction of 1 with O(2) resulted in oxygenation of the thiolate donor to afford the doubly oxygenated sulfinate product [Fe(II)(N3PySO(2))(NCS)] (2), which was crystallographically characterized. The thiolate donor provided by the new N3PyS ligand has a dramatic influence on the redox potential and O(2) reactivity of this Fe(II) model complex.
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Affiliation(s)
- Alison C. McQuilken
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland, 21218, United States
| | - Yunbo Jiang
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland, 21218, United States
| | - Maxime A. Siegler
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland, 21218, United States
| | - David P. Goldberg
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland, 21218, United States
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Shearer J, Callan PE, Masitas CA, Grapperhaus CA. Influence of sequential thiolate oxidation on a nitrile hydratase mimic probed by multiedge X-ray absorption spectroscopy. Inorg Chem 2012; 51:6032-45. [PMID: 22591049 DOI: 10.1021/ic202453c] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Nitrile hydratases (NHases) are Fe(III)- and Co(III)-containing hydrolytic enzymes that convert nitriles into amides. The metal-center is contained within an N(2)S(3) coordination motif with two post-translationally modified cysteinates contained in a cis arrangement, which have been converted into a sulfinate (R-SO(2)(-)) and a sulfenate (R-SO(-)) group. Herein, we utilize Ru L-edge and ligand (N-, S-, and P-) K-edge X-ray absorption spectroscopies to probe the influence that these modifications have on the electronic structure of a series of sequentially oxidized thiolate-coordinated Ru(II) complexes ((bmmp-TASN)RuPPh(3), (bmmp-O(2)-TASN)RuPPh(3), and (bmmp-O(3)-TASN)RuPPh(3)). Included is the use of N K-edge spectroscopy, which was used for the first time to extract N-metal covalency parameters. We find that upon oxygenation of the bis-thiolate compound (bmmp-TASN)RuPPh(3) to the sulfenato species (bmmp-O(2)-TASN)RuPPh(3) and then to the mixed sulfenato/sulfinato speices (bmmp-O(3)-TASN)RuPPh(3) the complexes become progressively more ionic, and hence the Ru(II) center becomes a harder Lewis acid. These findings are reinforced by hybrid DFT calculations (B(38HF)P86) using a large quadruple-ζ basis set. The biological implications of these findings in relation to the NHase catalytic cycle are discussed in terms of the creation of a harder Lewis acid, which aids in nitrile hydrolysis.
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Affiliation(s)
- Jason Shearer
- Department of Chemistry, University of Nevada, Reno, Nevada 89557, USA.
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Naolou T, Busse K, Kressler J. Synthesis of Well-Defined Graft Copolymers by Combination of Enzymatic Polycondensation and “Click” Chemistry. Biomacromolecules 2010; 11:3660-7. [DOI: 10.1021/bm1011085] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Toufik Naolou
- Martin Luther University Halle-Wittenberg, Department of Chemistry, D-06099 Halle (Saale), Germany
| | - Karsten Busse
- Martin Luther University Halle-Wittenberg, Department of Chemistry, D-06099 Halle (Saale), Germany
| | - Jörg Kressler
- Martin Luther University Halle-Wittenberg, Department of Chemistry, D-06099 Halle (Saale), Germany
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McDonald AR, Bukowski MR, Farquhar ER, Jackson TA, Koehntop KD, Seo MS, De Hont RF, Stubna A, Halfen JA, Münck E, Nam W, Que L. Sulfur versus iron oxidation in an iron-thiolate model complex. J Am Chem Soc 2010; 132:17118-29. [PMID: 21070030 DOI: 10.1021/ja1045428] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In the absence of base, the reaction of [Fe(II)(TMCS)]PF6 (1, TMCS = 1-(2-mercaptoethyl)-4,8,11-trimethyl-1,4,8,11-tetraazacyclotetradecane) with peracid in methanol at -20 °C did not yield the oxoiron(IV) complex (2, [Fe(IV)(O)(TMCS)]PF6), as previously observed in the presence of strong base (KO(t)Bu). Instead, the addition of 1 equiv of peracid resulted in 50% consumption of 1. The addition of a second equivalent of peracid resulted in the complete consumption of 1 and the formation of a new species 3, as monitored by UV-vis, ESI-MS, and Mössbauer spectroscopies. ESI-MS showed 3 to be formulated as [Fe(II)(TMCS) + 2O](+), while EXAFS analysis suggested that 3 was an O-bound iron(II)-sulfinate complex (Fe-O = 1.95 Å, Fe-S = 3.26 Å). The addition of a third equivalent of peracid resulted in the formation of yet another compound, 4, which showed electronic absorption properties typical of an oxoiron(IV) species. Mössbauer spectroscopy confirmed 4 to be a novel iron(IV) compound, different from 2, and EXAFS (Fe═O = 1.64 Å) and resonance Raman (ν(Fe═O) = 831 cm(-1)) showed that indeed an oxoiron(IV) unit had been generated in 4. Furthermore, both infrared and Raman spectroscopy gave indications that 4 contains a metal-bound sulfinate moiety (ν(s)(SO2) ≈ 1000 cm (-1), ν(as)(SO2) ≈ 1150 cm (-1)). Investigations into the reactivity of 1 and 2 toward H(+) and oxygen atom transfer reagents have led to a mechanism for sulfur oxidation in which 2 could form even in the absence of base but is rapidly protonated to yield an oxoiron(IV) species with an uncoordinated thiol moiety that acts as both oxidant and substrate in the conversion of 2 to 3.
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Affiliation(s)
- Aidan R McDonald
- Department of Chemistry and Center for Metals in Biocatalysis, 207 Pleasant Street SE, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Masitas CA, Kumar M, Mashuta MS, Kozlowski PM, Grapperhaus CA. Controlled sulfur oxygenation of the ruthenium dithiolate (4,7-bis-(2'-methyl-2'-mercaptopropyl)-1-thia-4,7-diazacyclononane)RuPPh(3) under limiting O(2) conditions yields thiolato/sulfinato, sulfenato/sulfinato, and bis-sulfinato derivatives. Inorg Chem 2010; 49:10875-81. [PMID: 20973591 DOI: 10.1021/ic101221z] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The ruthenium(II) dithiolate complex (bmmp-TASN)RuPPh(3) (1) reacts with O(2) under limiting conditions to yield isolable sulfur oxygenated derivatives as a function of reaction time. With this approach, a family of sulfur-oxygenates has been prepared and isolated without the need for O-atom transfer agents or column chromatography. Addition of 5 equiv of O(2) to 1 yields the thiolato/sulfinato complex (bmmp-O(2)-TASN)RuPPh(3) (2) in 70% yield within 5 min. Increasing the reaction time to 12 h yields the sulfenato/sulfinato derivative (bmmp-O(3)-TASN)RuPPh(3) (3) in 82% yield. Longer reaction times and/or additional O(2) exposure yield the bis-sulfinato complex (bmmp-O(4)-TASN)RuPPh(3) (4). All products remain in the Ru(II) oxidation state under the conditions employed. Stoichiometric hydrolysis of acetonitrile to acetamide by 2 and 3 is observed in mixed acetonitrile, methanol, PIPES buffer (pH = 7.0) mixtures. The Ru(III)/(II) reduction potential of -0.85 V (versus ferrocenium/ferrocene) for 1 shifts to -0.39 and -0.26 V for 2 and 3, respectively, because of the decreased donor ability of sulfur upon oxygenation. X-ray diffraction studies reveal a decrease in Ru-S bond distances upon oxygenation by 0.045(1) and 0.158(1) Å for the sulfenato and sulfinato donors, respectively. Conversely, sulfur-oxygenation increases the Ru-P bond distance by 0.061(1) Å from 1 to 2 and an additional 0.027(1) Å from 2 to 3. Density functional theory investigations using the BP86 and B3LYP functionals with a LANL2DZ basis set for Ru and the 6-31G(d) basis set for all other atoms reveal a direct correlation between the oxygenation level and the Ru-P distance with an increase of 0.031 Å per O-atom.
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Affiliation(s)
- César A Masitas
- Department of Chemistry, University of Louisville, Louisville, Kentucky 40292, United States
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Shearer J, Callan PE, Amie J. Use of metallopeptide based mimics demonstrates that the metalloprotein nitrile hydratase requires two oxidized cysteinates for catalytic activity. Inorg Chem 2010; 49:9064-77. [PMID: 20831172 PMCID: PMC3570060 DOI: 10.1021/ic101765h] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nitrile hydratases (NHases) are non-heme Fe(III) or non-corrin Co(III) containing metalloenzymes that possess an N(2)S(3) ligand environment with nitrogen donors derived from amidates and sulfur donors derived from cysteinates. A closely related enzyme is thiocyanate hydrolase (SCNase), which possesses a nearly identical active-site coordination environment as CoNHase. These enzymes are redox inactive and perform hydrolytic reactions; SCNase hydrolyzes thiocyanate anions while NHase converts nitriles into amides. Herein an active CoNHase metallopeptide mimic, [Co(III)NHase-m1] (NHase-m1 = AcNH-CCDLP-CGVYD-PA-COOH), that contains Co(III) in a similar N(2)S(3) coordination environment as CoNHase is reported. [Co(III)NHase-m1] was characterized by electrospray ionization-mass spectrometry (ESI-MS), gel-permeation chromatography (GPC), Co K-edge X-ray absorption spectroscopy (Co-S: 2.21 Å; Co-N: 1.93 Å), vibrational, and optical spectroscopies. We find that [Co(III)NHase-m1] will perform the catalytic conversion of acrylonitrile into acrylamide with up to 58 turnovers observed after 18 h at 25 °C (pH 8.0). FTIR data used in concert with calculated vibrational data (mPWPW91/aug-cc-TZVPP) demonstrates that the active form of [Co(III)NHase-m1] has a ligated SO(2) (ν = 1091 cm(-1)) moiety and a ligated protonated SO(H) (ν = 928 cm(-1)) moiety; when only one oxygenated cysteinate ligand (i.e., a mono-SO(2) coordination motif) or the bis-SO(2) coordination motif are found within [Co(III)NHase-m1] no catalytic activity is observed. Calculations of the thermodynamics of ligand exchange (B3LYP/aug-cc-TZVPP) suggest that the reason for this is that the SO(2)/SO(H) equatorial ligand motif promotes both water dissociation from the Co(III)-center and nitrile coordination to the Co(III)-center. In contrast, the under- or overoxidized motifs will either strongly favor a five coordinate Co(III)-center or strongly favor water binding to the Co(III)-center over nitrile binding.
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Affiliation(s)
- Jason Shearer
- Department of Chemistry, University of Nevada, Reno, Nevada 89557, USA.
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Hsieh CC, Chao WJ, Horng YC. An unique stair-like infinite chain polymer containing dimeric N2S3 square-pyramidal iron(III) complex. INORG CHEM COMMUN 2009. [DOI: 10.1016/j.inoche.2009.06.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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