1
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Skeel BA, Suess DLM. Exploiting Molecular Symmetry to Quantitatively Map the Excited-State Landscape of Iron-Sulfur Clusters. J Am Chem Soc 2023; 145:10376-10395. [PMID: 37125463 DOI: 10.1021/jacs.3c02412] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Cuboidal [Fe4S4] clusters are ubiquitous cofactors in biological redox chemistry. In the [Fe4S4]1+ state, pairwise spin coupling gives rise to six arrangements of the Fe valences ("valence isomers") among the four Fe centers. Because of the magnetic complexity of these systems, it has been challenging to understand how a protein's active site dictates both the arrangement of the valences in the ground state as well as the population of excited-state valence isomers. Here, we show that the ground-state valence isomer landscape can be simplified from a six-level system in an asymmetric protein environment to a two-level system by studying the problem in synthetic [Fe4S4]1+ clusters with solution C3v symmetry. This simplification allows for the energy differences between valence isomers to be quantified (in some cases with a resolution of <0.1 kcal/mol) by simultaneously fitting the VT NMR and solution magnetic moment data. Using this fitting protocol, we map the excited-state landscape for a range of clusters of the form [(SIMes)3Fe4S4-X/L]n, (SIMes = 1,3-dimesityl-imidazol-4,5-dihydro-2-ylidene; n = 0 for anionic, X-type ligands and n = +1 for neutral, L-type ligands) and find that a single ligand substitution can alter the relative ground-state energies of valence isomers by at least 103 cm-1. On this basis, we suggest that one result of "non-canonical" amino acid ligation in Fe-S proteins is the redistribution of the valence electrons in the manifold of thermally populated excited states.
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Affiliation(s)
- Brighton A Skeel
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Daniel L M Suess
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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2
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Sato A, Hori Y, Shigeta Y. Characterization of the Geometrical and Electronic Structures of the Active Site and Its Effects on the Surrounding Environment in Reduced High-Potential Iron-Sulfur Proteins Investigated by the Density Functional Theory Approach. Inorg Chem 2023; 62:2040-2048. [PMID: 36695190 DOI: 10.1021/acs.inorgchem.2c03617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The high-potential iron-sulfur protein (HiPIP) is an electron-transporting protein that functions in the photosynthetic electron-transfer system and possesses a cubane-type [4Fe-4S] cluster in the active center. Characterization of the geometrical and electronic structures of the [4Fe-4S] cluster leads to an understanding of the functions in HiPIP, which are expected to be influenced by the environment surrounding the [4Fe-4S] cluster. This work characterized the geometrical and electronic structures of the [4Fe-4S] cluster in the reduced HiPIP and evaluated their effects on the protein environment using the density functional theory (DFT) approach. DFT calculations showed that the structural asymmetry and spin delocalization between iron atoms allowed for the acquisition of a unique stable geometrical and electronic structure in the open-shell singlet. In addition, the formation of an Fe-Fe bond accompanying the spin delocalization was found to depend on the interatomic distance. A comparison of the calculated stable structures with and without consideration of the amino acids around the [4Fe-4S] cluster demonstrated that the surrounding amino acids stabilized the unique geometrical and electronic structure of the [4Fe-4S] cluster in HiPIP.
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Affiliation(s)
- Ayaka Sato
- Center for Computational Sciences, University of Tsukuba, Ibaraki305-8577, Japan.,Master's Program in Physics, Degree Programs in Pure and Applied Sciences, Graduate School of Science and Technology, University of Tsukuba, Ibaraki305-8577, Japan
| | - Yuta Hori
- Center for Computational Sciences, University of Tsukuba, Ibaraki305-8577, Japan
| | - Yasuteru Shigeta
- Center for Computational Sciences, University of Tsukuba, Ibaraki305-8577, Japan
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3
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Schüren AO, Ridgway BM, Di Salvo F, Carella LM, Gramm VK, Metzger E, Doctorovich F, Rentschler E, Schünemann V, Ruschewitz U, Klein A. Structural insight into halide-coordinated [Fe 4S 4X nY 4-n] 2- clusters (X, Y = Cl, Br, I) by XRD and Mössbauer spectroscopy. Dalton Trans 2023; 52:1277-1290. [PMID: 36621931 DOI: 10.1039/d2dt03203a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Iron sulphur halide clusters [Fe4S4Br4]2- and [Fe4S4X2Y2]2- (X, Y = Cl, Br, I) were obtained in excellent yields (77 to 78%) and purity from [Fe(CO)5], elemental sulphur, I2 and benzyltrimethylammonium (BTMA+) iodide, bromide and chloride. Single crystals of (BTMA)2[Fe4S4Br4] (1), (BTMA)2[Fe4S4Br2Cl2] (2), (BTMA)2[Fe4S4Cl2I2] (3), and (BTMA)2[Fe4S4Br2I2] (4) were isostructural to the previously reported (BTMA)2[Fe4S4I4] (5) (monoclinic, Cc). Instead of the chloride cubane cluster [Fe4S4Cl4]2-, we found the prismane-shaped cluster (BTMA)3[Fe6S6Cl6] (6) (P1̄). 57Fe Mössbauer spectroscopy indicates complete delocalisation with Fe2.5+ oxidation states for all iron atoms. Magnetic measurements showed small χMT values at 298 K ranging from 1.12 to 1.54 cm3 K mol-1, indicating the dominant antiferromagnetic exchange interactions. With decreasing temperature, the χMT values decreased to reach a plateau at around 100 K. From about 20 K, the values drop significantly. Fitting the data in the Heisenberg-Dirac-van Vleck (HDvV) as well as the Heisenberg Double Exchange (HDE) formalism confirmed the delocalisation and antiferromagnetic coupling assumed from Mössbauer spectroscopy.
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Affiliation(s)
- Andreas O Schüren
- Universität zu Köln, Mathematisch-Naturwissenschaftliche Fakultät, Department für Chemie, Institut für Anorganische Chemie, Greinstraße 6, D-50939 Köln, Germany. .,INQUIMAE-CONICET-Universidad de Buenos Aires, Intendente Güiraldes 2160, Pabellón 2, Piso 3, C1428EGA, Buenos Aires, Argentina
| | - Benjamin M Ridgway
- INQUIMAE-CONICET-Universidad de Buenos Aires, Intendente Güiraldes 2160, Pabellón 2, Piso 3, C1428EGA, Buenos Aires, Argentina
| | - Florencia Di Salvo
- INQUIMAE-CONICET-Universidad de Buenos Aires, Intendente Güiraldes 2160, Pabellón 2, Piso 3, C1428EGA, Buenos Aires, Argentina.,Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Inorgánica, Analítica y Química Física, Intendente Güiraldes 2160, Pabellón 2, Piso 3, C1428EGA, Buenos Aires, Argentina
| | - Luca M Carella
- Johannes Gutenberg Universität Mainz, Department Chemie, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Verena K Gramm
- Universität zu Köln, Mathematisch-Naturwissenschaftliche Fakultät, Department für Chemie, Institut für Anorganische Chemie, Greinstraße 6, D-50939 Köln, Germany.
| | - Elisa Metzger
- TU Kaiserlautern Department of Physics, 67663 Kaiserlautern, Germany
| | - Fabio Doctorovich
- INQUIMAE-CONICET-Universidad de Buenos Aires, Intendente Güiraldes 2160, Pabellón 2, Piso 3, C1428EGA, Buenos Aires, Argentina.,Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Inorgánica, Analítica y Química Física, Intendente Güiraldes 2160, Pabellón 2, Piso 3, C1428EGA, Buenos Aires, Argentina
| | - Eva Rentschler
- Johannes Gutenberg Universität Mainz, Department Chemie, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Volker Schünemann
- TU Kaiserlautern Department of Physics, 67663 Kaiserlautern, Germany
| | - Uwe Ruschewitz
- Universität zu Köln, Mathematisch-Naturwissenschaftliche Fakultät, Department für Chemie, Institut für Anorganische Chemie, Greinstraße 6, D-50939 Köln, Germany.
| | - Axel Klein
- Universität zu Köln, Mathematisch-Naturwissenschaftliche Fakultät, Department für Chemie, Institut für Anorganische Chemie, Greinstraße 6, D-50939 Köln, Germany.
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4
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Moula G, Nagasaki A, Matsumoto T, Miehlich ME, Meyer K, Cramer RE, Tatsumi K. Synthesis of a Nitrogenase P
N
‐Cluster Model with [Fe
8
S
7
(μ‐S
thiolate
)
2
] Core from the All‐Ferric [Fe
4
S
4
(S
thiolate
)
4
] Cubane Synthon. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202102369] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Golam Moula
- Research Center for Materials Science Nagoya University Furo-cho, Chikusa-ku Nagoya 464-8602 Japan
| | - Ayaka Nagasaki
- Research Center for Materials Science Nagoya University Furo-cho, Chikusa-ku Nagoya 464-8602 Japan
| | - Tsuyoshi Matsumoto
- Institute of Transformative Bio-Molecules (WPI-ITbM) Nagoya University Furo-cho, Chikusa-ku Nagoya 464-8601 Japan
| | - Matthias E. Miehlich
- Department of Chemistry and Pharmacy Inorganic Chemistry Friedrich-Alexander-University Erlangen-Nürnberg (FAU) Egerlandstrasse 1 91058 Erlangen Germany
| | - Karsten Meyer
- Department of Chemistry and Pharmacy Inorganic Chemistry Friedrich-Alexander-University Erlangen-Nürnberg (FAU) Egerlandstrasse 1 91058 Erlangen Germany
| | - Roger E. Cramer
- Department of Chemistry University of Hawaii Honolulu HI 96822 USA
| | - Kazuyuki Tatsumi
- Research Center for Materials Science Nagoya University Furo-cho, Chikusa-ku Nagoya 464-8602 Japan
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5
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Moula G, Nagasaki A, Matsumoto T, Miehlich ME, Meyer K, Cramer RE, Tatsumi K. Synthesis of a Nitrogenase P N -Cluster Model with [Fe 8 S 7 (μ-S thiolate ) 2 ] Core from the All-Ferric [Fe 4 S 4 (S thiolate ) 4 ] Cubane Synthon. Angew Chem Int Ed Engl 2021; 60:15792-15797. [PMID: 33928749 DOI: 10.1002/anie.202102369] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 03/31/2021] [Indexed: 11/06/2022]
Abstract
Constructing synthetic models of the nitrogenase PN -cluster has been a long-standing synthetic challenge. Here, we report an optimal nitrogenase PN -cluster model [{(TbtS)(OEt2 )Fe4 S3 }2 (μ-STbt)2 (μ6 -S)] (2) [Tbt=2,4,6-tris{bis(trimethylsilyl)methyl}phenyl] that is the closest synthetic mimic constructed to date. Of note is that two thiolate ligands and one hexacoordinated sulfide are connecting the two Fe4 S3 incomplete cubanes similar to the native PN -cluster, which has never been achieved. Cluster 2 has been characterized by X-ray crystallography and relevant physico-chemical methods. The variable temperature magnetic moments of 2 indicate a singlet ground state (S=0). The Mössbauer spectrum of 2 exhibits two doublets with an intensity ratio of 3:1, which suggests the presence of two types of iron sites. The synthetic pathway of the cluster 2 could indicate the native PN -cluster maturation process as it has been achieved from the Fe4 S4 cubane Fe4 S4 (STbt)4 (1).
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Affiliation(s)
- Golam Moula
- Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Ayaka Nagasaki
- Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
| | - Tsuyoshi Matsumoto
- Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
| | - Matthias E Miehlich
- Department of Chemistry and Pharmacy, Inorganic Chemistry, Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Egerlandstrasse 1, 91058, Erlangen, Germany
| | - Karsten Meyer
- Department of Chemistry and Pharmacy, Inorganic Chemistry, Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Egerlandstrasse 1, 91058, Erlangen, Germany
| | - Roger E Cramer
- Department of Chemistry, University of Hawaii, Honolulu, HI, 96822, USA
| | - Kazuyuki Tatsumi
- Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
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6
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Zanello P. The competition between chemistry and biology in assembling iron–sulfur derivatives. Molecular structures and electrochemistry. Part V. {[Fe4S4](SCysγ)4} proteins. Coord Chem Rev 2017. [DOI: 10.1016/j.ccr.2016.10.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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7
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Schüren AO, Gramm VK, Dürr M, Foi A, Ivanović-Burmazović I, Doctorovich F, Ruschewitz U, Klein A. Halide coordinated homoleptic [Fe4S4X4](2-) and heteroleptic [Fe4S4X2Y2](2-) clusters (X, Y = Cl, Br, I)--alternative preparations, structural analogies and spectroscopic properties in solution and solid state. Dalton Trans 2016; 45:361-75. [PMID: 26618565 DOI: 10.1039/c5dt02769a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
New facile methods to prepare iron sulphur halide clusters [Fe4S4X4](2-) from [Fe(CO)5] and elemental sulphur were elaborated. Reactions of ferrous precursors like tetrahalidoferrates(ii) or simple ferrous halides with [Fe(CO)5] and sulphur turned out to be efficient methods to prepare homoleptic [Fe4S4X4](2-) (X = Cl, Br) and heteroleptic clusters [Fe4S4X4-nYn](2-) (X = Cl, Br; Y = Br, I). Solid materials were obtained as salts of BTMA(+) (= benzyltrimethylammonium); the new compounds containing [Fe4S4Br4](2-) and [Fe4S4X2Y2](2-) (X, Y = Cl, Br, I) were all isostructural to (BTMA)2[Fe4S4I4] (monoclinic, Cc) as inferred from synchrotron X-ray powder diffraction. While the solid materials contain defined heteroleptic clusters with a halide X : Y ratio of 2 : 2, dissolving these compounds leads to rapid scrambling of the halide ligands forming mixtures of all five possible [Fe4S4X4-nYn](2-) clusters as could be shown by UHR-ESI MS. The variation of X and Y allowed assignment of the absorption bands in the visible and NIR; the long-wavelength bands around 1100 nm were tentatively assigned to intervalence charge transfer (IVCT) transitions.
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Affiliation(s)
- Andreas O Schüren
- Department für Chemie, Institut für Anorganische Chemie, Universität zu Köln, Greinstraße 6, 50939 Köln, Germany. and Departamento de Química Inorgánica, Analítica, y Química Física, Facultad de Ciencias Exactas y Naturales, INQUIMAE-CONICET, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón 2, Piso 3, C1428EHA Buenos Aires, Argentina
| | - Verena K Gramm
- Department für Chemie, Institut für Anorganische Chemie, Universität zu Köln, Greinstraße 6, 50939 Köln, Germany.
| | - Maximilian Dürr
- Department Chemie und Pharmazie, Lehrstuhl für Bioanorgansiche Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany
| | - Ana Foi
- Departamento de Química Inorgánica, Analítica, y Química Física, Facultad de Ciencias Exactas y Naturales, INQUIMAE-CONICET, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón 2, Piso 3, C1428EHA Buenos Aires, Argentina
| | - Ivana Ivanović-Burmazović
- Department Chemie und Pharmazie, Lehrstuhl für Bioanorgansiche Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany
| | - Fabio Doctorovich
- Departamento de Química Inorgánica, Analítica, y Química Física, Facultad de Ciencias Exactas y Naturales, INQUIMAE-CONICET, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón 2, Piso 3, C1428EHA Buenos Aires, Argentina
| | - Uwe Ruschewitz
- Department für Chemie, Institut für Anorganische Chemie, Universität zu Köln, Greinstraße 6, 50939 Köln, Germany.
| | - Axel Klein
- Department für Chemie, Institut für Anorganische Chemie, Universität zu Köln, Greinstraße 6, 50939 Köln, Germany.
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8
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Tanifuji K, Yamada N, Tajima T, Sasamori T, Tokitoh N, Matsuo T, Tamao K, Ohki Y, Tatsumi K. A convenient route to synthetic analogues of the oxidized form of high-potential iron-sulfur proteins. Inorg Chem 2014; 53:4000-9. [PMID: 24694068 DOI: 10.1021/ic402890k] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
An amide-bound [Fe4S4](3+) cluster, [Fe4S4{N(SiMe3)2}4](-) (1), was found to serve as a convenient precursor for synthetic analogues of the oxidized form of high-potential iron-sulfur proteins. Treatment of 1 with 4 equiv of bulky thiols led to replacement of the amide ligands with thiolates, giving rise to a series of [Fe4S4(SR)4](-) clusters (R = Dmp (2a), Tbt (2b), Eind (2c), Dxp (2d), Dpp (2e); Dmp = 2,6-di(mesityl)phenyl, Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl, Eind = 1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl, Dxp = 2,6-di(m-xylyl)phenyl, Dpp = 2,6-diphenylphenyl). These clusters were characterized by the mass spectrum, the EPR spectrum, and X-ray crystallography. The redox potentials of the [Fe4S4](3+/2+) couple, -0.82 V (2a), -0.86 V (2b), -0.84 V (2c), -0.74 V (2d), and -0.63 V (2e) vs Ag/Ag(+) in THF, are significantly more negative than that of [Fe4S4(SPh)4](-/2-) (-0.21 V).
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Affiliation(s)
- Kazuki Tanifuji
- Department of Chemistry, Graduate School of Science, and Research Center for Materials Science, Nagoya University , Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
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9
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Terada T, Wakimoto T, Nakamura T, Hirabayashi K, Tanaka K, Li J, Matsumoto T, Tatsumi K. Tridentate thiolate ligands: application to the synthesis of the site-differentiated [4Fe-4S] cluster having a hydrosulfide ligand at the unique iron center. Chem Asian J 2012; 7:920-9. [PMID: 22488788 DOI: 10.1002/asia.201200039] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Indexed: 11/08/2022]
Abstract
We have designed new trithiols Temp(SH)(3) and Tefp(SH)(3) that can be synthesized conveniently in short steps and are useful for preparation of crystalline [3:1] site-differentiated [4Fe-4S] clusters suitable for X-ray structural analysis. The ethanethiolate clusters (PPh(4))(2)[Fe(4)S(4)(SEt)(TempS(3))] (4a) and (PPh(4))(2)[Fe(4)S(4)(SEt)(TefpS(3))] (4b) were prepared as precursors, and the unique iron sites were then selectively substituted. Upon reaction with H(2)S, (PPh(4))(2)[Fe(4)S(4)(SH)(TempS(3))] (6a) and (PPh(4))(2)[Fe(4)S(4)(SH)(TefpS(3))] (6b), which model the [4Fe-4S] cluster in the β subunit of (R)-2-hydroxyisocaproyl-CoA dehydratase, were synthesized. Clusters 6a and 6b were further converted to the sulfido-bridged double cubanes (PPh(4))(4)[{Fe(4)S(4)(TempS(3))}(2)(μ(2)-S)] (7a) and (PPh(4))(4)[{Fe(4)S(4)(TefpS(3))}(2)(μ(2)-S)] (7b), respectively, via intermolecular condensation with the release of H(2)S. Conversely, addition of H(2)S to 7a,b afforded the hydrosulfide clusters 6a,b. The molecular structures of the clusters reported herein were elucidated by X-ray crystallographic analysis. Their redox properties were investigated by cyclic voltammetry.
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Affiliation(s)
- Tamaki Terada
- Research Center for Materials Science and Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
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10
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Stabilities of cubane type [Fe₄S₄(SR)₄](2-) clusters in partially aqueous media. J Inorg Biochem 2010; 105:497-508. [PMID: 21329647 DOI: 10.1016/j.jinorgbio.2010.12.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Revised: 12/20/2010] [Accepted: 12/22/2010] [Indexed: 11/23/2022]
Abstract
The stability of cubane-type [Fe₄S₄(SR)₄](2-) clusters in mixed organic/aqueous solvents was examined as an initial step in the development of stable water-soluble cluster compounds possibly suitable for reconstitution of scaffold proteins in protein biosynthesis. The research involves primarily spectrophotometric assessment of stability in 20-80% Me₂SO/aqueous media (v/v), from which it was found that conventional clusters tend to be stable for up to 12h in 60% Me₂SO but are much less stable at higher aqueous content. α-Cyclodextrin mono- and dithioesters and thiols were prepared as ligand precursors for cluster binding, which was demonstrated by spectroscopic methods. A potentially bidentate cyclodextrin dithiolate was found to be relatively effective for cluster stabilization in 40% Me₂SO, suggesting (together with earlier results) that other exceptionally large thiolate ligands may promote cluster stability in aqueous media.
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11
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Abstract
Although DFT calculations have provided a first-order electronic-structural description for Roussin's red and black salts, a detailed study of spin coupling in these species has yet to be reported. Such an analysis is presented here for the first time, based on broken-symmetry density functional theory (DFT, chiefly OLYP/STO-TZP) calculations. Both the Noodleman and Yamaguchi formulas were used to evaluate the Heisenberg coupling constants (J). Three nitrosylated binuclear clusters were studied: [Fe(2)(NO)(2)(Et-HPTB)(O(2)CPh)](2+) (1; Et-HPTB=N,N,N',N'-tetrakis-(N-ethyl-2-benzimidazolylmethyl)-2-hydroxy-1,3-diaminopropane), [Fe(NO)(2){Fe(NO)(NS(3))}-S,S'] (2), and Roussin's red salt anion [Fe(2)(NO)(4)(μ-S)(2)](2-) (3). Although the Heisenberg J for 1 is small (≈10(2) cm(-1)), 2 and 3 exhibit J values that are at least an order of magnitude higher (≈10(3) cm(-1)), where the J values refer to the following Heisenberg spin Hamiltonian: ℋ=JS(A)⋅S(B). For Roussin's black salt anion, [Fe(4)(NO)(7)(μ(3)-S)(3)](-) (4), the Heisenberg spin Hamiltonian describing spin coupling between the {FeNO}(7) unit (S(A)=3/2) and the three {Fe(NO)(2)}(9) units (S(B)=S(C)=S(D)=1/2) in [Fe(4)(NO)(7)(μ(3)-S)(3)](-) was assumed to have the form: ℋ=J(12)(S(A)⋅S(B)+S(A)⋅S(C)+S(A)⋅S(D))+J(22)(S(B)⋅S(C)+S(B)⋅S(D)+S(C)⋅S(D)), in which J(12) corresponds to the interaction between the apical iron and a basal iron, and J(22) refers to that between any two basal iron centers. Although the basal-basal coupling constant J(22) was found to be small (≈10(2) cm(-1)), the apical-basal coupling constant J(12) is some forty times higher (≈4000 cm(-1)). Thus, the nitrosylated iron-sulfur clusters feature some exceptionally high J values relative to the non-nitrosylated {2Fe2S} and {4Fe4S} clusters. An analysis of spin-dependent bonding energies shed light on this curious feature. In essence, the energy difference between the high-spin (i.e., ferromagnetically coupled iron sites) and low-spin (i.e., maximum spin coupling) states of Roussin's salts are indeed rather similar to those of analogous non-nitrosylated iron-sulfur clusters. However, the individual Fe(NO)(x) (x=1, 2) site spins are lower in the nitrosylated systems, resulting in a smaller denominator in both the Noodleman and Yamaguchi formulas for J, which in turn translates into the very high J values.
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Affiliation(s)
- Kathrin H Hopmann
- Center for Theoretical and Computational Chemistry and Department of Chemistry, University of Tromsø, 9037 Tromsø, Norway
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12
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Zakai UI, Błoch-Mechkour A, Jacobsen NE, Abrell L, Lin G, Nichol GS, Bally T, Glass RS. Synthesis and Structure of m-Terphenyl Thio-, Seleno-, and Telluroethers. J Org Chem 2010; 75:8363-71. [DOI: 10.1021/jo101299x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Uzma I. Zakai
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States
| | - Anna Błoch-Mechkour
- Department of Chemistry, University of Fribourg, CH-1700 Fribourg, Switzerland
| | - Neil E. Jacobsen
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States
| | - Leif Abrell
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States
| | - Guangxin Lin
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States
| | - Gary S. Nichol
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States
| | - Thomas Bally
- Department of Chemistry, University of Fribourg, CH-1700 Fribourg, Switzerland
| | - Richard S. Glass
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States
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Wang R, Xu W, Zhang J, Li L. A new hexanuclear iron-selenium nitrosyl cluster: primary exploration of the preparation methods, structure, and spectroscopic and electrochemical properties. Inorg Chem 2010; 49:4814-9. [PMID: 20459063 DOI: 10.1021/ic9014509] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A new hexanuclear iron-selenium nitrosyl cluster, [(n-Bu)(4)N](2)[Fe(6)Se(6)(NO)(6)] (1), and a hexanuclear iron-sulfur nitrosyl cluster, [(n-Bu)(4)N](2)[Fe(6)S(6)(NO)(6)] (2), were synthesized by the solvent-thermal reactions of [(n-Bu)(4)N][Fe(CO)(3)NO] with selenium or sulfur in methanol, while a tetranuclear iron-sulfur nitrosyl cluster, (Me(4)N)[Fe(4)S(3)(NO)(7)] (3), was also prepared by the solvent-thermal reaction of FeCl(2).4H(2)O with thiourea in the presence of (CH(3))(4)NCl, NaNO(2), and methanol. Complexes 1-3 were characterized by IR, UV-vis, (1)H NMR, electrochemistry, and single-crystal X-ray diffraction analysis. IR spectra of complexes 1 and 2 show the characteristic NO stretching frequencies at 1694 and 1698 cm(-1), respectively, while the absorptions of complex 3 appear at 1799, 1744, and 1710 cm(-1). The UV-vis spectra of complexes 1-3 show different bands in the range of 259-562 nm, which are assigned to the transitions between orbitals delocalized over the Fe-S cluster, the ligand-to-metal charge transfer, pi*(NO)-d(Fe), and the metal-to-ligand charge transfer, d(Fe)-pi*(NO). Single-crystal X-ray structural analysis reveals that complex 1 crystallizes in the monoclinic P2(1)/n space group with two molecules per unit cell. Two parallel "chair-shaped" structures, consisting of three iron and three selenium atoms, are connected by Fe-Se bonds with an average distance of 2.341 A; each iron center is bonded to three selenium atoms and a nitrogen atom from the nitrosyl ligand with a pseudotetrahedral center geometry. Cyclic voltammograms of complexes 1 and 2 display two cathodic and three anodic current peaks with an unusually strong cathodic peak. Further electrochemical investigations demonstrated that the intensity of the unusually strong peak is a result of at least three processes. One is the quasi-reversible reduction, and the other two are from an irreversible electrochemical process, in which the compound goes through a typical electron transfer and chemical reaction mechanism. Compound 3 shows three quasi-reversible reductions.
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Affiliation(s)
- Rongming Wang
- Department of Chemistry and Biochemistry, California State University, Long Beach, 1250 Bellflower Boulevard, Long Beach, California 90840, USA.
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