151
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Goto A, Endo K, Saito S. RhI-Catalyzed Hydration of Organonitriles under Ambient Conditions. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200800366] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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152
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Song Y, Xu Z, Sun Q, Su B, Gao Q, Liu H, Zhao J. Synthesis, structures, and characterization of copper(II), nickel(II), and cobalt(III) metal complexes derived from an asymmetric bidentate Schiff-base ligand. J COORD CHEM 2008. [DOI: 10.1080/00958970701509768] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Yanhong Song
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an, Shaanxi 710069, China
| | - Zhanwei Xu
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an, Shaanxi 710069, China
| | - Qingjin Sun
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an, Shaanxi 710069, China
| | - Biyun Su
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an, Shaanxi 710069, China
| | - Quanchang Gao
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an, Shaanxi 710069, China
| | - Huaqiang Liu
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an, Shaanxi 710069, China
| | - Jianshe Zhao
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an, Shaanxi 710069, China
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153
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Ray A, Banerjee S, Rosair GM, Gramlich V, Mitra S. Variation in coordinative property of two different N2O2 donor Schiff base ligands with nickel(II) and cobalt(III) ions: characterisation and single crystal structure elucidation. Struct Chem 2008. [DOI: 10.1007/s11224-008-9304-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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154
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Hopmann KH, Himo F. Theoretical Investigation of the Second-Shell Mechanism of Nitrile Hydratase. Eur J Inorg Chem 2008. [DOI: 10.1002/ejic.200701137] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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155
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Alonso FOM, Oestreicher EG, Antunes OAC. Production of enantiomerically pure D-Phenylglycine using Pseudomonas aeruginosa 10145 as biocatalyst. BRAZILIAN JOURNAL OF CHEMICAL ENGINEERING 2008. [DOI: 10.1590/s0104-66322008000100002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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156
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Thallaj NK, Przybilla J, Welter R, Mandon D. A Ferrous Center as Reaction Site for Hydration of a Nitrile Group into a Carboxamide in Mild Conditions. J Am Chem Soc 2008; 130:2414-5. [DOI: 10.1021/ja710560g] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Nasser K. Thallaj
- Laboratoire de Chimie Biomimétique des Métaux de Transition and Laboratoire DECOMET, Institut de Chimie, UMR CNRS nο. 7177-LC 3, Université Louis Pasteur, 4 rue Blaise Pascal, B.P. 1032, F-67070 Strasbourg cedex, France
| | - Juliette Przybilla
- Laboratoire de Chimie Biomimétique des Métaux de Transition and Laboratoire DECOMET, Institut de Chimie, UMR CNRS nο. 7177-LC 3, Université Louis Pasteur, 4 rue Blaise Pascal, B.P. 1032, F-67070 Strasbourg cedex, France
| | - Richard Welter
- Laboratoire de Chimie Biomimétique des Métaux de Transition and Laboratoire DECOMET, Institut de Chimie, UMR CNRS nο. 7177-LC 3, Université Louis Pasteur, 4 rue Blaise Pascal, B.P. 1032, F-67070 Strasbourg cedex, France
| | - Dominique Mandon
- Laboratoire de Chimie Biomimétique des Métaux de Transition and Laboratoire DECOMET, Institut de Chimie, UMR CNRS nο. 7177-LC 3, Université Louis Pasteur, 4 rue Blaise Pascal, B.P. 1032, F-67070 Strasbourg cedex, France
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157
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Rabie U, Assran A, Abou-El-Wafa M. Unsymmetrical Schiff bases functionalize as bibasic tetradentate (ONNO) and monobasic tridentate (NNO) ligands on complexation with some transition metal ions. J Mol Struct 2008. [DOI: 10.1016/j.molstruc.2007.02.023] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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158
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Singh AK, Mukherjee R. Cobalt(ii) and cobalt(iii) complexes of thioether-containing hexadentate pyrazine amide ligands: C–S bond cleavage and cyclometallation reaction. Dalton Trans 2008:260-70. [DOI: 10.1039/b709901k] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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159
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Nayak S, Dash AC, Lahiri GK. A new octahedral cobalt(III) complex of (1,8)-bis(2-hydroxybenzamido)-3,6-diazaoctane incorporating phenolate-amide-amine coordination: synthesis, X-ray crystal structure, ligand substitution and redox activity with sulfur(IV) and l-ascorbic acid. TRANSIT METAL CHEM 2007. [DOI: 10.1007/s11243-007-9012-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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160
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Song Y, Xu Z, Sun Q, Su B, Gao Q, Liu H, Zhao J. Chloro-bridged complexes of copper(II) and manganese(II) derived from unsymmetric bidentate ligands: synthesis, crystal structure and characterization. J COORD CHEM 2007. [DOI: 10.1080/00958970701266484] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Yanhong Song
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an, Shaanxi 710069, China
| | - Zhanwei Xu
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an, Shaanxi 710069, China
| | - Qingjin Sun
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an, Shaanxi 710069, China
| | - Biyun Su
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an, Shaanxi 710069, China
| | - Quanchang Gao
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an, Shaanxi 710069, China
| | - Huaqiang Liu
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an, Shaanxi 710069, China
| | - Jianshe Zhao
- a Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry , Northwest University , Xi’an, Shaanxi 710069, China
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161
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John A, Katiyar V, Pang K, Shaikh MM, Nanavati H, Ghosh P. Ni(II) and Cu(II) complexes of phenoxy-ketimine ligands: Synthesis, structures and their utility in bulk ring-opening polymerization (ROP) of l-lactide. Polyhedron 2007. [DOI: 10.1016/j.poly.2007.04.039] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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162
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Sharma SK, Upreti S, Gupta R. Effect of Ligand Architecture on the Structure and Properties of Square-Planar Nickel(II) Complexes of Amide-Based Macrocycles. Eur J Inorg Chem 2007. [DOI: 10.1002/ejic.200700122] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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163
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Khandar AA, Shaabani B, Belaj F, Bakhtiari A. Synthesis, characterization, electrochemical and spectroscopic investigation of cobalt(III) Schiff base complexes with axial amine ligands: The layered crystal structure of [CoIII(salophen)(4-picoline)2]ClO4·CH2Cl2. Inorganica Chim Acta 2007. [DOI: 10.1016/j.ica.2007.03.036] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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164
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Dey A, Jeffrey SP, Darensbourg M, Hodgson KO, Hedman B, Solomon EI. Sulfur K-edge XAS and DFT studies on NiII complexes with oxidized thiolate ligands: implications for the roles of oxidized thiolates in the active sites of Fe and Co nitrile hydratase. Inorg Chem 2007; 46:4989-96. [PMID: 17500514 PMCID: PMC2565589 DOI: 10.1021/ic070244l] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
S K-edge X-ray absorption spectroscopy data on a series of NiII complexes with thiolate (RS-) and oxidized thiolate (RSO2-) ligands are used to quantify Ni-S bond covalency and its change upon ligand oxidation. Analyses of these results using geometry-optimized density functional theory (DFT) calculations suggest that the Ni-S sigma bonds do not weaken on ligand oxidation. Molecular orbital analysis indicates that these oxidized thiolate ligands use filled high-lying S-O pi* orbitals for strong sigma donation. However, the RSO2- ligands are poor pi donors, as the orbital required for pi interaction is used in the S-O sigma-bond formation. The oxidation of the thiolate reduces the repulsion between electrons in the filled Ni t2 orbital and the thiolate out-of-plane pi-donor orbital leading to shorter Ni-S bond length relative to that of the thiolate donor. The insights obtained from these results are relevant to the active sites of Fe- and Co-type nitrile hydratases (Nhase) that also have oxidized thiolate ligands. DFT calculations on models of the active site indicate that whereas the oxidation of these thiolates has a major effect in the axial ligand-binding affinity of the Fe-type Nhase (where there is both sigma and pi donation from the S ligands), it has only a limited effect on the sixth-ligand-binding affinity of the Co-type Nhases (where there is only sigma donation). These oxidized residues may also play a role in substrate binding and proton shuttling at the active site.
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Affiliation(s)
- Abhishek Dey
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | - Stephen P. Jeffrey
- Department of Chemistry, Texas A&M University, College Station, TX, 77843
| | | | - Keith O. Hodgson
- Department of Chemistry, Stanford University, Stanford, CA, 94305
- Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Menlo Park, California 94025
| | - Britt Hedman
- Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Menlo Park, California 94025
| | - Edward I. Solomon
- Department of Chemistry, Stanford University, Stanford, CA, 94305
- Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Menlo Park, California 94025
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165
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Howell SJ, Day CS, Noftle RE. Metal Complexes of 3-Thiophene Carboxamides Containing a Pyridine Ring. Inorganica Chim Acta 2007; 360:2669-2680. [PMID: 18516222 PMCID: PMC2245882 DOI: 10.1016/j.ica.2007.01.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Complexes of Zn(II), Cu(II) and Co(II) with either N-(2-methylpyridyl)-3-thienyl-alkyl-carboxamide or N-(2-pyridyl)-3-thienylalkyl-carboxamide groups have been prepared and characterized. Crystal structures of ten new complexes are reported and discussed. N-(2-Methylpyridyl)-3-thienyl-alkyl-carboxamide exhibits both uni- and bidentate behavior. With all ligands, bidentate complexation is through the carbonyl oxygen and pyridine nitrogen atoms (O, N) and the amide nitrogen atom remains protonated. The electrochemical behavior and the infrared spectra of selected complexes are discussed.
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Affiliation(s)
- S Jarrett Howell
- Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109, USA
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166
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Hopmann KH, Guo JD, Himo F. Theoretical Investigation of the First-Shell Mechanism of Nitrile Hydratase. Inorg Chem 2007; 46:4850-6. [PMID: 17497847 DOI: 10.1021/ic061894c] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The first-shell mechanism of nitrile hydratase (NHase) is investigated theoretically using density functional theory. NHases catalyze the conversion of nitriles to amides and are classified into two groups, the non-heme Fe(III) NHases and the non-corrinoid Co(III) NHases. The active site of the non-heme iron NHase comprises a low-spin iron (S=1/2) with a remarkable set of ligands, including two deprotonated backbone nitrogens and both cysteine-sulfenic and cysteine-sulfinic acids. A widely proposed reaction mechanism of NHase is the first-shell mechanism in which the nitrile substrate binds directly to the low-spin iron in the sixth coordination site. We have used quantum chemical models of the NHase active site to investigate this mechanism. We present potential energy profiles for the reaction and provide characterization of the intermediates and transition-state structures for the NHase-mediated conversion of acetonitrile. The results indicate that the first-shell ligand Cys114-SO- could be a possible base in the nitrile hydration mechanism, abstracting a proton from the nucleophilic water molecule. The generally suggested role of the Fe(III) center as a Lewis acid, activating the substrate toward nucleophilic attack, is shown to be unlikely. Instead, the metal is suggested to provide electrostatic stabilization to the anionic imidate intermediate, thereby lowering the reaction barrier.
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Affiliation(s)
- Kathrin H Hopmann
- Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, AlbaNova University Center, SE-106 91 Stockholm, Sweden
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167
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Harrop TC, Olmstead MM, Mascharak PK. Synthetic analogues of the active site of the A-cluster of acetyl coenzyme A synthase/CO dehydrogenase: syntheses, structures, and reactions with CO. Inorg Chem 2007; 45:3424-36. [PMID: 16602803 PMCID: PMC4826277 DOI: 10.1021/ic0520465] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Two metallosynthons, namely (Et4N)2[Ni(NpPepS)] (1) and (Et4N)2[Ni(PhPepS)] (2) containing carboxamido-N and thiolato-S as donors have been used to model the bimetallic M(p)-Ni(d) subsite of the A-cluster of the enzyme acetyl coenzyme A synthase/CO dehydrogenase. A series of sulfur-bridged Ni/Cu dinuclear and trinuclear complexes (3-10) have been synthesized to explore their redox properties and affinity of the metal centers toward CO. The structures of (Et4N)2[Ni(PhPepS)] (2), (Et4N)[Cu(neo)Ni(NpPepS)] x 0.5 Et2O x 0.5 H2O (3 x 0.5 Et2O x 0.5 H2O), (Et4N)[Cu(neo)Ni(PhPepS)] x H2O (4 x H2O), (Et4N)2[Ni{Ni(NpPepS)}2] x DMF (5 x DMF), (Et4N)2[Ni(DMF)2{Ni(NpPepS)}2] x 3 DMF (6 x 3 DMF), (Et4N)2[Ni(DMF)2{Ni(PhPepS)}2] (8), and [Ni(dppe)Ni(PhPepS)] x CH2Cl2 (10 x CH2Cl2) have been determined by crystallography. The Ni(d) mimics 1 and 2 resist reduction and exhibit no affinity toward CO. In contrast, the sulfur-bridged Ni center (designated Ni(C)) in the trinuclear models 5-8 are amenable to reduction and binds CO in the Ni(I) state. Also, the sulfur-bridged Ni(C) center can be removed from the trimers (5-8) by treatment with 1,10-phenanthroline much like the "labile Ni" from the enzyme. The dinuclear Ni-Ni models 9 and 10 resemble the Ni(p)-Ni(d) subsite of the A-cluster more closely, and only the modeled Ni(p) site of the dimers can be reduced. The Ni(I)-Ni(II) species display EPR spectra typical of a Ni(I) center in distorted trigonal bipyramidal and distorted tetrahedral geometries for 9(red) and 10(red), respectively. Both species bind CO, and the CO-adducts 9(red)-CO and 10(red)-CO display strong nu(co) at 2044 and 1997 cm(-1), respectively. The reduction of 10 is reversible. The CO-affinity of 10 in the reduced state and the nu(co) value of 10(red)-CO closely resemble the CO-bound reduced A-cluster (nu(co) = 1996 cm(-1)).
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Affiliation(s)
- Todd C. Harrop
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064
| | | | - Pradip K. Mascharak
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064
- (P. K. Mascharak), Fax: + 1-831-459-2935 Tel: + 1-831-459-4251
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168
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Arakawa T, Kawano Y, Kataoka S, Katayama Y, Kamiya N, Yohda M, Odaka M. Structure of Thiocyanate Hydrolase: A New Nitrile Hydratase Family Protein with a Novel Five-coordinate Cobalt(III) Center. J Mol Biol 2007; 366:1497-509. [PMID: 17222425 DOI: 10.1016/j.jmb.2006.12.011] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2006] [Revised: 12/01/2006] [Accepted: 12/05/2006] [Indexed: 10/23/2022]
Abstract
Thiocyanate hydrolase (SCNase) of Thiobacillus thioparus THI115 is a cobalt(III)-containing enzyme catalyzing the degradation of thiocyanate to carbonyl sulfide and ammonia. We determined the crystal structures of the apo- and native SCNases at a resolution of 2.0 A. SCNases in both forms had a conserved hetero-dodecameric structure, (alphabetagamma)(4). Four alphabetagamma hetero-trimers were structurally equivalent. One alphabetagamma hetero-trimer was composed of the core domain and the betaN domain, which was located at the center of the molecule and linked the hetero-trimers with novel quaternary interfaces. In both the apo- and native SCNases, the core domain was structurally conserved between those of iron and cobalt-types of nitrile hydratase (NHase). Native SCNase possessed the post-translationally modified cysteine ligands, gammaCys131-SO(2)H and gammaCys133-SOH like NHases. However, the low-spin cobalt(III) was found to be in the distorted square-pyramidal geometry, which had not been reported before in any protein. The size as well as the electrostatic properties of the substrate-binding pocket was totally different from NHases with respect to the charge distribution and the substrate accessibility, which rationally explains the differences in the substrate preference between SCNase and NHase.
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Affiliation(s)
- Takatoshi Arakawa
- Department of Biotechnology and Life Science, Graduate School of Technology, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan
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169
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Joseph J, Mehta BH. Synthesis, characterization, and thermal analysis of transition metal complexes of polydentate ONO donor Schiff base ligand. RUSS J COORD CHEM+ 2007. [DOI: 10.1134/s1070328407020091] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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170
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Kilinçarslan R, Karabiyik H, Ulusoy M, Aygün M, Çetinkaya B, Büyükgüngör O. The synthesis, electrochemical properties and structural characterization of bis ( N -(4-dimethylaminophenyl)-3,5-di- tert -butylsalicylaldiminato)copper(II). J COORD CHEM 2007. [DOI: 10.1080/00958970500537952] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Rafet Kilinçarslan
- a Department of Chemistry , Ege University , 35100-Bornova, İzmir, Turkey
| | - Hasan Karabiyik
- b Department of Physics , Dokuz Eylül University , 35160-Buca, İzmir, Turkey
| | - Mahmut Ulusoy
- a Department of Chemistry , Ege University , 35100-Bornova, İzmir, Turkey
| | - Muhittin Aygün
- b Department of Physics , Dokuz Eylül University , 35160-Buca, İzmir, Turkey
| | - Bekir Çetinkaya
- a Department of Chemistry , Ege University , 35100-Bornova, İzmir, Turkey
| | - Orhan Büyükgüngör
- c Department of Physics , Ondokuz Mayis University , 55139-Samsun, Turkey
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171
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Jacob W, Mukherjee R. Synthesis, structure, and properties of monomeric Fe(II), Co(II), and Ni(II) complexes of neutral N-(aryl)-2-pyridinecarboxamides. Inorganica Chim Acta 2006. [DOI: 10.1016/j.ica.2006.07.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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172
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Syntheses, structures, and properties of Co(III) complexes derived from polypyridine ligands containing one carboxamido nitrogen donor. Inorganica Chim Acta 2006. [DOI: 10.1016/j.ica.2006.04.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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173
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Lugo-Mas P, Dey A, Xu L, Davin SD, Benedict J, Kaminsky W, Hodgson KO, Hedman B, Solomon EI, Kovacs JA. How does single oxygen atom addition affect the properties of an Fe-nitrile hydratase analogue? The compensatory role of the unmodified thiolate. J Am Chem Soc 2006; 128:11211-21. [PMID: 16925440 PMCID: PMC4481871 DOI: 10.1021/ja062706k] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nitrile hydratase (NHase) is one of a growing number of enzymes shown to contain post-translationally modified cysteine sulfenic acids (Cys-SOH). Cysteine sulfenic acids have been shown to play diverse roles in cellular processes, including transcriptional regulation, signal transduction, and the regulation of oxygen metabolism and oxidative stress responses. The function of the cysteine sulfenic acid coordinated to the iron active site of NHase is unknown. Herein we report the first example of a sulfenate-ligated iron complex, [Fe(III)(ADIT)(ADIT-O)](+) (5), and compare its electronic and magnetic properties with those of structurally related complexes in which the sulfur oxidation state and protonation state have been systematically altered. Oxygen atom addition was found to decrease the unmodified thiolate Fe-S bond length and blue-shift the ligand-to-metal charge-transfer band (without loss of intensity). S K-edge X-ray absorption spectroscopy and density functional theory calculations show that, although the modified RS-O(-) fragment is incapable of forming a pi bond with the Fe(III) center, the unmodified thiolate compensates for this loss of pi bonding by increasing its covalent bond strength. The redox potential shifts only slightly (75 mV), and the magnetic properties are not affected (the S = (1)/(2) spin state is maintained). The coordinated sulfenate S-O bond is activated and fairly polarized (S(+)-O(-)). Addition of strong acids at low temperatures results in the reversible protonation of sulfenate-ligated 5. An X-ray structure demonstrates that Zn(2+) binds to the sulfenate oxygen to afford [Fe(III)(ADIT)(ADIT-O-ZnCl(3))] (6). The coordination of ZnCl(3)(-) to the RS-O(-) unit causes the covalent overlap with the unmodified thiolate to increase further. A possible catalytic role for the unmodified NHase thiolate, involving its ability to "tune" the electronics in response to protonation of the sulfenate (RS-O(-)) oxygen and/or substrate binding, is discussed.
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Affiliation(s)
- Priscilla Lugo-Mas
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, USA
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174
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Miranda-Soto V, Pérez-Torrente JJ, Oro LA, Lahoz FJ, Martín ML, Parra-Hake M, Grotjahn DB. Effects of the Heterocycle and Its Substituents on Structure and Fluxionality in Rhodium(I) and Iridium(I) Complexes with the Hindered Thiolates 6-tert-Butylpyridine-2-thiolate and 1-Alkyl-4-tert-butylimidazole-2-thiolate (alkyl = methyl and tert-butyl). Organometallics 2006. [DOI: 10.1021/om060317t] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Valentín Miranda-Soto
- Centro de Graduados e Investigación, Instituto Tecnológico de Tijuana, Apartado Postal 1166, 22000 Tijuana, Baja California, México, and Departamento de Química Inorgánica, Instituto Universitario de Catálisis Homogénea, Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-Consejo Superior de Investigaciones Científicas, 50009 Zaragoza, Spain, and Department of Chemistry and Biochemistry, San Diego State University, 5500 Campanile Drive, San Diego, California 92182-1030
| | - Jesús J. Pérez-Torrente
- Centro de Graduados e Investigación, Instituto Tecnológico de Tijuana, Apartado Postal 1166, 22000 Tijuana, Baja California, México, and Departamento de Química Inorgánica, Instituto Universitario de Catálisis Homogénea, Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-Consejo Superior de Investigaciones Científicas, 50009 Zaragoza, Spain, and Department of Chemistry and Biochemistry, San Diego State University, 5500 Campanile Drive, San Diego, California 92182-1030
| | - Luis A. Oro
- Centro de Graduados e Investigación, Instituto Tecnológico de Tijuana, Apartado Postal 1166, 22000 Tijuana, Baja California, México, and Departamento de Química Inorgánica, Instituto Universitario de Catálisis Homogénea, Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-Consejo Superior de Investigaciones Científicas, 50009 Zaragoza, Spain, and Department of Chemistry and Biochemistry, San Diego State University, 5500 Campanile Drive, San Diego, California 92182-1030
| | - Fernando J. Lahoz
- Centro de Graduados e Investigación, Instituto Tecnológico de Tijuana, Apartado Postal 1166, 22000 Tijuana, Baja California, México, and Departamento de Química Inorgánica, Instituto Universitario de Catálisis Homogénea, Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-Consejo Superior de Investigaciones Científicas, 50009 Zaragoza, Spain, and Department of Chemistry and Biochemistry, San Diego State University, 5500 Campanile Drive, San Diego, California 92182-1030
| | - M. Luisa Martín
- Centro de Graduados e Investigación, Instituto Tecnológico de Tijuana, Apartado Postal 1166, 22000 Tijuana, Baja California, México, and Departamento de Química Inorgánica, Instituto Universitario de Catálisis Homogénea, Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-Consejo Superior de Investigaciones Científicas, 50009 Zaragoza, Spain, and Department of Chemistry and Biochemistry, San Diego State University, 5500 Campanile Drive, San Diego, California 92182-1030
| | - Miguel Parra-Hake
- Centro de Graduados e Investigación, Instituto Tecnológico de Tijuana, Apartado Postal 1166, 22000 Tijuana, Baja California, México, and Departamento de Química Inorgánica, Instituto Universitario de Catálisis Homogénea, Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-Consejo Superior de Investigaciones Científicas, 50009 Zaragoza, Spain, and Department of Chemistry and Biochemistry, San Diego State University, 5500 Campanile Drive, San Diego, California 92182-1030
| | - Douglas B. Grotjahn
- Centro de Graduados e Investigación, Instituto Tecnológico de Tijuana, Apartado Postal 1166, 22000 Tijuana, Baja California, México, and Departamento de Química Inorgánica, Instituto Universitario de Catálisis Homogénea, Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-Consejo Superior de Investigaciones Científicas, 50009 Zaragoza, Spain, and Department of Chemistry and Biochemistry, San Diego State University, 5500 Campanile Drive, San Diego, California 92182-1030
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175
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Greene SN, Richards NGJ. Electronic structure, bonding, spectroscopy and energetics of Fe-dependent nitrile hydratase active-site models. Inorg Chem 2006; 45:17-36. [PMID: 16390037 DOI: 10.1021/ic050965p] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Fe-type nitrile hydratase (NHase) is a non-heme Fe(III)-dependent enzyme that catalyzes the hydration of nitriles to the corresponding amides. Despite experimental studies of the enzyme and model Fe(III)-containing complexes, many questions concerning the electronic structure and spectroscopic transitions of the metal center remain unanswered. In addition, the catalytic mechanism of nitrile hydration has not yet been determined. We now report density functional theory (B3LYP/6-31G) calculations on three models of the Fe(III) center in the active site of NHase corresponding to hypothetical intermediates in the enzyme-catalyzed hydration of acetonitrile. Together with natural bond orbital (NBO) analysis of the chemical bonding in these active-site models and INDO/S CIS calculations of their electronic spectra, this theoretical investigation gives new insight into the molecular origin of the unusual low-spin preference and spectroscopic properties of the Fe(III) center. In addition, the low-energy electronic transition observed for the active form of NHase is assigned to a dd transition that is coupled with charge-transfer transitions involving the metal and its sulfur ligands. Calculations of isodesmic ligand-exchange reaction energies provide support for coordination of the Fe(III) center in free NHase by a water molecule rather than a hydroxide ion and suggest that the activation of the nitrile substrate by binding to the metal in the sixth coordination site during catalytic turnover cannot yet be definitively ruled out.
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Affiliation(s)
- Shannon N Greene
- Department of Chemistry, University of Florida, Gainesville, 32611-7200, USA
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176
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Khandar AA, Shaabani B, Belaj F, Bakhtiari A. Synthesis, characterization and spectroscopic and electrochemical studies of new axially coordinated cobalt(III) salen (salen=N,N′-bis(salicylidene)-1,2-ethylenediamine) complexes. The crystal structure of [CoIII(salen)(aniline)2]ClO4. Polyhedron 2006. [DOI: 10.1016/j.poly.2005.12.001] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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177
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Dey A, Chow M, Taniguchi K, Lugo-Mas P, Davin S, Maeda M, Kovacs JA, Odaka M, Hodgson KO, Hedman B, Solomon EI. Sulfur K-edge XAS and DFT calculations on nitrile hydratase: geometric and electronic structure of the non-heme iron active site. J Am Chem Soc 2006; 128:533-41. [PMID: 16402841 PMCID: PMC4485618 DOI: 10.1021/ja0549695] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The geometric and electronic structure of the active site of the non-heme iron enzyme nitrile hydratase (NHase) is studied using sulfur K-edge XAS and DFT calculations. Using thiolate (RS(-))-, sulfenate (RSO(-))-, and sulfinate (RSO(2)(-))-ligated model complexes to provide benchmark spectral parameters, the results show that the S K-edge XAS is sensitive to the oxidation state of S-containing ligands and that the spectrum of the RSO(-) species changes upon protonation as the S-O bond is elongated (by approximately 0.1 A). These signature features are used to identify the three cysteine residues coordinated to the low-spin Fe(III) in the active site of NHase as CysS(-), CysSOH, and CysSO(2)(-) both in the NO-bound inactive form and in the photolyzed active form. These results are correlated to geometry-optimized DFT calculations. The pre-edge region of the X-ray absorption spectrum is sensitive to the Z(eff) of the Fe and reveals that the Fe in [FeNO](6) NHase species has a Z(eff) very similar to that of its photolyzed Fe(III) counterpart. DFT calculations reveal that this results from the strong pi back-bonding into the pi antibonding orbital of NO, which shifts significant charge from the formally t(2)(6) low-spin metal to the coordinated NO.
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Affiliation(s)
- Abhishek Dey
- Department of Chemistry, Stanford University, Stanford, California 94305
| | - Marina Chow
- Department of Chemistry, Stanford University, Stanford, California 94305
| | | | - Priscilla Lugo-Mas
- Department of Chemistry, University of Washington, Seattle, Washington 98195
| | - Steven Davin
- Department of Chemistry, University of Washington, Seattle, Washington 98195
| | - Mizuo Maeda
- Bioengineering Laboratory, RIKEN, Wako, Saitama 351-0198, Japan
| | - Julie A. Kovacs
- Department of Chemistry, University of Washington, Seattle, Washington 98195
| | - Masafumi Odaka
- Bioengineering Laboratory, RIKEN, Wako, Saitama 351-0198, Japan
| | - Keith O. Hodgson
- Department of Chemistry, Stanford University, Stanford, California 94305
- Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, California 94309
| | - Britt Hedman
- Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, California 94309
| | - Edward I. Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305
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178
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Chiang CY, Darensbourg MY. Iron nitrosyl complexes as models for biological nitric oxide transfer reagents. J Biol Inorg Chem 2006; 11:359-70. [PMID: 16520978 DOI: 10.1007/s00775-006-0084-y] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2005] [Accepted: 01/24/2006] [Indexed: 11/26/2022]
Abstract
Owing to the indiscriminate reactivity of the free NO radical, intricate control mechanisms are required for storage, transport and transfer of NO to its various biological targets. Among the proposed storage components are protein-bound thionitrosyls (Rprotein-SNO) and protein-bound dinitrosyl iron complexes. Current knowledge suggests the latter are derived from iron-sulfur cluster degradation in the presence of excess NO. Mobilization of protein-bound NO could involve NO or Fe(NO)2 unit transfer to small serum molecules such as glutathione, free cysteine, or iron-porphyrins. The study reported is of a reaction model which addresses the key steps in NO transfer from a prototypal iron dinitrosyl complex. While the N,N'-bis(2-mercaptoethyl)-N,N'-diazacyclooctane (bme-daco) ligand typically binds in square-planar N2S2 coordination, it also serves as a bidentate dithiolate donor for tetrahedral structures in the preparation of the (H+bme-daco)Fe(NO)2 derivative (Chiang et al., J. Am. Chem. Soc. 126:10867-10874, 2004). The removal of one NO produces the mononitrosyl complex, (bme-daco)Fe(NO), and simplifies studies of NO release mechanisms. We have used heme-type model complexes, Fe or Co porphyrins as NO acceptors, yielding (porphyrin)M(NO), where M is Fe or Co, and monitored reactions by nu(NO) Fourier transform IR spectroscopy. Reaction products were verified by electrospray ionization mass spectrometry. Rudimentary mechanistic studies suggest a role for HNO in the NO release from the dinitrosyl; the mononitrosyl benefits as well from acid catalysis. Other NO uptake complexes such as [(N2S2)Fe]2 [N2S2 is bme-daco or N,N'-bis(2-mercapto-2-methylpropyl)-daco] are shown to form Fe(NO) mononitrosyls with stability and spectroscopic signatures similar to those of the porphyrins.
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Affiliation(s)
- Chao-Yi Chiang
- Department of Chemistry, Texas A&M University, College Station, TX 77843, USA
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179
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Harrop TC, Olmstead MM, Mascharak PK. Modeling the Active Site of Nitrile Hydratase: Synthetic Strategies to Ensure Simultaneous Coordination of Carboxamido-N and Thiolato-S to Fe(III) Centers. Inorg Chem 2005; 44:9527-33. [PMID: 16323940 DOI: 10.1021/ic051183z] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A general strategy for synthesizing Fe(III) complexes of ligands containing carboxamido-N and thiolato-S donors has been described. Reaction of the doubly deprotonated ligand PyPepS2- (where PyPepSH2=N-2-mercaptophenyl-2'-pyridinecarboxamide) with Fe(III) salts in DMF had previously afforded the Fe(III) complex (Et4N)[Fe(PyPepS)2] without any problem(s) associated with autoredox reactions of the thiolate functionality. In the present work, similar reactions with the doubly deprotonated ligand PiPepS2- (where PiPepSH2=2-mercapto-N-pyridin-2-yl-methylbenzamide) with Fe(III) salts, however, fail to afford any Fe(III) complex because of autoredox reactions. The break in the conjugation in the PiPepSH2 ligand frame is the key reason for this difference in behavior between these two very similar ligands. This is demonstrated by the fact that the same reaction with AqPepS2- (where AqPepSH2=2-mercapto-N-quinolin-8-yl-benzamide), another ligand with extended conjugation, affords the Fe(III) complex (Et4N)[Fe(AqPepS)2] without any synthetic complication. It is therefore evident that ligands in which the carboxamide and thiolate functionalities are kept in conjugation could be used to isolate Fe(III) complexes with carboxamido-N and thiolato-S coordination. This finding will be very helpful in future research work in the area of modeling the active site of Fe-containing nitrile hydratase.
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Affiliation(s)
- Todd C Harrop
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, USA
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180
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Nayak S, Dash AC, Nayak PK, Das D. Kinetics and Mechanism of the Formation of (1,5)bis(2-hydroxybenzamido)3- azapentaneiron(III) and its Reactions with Thiocyanate, Azide, Acetate, Sulfur(IV) and Ascorbic Acid in Solution, and the Synthesis and Characterization of (nitrato)bis- (2-hydroxybenzamido)3-azapentaneiron(III). The Role of Phenol–amide–amine Coordination. TRANSIT METAL CHEM 2005. [DOI: 10.1007/s11243-005-5627-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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181
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Synthesis and Structural Characterisation of Two Copper(II) Complexes of N-(1-acetyl-2-propylidene) (2-pyridylmethyl) amine. Struct Chem 2005. [DOI: 10.1007/s11224-005-6057-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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182
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Bourles E, Alves de Sousa R, Galardon E, Giorgi M, Artaud I. Direct Synthesis of a Thiolato-S and Sulfinato-S CoIII Complex Related to the Active Site of Nitrile Hydratase: A Pathway to the Post-Translational Oxidation of the Protein. Angew Chem Int Ed Engl 2005; 44:6162-5. [PMID: 16136617 DOI: 10.1002/anie.200500814] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Emilie Bourles
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR8601 CNRS, Université René Descartes, 45 rue des Sts pères, 75270 Paris Cedex 06, France
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183
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Bourles E, Alves de Sousa R, Galardon E, Giorgi M, Artaud I. Direct Synthesis of a Thiolato-S and Sulfinato-S CoIII Complex Related to the Active Site of Nitrile Hydratase: A Pathway to the Post-Translational Oxidation of the Protein. Angew Chem Int Ed Engl 2005. [DOI: 10.1002/ange.200500814] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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184
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Bricks JL, Kovalchuk A, Trieflinger C, Nofz M, Büschel M, Tolmachev AI, Daub J, Rurack K. On the Development of Sensor Molecules that Display FeIII-amplified Fluorescence. J Am Chem Soc 2005; 127:13522-9. [PMID: 16190715 DOI: 10.1021/ja050652t] [Citation(s) in RCA: 461] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Incorporation of a tailor-made size-restricted dithia-aza-oxa macrocycle, 1-oxa-4,10-dithia-7-aza-cyclododecane, via a phenyl linker into two fluorescent sensor molecules with electronically decoupled, rigidly fixed, and sterically preoriented architectures, a 1,3,5-triaryl-Delta2-pyrazoline and a meso-substituted boron-dipyrromethene (BDP), yields amplified fluorescence in the red-visible spectral range upon binding of Fe(III) ions. The response to Fe(III) and potentially interfering metal ions is studied in highly polar aprotic and protic solvents for both probes as well as in neat and buffered aqueous solution for one of the sensor molecules, the BDP derivative. In organic solvents, the fluorescence of both indicators is quenched by an intramolecular charge or electron transfer in the excited state and coordination of Fe(III) leads to a revival of their fluorescence without pronounced spectral shifts. Most remarkably, the unbound BDP derivative shows dual emission in water and can be employed for the selective ratiometric signaling of Fe(III) in buffered aqueous solutions.
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Affiliation(s)
- Julia L Bricks
- Institute of Organic Chemistry, National Academy of Sciences of the Ukraine, 02094 Kiev, Ukraine.
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185
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Lee CM, Chen CH, Chen HW, Hsu JL, Lee GH, Liaw WF. Nitrosylated Iron−Thiolate−Sulfinate Complexes with {Fe(NO)}6/7 Electronic Cores: Relevance to the Transformation between the Active and Inactive NO-Bound Forms of Iron-Containing Nitrile Hydratases. Inorg Chem 2005; 44:6670-9. [PMID: 16156625 DOI: 10.1021/ic050108l] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The five-coordinated iron-thiolate nitrosyl complexes [(NO)Fe(S,S-C6H3R)2]- (R = H (1), m-CH3 (2)), [(NO)Fe(S,S-C6H2-3,6-Cl2)2]- (3), [(NO)Fe(S,S-C6H3R)2]2- (R = H (10), m-CH3 (11)), and [(NO)Fe(S,S-C6H2-3,6-Cl2)2]2- (12) have been isolated and structurally characterized. Sulfur oxygenation of iron-thiolate nitrosyl complexes 1-3 containing the {Fe(NO)}6 core was triggered by O2 to yield the S-bonded monosulfinate iron species [(NO)Fe(S,SO2-C6H3R)(S,S-C6H3R)]- (R = H (4), m-CH3 (5)) and [(NO)Fe(S,SO2-C6H2-3,6-Cl2)(S,S-C6H2-3,6-Cl2)]2(2-) (6), respectively. In contrast, attack of O2 on the {Fe(NO)}7 complex 10 led to the formation of complex 1 accompanied by the minor products, [Fe(S,S-C6H4)2]2(2-) and [NO3]- (yield 9%). Reduction of complexes 4-6 by [EtS]- in CH3CN-THF yielded [(NO)Fe(S,SO2-C6H3R)(S,S-C6H3R)]2- (R = H (7), m-CH3 (8)) and [(NO)Fe(S,SO2-C6H2-3,6-Cl2)(S,S-C6H2-3,6-Cl2)]2- (9) along with (EtS)2 identified by 1H NMR. Compared to complex 10, complexes 7-9 with the less electron-donating sulfinate ligand coordinated to the {Fe(NO)}7 core were oxidized by O2 to yield complexes 4-6. Obviously, the electronic perturbation of the {Fe(NO)}7 core caused by the coordinated sulfinate in complexes 7-9 may serve to regulate the reactivity of complexes 7-9 toward O2. The iron-sulfinate nitrosyl species with the {Fe(NO)}6/7 core exhibit the photolabilization of sulfur-bound [O] moiety. Complexes 1-4-7-10 (or 2-5-8-11 and 3-6-9-12) are interconvertible under sulfur oxygenation, redox processes, and photolysis, respectively.
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Affiliation(s)
- Chien-Ming Lee
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
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186
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Singh AK, Mukherjee R. Bivalent and Trivalent Iron Complexes of Acyclic Hexadentate Ligands Providing Pyridyl/Pyrazine−Amide−Thioether Coordination. Inorg Chem 2005; 44:5813-9. [PMID: 16060634 DOI: 10.1021/ic050057s] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Acyclic pyridine-2-carboxamide- and thioether-containing hexadentate ligand 1,4-bis[o-(pyridine-2-carboxamidophenyl)]-1,4-dithiobutane (H(2)bpctb), in its deprotonated form, has afforded purple low-spin (S = 0) iron(II) complex [Fe(bpctb)] (1). A new ligand, the pyrazine derivative of H(2)bpctb, 1,4-bis[o-(pyrazine-2-carboxamidophenyl)]-1,4-dithiobutane (H(2)bpzctb), has been synthesized which has furnished the isolation of purple iron(II) complex [Fe(bpzctb)].CH(2)Cl(2) (4) (S = 0). Chemical oxidation of 1 by [(eta(5)-C(5)H(5))(2)Fe][PF(6)] or [Ce(NO(3))(6)][NH(4)](2) led to the isolation of low-spin (S = 1/2) green Fe(III) complexes [Fe(bpctb)][PF(6)] (2) or [Fe(bpctb)][NO(3)].H(2)O (3), and oxidation of 4 by [Ce(NO(3))(6)][NH(4)](2) afforded [Fe(bpzctb)][NO(3)].H(2)O (5) (S = 1/2). X-ray crystal structures of 1 and 4 revealed that (i) in each case the ligand coordinates in a hexadentate mode and (ii) bpzctb(2-) binds more strongly than bpctb(2-), affording distorted octahedral M(II)N(2)(pyridine/pyrazine)N'(2)(amide)S(2)(thioether) coordination. To the best of our knowledge, 1 and 4 are the first examples of six-coordinate low-spin Fe(II) complexes of deprotonated pyridine/pyrazine amide ligands having appended thioether functionality. The Fe(III) complexes display rhombic EPR spectra. Each complex exhibits in CH(2)Cl(2)/MeCN a reversible to quasireversible cyclic voltammetric response, corresponding to the Fe(III)-Fe(II) redox process. The E(1/2) value of 4 is more anodic by approximately 0.2 V than that of 1, attesting that compared to pyridine, pyrazine is a better stabilizer of iron(II). Moreover, the E(1/2) value of 1 is significantly higher (approximately 1.5 V) than that reported for six-coordinate Fe(II)/Fe(III) complexes of the tridentate pyridine-2-carboxamide ligand incorporating thiolate donor site.
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187
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Synthesis, characterization and X-ray crystal structures of copper(II) and nickel(II) complexes with potentially hexadentate Schiff base ligands. Inorganica Chim Acta 2005. [DOI: 10.1016/j.ica.2005.04.028] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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188
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Kennepohl P, Neese F, Schweitzer D, Jackson HL, Kovacs JA, Solomon EI. Spectroscopy of non-heme iron thiolate complexes: insight into the electronic structure of the low-spin active site of nitrile hydratase. Inorg Chem 2005; 44:1826-36. [PMID: 15762709 PMCID: PMC4489710 DOI: 10.1021/ic0487068] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Detailed spectroscopic and computational studies of the low-spin iron complexes [Fe(III)(S2(Me2)N3 (Pr,Pr))(N3)] (1) and [Fe(III)(S2(Me2)N3 (Pr,Pr))]1+ (2) were performed to investigate the unique electronic features of these species and their relation to the low-spin ferric active sites of nitrile hydratases. Low-temperature UV/vis/NIR and MCD spectra of 1 and 2 reflect electronic structures that are dominated by antibonding interactions of the Fe 3d manifold and the equatorial thiolate S 3p orbitals. The six-coordinate complex 1 exhibits a low-energy S(pi) --> Fe 3d(xy) (approximately 13,000 cm(-1)) charge-transfer transition that results predominantly from the low energy of the singly occupied Fe 3d(xy) orbital, due to pure pi interactions between this acceptor orbital and both thiolate donor ligands in the equatorial plane. The 3d(pi) --> 3d(sigma) ligand-field transitions in this species occur at higher energies (>15,000 cm(-1)), reflecting its near-octahedral symmetry. The Fe 3d(xz,yz) --> Fe 3d(xy) (d(pi) --> d(pi)) transition occurs in the near-IR and probes the Fe(III)-S pi-donor bond; this transition reveals vibronic structure that reflects the strength of this bond (nu(e) approximately 340 cm(-1)). In contrast, the ligand-field transitions of the five-coordinate complex 2 are generally at low energy, and the S(pi) --> Fe charge-transfer transitions occur at much higher energies relative to those in 1. This reflects changes in thiolate bonding in the equatorial plane involving the Fe 3d(xy) and Fe 3d(x2-y2) orbitals. The spectroscopic data lead to a simple bonding model that focuses on the sigma and pi interactions between the ferric ion and the equatorial thiolate ligands, which depend on the S-Fe-S bond angle in each of the complexes. These electronic descriptions provide insight into the unusual S = 1/2 ground spin state of these complexes: the orientation of the thiolate ligands in these complexes restricts their pi-donor interactions to the equatorial plane and enforces a low-spin state. These anisotropic orbital considerations provide some intriguing insights into the possible electronic interactions at the active site of nitrile hydratases and form the foundation for further studies into these low-spin ferric enzymes.
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Affiliation(s)
- Pierre Kennepohl
- Departments of Chemistry, Stanford University, Stanford, California 94305
| | - Frank Neese
- Departments of Chemistry, Stanford University, Stanford, California 94305
| | | | | | - Julie A. Kovacs
- University of Washington, Seattle, Washington 98195
- Corresponding authors. (J.A.K.), (E.I.S.)
| | - Edward I. Solomon
- Departments of Chemistry, Stanford University, Stanford, California 94305
- Corresponding authors. (J.A.K.), (E.I.S.)
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189
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Morgado CA, Mcnamara JP, Hillier * IH, Sundararajan M. The structure and spin-states of some Fe(III) mimics of nitrile hydratase, studied by DFT and ONIOM(DFT:PM3) calculations. Mol Phys 2005. [DOI: 10.1080/00268970512331340583] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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190
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Cantarella M, Cantarella L, Gallifuoco A, Spera A. Nitrile bioconversion by Microbacterium imperiale CBS 498-74 resting cells in batch and ultrafiltration membrane bioreactors. J Ind Microbiol Biotechnol 2005; 33:208-14. [PMID: 15739103 DOI: 10.1007/s10295-004-0200-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2004] [Accepted: 12/02/2004] [Indexed: 10/25/2022]
Abstract
The biohydration of acrylonitrile, propionitrile and benzonitrile catalysed by the NHase activity contained in resting cells of Microbacterium imperiale CBS 498-74 was operated at 5, 10 and 20 degrees C in laboratory-scale batch and membrane bioreactors. The bioreactions were conducted in buffered medium (50 mM Na(2)HPO(4)/NaH(2)PO(4), pH 7.0) in the presence of distilled water or tap-water, to simulate a possible end-pipe biotreatment process. The integral bioreactor performances were studied with a cell loading (dry cell weight; DCW) varying from 0.1 mg(DCW) per reactor to 16 mg(DCW) per reactor, in order to realize near 100% bioconversion of acrylonitrile, propionitrile and benzonitrile without consistent loss of NHase activity.
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Affiliation(s)
- M Cantarella
- Department of Chemistry, Chemical Engineering and Materials, University of L'Aquila, Monteluco di Roio, L'Aquila, 67040, Italy.
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191
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Kumar Singh A, Mukherjee R. Structure and properties of bivalent nickel and copper complexes with pyrazine-amide-thioether coordination: stabilization of trivalent nickel. Dalton Trans 2005:2886-91. [PMID: 16094477 DOI: 10.1039/b504893a] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Acyclic pyrazine-2-carboxamide and thioether containing hexadentate ligand 1,4-bis[o-(pyrazine-2-carboxamidophenyl)]-1,4-dithiobutane (H(2)bpzctb), in its deprotonated form, has afforded light brown [Ni(II)(bpzctb)](1)(S=1) and green [Cu(II)(bpzctb)](2)(S=1/2) complexes. The crystal structures of 1.CH(3)OH and 2.CH(2)Cl(2) revealed that in these complexes the ligand coordinates in a hexadentate mode, affording examples of distorted octahedral M(II)N(2)(pyrazine)N'(2)(amide)S(2)(thioether) coordination. Each complex exhibits in CH(2)Cl(2) a reversible to quasireversible cyclic voltammetric response, corresponding to the Ni(III)/Ni(II)(1) and Cu(II)/Cu(I)(2) redox process. The E(1/2) values reveal that the complexes of bpzctb(2-) are uniformly more anodic by approximately 0.2 V than those of the corresponding complexes with the analogous pyridine ligand, 1,4-bis[o-(pyridine-2-carboxamidophenyl)]-1,4-dithiobutane (H(2)bpctb), attesting that compared to pyridine, pyrazine is a better stabilizer of the Ni(ii) or Cu(i) state. Coulometric oxidation of the previously reported complex [Ni(II)(bpctb)] and 1 generates [Ni(III)(bpctb)](+) and [Ni(III)(bpzctb)](+) species, which exhibit a LMCT transition in the 470--480 nm region and axial EPR spectra corresponding to a tetragonally elongated octahedral geometry. Complex 2 exhibits EPR spectra characteristic of the d(z(2)) ground state.
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Affiliation(s)
- Akhilesh Kumar Singh
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016, India
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192
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Greene SN, Richards NGJ. Theoretical investigations of the electronic structure and spectroscopy of mononuclear, non-heme [Fe-NO](6) complexes. Inorg Chem 2004; 43:7030-41. [PMID: 15500340 DOI: 10.1021/ic0499695] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The unusual metal coordination and spin-state of the Fe(III) center in nitrile hydratase (NHase) has stimulated the synthesis of numerous model complexes in efforts to understand the reactivity and spectroscopic properties of the enzyme. A particular problem has been the development of model Fe(III) complexes that exhibit reversible, photolabile binding to nitric oxide (NO) in a manner similar to that observed for the NHase metal center. We now report a detailed NBO analysis of the ground-state chemical bonding in three [Fe-NO](6) complexes that exhibit different responses to irradiation, together with investigations of their spectroscopic properties using semiempirical INDO/S CI singles calculations. Our computational studies reveal a correlation between the photolability of these complexes and the existence of low-energy transitions that promote an electron into the Fe-NO pi(*) antibonding molecular orbital. In addition to providing detailed insights into how the ligand field influences the spectroscopy of these mononuclear complexes, these studies strengthen our previous conclusions regarding the role of post-translational cysteine modification in modulating the photoreactivity of the inactive, NO complex of NHase.
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Affiliation(s)
- Shannon N Greene
- Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, USA
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193
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194
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Theisen RM, Shearer J, Kaminsky W, Kovacs JA. Steric and electronic control over the reactivity of a thiolate-ligated Fe(II) complex with dioxygen and superoxide: reversible mu-oxo dimer formation. Inorg Chem 2004; 43:7682-90. [PMID: 15554633 PMCID: PMC4485619 DOI: 10.1021/ic0491884] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The reactivity between a thiolate-ligated five-coordinate complex [FeII(SMe2N4(tren))]+ (1) and dioxygen is examined in order to determine if O2 activation, resembling that of the metalloenzyme cytochrome P450, can be promoted even when O2 binds cis, as opposed to trans, to a thiolate. Previous work in our group showed that [FeII(SMe2N4(tren))]+ (1) reacts readily with superoxide (O2-) in the presence of a proton source to afford H2O2 via an Fe(III)-OOH intermediate, thus providing a biomimetic model for the metalloenzyme superoxide reductase (SOR). Addition of O2 to 1 affords binuclear mu-oxo-bridged [FeIII(SMe2N4(tren))]2(mu2-O)(PF6)2.3MeCN (3). At low temperatures, in protic solvents, an intermediate is detected, the details of which will be the subject of a separate paper. Although the thiolate ligand does not appear to perturb the metrical parameters of the unsupported mu-oxo bridge (Fe-O= 1.807(8) A, and Fe-O-Fe= 155.3(5) degrees fall in the usual range), it decreases the magnetic coupling between the irons (J=-28 cm(-1)) and creates a rather basic oxo site. Protonation of this oxo using strong (HBF4, HCl) or weak (HOAc, NH4PF6, LutNHCl) acids results in bridge cleavage to cleanly afford the corresponding monomeric anion-ligated (OAc- (6), or Cl- (7)) or solvent-ligated (MeCN (4)) derivatives. Addition of OH- converts [FeIII(SMe2N4(tren))(MeCN2+ (4) back to mu-oxo 3. Thus, mu-oxo bridge cleavage is reversible. The protonated mu-hydroxo-bridged intermediate is not observed. In an attempt to prevent mu-oxo dimer formation, and facilitate the observation of O2-bound intermediates, a bulkier tertiary amine ligand, tren-Et4= N-(2-amino-ethyl)-N-(2-diethylamino-ethyl)-N',N'-diethyl-ethane-1,2-diamine, and the corresponding [FeII(SMe2N4(tren-Et4))]+ (5) complex was synthesized and structurally characterized. Steric repulsive interactions create unusually long FeII-N(3,4) amine bonds in 5 (mean distance=2.219(1) A). The [(tren-Et4)N4SMe2]1- ligand is unable to accommodate iron in the +3 oxidation state, and consequently, in contrast to most thiolate-ligated Fe(II) complexes, [FeII(SMe2N4(tren-Et4))]+ (5) does not readily react with O2. Oxidation of 5 is irreversible, and the potential (Epa=+410 mV (vs SCE)) is anodically shifted relative to 1 (E1/2=-100 mV (vs SCE)).
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Affiliation(s)
- Roslyn M. Theisen
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700
| | - Jason Shearer
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700
| | | | - Julie A. Kovacs
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700
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195
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Golden ML, Reibenspies JH, Darensbourg MY. Accommodation of the irregular coordination geometry of lead(II) by a square planar N2S2 ligand and its preference for zinc(II). Inorg Chem 2004; 43:5798-800. [PMID: 15360227 DOI: 10.1021/ic049489d] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The N2S2 ligand, bis-mercaptoethanediazacyclooctane, coordinates to Pb(II) largely through sulfur donors, enlisting a second unit to fulfill an irregular, hemispherical N2S3 coordination environment in which a void suggests the location of a stereochemically active lone pair on Pb(II). That the highly exposed lead is vulnerable to metal ion displacement is demonstrated on reaction with zinc which results in a regular square pyramidal coordination about zinc within a [N2S2Zn]2 dimer. Analysis of the two dimeric structures finds different connectivities of the monomeric subunits account for the stability of the zinc structure over that of the lead.
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Affiliation(s)
- Melissa L Golden
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, USA
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196
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197
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Chiang CY, Miller ML, Reibenspies JH, Darensbourg MY. Bismercaptoethanediazacyclooctane as a N2S2 Chelating Agent and Cys−X−Cys Mimic for Fe(NO) and Fe(NO)2. J Am Chem Soc 2004; 126:10867-74. [PMID: 15339171 DOI: 10.1021/ja049627y] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The N-protonated bismercaptoethanediazacyclooctane serves as a bidentate dithiolate ligand to oxidized Fe(NO)(2) of Enemark-Feltam notation, E-F [Fe(NO)(2)],(9) mimicking Cys-X-Cys binding of Fe(NO)(2) to proteins or thio-biomolecules. The neutral compound is characterized by the well-known g = 2.03 EPR signal which is a hallmark of dinitrosyl iron complexes, DNIC's. The Fe(NO)(2) unit can be removed from the chelate by excess PhS(-), producing (PhS)(2)Fe(NO)(2)(-). Transfer of NO from Fe(H(+)bme-daco)(NO)(2) (nu(NO) = 1740, 1696 cm(-)(1)) to Fe(II) of [(bme-daco)Fe](2) yields the five-coordinate, square-pyramidal N(2)S(2)Fe(NO) (nu(NO) = 1649 cm(-)(1)), where NO is in the apical position. Its isotropic EPR signal at g = 2.05 is consistent with E-F [Fe(NO)](7) formulation. In excess NO, Roussin's red ester-type molecules are formed as dinuclear or tetranuclear species, [(micro-SRS)[Fe(2)(NO)(4)]](n)() (n =1, 2). These well-characterized molecules furnish reference points for positions and patterns in nu(NO) vibrational spectroscopy expected to be useful for in vivo studies of NO degradation of iron-sulfur clusters in ferredoxins.
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Affiliation(s)
- Chao-Yi Chiang
- Contribution from the Department of Chemistry, Texas A&M University, College Station, TX 77843, USA
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198
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Bis-axial cyanide coordination induces high nucleophilicity of the in-plane thiolato ligands bound to a Co(III) center: model complexes related to the Co-containing nitrile hydratases. Inorganica Chim Acta 2004. [DOI: 10.1016/j.ica.2004.02.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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199
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Rotthaus O, LeRoy S, Tomas A, Barkigia K, Artaud I. A New Family of Low-Spin CoIII Bis(amidate) Complexes with Twocis ortrans Cyanides. Eur J Inorg Chem 2004. [DOI: 10.1002/ejic.200300645] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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200
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Grapperhaus CA, Mullins CS, Kozlowski PM, Mashuta MS. Synthesis and Oxygenation of a Nickel(II) and Zinc(II) Dithiolate: An Experimental and Theoretical Comparison. Inorg Chem 2004; 43:2859-66. [PMID: 15106973 DOI: 10.1021/ic035205y] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The diamino-dithiolato N2S2 ligand N,N'-bis-2-methyl-mercaptopropyl-N,N'-dimethylethylenediamine, H2bmmp-dmed), and its nickel (1) and zinc (2) complexes have been prepared and their reactivities with hydrogen peroxide investigated. Complex 1 yields a mixture of sulfenato (RSO-), 4, sulfinato (RSO2-), 3, and sulfonato (RSO3-), 5, products upon addition of H2O2. Products are separable by column chromatography. Stoichiometric addition of H2O2 to 2 yields an inseparable mixture. Excess peroxide addition results in oxygenation of the ligand to the disulfonate, 6, and decomplexation of zinc. Complexes 1, 2, and 3 and compound 6 have been investigated by X-ray crystallography, and their structures are reported. Density functional theory (DFT) calculations of 1 and 2 reveal significant sulfur p character in the HOMO of each complex. However, 1 also shows significant metal d character that is pi-antibonding with respect to the sulfur p orbitals. Complex 2 shows little metal character in the HOMO. Implications of the HOMO with respect to S-centered reactivity and metal ligand distances in S-oxygenated products are provided.
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Affiliation(s)
- Craig A Grapperhaus
- Department of Chemistry, University of Louisville, Louisville, Kentucky 40292, USA.
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