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Spectroscopic and Computational Studies of Ni3+ Complexes with Mixed S/N Ligation: Implications for the Active Site of Nickel Superoxide Dismutase.

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Title: Spectroscopic and Computational Studies of Ni3+ Complexes with Mixed S/N Ligation: Implications for the Active Site of Nickel Superoxide Dismutase.
Authors: Fiedler, Adam T.1, Brunold, Thomas C.1 brunold@chem.wisc.edu
Source: Inorganic Chemistry. 10/15/2007, Vol. 46 Issue 21, p8511-8523. 13p. 6 Diagrams, 5 Charts, 9 Graphs.
Subjects: Spectrum analysis, Ligands (Chemistry), Nickel, Superoxides, Metalloenzymes, Electron paramagnetic resonance, Absorption, Amides
Abstract: Both Ni-containing superoxide dismutase (NiSOD) and NiFe hydrogenases feature thiolate-rich active sites that are capable of stabilizing the Ni3+ oxidation state in catalytically relevant species. In an effort to better understand the role of Ni3+—S bonding interactions in these metalloenzymes, we have employed various spectroscopic and computational methods to probe the geometric and electronic structures of three Ni3+ complexes with mixed SIN ligation: [Ni3+(pdtc)2]- (1), [Ni3+(emb)]- (2), and [Ni3+(ema)]- (3) [where pdtc is pyridine-2,6-bis(monothiocarboxylate) and emb and ema are the tetraanions of N,N′-ethylenebis(o-mercaptobenzamide) and N,N′-ethylenebis(2- mercaptoacetamide), respectively]. Each complex has been examined with electronic absorption, magnetic circular dichroism, electron paramagnetic resonance, and resonance Raman (rR) spectroscopies. Detailed assignments of the features observed in the corresponding spectra have been established within the framework of density functional theory calculations that provide remarkably accurate reproductions of the absorption spectra, g values, and vibrational frequencies. Collectively, our spectroscopic and computational studies have yielded experimentally validated electronic-structure descriptions for 1–3 that provide significant insights into the nature of the Ni3+–S bonding interactions. Additionally, the results obtained in these studies reveal that the thermochromism observed for 2 is due to the formation of a dimeric species at reduced temperatures, the structure of which has been determined through computational analysis of viable dimer models. Finally, we have employed the framework established in our spectroscopic and computational studies of the Ni3+ models to carry out a detailed analysis of our rR data of NiSOD obtained previously. Our results indicate that the Ni3+–S bonds in oxidized NiSOD are significantly stronger than those in 1–3 due to the unique mixed amine/amide ligation that is present at the enzyme active site. [ABSTRACT FROM AUTHOR]
Copyright of Inorganic Chemistry is the property of American Chemical Society and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: Spectroscopic and Computational Studies of Ni<superscript>3+</superscript> Complexes with Mixed S/N Ligation: Implications for the Active Site of Nickel Superoxide Dismutase.
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  Data: <searchLink fieldCode="JN" term="%22Inorganic+Chemistry%22">Inorganic Chemistry</searchLink>. 10/15/2007, Vol. 46 Issue 21, p8511-8523. 13p. 6 Diagrams, 5 Charts, 9 Graphs.
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  Data: <searchLink fieldCode="DE" term="%22Spectrum+analysis%22">Spectrum analysis</searchLink><br /><searchLink fieldCode="DE" term="%22Ligands+%28Chemistry%29%22">Ligands (Chemistry)</searchLink><br /><searchLink fieldCode="DE" term="%22Nickel%22">Nickel</searchLink><br /><searchLink fieldCode="DE" term="%22Superoxides%22">Superoxides</searchLink><br /><searchLink fieldCode="DE" term="%22Metalloenzymes%22">Metalloenzymes</searchLink><br /><searchLink fieldCode="DE" term="%22Electron+paramagnetic+resonance%22">Electron paramagnetic resonance</searchLink><br /><searchLink fieldCode="DE" term="%22Absorption%22">Absorption</searchLink><br /><searchLink fieldCode="DE" term="%22Amides%22">Amides</searchLink>
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  Data: Both Ni-containing superoxide dismutase (NiSOD) and NiFe hydrogenases feature thiolate-rich active sites that are capable of stabilizing the Ni3+ oxidation state in catalytically relevant species. In an effort to better understand the role of Ni3+—S bonding interactions in these metalloenzymes, we have employed various spectroscopic and computational methods to probe the geometric and electronic structures of three Ni3+ complexes with mixed SIN ligation: [Ni3+(pdtc)2]- (1), [Ni3+(emb)]- (2), and [Ni3+(ema)]- (3) [where pdtc is pyridine-2,6-bis(monothiocarboxylate) and emb and ema are the tetraanions of N,N′-ethylenebis(o-mercaptobenzamide) and N,N′-ethylenebis(2- mercaptoacetamide), respectively]. Each complex has been examined with electronic absorption, magnetic circular dichroism, electron paramagnetic resonance, and resonance Raman (rR) spectroscopies. Detailed assignments of the features observed in the corresponding spectra have been established within the framework of density functional theory calculations that provide remarkably accurate reproductions of the absorption spectra, g values, and vibrational frequencies. Collectively, our spectroscopic and computational studies have yielded experimentally validated electronic-structure descriptions for 1–3 that provide significant insights into the nature of the Ni3+–S bonding interactions. Additionally, the results obtained in these studies reveal that the thermochromism observed for 2 is due to the formation of a dimeric species at reduced temperatures, the structure of which has been determined through computational analysis of viable dimer models. Finally, we have employed the framework established in our spectroscopic and computational studies of the Ni3+ models to carry out a detailed analysis of our rR data of NiSOD obtained previously. Our results indicate that the Ni3+–S bonds in oxidized NiSOD are significantly stronger than those in 1–3 due to the unique mixed amine/amide ligation that is present at the enzyme active site. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
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  Data: <i>Copyright of Inorganic Chemistry is the property of American Chemical Society and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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        Value: 10.1021/ic061237k
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      – Code: eng
        Text: English
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        PageCount: 13
        StartPage: 8511
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      – SubjectFull: Spectrum analysis
        Type: general
      – SubjectFull: Ligands (Chemistry)
        Type: general
      – SubjectFull: Nickel
        Type: general
      – SubjectFull: Superoxides
        Type: general
      – SubjectFull: Metalloenzymes
        Type: general
      – SubjectFull: Electron paramagnetic resonance
        Type: general
      – SubjectFull: Absorption
        Type: general
      – SubjectFull: Amides
        Type: general
    Titles:
      – TitleFull: Spectroscopic and Computational Studies of Ni3+ Complexes with Mixed S/N Ligation: Implications for the Active Site of Nickel Superoxide Dismutase.
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            NameFull: Fiedler, Adam T.
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            NameFull: Brunold, Thomas C.
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            – D: 15
              M: 10
              Text: 10/15/2007
              Type: published
              Y: 2007
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              Value: 46
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              Value: 21
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            – TitleFull: Inorganic Chemistry
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