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Ebbe Nordlander. Portrait.

Ebbe Nordlander

Professor

Ebbe Nordlander. Portrait.

Zinc Complexes of a Bioinspired Binucleating Ligand Platform - Equilibria in Solution and Structures in the Solid State

Author

  • Simone Woeckel
  • Joanna Galezowska
  • Sebastian Dechert
  • Wolfram Meyer-Klaucke
  • Ebbe Nordlander
  • Franc Meyer

Summary, in English

The zinc(II) coordination chemistry of the bioinspired bis(tetradentate) ligand 3,5-bis{bis[2-(1-methylimidazolyl)methyl]aminomethyl}pyrazole (L) was studied in detail both in solution and in the solid state. Six different species were determined in aqueous solution by means of potentiometry within the pH range 211, namely mononuclear [ZnH2L]4+, dinuclear [Zn2L]4+, [Zn2H1L]3+ and [Zn2H2L]2+, as well as tetranuclear [Zn4H5L2]3+ and [Zn4H6L2]2+. Complexes representing the protonation state of four of these species could be isolated and structurally characterized by X-ray diffraction, namely [ZnH2L(MeCN)](ClO4)4 (1), [Zn2H1L](SO3CF3)3 (4), [Zn2H1L(MeOHOMe)](ClO4)2 (5a), [Zn2H1L(OMe)](ClO4)2 (5b), and [(Zn2H1L)2(mu-O)(mu-OH)](ClO4)3 (6). In addition, a bis(pyrazolato)-bridged complex, [(ZnH1L)2](ClO4)2 (2), was obtained and structurally characterized, and it was found to exhibit ligand dynamics in solution. Both 5a and 5b are likely present in solution, which requires significant plasticity of the Zn...Zn distance (4.21 angstrom in 5a vs. 3.38 angstrom in 5b). Interconversion of 5a and 5b is proposed to be a facile process, supporting the idea that the ZnO2H3Zn moiety is a functionally relevant hydrolytic zincaqua structure in oligozinc metalloenzymes. The tetranuclear complex 6 that features two {Zn2H1L} subunits connected by a central mu-oxido-mu-hydroxido moiety is unprecedented in zinc(II) chemistry. Combining X-ray crystallography with potentiometry, ESI mass spectrometry, as well as NMR and EXAFS spectroscopy has provided a comprehensive picture of the multitude of species present in this rather complex system.

Department/s

  • Chemical Physics

Publishing year

2012

Language

English

Pages

4728-4738

Publication/Series

European Journal of Inorganic Chemistry

Issue

29

Document type

Journal article

Publisher

John Wiley & Sons Inc.

Topic

  • Atom and Molecular Physics and Optics

Keywords

  • Zinc
  • N ligands
  • Pyrazolate li-gands
  • Binuclear complexes
  • Potentiometric titration
  • EXAFS spectroscopy

Status

Published

ISBN/ISSN/Other

  • ISSN: 1099-0682