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

Woeckel, Simone; Galezowska, Joanna; Dechert, Sebastian; Meyer-Klaucke, Wolfram; Nordlander, Ebbe LU and Meyer, Franc (2012) In European Journal of Inorganic Chemistry p.4728-4738
Abstract
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... (More)
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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Zinc, N ligands, Pyrazolate li-gands, Binuclear complexes, Potentiometric titration, EXAFS spectroscopy
in
European Journal of Inorganic Chemistry
issue
29
pages
4728 - 4738
publisher
John Wiley & Sons
external identifiers
  • wos:000309467600024
  • scopus:84867090656
ISSN
1099-0682
DOI
10.1002/ejic.201200269
language
English
LU publication?
yes
id
d69ba1ae-4412-4d15-ac9d-b555176ad206 (old id 3244552)
date added to LUP
2012-12-27 11:14:19
date last changed
2017-01-01 03:16:45
@article{d69ba1ae-4412-4d15-ac9d-b555176ad206,
  abstract     = {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.},
  author       = {Woeckel, Simone and Galezowska, Joanna and Dechert, Sebastian and Meyer-Klaucke, Wolfram and Nordlander, Ebbe and Meyer, Franc},
  issn         = {1099-0682},
  keyword      = {Zinc,N ligands,Pyrazolate li-gands,Binuclear complexes,Potentiometric titration,EXAFS spectroscopy},
  language     = {eng},
  number       = {29},
  pages        = {4728--4738},
  publisher    = {John Wiley & Sons},
  series       = {European Journal of Inorganic Chemistry},
  title        = {Zinc Complexes of a Bioinspired Binucleating Ligand Platform - Equilibria in Solution and Structures in the Solid State},
  url          = {http://dx.doi.org/10.1002/ejic.201200269},
  year         = {2012},
}