Copper(II) coordination chemistry of Westiellamide and its imidazole, oxazole, and thiazole analogues

Comba, Peter, Gahan, Lawrence R., Haberhauer, Gebhard, Hanson, Graeme R., Noble, Christopher J., Seibold, Bjoern and van den Brenk, Anna L. (2008) Copper(II) coordination chemistry of Westiellamide and its imidazole, oxazole, and thiazole analogues. Chemistry: A European Journal, 14 14: 4393-4403. doi:10.1002/chem.200701778

Author Comba, Peter
Gahan, Lawrence R.
Haberhauer, Gebhard
Hanson, Graeme R.
Noble, Christopher J.
Seibold, Bjoern
van den Brenk, Anna L.
Title Copper(II) coordination chemistry of Westiellamide and its imidazole, oxazole, and thiazole analogues
Journal name Chemistry: A European Journal   Check publisher's open access policy
ISSN 0947-6539
Publication date 2008-05-09
Sub-type Article (original research)
DOI 10.1002/chem.200701778
Open Access Status
Volume 14
Issue 14
Start page 4393
End page 4403
Total pages 11
Place of publication Weinheim, Germany
Publisher Wiley - V C H
Language eng
Formatted abstract
The copper(II) coordination chemistry of westiellamide (H3Lwa), as well as of three synthetic analogues with an [18]azacrown-6 macrocyclic structure but with three imidazole (H3L1), oxazole (H3L2), and thiazole (H3L3) rings instead of oxazoline, is reported. As in the larger patellamide rings, the Nheterocycle-Npeptide-Nheterocycle binding site is highly preorganized for copper(II) coordination. In contrast to earlier reports, the macrocyclic peptides have been found to form stable mono- and dinuclear copper(II) complexes. The coordination of copper(II) has been monitored by high-resolution electrospray mass spectrometry (ESI-MS), spectrophotometric and polarimetric titrations, and EPR and IR spectroscopies, and the structural assignments have been supported by time-dependent studies (UV/Vis/NIR, ESI-MS, and EPR) of the complexation reaction of copper(II) with H3L1. Density functional theory (DFT) calculations have been used to model the structures of the copper(II) complexes on the basis of their spectroscopic data. The copper(II) ion has a distorted square-pyramidal geometry with one or two coordinated solvent molecules (CH3OH) in the mononuclear copper(II) cyclic peptide complexes, but the coordination sphere in [Cu(H2Lwa)(OHCH3)]+ differs from those in the synthetic analogues, [Cu(H2L)(OHCH3)2]+ (L=L1, L2, L3). Dinuclear copper(II) complexes ([CuII2(HL)(µ-X)]+; X=OCH3, OH; L=L1, L2, L3, Lwa) are observed in the mass spectra. While a dipole-dipole coupled EPR spectrum is observed for the dinuclear copper(II) complex of H3L3, the corresponding complexes with H3L (L=L1, L2, Lwa) are EPR-silent. This may be explained in terms of strong antiferromagnetic coupling (H3L1) and/or a low concentration of the dicopper(II) complexes (H3Lwa, H3L2), in agreement with the mass spectrometric observations.
Keyword Coordination modes
Crown compounds
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: 2009 Higher Education Research Data Collection
School of Chemistry and Molecular Biosciences
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Created: Wed, 18 Mar 2009, 18:20:32 EST by Jennifer Falknau on behalf of School of Chemistry & Molecular Biosciences