Journal article
Cobalt(II) "Scorpionate" Complexes as Models for Cobalt-Substituted Zinc Enzymes: Electronic Structure Investigation by High-Frequency and -Field Electron Paramagnetic Resonance Spectroscopy
Journal of the American Chemical Society, Vol.132(14), pp.5241-5253
04/14/2010
DOI: 10.1021/ja910766w
PMID: 20329727
Abstract
A series of complexes of formula Tp(R,R')CoL, where Tp(R,R'-) = hydrotris(3-R,5-R'-pyrazol-1-yl)borate ("scorpionate") anion (R = tert-butyl, R' = H, Me, 2'-thienyl (Tn), L = Cl-, NCS-, NCO-, N-3(-)), has been characterized by electronic absorption spectroscopy in the visible and near-infrared (near-IR) region and by high-frequency and -field electron paramagnetic resonance (HFEPR). Reported here are also crystal structures of seven members of the series that have not been reported previously: R' = H, L = NCO-, N-3(-); R' = Me, L = Cl-, NCS-, NCO-, N-3(-); R' = Tn, L = Cl-, NCS-. These include a structure for Tp(t-Bu,me)CoCl different from that previously reported. All of the investigated complexes contain a four-coordinate cobalt(II) ion (3d(7)) with approximate C-3v point group symmetry about the metal ion and exhibit an S = 3/2 high-spin ground state. The use of HFEPR allows extraction of the full set of intrinsic S = 3/2 spin Hamiltonian parameters (D, E, and g values). The axial zero-field splitting parameter, D, for all investigated Tp(R,R')CoL complexes is always positive, a fact not easily determined by other methods. However, the magnitude of this parameter varies widely: 2.4 cm(-1) <= D <= 12.7 cm(-1), indicating the extreme sensitivity of this parameter to environment. The spin Hamiltonian parameters are combined with estimates of 3d energy levels based on the visible-near-IR spectra to yield ligand-field parameters for these complexes following the angular overlap model (AOM). This description of electronic structure and bonding in pseudotetrahedral cobalt(II) complexes can enhance the understanding of similar sites in metalloproteins, specifically cobalt-substituted zinc enzymes.
Details
- Title: Subtitle
- Cobalt(II) "Scorpionate" Complexes as Models for Cobalt-Substituted Zinc Enzymes: Electronic Structure Investigation by High-Frequency and -Field Electron Paramagnetic Resonance Spectroscopy
- Creators
- J. Krzystek - National High Magnetic Field LaboratoryDale C. Swenson - University of IowaS. A. Zvyagin - National High Magnetic Field LaboratoryDmitry Smirnov - National High Magnetic Field LaboratoryAndrew Ozarowski - National High Magnetic Field LaboratoryJoshua Telser - National High Magnetic Field Laboratory
- Resource Type
- Journal article
- Publication Details
- Journal of the American Chemical Society, Vol.132(14), pp.5241-5253
- Publisher
- Amer Chemical Soc
- DOI
- 10.1021/ja910766w
- PMID
- 20329727
- ISSN
- 0002-7863
- eISSN
- 1520-5126
- Number of pages
- 13
- Grant note
- 5062 / NHMFL UCGP W. M. Keck Foundation; W.M. Keck Foundation DMR 0654118 / NSF; National Science Foundation (NSF) State of Florida Goldenberg Foundation National High Magnetic Field Laboratory DOE; United States Department of Energy (DOE) 0924374 / Division Of Chemistry; National Science Foundation (NSF); NSF - Directorate for Mathematical & Physical Sciences (MPS)
- Language
- English
- Date published
- 04/14/2010
- Academic Unit
- Chemistry
- Record Identifier
- 9984622746302771
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