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Electronic Paramagnetic Resonance and Magnetic Properties of Model Complexes for Binuclear Active Sites in Hydrolase Enzymes

Schultz, Brian E. and Ye, Bao-Hui and Li, Xiao-yuan and Chan, Sunney I. (1997) Electronic Paramagnetic Resonance and Magnetic Properties of Model Complexes for Binuclear Active Sites in Hydrolase Enzymes. Inorganic Chemistry, 36 (12). pp. 2617-2622. ISSN 0020-1669. https://resolver.caltech.edu/CaltechAUTHORS:20180529-113543917

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Abstract

A set of binuclear metal complexes with the formula M_2(Im)_4(OAc)_4(H_2O), where M = Mn, Co, or Ni, designed as mimics of the active sites of hydrolase enzymes, were subjected to EPR and magnetic susceptibility studies. The manganese complex displayed a broad EPR spectrum over the field range 0−5500 G. The 4 K spectrum was simulated as a summation of the S = 1, S = 2, and S = 3 spin manifolds of the coupled dimer, with each manifold weighted by the appropriate Boltzmann factor. Parameters for the best fits of EPR and magnetic susceptibility were g = 1.95, J = −1.29 cm^(-1), and D = 0.095 cm^(-1), with line widths of 350, 450, and 550 G for the S = 1, 2, and 3 manifolds, respectively. An alternative simulation, with g = 1.93, J = −1.28 cm^(-1), and D = 0.081 cm^(-1) provided a better fit for the central peaks but only accounted for six of the seven observed peaks. The cobalt and nickel complexes are EPR-silent. Magnetic susceptibility measurements of these two dimers showed weak antiferromagnetic coupling; variable-temperature magnetic susceptibility plots were fit with the parameters g = 2.22, J = −1.60 cm^(-1) (cobalt) and g = 2.04, J = −2.47 cm^(-1) (nickel). The weak coupling highlights the difficulty in detecting bound water in these binuclear complexes or in enzymes and hence in determining active site structure through the physical techniques used in this work.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://dx.doi.org/10.1021/ic960988rDOIArticle
ORCID:
AuthorORCID
Chan, Sunney I.0000-0002-5348-2723
Additional Information:© 1997 American Chemical Society. Received August 14, 1996. Funding for this work was provided by NIH Grant GM22432 from the National Institute of General Medical Sciences, U.S. Public Health Services. X.-y.L. acknowledges the support of this project by RGC-CERG and HKUST. B.E.S. is the recipient of a National Science Foundation Postdoctoral Fellowship. We thank Jeff Clites for experimental assistance.
Funders:
Funding AgencyGrant Number
NIHGM22432
Research Grants Council of Hong KongUNSPECIFIED
Hong Kong University of Science and TechnologyUNSPECIFIED
NSF Postdoctoral FellowshipUNSPECIFIED
Issue or Number:12
Record Number:CaltechAUTHORS:20180529-113543917
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180529-113543917
Official Citation:Electronic Paramagnetic Resonance and Magnetic Properties of Model Complexes for Binuclear Active Sites in Hydrolase Enzymes Brian E. Schultz, Bao-Hui Ye, Xiao-yuan Li, and Sunney I. Chan Inorganic Chemistry 1997 36 (12), 2617-2622 DOI: 10.1021/ic960988r
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86667
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:29 May 2018 19:48
Last Modified:03 Oct 2019 19:46

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