Pulsed EPR Investigations of Systems Modeling Molybdenum Enzymes: Hyperfine and Quadrupole Parameters of Oxo-17O in [Mo17O(SPh)4]-

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• 作者：Andrei V. Astashkin ; Frank Neese ; Arnold M. Raitsimring ; J. Jon A. Cooney ; Eric Bultman ; and John H. Enemark
• 刊名：Journal of the American Chemical Society
• 出版年：2005
• 出版时间：November 30, 2005
• 年：2005
• 卷：127
• 期：47
• 页码：16713 - 16722
• 全文大小：210K
• 年卷期：v.127,no.47(November 30, 2005)
• ISSN：1520-5126

文摘

K_a band ESEEM spectroscopy was used to determine the hyperfine (hfi) and nuclear quadrupole(nqi) interaction parameters for the oxo-¹⁷O ligand in [Mo¹⁷O(SPh)₄]^-, a spectroscopic model of the oxo-Mo(V) centers of enzymes. The isotropic hfi constant of 6.5 MHz found for the oxo-¹⁷O is much smallerthan the values of ~20-40 MHz typical for the ¹⁷O nucleus of an equatorial OH₍₂₎ ligand in molybdenumenzymes. The ¹⁷O nqi parameter (e²qQ/h = 1.45 MHz, 0) is the first to be obtained for an oxo groupin a metal complex. The parameters of the oxo-¹⁷O ligand, as well as other magnetic resonance parametersof [Mo¹⁷O(SPh)₄]^- predicted by quasi-relativistic DFT calculations, were in good agreement with thoseobtained in experiment. From the electronic structure of the complex revealed by DFT, it follows that theSOMO is almost entirely molybdenum d_xy and sulfur p, while the spin density on the oxo-¹⁷O is negative,determined by spin polarization mechanisms. The results of this work will enable direct experimentalidentification of the oxo ligand in a variety of chemical and biological systems.