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677299.0 [No comment] 18.06.2015 12:26 Released

ID: 677299.0, MPI für bioanorganische Chemie / MPI für bioanorganische Chemie
Sensitivity of X-ray Core Spectroscopy to Changes in Metal Ligation: A Systematic Study of Low-Coordinate, High-Spin Ferrous Complexes
Authors:Chandrasekaran, P.; Chiang, Karen P.; Nordlund, Dennis; Bergmann, Uwe; Holland, Patrick L.; DeBeer, Serena
Date of Publication (YYYY-MM-DD):2013
Title of Journal:Inorganic Chemistry
Journal Abbrev.:Inorg. Chem.
Start Page:6286
End Page:6298
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:In order to assess the sensitivity and complementarity of X-ray absorption and emission spectroscopies for determining changes in the metal ligation sphere, a systematic experimental and theoretical study of iron model complexes has been carried out A series of high spin ferrous complexes, in which the ligation sphere has been varied from a three coordinate complex, [(LFe)-Fe-tBu(SPh)] (1) (where L-tBu = bulky beta-diketiminate ligand; SPh = phenyl thiolate) to four coordinate complexes [(LFe)-Fe-tBu(SPh)(X)] (where X = (CNBu)-Bu-t (2); 1-methylimidazole (3); or N,N-dimethylformamide (DMF) (4)), has been investigated using a combination of Fe K-edge X-ray absorption (XAS) and K beta X-ray emission (XES) spectroscopies. The Fe K XAS pre-edge and edge of all four complexes are consistent with a high spin ferrous assignment, with the largest differences in the pre-edge intensities attributed to changes in covalency of the fourth coordination site The X-ray emission spectra show pronounced changes in the valence to core region (V2C) as the identity of the coordinated ligand is varied. The experimental results have been correlated to density functional theory (DFT) calculations, to understand key molecular orbital contributions to the observed absorption and emission features The calculations also have been extended to a series of hypothetical high spin iron complexes to understand the sensitivity of XAS and XES techniques to different ligand protonation states ([(LFeII)-Fe-tBu(SPh)(NHn)](3-n) (n = 3, 2, 1, 0)), metal oxidation states [(LFe)-Fe-tBu(SPh)(N)](n-) (n = 3, 2, 1), and changes in the ligand identity [(LFeIV)-Fe-tBu(SPh)(X)](n-) (X = C4-, N3-, O2-; n = 2, 1, 0). This study demonstrates that XAS pre-edge data have greater sensitivity to changes in oxidation state, while valence to core (V2C) XES data provide a more sensitive probe of ligand identity and protonation state. The combination of multiple X-ray spectroscopic methods with DFT results thus has the potential to provide for detailed characterization of complex inorganic systems in both chemical and biological catalysis.
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für bioanorganische Chemie
External Affiliations:Chandrasekaran, P.; DeBeer,S.;Cornell Univ, Dept Chem & Chem Biol, Ithaca, NY 14853 USA.
Chiang, K.P.; Holland, P.L.; Univ Rochester, Dept Chem, Rochester, NY 14627 USA.
Nordlund, D.; SLAC Natl. Accelerator Lab, Stanford Synchrotron Radiat Lightsource, Menlo Pk, CA 94025 USA. Bergmann, U.; SLAC Natl Accelerator Lab, Linac Coherent Light Source, Menlo Pk, CA 94025 USA.
Chandrasekaran, P..; Lamar Univ, Dept Chem & Biochem, Beaumont, TX 77710 USA.
Identifiers:ISI:000320015700009 [ID No:1]
ISSN:0020-1669 [ID No:2]