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Electronic structure of high-spin iron(IV) complexes
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UNSPECIFIED (2004) Electronic structure of high-spin iron(IV) complexes. EUROPEAN JOURNAL OF INORGANIC CHEMISTRY (23). pp. 4555-4560. doi:10.1002/ejic.200400362 ISSN 1434-1948.
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Official URL: http://dx.doi.org/10.1002/ejic.200400362
Abstract
High-spin (S = 2) iron(IV) species are rare but increasingly recognized as reactive intermediates in the catalytic cycles of several nonheme iron enzymes. A question of some interest, therefore, concerns how much higher in energy the low-spin (S = 1) state is for these species. With the use of density functional theory (DFT) and high-level ab initio calculations [CASPT2 and CCSD(T)], we have attempted to answer this question for the so-called Collins complex, a square-pyramidal Fe-IV complex with a tetraamido-N equatorial ligand set, a chloride axial ligand, and an S = 2 ground state. The calculations suggest that relative to the ground state, the low-spin state is higher in energy by at least 0.3 eV and possibly as much as 0.7 eV. Using DFT calculations, a broad quantum chemical survey of high-spin (FeO)-O-IV intermediates was also undertaken. A key finding is that the Fe-O distance and O spin population are quite similar across all mononuclear (FeO)-O-IV species studied, regardless of the heme versus non-heme environment and of the S = 1 versus 2 spin state, reflecting the essential similarity of the Fe(d(pi))-O(p(pi)) orbital interactions in all the species studied. However, the spin density profiles of high-spin (FeO)-O-IV species, currently believed to be known only as a nonheme iron enzyme (TauD) intermediate, are predicted to be very different from that of Collins' high-spin Fe-IV complex. Our calculations further suggest that with the help of sterically hindered ligands such as 6-me(3)-tpa, it might be possible to generate synthetic high-spin (FeO)-O-IV models of the unique TauD intermediate. Finally, our calculations confirm the aptness of describing the [(6-me(3)-tpa)Fe-III(mu-O)(2)Fe-IV(6-me(3)-tpa)](3+) cation as a flexible diamond core and indicate the presence of a fairly discrete high-spin (FeO)-O-IV unit within the dinuclear core. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
Item Type: | Journal Article | ||||
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Subjects: | Q Science > QD Chemistry | ||||
Journal or Publication Title: | EUROPEAN JOURNAL OF INORGANIC CHEMISTRY | ||||
Publisher: | WILEY-V C H VERLAG GMBH | ||||
ISSN: | 1434-1948 | ||||
Official Date: | 3 December 2004 | ||||
Dates: |
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Number: | 23 | ||||
Number of Pages: | 6 | ||||
Page Range: | pp. 4555-4560 | ||||
DOI: | 10.1002/ejic.200400362 | ||||
Publication Status: | Published |
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