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Spectroscopic and Theoretical Investigation of High-Spin Square-Planar and Trigonal Fe(II) Complexes Supported by Fluorinated Alkoxides

The electronic structures and spectroscopic behavior of three high-spin FeII complexes of fluorinated alkoxides were studied: square-planar {K­(DME)2}2[Fe­(pinF)2] (S) and quasi square-planar {K­(C222)}2[Fe­(pinF)2] (S′) and trigonal-planar {K­(18C6)}­[Fe­(OC4F9)3] (T) where pinF = perfluoropinacola...

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Bibliographic Details
Published in:Inorganic chemistry 2024-02, Vol.63 (5), p.2370-2387
Main Authors: Toubiana, Léa A., Valaydon-Pillay, Adam, Elinburg, Jessica K., Bacon, Jeffrey W., Ozarowski, Andrew, Doerrer, Linda H., Stoian, Sebastian A.
Format: Article
Language:English
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Summary:The electronic structures and spectroscopic behavior of three high-spin FeII complexes of fluorinated alkoxides were studied: square-planar {K­(DME)2}2[Fe­(pinF)2] (S) and quasi square-planar {K­(C222)}2[Fe­(pinF)2] (S′) and trigonal-planar {K­(18C6)}­[Fe­(OC4F9)3] (T) where pinF = perfluoropinacolate and OC4F9 = tris-perfluoro-t-butoxide. The zero-field splitting (ZFS) and hyperfine structure parameters of the S = 2 ground states were determined using field-dependent 57Fe Mössbauer and high-field and -frequency electron paramagnetic resonance (HFEPR) spectroscopies. The spin Hamiltonian parameters were analyzed with crystal field theory and corroborated by density functional theory (DFT) and ab initio complete active space self-consistent field (CASSCF) calculations. Whereas the ZFS tensor of S has a small rhombicity, E/D = 0.082, and a positive D = 15.17 cm–1, T exhibits a negative D = −9.16 cm–1 and a large rhombicity, E/D = 0.246. Computational investigation of the structural factors suggests that the ground-state electronic configuration and geometry of T’s Fe site are determined by the interaction of [Fe­(OC4F9)3]− with {K­(18C6)}+. In contrast, two distinct countercations of S/S′ have a negligible influence on their [Fe­(pinF)2]2– moieties. Instead, the distortions in S′ are likely induced by the chelate ring conformation change from δλ, observed for S, to the δδ conformation, determined for S′.
ISSN:0020-1669
1520-510X
1520-510X
DOI:10.1021/acs.inorgchem.3c03236