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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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Published in: | Inorganic chemistry 2024-02, Vol.63 (5), p.2370-2387 |
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Main Authors: | , , , , , , |
Format: | Article |
Language: | English |
Citations: | Items that this one cites |
Online Access: | Get full text |
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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′. |
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ISSN: | 0020-1669 1520-510X 1520-510X |
DOI: | 10.1021/acs.inorgchem.3c03236 |