FeIII Bipyrrolidine Phenoxide Complexes and Their Oxidized Analogues

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• 作者：Linus Chiang ; Didier Savard ; Yuichi Shimazaki ; Fabrice Thomas ; Tim Storr
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：June 2, 2014
• 年：2014
• 卷：53
• 期：11
• 页码：5810-5819
• 全文大小：448K
• 年卷期：v.53,no.11(June 2, 2014)
• ISSN：1520-510X

文摘

Fe^III complexes of the symmetric (2S,2鈥?i>S)-[N,N鈥?bis(1-(2-hydroxy-3,5-di-tert-butylphenylmethyl))]-2,2鈥?bipyrrolidine (H₂L¹) and dissymmetric (2S,2鈥?i>S)-[N,N鈥?(1-(2-hydroxy-3,5-di-tert-butylphenylmethyl))-2-(pyridylmethyl)]-2,2鈥?bipyrrolidine (HL²) ligands incorporating the bipyrrolidine backbone were prepared, and the electronic structure of the neutral and one-electron oxidized species was investigated. Cyclic voltammograms (CV) of FeL¹Cl and FeL²Cl₂ showed expected redox waves corresponding to the oxidation of phenoxide moieties to phenoxyl radicals, which was achieved by treating the complexes with 1 equiv of a suitable chemical oxidant. The clean conversion of the neutral complexes to their oxidized forms was monitored by UV鈥搗is-NIR spectroscopy, where an intense 蟺鈥撓€* transition characteristic of a phenoxyl radical emerged ([FeL¹Cl]^{+鈥?/sup>: 25鈥?00 cm鈥? (9000 M鈥? cm鈥?); [FeL2Cl₂]+鈥?/sup>: 24鈥?00 cm鈥? (8300 M鈥? cm鈥?). The resonance Raman (rR) spectra of [FeL1Cl]+鈥?/sup> and [FeL2Cl₂]+鈥?/sup> displayed the characteristic phenoxyl radical 谓_7a band at 1501 and 1504 cm鈥?, respectively, confirming ligand-based oxidation. Electron paramagnetic resonance (EPR) spectroscopy exhibited a typical high spin FeIII (S = 5/2) signal for the neutral complexes in perpendicular mode. Upon oxidation, a signal at g 鈮?9 was observed in parallel mode, suggesting the formation of a spin integer system arising from magnetic interactions between the high spin FeIII center and the phenoxyl radical. Density functional theory (DFT) calculations further supports this formulation, where weak antiferromagnetic coupling was predicted for both [FeL1Cl]+鈥?/sup> and [FeL2Cl₂]+鈥?/sup>.}