School of Chemistry, Monash University, Clayton, Victoria 3800, Australia.
Inorg Chem. 2011 Apr 4;50(7):3052-64. doi: 10.1021/ic102588h. Epub 2011 Mar 8.
The reaction of [Fe(II)(BF(4))(2)]·6H(2)O with the nitroxide radical, 4,4-dimethyl-2,2-di(2-pyridyl) oxazolidine-N-oxide (L(•)), produces the mononuclear transition metal complex Fe(II)(L(•))(2)(2) (1) which has been investigated using temperature dependent susceptibility, Mössbauer spectroscopy, electrochemistry, density functional theory (DFT) calculations, and X-ray structure analysis. Single crystal X-ray diffraction analysis and Mössbauer measurements reveal an octahedral low spin Fe(2+) environment where the pyridyl donors from L(•) coordinate equatorially while the oxygen containing the radical from L(•) coordinates axially forming a linear O(•)··Fe(II)··O(•) arrangement. Magnetic susceptibility measurements show a strong radical-radical intramolecular antiferromagnetic interaction mediated by the diamagnetic Fe(2+) center. This is supported by DFT calculations which show a mutual spatial overlap of 0.24 and a spin density population analysis which highlights the antiparallel spin alignment between the two ligands. Similarly the monocationic complex Fe(III)(L(-))(2)·0.5H(2)O (2) has been fully characterized with Fe-ligand and N-O bond length changes in the X-ray structure analysis, magnetic measurements revealing a Curie-like S = 1/2 ground state, electron paramagnetic resonance (EPR) spectra, DFT calculations, and electrochemistry measurements all consistent with assignment of Fe in the (III) state and both ligands in the L(-) form. 2 is formed by a rare, reductively induced oxidation of the Fe center, and all physical data are self-consistent. The electrochemical studies were undertaken for both 1 and 2, thus allowing common Fe-ligand redox intermediates to be identified and the results interpreted in terms of square reaction schemes.
[Fe(II)(BF(4))(2)]·6H(2)O 与氮氧自由基 4,4-二甲基-2,2-二(2-吡啶基)恶唑啉-N-氧化物 (L(•)) 反应，生成单核过渡金属配合物 Fe(II)(L(•))(2)(2) (1)，该配合物已通过温度依赖磁化率、穆斯堡尔光谱、电化学、密度泛函理论 (DFT) 计算和 X 射线结构分析进行了研究。单晶 X 射线衍射分析和穆斯堡尔测量揭示了低自旋 Fe(2+)的八面体环境，其中 L(•)的吡啶供体赤道配位，而来自 L(•)的含氧基轴向配位，形成线性 O(•)··Fe(II)··O(•)排列。磁化率测量表明，在顺磁性 Fe(2+)中心的介导下，自由基-自由基之间存在强烈的分子内反铁磁相互作用。这一结果得到了 DFT 计算的支持，计算表明两个配体之间存在 0.24 的相互空间重叠和自旋密度分布分析，突出了两个配体之间的反平行自旋排列。同样，Fe(III)(L(-))(2)·0.5H(2)O (2) 也已通过 X 射线结构分析、磁性测量、电子顺磁共振 (EPR) 光谱、DFT 计算和电化学测量得到了充分的表征，这些测量结果表明 Fe 处于 (III) 态，两个配体均处于 L(-)态，Fe-配体和 N-O 键长的变化与该配合物的特征一致。2 是通过 Fe 中心的罕见还原诱导氧化形成的，所有物理数据都是一致的。对 1 和 2 都进行了电化学研究，从而可以识别常见的 Fe-配体氧化还原中间体，并根据正方形反应方案解释结果。
