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首页> 外文期刊>Chemistry: A European journal >Experimental Spin Density in a Purely Organic Free Radical: Visualisation of the Ferromagnetic Exchange Pathway in p-(Methylthio) phenyl Nitronyl Nitroxide, Nit(SMe)Ph
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Experimental Spin Density in a Purely Organic Free Radical: Visualisation of the Ferromagnetic Exchange Pathway in p-(Methylthio) phenyl Nitronyl Nitroxide, Nit(SMe)Ph

机译：纯有机自由基中的实验自旋密度：对-（甲硫基）苯基亚硝酸硝基氮，Nit（SMe）Ph中铁磁交换途径的可视化

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摘要

The P2_1/a form of the 2-(4-methylthiophenyl)-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3-oxide [Nit(SMe)Ph] ferromagnet (T_c = 0.2 K) was investigated by conventional and polarised neutron diffraction. The data was analysed by both direct methods (3D maximum entropy) and indirect methods (wave function modelling). In both cases, we found that the major part of the spin density is located on the O-N-C-N-O fragment with a negative contribution on the bridging sp~2 carbon atom. In addition, the magnetic molecular orbital of the two oxygen atoms of the O-N-C-N-O fragment is rotated and hybridised. Delocalisation of the unpaired electron onto the methylthio fragment is significant; it suggests that this group is involved in the intermolecular exchange pathway. The experimental results were compared to those obtained by density functional theory (DFT) calculations on an isolated molecule as well as on a pair of molecules which have the same short intermolecular contact as those observed in the structure. The main conclusion is that DFt fails to predict, in terms of quantitative results, the transfer and the delocalisation of the spin density outside of the O-N-C-N-O fragment.
机译：用常规方法研究了2-（4-甲基硫代苯基）-4、4、5、5-四甲基咪唑啉-1-氧基-3-氧化物[Nit（SMe）Ph]铁磁体（T_c = 0.2 K）的P2_1 / a形式。和极化中子衍射。通过直接方法（3D最大熵）和间接方法（波函数建模）对数据进行了分析。在这两种情况下，我们发现自旋密度的主要部分位于O-N-C-N-O片段上，对桥接sp〜2碳原子有负贡献。另外，O-N-C-N-O片段的两个氧原子的磁性分子轨道旋转并杂交。未成对电子在甲硫基片段上的离域作用很大;这表明该群体参与了分子间的交换途径。将实验结果与通过密度泛函理论（DFT）计算获得的结果进行了比较，结果是对一个分离的分子以及一对与结构中观察到的分子间短接触相同的分子进行了比较。主要结论是，DFt无法根据定量结果预测自旋密度在O-N-C-N-O片段之外的转移和离域。

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