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首页> 外文期刊>Crystal growth & design >Partially Covalent Two-Electron/Multicentric Bonding between Semiquinone Radicals
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Partially Covalent Two-Electron/Multicentric Bonding between Semiquinone Radicals

机译：在半醌基团之间部分共价两电子/多中心键合

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摘要

X-ray charge density was determined and analyzed for two polymorphs of the N-methylpyridinium salt of the tetrachlorosemiquinone radical anion and its analogous closed-shell relatives, tetrachloroquinone (chloranil) and tetrachlorohydroquinone. The study, which was combined with calculations of electron delocalization, electrostatic potentials, and aromaticity, presents details of electronic structure of the semiquinoid ring. This comparative study reveals that the negative charge is delocalized over the entire semiquinone radical and that the chlorine substituents play a crucial role in its stabilization through induction effect. In general, the semiquinoid ring has partially delocalized pi-electrons and is approximately halfway between a quinoid and an aromatic ring. In the orthorhombic polymorph with stacks of equidistant radicals electron density between the rings of almost 0.05 e angstrom(-3) and four (3,-1) saddle points between the contiguous rings were found. In the diamagnetic triclinic polymorph, comprising strongly bound radical dimers (with significant covalent character-"pancake bond"), maximum electron density between the rings exceeds 0.095 e angstrom(-3), and multiple (3,-1) critical points are found. However, only negligible electron density is observed between the dimers. Thus, in the radical anion stacks spin coupling, along with dispersive and polarization effects, defines interplanar distance and magnetic behavior, whereas intermolecular electrostatic potential determines the ring offset.
机译：确定X射线充电密度并分析四氯磷酮基氨醌基团的N-甲基吡啶鎓盐的两种多晶型物及其类似的封闭壳亲属，四氯醌（氯醌）和四氯氢醌。该研究与电子临床化，静电电位和芳香性相结合，呈现了半单细胞环的电子结构的细节。该比较研究表明，负电荷在整个半醌的基础上删除，并且氯取代基通过诱导效应在其稳定性中起着至关重要的作用。通常，半单细胞环具有部分中间分层的PI - 电子，并且在奎单和芳环之间大约是半部。在邻近0.05埃埃（-3）的环之间的正等距基团电子密度的正交多晶型物中，找到了连续环之间的四（3，-1）鞍座点。在抗磁性三级多晶型物中，含有强烈的自由基二聚体（具有显着的共价特征 - “煎饼键”），环之间的最大电子密度超过0.095埃埃（-3），并且发现多个（3，-1）关键点。然而，在二聚体之间仅观察到可忽略的电子密度。因此，在自由基阴离子堆叠中，旋转耦合，以及分散和偏振效应，限定了树木距离和磁性行为，而分子间静电电位决定了环偏移。

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  • 来源
    《Crystal growth & design》 |2019年第1期|共12页
  • 作者

    Molcanov Krgimir; Jelsch Christian; Landeros Bruno; Hernandez-Trujillo Jesus; Wenger Emmanuel; Stilinovic Vladimir; Kojic-Prodic Biserka; Escudero-Adan Eduardo C.;

  • 作者单位

    Rudjer Boskovic Inst Dept Phys Chem Bijenicka 54 HR-10000 Zagreb Croatia;

    CNRS Inst Jean Barriol UMR 7036 Cristallog Resonance Magnet &

    Modelisat BP 70239 F-54506 Vandoeuvre Les Nancy France;

    Univ Nacl Autonoma Mexico Fac Quim Dept Fis &

    Quim Teor Mexico City 04510 DF Mexico;

    Univ Nacl Autonoma Mexico Fac Quim Dept Fis &

    Quim Teor Mexico City 04510 DF Mexico;

    CNRS Inst Jean Barriol UMR 7036 Cristallog Resonance Magnet &

    Modelisat BP 70239 F-54506 Vandoeuvre Les Nancy France;

    Univ Zagreb Fac Sci Dept Chem Horvatovac 102a HR-10000 Zagreb Croatia;

    Rudjer Boskovic Inst Dept Phys Chem Bijenicka 54 HR-10000 Zagreb Croatia;

    Barcelona Inst Sci &

    Technol Inst Chem Res Catalonia Avgda Paisos Catalans 16 Tarragona 43007 Spain;

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  • 正文语种 eng
  • 中图分类 晶体学;
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