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首页> 外文期刊>Chemistry: A European journal >Tuning the polarization along linear polyaromatic strands for rationally inducing mesomorphism in lanthanide nitrate complexes
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Tuning the polarization along linear polyaromatic strands for rationally inducing mesomorphism in lanthanide nitrate complexes

机译：调整线性多芳香族链的极化，以合理地诱导硝酸镧系元素络合物的同构

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摘要

The opposite orientation of the ester spacers in the rodlike ligands L4(C12) (benzimidazole-OOC-phenyl) and L5C(12) (benzimidazole-COO-phenyl) drastically changes the electronic structure of the aromatic systems, without affecting their meridional tricoordination to trivalent lanthanides, Ln(III), and their thermotropic liquid crystalline (i.e., mesomorphic) behaviors. However, the rich mesomorphism exhibited by the complexes [Ln(L4(C12))-(NO3)(3)] (Ln = La-Lu) vanishes in [Ln-(L5(C12))(NO3)(3)], despite superimposable molecular structures and comparable photophysical properties. Density functional theory (DFT) and time-dependant DFT calculations performed in the gas phase show that the inversion of the ester spacers has considerable effects on the electronic structure and polarization of the aromatic groups along the strands, which control residual intermolecular interactions responsible for the formation of thermotropic liquid-crystalline phases. As a rule of thumb, an alternation of electron-poor and electron-rich aromatic rings favors intermolecular interactions between the rigid cores and consequently mesomorphism, a situation encountered for L4(C12), L5(C12), [Ln(L4(C12))(NO3)(3)], but not for [Ln(L5(C12))(NO3)(3)]. The intercalation of an additional electron-rich diphenol ring on going from [Ln(L5(C12))-(NO3)(3)] to [Ln(L6(C12))(NO3)(3)] restores mesomorphism despite an unfavorable orientation of the ester spacers, in agreement with our simple predictive model.
机译：棒状配体L4（C12）（苯并咪唑-OOC-苯基）和L5C（12）（苯并咪唑-COO-苯基）中酯间隔基的相反取向在不影响其经向三配位的情况下极大地改变了芳族系统的电子结构三价镧系元素Ln（III）及其热致液晶（即介晶）行为。但是，[Ln（L4（C12））-（NO3）（3）]（Ln = La-Lu）配合物表现出的丰富的同质性在[Ln-（L5（C12））（NO3）（3）]中消失。 ，尽管分子结构重叠且光物理性质相当。在气相中进行的密度泛函理论（DFT）和随时间变化的DFT计算表明，酯间隔基的倒置对沿链的芳族基团的电子结构和极化有很大影响，从而控制了残余的分子间相互作用。热致液晶相的形成。根据经验，贫电子和富电子芳环的交替有利于刚性核之间的分子间相互作用，因此有利于同构，这是L4（C12），L5（C12），[Ln（L4（C12） ）（NO3）（3）]，但不适用于[Ln（L5（C12））（NO3）（3）]。从[Ln（L5（C12））-（NO3）（3）]到[Ln（L6（C12））（NO3）（3）]插入额外的富电子双酚环可恢复同构酯间隔基的方向，与我们的简单预测模型一致。

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