完全 π 共轭开笼分子中的芳香性,Journal of the American Chemical Society

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完全 π 共轭开笼分子中的芳香性
Journal of the American Chemical Society ( IF 15.0 ) Pub Date : 2022-12-07 , DOI: 10.1021/jacs.2c10859
Shaofei Wu _{1,

2} , Yong Ni ₁ , Yi Han ₁ , Shan Xin _{1,

2} , Xudong Hou ₁ , Jun Zhu ₁ , Zhengtao Li ₁ , Jishan Wu _{1,

2}

Affiliation

尽管已经深入研究了 2D π-共轭单环和多环分子中的芳香性，但由于合成方面的挑战，3D 完全 π-共轭分子笼中的芳香性在很大程度上仍未得到探索。在此，我们报告了通过铂介导组装四个硼酸频哪醇三取代 DTPA 衍生物分子，然后进行还原消除，轻松合成了一个包含四个二甲基亚甲基桥联三苯胺 (DTPA) 单元的 π 共轭分子笼 ( 1 )。1具有开笼结构，由反式和顺式构型的两个异构三聚体和一个跨四个 DTPA 单元的附加大环组成。因此，反式- ( 2)和顺式- ( 3 ) 大环三聚体也被合成用于比较。1-3可以很容易地氧化成它们各自的阳离子，其中电子在两个或三个维度上有效地离域。详细的实验测量和理论计算表明：（1）中性笼1在单个苯环中显示出局部芳香性；(2) 双阳离子1 ²⁺ ·2SbF ₆^–显示双环(反)芳香性，其中一个大环为芳香族(38π)，另一个大环为反芳香族(28π)；另一方面，模型化合物2和3的阳离子分别是全球抗芳香和非芳香的；(3) 四氢化1 ⁴⁺ ·4SbF ₆^–在其中一个大环 (36π) 中表现出主要的 2D Hückel 反芳香性。此外，1 ²⁺ · 2SbF ₆^–、1 ⁴⁺ ·4SbF ₆^–和2 ²⁺ ·2SbF ₆^–具有开壳层单线态基态，具有显着的双自由基特征，而3 ²⁺ ·2SbF ₆^–采用三线态释放应变的基态。

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Aromaticity in Fully π-Conjugated Open-Cage Molecules

Although aromaticity in 2D π-conjugated monocyclic and polycyclic molecules has been intensively studied, aromaticity in 3D fully π-conjugated molecular cages remains largely unexplored mainly due to the synthetic challenges. Herein, we report the facile synthesis of a π-conjugated molecular cage (1) containing four dimethylmethylene-bridged triphenylamine (DTPA) units via platinum-mediated assembly of four molecules of a pinacol borate trisubstituted DTPA derivative, followed by reductive elimination. 1 has an open-cage structure, consisting of two isomeric trimers in trans- and cis-configurations, and an additional macrocycle across four DTPA units. Accordingly, the trans- (2) and cis- (3) macrocyclic trimers were also synthesized for comparison. 1–3 can be facilely oxidized into their respective cations in which electrons are effectively delocalized at two or three dimensions. The detailed experimental measurements and theoretical calculations reveal that (1) the neutral cage 1 shows localized aromaticity in individual benzene rings; (2) the dication 1²⁺·2SbF₆^– displays bicyclic (anti)aromaticity with one macrocycle being aromatic (38π) and another macrocycle being antiaromatic (28π); on the other hand, the dications of the model compounds 2 and 3 are globally antiaromatic and nonaromatic, respectively; (3) the tetracation 1⁴⁺·4SbF₆^– exhibits dominant 2D Hückel antiaromaticity in one of the macrocycles (36π). In addition, 1²⁺·2SbF₆^–, 1⁴⁺·4SbF₆^–, and 2²⁺·2SbF₆^– possess open-shell singlet ground state with significant diradical character, while 3²⁺·2SbF₆^– adopts a triplet ground state to release strain.

更新日期：2022-12-07

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