Bian Jian-Hong, Jin Bo, Mu Yuewen, Hu Lingfei, Zhao Xue-Feng, Zhou Cheng-Yong, Yuan Caixia, Lu Gang, Wu Yan-Bo
Department of Materials and Chemical Engineering, Taiyuan University, Taiyuan 030032, P. R. China.
Key Laboratory of Materials for Energy Conversion and Storage of Shanxi Province and Institute of Molecular Science, Shanxi University, Taiyuan 030006, P. R. China.
Inorg Chem. 2023 Jul 24;62(29):11372-11380. doi: 10.1021/acs.inorgchem.3c00864. Epub 2023 Jul 11.
[]Cycloparaphenylenes ([]CPPs, denotes the number of phenyl groups) are difficult to synthesize because of the strain related to their bent phenyl rings. In particular, the strain in [3]CPP is high enough to destroy the π electron delocalization, leading to the spontaneous structural transition to an energetically more stable "bond-shift" (BS) isomer ([3]BS). In this contribution, we propose to achieve [3]CPP by enhancing the π electron delocalization through hosting a guest metal atom. Our computations revealed that Sc could stabilize [3]CPP by forming the [Sc©[3]CPP] complex through the favorable π-Sc donation-backdonation interactions. Thermodynamically, the binding energy between the Sc atom and [3]CPP was -205.7 kcal/mol, which could well compensate not only the energy difference of 44.2 kcal/mol between [3]CPP and [3]BS but also the extremely high strain energy of 170.3 kcal/mol in [3]CPP. Simultaneously, the [Sc©[3]CPP] complex is stable up to 1500 K in dynamic simulations, suggesting its high viability in the synthesis.
[ ] 环对亚苯基（[ ]CPPs， 表示苯基的数量）由于其弯曲苯环相关的张力而难以合成。特别是，[3]CPP中的张力高到足以破坏π电子离域，导致自发地向能量上更稳定的“键移”（BS）异构体（[3]BS）发生结构转变。在本论文中，我们提议通过引入客体金属原子来增强π电子离域，从而实现[3]CPP的合成。我们的计算表明，Sc可以通过有利的π-Sc给予-反馈相互作用形成[Sc©[3]CPP]配合物，从而使[3]CPP稳定。从热力学角度来看，Sc原子与[3]CPP之间的结合能为-205.7 kcal/mol，这不仅可以很好地补偿[3]CPP与[3]BS之间44.2 kcal/mol的能量差，还可以补偿[3]CPP中高达170.3 kcal/mol的极高应变能。同时，在动态模拟中，[Sc©[3]CPP]配合物在高达1500 K的温度下都是稳定的，这表明其在合成中具有很高的可行性。
