Wu Jiashun, Rouf Alvi Muhammad, Huang Yuanyuan, Zhuang Danling, Zhu Jun
State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, China.
Phys Chem Chem Phys. 2020 Feb 26;22(8):4668-4676. doi: 10.1039/c9cp06506g.
Pentafulvenes are dipolar hydrocarbons since they shift their π-electrons to achieve Hückel aromaticity and thus the electron donating groups at the exocyclic position can enhance their aromaticity. Silapentafulvenes are analogues of pentafulvene formed by the replacement of the carbon atoms at the exocyclic C[double bond, length as m-dash]C double bond with a silicon atom in pentafulvene. It remains unclear how the aromaticity of 5-silapentafulvenes and 6-silapentafulvenes can be changed due to the polarization of the C[double bond, length as m-dash]Si double bond. Here we perform density functional theory calculations and reveal the increased aromatic character in 6-silapentafulvenes and the reduced aromaticity of 5-silapentafulvenes in the ground state. In addition, the origin of the relative thermodynamic stability of the silapentafulvene isomers can be attributed to the bond dissociation energy (BDE) of the exocyclic bond. More interestingly, some triplet ground state 5-silapentafulvene species are predicted by introducing amino groups on the ring, which is supported by the coupled cluster calculations. Our findings could be useful for experimentalists to realize silaaromatics.
戊搭烯是偶极烃，因为它们会移动其π电子以实现休克尔芳香性，因此环外位置的给电子基团可以增强其芳香性。硅戊搭烯是戊搭烯的类似物，它是通过将戊搭烯中环外C═C双键处的碳原子用硅原子取代而形成的。由于C═Si双键的极化，5-硅戊搭烯和6-硅戊搭烯的芳香性如何变化仍不清楚。在此，我们进行了密度泛函理论计算，并揭示了基态下6-硅戊搭烯的芳香性增加以及5-硅戊搭烯的芳香性降低。此外，硅戊搭烯异构体相对热力学稳定性的起源可归因于环外键的键解离能（BDE）。更有趣的是，通过在环上引入氨基预测了一些三线态基态5-硅戊搭烯物种，这得到了耦合簇计算的支持。我们的发现可能有助于实验人员实现硅芳香族化合物。
