Achieving Adaptive Aromaticity in Cyclo[10]carbon by Screening Cyclo[n]carbon (n=8-24)
Achieving Adaptive Aromaticity in Cyclo[10]carbon by Screening Cyclo[n]carbon (n=8-24)
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DOI：
10.1002/asia.202000528
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发表时间：
2020-06-16
影响因子：
4.1
通讯作者：
Zhu, Jun
中科院分区：
文献类型：
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作者：
Dai, Chenshu;Chen, Dandan;Zhu, Jun
发现具有适应性芳香性的物种（在最低单线态和三线态下都具有芳香性）特别具有挑战性，因为根据休克尔和贝尔德的规则，环状物种通常仅在基态或仅在激发态下具有芳香性。受最近实现的环[18]碳的启发，我们通过筛选环[n]碳（n=8-24）证明了环[10]碳具有自适应芳香性，这得到了核无关化学位移（NICS）、电流诱导密度各向异性（ACID）、电子定位函数的pi贡献（ELF pi）和电子密度的支持。 离域键（EDDB）分析。进一步的研究表明，环[10]碳的最低三重态是由面内 pi pi* 激发形成的。因此，面外π分子轨道对芳香性的主要贡献在最低单线态下不会显着变化。我们的研究结果强调了面外 pi 轨道在维持最低单重态和三重态的芳香性以及芳香性对环[n]碳中碳原子数的依赖性方面的关键作用。
Discovery of species with adaptive aromaticity (being aromatic in both the lowest singlet and triplet states) is particularly challenging as cyclic species are generally aromatic either in the ground state or in the excited state only, according to Huckel's and Baird's rules. Inspired by the recent realization of cyclo[18]carbon, here we demonstrate that cyclo[10]carbon possesses adaptive aromaticity by screening cyclo[n]carbon (n=8-24), which is supported by nucleus-independent chemical shift (NICS), anisotropy of the current-induced density (ACID), pi contribution of electron localization function (ELF pi) and electron density of delocalized bonds (EDDB) analyses. Further study reveals that the lowest triplet state of cyclo[10]carbon is formed by in-plane pi pi* excitation. Thus, the major contribution to the aromaticity from out-of-plane pi molecular orbitals does not change significantly in the lowest singlet state. Our findings highlight a crucial role of out-of-plane pi orbitals in maintaining aromaticity for both the lowest singlet and triplet states as well as the aromaticity dependence on the number of the carbon in cyclo[n]carbon.