Qiu Rulin, 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.
Dalton Trans. 2021 Nov 23;50(45):16842-16848. doi: 10.1039/d1dt03244e.
According to Hückel's and Baird's rules, cyclic species are generally aromatic only either in the lowest singlet state (S) or in the lowest-lying triplet ππ* excited state (T). Thus, species with aromaticity both in S and T states (termed as adaptive aromaticity) are particularly rare. Herein, we carry out density functional theory (DFT) calculations to examine the aromaticity of 16e metallapentalenes containing heteroatoms (N, O). Interestingly, metallazapentalenes show adaptive aromaticity whereas metalloxapentalenes display nonaromaticity in the S and T states, which is supported by structural, magnetic, and electronic indices. In addition, a series of metallazapentalenes containing strong σ- or π-donor ligands are predicted to achieve adaptive aromaticity. Our findings expand the family of adaptive aromatics significantly, inviting experimental chemists to realize more hetero-metallapentalenes with adaptive aromaticity.
根据休克尔规则和贝尔德规则，环状物种通常仅在最低单重态（S）或最低三重态ππ*激发态（T）中具有芳香性。因此，在S态和T态均具有芳香性的物种（称为适应性芳香性）极为罕见。在此，我们进行密度泛函理论（DFT）计算，以研究含杂原子（N、O）的16e金属戊搭烯的芳香性。有趣的是，金属氮杂戊搭烯表现出适应性芳香性，而金属氧杂戊搭烯在S态和T态均表现为非芳香性，这得到了结构、磁性和电子指标的支持。此外，一系列含有强σ或π给体配体的金属氮杂戊搭烯预计可实现适应性芳香性。我们的发现显著扩展了适应性芳香族化合物的家族，促使实验化学家合成更多具有适应性芳香性的杂金属戊搭烯。
