State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
Nat Chem. 2013 Aug;5(8):698-703. doi: 10.1038/nchem.1690. Epub 2013 Jun 23.
Anti-aromatic compounds, as well as small cyclic alkynes or carbynes, are particularly challenging synthetic goals. The combination of their destabilizing features hinders attempts to prepare molecules such as pentalyne, an 8π-electron anti-aromatic bicycle with extremely high ring strain. Here we describe the facile synthesis of osmapentalyne derivatives that are thermally viable, despite containing the smallest angles observed so far at a carbyne carbon. The compounds are characterized using X-ray crystallography, and their computed energies and magnetic properties reveal aromatic character. Hence, the incorporation of the osmium centre not only reduces the ring strain of the parent pentalyne, but also converts its Hückel anti-aromaticity into Craig-type Möbius aromaticity in the metallapentalynes. The concept of aromaticity is thus extended to five-membered rings containing a metal-carbon triple bond. Moreover, these metal-aromatic compounds exhibit unusual optical effects such as near-infrared photoluminescence with particularly large Stokes shifts, long lifetimes and aggregation enhancement.
反芳香化合物以及小环炔烃或卡宾，是极具挑战性的合成目标。它们的不稳定性特征的结合阻碍了制备五炔，一种具有极高环张力的 8π 电子反芳香自行车分子的尝试。在这里，我们描述了易于合成的奥斯马五炔衍生物，尽管它们含有迄今为止在卡宾碳上观察到的最小角度，但在热稳定性上是可行的。通过 X 射线晶体学对化合物进行了表征，其计算出的能量和磁性特性显示出芳香性。因此，锇中心的引入不仅降低了母体五炔的环张力，而且将其 Hückel 反芳香性转化为金属五炔中的 Craig 型莫比乌斯芳香性。因此，芳香性的概念被扩展到含有金属-碳三键的五元环中。此外，这些金属芳香化合物表现出不寻常的光学效应，如具有特别大的斯托克斯位移、长寿命和聚集增强的近红外光致发光。
