Solel Ephrath, Pappo Doron, Reany Ofer, Mejuch Tom, Gershoni-Poranne Renana, Botoshansky Mark, Stanger Amnon, Keinan Ehud
The Schulich Faculty of Chemistry, Technion - Israel Institute of Technology Technion City Haifa 3200001 Israel
Department of Chemistry, Ben-Gurion University of the Negev Beer-Sheva 84105 Israel.
Chem Sci. 2020 Oct 22;11(48):13015-13025. doi: 10.1039/d0sc04566g.
Flat corannulene has been considered so far only as a transition state of the bowl-to-bowl inversion process. This study was driven by the prediction that substituents with strong steric repulsion could destabilize the bowl-shaped conformation of this molecule to such an extent that the highly unstable planar geometry would become an isolable molecule. To examine the substituents' effect on the corannulene bowl depth, optimized structures for the highly-congested decakis(-butylsulfido)corannulene were calculated. The computations, performed with both the M06-2X/def2-TZVP and the B3LYP/def2-TZVP methods (the latter with and without Grimme's D3 dispersion correction), predict that this molecule can achieve two minimum structures: a flat carbon framework and a bowl-shaped structure, which are very close in energy. This rather unusual compound was easily synthesized from decachlorocorannulene under mild reaction conditions, and X-ray crystallographic studies gave similar results to the theoretical predictions. This compound crystallized in two different polymorphs, one exhibiting a completely flat corannulene core and the other having a bowl-shaped conformation.
迄今为止，扁平的碗烯仅被视为碗状翻转过程中的过渡态。本研究的起因是有预测称，具有强烈空间排斥作用的取代基会使该分子的碗状构象不稳定到如此程度，以至于高度不稳定的平面几何结构会成为一种可分离的分子。为了研究取代基对碗烯碗深的影响，计算了高度拥挤的十（-丁基硫基）碗烯的优化结构。使用M06-2X/def2-TZVP和B3LYP/def2-TZVP方法（后者有和没有Grimme的D3色散校正）进行的计算预测，该分子可以实现两种最低结构：扁平的碳骨架和碗状结构，它们的能量非常接近。这种相当不寻常的化合物在温和的反应条件下很容易由十氯碗烯合成，并且X射线晶体学研究给出了与理论预测相似的结果。该化合物以两种不同的多晶型结晶，一种呈现完全扁平的碗烯核心，另一种具有碗状构象。
