Conformation and Aromaticity Switching in a Curved Non-Alternant sp2 Carbon Scaffold.,Angewandte Chemie International Edition

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Conformation and Aromaticity Switching in a Curved Non-Alternant sp2 Carbon Scaffold.
Angewandte Chemie International Edition ( IF 16.1 ) Pub Date : 2020-08-20 , DOI: 10.1002/anie.202010077
Chongwei Zhu ₁ , Kazutaka Shoyama ₁ , Frank Würthner ₁

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A curved sp² carbon scaffold containing fused pentagon and heptagon units (1) was synthesized by Pd‐catalyzed [5+2] annulation from a 3,9‐diboraperylene precursor and shows two reversible oxidation processes at low redox potential, accompanied by a butterfly‐like motion. Stepwise oxidation produced radical cation 1^.+ and dication 1²⁺. In the crystal structure, 1 exhibits a chiral cisoid conformation and partial π‐overlap between the enantiomers. For the radical cation 1^.+, a less curved cisoid conformation is observed with a π‐dimer‐type arrangement. 1²⁺ adopts a more planar structure with transoid conformation and slip‐stacked π‐overlap with closest neighbors. We also observed an intermolecular mixed‐valence complex of 1⋅(1^.+)₃ that has a huge trigonal unit cell [(1)₇₂(SbF₆)₅₄⋅(hexane)₁₀₁] and hexagonal columnar stacks. In addition to the conformational change, the aromaticity of 1 changes from localized to delocalized, as demonstrated by AICD and NICS(1)_zz calculations.

中文翻译：

弯曲非交替 sp2 碳支架中的构象和芳香度转换。

含有稠合五边形和七边形单元的弯曲 sp ²碳支架（ 1 ）是通过 Pd 催化的 [5+2] 环化从 3,9-二硼苝前体合成的，并在低氧化还原电位下显示出两个可逆氧化过程，并伴有蝶形反应。 ‐类运动。逐步氧化产生自由基阳离子1 ^.+和阳离子1 ²⁺ 。在晶体结构中， 1呈现手性顺式构象，对映体之间存在部分π重叠。对于自由基阳离子1 ^.+ ，观察到弯曲较小的顺式构象，具有 π-二聚体型排列。 1 ²⁺采用更平面的结构，具有反式构象和与最近邻的滑堆积 π 重叠。我们还观察到了1 ⋅( 1 ^.+ ) ₃的分子间混合价复合物，其具有巨大的三角晶胞 [( 1 ) ₇₂ (SbF ₆ ) ₅₄ ⋅(己烷) ₁₀₁ ] 和六角柱状堆叠。除了构象变化之外， 1的芳香性从定域变为非定域，如 AICD 和 NICS(1) _zz计算所证明的。

更新日期：2020-08-20

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