Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
Université Paris-Saclay, CEA, INRAE, Département Médicaments et Technologies pour la Santé (DMTS), SCBM, F-91191, Gif-sur-Yvette, France.
J Am Chem Soc. 2021 Mar 31;143(12):4661-4667. doi: 10.1021/jacs.0c13197. Epub 2021 Mar 18.
π-Extended helicenes constitute an important class of polycyclic aromatic hydrocarbons with intrinsic chirality. Herein, we report the syntheses of π-extended [7]helicene and π-extended [9]helicene through regioselective cyclodehydrogenation in high yields, where a "prefusion" strategy plays a key role in preventing undesirable aryl rearrangements. The unique helical structures are unambiguously confirmed by X-ray crystal structure analysis. Compared to the parent pristine [7]helicene and [9]helicene, these novel π-extended helicenes display significantly improved photophysical properties, with a quantum yield of 0.41 for . After optical resolution by chiral high-performance liquid chromatography, the chiroptical properties of enantiomers -/ and -/ are investigated, revealing that the small variation in helical length from [7] to [9] can cause an approximately 10-fold increase in the dissymmetry factors. The circularly polarized luminescence brightness of reaches 12.6 M cm as one of the highest among carbohelicenes.
π-扩展的螺旋芳烃是具有内在手性的一类重要多环芳烃。在此，我们通过区域选择性环脱氢反应以高产率得到了 π-扩展的[7]螺旋芳烃 和 π-扩展的[9]螺旋芳烃，其中“预融合”策略在防止不期望的芳基重排方面起着关键作用。独特的螺旋结构通过 X 射线晶体结构分析得到了明确的证实。与母体的原始[7]螺旋芳烃和[9]螺旋芳烃相比，这些新型的π-扩展螺旋芳烃显示出显著改善的光物理性质，对于 ，量子产率为 0.41。通过手性高效液相色谱进行光学拆分后，研究了对映异构体 -/和 -/的手性光学性质，结果表明，螺旋长度从[7]到[9]的微小变化会导致不对称因子增加约 10 倍。作为碳螺旋芳烃中最高的之一，的圆偏振发光亮度达到 12.6 M cm。
