Pentahelicene (PH) exhibits the largest absorption (g_abs) and luminescence (g_lum) dissymmetry factors among the helicene family but is configurationally and (photo)chemically labile, encumbering its application to chiroptical materials. To bypass the pitfalls, three PH units are merged in a single molecule to build D₃-symmetric triple pentahelicene, hexabenzotriphenylene (HBT), which attains indeed the configurational and (photo)chemical robustness through equilibrium with a C₂-symmetric conformer that interrupts the racemization and photocyclization. UV–vis, circular dichroism (CD), and circularly polarized luminescence (CPL) spectral examinations reveal the significantly larger g_abs and g_lum values for HBT than for any of configurationally robust single [n]helicene (n ≥ 6) and C₂-symmetric triple pentahelicene, trinaphthotriphenylene (TNT). Theoretical calculations precisely reproduce the main features of the experimental CD and CPL spectra of PH, HBT, and TNT, and the relevant electric and magnetic transition moments and their mutual angles well rationalize the relative CD and CPL intensities of all the single and triple pentahelicenes.

中文翻译：

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构型健壮的D ₃对称三元十五碳烯的圆二色性和圆偏振发光的组合实验和理论研究

戊烯化合物（PH）在螺旋烯家族中表现出最大的吸收（g _abs）和发光（g _lum）不对称因子，但在构型和（光）化学上不稳定，这妨碍了其在手性材料中的应用。为了避开陷阱，将三个PH单元合并到一个分子中，以构建D ₃对称的三并五戊烯六苯并三苯并菲（HBT），通过与C ₂平衡，确实获得了构型和（光）化学稳健性。对称的构象异构体，可中断外消旋和光环化。紫外-可见，圆二色性（CD），和圆偏振发光（CPL）谱检查揭示显著较大克_ABS和克_LUM为值HBT比任何构型上坚固的单[的Ñ ]螺烯（Ñ ≥6）和c ^ ₂对称的三戊基三苯并三萘并三苯并菲（TNT）。理论计算精确再现了PH，HBT和TNT的实验CD和CPL光谱的主要特征，相关的电磁跃迁矩和它们的相互夹角很好地合理化了所有单和三方戊烯的相对CD和CPL强度。