Helicenes are one of attracted non-planar polycyclic aromatic hydrocarbons with their unique optical and electronic properties. In recent years, the chemistry of “multiple helicenes” with plural helicities in a single molecule has also grown rapidly as one of the research areas due to intriguing properties such as highly distorted structures, multidimensional intermolecular interactions, and the enhanced chiroptical properties. In this review, we summarize the synthesis and the molecular structures of multiple helicenes. Taking into consideration that the applied π-conjugated framework largely affects their synthesis, molecular structures, and physical properties, we categorize them according to the central π-conjugated core from smaller to larger aromatic rings and not the criterion of the original classification of multiple helicenes (multiplicity and the number of fused rings). Furthermore, we cover structural parameters and aromaticity of multiple helicenes, especially for the individual benzene rings, based on the definition of “twisting angle” and NICS values, respectively.

中文翻译：

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以合成方法和分子结构为特征的多重螺旋

Helicenes 是一种吸引的非平面多环芳烃，具有独特的光学和电子特性。近年来，“多重螺旋的化学”由于具有高度扭曲的结构、多维分子间相互作用和增强的手性光学特性等引人入胜的特性，在单个分子中具有多个螺旋的分子也迅速成为研究领域之一。在这篇综述中，我们总结了多重螺旋的合成和分子结构。考虑到所应用的π共轭骨架对它们的合成、分子结构和物理性质有很大影响，我们根据中心π共轭核从较小到较大的芳环对它们进行分类，而不是最初的多螺旋分类标准（多重性和稠环的数量）。此外，我们涵盖了多重螺旋的结构参数和芳香性，特别是对于单个苯环，扭转角”和 NICS 值。