AbstractChirality induction is an important topic in studies of nanographenes (NGs). We report chirality enhancements of NGs through postsynthetic chemical modifications of NGs with pyrene and m‐terphenyl groups. These substituents were installed into N‐(p‐bromophenylethyl)imides on the edges of the NGs with Pd‐catalyzed cross‐coupling reactions. Circular dichroism (CD) spectra demonstrated that these bulky substituents improved the induced CD signal of the NGs compared to those previously reported and suggested that they induced the opposite chirality. Density functional theory calculations indicated possible edge structures for the NGs and indicated that π/π and CH/π interactions among the neighboring substituents influenced the orientations of the imides. These imides distorted the edges, and the distorted edges eventually generated the chiral environments of the NGs. The interactions among the substituents are, therefore, likely to allow detection of the CD signals in the visible region and induction of the opposite chirality.
摘要手性诱导是纳米石墨烯(NGs)研究中的一个重要课题。我们报告了通过芘和间三联苯基团对 NGs 进行后合成化学修饰而增强 NGs 手性的情况。通过钯催化的交叉耦合反应,这些取代基被安装到了 NG 边缘的 N-(对溴苯基乙基)酰亚胺中。圆二色性(CD)光谱显示,与之前报道的相比,这些大块取代基改善了 NG 的诱导 CD 信号,并表明它们诱导了相反的手性。密度泛函理论计算显示了 NG 可能的边缘结构,并表明相邻取代基之间的 π/π 和 CH/π 相互作用影响了亚胺的取向。这些酰亚胺使边缘扭曲,扭曲的边缘最终产生了 NG 的手性环境。因此,取代基之间的相互作用很可能会在可见光区域检测到 CD 信号,并诱导出相反的手性。