Tuning the (Chir)Optical Properties and Squeezing out the Inherent Chirality in Polyphenylene‐Locked Helical Carbon Nanorings

• Published in: Chemistry : a European journal Vol. 28; no. 13; pp. e202103828 - n/a
• Main Authors: Wang, Jinyi, Shi, Hong, Wang, Shengda, Zhang, Xinyu, Fang, Pengwei, Zhou, Yu, Zhuang, Gui‐Lin, Shao, Xiang, Du, Pingwu
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.03.2022
• Subjects: Chemistry; Chirality; circularly polarized luminescence; conjugation; Enantiomers; Helicity; High-performance liquid chromatography; inherent chirality; Isomerization; Liquid chromatography; macrocycles; Optical activity; Optical properties; photophysics; Physical properties; Polycyclic aromatic hydrocarbons; Racemization; Tuning; inherent chirality; photophysics; circularly polarized luminescence; macrocycles; conjugation
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202103828

Distorting linear polyaromatic hydrocarbons (PAHs) out of planarity affects their physical properties and breaks their symmetry to induce inherent chirality. However, the chirality cannot be achieved in large distorted PAHs‐based macrocycles due to a low racemization barrier for isomerization. Herein, we report the precise synthesis and tuning size‐dependent (chir)optical properties of a new class of chiral PAHs‐containing conjugated macrocycles (cyclo[n]paraphenylene‐2,6‐anthrylene, [n]CPPAn2,6; n=6–8). Their inherent chiralities were squeezed out in small anthrylene‐based macrocycles. Efficient resolutions for chiral enantiomers with (P)/(M)‐helicity of small [6‐7]CPPAns were achieved by HPLC. Interestingly, these macrocycles showed enriched size‐dependent physical, chiral, and (chir)optical properties. Theoretical calculations indicate that these macrocycles have high strain energy (Estrain=60.8 to 73.4 kcal/mol) and very small Egap (∼3.0 eV). Notably, these enantiomers showed strong chiroptical properties and dissymmetry factors (|gabs| and |glum|∼0.01 for an enantiomer of [6]CPPAn2,6), which can give them potential applications in optically active materials. This study reports the precise synthesis and tuning size‐dependent (chir)optical properties of chiral distorted acenes ([n]CPPAn2,6; n=6–8). Efficient resolutions for chiral enantiomers with (P)/(M)‐helicity were achieved only when the size is small. These enantiomers showed strong chiroptical properties and dissymmetry factors (|gabs| and |glum|∼0.01 for an enantiomer of [6]CPPAn2,6).