@article{oai:oist.repo.nii.ac.jp:00002084,
 author = {Qiu, Zijie and Ju, Cheng-Wei and Frédéric, Lucas and Hu, Yunbin and Schollmeyer, Dieter and Pieters, Grégory and Müllen, Klaus and Narita, Akimitsu},
 issue = {12},
 journal = {Journal of the American Chemical Society},
 month = {Mar},
 note = {π-Extended helicenes constitute an important class of polycyclic aromatic hydrocarbons with intrinsic chirality. Herein, we report the syntheses of π-extended [7]helicene 4 and π-extended [9]helicene 6 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 6. After optical resolution by chiral high-performance liquid chromatography, the chiroptical properties of enantiomers 4-P/M and 6-P/M 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 6 reaches 12.6 M⁻¹ cm⁻¹ as one of the highest among carbohelicenes.},
 pages = {4661--4667},
 title = {Amplification of Dissymmetry Factors in π-Extended [7]- and [9]Helicenes},
 volume = {143},
 year = {2021}
}