Nakakuki Yusuke, Hirose Takashi, Sotome Hikaru, Gao Min, Shimizu Daiki, Li Ruiji, Hasegawa Jun-Ya, Miyasaka Hiroshi, Matsuda Kenji
Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, 615-8510, Japan.
Institute for Chemical Research, Kyoto University, Uji, Kyoto, 611-0011, Japan.
Nat Commun. 2022 Apr 4;13(1):1475. doi: 10.1038/s41467-022-29108-8.
Helically twisted conductive nanocarbon materials are applicable to optoelectronic and electromagnetic molecular devices working on the nanometer scale. Herein, we report the synthesis of per-peri-perbenzo[5]- and [9]helicenes in addition to previously reported π-extended [7]helicene. The homogeneously π-extended helicenes can be regarded as helically fused oligo-phenanthrenes. The HOMO-LUMO gap decreased significantly from 2.14 to 1.15 eV with increasing helical length, suggesting the large effective conjugation length (ECL) of the π-extended helical framework. The large ECL of π-extended helicenes is attributed to the large orbital interactions between the phenanthrene subunits at the 9- and 10-positions, which form a polyene-like electronic structure. Based on the experimental results and DFT calculations, the ultrafast decay dynamics on the sub-picosecond timescale were attributed to the low-lying conical intersection.
螺旋扭曲的导电纳米碳材料适用于在纳米尺度上工作的光电子和电磁分子器件。在此，我们报告了除先前报道的π-扩展[7]螺旋烯之外的全-周-全苯并[5] - 和[9]螺旋烯的合成。均匀的π-扩展螺旋烯可被视为螺旋稠合的低聚菲。随着螺旋长度的增加，HOMO-LUMO能隙从2.14 eV显著降低至1.15 eV，这表明π-扩展螺旋骨架具有较大的有效共轭长度（ECL）。π-扩展螺旋烯的大ECL归因于9位和10位菲亚基之间的大轨道相互作用，其形成了类似多烯的电子结构。基于实验结果和DFT计算，亚皮秒时间尺度上的超快衰减动力学归因于低位锥形交叉。
