Helicenes are polycyclic aromatic hydrocarbons (PAHs) with a screw-shaped structure. They are chiral molecules and have possible applications, for example, in optoelectronics or sensors. Synthesizing helicenes that are composed of one long spiral of fused benzene rings can be challenging, and their spectra do not change very much with increasing length. Thus, the development of other helicene-based nanographenes with tunable properties is an interesting research target.

Sujuan Wang, Jinchong Xiao, Hebei University, Baoding, China, and colleagues have synthesized a family of chiral [6]helicene-containing nanographenes (example structure pictured). The nanographenes were synthesized starting from, e.g., 9,14-diphenyldibenzo[de,qr]tetracene derivatives via Sonogashira and Scholl reactions.

The team confirmed the structure of one of the products using X-ray crystallography (pictured). In the solid state, the P and M enantiomers of the nanographene are stacked into dimers with a ratio of 1:1. The packing in the crystal indicates that the product might be useful, e.g., for applications in electronic devices. In addition, the isolated enantiomers show interesting chiroptical properties, such as circularly polarized luminescence (CPL).

• π-Expanded [6]Helicene-Containing Nanographenes: Synthesis, Structures, and Chiroptical Properties,
  Tongtong Ye, Yiming Li, Yanwei Shi, Yi Che, Bihan Leng, Sujuan Wang, Jinchong Xiao,
  Org. Lett. 2024.
  https://doi.org/10.1021/acs.orglett.4c02273