Tuning Photophysical and Chiroptical Properties of [7]Helicene through Formation of Imidazole-Based Push−Pull Systems

Circularly polarized light has attracted considerable attention in recent years due to its potential applications in modern optoelectronics, display technologies, quantum information systems, and advanced data encryption. Among the most promising molecular systems capable of emitting such light are helicenes – aromatic hydrocarbons whose structure resembles a molecular spring or helix. Owing to this three-dimensional asymmetry, helicenes exist in two mirror-image forms, much like left and right hands. Despite their appeal for these applications, helicenes suffer from one major drawback: most of them emit light rather inefficiently. Researchers have therefore been searching for ways to enhance their fluorescence while preserving their ability to generate circularly polarized light.

In a recent study, scientists from the Research Group of Advanced Materials and Organic Synthesis focused on [7]helicene and its incorporation into an imidazole-containing framework. They prepared a series of nine new helicene derivatives and investigated how this modification affects their optical properties.

The results showed that introducing an imidazole unit significantly improves the fluorescence performance of these molecules. While the parent [7]helicene exhibits a fluorescence quantum yield of only about 2%, the best-performing derivatives achieved values exceeding 22%. Importantly, all prepared compounds retained their blue emission, centered around 450 nm, a highly desirable feature for future optoelectronic applications. Interestingly, the different molecular properties influence one another. Some modifications led to a slight reduction in parameters describing the “chiral character” of the emitted light. However, this effect was more than compensated for by substantial increases in both light absorption and fluorescence efficiency. As a result, the overall CPL brightness—a parameter describing the efficiency of circularly polarized light emission—improved dramatically. The best compounds exhibited up to a 15-fold increase in CPL brightness compared with the parent [7]helicene.

This study demonstrates that the formation of imidazole-based push–pull systems represents a simple and effective strategy for enhancing the performance of helicene luminophores. The findings may contribute to the development of a new generation of chiral organic materials for circularly polarized OLEDs, optical sensors, and other future photonic technologies.

• Kos M., Beránek T., Takase S., Žádný J., Sýkora J., Císařová I., Storch J., Církva V., Jakubec M.: Tuning Photophysical and Chiroptical Properties of [7]Helicene through Formation of Imidazole-Based Push−Pull Systems. J. Org. Chem. 2026, 91(22), 7391-7399. doi.org/10.1021/acs.joc.6c00092