Planar chirality is one of the unique features of mono- and polysubstituted [2.2]paracyclophane compounds. The potential applications of the [2.2]paracyclophane derivatives in materials chemistry necessitate the further development of practical optical resolution methods for planar chiral [2.2]paracyclophanes. Recently, we achieved the optical resolutions of 4,12-disubstituted [2.2]paracyclophane [1] and 4,7,12,15-tetrasubstituted [2.2]paracyclophane compounds [2]. By using the optically pure 4,12-disubstituted and 4,7,12,15-tetrasubstituted [2.2]paracyclophanes, we have prepared various planar chiral [2.2]paracyclophane building blocks [3] for π-system figuration. Herein, their optical resolution methods as well as subsequent transformations to the enantiopure conjugated compounds will be shown. As a representative example of π-system figuration, cyclic compounds based on planar chiral [2.2]paracyclophane will be introduced. These compounds comprise optically active higher-ordered structures such as propeller-shaped structure [2], double helical structure [3], and so on. They exhibit excellent chiroptical properties, i.e., large molar ellipticity in the ground state and intense circularly polarized luminescence (CPL) with large dissymmetry factors (g_lum) in the exited state. The results suggest that planar chiral [2.2]paracyclophane-based optically active higher-ordered structures (propeller-shaped and double helical structures in this study) are promising scaffolds for efficient CPL, and appropriate modifications can enhance the CPL properties.

References

[1] (a) Morisaki, Y.; Hifumi, R.; Lin, L.; Inoshita, K.; Chujo Y. Chem. Lett. 2012, 41, 990. (b) Morisaki, Y.; Hifumi, R.; Lin, L.; Inoshita, K.; Chujo Y. Polym. Chem. 2012, 3, 2727. (c) Morisaki, Y.; Inoshita, K.; Chujo Y. Chem.–Eur. J. 2014, 20, 8386.

[2] (a) Morisaki, Y.; Gon, M.; Sasamori, T.; Tokitoh, N.; Chujo Y. J. Am. Chem. Soc. 2014, 136, 3350. (b) Gon, M.; Morisaki, Y.; Chujo Y. J. Mater. Chem. C 2015, 3, 521.

[3] For example, Morisaki, Y.; Sawada, R.; Gon, M.; Chujo Y. Chem.–Asian J. 2016, 11(18), 2524.