Naphthalimide-Annulated []Helicenes: Red Circularly Polarized Light Emitters.

Two []heliceno-bis(naphthalimides) and ( = 5 and 6, respectively) where two electron-accepting naphthalimide moieties are attached at both ends of helicene core were synthesized by effective two-step strategy, and their enantiomers could be resolved by chiral stationary-phase high-performance liquid chromatography (HPLC). The single-crystal X-ray diffraction analysis of enantiopure fractions of and confirmed their helical structure, and together with experimental and calculated circular dichroism (CD) spectra, the absolute configuration was unambiguously assigned. Both and exhibit high molar extinction coefficients for the S-S transition and high fluorescence quantum yields (73% for and 69% for ), both being outstanding for helicene derivatives. The red circularly polarized luminescence (CPL) emission up to 615 nm for with CPL brightness () up to 66.5 M cm demonstrates its potential for applications in chiral optoelectronics. Time-dependent density functional theory (TD-DFT) calculations unambiguously showed that the large transition magnetic dipole moment || of is responsible for its high absorbance dissymmetry () and luminescence dissymmetry () factor.