Dual Enhancement of Emission and Luminescence Dissymmetry Factor by Si-Heteroannulation of Double π-Helix

Organic emitters of circularly polarized luminescence (CPL), especially chiral π-conjugated molecules, are attracting research interest, but they remain challenges to maintain both high luminescence dissymmetry factor ( g lum ) and photoluminescence quantum yield (Φ PL ). Herein, we present a novel kind of CPL emitter by integrating a double π-helix and Si-heteroannulation. The targeted cyclooctatetraene-embedded perylene diimide dimers, namely, sila- and disila-annulated double π-helices ( 3 and 4 ), are synthesized via one-pot palladium-catalyzed Si–C bond formation. Single-crystal analyses reveal their unique double π-helical frameworks featuring a cyclobis[3]helicene substructure with enhanced structural rigidity and coplanarity by Si-heteroannulation. Enhanced fluorescence emission is thus achieved with Φ PL reaching 70%, which is attributed to the mitigation of nonradiative energy loss revealed by the theoretical results of reorganization energy and Huang–Rhys factors. Notably, the symmetrically bilateral disila-annulated double π-helix 4 exhibit excellent chiral activities both in the ground and excited states, with dissymmetry factors | g abs | of up to 0.015, | g lum | of up to 0.013, and CPL brightness ( B CPL ) of 207.3 M –1 cm –1, outperforming pristine double π-helix 2 . These results indicated that a comprehensive CPL performance could be achieved by rational molecular design.