Circularly Polarized Luminescence with Large Dissymmetry Factor over 10^-1 Based on Flexible Point-Chirality via...

In this work, we report a series of small Spirocyclic Chiral Fluorophores (SCFs) with donor-acceptor type small-π emitters. These SCFs induce mimic α-helix supramolecular packing modes via adjustments at the molecular level (e.g., hydrogen bonding sites, positions of fused rings). This approach not only enhances circularly polarized luminescence (CPL) with the luminescence dissymmetry factor (g_lum) up to 0.18 in assembled materials but also enables inversion of the chiral signal. Moreover, unlike most CPL materials with a single point-chiral center that are CPL-silent at the molecular state, the spirocyclic configuration can enhance efficient point-chirality transfer to the fluorophores owing to the self-rigidified skeleton, consequently enable efficient CPL with the g_{l um} in the order of 10^-3 even in the molecular solutions. The mechanistic insights are revealed by experimental investigation including the femtosecond transient absorption (fs-TA) spectroscopy and single-crystal analysis, as well as DFT calculation. This study opens new avenues for developing organic CPL materials with large g values based on low-molecular-weight flexible point-chiral fluorophores, offering great potential for future applications in biotechnology and circularly polarized organic light-emitting diodes (CP-OLEDs).