Customizing circularly polarized afterglow by stepwise chiral amplification in BINAPs/BINAPOs

Abstract

Overcoming spin-forbidden radiation in chiral phosphors has attracted enormous attention because of their capacity to exhibit circularly polarized organic ultra-long room temperature phosphorescence (CP-OURTP). However, their development has been hindered by the short lifetimes and low dissymmetry factors, which are attributed to the differing parity selection rules that govern the electric and magnetic dipole moments in chiral molecules and poor triplet populations via intersystem crossing (ISC). Considering stepwise chiral amplification at molecular and supramolecular aspects, herein, we first reported donor-decorated BINAPs/BINAPOs with tunable D–A character and triplet incubation, which could enable hybridized local and charge-transfer (HLCT) characteristics, heavy atoms, and p–π* effects. These emitters could serve as guests in the polymer matrix. The doped phosphorescent polymer exhibits unimolecular circularly polarized luminescence (C) with high quantum efficiency, impressive CP-OURTP lifetimes (up to 1.02 s), and decent dissymmetry factors (10⁻³ level). Comprehensive studies unveil that the impressive CP-OURTP from monomer emission is ascribed to the ¹HLCT-controlled ISC, long-lived ³LE-governing triplet radiation, and superior electric–magnetic dipole moment environments. Moreover, given the high RTP activity of rigid polymerization, we demonstrate their potential application in CP-OURTP amplification. Using in situ chiral liquid crystal polymerization, RM257 liquid crystals doped with 0.1–1.0 wt% PO1 guests demonstrate a secondary helical assembly, showing an amplified g_CP-RTP factor (±0.11) and a long lifetime (0.83 s) after photopolymerization. The current materials' excellent performance in CP-OURTP and structural dependence could lead to their use in afterglow patterns for multiple optical encryption.