Axial chirality-induced rigidification in aminoboranes enhances persistent room-temperature phosphorescence and circularly polarized luminescence

Long-lived triplet exciton harvesting materials are of immense interest for applications in bioimaging, optoelectronics, anticounterfeiting, and sensing. However, achieving persistent room-temperature phosphorescence (pRTP) in metal-free systems remains a significant challenge. Herein, we present purely organic axially chiral aminoboranes (R/S-(BN)₂) with enhanced pRTP properties and circularly polarized luminescence (CPL). By introducing axial chirality, the dual-core (R/S-(BN)₂) system achieves steric-hindrance-caused rigidity, which restricts molecular motions, leading to superior phosphorescence properties. Notably, R-(BN)₂ demonstrates a phosphorescence quantum yield (Φ_P) of 9.2% (S-(BN)₂ : Φ_P = 8.7%) and an extended lifetime of 0.9 sec at room temperature, significantly outperforming its mono-core counterpart (BN)₁ (Φ_P = 3.0% and τ_P = 0.6 s). Theoretical analysis corroborates the observed improvements, revealing the synergistic role of borylation and axial chirality in stabilizing triplet states. Furthermore, the axially chiral aminoboranes exhibited CPL in dichloromethane solutions with a dissymmetry factor of ~10^-3. These findings highlight the potential of axially chiral frameworks in designing efficient metal-free pRTP materials, as demonstrated in the security writing application, further paving the way for their use in bioimaging, anti-counterfeiting technologies, and next-generation organic electronics.