Dual-Color Tunable Circularly Polarized Luminescence With Anti-Thermal-Quenching Enabled by Asymmetric...

Constructing chiral metal halides without relying on chiral organic cations offers exceptional compositional and structural freedom, yet their rational design remains challenging due to the limited understanding of the origins of structural chirality. Here, by employing the achiral 4-benzylpiperidine (4-BPP) cation and controlling the crystallization pathways, we access two distinct manganese bromide polymorphs: centrosymmetric α-(4-BPP)₂MnBr₄ (space group I2/a) and chiral β-(4-BPP)₂MnBr₄ (space group P2₁). Detailed crystallographic analysis reveals that asymmetric hydrogen-bonding interactions at the organic-inorganic interface of β-(4-BPP)₂MnBr₄ amplify the distortion of [MnBr₄]^2- tetrahedra, driving symmetry breaking and giving rise to inherent chirality. The resulting chiral phase exhibits anti-thermal-quenching green-red dual emission, in which the red component originates from distortion-induced self-trapped excitons and is further modulated via energy transfer from green-emissive Mn²⁺ centers. Consequently, dual-color tunable circularly polarized luminescence (CPL) is realized in chiral metal halides for the first time, featuring a large dissymmetry factor (g_lum) of 7 × 10^-2. Moreover, the non-centrosymmetric crystal structure enables efficient second- and third-harmonic generation. These findings elucidate how hydrogen-bonding interactions govern structural chirality at the molecular level and establish a general design principle for engineering chiroptical and nonlinear optical properties in metal halides.