Chiral Fluorine Engineering in Amine Molecular Design: Toward High‐ T _c Multifunctional Rare‐Earth Hybrid Double Perovskites

Abstract Chiral organic‐inorganic hybrid rare‐earth double perovskites represent an emerging multidisciplinary frontier that synergizes structural diversity, rare‐earth functionalities, and chirality‐driven phenomena. In this study, a chiral F‐engineering strategy is developed to synthesize three novel hybrid double perovskites: ( Rac ‐3‐DMFP) ₂ RbEu(NO ₃ ) ₆ ( Rac ‐1 ) and its enantiopure analogues ( R / S ‐3‐DMFP) ₂ RbEu(NO ₃ ) ₆ ( R / S ‐1 ). The intrinsic chirality of enantiomers R ‐1 and S‐ 1 is unambiguously confirmed by vibrational circular dichroism (VCD) spectroscopy. Compared to the racemic Rac ‐1 , the enantiomeric R / S ‐1 pair exhibits enhanced functionalities, including reversible phase transitions at elevated temperatures, distinct dielectric anomalies, and superior second‐harmonic generation (SHG) responses with SHG intensities surpassing those of conventional NO ₃ ⁻ ‐based perovskites. Comprehensive optoelectronic characterization leveraging the f‐f transition of Eu ³⁺ ions revealed broad UV absorption (250–400 nm), intense red luminescence ( ⁵ D ₀ → ⁷ F ₂ at 615 nm), a prolonged fluorescence lifetime ( τ = 3.89 ms), and a notable quantum yield ( Φ = 32.23%). This work establishes an effective molecular design strategy for exploring and constructing multifunctional organic‐inorganic hybrid rare‐earth double perovskites, highlighting their potential in advanced optoelectronics and nonlinear optical technologies.