Two 3D Rare-Earth Double Perovskite Materials Constructed with a Pair of Enantiomers

Organic–inorganic hybrid chiral small-molecule materials combine the inherent properties of both components; however, studies integrating chirality with rare-earth double-perovskite materials are limited. In this work, we synthesized two enantiomers of three-dimensional (3D) hybrid rare-earth double-perovskites, [ R -3-HDMP] 2 CsEu(NO 3 ) 6 ( 1 ) and [ S -3-HDMP] 2 CsEu(NO 3 ) 6 ( 2 ), by reacting R -3-HDMP and S -3-HDMP (where 3-HDMP = 3-hydroxy- N,N -dimethylpyrrole) with CsNO 3 and Eu(NO 3 ) 3 in a 2:1:1 ratio within an acidic solution. Both R -3-HDMPI and S -3-HDMPI crystallize in the chiral space group P 2 1 2 1 2 1 at room temperature, exhibiting a transition from SHG-on to SHG-off (SHG = second harmonic generation) upon heating and cooling. The temperature-dependent X-ray single-crystal diffraction analysis carried out on compound 1 and compound 2, before and after the phase transition, disclosed the transformation of their space groups from noncentrosymmetric to centrosymmetric. Additionally, the incorporation of rare-earth elements as hybrid B-site cations imparts exceptional fluorescence properties to the compounds. These materials effectively merge the unique characteristics of chiral molecules with the exceptional luminescence of double-perovskite structures, paving the way for innovative optical devices and advanced information processing technologies.