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]2CsEu(NO3)6 (1) and [S-3-HDMP]2CsEu(NO3)6 (2), by reacting R-3-HDMP and S-3-HDMP (where 3-HDMP = 3-hydroxy-N,N-dimethylpyrrole)
with CsNO3 and Eu(NO3)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 P212121 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.