Inverted Chiroptical Properties of Hybrid Metal Halides Through Reversible Chiral Induction Driven by External and Internal Chirality Transfer

Chiral organic-inorganic hybrid metal halides (OIHMHs) are commonly constructed by introducing pairs of enantiomorphic chiral precursors through a single chirality transfer pathway, which may limit the regulation of chiral structural diversity and chiroptoelectronic properties. Herein, we propose a new strategy for achieving reversible chiral induction of OIHMHs with inverted chiroptical properties through external and internal chirality transfer pathways, by utilizing a single chiral reagent R-/S-α-methylbenzylamine (R-/S-MBA). Specifically, R-MBA can externally induce chiral enrichment of M-DMA₄(Bi_0.486In_0.511Sb_0.003)Cl₇ (M-DMA₄(Bi-In-Sb)Cl₇, DMA = dimethylammonium cation) without integrating into structure. Conversely, R-MBA can insert into structure, internally inducing the formation of DMA(R-MBA)₂(Bi_0.634In_0.362Sb_0.004)Cl₆ (DMA(R-MBA)₂(Bi-In-Sb)Cl₆), which reverses the structural arrangements and inverts both linear and nonlinear chiroptical properties. Both externally and internally induced chiral OIHMHs exhibit significant chiroptical responses with high photoluminescence quantum yield (PLQY) and second harmonic generation (SHG). Moreover, the externally induced centimeter-sized rhombic single crystal enables morphology- and angle-dependent inverted circularly polarized luminescence with a dissymmetry factor of ∼0.02, through single crystal anisotropy. The internal induction enhances SHG intensity by nine-fold and increases PLQY to 98.9%. This multi-path chirality transfer, based on a single chiral reagent, can significantly broaden the structural scope of functional chiral OIHMH materials and facilitate the regulation of chiroptoelectronic properties.