Chiral Bimetallic Cuprous-Lead Hybrid Iodide Single Crystals toward Occurrence of Second Harmonic Generation

Hybrid bimetallic halides with two different optical activities have exhibited excellent optical properties, which demonstrates great potential in the optoelectronic fields. To develop hybrid cuprous-lead bimetallic halides with unique non-centrosymmetric structures, we introduced the chiral cations R/S-2-C₅H₁₄N₂²⁺ (C₅H₁₄N₂²⁺ = methylpiperazinium) into inorganic frameworks containing two different heterometallic cuprous and lead cations, respectively, and successfully obtained the novel chiral hybrid bimetallic halides of (R/S-2-C₅H₁₄N₂)₃Cu₂Pb₂I₁₂ single crystals by the hydrothermal method. Bimetallic anionic [Cu₂Pb₂I₁₂]^6- framework structures were constructed from two different [PbI₆]^4- and two different [CuI₄]^3- twisted polyhedra, and band gap calculations were demonstrated. Most importantly, chiral crystal structures of (R/S-2-C₅H₁₄N₂)₃Cu₂Pb₂I₁₂ were confirmed by circular dichroism (CD), and their anisotropy factor (g_CD) values were -5.98 × 10^-5 and +5.79 × 10^-5, respectively. Besides, significant second harmonic generation of (R/S-2-C₅H₁₄N₂)₃Cu₂Pb₂I₁₂ single crystals was also exhibited through the coupling of chiral organic cations and inorganic anionic [Cu₂Pb₂I₁₂]^6- frameworks. This work not only provides guidance for understanding the structure-property relationship of novel chiral hybrid bimetallic halides, but also extends the further optoelectronic applications of these hybrid halide systems.