Chiral Bimetallic\nCuprous-Lead Hybrid Iodide Single\nCrystals toward Occurrence of Second Harmonic Generation

Hybrid\nbimetallic halides with two different optical\nactivities\nhave exhibited excellent optical properties, which demonstrates great\npotential in the optoelectronic fields. To develop hybrid cuprous-lead\nbimetallic halides with unique non-centrosymmetric structures, we\nintroduced the chiral cations <i>R</i>/<i>S</i>-2-C<sub>5</sub>H<sub>14</sub>N<sub>2</sub><sup>2+</sup> (C<sub>5</sub>H<sub>14</sub>N<sub>2</sub><sup>2+</sup> = methylpiperazinium) into\ninorganic frameworks containing two different heterometallic cuprous\nand lead cations, respectively, and successfully obtained the novel\nchiral hybrid bimetallic halides of (<i>R</i>/<i>S</i>-2-C<sub>5</sub>H<sub>14</sub>N<sub>2</sub>)<sub>3</sub>Cu<sub>2</sub>Pb<sub>2</sub>I<sub>12</sub> single crystals by the hydrothermal\nmethod. Bimetallic anionic [Cu<sub>2</sub>Pb<sub>2</sub>I<sub>12</sub>]<sup>6–</sup> framework structures were constructed from\ntwo different [PbI<sub>6</sub>]<sup>4–</sup> and two different\n[CuI<sub>4</sub>]<sup>3–</sup> twisted polyhedra, and band\ngap calculations were demonstrated. Most importantly, chiral crystal\nstructures of (<i>R</i>/<i>S</i>-2-C<sub>5</sub>H<sub>14</sub>N<sub>2</sub>)<sub>3</sub>Cu<sub>2</sub>Pb<sub>2</sub>I<sub>12</sub> were confirmed by circular dichroism (CD), and their\nanisotropy factor (<i>g</i><sub>CD</sub>) values were –5.98\n× 10<sup>–5</sup> and +5.79 × 10<sup>–5</sup>, respectively. Besides, significant second harmonic generation of\n(<i>R</i>/<i>S</i>-2-C<sub>5</sub>H<sub>14</sub>N<sub>2</sub>)<sub>3</sub>Cu<sub>2</sub>Pb<sub>2</sub>I<sub>12</sub> single crystals was also exhibited through the coupling of chiral\norganic cations and inorganic anionic [Cu<sub>2</sub>Pb<sub>2</sub>I<sub>12</sub>]<sup>6–</sup> frameworks. This work not only\nprovides guidance for understanding the structure–property\nrelationship of novel chiral hybrid bimetallic halides, but also extends\nthe further optoelectronic applications of these hybrid halide systems.