Chiral Ligand-Induced Second-Harmonic Generation Response in Helical One-Dimensional Hybrid Lead Bromides

Chiral hybrid organic-inorganic metal halides have garnered broad attention due to their unique optoelectronic properties. Here, a pair of chiral helical lead halides, (d-/l-<i>pro</i>)PbBr₃·H₂O (<i>pro</i> = proline), with centimeter-size has been successfully synthesized via integrating three types of functional building units including chiral amino acid ligand, ns² metal cations, and halide anion. Their structures are composed of one-dimensional helical {[Pb₂Br₆]^2-}_∞ chains formed by face-sharing distorted [PbBr₆]^4- octahedra, which are separated by chiral cations and crystallize into the space group <i>P</i>2₁. They present a phase-matchable second-harmonic-generation (SHG) response and moderate birefringence. First-principles calculations elucidate that the effective SHG performances originate from the synergetic contribution of chiral cations and distorted [PbBr₆]^4- octahedra. This work not only enriches the structural chemistry of lead-based hybrid halides but also provides an important reference for the development of chiral metal halides.