Chiral organic hybrids for nonlinear optical applications and solvent-induced reversible red–yellow color change

Chiral hybrid metal halides hold great promise for the development of next-generation optoelectronic devices, owing to their asymmetric structures. Here, a series of one-dimensional chiral lead-halide hybrids with non-centrosymmetric structures were developed, including (R/S-C₁₂H₂₀N₂)Pb₂I₆·2H₂O, (R/S-C₁₂H₂₀N₂)SbI₅, and (R/S-C₁₂H₂₀N₂)BiI₅ (where [R/S-C₁₂H₂₀N₂]²⁺ refers to (R)-3-amino-1-benzylpiperidine and (S)-1-benzyl-3-aminopiperidine cations). (R-C₁₂H₂₀N₂)Pb₂I₆·2H₂O exhibits second harmonic generation (SHG) 3.3 times that of KH₂PO₄. Replacing Pb with Sb or Bi results in a slight reduction in the SHG intensity compared with (R/S-C₁₂H₂₀N₂)XI₅ (X = Sb, Bi) and a transition to a higher-symmetry space group. Furthermore, (R/S-C₁₂H₂₀N₂)SbI₅ exhibits a rapid and reversible amorphization-induced color transition from red to yellow upon exposure to a solvent (H₂O), highlighting its potential for applications in sensing and anti-counterfeiting technologies. These findings suggest that the R/S-C₁₂H₁₈N₂ series crystals are promising candidates for laser applications and hold potential in water detection, anti-counterfeiting, and information encryption.