Conformer‐Mediated Helical Chirality in 2D Layered Hybrid Perovskites

Two‐dimensional (2D) chiral hybrid perovskites A2PbI4 (A: chiral organic ion) enable chirality controlled optoelectronic and spin‐based properties. A+ organic sublattice induces chirality into the semiconducting [PbI4]2‐ inorganic sublattice through non‐covalent interactions at organic‐inorganic interface. Often, the A+ cations in the lattice have different orientations, leading to asymmetry in the non‐covalent interactions. In a novel approach, we use different conformers of A+ cations to create asymmetry in the non‐covalent interactions, thereby, achieving chiral perovskites with rare helical enantiomorphic structures. We prepared (R‐IdPA)2PbI4 and (S‐IdPA)2PbI4 (IdPA: 1‐iodopropan‐2‐ammonium) which crystallize in the helical enantiomorphic space groups P43212 and P41212, respectively. The gauche‐ and anti‐conformers of IdPA+ are arranged alternatively in the hybrid structure. Importantly, the anti‐conformer of IdPA+ ion have significantly stronger electrostatic, N‐H···I hydrogen bonding, and I···I halogen bonding interactions with the [PbI4]2‐ sublattice, compared to the gauche‐conformer. This periodic asymmetry in non‐covalent interactions caused by the alternative arrangement of gauche‐ and anti‐conformers induces chirality in the inorganic sublattice with four‐fold screw axes (4₃ and 4₁). The enantiomers (R‐/S‐IAP)2PbI4 show mirror‐image like circular dichroism from excitonic absorption of the inorganic sublattice. This conformer‐based design of chiral hybrid perovskites in helical space groups broadens material choices for advanced optoelectronic applications.