Conformer‐Mediated Helical Chirality in 2D Layered Hybrid Perovskites

Abstract Two‐dimensional (2D) chiral hybrid perovskites A 2 PbI 4 (A: chiral organic ion) enable chirality controlled optoelectronic and spin‐based properties. A + organic sublattice induces chirality into the semiconducting [PbI 4 ] 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) 2 PbI 4 and ( S ‐IdPA) 2 PbI 4 (IdPA: 1‐iodopropan‐2‐ammonium) which crystallize in the helical enantiomorphic space groups P4 3 2 1 2 and P4 1 2 1 2, 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 [PbI 4 ] 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 (4 3 and 4 1 ). The enantiomers ( R ‐/ S ‐IdPA) 2 PbI 4 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.