Crystal and electronic structures of alaninePbX₃ monohydrates (X=Br, I)

Chiral organic–inorganic hybrid perovskites are promising materials for spintronic and optoelectronic applications due to their non-centrosymmetric structures and tunable electronic band structures. Here, we report the crystal growth and characterization of L-, D-, and DL-alaninePbBr₃·H₂O and alaninePbI₃·H₂O. Single-crystal X-ray diffraction analysis reveals the enantiomeric crystals crystallize in the polar space group C2, whereas the racemic counterparts adopt a centrosymmetric structure. Density functional theory calculations based on the experimental structures show that the valence band maximum arises primarily from Pb-6s orbitals, while the conduction band minimum comprises antibonding states of Pb-6p and halide-p. Bonding orbitals of Pb-6p–halide-p are located at deeper energies (~−2 eV). Both compounds exhibit direct bandgaps at the M point of the Brillouin zone: 2.79 eV (Br) and 2.26 eV (I). These results demonstrate how the molecular chirality governs crystallographic symmetry and the electronic structure, providing a platform for designing chiral semiconductors with tailored optical and spin-related functionalities.