Structural diversity in proline-based lead bromide chiral perovskites

Lead halide hybrid perovskites incorporating chiral organic cations attract considerable attention due to their promising application in multifarious optoelectronic devices. However, the examples of chiral hybrid perovskites are still limited, which greatly impedes their further studies in various optoelectronic fields. Herein, we report on new low-dimensional lead-halide hybrid perovskites incorporating the enantiopure chiral α-amino acid L-proline. Two hybrid perovskites (L-proH)PbBr₃·H₂O (Pro-PbBr) and (L-proH)₄Pb₃Br₁₀·4H₂O (Pro-PbBr) have been synthesized by employing different ratios of organic and inorganic precursors. According to structural analysis, the inorganic sublattice of compound Pro-PbBr is built of one-dimensional (1D) [PbX₃]_∞ lead halide chains, whereas the inorganic sublattice of compound Pro-PbBr is built upon a rare two-dimensional (2D) [Pb₃Br₁₀]_∞⁴ honeycomb-type inorganic framework. Hirshfeld surface analysis revealed an important role of various hydrogen bonding interactions in providing the binding between organic and inorganic parts of these hybrid perovskites. The optical band gap values of new hybrid perovskites as estimated using the Tauc plot approach are 4.19 eV (Pro-PbBr) and 4.13 eV (Pro-PbBr). Also, new compounds display low-temperature broadband photoluminescence which can be attributed to the self-trapped excitons. These results show the potential of α-proline for constructing novel and highly demanded chiral hybrid perovskites, which will hold great promise for further optoelectronic applications.