0-D and 1-D Perovskite-like Hybrid Bismuth(III) Iodides

Low-dimensional hybrid bismuth halide perovskites have recently emerged as a class of non-toxic alternative to lead perovskites with promising optoelectronic properties. Here, we report three hybrid bismuth(III)-iodides: 0-D (H₂DAC)₂Bi₂I₁₀ ⋅ 6H₂O (H₂DAC_Bi_I), 0-D (H₂DAF)₄Bi₂I₁₀ ⋅ 2I₃ ⋅ 2I ⋅ 6H₂O (H₂DAF_Bi_I), and 1-D (H₂DAP)BiI₅ (H₂DAP_Bi_I) (where H₂DAC=trans-1,4-diammoniumcyclohexane; H₂DAF=2,7-diammoniumfluorene and H₂DAP=1,5-diammoniumpentane). Their synthesis, single-crystal X-ray structures, and photophysical properties are reported. The first two compounds comprise edge-sharing [Bi₂I₁₀]^4- dimers, while the last compound has cis-corner-sharing 1-D chains of [BiI₆]^3- octahedra. Intercalation of triiodide (I₃ ^-) and iodide (I^-) ions enhance electronic coupling between the [Bi₂I₁₀]^4- of H₂DAF_Bi_I, leading to enhanced optical absorption, compared to H₂DAC_Bi_I which lacks such intercalants. Furthermore, calorimetric and variable temperature X-ray diffraction measurements suggest a centrosymmetric to non-centrosymmetric phase transition (monoclinic P2₁2₁2₁↔orthorhombic Pnma) of H₂DAP_Bi_I at 448 K (in heating step) and at 443 K (in cooling step).