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 (H 2 DAC) 2 Bi 2 I 10  ⋅ 6H 2 O (H 2 DAC_Bi_I), 0-D (H 2 DAF) 4 Bi 2 I 10  ⋅ 2I 3  ⋅ 2I ⋅ 6H 2 O (H 2 DAF_Bi_I), and 1-D (H 2 DAP)BiI 5 (H 2 DAP_Bi_I) (where H 2 DAC=trans-1,4-diammoniumcyclohexane; H 2 DAF=2,7-diammoniumfluorene and H 2 DAP=1,5-diammoniumpentane). Their synthesis, single-crystal X-ray structures, and photophysical properties are reported. The first two compounds comprise edge-sharing [Bi 2 I 10 ] 4- dimers, while the last compound has cis-corner-sharing 1-D chains of [BiI 6 ] 3- octahedra. Intercalation of triiodide (I 3 - ) and iodide (I - ) ions enhance electronic coupling between the [Bi 2 I 10 ] 4- of H 2 DAF_Bi_I, leading to enhanced optical absorption, compared to H 2 DAC_Bi_I which lacks such intercalants. Furthermore, calorimetric and variable temperature X-ray diffraction measurements suggest a centrosymmetric to non-centrosymmetric phase transition (monoclinic P2 1 2 1 2 1 ↔orthorhombic Pnma) of H 2 DAP_Bi_I at 448 K (in heating step) and at 443 K (in cooling step).