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 (HDAC)BiI ⋅ 6HO (HDAC_Bi_I), 0-D (HDAF)BiI ⋅ 2I ⋅ 2I ⋅ 6HO (HDAF_Bi_I), and 1-D (HDAP)BiI (HDAP_Bi_I) (where HDAC=trans-1,4-diammoniumcyclohexane; HDAF=2,7-diammoniumfluorene and HDAP=1,5-diammoniumpentane). Their synthesis, single-crystal X-ray structures, and photophysical properties are reported. The first two compounds comprise edge-sharing [BiI] dimers, while the last compound has cis-corner-sharing 1-D chains of [BiI] octahedra. Intercalation of triiodide (I ) and iodide (I) ions enhance electronic coupling between the [BiI] of HDAF_Bi_I, leading to enhanced optical absorption, compared to HDAC_Bi_I which lacks such intercalants. Furthermore, calorimetric and variable temperature X-ray diffraction measurements suggest a centrosymmetric to non-centrosymmetric phase transition (monoclinic P222↔orthorhombic Pnma) of HDAP_Bi_I at 448 K (in heating step) and at 443 K (in cooling step).