The structural versatility of proton sponge bismuth halides

Hybrid halometalates containing lead, tin, bismuth and antimony organic cations have recently shown a bevy of interesting photophysical properties. Aiming at finding chemically stable thermally inert species, three halobismutate species this class, crystallized with proton sponge-derived (PRSH), been isolated as microcrystalline powders by mixing 1,8-bis(dimethylamino)-naphthalene (proton sponge, or PRS) oxide in concentrated HX acids (X ​= ​Cl, Br I). The two isomorphous (PRSH)3Bi2X9 ​Br, I) [Bi2X9]3- anions, are triclinic room temperature convert upon heating into monoclinic structure through displacive phase transformation, fully reversible for X ​I only partially ​Br. At variance, (PRSH)BiCl4 is polymeric, contains extended zigzagging 1D chains formed edge-sharing BiCl6 octahedra. These were extensively studied synchrotron laboratory X-ray powder diffraction measurements, which enabled to detect the evolution toward high-temperature β-phases I), derive five different (significantly complex) assess thermal strain tensors regimes. Additional thermal, spectroscopic computational analyses completed characterization these materials.