All microcrystalline samples were initially assessed for their purity via their X-ray powder diffraction patterns, measured using a PANalytical Empyrean diffractometer (Cu Kα radiation, λ = 1.541 Å). High resolution synchrotron measurements on Cr[Bi(SCN) 6 ] were carried out at beamline 11-BM at the Advanced Photon Source (APS) using a wavelength of 0.414537 Å and on Cr[Bi(SCN) 6 ] • H 2 O at beamline I11 at the Diamond Light Source, using a wavelength of 0.826168 Å. Variable temperature powder diffraction measurements on Cr[Bi(SCN) 6 ] • H 2 O were carried out at beamline I11 at the Diamond Light source, using a hot air blower, and on Cr[Bi(SCN) 6 ] on a PANalytical Empyrean diffractometer using a Anton Parr XRK 900 furnace. Analysis of all powder diffraction data (including indexing, Pawley refinement and Rietveld refinement) was carried out using the TOPAS Academic 4.1 structure refinement software package. Full details of the powder X-ray refinements can be found in the supplementary information.