Abstract
A thorough investigation into the role of the counterion and occluded solvent on the structure and spin‐crossover behaviour of the threefold interpenetrated network [Fe(4__ditz__)~3~]^2+^ [4__ditz__ = 1,4‐bis(tetrazol‐1‐yl)butane] is presented. As seen by X‐ray single crystal diffraction, changing the hexafluorophosphate anion in the previously investigated trigonal phase Fe(4__ditz__)~3~~2~ to tetrafluoroborate causes the butylene spacers to adopt three different conformations, whereupon the symmetry is reduced to triclinic (space group P$\bar {1}$). X‐ray powder diffraction and NMR spectroscopy provide evidence for the incorporation of statistically distributed ethanol molecules in the cavities of the compound, whose amount depends on whether absolute ethanol or a binary system, ethanol/water (95:5, v/v), is used as solvent. The phase precipitated from EtOH/H~2~O features a metastable high‐spin (HS) state when rapidly cooled, a sharp spin transition to a mixed HS/LS (1:1) state at around 90 K on slow cooling with an approximately 10 K hysteresis and LIESST appears, whereas the sample synthesised from absolute ethanol shows a more gradual spin transition at the same temperature without hysteresis.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)