The influence of the spin crossover on the crystal structure of the [Fe₃(hyetrz)₆(H₂O)₆](CF₃SO₃)₆ complex compound

[Fe₃(hyetrz)₆(H₂O)₆](CF₃SO₃)₆ (where hyetrz = 4-(2'-hydroxyethyl)-1,2,4-triazole) is an interesting linear, trinuclear iron(II) compound with incomplete spin crossover. We reinvestigated crystal structure of this compound in the wide temperature range because the knowledge only about the crystal structure in the initial and final phases is not sufficient to establish correlations between the structural and magnetic properties of the spin crossover system. The complex [Zn₃(hyetrz)₆(H₂O)₆](CF₃SO₃)₆ was used for comparison because it does not exhibit spin crossover phenomenon and it is isostructural with a high spin phase of Fe(II).