10.1021/ic403035u.s002 Irene Bräunlich Irene Bräunlich Antoni Sánchez-Ferrer Antoni Sánchez-Ferrer Matthias Bauer Matthias Bauer Rahel Schepper Rahel Schepper Philippe Knüsel Philippe Knüsel Julia Dshemuchadse Julia Dshemuchadse Raffaele Mezzenga Raffaele Mezzenga Walter Caseri Walter Caseri Polynuclear Iron(II)–Aminotriazole Spincrossover Complexes (Polymers) In Solution American Chemical Society 2014 EXAFS molar NH 2trz ratio DMF SCO SAXS NH 2trz polynuclear species UV Fe equilibrium XANES 2014-04-07 00:00:00 Dataset https://acs.figshare.com/articles/dataset/Polynuclear_Iron_II_Aminotriazole_Spincrossover_Complexes_Polymers_In_Solution/2308357 Polynuclear spincrossover (SCO) complexes prepared by the combination of [Fe­(DMF)<sub>6</sub>]<sup>2+</sup> and NH<sub>2</sub>trz (NH<sub>2</sub>trz = 4-amino-1,2,4-triazole) were studied (2ns<sup>–</sup> = counterion 2-naphthalenesulfonate). It is demonstrated that these [Fe­(NH<sub>2</sub>trz)<sub>3</sub>]­(2ns)<sub>2</sub> complexes can be dissolvedcontrary to common reported experiencein <i>N</i>,<i>N</i>-dimethylformamide (DMF) and, therefore, can be conveniently processed by simple means. The resulting solutions were examined with UV/vis and X-ray absorption spectroscopy (XANES and EXAFS) as well as with small-angle X-ray scattering (SAXS). At a molar NH<sub>2</sub>trz/Fe<sup>2+</sup> ratio of 3/1, corresponding to the stoichiometric ratio of the ideal coordination compound, [Fe­(NH<sub>2</sub>trz)<sub>3</sub>]<sup>2+</sup> in the low-spin state was found to be in equilibrium with polynuclear species in the high-spin state. The equilibrium can be shifted virtually completely to the side of low-spin Fe<sup>2+</sup> by an excess of the ligand. The polymer therewith formed contains 100 or more Fe<sup>2+</sup> ions and is of a pronounced rigid-rod structure, with Fe–Fe distances around 3.32 Å (in comparison to 3.94 Å of the polynuclear species in the high-spin state). Reversible spin crossover takes place in solution upon a temperature increase to around 60 °C; this process is associated with a shift in equilibrium toward species shorter than the initial polynuclear species.