Spin-crossover in the complex of iron(II) nitrate with tris(3,5-dimethylpyrazol-1-yl)methane

Novel coordination compound [Fe(HC(3,5-Mepz)3)2](NO3)2 is obtained by a reaction of Fe(NO3)2 with tris(3,5-dimethylpyrazol-1-yl)methane. The compound is characterized with magnetic susceptibility method, electronic (diffuse reflection) and IR spectroscopy and powder diffraction. According to temperature dependence μeff(T) the compound possesses spin-crossover 1A1 ⇔ 5T2 with hysteresis (Tc↑ = 231, Tc↓ = 227 K) accompanied by thermochromism (pink ⇔ colorless). A crystal structure of the compound was determined just before (T = 240 K, FeHS–N 2.14–2.18 Å) and after (T = 123 K, FeLS–N 1.97–1.99 Å) spin phase transition.

Graphical abstractNovel coordination compound [Fe(HC(3,5-Mepz)3)2](NO3)2 possesses spin-crossover 1A1 ⇔ 5T2 (Tc = 231 K and Tc = 227 K) accompanied by thermochromism (pink colorless), which crystal structure was determined before and after spin phase transition.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Novel compound [Fe(HC(3,5-Mepz)3)2](NO3)2 possesses spin-crossover 1A1 ⇔ 5T2. ► Critical temperatures are 231 K (heating) and 227 K (cooling). ► Spin-crossover is accompanied by thermochromism (pink ⇔ colorless). ► Magnetic susceptibility curve shows hysteresis of 4 K. ► Crystal structure from single crystal was determined before and after spin-crossover.