Spin crossover in homo- and heteroligand iron(II) complexes with tris(pyrazol-1-yl)methane derivatives

The studies concerning coordination compounds of various salts of iron(II) with tris(pyrazol-1-yl)methane derivatives (HC(pz)₃) are discussed. The results of a number of studies on the synthesis and investigation of the homo- and heteroligand iron(II) complexes with tris(3,5- dimethylpyrazol-1-yl)methane (HC(3,5-Me₂pz)₃) are considered. The study of the temperature dependence μ_eff (T) showed that the spin crossover (SCO) ¹A₁?⁵T₂ observed in a series of the compounds discussed is accompanied by thermochromism (color change pink (purple) ? colorless). Specific features of the SCO and their dependence on the outer-sphere anion in the iron(II) complexes are discussed. The data of the recently published work devoted to the synthesis of the iron(II) complexes with three N-substituted HC(pz)₃ derivatives (general formula ^xL, where x = H, CH₂C₆H₅ (Bn) and p-SO₃C₆H₄CH₃ (Ts)) are considered.