High-temperature spin-crossover in coordination compounds of iron(II) with tris(pyrazol-1-yl)methane

Novel mononuclear Fe(II) complexes of tris(pyrazol-1-yl)methane [Fe{HC(pz)3}2]2+ with SiF62- and p-sulfonatothiacalix[4]arene (TCAS4−) as counterions were obtained. The compounds were characterized by magnetic susceptibility method, IR and UV–Vis spectroscopy. The structure of [Fe{HC(pz)3}2]SiF6 has been analyzed by single-crystal X-ray diffraction. The 1H NMR spectroscopy measurements of [Fe{HC(pz)3}2]2(TСAS) in aqueous solution reveal the outer sphere inclusion of [Fe{HC(pz)3}2]2+ into the cyclophanic cavity of TCAS4−. The temperature induced spin-crossover 1А1 ⇔ 5Т2, accompanied by thermochromism, has been revealed from the temperature dependence of μeff and IR spectra for both complexes. The comparative analysis of magnetochemical and spectroscopy data elucidates the effect of the cyclophanic counterion on the physico-chemical properties of Fe(II) complex.

Fe(II) complexes of tris(pyrazol-1-yl)methane [Fe{HC(pz)3}2]2+ with SiF62- and p-sulfonatothiacalix[4]arene (TCAS4−) as counterions are obtained and characterized by several methods, including single-crystal X-ray diffraction. Less abrupt transition and a significantly higher temperature of spin-crossover 1А1 ⇔ 5Т2 of [Fe{HC(pz)3}2]2[TСAS] relative to [Fe{HC(pz)3}2]SiF6 are attributed to the inclusion of [Fe{HC(pz)3}2]2+ into the cavity of TCAS4−.Figure optionsDownload as PowerPoint slide