Symmetry Breaking and Two-Step Spin-Crossover Behavior in Two Cyano-Bridged Mixed-Valence {FeIII2(μ-CN)4FeII2} Clusters.
Chunyang ZhengShuwen JiaYubao DongJuping XuHuanhuan SuiFeng WangDong-Feng LiPublished in: Inorganic chemistry (2019)
Two new cyano-bridged mixed-valence {FeIII2(μ-CN)4FeII2} clusters, {[(Tp)FeIII(CN)3]2[FeII(Py2N2)]2}·(ClO4)2·MeCN·Et2O (1·MeCN·Et2O), its solvent-free form (1), and {[(Tp)FeIII(CN)3]2[FeII(Me2Py2N2)]2}·(ClO4)2·5MeOH (2·5MeOH), were obtained [Tp = hydrotris(pyrazol-1-yl)borate; N,N'-bis(2-pyridylmethyl)-N,N'-bis(4-X-benzyl)-1,2-ethanediamine, Py2N2, X = H; Me2Py2N2, X = Me]. Complexes 1 and 2·5MeOH exhibit gradual thermally induced two-step spin-crossover behavior (SCO) at two FeII metal centers, and the transformation of high-spin (HS) to low-spin (LS) FeII ions with temperature was confirmed by a combination of X-ray crystallography, variable-temperature Fourier transform infrared, variable-temperature magnetic susceptibility, and 57Fe Mössbauer spectroscopy. Moreover, complexes 1·MeCN·Et2O and 1 exhibit a reversible single-crystal-to-single-crystal transformation, and complex 1 undergoes two-step SCO behavior with T1/2 = 178 and 93 K accompanied by symmetry breaking in the structure.
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