Unprecedented bistability domain and interplay between spin crossover and polymorphism in a mononuclear iron(ii) complex
作者:Mark B. Bushuev、Vasiliy A. Daletsky、Denis P. Pishchur、Yuri V. Gatilov、Ilya V. Korolkov、Elena B. Nikolaenkova、Viktor P. Krivopalov
DOI:10.1039/c3dt53440e
日期:——
A mononuclear complex, [FeL2](BF4)2·xH2O (1LS·xH2O), where L is 4-(3,5-dimethyl-1H-pyrazol-1-yl)-2-(pyridin-2-yl)-6-methylpyrimidine, can be converted into several phases showing different spin crossover regimes. In the first heating 1LS·xH2O loses water molecules and converts into a mixture of two high spin phases, 1A/HS and 1C/HS. Further cycling produces the low spin phase 1A/LS. The transition 1A/LS ↔ 1A/HS is accompanied by a 130 K wide hysteresis loop (Tc↑ = 490 K, Tc↓ = 360 K). Annealing the complex 1LS·xH2O at 500 K yields a high spin phase 1C/HS. The phase 1C/HS undergoes spin conversion to the corresponding low spin phase 1C/LS on cooling, T1/2 ≈ 320 K. Dehydration of 1LS·xH2O at 370 or 400 K yields a certain low spin phase, 1X/LS, which irreversibly transforms into a high spin phase 1B/HS, which, in turn, reversibly transforms to the low spin phase 1B/LS on cooling, T1/2 ≈ 320 K.
一个单核复合物 [FeL2](BF4)2·xH2O (1LS·xH2O),其中 L 为 4-(3,5-二甲基-1H-吡唑-1-基)-2-(吡啶-2-基)-6-甲基嘧啶,可以转变为几种不同自旋交叉状态的相。在第一次加热中,1LS·xH2O 失去水分子并转变为两种高自旋相的混合物,1A/HS 和 1C/HS。进一步的循环产生低自旋相 1A/LS。转变 1A/LS ↔ 1A/HS 伴随有一个宽度为 130 K 的滞回环(Tc↑ = 490 K, Tc↓ = 360 K)。在 500 K 下退火复合物 1LS·xH2O 可得到高自旋相 1C/HS。相 1C/HS 在冷却时经历自旋转换,变为相应的低自旋相 1C/LS,T1/2 ≈ 320 K。在 370 或 400 K 下脱水 1LS·xH2O 会得到某种低自旋相 1X/LS,该相不可逆转变为高自旋相 1B/HS,后者在冷却时又可逆转变为低自旋相 1B/LS,T1/2 ≈ 320 K。