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Synthesis and Characterisation of a New Series of Bistable Iron(II) Spin-Crossover 2D Metal–Organic Frameworks

机译:一系列新的双稳态双稳铁(II)自旋交联二维金属-有机骨架的合成与表征

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摘要

Twelve coordination poly-mers with formula {Fe(3-Xpy)_2-[M~(II)(CN)_4]}(M~(II):Ni,Pd, Pt; X: F, Cl,Br, I; py: pyridine) have been synthes-ised, and their crystal structures havebeen determined by single-crystal orpowder X-ray analysis. All of thefluoro and iodo compounds, as well asthe chloro derivative in which M~(II)is Pt,crystallise in the monoclinic C2/mspace group, whereas the rest of thechloro and all of the bromo derivativescrystallise in the orthorhombic Pnc2space group. In. all cases, the iron(II)atom resides in a pseudo-octahedral[FeN_6] coordination core, with similarbond lengths and angles in the various derivatives. The major difference be-tween the two kinds of structure arisesfrom the stacking of consecutive two-dimensional {Fe(3-Xpy)_2[M~(II)(CN)_4]}∞layers, which allows different disposi-tions of the X atoms. The fluoro andchloro derivatives undergo cooperativespin crossover (SCO) with significanthysteretic behaviour, whereas the restare paramagnetic. The thermal hystere-sis, if X is F, shifts toward room tem-perature without changing the coopera-tivity as the pressure increases in theinterval 10~5Pa-0.5 GPa. At ambientpressure, the SCO phenomenon hasbeen structurally characterised at dif-ferent significant temperatures, and thecorresponding thermodynamic parame-ters were obtained from DSC calori-metric measurements. Compound {Fe-(3-Clpy)_2[Pd(CN)_4]}represents a newexample of a "re-entrant" two-stepspin transition by showing the Pnmaspace group in the intermediate phase(IP) and the Pnc2 space group in thelow-spin (LS) and high-spin (HS)phases.
机译:式{Fe(3-Xpy)_2- [M〜(II)(CN)_4]}(M〜(II):Ni,Pd,Pt; X:F,Cl,Br,I ; py:吡啶)已经合成,并且它们的晶体结构已经通过单晶或粉末X射线分析确定。所有的氟和碘化合物,以及其中M〜(II)是Pt的氯代衍生物,在单斜C2 / mspace组中结晶,而其余的氯代和所有溴代衍生物在正交Pnc2space组中结晶。在。在所有情况下,铁(II)原子都位于伪八面体[FeN_6]配位核中,在各种导数中键长和角度相似。两种结构之间的主要区别来自于连续二维{Fe(3-Xpy)_2 [M〜(II)(CN)_4]}∞层的堆叠,从而可以实现X个原子。氟和氯衍生物经历具有显着滞后行为的合作旋转(SCO),而其余部分是顺磁性的。如果X为F,则热滞现象会随着压力在10〜5Pa-0.5 GPa间隔内的增加而朝着室温方向移动而不改变合作性。在环境压力下,SCO现象已在不同的显着温度下进行了结构表征,并且通过DSC量热测量获得了相应的热力学参数。化合物{Fe-(3-Clpy)_2 [Pd(CN)_4]}表示中间相(IP)中的Pnmaspace组和其中的Pnc2空间组,代表了一个“重入”两步自旋转变的新示例。低自旋(LS)和高自旋(HS)相。

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