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Gels, xerogels and films of polynuclear iron(II)-aminotriazole spin-crossover polymeric complexes

机译:多核铁(II)-氨基三唑自旋交联聚合物复合物的凝胶,干凝胶和薄膜

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The prominent polynuclear spin-crossover complex [Fe(NH(2)trz)(3)](2ns)(2) (polymer) (NH(2)trz = 4-amino-1,2,4-triazole, 2ns(-) = 2-naphthalenesulfonate) as obtained from synthesis exists in a metastable state characterized by a columnar hexagonal packing (Col(h)) of polynuclear rigid-rod complexes, and shows considerable fluctuations in the spin-crossover temperature (between 22 and 41 degrees C upon heating and between 14 and 25 degrees C upon cooling). This structure is converted into a more stable columnar rectangular packing (Col(r)) by annealing this material at 250 degrees C, which is accompanied by a shift of the spin-crossover towards higher temperatures (similar to 52 degrees C upon heating and similar to 33 degrees C upon cooling). Furthermore, solutions of [Fe(NH(2)trz)(3)](2ns)(2) in dimethylformamide (DMF) can be converted into gels by increasing the concentration of [Fe(NH(2)trz)(3)](2ns)(2) or by addition of toluene, while preserving the spin-crossover behavior. Gels prepared by the latter method were converted into xerogels by CO2 critical-point drying, or into transparent thermochromic films by slow evaporation of the solvent. For the xerogels an initial Col(h) packing is transformed into the more stable Col(r) packing by the same annealing procedure applied to the powders. On the other hand, the slow evaporation of solvent used for the manufacture of films allowed establishment of a Col(r) packing by annealing at lower temperatures (150 degrees C).
机译:著名的多核自旋交络复合物[Fe(NH(2)trz)(3)] [2ns)(2)(聚合物)(NH(2)trz = 4-氨基-1,2,4-三唑,2ns( -)= 2-萘磺酸盐)合成所得,处于亚稳定状态,其特征是多核刚性棒络合物的柱状六方堆积(Col(h)),并且显示自旋交叉温度存在较大波动(22至41之间)加热时的温度为摄氏14度,冷却时为14至25摄氏度。通过在250摄氏度下对该材料进行退火,可将这种结构转变为更稳定的柱状矩形填料(Col(r)),同时伴随着自旋交叉点向更高温度的移动(加热时类似于52摄氏度,冷却至33摄氏度)。此外,可以通过增加[Fe(NH(2)trz)(3)的浓度将[Fe(NH(2)trz)(3)](2ns)(2)在二甲基甲酰胺(DMF)中的溶液转化为凝胶。 ](2ns)(2)或通过添加甲苯,同时保留自旋交叉行为。通过后一种方法制备的凝胶通过CO2临界点干燥转变为干凝胶,或者通过缓慢蒸发溶剂转变为透明的热致变色薄膜。对于干凝胶,通过对粉末进行相同的退火程序,将初始的Col(h)填充物转化为更稳定的Col(r)填充物。另一方面,用于制造膜的溶剂的缓慢蒸发允许通过在较低温度(150℃)下退火而建立Col(r)填料。

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