The coordination polymer [Fe(NH2trz)3](2ns)2 (NH2trz = 4-amino-1,2,4-triazole and 2ns− = counterion 2-naphthalene sulfonate) exhibits the rare phenomenon of spin crossover in an attractive temperature range, i.e., somewhat above room temperature. Spin crossover in [Fe(NH2trz)3](2ns)2 is manifested by thermochromism, which is accompanied by a magnetic transition from diamagnetism to paramagnetism. However, [Fe(NH2trz)3](2ns)2 is brittle and difficult to process, which limits its use. In this study, we show that [Fe(NH2trz)3](2ns)2 can be co-processed with ultrahigh molecular weight polyethylene (UHMWPE), which possesses outstanding mechanical properties, particularly when tensile-drawn. Therefore, [Fe(NH2trz)3](2ns)2–UHMWPE blends were gel-processed by extrusion, employing a relatively poor solvent, which has recently been shown to offer advantages compared to good solvents. Uniform and flexible films, ribbons and fibers with [Fe(NH2trz)3](2ns)2 fractions as high as 33.3% m/m were obtained that could be readily drawn. Spin crossover in the coordination polymer is retained in these materials, as evident from their thermochromism. The tensile strength and Young’s modulus of the blends exceed those of typical commodity polymers. Thus, the films, ribbons and fibers constitute a special class of multifunctional materials that combine the flexibility and excellent mechanical properties of drawn UHMWPE with the spin crossover behavior of [Fe(NH2trz)3](2ns)2.

The coordination polymer [Fe(NH2trz)3](2ns)2 exhibits the rare phenomenon of spin crossover in an attractive temperature range, i.e., somewhat above room temperature. Spin crossover in [Fe(NH2trz)3](2ns)2 is manifest by thermochromism, which is accompanied by a magnetic transition from diamagnetism to paramagnetism. However, [Fe(NH2trz)3](2ns)2 is brittle and difficult to process, which limits its use. In this study, we show that [Fe(NH2trz)3](2ns)2 can be co-processed with ultrahigh molecular weight polyethylene (UHMWPE), which possesses outstanding mechanical properties, particularly when tensile drawn. Therefore, [Fe(NH2trz)3](2ns)2–UHMWPE blends were gel-processed by extrusion, employing a relatively poor solvent, which has recently been shown to offer advantages compared to good solvents. Uniform and flexible films, ribbons and fibers with [Fe(NH2trz)3](2ns)2 fractions as high as 33.3% m/m were obtained that could be readily drawn. Spin crossover in the coordination polymer is retained in these materials, as evident from their thermochromism. The tensile strength and Young’s modulus of the blends exceed those of typical commodity polymers. Thus, the films, ribbons and fibers constitute a special class of multifunctional materials that combine the flexibility and excellent mechanical properties of drawn UHMWPE with the spin crossover behavior of [Fe(NH2trz)3](2ns)2.

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Mononuclear coordination compounds of the type [Pd(NH2trz)4]2+ with the counterions chloride, nitrate, trifluoromethanesulfonate, and methanesulfonate were synthesized and their structures identified with single‐crystal X‐ray diffraction. In case of the synthesis with methanesulfonate as the counterion the dominant product was of the generic formula [Pd2(NH2trz)3](CH3SO3)4, and the complex [Pd(NH2trz)4](CH3SO3)2 only emerged as a byproduct. While the structure of the byproduct could be analyzed by single‐crystal X‐ray diffraction, suitable crystals of the main product [Pd2(NH2trz)3](CH3SO3)4 could not be obtained. However, stoichiometry implies a polynuclear nature with NH2trz present in the rare μ3‐η1:η1:η1 coordination type, i.e. with NH2trz molecules coordinating to three palladium atoms. Accordingly, identification of solids by single‐crystal analysis alone can be misleading in particular with NH2trz as a ligand due to its versatile coordination behavior. Finally, analysis by differential scanning calorimetry (DSC) revealed that the complexes were thermally stable (the onset of decomposition well above 100 °C), with [Pd2(NH2trz)3](CH3SO3)4 being the most stable compound (onset of decomposition at 204 °C).