Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.
J Am Chem Soc. 2020 Mar 11;142(10):4842-4851. doi: 10.1021/jacs.9b13835. Epub 2020 Feb 26.
Spin crossover complexes are known to undergo bond length, volume, and enthalpy changes during spin transition. In an explosive spin crossover complex, these changes could affect the mechanical and initiation sensitivity of the explosive and lead to the development of a new class of sensitivity switchable materials. To explore this relationship, the well-known spin crossover compound [Fe(Htrz)][ClO] () was re-evaluated for its explosive properties, and its mechanical impact sensitivity was correlated to spin transition. A variable temperature impact test was developed and used to evaluate the impact sensitivity of in the low spin (LS, S = 0), thermally accessed high spin (HS, S = 2), and mixed LS and HS states. For comparison, the structurally similar Ni compound, [Ni(Htrz)][ClO] (), which does not undergo a spin transition at accessible temperatures, was synthesized and characterized, and its explosive properties and variable temperature impact sensitivity measured. These results reveal a correlation between impact sensitivity and spin transition, where exhibits lower impact sensitivity in the LS state and increases in sensitivity upon transition to the HS state. Density functional theory was used to predict structural changes that occur upon spin transition that correlate to the change in sensitivity. This demonstrates, for the first time, an explosive spin crossover compound (ExSCO) that exhibits switchable impact sensitivity with a fully reversible internal switching mechanism.
自旋交叉配合物在自旋转变过程中通常会经历键长、体积和焓的变化。在爆炸型自旋交叉配合物中，这些变化可能会影响爆炸物的机械和引发敏感性，并导致新型敏感性可切换材料的发展。为了探索这种关系，重新评估了著名的自旋交叉化合物[Fe(Htrz)][ClO]（）的爆炸性能，并将其机械撞击敏感性与自旋转变相关联。开发了一个变温撞击测试，用于评估[Fe(Htrz)][ClO]（）在低自旋（LS，S=0）、热访问的高自旋（HS，S=2）和混合 LS 和 HS 状态下的撞击敏感性。为了进行比较，合成并表征了结构相似的 Ni 化合物[Ni(Htrz)][ClO]（），该化合物在可访问的温度下不会发生自旋转变，并测量了其爆炸性能和变温撞击敏感性。这些结果表明撞击敏感性与自旋转变之间存在相关性，其中[Fe(Htrz)][ClO]（）在 LS 状态下表现出较低的撞击敏感性，而在向 HS 状态转变时敏感性增加。密度泛函理论用于预测自旋转变时发生的结构变化，这些变化与敏感性的变化相关。这首次证明了具有完全可逆内部切换机制的可切换冲击敏感性的爆炸型自旋交叉配合物（ExSCO）。
