Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22607, Hamburg, Germany.
Departments of Chemistry and Physics, University of Toronto, 80 St. George Street, Toronto, M5S 3H6, Canada.
Angew Chem Int Ed Engl. 2017 Jun 12;56(25):7130-7134. doi: 10.1002/anie.201702497. Epub 2017 May 16.
Photoexcitation of spin crossover (SCO) complexes can trigger extensive electronic spin transitions and transformation of molecular structure. However, the precise nature of the associated ultrafast structural dynamics remains elusive, especially in the solid state. Here, we studied a single-crystal SCO material with femtosecond electron diffraction (FED). The unique capability of FED allows us to directly probe atomic motions and to track ultrafast structural changes within a crystal lattice. By monitoring the time-dependent changes of the Bragg reflections, we observed the formation of a photoinduced structure similar to the thermally induced high-spin state. The data and refinement calculations indicate the global structural reorganization within 2.3 ps, as the metal-ligand bond distribution narrows during intramolecular vibrational energy redistribution (IVR) driving the intermolecular rearrangement. Three independent dynamical group are identified to model the structural dynamics upon photoinduced SCO.
光激发自旋交叉（SCO）配合物可以引发广泛的电子自旋转变和分子结构的转变。然而，相关的超快结构动力学的精确性质仍然难以捉摸，特别是在固态下。在这里，我们使用飞秒电子衍射（FED）研究了一种单晶 SCO 材料。FED 的独特能力允许我们直接探测原子运动，并在晶格内跟踪超快结构变化。通过监测布拉格反射的时变，我们观察到形成了类似于热诱导高自旋态的光诱导结构。数据和精修计算表明，在 2.3 ps 内发生了整体结构重排，因为在分子内振动能量再分配（IVR）驱动分子间重排期间，金属-配体键分布变窄。确定了三个独立的动力学组来模拟光诱导 SCO 后的结构动力学。
