Local Coordination and Electronic Structure Ramifications of Guest-Dependent Spin Crossover in a Metal–Organic Framework: A Combined X-ray Absorption and Emission Spectroscopy Study
Local Coordination and Electronic Structure Ramifications of Guest-Dependent Spin Crossover in a Metal–Organic Framework: A Combined X-ray Absorption and Emission Spectroscopy Study
复制标题
金属有机框架中客体相关自旋交叉的局域配位和电子结构后果：X 射线吸收和发射光谱联合研究
DOI：
10.1021/acs.inorgchem.2c00774
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发表时间：
2022
影响因子：
4.6
通讯作者：
Lockard, Jenny V.
中科院分区：
文献类型：
--
作者：
Solovyev, Mikhail;Kucheryavy, Pavel;Lockard, Jenny V.
多孔霍夫曼型三维晶格Fe(pz)[NiII(CN)4]表现出热诱导自旋交叉（SCO）行为，该行为取决于占据孔隙的溶剂客体。本文采用原位Fe - K-edge x射线吸收光谱（XAS）和非共振和共振k - β x射线发射光谱（XES）方法，在两种产生不同极端自旋交叉温度的溶剂环境下（乙腈和甲苯）对该框架进行了探测。当乙腈孔环境在室温下产生SCO响应时，甲苯客体稳定了高自旋状态，并在整个环境温度范围内有效抑制SCO行为。多管齐下的x射线光谱方法同时证实了这种自旋交叉行为，并提供了这两种溶剂环境下框架的局部配位和电子结构的新见解。扩展x射线吸收精细结构分析揭示了自旋态和溶剂客体相关的配位键长度和结构紊乱的差异。共振光谱测量产生了具有明显前边缘和边缘特征的高分辨率XAS光谱，该光谱的分配是通过简单的配体场理论和随时间变化的密度泛函理论计算建立的，并得到了它们在二维rx平面上观察到的共振行为的进一步支持。边缘特征随Fe自旋态的变化被解释为揭示特定金属连接器键共价的变化。
The porous Hoffman-type 3D lattice Fe(pz)[NiII(CN)4] exhibits thermally induced spin-crossover (SCO) behavior that is dependent on the solvent guest species occupying the pores. Here, in situ Fe K-edge X-ray absorption spectroscopy (XAS) and both non-resonant and resonant Kβ X-ray emission spectroscopy (XES) methods are used to probe this framework under two solvent environments that yield different extremes of spin crossover temperature: acetonitrile and toluene. While the acetonitrile pore environment engenders an SCO response around room temperature, toluene guests stabilize the high spin state and effectively suppress SCO behavior throughout the ambient temperature range. The multipronged X-ray spectroscopy approach simultaneously confirmed this spin crossover behavior and provided new local coordination and electronic structural insights of the framework under these two solvent environments. Extended X-ray absorption fine structure analysis revealed spin state and solvent guest-dependent differences in coordination bond lengths and structural disorder. Resonant XES measurements produced high-resolution XAS spectra with distinct pre-edge and edge features, whose assignment was established using both simple ligand field theory and time-dependent density-functional theory calculations and further supported by their observed resonance behavior in the 2D RXES plane. Edge feature variation with the Fe spin state was interpreted to reveal changes in specific metal-linker bond covalency.