American Chemical Society
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Single-Crystal to Single-Crystal Transformation of a Spin-Crossover Hybrid Perovskite via Thermal-Induced Cyanide Linkage Isomerization

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journal contribution
posted on 2022-06-09, 14:33 authored by Wei-Wei Wu, Kai-Ping Xie, Guo-Zhang Huang, Ze-Yu Ruan, Yan-Cong Chen, Si-Guo Wu, Zhao-Ping Ni, Ming-Liang Tong
Linkage isomers involving changes in the bonding mode of ambidentate ligands have potential applications in data storage, molecular machines, and motors. However, the observation of the cyanide-linkage-isomerism-induced spin change (CLIISC) effect characterized by single-crystal X-ray diffraction remains a considerable challenge. Meanwhile, the high-spin and low-spin states can be reversibly switched in spin-crossover (SCO) compounds, which provide the potential for applications to data storage, switches, and sensors. Here, a new perovskite-type SCO framework (PPN)­[Fe­{Ag­(CN)2}3] (PPN+ = bis­(trisphenylphosphine)­iminium cation) is synthesized, which displays the unprecedented aging and temperature dependences of hysteretic multistep SCO behaviors near room temperature. Moreover, the thermal-induced cyanide linkage isomerization from FeII–NC–AgI to FeII–CN–AgI is revealed by single-crystal X-ray diffraction, Raman, and Mössbauer spectra, which is associated with a transition from the mixed spin state to the low-spin state and a dramatic volume shrinkage. Considering the wide use of cyanogen in magnetic systems, the association of CLIISC and SCO opens a new dimension to modulate the spin state and realize a colossal negative thermal expansion.