A Multiferroic Spin-Crossover Molecular Crystal.
basic_science · Level V
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- Record sourced from PubMed, PMID 39104291.
- Also identified by DOI 10.1002/adma.202407822.
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Abstract
Spin-crossover (SCO) ferroelectrics with dual-function switches have attracted great attention for significant magnetoelectric application prospects. However, the multiferroic crystals with SCO features have rarely been reported. Herein, a molecular multiferroic Fe(II) crystalline complex [Fe<sup>II</sup>(C<sub>8</sub>-F-pbh)<sub>2</sub>] (1-F, C<sub>8</sub>-F-pbh = (1Z,N'E)-3-F-4-(octyloxy)-N'-(pyridin-2-ylmethylene)-benzo-hydrazonate) showing the coexistence of ferroelectricity, ferroelasticity, and SCO behavior is presented for the first time. By H/F substitution, the low phase transition temperature (270 K) of the non-fluorinated parent compound is significantly increased to 318 K in 1-F, which exhibits a spatial symmetry breaking 222F2 type ferroelectric phase transition with clear room-temperature ferroelectricity. Besides, 1-F also displays a spin transition between high- and low-spin states, accompanied by the d-orbital breaking within the t<sub>2g</sub> <sup>4</sup>e<sub>g</sub> <sup>2</sup> and t<sub>2g</sub> <sup>6</sup>e<sub>g</sub>° configuration change of octahedrally coordinated Fe<sup>II</sup> center. Moreover, the 222F2 type ferroelectric phase transition is also a ferroelastic one, verified by the ferroelectric domains reversal and the evolution of ferroelastic domains. To the knowledge, 1-F is the first multiferroic SCO molecular crystal. This unprecedented finding sheds light on the exploration of molecular multistability materials for future smart devices.