Stimuli Responsive Hybrid Magnets: Tuning the Photoinduced Spin-Crossover in Fe(III) Complexes Inserted into Layered Magnets

The insertion of a [Fe­(sal2-trien)]+ complex cation into a 2D oxalate network in the presence of different solvents results in a family of hybrid magnets with coexistence of magnetic ordering and photoinduced spin-crossover (LIESST effect) in compounds [FeIII(sal2-trien)]­[MnIICrIII(ox)3]·CHCl3 (1·CHCl3), [FeIII(sal2-trien)]­[MnIICrIII(ox)3]·CHBr3 (1·CHBr3), and [FeIII(sal2-trien)]­[MnIICrIII(ox)3]·CH2Br2 (1·CH2Br2). The three compounds crystallize in a 2D honeycomb anionic layer formed by MnII and CrIII ions linked through oxalate ligands and a layer of [Fe­(sal2-trien)]+ complexes and solvent molecules (CHCl3, CHBr3, or CH2Br2) intercalated between the 2D oxalate network. The magnetic properties and Mössbauer spectroscopy indicate that they undergo long-range ferromagnetic ordering at 5.6 K and a spin crossover of the intercalated [Fe­(sal2-trien)]+ complexes at different temperatures T1/2. The three compounds present a LIESST effect with a relaxation temperature TLIESST inversely proportional to T1/2. The isostructural paramagnetic compound, [FeIII(sal2-trien)]­[ZnIICrIII(ox)3]·CH2Cl2 (2·CH2Cl2) was also prepared. This compound presents a partial spin crossover of the inserted FeIII complex as well as a LIESST effect. Finally, spectroscopic characterization of the FeIII doped compound [Ga0.99Fe0.01(sal2trien)]­[MnIICrIII(ox)3]·CH2Cl2 (3·CH2Cl2) shows a gradual and complete thermal spin crossover and a LIESST effect on the isolated FeIII complexes. This result confirms that cooperativity is not a necessary condition to observe the LIESST effect in an FeIII compound.将[Fe(双水杨醛缩三乙四胺)]+（[Fe(sal2-trien)]+）配合物阳离子嵌入不同溶剂存在下的二维草酸根骨架网络中，得到一系列杂化磁性材料，此类材料在配合物[FeIII(sal2-trien)][MnIICrIII(ox)3]·CHCl3（记为1·CHCl3）、[FeIII(sal2-trien)][MnIICrIII(ox)3]·CHBr3（记为1·CHBr3）以及[FeIII(sal2-trien)][MnIICrIII(ox)3]·CH2Br2（记为1·CH2Br2）中同时存在磁有序与光诱导自旋交叉（photoinduced spin-crossover, LIESST effect）。上述三种配合物均结晶为二维蜂窝状阴离子层结构：该层由MnII与CrIII离子通过草酸根配体桥连形成，同时嵌入于二维草酸根骨架网络之间的还有一层[Fe(sal2-trien)]+配合物与溶剂分子（CHCl3、CHBr3或CH2Br2）。磁性能测试与穆斯堡尔谱学（Mössbauer spectroscopy）表征结果显示，这三种配合物在5.6 K时发生长程铁磁有序，且嵌入的[Fe(sal2-trien)]+配合物会在不同的半转变温度T1/2处发生自旋交叉。三种配合物均表现出LIESST效应，其弛豫温度TLIESST与半转变温度T1/2呈反比关系。本研究还合成了同结构顺磁配合物[FeIII(sal2-trien)][ZnIICrIII(ox)3]·CH2Cl2（记为2·CH2Cl2），该配合物中嵌入的FeIII配合物发生部分自旋交叉，同时也表现出LIESST效应。最后，对FeIII掺杂配合物[Ga0.99Fe0.01(sal2-trien)][MnIICrIII(ox)3]·CH2Cl2（记为3·CH2Cl2）的光谱表征结果显示，孤立的FeIII配合物发生了渐进且完全的热诱导自旋交叉，同时表现出LIESST效应。该结果证实，在FeIII配合物中观测到LIESST效应并不需要协同性的存在。