Fixing CO2 from the air to assemble Dy8 zero-field single-molecule magnets and Gd8 magnetocaloric molecular materials
Cai-Ming Liu1,2, Xiang Hao1
1Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory for Organic Solids, Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China. cmliu@iccas.ac.cn.
Abstract:
Assembling Ln(III) clusters by capturing and fixing CO2 from the air is a unique and eco-friendly approach to yielding multinuclear single-molecule magnets and magnetocaloric molecular materials. However, the conditions or factors required to facilitate this process are still unclear. When synthesizing Ln(III) complexes using a hydrazone Schiff base (H2Lschiff) condensed from o-vanillin and 3-aminopyrazine-2-carbohydrazide, LiOH plays a decisive role in the formation of [Dy8(Lschiff)8(CO3)4(H2O)8]·4DMA·4H2O (1) by capturing and fixing CO2 from the air, as using Et3N under the same conditions only yields a normal product, [Dy2(Lschiff)2(DMA)3(H2O)3](CF3SO3)2·3DMA·H2O (2). Either 1 or 2 exhibits intramolecular ferromagnetic interactions, and both perform as good zero-field single-molecule magnets (SMMs). Furthermore, an analog of 1, complex [Gd8(Lschiff)8(CO3)4(H2O)8]·4DMA·4H2O (3), was obtained using a synthesis method similar to that of 1, exhibiting a good magnetocaloric effect. Therefore, choosing the appropriate alkali is a necessary prerequisite for fixing CO2 from the air to assemble polynuclear Ln(III) SMMs and magnetocaloric molecular materials.
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