羧酸配体取代基对席夫碱型双核镝(Ⅲ)配合物结构和磁性的影响

Replacement of Carboxylate Ligand Substituent on Modulation of Structures and Magnetic Properties in Salen⁃Type Dinuclear Dy(Ⅲ) Complexes

以N-(2-羟基-3-甲氧基亚苄基)氨基脲(H2hms)与不同取代基的羧酸(RCOOH)为配体,合成了3例席夫碱类的中心对称双核镝基配合物[Dy_(2)(Hhms)_(2)(C(CH_(3))_(3)COO)_(2)(H_(2)O)_(4)](NO_(3))_(2)(1)、[Dy_(2)(Hhms)_(2)(C_(14)H_(9)COO)_(2)(C_(2)H_(5)OH)_(2)(CH_(3)OH)_(2)][ZnCl_(4)](2)和[Dy_(2)(Hhms)_(2)(C_(6)H_(3)(NH_(2))_(2)COO)_(2)Cl_(2)]·2CH_(3)CN(3),并对其进行了结构和磁性表征。结构分析表明,配合物1和2保持了相似的单帽四方反棱柱配位构型,但1与2中羧酸与Dy(Ⅲ)键合的方式不同;配合物2和3保持了相似的酚氧和羧酸桥联结构,但由于配位小分子的不同,配合物3中Dy(Ⅲ)离子的配位几何构型与2有所不同。磁性测试结果表明,配合物3在零场下观察到显著的单分子磁体行为,具有磁翻转有效能垒96 K。相反,配合物1仅表现了快的量子隧穿弛豫行为,甚至配合物2没有单分子磁体的弛豫信号。借助结构特点和各向异性轴取向等关键信息,对3例配合物的磁构效关系进行了讨论。研究结果表明利用羧酸配体取代基能够实现对分子磁各向异性以及对称性的良好调控,从而提高镧系单分子磁体磁弛豫行为。

Three salen⁃type centrosymmetric dinuclear Dy(Ⅲ)complexes,[Dy_(2)(Hhms)_(2)(C(CH_(3))_(3)COO)_(2)(H_(2)O)_(4)](NO_(3))_(2)(1),[Dy_(2)(Hhms)_(2)(C_(14)H_(9)COO)_(2)(C_(2)H_(5)OH)_(2)(CH_(3)OH)_(2)][ZnCl_(4)](2),and [Dy_(2)(Hhms)_(2)(C_(6)H_(3)(NH_(2))_(2)COO)_(2)Cl_(2)]·2CH_(3)CN(3)(H_(2)hms=(2⁃hydroxy⁃3⁃methoxybenzylidene)⁃semicarbazide),were isolated with different substituted carboxylic acid ligand,and were characterized structurally and magnetically.Structural analyses illustrate that the Dy(Ⅲ)ions in complexes 1 and 2 maintain similar monocapped square⁃antiprism geometries,but the coordination mode of carbox⁃ylate in 1 is different from that in 2;complexes 2 and 3 possess similar phenoxy oxygen and carboxylate bridged structure whereas the coordination geometries around the Dy(Ⅲ)ions are different between 3 and 2 due to the differ⁃ence of coordinated small molecules.Magnetic characterizations reveal that significant single⁃molecule magnet(SMM)behavior was observed under zero dc field for complex 3,with an effective energy barrier to the reversal of magnetization of 96 K.Conversely,complex 1 only showed fast quantum tunneling relaxation even 2 was SMM⁃silent.Furthermore,the magneto⁃structural correlations in these Dy_(2) complexes were discussed.The results indicate that utility of carboxylate ligand substituent can give rise to good modulation in the molecular anisotropy and symme⁃try,hence the enhanced magnetic relaxation.CCDC:2092500,1;2092502,2;2092503,3.