Linker Stoichiometry-Controlled Stepwise Supramolecular Growth of a Flexible Cu2Tb Single Molecule Magnet from Monomer to Dimer to One-Dimensional Chain

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• 作者：Soumavo Ghosh ; Yumi Ida ; Takayuki Ishida ; Ashutosh Ghosh
• 刊名：Crystal Growth & Design
• 出版年：2014
• 出版时间：May 7, 2014
• 年：2014
• 卷：14
• 期：5
• 页码：2588-2598
• 全文大小：572K
• 年卷期：v.14,no.5(May 7, 2014)
• ISSN：1528-7505

文摘

A trinuclear complex [(CuL)₂Tb(H₂O)(NO₃)₃]路MeOH路H₂O (1) is synthesized by using a metalloligand [CuL] (H₂L = N,N鈥?bis(salicylidene)-1,3-propanediamine or salpn). This complex is used as a new 3d-4f metallatecton for stepwise supramolecular oligomerization along with a simple diimine linker, 4,4鈥?bipyridine (bpy). A ratio of metallatecton/linker = 2:1 is conducive for the formation of a dimer [{(CuL)₂Tb(H₂O)(NO₃)₃}₂bpy]路2MeOH路4H₂O (2), whereas a higher proportion of linker at a ratio of 1:1 gives rise to a zigzag one-dimensional coordination polymer {[(CuL)₂Tb(NO₃)₃bpy]路MeOH路2H₂O}_{鈭?/sub> (3). The inherent conformational flexibility of the trinuclear (CuL)2Tb node which is folded (cisoid) for 1 and 2 (asymmetric TbO9 tricapped trigonal prism) and unfolded (transoid) for 3 (a C2-symmetric TbO10 tetradecahedron) seems to stabilize the crystal packing of these coordination-driven self-assemblies. The rapidly saturated magnetization at 1.8 K for 1 (11 渭B) and 2 (22 渭B) clearly indicates the presence of Tb鈥揅u ferromagnetic coupling through the phenoxido bridges of the Cu(渭1,1-O)2Tb(渭1,1-O)2Cu cores. A slow saturation behavior has been found for 3 (9.5 渭B). Both in-phase and out-of-phase ac magnetic measurements of 1 under an applied dc magnetic field reveal temperature dependence of the susceptibility at different frequencies below 5 K, characteristic of single molecule magnets (SMMs), which is conserved in 2 and 3 signifying oligo- and polymeric aggregates of SMMs.}