Yan Zhang,Jing Fan,Lingzhi Chen,Na Liu,Hongmei Geng
Two new tetranuclear cluster-based compounds, namely [Cd 2 (L1)(H 2 O)(DMA)] n ( 1 ) and [Cd 2 Ba 2 (L2)(H 2 O) 6 (DMA)] n ( 2 ) [H 4 L1 = 3-(3',5'-dicarboxylphenoxy) phthalic acid, H 4 L2 = 6-(3',4'-dicarboxyl-phenoxy) isophthalic acid, DMA = N,N' -dimethylacetamide], were successfully synthesized under solvothermal conditions and structurally characterized by single-crystal X-ray diffraction analyses. Compound 1 features a two-dimensional (2D) layered framework with tetranuclear [Cd 4 (COO) 6 ] clusters as building subunits, and can be simplified into a binodal (3, 6)-connected kgd topological network with the schläfli symbol of {4 3 } 2 {4 6 ;6 6 ;8 3 }, and compound 2 features a three-dimensional (3D) complicated framework based on heterometallic tetranulear [Cd 2 Ba 2 (COO) 8 ] cluster subunits, and can be simplified into a binodal (3, 6)-connected topological network. In addition, compounds 1 and 2 not only have high thermal stabilities but also show strong luminescent emissions at room temperature.
A series of tetranuclear lanthanide-based clusters [Ln4(dbm)6(L)2(CH3OH)4]·2CH3OH (Ln(III) = Gd (1), Dy (2), and Ho (3); H3L = 2-[(2-(hydroxyimino)propanehydrazide)methyl]-2,3-dihydroxybenzaldehyde, Hdbm = dibenzoylmethane) and octanuclear lanthanide-based clusters [Ln8(HL)10(CH3O)4(CH3OH)2]·6CH3OH (Ln(III) = Gd (4), Dy (5)) were assembled using a polydentate Schiff-base ligand H3L and two different β-diketone salts via a solvothermal method, and their structures and magnetic properties have been characterized. Interestingly, β-diketones play an important role in assembling and affecting the structures of Ln4 to Ln8 clusters. This is the first use of β-diketone to affect the structures of polynuclear Ln(III)-based clusters from linear-shaped Ln4 clusters to Ln8 clusters. Magnetic studies revealed that antiferromagnetic interactions exist in clusters 1-Gd4 and 4-Gd8. More importantly, clusters 1-Gd4 and 4-Gd8 display significant cryogenic magnetic refrigeration properties (−ΔSm = 24.88 J kg−1 K−1 for 1-Gd4 and −ΔSm = 32.52 J kg−1 K−1 for 4-Gd8); the results show that cluster 4-Gd8 exhibits a larger magnetocaloric effect than 1-Gd4. Cluster 2-Dy4 shows remarkable single-molecule magnet (SMM) behavior (ΔE/kB = 67.5 K and τ0 = 3.06 × 10−7 s) under a zero dc field, and 5-Dy8 exhibits a field-induced SMM-like behavior (ΔE/kB = 39.83 K and τ0 = 2.12 × 10−7 s) under a 5000 Oe dc field.
Yan Li,Deyun Ma,Chanchan Chen,Minchun Chen,Zhanhong Li,Yetao Wu,Shanshan Zhu,Guo Peng
A hydrostable and bromine-functionalized MOF with a sxd topology constructed from tetranuclear clusters, {[Mn 2 (Bript) 2 (4,4'-bpy) .5 (DMF)]·(H 2 O)} n ( 1 ) (H 2 Bript = 4-Bromoisophthalic acid, 4,4'-bpy = 4,4'-bipyridine, DMF = dimethylformamide) was synthesized and structurally characterized. TGA and PXRD results show high thermal and water stability for the framework. 1 displays a 3D framework with the channel of 4.6 × 4.6 Å 2 along the c axis. The framework exhibits a reversible and highly selective luminescent sensing function with respect to Hg 2+ cation. Magnetic measurements reveal that the presence of weak antiferromagnetic couplings between the four Mn(II) ions in 1 .
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