Anion-Dependent Assembly of 3d–4f Heterometallic Clusters Ln<sub>5</sub>Cr<sub>2</sub> and Ln<sub>8</sub>Cr<sub>4</sub>
Jia-Jia Yin, Cheng Chen, Gui‐Lin Zhuang, Jun Zheng, Xiu‐Ying Zheng, Xiang‐Jian Kong
Abstract
A series of heterometallic Ln–Cr clusters with the formulas [Ln5Cr2(H2L)2(OAc)6(μ3-OH)6(H2O)15](ClO4)7·xH2O (Ln = Gd and x = 33 for 1 and Ln = Dy and x = 21 for 2) and [Ln8Cr4(H2L)4(OAc)8(μ3-OH)16(μ4-O)1(H2O)8](Cl)(ClO4)5·10H2O (Ln = Gd for 3 and Ln = Dy for 4) was obtained through the reaction of the acetate ligands 2,2-dimethylolpropionic acid (H3L) and Ln(ClO4)3 in the presence of chromium salts with different anions under the same high pH conditions. X-ray analysis revealed that compound 1 contained a metal unit [Gd3Cr2] displaying the pentagonal bipyramid configuration and that compound 3 was templated by Cl– and ClO4– as a mixed anion template featuring a quadrangular structure. In compound 3, the 12 metal atoms were arranged in a wheel-shaped metal skeleton [Gd8Cr4], which was produced by 4 tetrahedral metal units [Gd3Cr] sharing vertices. The introduction of the mixed anion template increased the number of metal atoms in the Ln–Cr clusters. Magnetic calculations indicated that there was weak antiferromagnetic Gd···Cr coupling and weak ferromagnetic Gd···Gd coupling in 1, whereas both Gd···Cr and Gd···Gd in 3 exhibited weak antiferromagnetic interactions. Magnetothermal studies showed that compounds 1 and 3 displayed magnetic entropy changes of 25.2 J kg–1 K–1 at 5 K and 7 T and 33.8 J kg–1 K–1 at 2 K and 7 T, respectively.