A series of dysprosium clusters assembled by a substitution effect-driven out-to-in growth mechanism

Abstract

Although the design and synthesis of high-nuclear lanthanide clusters with specific shapes and functions have been an active area of research, effective experience and rules to guide further systematic expansion of lanthanide clusters with different connections are lacking. Herein, we adjusted the steric hindrance effects on the substituents of diacylhydrazone ligands (H₄L¹, N′²,N′⁹-bis((E)-2-hydroxybenzylidene)-1,10-phenanthroline-2,9-dicarbohydrazide; H₄L², N′²,N′⁹-bis((E)-2-hydroxy-3-methylbenzylidene)-1,10-phenanthroline-2,9-dicarbohydrazide; H₄L³, N′²,N′⁹-bis((E)-3-(tert-butyl)-2-hydroxybenzylidene)-1,10-phenanthroline-2,9-dicarbohydrazide) and reacted them with Dy(NO₃)₃·6H₂O under solvothermal conditions to obtain three dysprosium clusters (1–3) with different shapes. The molecular formulas of the abovementioned clusters are [Dy₁₆(L¹)₃(μ₃-OH)₂₅(NO₃)₁₁(H₂O)₁₀]·4CH₃CN·8CH₃OH, [Dy₁₀(L²)₄(μ₂-OH)₂(μ₃-O)₄(NO₃)₄(CH₃CN)₂(CH₃OH)₄(H₂O)₈]·CH₃OH·8H₂O, and [Dy₅(L³)₂(μ₂-CH₃O)(μ₂-OH)₂(μ₄-O)(NO₃)₂(CH₃OH)₂]·6CH₃OH·2CH₃CN. Cluster 1 with a brucite-like planar structure crystallizes in the P2₁/n space group of the monoclinic system. The Dy(III) ions in the cluster 1 structure are bridged by μ₃-OH⁻ to form a plane triangle shape. In addition, the structure of cluster 1 contains three layers of Dy(III) ions (1 + 6 + 9) with different coordination environments. Cluster 2 crystallizes in the P space group of the triclinic system. The cluster core in cluster 2 is composed of two molecules of missing cubane Dy₄O₆ and two Dy(III) ions. The ligand (L²)⁴⁻ adopts two coordination modes (μ₃-η¹:η¹:η²:η¹:η¹:η²:η¹:η¹ and μ₅-η²:η¹:η¹:η¹:η¹:η¹:η¹:η¹:η¹:η²) to chelate Dy(III) ions. In addition, Dy(III) ions in Dy₄O₆ are connected by μ₂-OH⁻ and μ₃-OH⁻. Two molecules of planar Dy₃L³ intersect to form cluster 3, and it crystallizes in the I2/a space group of the monoclinic system. The analysis of the structure of clusters 1–3 shows that they are formed by a stepwise assembly process from outside to inside. To the best of our knowledge, a very small number of examples have reported that a series of differently connected dysprosium clusters were obtained through the regulation of substitution effects. Notably, we are the first to propose the out-to-in growth mechanism of planar high-nucleus dysprosium clusters. The results of the variable temperature AC susceptibility test show that clusters 1, 2, and 3 exhibit single-molecule magnet-like behavior under zero-field conditions.