Anion and Solvent Manipulated Out-to-In Growth Mechanism to Assemble a Series of Different Dysprosium Clusters

Abstract Although various lanthanide clusters with different shapes and connections have been synthesised, more rules are still needed to guide their further serial expansion and directed structural modification. Herein, we used the multidentate chelating ligand N′2,N′9-bis((E)-2-hydroxy-3-methoxybenzylidene)-1,10-phenanthroline-2,9-dicarbohydrazide (H4L) to react with Dy(NO3)3·6H2O under EtOH/CH3CN conditions to obtain an example of a nonanuclear dysprosium cluster, i.e., [Dy9(L)2(μ2-OH)(μ3-OH)6(NO3)12(H2O)3]·5CH3CN·H2O (1). The structural framework of cluster 1 contains 2 (L)4− ligands, 1 μ2-OH−, 6 μ3-OH−, 12 NO3−, and 3 H2O. Each ligand (L)4− chelates five Dy(III) ions, and its coordination mode is μ5-η1:η2:η1:η2:η1:η1:η2:η1:η2:η1. Cluster 1 has many different connection modes of NO3−, such as μ5-η2:η2:η2, μ2-η1:η1, and μ2-η1:η2. Notably, we only changed the metal salt to Dy(OAc)3·6H2O and obtained an example of a trinuclear dysprosium cluster, i.e., [Dy3(H2L)(OAc)7]·CH3CN·3H2O (2). The structure of cluster 2 contains three Dy(III) ions, one (H2L)2− ion, one μ3-η2:η2-bridged OAc− and six end-coordinated OAc−. The coordination mode of ligand (H2L)2− is μ3-η1:η1:η2:η1:η1:η1:η2:η1. More notably, we only changed the solvent to MeOH/CH3CN, and under the same reaction conditions, we got an example of a dodeca-nucleus dysprosium cluster, i.e., [Dy12(L)4(μ2-OH)2(OAc)14(H2O)8]·4C2H3O2·2H2O (3). In cluster 3, ligand (L)4− adopts the μ5-η1:η2:η1:η2:η1:η1:η2:η1:η2:η1 coordination mode, and the four ligands (L)4− are connected to each other forming the grid structure. Twelve Dy(III) ions are “embedded” in the chelating sites of the ligand and bridged by multiple OAc− ions. A large cavity is formed in the centre of the ‘well’ in cluster 3. The test results of variable temperature AC magnetic susceptibility show that clusters 1–3 all exhibit single-molecule magnet behaviour. To the best of our knowledge, this study is the first to describe that an out-to-in growth mechanism has been manipulated by anions and solvents to realise the synthesis of a series of completely differently connected dysprosium clusters. In addition, this mechanism is also one of the rare examples of anion and solvent co-induced assembly to form lanthanide clusters with completely different shapes and connections.