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The complex hydrolysis process and strong uncertainty of self-assembly rules have led to the precise synthesis of lanthanide clusters still being in the "blind-box" stage and simplifying the self-assembly process and developing reliable regulation strategies have attracted widespread attention. Herein, different anions are used to induce the construction of a series of dysprosium clusters with different shapes and connections. When the selected anion is NO3−, it blocks the coordination of metal sites around the cluster through the terminal group coordination mode, thereby controlling the growth of the cluster. When NO3− was changed to OAc−, OAc− adopted a bridging mode to induce modular units to build dysprosium clusters through an annular growth mechanism. Specifically, we selected 2-amino-6-methoxybenzoic acid, 2-hydroxybenzaldehyde, and Dy(NO3)3·6H2O to react under solvothermal conditions to obtain a pentanuclear dysprosium cluster (1). The five Dy(III) ions in 1 are distributed in upper and lower planes and are formed by the tight connection of nitrogen and oxygen atoms, and μ3-OH− bridges on the ligand. Next, octa-nuclear dysprosium cluster (2) were obtained by only regulating ligand substituents. The eight Dy(III) ions in 2 are tightly connected through ligand oxygen atoms, μ2-OH−, and μ3-OH− bridges, forming an elliptical {Dy/O} cluster core. Furthermore, only by changing NO3− to OAc−, a wheel-shaped tetradeca-nuclear dysprosium cluster (3) was obtained. Cluster 3 is composed of OAc− bridged multiple template Dy3L3 units and pulling of these template units connected by an annular growth mechanism forms a wheel-shaped cluster. The angle of the coordination site on NO3− is ∠ONO = 115°, which leads to the further extension of the metal sites on the periphery of clusters 1 and 2 through the terminal group coordination mode, thereby regulating the structural connection of the clusters. However, the angle of the coordination site on OAc− is ∠OCO = 128°, and a slightly increased angle leads to the formation of a ring-shaped cluster 3 by connecting the template units through bridging. This is a rare example of the controllable construction of lanthanide clusters with different shapes induced by the regulation of different anions, which provides a new method for the precise construction of lanthanide clusters with special shapes. [ABSTRACT FROM AUTHOR]

Although progress has been made in the design and synthesis of chiral lanthanide clusters with pleasing structural connections and special shapes, assembly rules that guide their directional construction are still lacking. We reacted R/S -mandelic acid hydrazide, 2,3-dihydroxybenzaldehyde and DyCl3·6H2O under solvothermal conditions to obtain two octanuclear chirality clusters R-1 and S-1 , which are the enantiomers of each other. R/S -mandelic acid hydrazide and 2,3-dihydroxybenzaldehyde underwent an in situ reaction under "one-pot" conditions to generate a monohydrazone-type organic ligand R/S -mandelic acid hydrazide-2,3-dihydroxybenzaldehyde hydrazone (R/S -H2L). Four R/S -H2L ligands captured eight metal-centered Dy(III) ions and presented an annular arrangement, which assembled to form a pinwheel-shaped chiral cluster R/S-1. The benzene rings at the four vertices of R/S-1 can rotate freely as rotors. This is the first discovery of an annular growth mechanism during the self-assembly of lanthanide clusters. By changing the metal salt to Dy(NO3)3·6H2O, two twist-shaped hexanuclear clusters R-2 and S-2 , which are the enantiomers of each other were obtained. Four R/S -H2L and two R/S -H3L ligands captured six metal-centered Dy(III) ions, respectively, and were assembled through a linear growth mechanism to form the twist-shaped chiral clusters R/S-2. This is the first time that a linear growth mechanism has been proposed for the directional construction of lanthanide clusters with specific shapes. Circular dichroism results showed that R/S-1 and R/S-2 were both chiral clusters and enantiomers of each other. Magnetic studies showed that both R/S-1 and R/S-2 exhibit obvious single-molecule magnet (SMM) behaviors under zero-field conditions. This work is the first to propose an annular/linear growth mechanism for the design and synthesis of lanthanide clusters and allows the directional construction of chiral lanthanide clusters with special shapes and structural connections. [ABSTRACT FROM AUTHOR]

The most effective way to understand reaction mechanisms and kinetics is to identify the reaction intermediates and determine the possible reaction patterns. The influencing factors that must be considered in the self-assembly of clusters are the type of ligand, metal ion, coordination anion and the pH of the solution. However, changes in ligand substituents resulting in different self-assembly processes to obtain different types of structures are still very rare, especially with –H and –CH3 substituents, which do not exert significant steric hindrance effects. In this study, planar mononuclear Ni(L1)2 (L1 = 2-ethoxy-6-(iminomethyl)phenol) was dissolved in methanol and combined with Dy(NO3)3·6H2O for 48 h at room temperature to obtain a butterfly-like Ni2Dy2 cluster ([Dy2Ni2(L1)4(CH3O)2(NO3)4], 1). The Dy(III) ions in cluster 1 are in an O8N coordination environment, and the Ni(II) ions are in an O5N coordination environment. High-resolution electrospray ionization mass spectrometry (HRESI-MS) was used to track species changes during the formation of cluster 1. Six key intermediate fragments were screened, and the self-assembly mechanism was proposed as Ni(L1)2 → HL1 + NiL1 → DyL1/Ni(L1)2′ → DyNi(L1)2 → Dy2Ni2(L1)4. Through this assembly mechanism, we found that Ni(L1)2 was first cleaved into HL1 + NiL1 and then further assembled to obtain 1. Another butterfly-like tetranuclear heterometallic cluster ([Dy2Ni2(L2)4(CH3O)2(NO3)4], 2) was obtained using planar mononuclear Ni(L2)2 (L2 = (E)-2-ethoxy-6-((methylimino)methyl)phenol) with –CH3 substitution on the nitrogen atom under the same reaction conditions. The structural analysis of cluster 2 showed that the Dy(III) ions are in an O9 coordination environment, and the Ni(II) ions are in an O4N2 coordination environment. HRESI-MS was used to trace species changes during the formation of 2, and the assembly mechanism was proposed as Ni(L2)2 → DyNi(L2)2 → Dy2Ni(L2)2 → Dy2Ni2(L2)4. Analysis of the assembly mechanism of 2 showed that Ni(L2)2 was twisted during the reaction, and its coordination point was exposed to capture the Dy(III) ions. Finally, Dy(NO3)3·6H2O was replaced with NaN3 to obtain a [Ni2Na2(L2)4(N3)4] cluster (3) under the same reaction conditions and verify the above-mentioned torsion step. HRESI-MS was also used to trace the assembly process, and the assembly mechanism was proposed as Ni(L2)2 → NiNa(L2)2 → NiNa2(L2)2 → Ni2Na2(L2)4. Herein, the effect of interference from substitution and the regulation self-assembly process were discovered in the formation of 3d–4f heterometallic clusters, and different types of coordination clusters were obtained. [ABSTRACT FROM AUTHOR]