Two Decanuclear DyIIIxCoII10-x (x = 2, 4) Nanoclusters: Structure, Assembly Mechanism, and Magnetic Properties

Anion-Manipulated Hydrolysis Process Assembles of Giant High-Nucleation Lanthanide-Oxo Cluster

Widespread concern has been raised over the synthesis of highly nucleated lanthanide clusters with special shapes and/or specific linkages. Construction of lanthanide clusters with specific shapes and/or linkages can be achieved by carefully regulating the hydrolysis of lanthanide metal ions and the resulting hydrolysis products. However, studies on the manipulation of lanthanide-ion hydrolysis to obtain giant lanthanide-oxo clusters have been few. In this study, we obtained a tetraicosa lanthanide cluster (3) by manipulating the hydrolysis of Dy(III) ions using an anion (OAc^-). As far as we know, cluster 3 has the highest nucleation among all lanthanide-oxo clusters reported. In 3, two triangular Dy₃O₄ are oriented in opposite directions to form the central connecting axis Dy₆(OH)₈, which is in turn connected to six Dy₃O₄ that are oriented in different directions. Meanwhile, a sample of a chiral trinuclear dysprosium cluster (1) was obtained in a mixed CH₃OH and CH₃CN solvent and by replacing the anion in the reaction to Cl^- ions. In this cluster, 1,3,4-thiadiazole-2,5-diamine (L²) is free on one side through π···π interactions and is parallel to the o-vanillin (L¹)^- ligand, thus resulting in a triangular arrangement. The arrangement of L² affects the end group coordination in the cluster 1 structure through hydrogen bonding and induces the cluster to exhibit chirality. When the reaction solvent was changed to CH₃OH, a sample of cluster 2, composed of two independent triangular Dy₃ that have different end group arrangements, was obtained. Magnetic analysis showed that clusters 1 and 3 both exhibit distinctive single-molecule magnetic properties under zero-magnetic-field conditions. This study thus provides a method for the creation of chiral high-nucleation clusters from achiral ligands and potentially paves the way for the synthesis of high-nucleation lanthanide clusters with unique forms.

Alkali metal-linked triangular building blocks assemble a high-nucleation lanthanoid cluster based on single-molecule magnets

The metallic central magnetic axes in high-nucleation clusters with complex structural connections tend to be disorganized and cancel each other out. Therefore, high-nucleation clusters cannot easily exhibit single-molecule magnets (SMMs) behaviors. Herein, we select a triple-core building block (Dy3K2, 1) and use linked diamagnetic alkali metal to form an open, spherical, high-nucleation cluster Dy12Na6 (3) with SMM behavior. Furthermore, by changing the reaction conditions, Dy6K2 (2) formed by linking two Dy3 by K(I) is obtained. High-resolution electrospray mass spectrometry of clusters 1-3 effectively captures the building block Dy3, and clusters 1 and 3 and Dy3 have high stability even with the increase in ion source energy. To the best of our knowledge, this is the first time that an SMM based on a high-nucleation cluster has been obtained by connecting magnetic primitives via diamagnetic metal ions. Dy12K6 is currently the highest nuclear ns-4f heterometallic SMM.

Two Heterometallic Nanoclusters [DyIII4NiII8] and [DyIII10MnIII4MnII2]: Structure, Assembly Mechanism, and Magnetic Properties

A full understanding of the assembly mechanisms of coordination complexes is of great importance for a directional synthesis under control. We thus explored here the formation mechanisms of the two new heterometallic nanoclusters [Dy^III₄Ni^II₈(μ₃-OH)₈(L)₈(OAc)₄(H₂O)₄]·3.25EtOH·4CH₃CN (1) and [Dy^III₁₀Mn^III₄Mn^II₂O₄(OH)₁₂(OAc)₁₆(L)₄(HL)₂(EtOH)₂]·2EtOH·2CH₃CN·2H₂O (2) with different cubane-based squarelike ring structures, which were obtained from the reactions of 4-bromo-2-[(2-hydroxypropylimino)methyl]phenol (H₂L) with Dy(NO)₃·6H₂O and the transition metal salt Ni(OAc)₂·4H₂O or Mn(OAc)₂·4H₂O. The high-resolution electrospray ionization mass spectrometry (HRESI-MS) tests showed that the skeletons of clusters 1 and 2 have a high stability under the measurement conditions for HRESI-MS. The intermediates formed in the reaction courses of clusters 1 and 2 were tracked using time-dependent HRESI-MS, which helped to determine the proposed hierarchical assembly mechanisms for 1 (H₂L → NiL → Ni₂L₂ → Ni₃L₄ → Ni₄L₄ → DyNi₄L₅ → Dy₂Ni₆L₆ → Dy₃Ni₆L₆ → Dy₃Ni₇L₇ → Dy₄Ni₈L₈) and 2 (H₂L → MnL → DyMnL → DyMn₂L → Dy₂Mn₂L_x → Dy₈Mn₂L₂ → Dy₁₀Mn₂L₂ → Dy₁₀Mn₆L_x and H₂L → DyL → Dy₄L₂ → Dy₆L₂ → Dy₈Mn₂L₂ → Dy₁₀Mn₂L₂ → Dy₁₀Mn₆L_x). This is one of the rare examples of investigating the assembly mechanisms of 3d-4f heterometallic clusters. Magnetic studies indicated that the title complexes both show slow magnetic relaxation behaviors and cluster 1 is a field-induced single-molecule magnet.

Anion-Dependent Structure and Luminescence Diversity in ZnII-LnIII Heterometallic Architectures Supported by a Salicylamide-Imine Ligand

To advance the structural development and fully explore the application potential, it is highly desirable but challenging to elucidate the relationship between the structures and properties of Zn^II-Ln^III heterometallic species. Herein, three types of Zn^II-Ln^III heterometallic compounds (Ln^III = Gd^III, Tb^III) formulated as [Zn₁₆Ln₄L₁₂(μ₃-O)₄(NO₃)₁₂]·8CH₃CN (ZnLn-1), [Zn₂Ln₂L₂(NO₃)₆(H₂O)₂]·3CH₃CN (ZnLn-2), and [Zn₄Ln₂L₈(OAc)₁₂]·xCH₃CN (ZnLn-3: for Ln = Gd, x = 5; for Ln = Tb, x = 4) were dictated by common inorganic anions, NO₃^- and OAc^-, with the aid of the multidentate ligand H₂L with propane as the central skeleton and 3-methoxysalicylamide and 3-methoxysalicylaldimine as terminal groups. ZnLn-1 features cubic cages with four {Zn₄L₃} tetrahedral subunits and four Ln³⁺ centers positioned at the eight vertices alternately when NO₃^- was introduced into the reaction system exclusively. An attempt to replace NO₃^- in ZnLn-1 with OAc^- partially led to the formation of {Zn₂Ln₂L₂} heterometallic wheels. Meanwhile, ZnLn-3 featuring double-hairpin-like {Zn₄Ln₂L₄} hemicycles that are orthogonal to each other assisted by intermolecular hydrogen bonds was constructed when NO₃^- in ZnLn-1 was completely replaced by OAc^-. Their structural integrity in solution were ascertained by both emission and ¹H NMR spectroscopy. Ascribed to the different Zn²⁺-containing antenna, ZnTb-2 possesses a relatively strong emission characteristic of Tb³⁺; ZnTb-1 has moderate Tb³⁺ luminescence, yet an absence of Tb³⁺ emission is found in ZnTb-3. Such an emission difference could be mainly attributed to the antenna effect directed by distinct structural characteristics induced by anions. The anion-dictated self-assembly strategy presented herein not only offers a facile approach to regulate the coordination mode of H₂L to such an extent to obtain diverse structures of Zn^II-Ln^III heterometallic species but also provides an understanding of how common inorganic anions tune coordination-driven self-assemblies as well as the subsequent luminescence properties.

Structure, assembly mechanism and magnetic properties of heterometallic dodecanuclear nanoclusters DyIII4MII8 (M = Ni, Co)

Two isostructural heterometallic dodecanuclear nanoclusters [Dy4Co8(μ3-OH)8(L)8(OAc)4(H2O)4]·3EtOH·3CH3CN·H2O (1) and [Dy4Ni8(μ3-OH)8(L)8(OAc)4(H2O)4]·3.5EtOH·0.5CH3CN·5H2O (2) with different assembly mechanisms are presented here.