Aimed at exploring new organically derivatized POMs, three heterocyclic hydrazides functionalized hexamolybdates (TBA)₃[Mo₆O₁₈(=N=NCOC₅H₄N)] (1) (TBA = tetrabutylammonium), (TBA)₃[Mo₆O₁₈(=N=NCOC₄H₃S)] (2) and (TBA)₃[Mo₆O₁₈(=N=NCOC₄H₃N₂)] (3) were prepared via the reflux reaction of corresponding heterocyclic hydrazides and octamolybdates in the dry acetonitrile. Their structures were determined by single crystal X-ray diffraction, all compounds can be viewed as one terminal oxo atom of hexamolybdates being substituted by corresponding heterocyclic hydrazides via the Mo=N multiple bond. There are three conformational isomers of [Mo₆O₁₈(=N=NCOC₅H₄N)]^3- with the approximate symmetry of C_s or C₁ in the asymmetric unit of compound 1, but only one anion cluster of [Mo₆O₁₈(=N=NCOC₄H₃S)]^3- with the approximate symmetry of C_s in the asymmetric unit of compound 2. Their structures are further evidenced by FT-IR, UV-Vis, ESI MS, ¹H NMR spectroscopy and so on. Antitubercular activity tests manifest that all compounds demonstrate enhanced inhibitory activities compared to that of hexamolybdates and L2, but it still inferior to L1 and L3. Considering their large molecular weight, their molar inhibitory activity is close or superior to the ligands of L1 and L3. Our current work provides a promising way to develop POMs with biological activities through the molecular hybridization of organic medicines and POMs via covalent bond.

A series of polyoxometalate-based cyclophanes (polyoxometalatocyclophanes) were synthesized via covalent linkage of Lindqvist-type hexamolybdate clusters with bis-arylimido ligands bearing flexible alkyl chains. Single-crystal X-ray diffraction and circular dichroism spectroscopy confirm that compound 3, ((n-C₄H₉)N)₂[Mo₆O₁₇N(o-phenyl-O(CH₂)₅O-phenyl-o)N], undergoes spontaneous chiral resolution upon crystallization. Biological evaluation against the leukemia K562 cell line shows that, among the tested compounds, including aromatic amine ligands, hexamolybdate salts, and related polyoxometalatocyclophanes, compound 3 exhibits the highest inhibitory activity. At higher concentrations, its activity surpasses that of the positive control, 5-fluorouracil (5-FU). Molecular docking and molecular dynamics simulations indicate that the [Mo₆O₁₇N(o-phenyl-O(CH₂)₅O-phenyl-o)N]²⁻ anion adopts a compact conformation and can effectively bind to the anti-apoptotic protein Bcl-2, with a predicted binding affinity of −27.39 kcal/mol.

Two monosubstituted organoimido hexamolybdates containing isoquinoline or quinoline were successfully synthesized. Through the coordination driving of silver(I) ions, the obtained organoimido-derivatized hexamolybdates can assemble with β-octamolybdate in a controlled manner to form nanorod-like triads. Unlike the isolated polyoxometalates before assembly, nanosized polyoxometalate assemblies can exhibit interesting fluorescence activities.

Using chain-like polyethers consisting of two terminal –NH₂ groups and (TBA)₄[α-Mo₈O₂₆] as starting materials, two polyoxometalatocrown ethers were prepared by a cyclization reaction through the formation of Mo≡N triple bonds: (TBA)₂[Mo₆O₁₇N(o-C₆H₄OCH₂(CH₂OCH₂)_nCH₂OC₆H₄-o)N] (compounds 1, n = 1; 2, n = 2). As confirmed by single-crystal X-ray diffraction and infrared (IR) studies, the polyoxometalatocrown ether 2 can capture primary ammonium cations in solid state.

In this study, we present a comprehensive overview of supramolecular self-assemblies comprising cyclodextrins (CDs) and polyoxometalates (POMs). We summarize the recent advancements in supramolecular POM–CD systems, including their structures, functions, and applications. Subsequently, we focus on the self-assembly behavior of CDs and POMs, encompassing the formation of inclusion complexes, host–guest interactions, and the development of hybrid materials. In addition, we discuss the remarks on future outlooks and hope that this review will serve as a valuable reference for researchers engaged in the fields of supramolecular/POM chemistry, materials science, and nanotechnology.