To explore new organically derivatized polyoxymetalates (POMs), three heterocyclic hydrazide-functionalized hexamolybdates—1: (TBA)₃[Mo₆O₁₈(=N=NCOC₅H₄N)], 2: (TBA)₃[Mo₆O₁₈(=N=NCOC₄H₃S)], and 3: (TBA)₃[Mo₆O₁₈(=N=NCOC₄H₃N₂)]; (TBA = tetrabutylammonium)—were synthesized by refluxing the corresponding heterocyclic hydrazides with octamolybdates in dry acetonitrile. Their structures were elucidated by single-crystal X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet–visible spectrscopy, electrospray ionization mass spectrometry, and ¹H nuclear magnetic resonance spectroscopy. In all compounds, one terminal oxo atom of the hexamolybdate is replaced by a heterocyclic hydrazide via a Mo=N multiple bond. Compound 1 contains three conformational isomers of [Mo₆O₁₈(=N=NCOC₅H₄N)]³⁻ with approximate C_s or C₁ symmetry, whereas compound 2 contains a single [Mo₆O₁₈(=N=NCOC₄H₃S)]³⁻ anion with C_s approximate symmetry. Antitubercular activity assays show that all three compounds exhibit enhanced inhibitory activity compared with hexamolybdate and the thiophene-2-carbohydrazide (L2) ligand, although their activity remains lower than that of isoniazid(L1) and pyrazine-2-carbohydrazide (L3). Given their large molecular weights, the molar inhibitory activities of compounds 1–3 are close to or superior to the corresponding ligands alone. Overall, this work demonstrates that molecular hybridization of organic drug molecules with POMs via covalent bonds provides a promising strategy for developing POM-based agents with enhanced biological activity.

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.