The controlled assembly of gigantic polyoxometalate (POM) clusters remains one of the most formidable challenges in molecular self-assembly, as it is highly dependent on delicate synthesis parameters that can yield a wide variety of products. In this study, we report the synthesis of a series of unprecedented wheel-shaped molybdenum-blue (MB) clusters directed by organophosphonate (L) and acetate ligands, resulting in a new range of giant MB-type POMs: Mo136Na4, Mo120, Mo118Na2, Mo118, and Mo157. These structures, constructed from fundamental Mo1, Mo2, and Mo8 building blocks, exhibit new features of organic ligand coordination on their exterior surfaces. Notably, the Mo157 framework acts as a host capable of capturing the fully reduced ε-Keggin-based Mo16 guest. It represents the first pure dodecameric Mo wheel reported to date. Systematic variation of reaction parameters─including ligand type, concentration, solvent composition, and precursor identity─enabled precise control over cluster topology, revealing competitive coordination between organophosphonate and acetate ligands. Structural analyses unveiled new connection modes involving reduced edge-sharing e-Mo2 units and their derivative Mo3L2 motifs, which reinforce the overall cage architecture. Mass spectrometry and NMR spectroscopy confirmed the structural integrity of these assemblies in solution. This work not only expands the library of gigantic MB clusters but also establishes a new strategy for their controlled construction using anchored organophosphonate ligands. The resulting clusters exhibit significantly enhanced solubility in organic solvents compared with traditional MB species, offering new opportunities for postsynthetic modification, improved interactions with biomolecules, and diverse applications.
Cheng et al. (2026) studied this question.