Low-valent vanadium(III) with d² electronic configuration, which can generate significant magnetic anisotropy, is highly desirable for the construction of high-performance molecule-based magnetic materials. Such lightweight and flexible magnetic materials cannot be realized by conventional inorganic or alloy-based permanent magnets. However, owing to the facile oxidation of vanadium(III), the synthesis of stable complexes containing highly reduced V(III) or mixed low-valent V(III,IV) centers remains extremely challenging. To date, only a limited number of V(III) or V(III,IV)-based coordination complexes or clusters have been isolated, most of which possess a nuclearity lower than eighteen. Herein, we report the self-assembly of a giant V(III,IV) cluster, namely {V^III₂₀V^IV₂O₈(OH)₈(CH₃COO)₂₄(CH₃CH₂O)₂₀}·5CH₃CH₂OH (V₂₂), from a trinuclear vanadium precursor. The resulting large V₂₂ cyclic coordination cluster exhibits an unusual small triplet ground spin state, which arises from antiferromagnetic exchange interactions. Moreover, this cluster system is detectable by electron paramagnetic resonance (EPR) spectroscopy and displays prominent quantum characteristics.

A family of polyoxo(alkoxo)lanthanide cluster {Ln₁₅} (Ln = Eu (1), Gd (2), Tb (3)) was successfully isolated via a simple hydrolysis reaction of lanthanide metal ions in the presence of tricine ligands. X-ray diffraction analyses revealed that {Ln₁₅} displayed a wheel-like structure with a µ₅-chloride anion as a template. Interestingly, each analog showed distinctive functions based on the different Ln(III) ions. Complexes 1 and 3 in the solid state emitted the characteristic fluorescence of Eu(III) or Tb(III). The fluorescence lifetimes of the ⁵D₀ excited state for 1 and the ⁵D₄ excited state for 3 were tested, and the values were 890 and 250 μs, respectively. Meanwhile, gadolinium analog 2 exhibited a magneto-caloric effect at ultralow temperatures with a maximum −ΔS_m value of 29.9 J·kg⁻¹·K⁻¹ at 3 K and 7 T.