Structural evolution beyond carbon fullerenes: A family of metal-oxo clusters

Fullerenes are a unique class of stable molecular clusters whose structural evolution is constrained by the geometry and topology of pentagon-hexagon arrangements of sp²-hybridized carbons with (p-p)π conjugation. However, extending this geometry- and topology-driven structural evolution to other inorganic systems remains exceedingly rare, because it is highly challenging to achieve controlled assembly of distinct building units and precisely tune their numbers. Here, we report a family of metal-oxo clusters with V₃₀Nb₁₂, V₂₆Nb₈, V₂₄Nb₆, and V₂₂Nb₄ cluster cores. They are constructed from m {(Nb)V₅} pentagons and l {(V)V₄} squares linked through shared vanadium centers. These clusters show a stepwise pentagon decrease (m = 12 → 8 → 6 → 4) and square increase (l = 0 → 2 → 3 → 4) and follow a mathematically defined evolution rule l = 6 - m/2. Quantum-chemical analyses show that, similar to the curved (p-p)π-conjugation characteristic of carbon fullerenes, a spherical multicenter (d-p)π-conjugated network stabilizes these curved {(Nb)V₅} pentagons and {(V)V₄} squares. Together, these findings demonstrate that fullerene-like structural evolution is not restricted to carbon frameworks, but can emerge in metal-oxo clusters through multicenter (d-p)π-conjugation interaction.