Here we report the synthesis, structure and detailed characterisation of three n-membered oxovanadium rings, Nan[(V=O)nNan(H2O)n(α, β, or γ-CD)2]⋅mH2O (n = 6, 7, or 8), prepared by the reactions of (V=O)SO4⋅xH2O with α, β, or γ-cyclodextrins(CDs) and NaOH in water. Their alternating heterometallic vanadium/sodium cyclic core structures were sandwiched between two CD moieties such that O-Na-O groups separated neighbouring vanadyl ions. Antiferromagnetic interactions between the S = ½ vanadyl ions led to S = 0 ground states for the even-membered rings, but to two quasi-degenerate S = ½ states for the spin-frustrated heptanuclear cluster
