Polyoxovanadium glycolates (NH4)3[V6O6(glyc)6V(μ-OH)6]·10H2O (1-V7) (H2glyc = glycolic acid) and its derivatives added with ammonium sulfates (NH4)3[V6O6(glyc)6M(μ-OH)6][(NH4)2SO4]2·xH2O (M = Cr, x = 6, 2-CrV6; M = Fe, x = 7, 3-FeV6; M = Al, x = 6, 4-AlV6) were obtained through self-assembly and fully characterized. Compounds 1-4 are composed of the same fully reduced cyclic {VIV6O6} unit bridged by six glycolate ligands. The framework encapsulated an octahedral metal(III) hydroxide {M(OH)6} (M = V3+, Cr3+, Fe3+, and Al3+) in the center, forming an iso- or hetero-heptanuclear Anderson-type structure. Moreover, two sulfate anions capped the two sides of cyclic {V6O6} units in compounds 2-4. Each sulfate formed a strong triple hydrogen bond (2.657-2.829 Å) with the μ3-OH group of the hydroxide. The sulfate anions played important roles in the formation of layered structures in 2-4, while the clusters were stacked compactly through strong hydrogen bonds in 1-V7. Because of the different central metals, these heptanuclear clusters exhibited distinct electronic structures as well as redox and magnetic properties. Magnetic studies showed that compounds 1-3 exhibited weak antiferromagnetic interactions in decreasing order with Fe3+, V3+ and Cr3+, while 4-AlV6 displayed weak ferromagnetic interactions. Their relationships with the local environment of the FeV-cofactor in V-nitrogenase are also discussed.