Structurally well-defined hetero-pentanuclear manganese-oxide clusters {MMn4} were successfully synthesized in TBA7Hn[MMn4(OH)2(A-α-SiW9O34)2]·2H2O·C2H4Cl2 (, M = Fe(iii), Co(ii), Ni(ii), Cu(ii), Ga(iii)) by sequential introduction of metal cations into the trivacant lacunary polyoxometalates (POMs). The pentanuclear manganese-oxide cluster {Mn5} showed a small spin ground state and a low energy barrier for magnetization relaxation. In contrast, the magnetic interactions in the hetero-pentanuclear clusters could be controlled by the arrangements of metals, and the clusters showed large magnetic anisotropy and single-molecule magnet behavior. In particular, the cluster {FeMn4} in (S = 11/2) showed the slowest relaxation and the highest energy barrier among the previously reported transition metal-containing POMs.