Two new heterometallic coordination polymers, [Na(4)Ln(12)(stp)(8)(OH)(16)(H2O)(12)] (H2O)-H-10 [Ln = Dy (1) and Ho-2], have been prepared from monosodium 2-sulfoterephthalate (NaH(2)stp), dysprosium acetate, or holmium acetate. They are isostructural, possessing a [Ln(12)(mu(3)-OH)(16)](20+) wheel-cluster core based on four vertex-sharing cubane-like [Ln(4)(mu(3)-OH)(4)](8+) units. The Ln(12) cores are linked by stp ligands into a three-dimensional (3D) architecture. Magnetic studies indicate that complex 1 exhibits slow relaxation of magnetization, and it can be regarded as the first 3D coordination assembly of a Dy12 cluster single-molecule magnet.